Short-term changes in tree populations in a tropical evergreen forest at Varagalaiar, Western Ghats, India

Within a 30-ha permanent plot of a tropical evergreen forest in the Anamalais, Indian Western Ghats, all the 13415 trees 30cmgbh (belonging to 153 species) were identified and tagged during 1997–1998. This communication reports the results of tree population changes based on two annual censuses (1999 and 2000) of the plot after the initial census, and compares the results with other tropical forest sites. One species, Ficus beddomei, disappeared from the plot and there was no new addition of species. Of the 96 species that showed changes in their population density, for 12 species recruitment and mortality matched. Tree recruitment (5 treesha^–1year^–1) exceeded mortality (4 treesha^–1year^–1) during the two-year period. Four modes of tree deaths were recorded in our site. The per cent mortality of trees differed between tree size classes during each recensus. The plot tree density increased progressively in the two-year period, indicating that shifts in species composition and density in natural forests, without major catastrophic disturbance, occur slowly.     

Landscape-level tree diversity assessment in tropical forests of southern Eastern Ghats,India

This large-scale, landscape-level study aims to assess tree species diversity, stem density and stand structure of six major tropical hill forests of southern Eastern Ghats, India, namely, Bodamalai (BM), Chitteri (CH), Kalrayan (KA), Kolli hills (KO), Pachaimalai (PM) and Shervarayan hills (SH). The Eastern Ghats of India is relatively under-studied compared with the Western Ghats biodiversity hotspot. The entire stretch of southern Eastern Ghats was divided into smaller grids of 6.25 km × 6.25 km, totaling to 120 grids. Within each grid, a belt transect of 0.5 ha (5 m × 1000 m) area was laid and all trees ≥30 cm girth at breast height (gbh) were enumerated. A total of 272 tree species (≥30 cm gbh) that belonged to 181 genera and 62 families were recorded in the total 60 ha area inventoried. Diversity indices such as Shannon, Simpson and Fisher's alpha indices were 2.44, 0.03 and 42.1, respectively, for the whole 60 ha area. One way ANOVA revealed that the species richness varied significantly across the six sites (F_(5,823) = 4.854, p < 0.0002). Also, the contribution of tree species to total species richness classified by three plant types viz. evergreen, brevi-deciduous and deciduous species varied significantly across the sites (One way ANOVA: F_(2,15) = 10.05, p < 0.002). Similarity indices such as Jaccard and Sørensen showed that sites CH and KA are more similar in terms of species composition. The total stand density and basal area for the total 60 ha area were 27,412 stems (457 stems ha⁻¹) and 1012.12 m² (16.9 m² ha⁻¹), respectively. The stand density and basal area for the six sites ranged from 290 (in site BM) to 527 stems ha⁻¹ (in site KA) and from 5.6 (in site BM) to 24.4 m² ha⁻¹ (in site KO), respectively. Stand density and basal area of tree species varied significantly across the six hill complexes (F_(5,823) = 4.85, p < 0.0002 and F_(5,823) = 2.71, p < 0.02, respectively). A positive correlation was obtained between stand density and species richness in sites PM (r_s = 0.65, p < 0.05) and SH (r_s = 0.67, p < 0.05), but not in other sites. The predominant tree species in the tropical forests of southern Eastern Ghats include Albizia amara, Euphorbia antiquorum, Canthium dicoccum var. dicoccum, Memecylon edule, Chloroxylon swietenia and Nothopegia heyneana. Taxonomically, Euphorbiaceae constituted the most diverse family with 25 species. Whereas, by tree abundance the Mimosaceae with 4126 stems enumerated from the 60 ha area formed the dominant family. Bray–Curtis cluster analysis, based on tree species composition and abundance revealed that the low-diverse site BM formed a separate entity from other hill complexes. This large-scale tree diversity inventory provides a baseline data for a variety of investigations and is expected to be useful for effective forest management and biodiversity conservation of southern Eastern Ghats region.     

Endemism and sexual systems in the evergreen tree flora of the Western Ghats, India

This study reports the endemism and sexual system in the wet evergreen tree flora of the Western Ghats. A total of 656 species from 66 families and 231 genera were listed. This included a gymnosperm family (Podocarpaceae) and a monocot family (Arecaceae). No family was endemic to the Western Ghats, but 352 species (53%) from 43 families and five genera were endemic. Nearly 35% of the families had no endemics. The largest families with endemics were Dipterocarpaceae (92%), Anacardiaceae (84%), Lauraceae (72%), Fabaceae, Rubiaceae and Myrtaceae (68%). The top five contributing families in the tree flora of the Western Ghats were Euphorbiaceae, Lauraceae, Rubiaceae, Myrtaceae and Annonaceae. The 656 species were largely hermaphrodites (57%) followed by dioecious (20%), polygamous (16%) and monoecious species (5%). The rate of dioecy reported in this study (20%) is higher than reports for Puerto Rico (18%) but lower than the Malaysian rainforest (26%). Structurally, like the Neotropical forests, most evergreen forest types of the Western Ghats could be classified into four ensembles. Yet, the Western Ghats had fewer species than other tropical and Neotropical forests. The proportion of endemics in the ensembles of the Western Ghats ranged from 34% (ensemble IV) to 14% (ensemble I).     

Occurrence of Gluconacetobacter diazotrophicus in tropical and subtropical plants of Western Ghats, India

Endophytic bacteria were isolated from the tissues of surface sterilized roots, stems, and leaves of fifty different crop plants. Phenotypic, biochemical tests and species-specific PCR assay permitted identification of four isolates of Gluconacetobacter diazotrophicus from root tissues of carrot (Daucus carota L.), raddish (Raphanus sativus L.), beetroot (Beta vulgaris L.) and coffee (Coffea arabica L.). Further the plant growth promoting traits such as nitrogenase activity, production of phytohormone indole acetic acid (IAA), phosphorus and zinc solubilization were assessed. Significant nitrogenase activity was recorded among the isolates and all the isolates produced IAA in the presence of tryptophan. Though all the four isolates efficiently solubilized phosphorus, the zinc solubilizing ability differed among the isolates.     

Plant diversity,structure and regeneration potential in tropical forests of Western Ghats,India

Diversity, stand structure and regeneration potential are the key elements of any forest ecosystem. For the present study, seven sites were selected with the aims of assessing plant diversity, structure and regeneration potential in tropical forests across Kanyakumari Wildlife Sanctuary (KWLS), Western Ghats, India. The sites were classified based on the similarity: tropical dry deciduous sites (TDDs I and II), tropical semi-evergreen sites (TSEs I and II) and tropical evergreen sites (TEFs I-III). The phytosociological survey was done by laying a total of 70 plots (10 plots in each study site). Standard methods were followed for the assessment of diversity, structure and regeneration patterns. A total of 267 species (205 genera, 70 families) were recorded. The tree species richness ranged 24 (TDD II) – 76 (TEF III). Of the vegetation spectrum, trees, vines and understorey accounted 56.5, 15.3 and 28.2% respectively to the total flora documented. A total of 66 species were endemic. The total tree density and tree basal area (seedlings, saplings, juveniles and adults) were 18,790 individuals (mean 2684) and 137.6 m² (mean 19.7 m²) in 70 plots respectively. The mean tree adult density and basal area ranged 370 (TDD I) – 900 (TEF I) individuals/ha and 24.2 (TDD I) – 75.3 (TEF III) m²/ha respectively. The overall species richness was highest in TDD I, but TEF III had the highest tree species richness. The diameter class-wise distribution showed the characteristic ‘reverse J-shaped’ curve. Most tree species were ‘newly recruited’. The dominant species had ‘fair’ to ‘good’ regeneration potential. However, 12 tree species showed ‘no’ regeneration. The overall regeneration pattern of trees was ‘good’, but ‘no’ or ‘poor’ regeneration patterns in some tree species, especially endemics is a point of concern. Since a majority of tree species were ‘new recruits’, species composition may likely change in the future. The results obtained would help in understanding diversity patterns, structural attributes and regeneration potential in tropical forests of protected areas for better forest management and conservation.     

Alpha diversity of lianas in a tropical evergreen forest in the Anamalais, Western Ghats, India

Abstract. Species richness, abundance, size-class distribution, climbing mode and spatial patterns of lianas were investigated in a 30-ha permanent plot of tropical evergreen forest at Varagalaiar in the Anamalais, Western Ghats, India. Each hectare was subdivided into 10 m × 10 m quadrats, in which all lianas ≥ 1 cm d.b.h. were measured, tagged and identified. The total liana density was 11, 200 individuals (373 ha–1) and species richness was 75 species, representing 66 genera and 37 families. The richness estimators employed for species and family accumulation curves after 100 times randomization of sample order, have stabilized the curves at 16th and 15th hectares, respectively. A greater proportion of lianas was twiners (55% of species and 44.4% of density) and root climbers (5% of species and 14% of density), and a few were tendril climbers, reflecting the late successional stage of the forest. In the size-class distribution, 82% of abundance and 97% of species richness fell within 1–3 cm diameter threshold. The dominance of succulent diaspore type signifies the faunal dependence of lianas on vertebrate frugivores for dispersal. The diversity, population density and family composition of lianas of our site is compared with those of other tropical forests. The need for biomonitoring of this synusia in the permanent plot for forest functioning is emphasized.     

Resource partitioning in sympatric langurs and macaques in tropical rainforests of the central Western Ghats, south India

In a competitive sympatric association, coexisting species may try to reduce interspecific interactions as well as competition for similar resources by several ecological and behavioral practices. We studied resource utilization of three sympatric primate species namely, lion-tailed macaques (Macaca silenus), bonnet macaques (M. radiata) and Hanuman langurs (Semnopithecus entellus) in a tropical rainforest of the central Western Ghats, south India. We studied resource use, tree-height use, foraging height, substrate use when consuming animal prey and interspecific interactions. The results revealed that across the year, there was very limited niche overlap in diet between each species-pair. Each primate species largely depended on different plant species or different plant parts and phenophases from shared plant species. Primate species used different heights for foraging, and the two macaque species searched different substrates when foraging on animal prey. We also recorded season-wise resource abundance for the resources shared by these three primate species. While there was low dietary overlap during the dry season (a period of relatively low resource abundance), there was high dietary overlap between the two macaque species during the wet season (a period of high resource abundance for the shared resources). We observed only a few interspecific interactions. None of these were agonistic, even during the period of high niche overlap. This suggests that the sympatric primate species in this region are characterized by little or no contest competition. Unlike in some other regions of the Western Ghats, the lack of interspecific feeding competition appears to allow these primates, especially the macaques, to remain sympatric year-round.     

Variation in bark thickness in a tropical forest community of Western Ghats in India

1. We examined the relation between bark thickness and girth in a large sample of trees from evergreen and semi-evergreen rain forest.
2. There is a significant tendency for bark thickness to increase with tree girth. Removing this tendency, we find a significant trend for species from more disturbed habitats to possess thicker bark.
3. Species from more disturbed habitats also have a greater propensity for secreting gums and resins.
4. Nine of the 29 species occurring in more than one habitat type and with a sample size of at least 11 individuals show a tendency for possession of a thicker bark by individuals in the more disturbed habitats.
5. We conclude that bark thickness and occurrence of gums and resins are physiognomic–structural attributes of value in characterizing tree communities created by different levels of disturbance.     

Attenuated tree species diversity in human-impacted tropical evergreen forest sites at Kolli hills, Eastern Ghats, India

Tree diversity (30 cm gbh) in undisturbed and human-impacted tropical evergreen forest sites was investigated in the Kolli hills, Eastern Ghats, India. Four 2-ha contiguous permanent plots were erected, one each in Perumakkai shola (site PS), Vengodai shola (VS), Kuzhivalavu shola (KS) and Mottukkadu shola (MS) at 1000, 1050, 1200 and 1250 m elevation, with increasing human disturbance, to evaluate the difference in tree species composition, stand structure and dynamics. This paper discusses the results of the first survey. A total of 3825 individuals and 78 species from 61 genera and 36 families were enumerated in the 8 ha area. Among the four 2-ha sites, species richness was greatest (58) in the undisturbed site PS and lowest (39) in the highly disturbed site MS. Shannon, Simpson, Hill diversity and evenness indexes revealed a progressive reduction in diversity with increasing disturbance. The asymptote species-area curves imply adequate site sampling. Tree density (1151 to 651 trees ha^–2) and basal area (106 to 46.6 m² ha^–2) decreased from undisturbed to disturbed site, due to selective felling. Single species, Memecylon umbellatum dominated sites MS (39%) and VS (26%), while Nothopegia heyneana, Memecylon umbellatum and Diospyros ovalifolia were dominant in PS, and Meliosma simplicifolia, Myristica dactyloides and Phoebe wightii in KS. Based on species abundance, we classify the study area as Memecylon–Phoebe–Beilschmiedia association with Neolitsea and Myristica as codominants. Tree population structure revealed a step-wise decline in girth frequencies with increasing size class in undisturbed site PS, whereas tree density fell sharp (>50%) in medium girth class in the disturbed site MS. Population of the dominant species varied widely. The diversity values of this inventory are compared with similar studies in India and other tropical forests. Evidently, the reduction in species richness (by 52%), basal area (56%) and tree density (58%) in disturbed sites, with 57.6% of species rarity of this tropical evergreen forest, in secluded patches (sholas) of Kolli hills, underlines conservation need to prevent species loss.     

Endophytic fungal communities in woody perennials of three tropical forest types of the Western Ghats,southern India

Fungal endophytes of tropical trees are expected to be exceptionally species rich as a consequence of high tree diversity in the tropics and the purported host restriction among the endophytes. Based on this premise, endophytes have been regarded as a focal group for estimating fungal numbers because their possible hyperdiverse nature would reflect significantly global fungal diversity. We present our consolidated ten-year work on 75 dicotyledonous tree hosts belonging to 33 families and growing in three different types of tropical forests of the NBR in the Western Ghats, southern India. We conclude that endophyte diversity in these forests is limited due to loose host affiliations among endophytes. Some endophytes have a wide host range and colonize taxonomically disparate hosts suggesting adaptations in them to counter a variety of defense chemicals in their hosts. Furthermore, such polyphagous endophytes dominate the endophyte assemblages of different tree hosts. Individual leaves may be densely colonized but only by a few endophyte species. It appears that the environment (the type of forest in this case) has a larger role in determining the endophyte assemblage of a plant host than the taxonomy of the host plant. Thus, different tropical plant communities have to be studied for their endophyte diversity to test the generalization that endophytes are hyperdiverse in the tropics, estimate their true species richness, and use them as a predictor group for more accurate assessment of global fungal diversity.     

Comparing tree diversity and composition in coffee farms and sacred forests in the Western Ghats of India

Expansion of coffee cultivation is one of the causes of deforestation and biodiversity loss. However, shade grown coffee has been promoted as a means for preserving biodiversity in the tropics. In this study we compared tree diversity in two types of coffee management regimes with the sacred groves in the Western Ghats of India. We computed species accumulation curves, species diversity indices and evenness indices to compare the different management regimes. Results of diversity indices showed that shade coffee had less diversity compared to sacred groves. Exotic species dominated the tree diversity in lands where the tree harvesting rights are with the growers. Native trees dominated the tree diversity when growers had no ownership rights on trees. A species accumulation curve suggested that the sacred grove had higher species richness compared to other two habitats. Lack of incentive to preserve endemic species as shade trees is forcing growers to plant more exotic species in shade grown coffee plots. If encouraged, shade grown coffee can preserve some biodiversity, but cannot provide all ecological benefits of a natural forest.     

Changes in rain forest tree diversity, dominance and rarity across a seasonality gradient in the Western Ghats, India

Aim We assessed the effects of latitude, altitude and climate on the alpha diversity of rain forest trees in the Western Ghats (WG) of India. We tested whether stem densities, dominance, the prevalence of rarity, and the proportion of understorey trees are significantly correlated with alpha diversity. Location The WG is a chain of mountains c. 1600 km in length, running parallel to the western coast of the Indian peninsula from above 8° N to almost 21° N latitude. Wet forests occur as a narrow strip in regions with heavy rainfall. Methods To assess tree diversity we used data from 40 small plots, < 1 ha in area, where all trees ≥ 3.18 cm d.b.h. had been inventoried. These plots were distributed across 7 latitudinal degrees and at elevations between 200 and 1550 m. Fisher's alpha was used as a measure of diversity. For each plot, the proportion of trees belonging to the understorey, the proportion of trees belonging to the most abundant species in the plot, as a measure of dominance, and the proportionate representation of singletons, as a measure of rarity, were estimated, and correlated with Fisher's alpha, elevation, rainfall and seasonality. Results Annual rainfall and seasonality increased towards the north, but were not significantly correlated. Tree diversity increased significantly with decreasing seasonality. Tree diversity was not significantly correlated with stem density or with the proportion of understorey tree species, but was significantly correlated with tree dominance and rarity. Dominance increased and rarity significantly decreased with increasing seasonality. Main conclusions This study demonstrates that seasonality influences rain forest tree diversity in the WG of India. The relationship between alpha diversity, dominance and rarity lends correlative support for the Janzen–Connell pest pressure hypothesis.     

Development of polymorphic microsatellite loci in Nothapodytes nimmoniana, a medicinally important tree from the Western Ghats, India

Nothapodytes nimmoniana is a medicinally important tree species that occur in the Western Ghats, a megadiversity hotspot in southern India. Inner stem bark of the tree contains an important anti-cancer alkaloid, camptothecin for which the natural population of the tree is heavily harvested. In this paper, we report the isolation and characterization of eight polymorphic microsatellite loci using enrichment hybridization protocol. Analysis of 36 individuals representing two populations revealed three to 12 alleles per locus. Observed heterozygosity ranged from 0.21 to 0.94 for the two populations. None of the loci tested showed linkage disequilibrium. These markers are invaluable for evaluating the genetic structure and assessing the genetic impacts of harvesting of N. nimmoniana in the Western Ghats to formulate strategies for conservation of the species.     

Forest resistance to drought in a humid tropical dipterocarp forest in the Western Ghats of India

Droughts are linked to tree die-offs in the biodiverse humid tropics. We assessed drought response of a Dipterocarp Forest and found a marginal decrease in tree survival, indicating drought resistance. Understory and emergent species were sensitive to drought. Urgent focus is needed to understand drought impacts and plant physiological responses in South Asian forests.     

Diversity and distribution of herbaceous vascular epiphytes in a tropical evergreen forest at Varagalaiar, Western Ghats, India

Herbaceous vascular epiphytes were screened in a total sample of 13 445 trees (in 153 species) and 348 lianas (in 30 species) 30 cm girth at breast height in a 30 ha plot of tropical evergreen forest at Varagalaiar, Indian Western Ghats. Of these, 4.3% of trees and 3.7% of lianas were infested with epiphytes. Epiphyte diversity totaled 26 species in 19 genera and 10 families. Sixteen species were angiosperms in three families (Orchidaceae 54%; Piperaceae and Araceae 8%) and 10 species (38%) were pteridophytes in seven families. The orchid, Pholidota pallida was most abundant and occurred on 178 (29.6%) stems. Asplenium nidus occurred on the maximum of 62 host species. The species richness estimators employed for species accumulation curves after 100 times randomization of sample order have stabilized the curve at 18th and 19th hectares respectively for Incidence-based Coverage Estimator and Chao2. A total of 588 trees and 13 liana stems lodged epiphytes, 74% of which were evergreen species and 26% deciduous. Epiphyte density was greater (56%) in deciduous species (Bischofia javanica 30% and Vitex altissima 8%). A significant positive relationship was found between trunk size and epiphyte association. Larger epiphyte species occurred mostly on middle and larger stems and smaller epiphyte species occurred on smaller stems. The majority of epiphytes (92%) were of autochorous dispersal type, bearing capsule or dust diaspores, while the remaining species with berries and nutlets are dispersed by small vertebrates.     

Tree species diversity and community composition in a human-dominated tropical forest of Western Ghats biodiversity hotspot,India

The structure, function, and ecosystem services of tropical forest depend on its species richness, diversity, dominance, and the patterns of changes in the assemblages of tree populations over time. Long-term data from permanent vegetation plots have yielded a wealth of data on the species diversity and dynamics of tree populations, but such studies have only rarely been undertaken in tropical forest landscapes that support large human populations. Thus, anthropogenic drivers and their impacts on species diversity and community structure of tropical forests are not well understood. Here we present data on species diversity, community composition, and regeneration status of tropical forests in a human-dominated landscape in the Western Ghats of southern India. Enumeration of 40 plots (50 m × 20 m) results a total of 106 species of trees, 76 species of saplings and 79 species of seedlings. Detrended Correspondence Analysis ordination of the tree populations yielded five dominant groups, along disturbance and altitudinal gradients on the first and second axes respectively. Abundant species of the area such as Albizia amara, Nothopegia racemosa and Pleiospermum alatum had relatively few individuals in recruiting size classes. Our data indicate probable replacement of rare, localized, and old-growth ‘specialists’ by disturbance-adapted generalists, if the degradation is continuing at the present scale.     

Assessing the potential for indirect interactions between tropical tree species via shared insect seed predators

Natural enemies of plants have the potential to influence the dynamics of plant populations and the structure of plant communities. In diverse tropical forests, research on the effects of plant enemies has largely focused on the diversity-enhancing effects of highly specialized enemies, while the community-level effects of enemies with broader diets have rarely been considered. We investigated the community of insect seed predators interacting with seven tree species in the family Lauraceae on Barro Colorado Island (Panama). We present one of the first quantitative food webs for pre-dispersal insect seed predators and their host plants, and use the information in the web to assess the potential for indirect interactions between the tree species. Our data suggest that there is high potential for indirect interactions between Lauraceae species via their shared seed predators. The strength and direction of these interactions are largely unrelated to the phylogenetic distance and trait similarity between species but are likely governed by the volume of fruit produced by each tree species.