The Barriers on Natural Regeneration of Degraded Peatswamp Forest
BARRIERS TO SEEDLINGS REGENERATION IN FIRE-DAMAGED TROPICAL PEATLAND OF BRUNEI DARUSSALAMInternational Conference on Wetland Forest, 22-23March 2012, Rizqun International Hotel,Bandar Seri Begawan, Brunei Darussalam DR. HJH DULIMA JALI, GEOGRAPHY & ENVIRONMENTAL STUDIES PROGRAMME, UNIVERSITI BRUNEI DARUSSALAM
IntroductionDestruction of Southeast Asia’s peat swamp forest is widelyacknowledged to be a serious problem, causingdegradation of water catchments, losses of biodiversity andexacerbating rural poverty.Most countries are now attempting to solve the problem byprotecting remaining forest and launching large restorationproject to meet local and national objectives, includingcountries’ international obligations following the UnitedNations Conference on Environment and Development.Large-scale restoration of complex tropical peatland forests isa comparatively modern dilemma, which has beenapproached in a variety of ways.
Selection of Approaches• To select an appropriate approaches to forest restoration a manager needs to asses actual and potential levels of natural regeneration and this demands a high inputs of ecological information of each site.• It also requires an understanding of the factors limiting successional change and increases in desired species towards the desired objectives.• Directing natural successional processes towards the desired goal requires an understanding of the processes driving succession and limitations that halt natural recovery.• These include:− Functional hydrological condition.− Soil ConditionNutrients status and cycling− Energy flow processes
Why need to identify factors that hamper / arrest regeneration processes?It is essential to understand the mechanisms ofregeneration and succession and the ecologicaldynamics of an ecosystem for effective and realisticmanagement planning.These are crucial for the interpretation of the highspatial-temporal variability found in post-fire speciesperformance.Such knowledge also necessary to assess thepotential of different regeneration mechanisms tocope with ongoing land-use and climate change.
UNDERLYING CAUSES HALTING / ARRESTING NATURAL SUCCESSIONMany studies throughout the neotropics tropical forestshave shown that a number of interacting factors mayimpede tropical forest natural regeneration.These include :Disturbance: fire, Drought, herbivories, anthropogenicSite Resources: water, soil nutrient availabilityCompetition from weeds.Roots competition.Plants and propagule availability: Seeds banks, seed rainsSeed dispersal limitations,Seeds / seedlings predationDistant from existing forests
Study AreaThis study was conducted in the Belait - Badas Peat Swamp, in Brunei Darussalam (4°15-4°39N, 114°05-l14°29E) an area of state land statute under the jurisdiction of Forestry Department of Brunei
Objectives of the StudyTo develop a better understanding of theunderlying ecological processes in regeneration offire affected peat swamp forest of Badas, BruneiDarussalamTo investigate / identify the biophysical barriers to thecolonization and natural regeneration of the plantcommunities in burnt areas that have been invaded by fernsand sedges.
Methodso Seedlings of several timber three timber species Agathis alba, Shorea pachyphylla, Dryobalanops rappa and non-timber tree species were planted in each transects and their growth were monitored for three years at 1 – 3 intervals.o The growth of naturally established peatland species were also monitored.o Seeds of several typical peatland species ( Timonius spp, Tetractomia spp, Ficus spp. saga, mempening) are disperse randomly.o Treatment: Control (no cutting), clearing weeds.o Dispersing seeds of non-timber species randomly
RESULTSFactors that dictated natural regeneration ofseedlings are:Site Hydrological Condition: site particularly thedepth of the water-tableWet SiteNatural regeneration flourish in site with high watertable ( < 20 cm below surface)Dominant species: Tetractumia beccari, Eugeniaspp, Litsea spp, Hoorsfieldia crassifolia.
Dry SitesVigorous growth of early post fire colonizersStenochlaena palustris, Pteridium aquilinum andBlechnum indicum that cover almost the entire surfacewith their strangling stems or dense leavesThis condition significantly hamper the establishmentand growth of seedlings.At least five species of woody plants - Teminius,Horsfieldia, Syzygiumspp, Ficus and Uncariaspp havethe capacities to germinate directly within the less densestand of ferns and grasses, indicating these species highcompetitive ability and adaptability to a wide range ofabiotic circumstances.
Survival Rates of planted seedlings Timber Seedlings 90 %Control 0% <2%Cut weeds Once 0% 3%1 – 3 months cut 65 – 85 % 70 -85 % Survival of Each species group Agathis 70 -80 % Dryobalanops rappa 60 – 75 % Shorea pachyphylla (1 yr) 80 – 90 % Non-timber species 85 – 95 %Environmental condition ( 2005 – 2009) is relatively good with no lengthyrainless period.
Competition with ferns and grassesIf seedling managed to establish among the ferns theirgrowth are greatly reduced.Seedlings are overgrown by the ferns and remain coveredand hidden between the ferns resulting in deformedstems.Demonstrated by the growth of planted seedlings,especially the Agathis seedlings.The seedlings growth is boosted as soon as they escapedfrom the ferns that are when the ferns are removed.Controlling the growth of ferns and grasses causedsignificant changes in the species composition as moreseedlings appear particularly Teminius spp and severalspecies of Ficus, Eugenis, Calophyllum and Uncaria.
Lack of seedsThe seed bank is likely to be exhausted by the firebecause the organic nature of the substrate wouldhave produced intense heat that would havedestroyed any available seeds.More trees regenerating nearer to undisturbed forest.Dominant species are Lithocarpus sundaica(mempening); Eugenia spp. (ubar); Baccaureabracteata ( tampoi antu), Calophyllum spp(bintangor)
Limited dispersal mechanisms & activitiesLarge treeless areas are unattractive to most frugivorousdispersers.Extensive growth of early colonizer of fern and sedgescommunities limited dispersal activities given thatgrasses and fernlands offer few resources that attractseed dispersers particularly the birds and smallmammals.Seeds dispersal therefore appears critical in determiningthe diversity, density, and location of naturalregeneration. Perching sites such as isolated trees can accelerateecological succession processes.Most generating species are birds dispersed
Existing surviving trees and distant from forest edge The existence of surviving timber trees also showed some influence on the regeneration processes. These survivors appear to facilitate recolonization as indicated by the appearance of several different seedlings that establish around the surviving trees. They appear to perform a probable mode of dispersal by acting as perches to birds that play a significant role in the dispersal of small seeds. In addition these surviving trees cast shade that limit the growth of ferns and grasses that otherwise limit the germination of tree saplings. There is no indication that the surviving trees act as seed sources as those seedlings are of totally of different species.
Application of assisted natural regeneration (ANR)As clearing eliminates the fern while enhancing theperformance of most tree seedlings suggests thatplanting trees to overcome dispersal limitations andproduce a shade cover is the best way to eliminate theferns.Once trees are established, they may act as regenerationnuclei by attracting seed dispersers and providingfavorable growing conditions, thereby acceleratingnatural regeneration.So application of assisted natural regeneration (ANR)offers efficient, low-cost forest restoration method thatcan effectively hastened regeneration of vegetation.
ConclusionThere are a several interacting factors that impose barriers forthe growth and survival of this seedling and arrest the naturalsuccession.The results of the study emphasize the predominant effect ofcompetition, effective seed dispersal (a combination ofdispersal and survival) and hydrological regime in affectingspecies composition and the seedling growth.It also highlights the need for management intervention inrestoring the peatland floristic diversity.Approach of overcoming the barriers to, and acceleratenatural successional processes are by removing or reducingthe barriers: - competition with weedy species, manipulationof tree stands and addressing the recurrence of fire