Thesis
Upcoming SlideShare
Loading in...5
×
 

Thesis

on

  • 12,736 views

 

Statistics

Views

Total Views
12,736
Views on SlideShare
12,736
Embed Views
0

Actions

Likes
0
Downloads
11
Comments
0

0 Embeds 0

No embeds

Accessibility

Categories

Upload Details

Uploaded via as Microsoft Word

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

Thesis Thesis Document Transcript

  • MATERIALS AND METHODS CHAPTER 3: MATERIALS AND METHODS The upland watershed spread over Chittagong and Chittagong Hill Tracts in Bangladesh was green with the presence of natural forests. Area affected by deforestation in Bangladesh is either not surveyed or mapped and areas never determined except periodic ocular observations. The different estimates of deforestation reported in various sources are not mutually consistent (FMP, 1992). In 1927 Bangladesh had 20% natural forest and at present 6% of its forestland is covered with natural trees. The annual rate of deforestation in Bangladesh is very high (3.3%) compared to other six South Asian countries (0.6%) during 1981-1990, the rate again increasing over the decades. The estimated deforestation of about 8,000 hayr -1 during the 1970s, increased to about 37,600 hayr-1in the 1980s (FMP, 1992). In the hill forest including USF tree cover area is 54% of the land managed by Forest Department. The period between mid-1960 and mid-1980s Cox’s Bazar region lost 36% and Chittagong region 58% tree cover. In other words, within this 20 years time denudation took place to 18,800 ha out of 52,800 ha in Cox’s Bazar, while to 57,500 ha out of 99,300 ha in Chittagong forest area. Deforestation also occurred in all the Reserved Forests in CHTs, but the extent varies from forest to forest (FMP, 1992). Of the major Reserved Forests in the CHTs Rankhiang was the worst affected forest. During the period from 1963 and 1983, the extent of non forested area at Kassalong Reserved Forest increased from 3 to 32%, at Sangu and Matamuhuri Reserved Forests from 0.5 to 23% and, at Rankhiang Reserved Forest from 3 to 49% (FMP, 1992). Deforestation increased at Kassalong Reserved Forest due to encroachment by destitute jhumias displaced by plain land settlers and also because of illegal logging. Within the Rangamati district, deforestation in the protected forest was caused by organized gangs. Development activities such as dam, highway, road construction and other infrastructure development also increased deforestation rate. Along with specific causes, generalized reasons for deforestation in hilly region including Chittagong and Cox’s Bazar district are policy weakness, inappropriate and over exploitation of forests, law and order failures and increased habitations. Deforestation process involves cutting and lopping of trees, excessive grazing, illicit felling, fuel wood collection, burning, uncontrolled and wasteful Institute of Forestry and Environmental Sciences Page 22
  • MATERIALS AND METHODS felling, conversion of forest to agriculture through clearing and burning, migration of landless people in the forest areas and encroachment. The study included 12 deforested locations spread over in Chittagong region and 7 clear felled area Chittagong district (North); and 14 shifting cultivated area in CHTs. Each of the sites with activities are described bellow: 3.1 DEFORESTED AREA: 3.1.1 DULAHAZARA: Dulhazara is an important forest belt of natural Dipterocarpus spp. (garjan) in Chittagong-Cox’s Bazar region. The natural garjan forest with an area of 900 ha at Dulhazara declared as Safari Park in 1996 (Choudhury et. al., 2004). The Dulhazara Safari Park is under the administration of Wildlife Management and Nature Conservation Division, Chittagong. The park lies between 20043´N to 21056´N latitudes and between 91050´E to 92023´ E longitudes beside Chittagong-Cox’s Bazar road. Topography of the park is almost flat and little undulating with a slope of 0 to 4%. Natural forests: Natural forest of Dulhazara Safari Park is characterized by the presence of dominant species such as Dipterocarpus spp. (garjan), Syzygium spp. (jam) and 2 types of canes and shrub species like Clerodendrum indicum, Mussaenda roseburghii, Melastoma malabatricwn etc. on gentle slope and several natural and artificially created lakes for wildlife water supply. About 92% trees in the forest were garjan, 7% jam and remaining of other tree species. Tree canopy coverage of the forest ranged from 10% to 50% and undergrowth coverage varied from 40% to 100% over the whole area of the forest. Undergrowth composed of herbs, shrubs, climbers, bamboos and canes along with remarkable amount of litter on the forest floor. Proportion of dominant garjan trees falling in 21m – 40 m height class possessed 23%, in 10 m -20 m height class 33% and in <10 m height class 44% and planted garjan trees mostly occupied this class. For creating ecotourism facility, 12 km road network present inside the Safari Park. Natural forest within the Safari Park falls under the tropical evergreen and semi-evergreen forest bio-geographic zone (Khan, 1990). However, like other natural forests, vegetation of the Dulahaza Safari Park was also variable in composition, coverage and height growth in different parts of the natural forests. Therefore, soil profiles were studied and soils Institute of Forestry and Environmental Sciences Page 23
  • MATERIALS AND METHODS collected from each horizon representing all variations of vegetation in the natural forest of Dulahazara, as described below. Old deer breeding area: This part of natural forest was in old deer breeding area on high land at 9 m elevation having gentle slope ranging from 0% to 4%. This forest site lies at 21o40΄09΄΄N latitude and 092o05΄18΄΄E longitude. In this natural forest, vegetation was the mixture of Dipterocarpus spp. (garjan), Syzygium grande (dhaki jam), Mangifera indica (aam) and Macaranga peltata (meda) with their proportion of 68, 17, 10 and 5, respectively. Tree canopy coverage of the forest was 40% and undergrowth coverage varied from 70% having no grass vegetation, but 96% land covered with litter. At this area bamboo clump covered 80% land during vegetation survey in 2007 and Dipterocarpus spp. (garjan) and Aquilaria agallocha (agar) together covered 20% land. All bamboo clumps were found to disappear in September 2012 during final visit to this forest area due to natural succession of the vegetation. Mean diameter of garjan trees in this part of the natural forest ranged from 60.50 cm to 66.25 cm and mean height from 21.70 m to 27.50 m. Mean height of S. grande ranged from 16.50 m to 25 m in this part of the forest. The number of trees varied from 125 to 200 with mean of 167 stems per hectare. Litter cover was almost uniform over the forest of depth 7.6 cm and weight 6490 kgha-1. Cimmamomum spp. (tejbahal) rarely present as undergrowth. At this site soil profile comprised of A1, A2, B1 and C horizon and soil texture up to B1 horizon i.e. up to 76 cm depth, was sandy clay loam and in the C horizon of 76 cm to 96 cm+ contained sandy clay texture. West of Birds Avery: This part of natural garjan forest was to the west of Birds Avery on high land at 9 m elevation having a gentle slope ranging from 0 to 4%. This forest site lies at 21o40΄10΄΄N latitude and 092o05΄02΄΄E longitude. In this part of natural forest, vegetation was the mixture of bamboo, bet and others. Tree canopy coverage in the forest was 30% and undergrowth coverage 90% having no grass vegetation with litter coverage of 70-96%. Bamboo constituted 80% during vegetation survey in 2007, and cane and other species 20% as undergrowth. Similar to above described area bamboo was absent at this part of the forest also in September 2012. The mean diameter of garjan trees ranged from 46.5 cm to 66.0 cm and mean height varied from 23.83 m to 24.5 m with tree Institute of Forestry and Environmental Sciences Page 24
  • MATERIALS AND METHODS densities ranging from 100 to 225 and mean of 168 numbers ha -1. The height and diameter of S. grande (dhaki jam) were 16 m and 60 cm and of Alstonia scholaris (chatim) 10 m and 6 cm, respectively. Litter cover was almost uniform over the forest of depth 3.67 cm and weight 5323 kgha-1. Asian and African Herbivores Animal Enclosure: This part of natural garjan forest was in Asian and African Herbivores Animal Enclosure on high land at 10 m elevation having a gentle slope ranging from 0 to 4%. This forest site lies at 21o40΄11N latitude and 092o05΄30E longitude. This site within the natural forest was fully covered by planted garjan trees. Three strata from lower to upward in the garjan plantation were 5 m, 8 m and >10 m height. Tree canopy coverage of the forest was 70% and undergrowth coverage 50% having no grass vegetation and 90% land covered with litter. Garjan constituted 80% as tree cover and Melastoma malabathricum (bon tezpata) and other herbs and shrubs constituted 20% as undergrowth. In the forest, mean diameter of garjan trees ranged from 9.81 cm to 12.95 cm and mean height varied from 8.15 m to 8.53 m with tree densities between 3100 and 3700 with mean of 3400 stems ha -1. Litter cover was almost uniform over the forest of depth 7 cm and weight 4607 kgha-1. North east of Lion Enclosure: This forest part was to the north east of Lion Enclosure on high land at 10 m in elevation having a gentle slope ranging from 0 to 2%. This forest site lies at 21o40΄24΄΄N latitude and 092o05΄17΄΄E. This natural forest area was fully covered by garjan tree. Tree canopy coverage of the forest was 50% and undergrowth coverage varied from 40-70% having no grass vegetation and 80% land covered with litter. Syzygium grande (dhaki jam) constituted 60% as tree and others such as Cimmamomum spp. (tejbahal) and cane as undergrowth constituted 40%. In the forest, mean diameter of garjan trees ranged from 52.5 cm to 58.22 cm and mean height varied from 17.25 m to 17.72 m with tree densities ranging from 200 to 400 and mean of 275 stems ha-1. Two S. grande trees were also found at this forest part. The mean diameter and height of S. grande were 49.5 cm and 14.5 m, respectively. Litter cover was almost uniform over the forest of depth 4.5 cm and weight 6297 kgha-1. West of observation tower: This natural garjan forest area was to the west of high observation tower and above branched lake on high land at 8 m elevation having gentle Institute of Forestry and Environmental Sciences Page 25
  • MATERIALS AND METHODS slope ranging from 0 to 4%. This forest part lies at 21 o39΄52΄΄N latitude and 092o05΄38΄΄E. This forest area covered with garjan trees. Tree canopy coverage of the forest was 10% and undergrowth coverage 100% having no grass vegetation and fully (100%) covered with bamboo clump. Similar to other parts of the forest bamboo clumps were found to disappear from this forest part also during final field visit in 2012. Syzygium grande (dhaki jam) constituted 60% and other vegetation such as Cimmamomum spp. (tejbahal), cane constituted 40% as undergrowth. In the forest, mean diameter of garjan trees ranged from 18.50 cm to 45.50 cm and mean height varied from 13 m to 17.5 m with tree density 200 numbers ha-1. Deforested land: The deforested land possessed in the past similar ecological characteristics as exists in natural forest vegetation of Dulhazara Safari Park. In the near past, the whole area of Dulahazara was covered with dense evergreen forest dominated by tall trees such as Anisoptera glebra (boilam), Dipterocarpus spp. (garjan), Artocarpus chaplasha (chapalish), Hopea odorata (telsur) etc. Then diversity and density of the plant species was very high with the presence many wild animals such as Royal Bengal tiger, Chitabag, elephant, deer (Choudhury et. al., 2004). Survey done on February 2007 showed that the land comprised of small sized scattered distribution of Hollarrhena antidycenterica (kuruz), Dipterocarpus turbinatus (telia garjan), Emblica officinalis (amoloki), Cimmamomum spp. (tejbahal), Ficus benghalensis (bot) and Syzygium fruticosum (puti jam) with herbs and shrubs of 1-2.5 m height giving coverage of 3040%. Only about 24 garjan trees of 10 m – 20 m height class and only 3 trees > 20 m height class on about 800 ha deforested land. No litter coverage was found on the floor due to complete burning in places. The land was disturbed through collection of forest products such as fuel-wood, small sized construction timber, grasses and other products by people residing inside and around the forest and clearing of forest areas in some places for the cultivation of seasonal agriculture crops. Deforested land is thus unprotected. The deforested land 1 was on low hill top at10 m elevation of gentle slope ranging from 0 to 4% to the 3 km north-east of Dulhazara Safari natural Park. This site was at geographical position of 21o40΄08N and 092o04΄53E and possessed similar ecological characteristics except the vegetation. The deforested land with slope of 2-10% contained Institute of Forestry and Environmental Sciences Page 26
  • MATERIALS AND METHODS no trees and vegetation consisting of herbs and shrubs of height 1.0 m – 2.5 m with coverage of 30-40% and litter coverage 30%. During survey on February 2007, the land was barren and burnt for agricultural practice, but about 30 years before this area possessed Dipeterocarpus spp. (garjan) forest, as informed from local people and similar to existing Safari natural Park, and now fully destroyed due to illicit felling. Litter depth of this site was 1 cm and weight 400 kgha-1. The deforested land 2 with slope of 0 to 4% contained no trees and vegetation consisting of herbs and shrubs of height 1-2.5 m having coverage of 30-40%. This site was at geographical position of 21o39΄55N and 092o05΄50N having no litter coverage because of complete burning and ashes present on surface soil. The deforested land 3 was at geographical position of 21o39΄58N and 092o05΄50E on 0 to 4%, land contained no trees and vegetation consisting of herbs and shrubs of height 1.0 m – 2.5m having coverage of 70%. Litter coverage was 60% with depth of 2.33 cm and weight 1440 kg ha-1. 3.1.2 Tonkawati Tonkawati forest is situated in the transition zone of Bandarban Hill District and Chittagong District. This forest covers Tankawati Beat under Padua Range of Chittagong South Forest Division and Tankawati Range of Bandarban Forest Division. This forest lies between 21057´8´´N and 2209´13´´N latitudes and between 9207´32´´E and 92012´22´´E longitudes. Tankawati forest covers five moujas, of which four in Chittagong district and one in Banderban district. The four moujas under Lohagara Upazilla of Chittagong district are Paharchada, Maijbilla, Rajghata and Charamba. Tankawati is the name of Mouja as well as Range in Bandarban Sadar Upazilla of Bandarban district. Natural forest: Tankawati natural forest covered 1741 ha land, of which 810 ha to 1012 ha compact high reserved forest. The forest was characterized by the presence of dominant species such as Dipterocarpus turbinatus (garjan) and Artocarpus chaplasha (chapalish) to the top storey and Pterospermum acerifolium (mose) as middle storey and Meloanna baccifera (muli) clump present as undergrowth. Tree canopy coverage of the forest ranged from 10% to 70% and undergrowth coverage varied from 40% to 100%. Institute of Forestry and Environmental Sciences Page 27
  • MATERIALS AND METHODS Tree size varied greatly in this natural forest. Mean height of the dominant species was 30 m with close canopy coverage. Litter cover was almost uniform over the forest with depth of 10 cm giving mean litter weight 5500 kgha-1. Natural forest 1: This was a good natural D. spp. (garjan) forest on northern aspect at 21°58′702″N and 092°11′745″E geographic position having large and well crown coverage and completely covered with litter on a medium high hill having 12% slope. This part of forest comprised of 60-70% trees and 30-40% other vegetation. This part of forest was mostly occupied by Dipterocarpus turbinatus, (telya garjan - 100 stems ha-1), Dipterocarpus gracilis (dhulia garjan- 75 stems ha-1) and other tree species included A. chaplasha (chapalish), Tetrameles nudiflora (chandul), Quercus spp. (batna) etc. giving 70% tree canopy coverage. Combining all tree species in this part of forest had 375 stems ha-1. Forest floor was fully covered with 8 cm thick litter giving accumulation rate 4620 kg ha-1. From ocular observation this part of forest was found free from soil erosion. Natural forest 2: This part of natural forest on northern aspect was on 15% slope, where 13 tree species recorded. Among these, dominant tree species were tellya garjan (100 stem ha-1) followed by Dipterocarpus gracilis (dhulia garjan), Illex godajam (godajam) (75 stem ha-1), Castanopsis indica (batna), A. chaplasha (chapalish), Brownlowia elata (moch) (50 stem ha-1). All other tree species in this part of forest had 25 stems ha-1. Combining all, 313 trees ha-1 was existed in the forest. The maximum dbh were found at this part for Dipterocarpus turbinatus (teliya garjan) D. gracilis (dhulia garjan) and B. elata (moch). Here, top storey coverage was 90%, middle storey 60%, and ground storey coverage 60% with no grass vegetation. Forest is of 3 storied, being upper story 26-30 m, middle 12-15 m and lower one 5-7 m. Both depth and litter fall accumulation were variable within the forest. Litter depth varied from 2 to 7 cm with accumulation of 40804600 kg ha-1 with mean of 4280 kg ha-1 and depth of 4.83 cm. The northern aspect of this forest also contained natural bamboo as under growth of D. spp. (garjan) trees. From ocular observation this site was found free from soil erosion. Tankawati natural forests were rich in natural regeneration and distribution of different trees quite good. The regeneration of Dipterocarpus spp., Swintonia floribunda and Artocarpus chaplasha are satisfactory by area, number and age class in different portions of the forest. Institute of Forestry and Environmental Sciences Page 28
  • MATERIALS AND METHODS Deforested land: The natural forest consisted of Dipterocarpus turbinatus (garjan), Artocarpus chaplasha (chapalish) with several other tree species on low hill, although a major portion has been deforested due to illicit felling. Topography of the land is moderately steep on western aspect. Soil profile was dug on a patch of barren/deforested land at lower part on 20% hill slope on western aspect. On both sides of the deforested land were natural forest and the site lied in between agricultural land on valley and natural forest. In this area, very few under growth were present, 80% land grass covered and litter almost nil. 3.1.3 Chunti Wildlife Sanctuary: Chunuti Wildlife Sanctuary is under Chunuti Forest Range of Chittagong South Forest Division. The sanctuary is located at 22008'N latitude and 91058' to 92005'E longitude, about 70 km south of Chittagong City and to the west side of Chittagong-Cox’s Bazar highway (WCMC, 1998 and Khan, 1990). This sanctuary covered a total area of 7764 ha of reserved forest (Rahman, et. al., 2000). There were 8 forest Beats in Chunuti Wildlife Sanctuary (Rahman, et. a.l., 2000) and the study area located at Chunuti Beat. Administratively, the land is situated at Aziz Nagar Union under Lohagara Upzila in Chittagong district. Each pair of land consisted of a Wildlife Sanctuary land and a deforested land situated side by side on similar topographic position. The sanctuary area is generally hilly to mountainous with shallow to deep gullies with gentle to steep slopes. Surface soils on the alluvial plain and valley are mainly silt loam to silt clay loam, moderately to strongly structured with neutral to medium acid subsoil (Rahman, et. al., 2000). First pair of land: 25 year old deforested land: The Chunuti wildlife sanctuary was established in 1986. Deforestation and encroachment has already destroyed a major portion of this sanctuary during the last decades (Rahaman, et al., 2000). The rate of deforestation was severe after the liberation war of Bangladesh. The distance of this deforested land from the Arakan Road is about 300 m and lies at an elevation of 25 m. According to the record of Chunuti Forest Range, this land was completely deforested in the beginning of 1980 and thus, the age of this deforestation land became 25 years. Institute of Forestry and Environmental Sciences Page 29
  • MATERIALS AND METHODS Wildlife sanctuary land1: The adjacent compared forest land in the sanctuary was 200 m apart from the deforested land. Once the sanctuary was composed of about 477 plant species of evergreen and semi-evergreen trees, shrubs, and herbs, but during the study species composition and condition much changed compared to the past time. In this sanctuary, only 20% species constituted natural and the remaining 80% planted species by the Forest Department in 1978. The dominant tree species of this land was Dipterocarpus turbinatus (telya garjan). Second pair of land: 27 year old deforested land: The deforested land was 500 m apart and to the west of the first deforested land. The topography of this land was also hilly and lied at an elevation of 20 m. The distance from the adjacent wildlife sanctuary land was 180 m and to the east of the first deforested land. According to record of Chunuti Forest Range, the site was deforested at the beginning of 1978 and therefore, deforestation age of this land was 27 years. Wildlife sanctuary land 2: On this land, only 20% species was natural and 80% species artificially planted by Forest Department in 1977. The land was hilly with an elevation of 30 m. The dominant species of this land was Dipterocarpus turbinatus (teya garjan). 3.1.4 Batali hill The area was planted with Acacia auriculiformis in 1997 under the financial and supervision by the Chittagong City Corporation. Only northern side of the hill was planted leaving the southern, eastern, and western side barren. The top of the hill was also not planted. The spacing was 2 m X 2 m in acacia mono-plantation. The growth of the trees was better. Most of the trees already reached to a height of 12 m to 15 m and diameter at breast height (dbh) between 12 cm and 18 cm. The height and diameter increment were more vigorous in valley than that of mid slope and upper slope. The encroacher built house on valley and top of the hill illegally without permission from the proper authority. The settlers mainly came from Noakhali, Comilla, Feni and Barisal districts. Hill cutting was recorded in the area by the encroacher for making houses. Institute of Forestry and Environmental Sciences Page 30
  • MATERIALS AND METHODS 3.1.5 Hazarikhil This study area was at Hazarikhil Forest Range in Chittagong North Forest Division for determination of effects of deforestation. This Forest Range is situated 45 km north of Chittagong city and administratively at Harualchari Union under Fatickchari Upazilla in Chittagong district. The area possesses sub-tropical climate with a long dry season extending from October to May. Total forest area of this Forest Range was 4255 ha, with legal status of reserve forest. Sampling sites both in deforested and natural forest covered an area of 4 ha in two Forest Blocks, namely, Hazarikhil and Rangapani, lying between 22040′N and 22043′ N latitudes and between 90039.5′E and 91042′ E longitudes. About 50 years back, Hazarikhil area was rich in forest. The forest consisted of a mixture of many tropical evergreen and deciduous species occurring in association with each other and with bamboo jungle. Most of the area is now deforested with the presence of hardly a few valuable forest species (SRDI, 2002). With the objective to select representative study sites, a preliminary survey was done first in Hazarikhil natural forest and its surrounding deforested area under Fatickchari Upazilla. The survey also included identifying respondents and rapport building with the local leader and interactive association with Hazarikhil Forest Range office to collect factual information related to natural forest and deforested land. For selection of study sites, personal contact was made with office of Chittagong North Forest Division and base map collected from the office. To get more information about Hazarikhil Natural forest, land acquisition records were searched in the office of Fatickchari Upazilla. No record was found on deforested area of Fatickchari Upazilla, contact therefore, made with Hazarikhil Range Office and local people, particularly old aged persons, to find out the age of deforested lands. Map was consulted in detailed with Forest Range Officer of Hazarikhil Range. He and his office staff helped to locate all the study sites in the field. Thus, 5 sites from Hazarikhil natural forest and 5 sites from deforested area were selected for collection of data on various aspects related to the study. Thus, selected five deforested sites were of 15, 23, 33, 38, and 43 years old. Sampling points in the natural forest and deforested land were at least 50 m inside from the boundary to avoid interaction between the two land use types. Natural forest consisted of a mixture of Institute of Forestry and Environmental Sciences Page 31
  • MATERIALS AND METHODS different species in association with bamboo jungle having 97% vegetation coverage. In deforested land coverage was 20%, each for trees, shrubs and herbs. At Hazarikhil soil sampling was done from 0-5 cm and 5-15 cm depth digging mini profiles. Hazarikhil was under Chittagong North Forest Division. This location contained 5 pair sites representing natural forest and deforested land. The deforested sites were of 15, 23, 33, 38, and 43 years old. Sampling points in the natural forest and deforested land were at least 50 m inside from the boundary to avoid interaction between the two land use types. 3.1.6 Mandakini To determine effect of deforestation this study was conducted at Mandakini Forest Beat, Hathazari Forest Range in Chittagong North Forest Division. Two sites, one in plantation at Mandakini Forest Beat and the other in adjacent deforested area, were selected for the study. Sampling area both on deforested land and plantation of this Forest Beat covered 25 ha. Mean monthly temperature of this area varied from 19.8ºC in January to 28.6ºC in May with mean annual temperature is 25.6ºC and mean annual rainfall of 2914 mm (SRDI, 1991). Plantation: This was a 9 year mixed plantation of Acacia auriculiformis (akashmoni) and Acacia mangium (mangium) with 70% canopy coverage situated on the southern side of Mandakini Forest Beat office on land with 15% slope. Undergrowth covered area was not uniform over the whole plantation. Undergrowth in this plantation consisted of Mimosa pudica (lajjabati), Caealpinia cristael (kootumkanta), Hyptic sauveolens (tokma), Eupatorium odoratum (assamlata) etc. with a number of vines and creepers. Deforested land: In deforested land had no tree and undergrowth consisted of Mimusa pudica (Lajjabati), Caealpinia cristael (Kootumkanta), Eupatorium odoratum (Assamlata), Mikania cordata (Tarakanta) etc. At Mandakini soil sampling was done from 0-10 cm and 10-30 cm depth both from plantation and deforested land. Degraded natural forest: This site was in degraded natural forest of Sitapahar at 49 m elevation of a flat hill top on north-western aspect with adjacent very steep hill slope at Institute of Forestry and Environmental Sciences Page 32
  • MATERIALS AND METHODS Rampahar Forest Beat, Kaptai Forest Range, Rangamati South Forest Division with geographical position 22o29΄41N and 092o10΄20E. Vegetation consisted of few valuable species like, Dipterocarpus spp. (garjan), Castanopsis tribuloides (lal batna) and Swintonia floribunda (civit) with admixture of herbs, shrubs and important climber, Entada phaseoloids (gilalata). Top storey canopy coverage of the forest was 30%, undergrowth coverage 100% and ground vegetation coverage 18% in the forest. Forest floor was uniformly fully (100%) covered with 11 cm thick litter layer giving mean weight 1093 kg ha-1. However, forest contained good regeneration of tree species like Syzygium grandis (jam), Mangifera longipes (uriam), Alastonia scholaris (chatim), D. spp. (garjan), Lannea coromandelica (bhadi), Mucuna prurens (bandarhula) etc. Different sized 12 tree species in 2 plots of diameter ranged between 6 cm and 55 cm and between 3 m and 30 m with 225 stems ha -1in this degraded natural forest. Tree species in the forest consisted of Pothos scandens (hatilata), M. longipes (uriam), Schima wallichii (konak), L. coromandelica (bhadi), Diospyros peregrina (gab), D. spp. (garjan), A. scholaris (chatim), S. grandis (jam) and Castanopsis indica (batna). 3.1.7 Jahajpura Jahazpura is one of the oldest garjan sample plot of more than 200 years covering an area of 700 m to 1300 m wide and 2 km long strip on almost flat land with 2% slope on northwestern aspect at 4 m elevation above MSL situated between sea and hills at Shilkhali Forest Beat and Range, under Cox’s Bazar South Forest Division. According to personal communication to Cox’s Bazar South Forest Division Office in September 2012 it was known that Garjan Sample Plot covers 30 ha land and total land area under Shilkhali Forest Beat covered 303.56 ha. This forest is about 10 km away from Teknaf lying at 21o1΄429΄΄N latitude and 92o11΄253΄΄E longitude. In this forest tree density was more in the middle part and density decreased both in northern and southern part. From a complete enumeration in Shilkhali garjan forest 5069 trees were found to grow having 27 different species. The dominant tree species in the forest was Dipterocarpus turbinatus (telya garjan) the number of which 4760 constituted 93.30%. The next occurring species was Hopea odorata (telsur) having 118 trees constituting 2.33% in the forest. The other tree species that grew in the Silkhali forest from higher to lower or equal in proportion were L. speciosa (jarul), Mangifera indica (am), Syzygium cumini (kalo jam), T. grandis Institute of Forestry and Environmental Sciences Page 33
  • MATERIALS AND METHODS (teak), Bombax ceiba (tula), A. auriculiformis (akasmoni), Dillenia pentagyna (hargoza), G. arborea (gamar), Terminalia belerica (bohera), Terminalia chebula (horitaki), Macaranga denticulata (foke), Albizia lebbeck (kalo koroi), A. chapalasha (chapalish), Ficus benghalensis (bot), Dillenia indica (chalta), Vitex peduncularis (arsol), Erythrina variegata (madar) and Albizia chinensis (chakua koroi) constituting proportion between 0.73% and 0.02%. Other vegetation like grass, shrub and climber also grew as undergrowth in the forest along with numerous naturally regenerated seedlings of garjan, telsur, dhakijam, uriam etc. Good garjan forest: Geographical position of this site was at 21 o1΄429N and 092 0 11΄253E. At this soil sampling site surrounding canopy coverage by garjan tree was 80% and jam 20% with undergrowth coverage of 90% including 30% grass vegetation and 20% herbs and shrubs. Number of garjan trees of diameter varying from 45 cm to 50 cm and height from 23 m to 31m ranged between 175 and 200 ha -1 having 5.5 cm thick litter accumulation of weight 1.05 kg ha-1. Degraded garjan forest: At this soil sampling site, no garjan tree was present, but adjacent site contained few medium sized garjan trees. However, vegetation composition consisted of mainly herbs which changes seasonally. This site was at geographic position of 210 01’784N and 92011.057’E at 4 m elevation. This site was a patch on flat to gentle slope (2%) land. Denuded land: The denuded land was a small hill top of 2.5% slope on sandy loam soil having vegetation consisting of herbs and shrubs without any trees. In the past this site possessed similar ecological conditions as exists in good garjan forest. However, existing vegetation here was not static and changed repeatedly due to cattle grazing and growing of agricultural crops by the settlers. No litter coverage was found on the floor, because the previous garjan vegetation had been completely removed due to illicit felling over the time. Human habitation was on this small hill and managed for household purpose. 3.1.8 Medakacchapia mature garjan forest: Medakacchapia was a mature more than 100 years old natural garjan forest declared in 2005 as National Park situated 40 km north of Cox’s Bazar town beside Cox’s Bazar- Institute of Forestry and Environmental Sciences Page 34
  • MATERIALS AND METHODS Chittagong Road. Administratively, Medakacchapia is a Forest Beat under Fulchari Forest Range, Cox’s Bazar North Forest Division.This land is on 0-8% low hill slope at 14 m elevation above M.S.L. Canopy coverage of garjan trees in the forest ranged from 80% to 85% with undergrowth coverage of 70% to 80% having no grass vegetation. Height of D. turbinatus varied from 23 m to 25 m and diameter from 64.43 cm to 72.57 cm with mean height of 24 m and diameter 69 cm showing little variation both in size and density varying from 175 to 200 stems ha-1with mean of 183 stems ha-1. Litter cover was almost uniform over the forest providing mean depth of 2.83 cm and mean weight 4033 kgha-1. Deforested land: Deforested land is located at 0.6 km south from the above described natural forest situated at Boroitoli with geographic position 21 o48΄03΄΄N and 92o04΄43΄΄E. This deforested land contained 2 -3 garjan trees ha-1 on hill top only with about 95% undergrowth coverage of height ranging from 1 m to 1.5 m with few grasses. Litter depth was variable over the area with a mean depth of 1.83 cm and mean weight of 1033.3 kg ha-1. Soil profile was dug on lower part of the hill slope ranging from 5 to 25%. 3.1.9 Napitkhali: General description: Napitkhali Forest Beat is situated about 35 km away from Cox’s Bazar town, under Cox’s Bazar North Forest Division. The Beat possessed 974 ha forest, of which 946 ha reserved and 28 ha protected forest. Topographically the forest area is hilly having gentle to steep slope. In the area annual rainfall is very high being 4581 mm in 2003. To select representative study sites, a reconnaissance survey was made covering 500 ha land at Napitkhali Beat to find out a pair site representing plantation with adjacent deforested area. Site description: In the plantation of the pair site, tree coverage was 78% and undergrowth coverage 69%. However, their coverage was not uniform over the area. Tree covered area ranged from 60% to 90%, while undergrowth coverage ranged from 60% to 80%. The plantation was a mixture of several species viz. Acacia hybrid, Acacia auriculiformes, Syzygium spp. Etc with mean height of 9.51 m and dbh of 5.75 cm. The dominant planted tree species were Acacia Institute of Forestry and Environmental Sciences Page 35
  • MATERIALS AND METHODS hybrid and Acacia auriculiformis. The adjacent deforested site had no tree, grass and undergrowth, except some scattered fruit trees planted by the owner. 3.1.10 Boroitali: Natural forest: Boroitali Forest Beat is located by the side of Chittagong-Cox’s Bazar Road, 85 km away from Chittagong city under Chunoti Forest Range in Chittagong North Forest Division at geographical position of 21048΄005΄΄N latitude and 92004΄740΄΄E longitude. This was a mixed forest comprised of tall natural garjan and replanted garjan and jam species. Other associated species in this forest were Michelia champaca (champa), Syzygium fruticosum (khudijam/banjam), Lagerstroemia speciosa (jarul) Artocanpus chapalasha (chapalish) etc. Tree canopy coverage ranged from 80 to 95%. Undergrowth coverage consisted of herbs and shrubs ranged from 70-80% with no grass vegetation. Among tree vegetation Dipterocarpus spp. (garjan) constituted 80% and Syzygium spp. (jam) and other trees covered about 20% in this forest. Mean diameter of Dipterocarpus spp (garjan) trees was 36 cm and height 21 m. Diameters of Dipterocarpus spp. (garjan) ranged from 12 cm to 95 cm and height from 12 m to 29 m. Height of dominant trees was 18 m -29 m and shrub height 0.5 m -1.2 m. Density of trees in the forest was not uniform and varied greatly ranging from175 stems ha-1 to 325 stems ha-1 with a mean of 258 stems ha-1. Herbs, shrub and other vegetation as undergrowth coverage were 60%. Litter cover was almost uniform on forest floor of depth 1.67 cm and weight 783.3 kg ha-1. 3.1.11 Soil and water conservation centre in Bandarban The Bandarban Soil and Water Conservation Centre is situated by the side of Bandarban- ′ Chittagong Road and 5 km to the south of Bandarban City. It lies between 22 0 9′ 16′ ′ ′ ′ N and 22 0 10′ 32′ N latitudes and between 92 0 11′ 17 ′ E and 92 0 11′ 34′ E longitudes. This centre covers 27 ha land having elevation ranged from 92 m to 133 m above MSL. The centre is abundant with numerous plant as well as animal species. The major timber tree species are Tectona graandis (teak), Bombax ceiba (shimul), Ficus hispida (dumur), Dalbergia sissoo (sisoo), Melia sempervirens (ghora neem), Azadiracahta indica (neem), Swietenia mahagoni (mahagoni), Leucaena diversifolia (ipil ipil), Murraya paniculata (kamini), Erythrina variegata (mandar), Albezia procera Institute of Forestry and Environmental Sciences Page 36
  • MATERIALS AND METHODS (koroi), Delonix regia (krishnachura), Anthocephalus cadamba (kadam), Cassia fistula (sonalu), Dipterocarpus turbinatus (garjan), Artocurpus chaplasha (chapalish), Syzygium spp. (jam), Dhabanga grandifolia (bandarhola), Michelia champach (champa), Toona ciliata (toon), Lagerstromia speciosa (jarul), Gmelina arboria (gamar) etc. Moreover, there are fruit species, bamboo, cane, climbers, fern, medicinal plants and shrub species such as Cleodendrum indicum, Mussaenda roseburghii, Melastoma malabatricum etc. Among the mammals Macaca mulatta (monkey) and Panthera pardus (Indian leopard) are common, while among the reptiles Ophiophagus hanna (king cobra), Varanus salvator (monitor lizard) and Varanus bengalensis (Bengal monitor lizard) noteworthy. Selected 8 land covers: More than 25 land covers were present in Bandarban Soil and Water Conservation Centre. In the present study 8 land covers were selected to determine variations in soil properties and other features. The 8 selected land covers were (1) Mangifera orchard planted in 1995, (2) Syzygium orchard planted in 1995, (3) One yearold fallow land, (4) Pineapple cultivated area, (5) Bushy land, (6) Natural bamboo forest, (7) Natural forest, and (8) Deforested land. All the selected sites were situated side by side on relatively homogenous land, except deforested land. In absence of deforested land within the centre, one deforested land was selected adjacent to the centre having similar topography and site conditions. From each site, soil as well as litter samples were collected and then analyzed in laboratory for the physical and chemical properties. Besides, vegetation study was also conducted and described for each land use. The staff working in the centre helped in providing information related to past management of each land use. 1995 mango orchard: The mango orchard was situated to the north side of Syzygium orchard covering an area of 2.3 ha. The land possessed moderately very steep (40-46%) slope from east to west. During planting, fertile top soil and compost at a ratio of 1:1, and fertilizers like urea, triple super phosphate (TSP) and murate of potash MP were used at a ratio of 2:2:1 and at a rate of 250 g per pit. Tree canopy covered area on the land was about 90% with 600 stem density ha -1 with 10% ground coverage. Height of trees was 9.98 m and dbh 17.79 cm. The Surface soil in this orchard was covered by fresh, Institute of Forestry and Environmental Sciences Page 37
  • MATERIALS AND METHODS partially decomposed litter and humus, but possessed severe to very severe erosion hazard to the downward slope. The land possesses severe drought in the dry season. 1995 jam orchard: The Syzygium orchard covered 3.3 ha land was situated to the south side of Mangifera orchard on moderately very steep (40-46%) slope from east to west. During planting, fertile top soil and compost at a ratio of 1:1, fertilizers like urea, TSP and MP were also used at a ratio of 2:2:1 at a rate of 250 g per pit as basal dose. The orchard was covered by fresh, partially and completely decomposed leaf litter. Tree canopy covered area was about 85% with stem density of 500 ha -1 of 11.96 m height and 19.55 cm dbh. The land possessed 40% ground coverage. Fallow land: The fallow land covered 4.5 ha land and situated to the south-east side of meteorological station of the soil conservation center. No trees, herbs, shrubs and bushes were present on the land but enormous stones without litter present on the soil surface. This land was previously cultivated with HYV paddy of BR-26 on gently undulating (15%) land and BR-27 on moderately steep (25%) slope in 2003. The slope direction was from south to north. Paddy was grown on the hill slope without any sort of land disturbances like leveling of land, cutting of earth etc. The land experienced severe soil erosion hazard. Pineapple cultivated land: This land covering an area of 2.4 ha was planted with pineapple in January, 2006 situated to the north-eastern side of meteorological station. During planting of suckers, 2.5 g TSP and 2.5 g MP per plant was applied as basal dozes. Afterwards before and after rainy seasons urea, TSP and MP were applied at a rate of 2.5 g, 1.5 g and 1.0 g per plant, respectively, This site was located on nearly level to very steep (35%) medium high hills at an altitude of 153-181 m above MSL. The slope direction of the land was from south to north. Pineapples were planted along the contour. Narrow spaced pineapple suckers in the row acted as compact vegetation hedge barrier and arrested eroded soil material efficiently. Very few grasses with no litter were present on the land. Bushy land: The bushy land covered by an area of 1.6 ha was situated to the south of Syzygium orchard with 44% slope. The site was well-drained. The soil was dark Institute of Forestry and Environmental Sciences Page 38
  • MATERIALS AND METHODS yellowish brown to strong brown with a pH of 4.23. Very few grasses were present on the site covered with litter accumulation. Some of the undergrowth species found in the area were bhat (Clerodendrum viscosum), lajjabati (Mimosa pudica), assamlata (Eupatorium odoratum), kootumkata (Caeslpinia cristael), tokma (Hyptic suaveolens), taralata (Mikinia cordata) with a number of vines and medicinal plants. Natural bamboo forest: This bamboo forest covered 2.5 ha land and situated to the east side of bushy land. Slope percentage varied from 36% to 46% from west to east. The naturally bamboo grown site was moderately well-drained. Bamboo covered area was about 90% with no undergrowth. The number of culms/clump in this site was 32667ha -1 of height 10 m. Presence of fresh and partially decomposed bamboo leaves on the land. Natural forest: Natural forest covering an area of 5.3 ha was on the northern aspect situated to the north side of meteorological station. The slope of this forest land was steep (30-42%) from east to west. The forest was covered by fresh, partially and completely decomposed leaf litter and well-drained. Undergrowth vegetation consisted of a number of herbs, shrubs and climbers. Both tree canopy coverage and ground coverage was about 80% and tree stem density of 800 ha-1of various species in the forest. Tree height and dbh were 18.57 m and 29.43 cm, respectively. Deforested site: The site deforested long before was irregular with an average slope of 42%. The soil was well-drained. Soil erosion occurred on the land evenly because of huge disturbances of the villagers and cattle grazing. Undergrowth consisted of a number of herbs providing 15% ground coverage having no tree species and litter. 3.2 CLEAR FELLED AND BURNING AREA: 3.2.1 Hasanabad block: Fatikchhari is a natural mixed forest of Dipterocarpus spp. (garjan), Syzygium grande (dakijam), Michelia champaca (champa), Shorea robusta (sal), Albizia richardiana (rajkoroi), Swietenia macrophylla (mehogoni), Terminalia arjuna (arjun), Emblica officinalis (amloki), Terminalia chebula (hortoki), Terminalia belerica (bohera) and Litsea monopetala (meda) at Hasnabad block, Chittagong North Forest Division. Institute of Forestry and Environmental Sciences Page 39
  • MATERIALS AND METHODS Natural forest: This site was a patch of 10 year old natural garjan forest on flat hill top at 37 m elevation near Hasnabad Forest Range office. Previously this forest area was under mixed forest of Dipterocarpus turbinatus (garjan), Syzygium grande (dhaki jam) and Artocarpus chaplasha (chapalish). Canopy coverage of the patch of natural garjan forest was 90% with few scattered undergrowth. Undergrowth was mainly of Calamus guruba (jalibet) and seedlings of Dipterocurpus turbinatus. Forest floor was covered with thick layer of fresh and partially decomposed litter. Clear felled area: This clear felled site was 50 m west of natural garjan patch having similar elevation and topography. Previously clear felled area was covered with garjan, which felled in 2006. Canopy coverage of clear felled area was 10% with few scattered undergrowth, mainly of Calamus guruba (jail bet). Litter coverage and thickness at this area was lower compared to natural forest. 3.2.2 Hyanko block: Hyanko Forest Block was situated at Chittagong North Forest Division. This contained a pair of site, representing one plantation and one clear felled area. Plantation: This plantation was situated at the southern part of the Koila Bazaar under the Hyanko Block and Beat in Korerhat Forest Range. This was 25 year old garjan plantation, established in 1982. This site was on middle part of 19% hill slope. Canopy coverage of site was 90% and undergrowth consisted of Calamus guruba (jalibet), Melastoma malabathricum (bon tejpata) and different kinds of herbs. Clear felled area: This was a 2003 clear felled area, 200 m south side of garjan plantation. Before clear felling 40 year old teak plantation was present there and then planted with teak, garjan, mahagoni, dhaki jam, champa, chickrassi, arjun, haritaki etc. This site was on middle of 15% hill slope. This site possessed 60% canopy coverage with undergrowth mainly of Imperata cylindrica (sungrass), Melastoma malabathricum, Calamus guruba etc. 3.2.3 Feni block: Feni Forest Block was also in Chittagong North Forest Division. This contained a pair site, representing one plantation and one clear felled area. Institute of Forestry and Environmental Sciences Page 40
  • MATERIALS AND METHODS Plantation: This plantation was situated at the southern side of the Bhanga tower under the Feni block at Korerhat sadar Beat and Range. This was 41 year old Tectona grandis (teak) plantation and established in 1966. Plantation site was lying on the middle part of 17% hill slope. Coverage of plantation was 60% with Imperata cylindrica (sungrass) as characteristic undergrowth in the plantation. Other under growth species were bhat, dhumki etc. Clear felled area: This was a 2007 clear field area, 70 m west of teak plantation. Before clear felling of this site, 40 year old teak plantation was there, which felled in 2007. This site was also on mid hill of 20% slope. Tree canopy coverage at this site was 8% and undergrowth mainly Imperata cylindrica (sungrass), dhumki and Citrus lemon (lemon). 3.2.4 Ichamati: The study area for determination of clear felling effects on soil properties was at Ichamati Range under Chittagong North Forest Division. Ichamoti Forest Range is divided into three Forest Beats viz. Ichamoti, Bogabil and Nischintapur, covering an area of 2948.76 ha. Sampling sites both at 1956 teak plantation and clear felled area were situated in Thandachori Forest Block of Ichamoti Beat. Administratively, this site is situated at Rajanagar Union under Rangunia Upazilla in Chittagong District. Rangunia Upazilla lies from 22018′N to 22038′ N latitudes and from 91058′ E to 9209′ E longitudes. About 70 years back, Rangunia Upazila was rich in forest, consisted of a mixture of many tropical evergreen and deciduous species occurring in association with bamboo jungle as undergrowth. Following widespread deforestation in Chittagong Forest Division, artificial plantation was started in 1949 with Tectona grandis (teak), Dipterocarpus spp. (garjan), Terminalia chebula (horitaki), Terminalia bellirica (bohera), Terminalia arjuna (arjun), Lagestroemia speciosa (jarul), Hopea odorata (telsur), and Shorea robusta (sal), which till now continued. 3.2.5 Chittagong University campus: Chittagong University campus contained following 3 pair sites for determination of clear felling effect on carbon storage, which are described below: Institute of Forestry and Environmental Sciences Page 41
  • MATERIALS AND METHODS Clear felled area with adjacent 14 year mixed plantation: This site contained clear-cut area and adjacent 14 year old mixed plantation of Garjan, akashmoni and eucalyptus. The clear-cut area was on eastern aspect situated to the north of Forestry garage, Chittagong University with the geographical position 22 027′890″N and 091047′785″E. The area was previously covered with 14 year old Akashmoni plantation. It was a moderately steep hill (18%) like other sites with ground coverage of 40%, scattered covered with creeper, herbs and grasses etc. The adjacent mixed plantation of Garjan, Akashmoni and Eucalyptus was 14 year old. The plantation hill was facing the Southeastern aspect and slope was 25%. The canopy coverage of the area was 75% with ground coverage of 35% mainly, covered by grass and herbs mainly by bhat with little or no litter. Clear felled area with adjacent 16 year mixed plantation: This pair site contained clear-felled area of 2007 and adjacent 16 year old mixed plantation of Chickrassi (Chickrassia tebularis) and Jarul (Lagerstroemia speciosa). Geographical position of this clear-cut site was 22027′939″N and 091047′769″E facing eastern aspect situated to the South of Paharika housing society, Chittagong University. The area was previously covered with 14-year-old Akashmoni plantation. It was a moderately steep hill (15%) with ground coverage of 40%, scatteredly covered by creeper, grasses and herbs mainly bhat. The adjacent mixed plantation of chickrassi and jarul was 16 year old. Slope was 20% and site was facing the eastern aspect. The canopy coverage of the area was 70% with ground coverage of 45% mainly, covered by climbers, bhat, grass etc. with little or no litter. Clear felled area with adjacent 20 year mixed plantation: The clear-cut area was on northeastern aspect situated to the west of the Nipobon school in Chittagong University located between 22028′148″N and 091047′612″E. This was clearfelling area of 2007 with adjacent 12 year old mixed plantation of mahagoni and koroi with similar edaphic conditions. The area was previously covered with 14-year-old akashmoni plantation. It Institute of Forestry and Environmental Sciences Page 42
  • MATERIALS AND METHODS was a moderately steep hill (24%) with ground coverage of 50%, covered by scattered bhat (Clerodendrum viscosum), asamlata (Eupatorium spp.) and grasses. The adjacent mixed plantation of Mahagoni and Koroi was of 20 years old. Slope and aspect were similar to clear felling area. The canopy coverage of the area was 75% with ground coverage of 80% mainly, covered by climbers, grass and herbs mainly bhat having litter of 2cm depth. Burning: Hilly land within the Chittagong University campus is brought under forest through plantations during the last two decades. On the other hand, people from nearby villages used to cultivate hills outside campus from long before generation to generation. Therefore, to investigate effects on soil properties selected forest lands were within the University campus and burnt land situated adjacent to the campus. On adjacent land of the Chittagong University campus farmers do cultivation on hilly land after clearing the forest vegetation consisting of thickets, bamboos and grasses of the past time. Such a managed land situated to the north- west corner and beside the botanical garden area of Chittagong University was studied to see the effect of burning on some soil physical and chemical properties. The pair site representing burnt and no burnt land was as follows: Burnt area: In the burnt area all the vegetation of the land were slashed in DecemberJanuary and after drying burnt in mid February - March, i.e. in pre-monsoon time. Thus, no tree was present in the burning area except some thickets and grasses. No burnt land: The vegetation in no burnt area was highly disturbed due to biotic interference such as human interference, grazing etc. The land contained secondary vegetation such as thickets, along with a few scattered trees, thatching grasses and some bamboos. 3.2.6 Fulchari: This study area for determination of clear felli ng effects was at Fulchari Beat and Range, under Cox's Bazar North Forest Division. Fulchari Range had total area of 3573.66 ha of which Reserved Forest comprises 3505.67 ha and the rest 67.99 ha protected forest. Fulchari Forest Range includes five Forest Beats, namely Fulchari, Medhakachapia, Khutakhali, Napitkhali and Rajghat. Administratively, the Fulchari Beat is situated at Chokoria Upazilla in Cox's Bazar District. The topography of the Institute of Forestry and Environmental Sciences Page 43
  • MATERIALS AND METHODS area is irregular consisting series of ridges (Das, 1980). Soil in the study area varies from clay to clay loam on level land and from sandy to coarse sandy on hilly land (Chowdhury, 1969). The forest area has four main geological formations, namely: Pleistocene, Pliocene, Mio-Pliocene and Miocene (Balmforth and Howlader, 1988; Mabud, 2001). The forest area is generally hilly with gentle to steep slopes. Locally sandy loam on ridges and silty clays in basins occupy small areas having strongly acid reaction. Some of the higher valley soils are moderately well-drained with brown, loamy, moderately structured and very strong acid sub-soil (Mabud, 2001). The natural forest is characterized by the presence of dominant species such as Acacia hybrid, Acacia acuriculiformes, Syzygium spp., and others, shrub species like Cleodendrum indicum, Mussaenda roseburghii, Melastoma malabatricum and others. The natural forest habitat found in the study area is generally poor in quality. Unfortunately, collection of forest products such as fuel-wood and others by the people residing inside and around the forests and clearing of forest areas for the cultivation of agricultural crops have been adversely affecting the quality of vegetation. 3.3 SHIFTING CULTIVATED AREA: The land area of Chittagong Hill Tracts (CHTs) is 13180 km 2 with a population of 1587000 (BBS, 2011) and constitutes about 75% of the total hills of Bangladesh (Khisa, 1997). Administratively, CHTs consist of Rangamati, Khagrachari and Bandarban district and possess 10% landmass of Bangladesh. This hill tracts region provides biggest share of forest resources owing second largest reserve forests (322,331 ha or about 24% of the region). Demographic and environmental conditions are changing rapidly in this mountainous region. Due to scarcity of suitable land, the traditional slash and burn farming system, locally known as Jhum cultivation, is becoming unsustainable. This cultivation system combined with other factors such as over exploitation of the forest is the cause of increased land degradation, such as soil erosion, nutrient decline and decreased biodiversity. Most of the hills in CHTs are of Tertiary age and contain high hill ranges (350 m – >1000 m above MSL). The hills comprise the higher parts of major anticline and possess steep Institute of Forestry and Environmental Sciences Page 44
  • MATERIALS AND METHODS slope (>40% to over 100%). In the high hill ranges, rocks are semi-consolidated to consolidated possessing Surma and Tipam formations of Oligocene to Miocene age. In the hills, rocks are mainly shale, siltstone, sandstone and some conglomerate, and considerably folded, faulted and uplifted. In the region, the anticlines form the hills and the synclines form the valleys. The intensity of the folding is greater towards east, causing higher topographic elevation in the eastern CHTs. Tipam formation has a thickness of about 1,200 m to 2,500 m and the Surma formation of about 3,500 m to 4,500 m. Surma formation is probably the most important stratigraphic unit in Bangladesh represented by great thickness and forms the backbone of the eastern hilly areas of Bangladesh. The hills consist of a series of anti-clinical ridges lying parallel to one another. The ridges are aligned approximately north-northwest to south-southeast. The three major rivers: the Karnafuli, the Sangu and the Matamuhuri along with their tributaries form the drainage system in this mountainous watershed with a total catchments area of approximately 1400 km2. The drainage of the Karnafuli river has been greatly affected by the construction of Kaptai dam in 1962 for hydro-electricity generation, submerging about 922 km2 of the Karnafuli river system and converted into an artificial lake. The river Karnafuli divides this upland area into nearly two equal parts. In the northern part of the river 5 major hill ranges separated the valley of Feni, Chengi, Maini, Gangaram, Kassalong and Sajek Rivers, while in the southern part five main ranges separated the valley of Bakhhali, Matamori, Sangu, Ringkheong and Thega Rivers. These river-valleys are mostly narrow with a wide belt of hills of varied elevation on both sides. The highest peak of Bangladesh is situated in Bandarban, named as Tajindong (1230 m). All hill ranges are very steep with slope> 400. The eastern side of the ranges is steeper than the west. This steepness contributes greatly to the serious problems of erosion. The mountain ranges of the CHTs are characterized by a huge network of trellis and dendrite drainage ending into the Bay of Bengal. Within CHTs the Karnafuli has several important tributaries, of which Chengi, Kasalong and Rainkhiang are the main ones. The hill ranges and the river valleys are generally longitudinally aligned. Four ranges, with an average elevation of 330 m from west to east are Phoromain, Dolajeri, Bhuachhari and Barkal with highest elevation of 463 m, 429 m, 611 m and 735 m, respectively. Seven main Institute of Forestry and Environmental Sciences Page 45
  • MATERIALS AND METHODS mountain ranges from west to east namely Muranja, Wayla, Chimbook, Batimain, Politai, Saichal-Mowdok and Saichal are situated to the South of the Karnafuli River with highest peaks between 526 m and 1,003m. Saichal range contains the highest peaks of Bangladesh situated on the border with Myanmar. Some hill ranges also contain important geological structures such as Semutang, Sitapahar, Matamuhuri and Bandarban anticlines to form excellent structural traps for natural gas accumulation. Rainkhiangkine and Bagakine natural lakes and Kaptai artificial lake are situated in CHTs. Under shifting cultivated land topsoil is from 0- 20 cm, subsoil from 20 – 50 cm and substratum from 50 - 80 cm with variable depth from place to place, particularly hill position such as, hill top, middle and bottom. The substratum occurs at a variable depth. The texture varies widely from sandy clay loam to clay, depending on the type of parent rocks. Soils at all depth are well drained formed on sandstones, siltstones and shale parent materials. Under forest vegetation the color of the topsoil becomes dark yellowish brown to very dark grey and in the substratum becomes strong brown. Under shifting cultivated land the color of the topsoil becomes dark olive brown to brown, in subsoil olive yellow and in the substratum yellowish brown. Under forest topsoil is very strongly acid (pH 4.6) and under shifting cultivated soil very strongly acid to strongly acid (pH 3.98 – 4.88) with slight increase in pH with depth. In surface soil C/N ratio ranges from 10 – 14 and in the substratum 6 - 9. In the surface soil available P ranges from 1.6 – 12 mg/kg soil, available Ca from 2.3 - 6.5 mg/kg soil, available Mg from 0.5 – 1.6 mg/kg soil with increase in subsoil and decrease in substratum. The climate of this mountainous watershed is characterized by tropical monsoon with mean annual rainfall 282 cm in Kaptai and 257 cm Rangamati (UNEP, 2001). This area experiences long dry season from October to May and monsoon wet season from June to September. Cyclones are frequent during May to October. Over 80% of the rainfall occurs between May and September. The dry and cool season is from November to March when temperatures range from 80C to 150C, pre-monsoon season from April-May very hot and sunny when temperatures range from 24 0C to 350C, and monsoon season from June to October warm, cloudy and wet when temperatures range from 20 0C to 360C. The relative humidity ranges between 65% in the dry season and 90% during monsoon. Institute of Forestry and Environmental Sciences Page 46
  • MATERIALS AND METHODS In recent years, the weather pattern has been erratic, with a reduction of the cool, dry season and late rainy season, which may be beginning of long-term changes due to global warming caused by greenhouse gases. The annual stream flows of the Karnafully, the Sangu and the Matamuhuri rivers are 3.67 million hectare meter, 0.66 million hectare meter, and 0.44 million hectare meter, respectively. During the driest month in March, about 92% flow of the Karnafuli River is coming from the Kaptai reservoir. In CHTs only 6% land suitable for intensive production of agriculture (Khisa, 1997). Within CHTs Unclassed State Forest lands occupy 10,121 km2, Kaptai Lake and other water area 535 km2 and the rest 2,581 km2 under reserved forest. In CHTs only 3-5% lands have few limitations for crop production occupying valleys of the region used for variety of field crops, 20% of the lands possess moderate to severe limitations to crop production and suitable for horticulture and the rest 75% vulnerable hill slopes of steep to excessively steep have severe limitations for general crop production. The major land uses in CHTs are shifting cultivation, horticulture crops, tea, rubber, yam and ginger on different parts of the hill slope without considering soil loss in many cases (Shoaib, 1997). Most parts of hill are under teak plantation and managed by Bangladesh Forest Department. Previously population pressure was confined only in the lowland watershed and at present population density is increasing in the hilly region at alarming rate because of migration of people from plain land in scarcity of traditional agricultural land. Population in CHTs in 1872 was 0.063 million and in 1998 became 1.1 million (Khisa, 1997). During the period from 1872 to1991, indigenous population rose from 0.062 million to 0.501 million, while non indigenous from 0.002 million to 0.473 million. 3.3.1 Kark Mohajon Para: Shifting cultivated soil: Ready for jhumming: Kark Mohajon Para is located on Khagrachari to Diginala Road under 26 No. Perachara Mouja. This site is about 11 km away from Khagrachari Sadar Upazilla and to Institute of Forestry and Environmental Sciences Page 47
  • MATERIALS AND METHODS the west side of Chiakhola. This area was on 28% hill slope. On this hill 3 soil profiles were dug on hill top near Chitakhola, an important feature for locating the place. 1 year old jhum cultivated area: One soil profile was dug in 1 year old rubber plantation where paddy grown as jhum crop last year. During soil sampling paddy straw was present on soil surface of one year rubber plantation. This site was to the south east of teak plantation. Above this sampling site 13-year old rubber plantation present on hill top and hill slope. Forest soil: 8 year old teak plantation: The 8-year old teak plantation was situated adjacent to shifting cultivated site to the east of ChitaKhola. The hill had 40% slope on the top portion, but lower portion >80% on southern aspect. In teak plantation no undergrowth was present. Shifting cultivation was done at this teak plantation area previously at least more than 3 times. Two soil profiles were dug on hill top in this 8 year old teak plantation. Earthworm activities were frequent in this profile. 4 year old gamar plantation: Two profiles slightly away from teak plantation were dug in four year old rubber plantation on bottom part of hill slope. 3.3.2 Simina Para: Following two land covers, one representing shifting cultivated land and the other by a patch of natural forest, were studied in this area: Ready for jhum cultivation: The area is located on Khagrachari to Dighinala road at Simina Para, which about 15km away from Khagrachari Sadar Upazilla with a geographical position of 23°12.041'N and 92°01.967'E. The area was ready for jhum cultivation during sampling date on 25 April 2007. Three profiles were dug in this jhuming area. Forest land: This hill was covered with different vegetation types on different parts of the slope. Vegetation on valley consisted of kalichari (Gigantochloa andamanica) 50%, Neohouzeana dullooa (dolu) 20%, Melocanna baccifera (muli) 30%. Vegetation on hill slope consisted of Syzygium fruticosum (puti jam), Aphanamixis polystachyd (rahunia), Institute of Forestry and Environmental Sciences Page 48
  • MATERIALS AND METHODS Abroma augusta (ulot kambal) toprin gach, which is used by bird as food materials, Qurcus spicata (batna), Artocarpus chaplasaha (chapalish), Tectona grandis (segun), Alstonia scholaris (chatim) etc. 3.3.3 Milan Karbari Para: Milan Karbari Para is located beside Khagrachari to Dighinala Road at Milan Karbari Para in Khagrachari Sadar Upazilla with a geographical position of 23°12.250'N and 92°01.749'E . This is a hilly area with an elevation of 201 m. Soil samplings were done from profiles of the following described pair site: Ready for shifting cultivation: This area was brought under banana plantation after slashing and burning. Previously jhum was done at this site four times. Now, this area was brought under rubber plantation and banana also planted in places. Forest land: This profile was on flat hill top, in a patch of bush. In this area jhum cultivation was done 20 year ago, but during soil sampling the area covered by different species mainly of Mecarenga scandea, Melastoma malabalthricum Linn., sulakhari etc. 3.3.4 Alutila: Demonstration plot on Sloping Agricultural Land Technology (SALT) of Chittagong Hill Tract Development Board (CHTBD) was located at Alutila under Matiranga upazila of the Khagrachari district. Chittagong Hill Tracts Development Board (CHTDB) established this farm in July 1993 as a pilot project under SALT. It was one of the programmes of International Centre of Integrated Mountain Development (ICIMOD) at Kathmundu, Nepal. The total project area was about 20.61 ha, of which 18.94 ha for the SALT demonstration farm and 1.67 ha for the intended farmers (SRDI, 1991). Soil samples from the site were collected on May, 2003. The project manager of Chittagong Hill Tracts Development Board (CHTBD) helped to select four different hill farming sites including modern and traditional farming system to make a comparison of jhumming effects on soil properties. The description of each of these sites is given below: Institute of Forestry and Environmental Sciences Page 49
  • MATERIALS AND METHODS SALT abandoned area where no jhumming done before: This site situated on the east aspect, was one of the SALT demonstration plots which brought under SALT in 1994. In this plot no jhumming and any other form of cultivation was done before. Here, the soil surface was covered with litter fully (100%). Naturally coming tree species were Kanchan (Bauhinia spp) of height 6.1 m, Rubber (Hevea brasiliensis) of height 19.14 m and Bogamedula (Indigofera spp) of height 1.5 m. This plot was also covered fully (100%) by the tree species and 50% land with herbs. This site having no jhumming before acted as control over the other three sites. 8 year old SALT adopted site, but abandoned in 2002: This SALT demonstration plot facing to the west aspect was under shifting cultivation until 1993 and brought under SALT in 1994. This land elapsed 8 years under modern salt technology upto 2002, after which left as abundant land from SALT cultivation. During the sampling on May, 2003 the land was covered with annual crop, horticultural and forest tree species along with 100% grass coverage. Horticultural crops included guava (Psidium guajava), litchi (Litchi chinensis), lebu (Citrus aurantifolia) and other fruit tree species. The main tree species in this plot was sada koroi (Albizia procera) of about 11 m height. However, this land was abandoned in 2002 from SALT. That means, this plot was not managed by SALT after 2002 due to completion of project period. Land ready for current jhumming: This site was outside the SALT demonstration plot. During sampling on 26 May 2003, the land was ready for jhumming and supposed to sow seeds in June of the same year. The site faces to the east aspect with 55% hill slope. Soil sampling was done on middle part of this hill slope. It was a burnt area, ready for shifting cultivation after necessary soil work having no litter, herbs, shrubs and trees. The site was kept fallow for three years from 2000 to 2003. Jhumming done in 2002: This SALT demonstration plot was fallow for the last one year situated on the west aspect of a steep hill slope. The site was covered with vegetation like, many flowering plants, few sungrasses, vegetables and naturally grown tree species. Vegetation included banana (Musa sapientum), Eupatorium odoratum and Mikania scandans and naturally grown tree species were Jangli begun (Solanum melongena), Dumur (Ficus roxburghii), Cycas ( Pnetum ula), Gamar (Gmelina arborea) and Koroi Institute of Forestry and Environmental Sciences Page 50
  • MATERIALS AND METHODS (Albizia spp). Very few Koroi trees were also present on this site. This land would be kept fallow for another two years after which land would be used for jhum cultivation again. 3.3.5 Sukurchhari Sukurchari under Kutukchari Forest Range is located beside Rangamati-ManikchariMohalchari-Khagrachori Road, about 7 km from Manikchari. Reconnaissance survey was first conducted at Sukurchari to find out pair land having shifting cultivated area of different years and natural vegetated land side by side. Survey showed that such pair site was absent in the area. For this reason following five different hills were selected at Sukurchari on north-west aspect, situated on west side only of the road. Shifting cultivated land: This site was one year old shifting cultivated land on medium high hill on eastern aspect at geographical position of 22 040′522″N and 092007′235″E. Paddy residues of the last year was still existed on the land with 75% grass vegetation and 15% ground coverage, mostly of asamlata of 80% (coverage cm in height). Mixed plantation: Adjacent to this shifting cultivated area mixed plantation of litchi, jackfruit, gamar, teak, supari and jam were present on upper part of the medium high hill at 22041′545″N and 92006′242″E geographical position. Tree canopy coverage of this plantation was 80% with full ground coverage and 4 cm litter depth. 3.3.6 Muralipara: Murali Para is located beside Gagra-Kaptai Road, Phulgaji Range under Jhum control division at Mulari Para under 100 No. Wagga Mouja, Kaptai, about 3 km from Gagra. One family has been residing permanently on lower part of hill slope at this shifting cultivated area and used to do shifting cultivation on the hills. Here, the whole hilly area was under shifting cultivation rotationally. On shifting cultivated land on hill slope having 65% gradient on western aspect major crops were turmeric (Curcuma longa), zinger (Zingiber officinale), sajina (Moringa oleifera), arum (Abrus precatorius) and banana (Musa paradisiaca). Institute of Forestry and Environmental Sciences Page 51
  • MATERIALS AND METHODS Shifting cultivated land: This site was 2 year old slashed and burnt area, situated at Mulari para on the way to Gagra, Kaptai Road, under Phulgaji Range and Jhum Control Division. In this shifting cultivated area vegetation was wild banana on medium high hill facing the eastern direction at geographical position of 22 034′942″N and 092006′229″E. Sungrass was the only ground vegetation in this land with 15% coverage. Mixed plantation: The area was a patch of forest, adjacent to the shifting cultivated area. The land was under 25 year old jackfruit, blackberry and mango tree plantation along with bamboo and sun grass (Imperata cylidrica) as undergrowth. On this hill, tree canopy coverage was 30% and undergrowth coverage 70%. 3.3.7 Burburichhara Shifting cultivated land: This site was located in Barkal upazila of Rangamati district with the geographical position of 22043′703″N and 92021′219″E. This was a hilly area having 100 % slope with an elevation of 364m on the north-west aspect. Shifting cultivated crops were paddy, turmeric, gamar and banana with the presence of some grasses in patches. Mixed plantation: Adjacent land was a mixed plantation of koroi, gamar, tula, and teak along with bamboo, sungrass, baruna, wild banana etc. This site was on steep (100%) high hill on north-west aspect at 22 043′699″N and 92021′150″E geographical position. In this plantation tree canopy coverage was 98% and undergrowth coverage 80% having 4 cm forest floor. 3.3.8 Maijchhari Shifting cultivated land: Maichchari shifting cultivated area was located in Barkal upazila of Rangamati district at geographical position of 22043′612″N and 92019′695″E. This was a hilly area having 80 % slope facing the south-western aspect. In this shifting cultivated area crops were paddy, turmeric and banana. Mixed plantation: The adjacent mixed plantation was of teak, jam, vadi, jarul and hijal on medium high hill of 90% slope on south-west aspect at 22 043′606″N and 92019′745″E Institute of Forestry and Environmental Sciences Page 52
  • MATERIALS AND METHODS geographical position. Tree canopy coverage in this plantation was 70% with 30% undergrowth. 3.3.9 Longadu: Shifting cultivated land: The shifting cultivated land in this pair site was situated at Longadu upazila to the north-western part of Rangamati district at geographical position 220 50′614″ N and 92017′417″ E on steep high hill facing south eastern aspect. Shifting cultivated crops were paddy, banana, turmeric etc. with no undergrowth. Mixed plantation: Adjacent mixed plantation of teak and gamar was on steep high hill (100% slope) on south–eastern aspect at 22045′512″ N and 92018′545″ E geographical position. Tree canopy coverage on this hill was 70% with 40% ground coverage, mostly of herbs with very little or no litter. 3.3.10 Betchara: Betchara is located on Bandarban-Chimbuk Road at 314 No. Soalok Mauza, 9 miles away from Bandarban Sadar district. The site is under Betchara Forest Range of Bandarban Forest Division with geographical position of 22º07′45″ N and 92º13′42″E. This is a hilly area having 10-24 % slope and an elevation of 364 m on the north-west aspect. Soil sampling was done on first week of February 2007 at upper part of the slope. Reconnaissance survey was conducted first to find out pair lands having jhuming area of different years and natural forest/ natural vegetated areas side by side. In absence of natural forest and shifting cultivated area on the same hill, soil samplings were done from three different hills having slashed area, 1-year shifting cultivated area and forest area on three separate hills. Shifting cultivated soil: Reconnaissance survey was conducted first to find out pair lands having jhuming area of different years and natural forest/ natural vegetated areas side by side. Betchara is located on Bandarban-Chimbuk Road at 314 No. Soalok Mauza, 15 km away from Bandarban Sadar district under Betchara Forest Range of Bandarban Forest Division with the geographical position of 22°07.45' N and 92° 13.42' E by the side of Bandarban Chimbuk Road. At Betchara no natural forest was found and comparison made between slashed area and one year jhum cultivated area. Here, three profiles were Institute of Forestry and Environmental Sciences Page 53
  • MATERIALS AND METHODS studied in slashed area on three hill positions - top, middle and bottom, and 3 profiles on 1 year old jhum cultivated area on different hill positions. Site descriptions of slashed and 1 year shifting cultivated are given below: Slashed area: This was a three year old shifting cultivated area, which slashed again for jumming. This was a round topped hill having 10-24 % slope on the north-west aspect. Slashing is the first stage of shifting cultivation in which all the previous vegetation on the land is cut down and allowed to dry, after which land burnt. The vegetation during soil sampling was consisted of only a few bamboo, banana, papaya etc. On this hill three profiles were dug - one on the hill top, second one on the middle part of the hill and third one on hill bottom. One year shifting cultivated area: One year old shifting cultivated area was on separate several hills slightly away from slashing hill at 314 No. Soulok Mouza, 15 km from Bandarban Sadar. Hill slope was 12% on north-west aspect and around this hill, steep hill slope present. Soil profiles were dug on this hill at top, middle and bottom part. Forest soil: This site was located on a different hill near to shifting cultivated site with a geographical position of 22°07' 19 N and 099°13'41 E. Slope at hill top was 16% with an elevation of 350 m and at middle to lower part 26% slope on north-west aspect. Forest vegetation was mainly of bamboo with few shrubs and climbers. 3.3.11 Tarasa: Shifting cultivated soil with bushy land: Khanshama para, Tarasa is located on Bandarban to Ruangchari Road under Tarasa Forest Range of Bandarban Forest Division, with a geographical position of 22°12.20' N and 92°15.38' E. This was a hilly area with a slope of 12 % on north-west aspect. This was a long hill, having absence of any forest, for which comparison done with naturally grown sporadic bushes. On this hill, three samples were collected from shifting cultivated area and three from bushy area at a depth of 0-6 cm. Three soil samples from each land use are mixed together to make a composite sample. The area was jhum cultivated one year before. Institute of Forestry and Environmental Sciences Page 54
  • MATERIALS AND METHODS 3.3.12 Thanchi: Selection of soil sampling sites: Two paired sites, one on 55% slope and the other on 35% slope, were selected in orange growing area at Bolipara under Thanchi Upazilla. In each pair, one part represented orange orchard and the other forests, being adjacently located on similar slope to avoid initial variation in soil properties between the two, due to topographic differences. To provide clear idea description of two paired sites is given below: On 55% slope: Orange orchard: This hill slope faces eastern aspect. Northern part of this slope was under orange (Citrus aurantaneum) orchard and the southern part under forest cover. Orchard floor was covered by orange (Citrus auruntaneum) trees fully (100%) along with herbs as undergrowth. The undergrowth comprised of various grasses including lojjaboti (Mimosa spp.). The mean height of the orchard was 3.5 m with an average diameter of 4.7 cm planted with a spacing of about 2.5 m × 2.5 m. Other naturally growing species in the orchard was banana (Musa sapientum). The orchard was subjected to partial weeding which included shrub cutting and the land possessed black colored top soil with earthworm activities. Forest land: On this slope, forested area was fully (100%) covered by herbs, shrubs and bushes. In absence of large trees the land lacked abundance of litter. This forest land was subjected to severe erosion. The naturally growing shrubs were ashamlota (Eupatorium odoratum) and lantana (Lantana camera) with an average height of 1.20 m. On 35% slope: Orange orchard: The site faces eastern aspect of the hill. Orchard floor was covered by orange (Citrus auruntaneum) trees (100%) along with herbs as undergrowth. The undergrowth comprised of various types of grasses including lojjaboti (Mimosa spp.), lantana (Lantana camera) etc. The height of the orchard was 3.1 m with an average diameter of each tree 3.9 cm planted with a spacing of 2.5 m × 2.5 m. Other conditions in this orchard were similar to previously described orchard grown on 55% slope. Institute of Forestry and Environmental Sciences Page 55
  • MATERIALS AND METHODS Forest land: This part containing forests was also covered by herbs, shrubs, bushes along with a few trees, which were dispersed over the area and the forest floor without litter. The naturally growing species were ashamlota (Eupatorium odoratum), lantana (Lantana camera), lojjaboti (Mimosa spp.), koroi (Albizia procera), dumur (Ficus spp.) etc. The average height of shrubs was 1.25 m and of Koroi (Albizia procera) tree 6.35 m and Dumur (Ficus spp.) 3.10 m. Similar to previous forest land (on 55% slope) this part was also eroded. 3.3.13 Bandarban Sadar: The study was done in Bandarban hill district of Bangladesh where local people practice shifting for their livelihood. To select representative study sites, a preliminary survey done in the shifting cultivated areas and its adjacent natural forest of Bandarban Sadar Upazila. During the preliminary survey local tribal people and FD officials were interviewed to find out the study sites based on years of shifting cultivation practices and presence of natural vegetation adjacent to it. Thus, three pair lands were selected namely 1 year, 2 year and 3 year of shifting practices, respectively, and their adjacent natural forest in Bandarban hill district. A brief description of the three pair lands is given below: 1 year shifting cultivated area with adjacent natural forest: This site was situated on the middle position of a hill slope at Na-mile village under Bandarban Sadar Upazila. The average slope was about 28 %. In this site shifting cultivation was done 1 year before. The tree species of shifting cultivation included gamar, segun, and goiree, covered 45 % of the land by crown. Natural forest was situated adjacent to the shifting site. Bamboo, banana, gamar, siyez, sil koroi, goda, dakudum, banlata and other unknown trees, shrubs and herbs were present in the natural forest. Canopy coverage of the trees was 100 %, ground vegetation occupied 70 %, and grasses occupied 20 % of the total area. Presence of litter coverage was 40 % of the total area. 2 year shifting cultivated area with adjacent natural forest: This site was situated on the middle position of a hill slope at Shoalok village under Bandarban Sadar Upazila. The average slope was about 35 %. In this site shifting cultivation was done 2 years before. Institute of Forestry and Environmental Sciences Page 56
  • MATERIALS AND METHODS The crops of shifting cultivation included paddy, marfa, papya, pumpkin, banana etc. During soil sampling in shifting cultivation had no vegetation coverage. Natural forest was situated adjacent to the shifting site. Bamboo and other unknown trees, shrubs and herbs were present in the natural forest. Canopy coverage of the trees was 90 %, ground vegetation occupied 58 %, and grasses occupied 10 % of the total area. Presence of litter coverage was 30 % of the total area. 3 year shifting cultivated area with adjacent natural forest: This site was situated on the middle position of a hill slope at Aat-mile village under Bandarban Sadar Upazila. The average slope was about 34 %. The shifting site was jhumed 3 years before. Long period and short period crops were found in shifting site. The crops of shifting cultivation included paddy, sesame, papya, cotton, maize, jack fruit etc. however underground coverage 50 %. Natural forest: Natural forest was situated adjacent to the shifting site. Bamboo, konak, goda, seuli, sil-koroi, banana and other unknown trees, shrubs and herbs were present in the natural forest. Canopy coverage of the trees was 100 %, ground vegetation occupied 75 %, and grasses occupied 30 % of the total area. Presence of litter coverage was 35 % of the total area. 3.4 Soil sampling: For determination of bulk density, 3 undisturbed soil cores or more in some places were collected in the field from 0 – 5 cm depth by pre-weighed cores. Cores were driven vertically into soil using wooden hammer. The cores were then carefully dug out using a sharp knife and excess soil at both ends removed. Then both the ends of the cores were wrapped with two small pieces of cloths and rubber bands, and carried in a labeled plastic bag to the laboratory for subsequent analysis. The field moist soil cores then weighted, allowed drying in an oven 105 0C for 8 hours, cooled in a desiccators and reweighed. Both the field moist and oven dry weights of the cores were divided by the volume of each core (100 cm3) to determine wet and dry bulk density, respectively. 3.5 Determination of organic carbon in soil For the determination organic carbon in soil, washed silica crucibles were dried in oven at 1050 C for 30 minutes and cooled in desiccators and then weight were taken. Dried Institute of Forestry and Environmental Sciences Page 57
  • MATERIALS AND METHODS soils were grind by pistol and then exactly 5g of grind soils were kept in silica crucibles and weighted by an electric balance. The crucibles with soils were then transferred to an electric muffle furnace for igniting at 8500 C for one and half an hour. Then crucibles with soils were cooled in a desiccators and reweighted to determine the percent loss of ignition (LOI%) LOI was expressed relative to the weight of oven dry soil and % of moisture relative to the weight of field moist soil. Percentage of LOI was calculated as follows: LOI (%) = w1 / w2 × 100 w1 = loss in weight and w2 = weight of oven dry soil Percentage of carbon calculated from the following relationship (Hoque and Alam, 2005) Organic carbon (%) = 0.476 × (% LOI – 18) 3.6 Calculation of C storage in soil: Organic carbon concentration of plantation area in 0-20 cm soil depth was 2.67% and for 20-30 cm soil depth 3.30%. From these values carbon storage were calculated as follows: i) For 0-20 cm soil depth: 1 ha soil with 15 cm depth weighs 2×106 kg 1 ha soil with 20 cm depth weighs =2.67×106 kg Now for, Organic carbon = 2.67% That means, 100 kg soil contains 2.67 kg organic C Institute of Forestry and Environmental Sciences Page 58
  • MATERIALS AND METHODS Therefore,1.6×106 kg soil contains organic C per ha = ton organic C per ha = 71.29 t/ha ii) For 20-30 cm soil depth: 1 ha soil with 15 cm depth weighs 2×106 kg 1 ha soil with 10 cm depth weigh7s =1.33×106 kg Now for, Organic carbon = 3.30% That means, 100 kg soil contains 3.30 kg organic C Therefore, 1.33×106 kg soil contains organic C per ha = t/ha = 43.89 t/ha Now, organic C content for 0-30 cm will be = (71.29+43.89) t/ha = 115.18 t/ha Thus, the amount of organic carbon was calculated from the following relationship for the other soil samples: ha Institute of Forestry and Environmental Sciences Page 59
  • MATERIALS AND METHODS 3.7 Calculation of CO2 sequestered in a standing tree: Total green weight of a tree: For trees with dbh < 11 inches W = 0.25D2H (Richard, 1992) For trees with dbh >= 11inches W = 0.15D2H (Richard, 1992) W = Weight of the tree in pounds dbh = diameter at breast height (in inches) H = Height (in feet) up to top of the tree Depending on the species, the coefficient 0.25 is variable for dbh >11. D 2 and H could be raised to exponents just above or below 1. However, these two equations could be seen as an “average” for all the species. The root system weighs about 20% as much as the above-ground weight of the tree. Therefore, to determine the total green weight of the tree, multiply the above-ground weight of the tree by 120%. Determination of dry weight of the tree: All species of the tree is contained 72.5% dry matter or 27.5% moisture. To determine the dry weight of the tree, multiply the weight of the tree by 72.5%. Determination of C weight in tree: To determine the weight of carbon in the tree, multiply the dry weight of the tree by 50%. Average C content is generally 50% of the total volume of tree. Determination of weight of CO2 sequestered in tree: CO2 is composed of one molecule of C and 2 molecules of oxygen. The atomic weight of C is 12.001115. Institute of Forestry and Environmental Sciences Page 60
  • MATERIALS AND METHODS The atomic weight of O2 is 15.9994. The weight of CO2 is C+2*O=43.999915. The ratio of CO2 to C is 43.999915/12.001115=3.6663. Therefore, to determine the weight of carbon dioxide sequestered in the tree, multiply the weight of carbon in the tree by 3.6663. 3.8 Calculation of CO2 production (IPCC, 2001) CO2= 12+ (16 x 2) =44 12 t C produces 44 t CO2 So, 15.2475 t C produces (44 x15.2475)/12 = 55.9075 CO2ha-1 This study has been done in continuation of the works done by several authors (viz. Miah et al, 2010; Haque et al., 2012; Haque and Karmakar, 2009 and Biswas et al., 2011 ) on upland watershed in Bangladesh on several aspects of soil and vegetation, but they did not work on C-sequestration in soil and forest vegetation. In this thesis, therefore, study has been done on the effects of several human induced activities such as deforestation, clear felling and shifting cultivation on C-sequestration in soil and forest vegetation of Chittagong and CHTs regions. Institute of Forestry and Environmental Sciences Page 61