Brewing trouble: coffee invasion in relation to edges and forest structure in tropical rainforest fragments of the Western Ghats, India

While the conservation impacts of invasive plant species on tropical biodiversity is widely recognised, little is known of the potential for cultivated crops turning invasive in tropical forest regions. In the Western Ghats biodiversity hotspot, India, fragmented rainforests often adjoin coffee plantations. This study in the Anamalai hills assessed the effects of distance from edges and forest structure on the occurrence and abundance of shade-tolerant coffee (Arabica Coffea arabica and Robusta C. canephora) in four fragments (32–200 ha) using replicate line transects laid from the edges into the interiors. The coffee species cultivated in adjoining plantations was more abundant than the other coffee species inside study fragments, showing a clear decline in stem density from edge (0 m) to interior (250 m), suggesting the influence of propagule pressure of adjoining plantations, coupled with edge effects and seed dispersal by animals. Significant positive correlations of coffee density with canopy cover indicate the potential threat of coffee invasion even in closed canopy rainforests. Stem density of Coffea arabica (150–1,825 stems/ha) was higher in more disturbed fragments, whereas Coffea canephora had spread in disturbed and undisturbed sites achieving much higher densities (6.3–11,486 stems/ha). In addition, a negative relationship between C. canephora and native shrub density indicates its potential detrimental effects on native plants.     

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.     

Effects of rainforest fragmentation and shade-coffee plantations on spider communities in the Western Ghats,India

Studies on the effects of tropical rainforest fragmentation and disturbance have often focussed on plants and vertebrates such as birds and mammals and seldom on invertebrates, despite the latter being among the most biologically diverse groups in these ecosystems. Spiders are one such group of invertebrate predators that are known to be sensitive indicators of environmental change in tropical ecosystems. The present study assesses the spider community structure and responses to rainforest fragmentation and degradation and conversion to shade-coffee plantations in the Anamalai hills, southern Western Ghats, India. Ten rainforest fragments ranging in size from 11 ha to 2,600 ha under varying levels of degradation within the Indira Gandhi Wildlife Sanctuary and private lands of the Valparai plateau, and two shade-coffee plantation sites were sampled for spiders using visual searches along time-constrained belt transects between January and May 2005. Within a total sampled area of 5.76 ha, 4,565 individual spiders (4,300 detections) belonging to 156 morphospecies within 21 families and 8 functional groups were recorded. The estimated total number of understorey spider species in the study area was 192 (±5.15 SD) species, representing around 13% of the total number of spider species so far described from India. Overall spider density, species richness, and species density showed no trend in relation to fragment area across all sites. Specific comparisons among undisturbed sites indicated however that high altitude sites had fewer species than mid-altitude sites and fragments had fewer species than relatively larger continuous forest sites. In contrast to the lack of trend in overall species richness and abundance, species composition changed substantially in relation to habitat alteration and altitude. Cluster analysis of Bray-Curtis similarities among sites in spider species composition revealed four distinct clusters: high altitude undisturbed sites, mid-altitude disturbed sites with an undisturbed mid altitude site, mid-altitude highly disturbed sites with a disturbed site, and shade-coffee plantation sites. Spider species, such as Psechrus torvus and Tylorida culta, that contributed significantly to the dissimilarity between undisturbed and disturbed rainforest sites, and rainforest and shade-coffee sites were identified that serve as useful indicators of habitat alteration.     

A field guide to the caecilians of the Western Ghats, India

Caecilians are legless amphibians quite characteristic of the Western Ghats. Fourteen out of 16 Indian species occur in the Western Ghats and all are endemic. The present paper deals with the biology of caecilians with reference to external morphology and general breeding behaviour. It consolidates information on 26 morphological parameters which are used in caecilian identification. Metric multidimensional scaling of 16 species of caecilians using pair-wise euclidian distances calculated on the basis of 11 important morphometric parameters clearly depicts morphological distances between different species and more so the genera, thereby validating the classification. A field guide has been developed for the identification of caecilians based on a survey made all over the Western Ghats, observation of holotypes at the Natural History Museum, London and review of the literature. The study also reveals the microhabitat requirements of the caecilians. Further, the localities of caecilian distribution in the Western Ghats are mapped. The taxonomy of Indian caecilians is discussed.     

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.     

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.     

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.     

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.     

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.     

Population dynamics of a group of lion-tailed macaques (Macaca silenus) inhabiting a rainforest fragment in the Western Ghats, India

We observed the overall population dynamics and number of births and deaths in identified individuals between January 2002 and October 2005, in a large group of lion-tailed macaques in the Anaimalai Hills of the Western Ghats in the south Indian state of Tamilnadu. The group inhabited an isolated rainforest fragment located inside a private tea/coffee garden. The group size increased from 56 in January 2002 to 84 in October 2005. All females reproduced, and the interbirth interval was 23.18 months. Of the 37 infants born between 2002 and 2005, only 1 died providing an infant survivorship rate of about 97.3%. Although births occurred in all months, most of the infants were born between February and March, and this pattern of births was consistent over the years, indicating a major birth peak in this species. The population growth rate in this unusually large group was found to be higher than even in those groups of lion-tailed macaques that inhabit large and relatively undisturbed rainforest complexes. This high growth rate could be attributed to the availability of abundant cultivated fruit plants including commercial crops such as coffee seeds. The observations provide a perspective for the management of other groups of this endangered species inhabiting rainforest fragments.     

Resource partitioning and interspecific interactions among sympatric rain forest arboreal mammals of the Western Ghats, India

Resource partitioning in a community of diurnal arboreal mammalsconsisting of the lion-tailed macaque Macaca silenus, bonnetmacaque (BM) Macaca radiata, Nilgiri langur Semnopithecus johnii,and the Indian giant squirrel Ratufa indica of the Western Ghats,southern India, was studied. Differences in their diet, verticalstratification, food resource niche breadth, niche overlap,and behavioral interactions were examined. Resource partitioningwas through differential habitat use, resource use, and verticalstratification. Of the four species, the BM was not a residentspecies and made frequent forays into evergreen forest fromthe adjacent deciduous forest during the flowering season ofCullenia exarillata and fruiting season of Ficus microcarpa.The macaques had narrower niches, and the langur and the squirrelhad wider niches. Niche overlap was highest between the twomacaques. Overlap among the study species was particularly pronouncedduring the flowering of C. exarillata. There was significantcorrelation between niche overlap and intolerance among thestudy species. Certain species pairs showed little or no mutualintolerance despite high overlap. Cooperative interactions suchas alarm calls occurred more frequently among the resident species.Interaction matrices revealed an underlying pattern of interspecificdominance hierarchy, with the BM dominating over the other threespecies. Our study suggests that the BM do not coexist withthe other three because of high overlap with its congener andlow occurrence of cooperative interactions.     

Assessing the utility of direct and indirect methods for estimating tropical tree age in the Western Ghats, India

The knowledge of tree age is important for understanding tree growth and forest dynamics. It may be estimated by ‘direct’ methods involving growth ring counts, or by ‘indirect’ methods involving field measurements of growth rates. Direct methods are considered more accurate, but it is not clear if they are appropriate for all species, notably from the humid tropics. In this paper we assess the occurrence of annual growth rings and their utility for age estimation in three tropical tree species, Acrocarpus fraxinifolius, Dalbergia latifolia (Fabaceae) and Syzygium cumini (Myrtaceae), growing in traditional shade coffee plantations of the southern Western Ghats, India. These species previously were described as having “indistinct or absent” growth rings. We used anatomical studies, field measurements and computational methods to characterise growth rings and assess similarities between directly and indirectly estimated tree ages. Our study revealed that annual growth rings were characterised by different sets of anatomical features per species and were most distinct in the fast-growing deciduous A. fraxinifolius. Growth rates measured in the field showed annual periodicity in all three species, and reflected annual rainfall-drought cycles in D. latifolia and S. cumini. Direct age estimates were most similar to indirect estimates in D. latifolia, and least so in S. cumini. The results of direct age estimation by counting rings are consistent with them being annual in nature in tropical species with distinct and reliable annual growth ring formation. However, for species with poorly defined growth rings, indirect age estimation methods might be more useful.     

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.     

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.     

A method for assessing evergreen habitats using phytodiversity and geospatial techniques in tropical rain forests of Southern Western Ghats (India)

We have used data generated using remote sensing and geographical information systems to categorize habitats, and then determined the relationship between the habitat categorizations and species-distribution patterns. A biologically rich hotspot—Kalakad-Mundanthurai Tiger Reserve, located at Southern Western Ghats, India, was chosen for this study. In order to spatially delineate areas of high species richness/diversity and endemic habitat zones, we have identified evergreen habitats in conjunction with landscape metrics, species assemblage, micro-habitats like slope, topography, species endemism, and proportion of core and edge species. A total of 236 species and 2,920 individuals were recorded using systematic stratified plots of 0.1 ha covering 47 plots. Hierarchical cluster analysis was done using Ward’s method. Plot information was used to identify clusters based on species density. The analysis showed five species assemblages that are quite distinct from each other in terms of dominant species. The distribution of endemic and edge species, land cover heterogeneity, and continuity of patches in these clusters were evaluated to understand the degree of disturbance and intactness at landscape scale. Integration of species assemblages and topography brought out four major elevation-slope complexes. Information on species composition (robust field survey) with spectral (hybrid classification) properties has shown 72% overall accuracy and distinguished four evergreen sub-groups and other land cover classes. The developed approach assumes great importance in the assessment of biodiversity and prioritizing the areas of conservation.     

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.