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Ecuador Regeneration Of Natural Landslides  (Ohl Y Bussman Citado)

Ecuador Regeneration Of Natural Landslides (Ohl Y Bussman Citado)



en mis estudios de gestión ambiental

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    Ecuador Regeneration Of Natural Landslides  (Ohl Y Bussman Citado) Ecuador Regeneration Of Natural Landslides (Ohl Y Bussman Citado) Document Transcript

    • Feddes Repertorium 115 (2004) 3 – 4 , 248 – 264 DOI: 10.1002/fedr.200311041 Weinheim, August 2004 Martin-Luther-University Halle-Wittenberg, Institute of Geobotany and Botanical Garden, Halle (Saale) University of Hawai’i Manoa, Institute of Botany, Honolulu C. OHL & R. BUSSMANN Recolonisation of natural landslides in tropical mountain forests of Southern Ecuador With 2 Map; 4 Figures and 2 Tables Summary Zusammenfassung The regeneration of the vegetation of natural land- Rekolonisation auf natürlichen Hangrutschun- slides was studied at Estación Científica San Fran- gen in tropischen Bergwäldern Südecuadors cisco (ECSF) in a tropical mountain forest area of Southern Ecuador, north of Podocarpus National Park. Im tropischen Bergwald Südecuadors (nördlich des The study focused on the process of regeneration on Podocarpus Nationalparks im Gebiet der Estación natural landslides and the vegetation change along an Científica San Francisco, ECSF) wurden Artenzu- altitudinal gradient using space-for-time substitution. sammensetzung und Rekolonisationsprozesse früher The most important plant families present on the Sukzessionsstadien entlang eines Höhengradienten landslides during the first stages of succession are auf natürlichen Hangrutschungen untersucht. Gleicheniaceae (Pteridophyta), Melastomataceae, Eri- Besonders Gleicheniaceae, Melastomataceae, Eri- caceae and Orchidaceae. Species of the genus Stiche- caceae und Orchidaceae sind von Bedeutung. Arten rus (Gleicheniaceae) are dominant, and species com- der Gattung Sticherus (Gleicheniaceae) sind sehr position varies with altitude and soil conditions. zahlreich vertreten. Die Artenzusammensetzung wech- Colonisation of landslides is not homogeneous. Zones selt entlang des Höhengradienten und in Abhängigkeit with bare ground, sparsely vegetated patches and von den Bodenbedingungen. Die mosaikartige Vertei- densely covered areas may be present within the same lung der Vegetation auf den Rutschungen (gänzlich slide. This small scale spatial heterogeneity is often unbedeckte bis stark überwucherte Zonen) ist auf created by local ongoing sliding processes and differ- häufige lokale Nachrutschungen sowie auf unter- ent distances towards undisturbed areas. Therefore, schiedliche Geschwindigkeiten der Wiederbesiedlung the duration of the successional process is highly entsprechend der Distanz zu ungestörter Vegetation variable. The initial stage of the succession is a com- zurückzuführen. Die Dauer der Sukzession ist daher munity of non vascular plants interspersed with scat- sehr variabel. Das Initialstadium wird von Moosen tered individuals of vascular plants. By means of und Flechten gebildet. Im weiteren Verlauf führt die runner-shoots they form vegetation patches which überwiegend vegetative Ausbreitung einzelner Gefäß- start growing into each other. The second stage is pflanzen zum zweiten Sukzessionsstadium. Dieses ist dominated by Gleicheniaceae (species composition durch die Dominanz von Gleicheniaceae gekenn- varying in altitude and soil chemistry). In the third zeichnet, während im dritten Stadium im Schutze der stage, bushes and trees colonise, sheltered by the Farne erste Büsche und Bäume heranwachsen und den ferns, and a secondary forest develops with pioneer Pionierwald bilden. Da diese Arten nicht im Primär- species that are not found in the primary forest vegeta- wald vertreten sind, kommt es regional zu einer be- tion. The common phenomenon of the natural land- trächtlichen Erhöhung der Artenzahl und der struktu- slides leads to an increase in structural and species rellen Diversität. diversity on a regional scale. Introduction of roads and catastrophic events burying houses or even villages are common. Such slides, Landslides are extremely frequent in the tropi- however, are usually initiated by human im- cal mountain regions of Ecuador. Destruction pact; most often by construction projects weak- © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 0014-8962/04/3-408-0248 2041275 Feddes Repertorium 3-4/2004 FED0681u.doc WinXP: Patrick Ahlemann/Pfü. /Sch. Beitrag: 5 Diskettenartikel
    • C. OHL & R. BUSSMANN: Recolonisation of natural landslides in tropical mountain forests 249 Fig. 1 View of the research area. Note the high number of natural landslides ening the underground and by deforestation In the present study natural slides in Ecua- accelerating erosion. At some distance from dor were analysed for vegetation characteristics roadsides and settlements, dense forests still during regeneration, species composition at exist. Even in these untouched areas, landslides different altitudes, succession and the role of are a very common phenomenon (Fig. 1). Such landslides for the biodiversity at the landscape natural slides are usually of smaller size than level. the anthropogenic slides. Little vegetation research has been done on landslides. Research on the regeneration of the Study area plant cover of a single landslide in Northern Ecuador was carried out by STERN (1995). The research was done in the easternmost KESSLER (1999) studied succession on land- mountain chain (Cordillera de Consuelo) in the slides in Bolivia, and ERICKSON et al. (1989) in Southern Ecuadorian Andes (Cordillera de the central and southern Andes. In other tropi- Numbala). The study area is part of the biologi- cal mountain areas species colonisation on cal reserve “Estación Científica San Fran- landslides was analysed by GARWOOD (1981 in cisco”. It is situated in the province Zamorra- Panama) and GUARIGUATA (1990 in Puerto Chinchipe (03°59′S, 79°04′W). Altitude ranges Rico) and geomorphological processes by from 1800 m up to 3150 m. The well-known BATARYA & VALDIYA (1989 in the Lesser Podocarpus National Park borders the south of Himalaya in India). KEEFER (1984) studied the site (Map 1). earthquake triggered landslides all over the The southern part of the Ecuadorian Andes world. is the lowest part of the Andes near the equator. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    • 250 Feddes Repert., Weinheim 115 (2004) 3 – 4 Map 1 The study site is located in southern Ecuador at the northern fringes of Podocarpus National Park between peak 3100 and ECSF (Estación Científica San Francisco) The substrate is built of pre-Creataceous to landslides in the research area are predomi- Tertiary material (HALL 1977; CLAPPERTON nantly caused by steep relief, long and heavy 1986). The geology of the study area varies. rainfalls, occasional earthquakes and a sub- Strongly weathered clay to sand stones are strate consisting mainly of highly weathered common while phyllitic slates are abundant in clay-stone; ideal conditions for the heavy wa- the lowest areas (ZECH & WILCKE 1999, own ter-logged organic layer to slip down. Roots obs.). The soils are mainly Aquic and Oxaquic rarely penetrate down to the mineral soil, and Dystropepts (SCHRUMPF et al. 2001). subsequently do not prevent the upper layers The precipitation regime is bimodal as in from sliding. the larger part of the Ecuadorian Andes. One The flora of Ecuador consists of approxi- peak of high rainfall occurs from February to mately 16000– 20000 species of vascular plants May and the other from October to December (GENTRY 1977; JØRGENSEN & ULLOA ULLOA (HOFSTEDE et al. 1998; BENDIX & LAUER 1994; JØRGENSEN & LEON-YANEZ 1999). 1992). The climate at 1950 m a.s.l. is semi- Given that Ecuador covers a relatively small humid with 10 humid months, has a mean tem- area, it is one of the most species-rich floras of perature of 15.5 °C and an annual precipitation the world. This richness is not equally distrib- of 2031 mm. Above 2200 m a.s.l. the climate is uted over the country. Only 10% of the coun- per-humid (EMCK, pers. comm.). The natural try’s surface falls into the altitudinal range of © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    • C. OHL & R. BUSSMANN: Recolonisation of natural landslides in tropical mountain forests 251 900 to 3000 m a.s.l but it is at this altitude 4 m2, as suggested by species area-curve analyses. where about 50% of the species and 39% of Each plot was photographed. the endemics are found (MADSEN & ØLLGAARD The cover of the floristic releves was estimated 1994). KESSLER (2002) counted 1138 endemic using the Londo scale (LONDO 1976). The vegetation table was sorted by hand and with the help of species in Ecuador at altitudes between 2500 TWINSPAN (HILL 1979) according to floristic and 3000 m. similarity (Table 1). The altitudinal zonation of the vegetation in The plots were sampled only once during the the study area is as follows: period between September and December 1999. The < 2100 m: Montane Broad-leaved Forest identification of plants was based on literature, and 2100–2700 m: Upper Montane forest or later compared to specimens in the “Herbario de la Ceja Andina Estacion Cientifica San Francisco”, the “Herbario de (2500–3100 m: Subalpine Elfin Forest or la Universidad Nacional de Loja” (Loja) and in the Yalca) “Herbario de la Pontifica Universidad Catolica” (QCA) in Quito. Angiosperm identification followed > 2700 m: Grass-Páramo, in wind-protected HUTCHINSON (1967), HARLING & SPARRE (1973– areas Shrub-Páramo. 2000), KELLER (1996), BRAKO & ZARUCHI (1993), The Montane Broad-leaved Forest is cha- MADSEN & ØLLGAARD (1993), ULLOA ULLOA & racterised by trees up to 30 m high, not exceed- JØRGENSEN (1993) and GENTRY (1996). Ferns have ing this height at exposed sites. Epiphytes, been identified according to the publications of especially ferns, Bromeliads and Orchids are TRYON & STOLZE (1989–1993), MACBRIDE (1930– highly abundant. Important taxa are Lauraceae 1970), ØSTERGAARD (1995) and ØLLGAARD (1979). (Ocotea, Nectandra, Persea), Melastomataceae Non vascular plants were not identified. Nomencla- ture of higher plants follows JØRGENSEN & LEON- (Miconia) and Rubiaceae (Psychotria, Pali- YANEZ (1999). Taxa missing in this work are named courea) (BUSSMANN 2001). The canopy is very according to the QCA specimens. dense and therefore herbal plants near the The collection of environmental data included ground are less common than at higher alti- soil texture of the upper mineral layer, and the soil tudes. Philodendron (Araceae) and Cyat- pH. The depth of the humus layer was measured as heaceae dominate the shrub layer. an important indicator of successional age and ongo- The vegetation composition of the Upper ing erosion. The inclination and position on the slide Montane Forest and the transition towards the was recorded as well as the altitude above sea level, Yalca vegetation was studied in 1999 and 2000 the direction aspect and the geographical position of the landslide. by HOMANN. The zone up to about 2400 m is Space-for-time substitution (PICKETT 1989) was dominated by Purdiaea nutans (Cyrillaceae), a employed to describe successional processes of stunted growing tree, and Guzmannia vanvolx- initial stages. Knowledge about the history of the emii (a terrestrial Bromeliaceae) building a slides can be gained by studying the aerial pictures dense ground-covering layer. Occasionally the of the region from 1962, 1976, 1989 (Instituto latter is replaced by Neurolepis elata (Poaceae). Geographico Militar, Quito) and 1998. However, the Other important taxa include Clusiaceae, Me- time since the last major sliding event for the plots lastomataceae and the genus Schefflera (Ara- could not be assessed accurately because most of the liaceae). Above 2400 m Purdiaea nutans landslide material is not displaced by one big event but by several consecutive slides. This type of land- becomes less important while species of Melas- slide has been called “ongoing slide” by STOYAN tomataceae become more abundant. Trees are (2000). Further on, many of the slides were invisible between 5 and 10 meters high. In wind-exposed at the aerial pictures due to their small size and the positions paramos occur as low down as steep relief. Therefore, the vegetation table was 2700 m a.s.l. organised according to their number of strata, in- creasing vegetation cover and height (Table 2). In this way the successional sequence can be inferred Methods but not their duration. Patterns of succession in the early to intermediate stages were investigated in this 23 landslides were selected between 2000 m and study; however there are no samples in the late 2700 m a.s.l. Selection criteria were: accessibility, successional stage. This is due to the logistical prob- aspect and altitude. On each selected slide between 2 lem of finding well-grown slides, as they are invisi- and 5 plots in homogenous zones were chosen for ble in aerial pictures and hard to find by walking the vegetation survey. The plot size was generally through the steep and dissected terrain. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    • 252 Feddes Repert., Weinheim 115 (2004) 3 – 4 Table 1 Vegetation types of landslides – frequency table, reduced to common and diagnostic species Sticherus rubiginosus- Sticherus revolutus types type variant with variant with Sticherus Sticherus bifidus melanoblastus number of plots 13 31 32 Average altitude in m a.s.l. 2030 2290 2480 Sticherus rubiginosus V I I Elleanthus aurantiacus IV I II Diplopterygium bancroftii III I Sticherus arachnoideus II Isachne cf rigens II Andropogon bicornis II Ageratina dendroides II Munnozia senecionidis II I Sticherus bifidus I IV Purdiaea nutans II I Graffenrieda harlingii II I Sticherus melanoblastus IV Viola stipularis III Rhynchospora cf macrochaeta II Sticherus revolutus I V V Bejaria aestuans I V III Blechnum sp. I III V Brachyotum campanulare II II Disterigma acuminatum II II Baccharis genistelloides IV V V Lycopodiella glaucescens III V V Tibouchina lepidota III III III Pitcairnea trianae II III IV Lophosoria quadripinnata II IV III Rhynchospora cf vulcani II III III Cortaderia bifida I II II Results Gleicheniaceae, of which nine species of Glei- cheniaceae were found. The genus Sticherus is Floristic Composition the most important with seven species. 146 species of more than 40 families grew on Vegetation: altitudinal the studied sites. 22 species belong to the Pteri- and edaphic differentiation dophyta. Families with ten or more representa- tives in the data set are the Melastomataceae, Two major groups are recognisable in the vege- Orchidaceae, Ericaceae, Asteraceae and Glei- tation table classified according to floristic cheniaceae (Pteridophyta). Poaceae, Bromeli- similarity (Table 1). One is dominated by aceae and Rubiaceae are frequently found, too. Sticherus rubiginosus (Gleicheniaceae) while 56 species were recorded only once. 75% of Sticherus revolutus (Gleicheniaceae) is com- the total cover of vascular plants is composed mon in the other. The second group is clearly of different species of Pteridophyta especially divided into two sub-clusters. The first is char- © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    • C. OHL & R. BUSSMANN: Recolonisation of natural landslides in tropical mountain forests 253 acterised by Sticherus bifidus (Gleicheniaceae), already on first stage sites points to an ad- the second by Sticherus melanoblastus (Glei- vanced age of at least 5 to 10 years (for exam- cheniaceae). ple Tibouchina lepidota, Vismia tomentosa or Other species are frequently occurring all Bejaria aestuans in plot 5, 12, 15, and 16). The over the studied plots. These include Baccharis second stage (Fig. 4) develops with the exten- genistelloides (Asteraceae) and Lycopodiella sion of the scattered plant individuals and glaucescens (Lycopodiaceae). ramets that established in the first stage of Altitude is a major factor influencing the succession using vegetative propagation, espe- species composition of the landslides. Fig. 2 cially Gleicheniaceae (see upper left corner of demonstrates the change of dominance of spe- Fig. 3) and Lycopodiaceae. Lycopodiella cies of Gleicheniaceae at different altitudes. At glaucescens and Lycopodium clavatum spread low altitudes Sticherus rubiginosus dominates. more quickly than the Gleicheniaceae with long At higher slides it is replaced by Sticherus looping runner-shoots but build stands of less revolutus accompanied by Sticherus bifidus or density (8, 10, 17, 19, or 27). Locally Viola Sticherus melanoblastus. The latter species stipularis spreads successfully using runner were never recorded both at the same slide. The shoots (plots 4, 20 and 21). The species compo- landslides colonised by Sticherus bifidus (slide sition seems to be random up to the point when 3, 4, 5, 6, 7, 8, 9, 10 and 22) and Sticherus the patches meet and competitive effects occur. melanoblastus (slide 19, 20, 21 and 23) are The month of October 1999 was a period of located on different mountain ridges (Map 2). extremely dry weather conditions. Locally, This shows that another environmental factor entire populations of Lycopodiella or Sticherus overlapping with the change in altitude is re- vanished suddenly (leaving patches of dead sponsible for this vegetation change. Slightly above ground plant material) probably as a different pH-values and a different percentage result of competition for water between the of exchangeable Ca2+ (VALLADAREZ, pers. individuals, ramets and species. The second comm.; ZECH et al. 2000) are characteristic for stage vegetation is made up by dense covers of the different ridges. Sticherus and Lycopodiaceae. Sticherus rubigi- nosus does not seem to have serious opponents at slides 1, 2, 11 and 12. Sticherus bifidus and Vegetation: time factor Lycopodiella tend to take over the dominant Table 2 shows a chronosequence of three suc- role at slides 3 – 10. Sticherus revolutus pre- cessional stages. The first stage (Fig. 3) is ra- vails at slide 22 and Sticherus melanoblastus ther similar at all altitudes with mosses and and Sticherus revolutus at slides 19– 21, 23 lichens covering the ground. The percentage and 13 – 18. The dominant role of Lycopo- cover of the layer of lichens and mosses is diella glaucescens vanishes usually with in- highly dependent on the soil and water condi- creasing total vegetation coverage (plots 59, 70, tions at a very small spatial scale and therefore or 75). not useful as an indicator for succession. A few Some species are equally present in early scattered vascular plants establish themselves. and later stages but never become dominant. The duration of this stage is highly variable Rhynchospora cf. vulcanii for example builds depending on the erosion of the site. The areas tufts and resists against the dominant species in in the first stage of succession on the slides are low numbers from the first stage to the end of freshly slipped parts, rocky parts, ever-eroding the second (plots 3, 11, 27, 38, or 70). Baccha- slopes or ever-accumulating zones with little ris genistelloides does not build dense colonies, inclination. Only some robust and runner-shoot and due to its straight and narrow growth form, building species can cope with strong erosion. percentage cover is usually very low but there In particular Baccharis genistelloides (As- are some plots where it is of greater importance teraceae) and Lycopodaceae are found. (plots 31, 43, 45, or 67). Seedlings of bushes The duration of the first or early second like Tibouchina lepidota, Graffenrieda harlin- stage is quite impossible to estimated, as ongo- gii (both Melastomataceae) or Bejaria aestuans ing erosion disturbs the successional sequence. (Ericaceae) are frequently found under dense The occasional presence of lignified plants layers of Sticherus in the first herbal layer. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    • 254 Feddes Repert., Weinheim 115 (2004) 3 – 4 100 Sticherus rubiginosus dominance in % 80 60 40 20 0 100 Sticherus revolutus dominance in % 80 60 40 20 0 100 Sticherus bifidus dominance in % 80 60 40 20 0 100 Sticherus melanoblastus dominance in % 80 60 40 20 0 1900 2000 2100 2200 2300 2400 2500 2600 2700 2800 2900 altitude in m a.s.l. Fig. 2 Altitudinal preference of some common Gleicheniaceae species on revegetating landslide plots Usually, these species are not found in primary undecomposed organic matter are very thick forest but form the pioneer forests. Seedlings of (plots 49, 50, and 51). The shady edges of the Purdiaea nutans (Cyrillaceae), the dominant slides are dominated by either Sticherus arach- species in the upper primary forest, may be noideus, or St. tomentosus. The woody plants found but apparently never mature to shrubs or Ageratina dendroides (Asteraceae), Munnozia trees in any of the early successional stages senecionidis (Asteraceae) and Liabum kingii (plots 17 or 29). (Asteraceae) are present. The third stage: Vegetation development at At the Sticherus melanoblastus or St. bifi- the Sticherus rubiginosus-dominated sites does dus dominated sites Cortaderia bifida (Poa- not show great variability. High stands of St. ceae) climbs with long, looping runner-shoots rubiginosus are covered with climbing Diplop- through the dense layer, hardly ever touching terygium bancroftii (plots 48, 49, or 50) which the ground (59, 64, 65, or 71). In the upper may locally dominate (plot 51); the mats of strata Tibouchina lepidota (Melastomataceae) © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    • C. OHL & R. BUSSMANN: Recolonisation of natural landslides in tropical mountain forests 255 Map 2 Position of the investigated landslides in the area. The landslides are aligned along three different mountain ridges and other species build bushes or small trees. like, varying between about 30° and 80°. This The fern Lophosoria quadripinnata (Lopho- leads to different erosive forces at different soriaceae) grows up to 2 meters in height (plot parts of the slide. Nevertheless, a direct correla- 59). tion between vegetation cover and inclination or erosive energy would only partly account for the distribution of the vegetation. The study of Discussion soil cores of the slides under more, and less, dense vegetation did not produce results with The first remarkable thing we noted when we significant differences in regard to soil texture, were climbing around the landslides, was the structure, colour and pH. This excludes the ‘patchy’ distribution of vegetation. What is the edaphic conditions as principal responsible reason for this? The slides are very similar in factors. shape, being long and narrow, although they Landslide areas are colonised quickly either vary in size. The surface is smooth and very at the borders of the slide or around islands that few rocks are present. Inclination changes step- slipped down without being overturned due to © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    • 256 Feddes Repert., Weinheim 115 (2004) 3 – 4 © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    • C. OHL & R. BUSSMANN: Recolonisation of natural landslides in tropical mountain forests 257 © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    • 258 Feddes Repert., Weinheim 115 (2004) 3 – 4 © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    • C. OHL & R. BUSSMANN: Recolonisation of natural landslides in tropical mountain forests 259 © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    • 260 Feddes Repert., Weinheim 115 (2004) 3 – 4 Fig. 3 Aspect of a plot in late first stage. Sticherus bifidus is spreading in the upper left corner (scale on the right = 2 m) vegetative propagation from the undisturbed established themselves after a few months. In neighbouring areas and possibly due to a fa- contrast, a landslide exposed to wind and direct vourable microclimate. Other patches of high sunlight was bare of any vegetation about eight vegetation cover are created by the clonal, months after the slide event. looping runner-shoot building growth of most Differences in vegetation along the altitudi- of the individual pioneers that managed to nal gradient have been found. The main flo- establish seedlings first (Gleicheniaceae, Lyco- ristic change occurs at an elevation of about podiaceae and Ericaceae). 2100 m. This altitude corresponds to the chan- The majority of the abundant species are ge in the vegetation zonation in the surrounding wind-dispersed and produce many seeds. The forests: from the Montane Broad-leaved Forest only frequent Angiosperm is Baccharis genis- to the Upper Montane Forest (BUSSMANN telloides (Asteraceae) which flowers all year 2001). On the landslides at higher altitudes round, so fruits are permanently available. some species typical for paramo vegetation are Under certain conditions freshly slipped found (Paepalanthus meridensis – Eriocaula- slides do not last very long in the first stage and ceae or Xyris subulata – Xyridaceae). Other lichens and mosses do not develop well as the distribution patterns do not correspond to vege- colonisation by higher plants starts already in tation changes along the altitudinal gradient but the first year of succession. In addition to the show similar patterns to differences in soil 23 landslides studied in detail some sites of chemistry. An explanation of the allopatric very recent origin were examined. On land- distribution of Sticherus bifidus and St. mela- slides well protected against wind and direct noblastus by the altitudinal gradient alone is sunlight, seedlings of the surrounding flora not possible, while the difference in altitude is © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    • C. OHL & R. BUSSMANN: Recolonisation of natural landslides in tropical mountain forests 261 Fig. 4 Early stage 2, dominant species are Sticherus bifidus and Lycopodiella glaucescens too small and no transition zone with the pre- compares the effect of landslides to the mean- sence of both species was found. Contrarily, as dering rivers of the lowland ecosystems. They described in the results, the influence of differ- create secondary forests dominated by colonis- ent soil chemistry combined with the influence ing species which are not able to survive in of changing altitude would offer an explana- mature stands. tion. Slightly different pH-values and a differ- In this work species richness during the first ent percentage of exchangeable Ca2+ (ZECH et al. two stages of regeneration is low due to the 2000) are characteristic for the different ridges. dominance of a few species of ferns. However, The amount of Ca2+ correlates negatively with during the third stage of succession, species the abundance of Al3+-ions which are toxic to composition still differs somewhat completely plants and could therefore be responsible for to the surrounding forest, but diversity is high. the differences in floristic composition (LAN- The second stage with a dense cover of DON 1991; ZECH & WILCKE 1999; WILCKE, Gleicheniaceae has not been described from pers. comm.). Correlations to other factors northern Ecuador (STERN 1995) but it was which could be responsible for the vegetation found on landslides in Bolivia (KESSLER 1999). change such as aspect were not found. There, the role of Gleicheniaceae seems simi- Landslides are a common phenomenon in lar. Diplopterygium bancroftii and species of most tropical mountain systems. STERN (1995) Sticherus dominate. In contrast, STERN (1995) and KESSLER (1999) hypothesised that landsli- found a dominant species of Chusquea, 3 ½ des maintain species diversity. STERN (1995) years after the slide event at the lower zone of a © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    • 262 Feddes Repert., Weinheim 115 (2004) 3 – 4 landslide. She adds that the presence of the gered slides along the roads? Studies on the bamboo is especially noteworthy because under regeneration of the latter type of slides close to certain environmental conditions it can grow the research area have been carried out by quickly and aggressively. Further on, she desc- HARTIG (2000). These slides are usually very ribes the great density of the bamboo, thereby extensive. The surface is not smooth but often having a profoundly limiting effect on the es- rocky. Natural slides are mainly created by a tablishment of other plant species. The bamboo heavy organic layer slipping over the mineral occurred at sites with a reasonable upper layer soil. If thick mats of organic material become of organic debris. Other interesting differences water-logged due to long-lasting heavy rains, in her work are that species of the genus Equi- the weight of the material reaches a critical setum are important in the early stage and point when the adhesive strength gives in to Blechnum dominates locally. No species of gravity and a slide-event is initiated. The thres- Gleicheniaceae were found. Reasons for those hold in this area is very low as the adhesive variations might be found in the obvious differ- strength is low due to the slippery mineral soil ences in geological substrate (of quaternary and the lack of a well developed root-system in volcanic origin) and the lower humidity and the B-horizon which could help to fix the upper altitude of the site (1440 m). Gleicheniaceae do layers (own obs.; STERN 1995). The human not hinder the establishment of bushes, though triggered slides are usually initiated due to the the time period from when seedlings of bushes weakened geological underground and have appear to when they manage to break through more in common with rock-falls. Succession the fern layer, varies. Different types of succes- differs between the two types of slides. Grasses sional models seem to correspond to the rege- largely replace the Gleicheniaceae and build a neration processes at the slides studies by very dense layer often limiting the establish- STERN on one hand and on the other hand the ment of bush species. Succession seems to slides observed by KESSLER and the work on follow the inhibition model (CONNELL & SLA- hand. Following the division of successional TYER 1977; PICKETT et al. 1987). Especially the models according to CONNELL & SLATYER number of orchids is tremendous which leads (1977) and PICKETT et al. (1987) the model of to a very high diversity on man-made slides inhibition will have to be used to describe the (GROSS 1998). In contrast, there are not many situation in northern Ecuador as observed by species of orchids found at the natural slides STERN (1995). In contrast, the tolerance model but in the few areas with rocky relief they be- combined with the facilitation model could be come more abundant (see plot 21 or 48). used to describe the situation in Bolivia (KESS- The aerial pictures of the region show a LER) and southern Ecuador. Little change in very unequal distribution of the natural slides. species composition but mainly a change in One possible explanation for the clustered vegetation density or -height was observed due occurrence of the slides might be reached by to local erosive energy, time elapsed since the studying the direction of the geological struc- last destruction, depth of the organic layer or tures. If the layers are aligned parallel to the the distance towards densely covered sites. slope, the risk of a slide-event arises. Consider- Mosses and lichens are not only abundant dur- ing that on most of the slides the soil is not ing the first stage but also during the second dragged down to the C-horizon, this explana- and third stage (though we do not know if the tion is probably not of great significance, but species are similar) and Gleicheniaceae are locally this certainly encourages or deters a present in the second and third stage though sliding process. Probably, the heavy organic they loose importance as they are overgrown by soil layer is responsible for the majority of the bushes and trees of the pioneer forests. Up sliding processes. Under mature forest organic to this point, the model of tolerance seems to fit layers build up, but due to evaporation and while the missing of species of the primary transpiration they will not get heavily water- forests during the third stage follows the facili- logged. In contrast, comparable amounts of tation model. water do not transpire from senescent forest. A What is the main difference between the mosaic-like forest structure with younger and studied natural landslides and the human trig- older forest stages is described in KESSLER © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    • C. OHL & R. BUSSMANN: Recolonisation of natural landslides in tropical mountain forests 263 (1999) from the montane forest in the Bolivian BENDIX, J. & LAUER, W. 1992: Die Niederschlags- Andes. He observed irregularly formed and jahreszeiten in Ecuador und ihre klimadyna- spaced patches of senescent forest with single mische Interpretation. – Erdkunde 46: 118 – 134. trees having already collapsed. This could BRAKO, L. & ZARUCHI, J. L. 1993: Catalogue of the flowering plants and Gymnosperms of Peru. – explain the clustered occurrence of landslides Monographs in Systematic Botany 45. as the risk of slipping in zones of senescent BUSSMANN, R. 2001: The montane forests of forest is higher than in zones of mature forest. Reserva Biológica San Francisco. – Die Erde In this case the effect of landslides in the eco- 132: 9 – 25. system would be very important for the natural CLAPPERTON, C. M. 1986: Glacial Geomorphology, regeneration of the system. At altitudes above Quaternary glacial sequence and palaeoclimatic 2100 m, especially under senescent forest, very inferences in the Ecuadorian Andes: 843 – 870. – dense layers of terrestrial Bromeliads are In: V. GARDINER (ed.), Proceed. Intern. Conf. found. Germination of other species is very Geomorphology II. – Cluchester. CONNELL, J. H. & SLATYER, R. O. 1977: Mechanisms difficult under these circumstances. In contrast, of succession in natural communities and their a landslide provides light and a high availabil- role in community stability and organization. – ity of minerals for successful plant growth. Am. Nat. 111: 1119 – 1144. There are still plenty of open questions DE NONI, G.; VIENNOT, M. & TRIJILLO, G. 1989– concerning the governing factors and the pro- 1990: Mesures de l‘erosion dans les Andes de cesses going on at landslides in the research l‘Equateur. – Cahier ORSTOM, Serie Pedologie area. Further research will have to deal in parti- 25(1–2): 183 – 196. cular with the influence of the soil chemistry on ERICKSON, G. E.; RAMIREZ, C. F.; CONCHA, J. F.; TISNADO, M. G. & URQUIDI, B. F. 1989: Land- species composition and succession and the slide hazards in the central and southern Andes: development of the pioneer forests towards the 111 – 117. – In: E. E. BRABB & B. L. HARROLD climax stage. (eds.), Landslides: extend and economic signi- ficance. – Rotterdam. Acknowledgements GARWOOD, N. C. 1981: Earthquake-caused land- slides in Panama: recovery of the vegetation. – We would like to express our cordial thanks to Res. Rep. Natl. Geogr. Soc. 21: 181 – 184. Prof. Dr. Ankea Sieg l and Prof. Dr. Ulrich GENTRY, A. H. 1977: Endangered plant species and Deil for helpful discussions and revisions habitats of Ecuador and Amazonian Peru: 136 – concerning this work and our Ecuadorian coun- 149. – In: G. T. PRANCE & T. S. ELIAS (eds.), terparts of the Universidad Nacionál Loja Extinction is forever. – The New York Botanical Garden, New York. (Ing. N. Mald o nad o , Ing. W. Ap lo , Dr. L. GENTRY, A. H. 1996: A field guide to the families L o ján), Herbario Reinaldo Espinosa Loja and genera of woody plants of north-west South (Ing. Z. Agu ir r e, Ego. B. Mer in o , Dra. B. America (Colombia, Ecuador, Peru) with supple- K l i t g a a r d ), the herbaria QCA y QCNE in mentary notes on herbaceous taxa. – Chicago, Quito, and ECSF, for all their collegial help at London. all times throughout the study. We thank INE- GROSS, A. 1998: Terrestrische Orchideen einer FAN for the research permit (now Ministerio Hangrutschung im Bergwald Süd-Ecuadors: Ver- de Medio Ambiente de Ecuador; no. 16-IC teilung, Phytomasse, Phänologie und Blüten- merkmale. – Univ. Ulm, Diploma Thesis, INEFAN DNAN VS/VS). We would also like unpubl. to thank the Deutsche Forschungsgemeinschaft GUARIGUATA, M. R. 1990: Landslide disturbance and for financing the project (DFG, Be 473/28-1, forest regeneration in the upper Luquillo Bu 886/1-1/2). Mountains of Puerto Rico. – J. Ecol. 78: 814 – 832. HALL, M. 1977: El volcanismo en el Ecuador. – Biblioteca Ecuador. – Quito. References HARLING, G. & SPARRE, B. 1973 – 2000: Flora of Ecuador. – Bot. Mus., Copenhagen. BATARYA, S. K. & VALDIYA, K. S. 1989: Landslides HARTIG, K. 2000: Pflanzensoziologische Untersu- and erosion in the catchment of the Gaula River, chungen von anthropogen gestörten Flächen im Kumaun Lesser Himalaya, India. – Mountain tropischen Bergwald Südecuadors. – Univ. Research and Development 9(4): 405 – 419. Bayreuth, Diploma Thesis, unpubl. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
    • 264 Feddes Repert., Weinheim 115 (2004) 3 – 4 HILL, M. O. 1979: TWINSPAN – a FORTRAN PICKETT, S. T. A. 1989: Space-for-time substitution program for arranging multivariate data in an as an alternative to long-term studies: 110 – 135. ordered two-way table by classification of the – In: G. E. LIKENS (ed.), Long-term studies in individuals and attributes. – New York. ecology. – New York. HOFSTEDE, R.; LIPS, J.; JONGSMA, W. & SEVINK, Y. PICKETT, S. T. A.; COLLINS, S. L. & ARMESTO, J. J. 1998: Geografia, ecologia y forestacion de la 1987: Models, mechanisms and pathways of sierra alta del Ecuador. Revision de literatura. – succession. – Bot. Rev. 53: 335 – 371. ABYA-YALA, Quito. SCHRUMPF, M.; GUGGENBERGER, G.; VALAREZO, C. HUTCHINSON, J. 1967: Key to the families of & ZECH, W. 2001: Tropical montane rain forest flowering plants of the world. – Oxford. soils: development and nutrient status along an JØRGENSEN, P. M. & LEON-YANEZ, S. (eds.) 1999: altitudinal gradient in the south Ecuadorian Catalogue of the vascular plants of Ecuador. – Andes. – Die Erde 132: 43 – 59. Monographs in Systematic Botany from the STERN, M. J. 1995: Vegetation recovery on earth- Missouri Botanical Garden 75. – St Louis. quake-triggered landslide sites in the Ecuadorian JØRGENSEN, P. M. & ULLOA ULLOA, C. 1994: Seed Andes: 207 – 220. – In: S. P. CHURCHILL; H. plants of the high Andes of Ecuador – a check- BALSLEV; E. FORERO & J. L. LUTEYN (eds.), list. – Aarhus University (AAU) Reports 34. Biodiversity and conservation of neotropical KEEFER, D. K. 1984: Landslides caused by earth- montane forests. – New York. quakes. – Geol. Soc. Amer., Bull. 95: 406 – 421. STOYAN, R. 2000: Aktivität, Ursachen und Klassifi- KELLER, R. 1996: Identification of tropical woody kation der Rutschungen in San Francisco/Süd- plants in the absence of flowers and fruits. – ecuador. – Univ. Erlangen, Diploma Thesis, un- Basel. publ.. KESSLER, M. 1999: Plant species richness and TRYON, R. M. & STOLZE, R. G. 1989 – 1993: Pterido- endemism during natural landslide succession in phyta of Peru I–V. – Fieldiana (Botany). N.S. – a perhumid montane forest in the Bolivian Chicago. Andes. – Ecotropica 5: 123 – 136. ULLOA ULLOA, C. & JØRGENSEN, P. M. 1993: Arbo- KESSLER, M. 2002: The elevational gradient of les y arbustos de los Andes del Ecuador. – Andean plant endemism: varying influences of Aarhus University (AAU) Reports 30. taxon-specific traits and topography at different ZECH, W. & WILCKE, W. 1999: Einfluß der Land- taxonomic levels. – J. Biogeogr. 29: 1159 – 1165. nutzung auf Bodeneigenschaften sowie auf die LANDON, J. R. (ed.) 1991: Booker tropical soil manu- Wasser- und Elementflüsse in Bergwäldern Süd- al. – Essex, New York. ecuadors. – Bericht zum bodenkundlichen Teil- LONDO, G. 1976: The decimal scale for releves of projekt des Projektverbunds „Ökosystemare permanent quadrats. – Vegetatio 33(1): 61 – 64. Kenngrössen gestörter und ungestörter tropischer MACBRIDE, J. F. (ed.) 1930 – 1970: Flora of Peru. – Bergwälder“. Zwischenbericht. – Univ. Bay- Chicago. reuth, unpubl. MADSEN, J. E. & ØLLGAARD, B. 1993: Inventario ZECH W.; WILCKE, W. & VALAREZO, C. 2000: In- preliminar de las especies vegetales en el Parque fluencia del uso de la tierra en los propiedades Nacional Podocarpus. – Ciencias agricolas de del suelo y en los flujos de aqua y de elementos la Universidad Nacional de Loja 22–23(1 – 2): en los bosques montanosos del Ecuador del sur. 66 – 87. Zwischenbericht. – Univ. Bayreuth, unpubl. MADSEN, J. E. & ØLLGAARD, B. 1994: Floristic com- position, structure, and dynamics of an upper montane rain forest in Southern Ecuador. – Nord. Addresses of the authors: J. Bot. 14: 403 – 423. Dr. Constanze O h l (corresp. author), Martin-Luther- ØLLGAARD, B. 1979: Lycopodium in Ecuador – ha- Universität Halle-Wittenberg, Institut für Geobotanik bits and habitats: 381 – 395. – In: K. LARSEN & und Botanischer Garten, Am Kirchtor 1, D-06108 L. B. HOLM-NIELSEN (eds.), Tropical botany. – Halle, Deutschland Proceed. sympos. Univ. Aarhus on 10–12 August e-mail: ohl@botanik.uni-halle.de 1978, organized on the occasion of the 50th Dr. R. B u s s m a n n , University of Hawai’i Manoa, anniversary of this university. – London. 3860 Manoa Road, Honolulu, Hawai’i, ØSTERGAARD, E. 1995: Gleicheniaceae – en gruppe bussmann@hawaii.edu, USA. pioner plantenblandt tropiske bregner. Afdeling for Systematik Botanik. Specialerapport marts 1995. – Biologisk Institut Aarhus Universitet, Manuscript received: September 29th, 2003/revised Aarhus. version: December 15th, 2003. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim