Biology subjects

Chanda, R.

Publications and source records attributed to Chanda, R..

4 recordsLinked to original sources

bioRxiv2023

Bird communities in a selectively logged tropical montane forest are dominated by small, low-elevation species

Tropical montane forests are critical centres of terrestrial biodiversity and endemism, and face a range of threats, including selective logging and climate change. However, few studies have explored the joint influence of these threats, particularly in tropical mountains, despite how crucial it is to understand the cumulative impact of forest loss and climate change on biodiversity. We used mist-netting and bird ringing data from a long-term (10-year) community and population monitoring program to examine how the composition of the mid-elevation Eastern Himalayan understorey bird community changed in the mid-elevation primary and logged forest. Because logged forest is warmer than primary forest, we hypothesised that the bird community would shift towards lower elevation species, with a faster transition in logged forest. Further, because logged forest has lower arthropod abundance, we hypothesised that the primary forest community would have larger species than the logged forest community. Our study shows that the bird community in the logged forest shifted towards lower-elevation species than in the primary forest (although this was not statistically significant). Moreover, we found that smaller species were better able to colonise warmer logged forest, whereas larger species reached higher densities in primary forest. These trends are likely to be driven by climate change causing upslope range shifts and logged forest selecting for species that are likely to tolerate the consequently altered abiotic (higher temperatures) and biotic (lower resources) environment. These findings have significant implications for understanding the impacts of forest loss and climate change on biodiversity, particularly in tropical montane forests.

ecology↗

bioRxiv2022

Patterns of secondary invasion in the understory of exotic, invasive timber stands

Current climate and land cover change threaten global mountaintops with increased spread of invasive species. Long-established plantations of exotic and invasive trees on these mountaintops can alter their surroundings, further increasing invader-facilitated or secondary invasion. Identifying the ecological conditions that promote such specific associations can help develop better management interventions. The Western Ghatss Shola Sky Islands (>1400m MSL) host vast stretches of exotic and invasive tree plantations that sustain colonisation of other invasive woody, herbaceous and fern species in their understories. Here we analysed vegetation and landscape variables from 232 systematically-placed plots in randomly selected grids using NMDS and Phi Coefficient approaches, to examine patterns of association (positive interactions) between secondary understory invasive species with specific exotic and invasive overstory species. We also conducted GLMM with zero inflation to determine the influence of environmental variables where such associations occur. We find that secondary invasion of multiple species under the canopy of other exotic invasives is widespread across the Shola Sky Islands. Stands of Eucalyptus host the colonisation of 70% of non-native invasive species surveyed across the Shola Sky Islands. In particular, Lantana camara invasion is strongly associated with Eucalyptus stands. We also found that climatic variables affect the colonisation of understorey woody invasive species, while invasion by exotic herbaceous species is associated with the density of road networks.. Canopy cover impacts all invasives negatively, while incidence of fire was negatively associated with invasion by Lantana spp and the Pteridium spp. While the restoration of natural habitats largely targets the highly invasive Acacia, less invasive Eucalyptus and Pine are often not included. Our study suggests that retaining such exotic species in natural habitats, particularly protected areas, can hinder ongoing restoration efforts by facilitating further invasions by multiple woody and herbaceous species.

ecology↗

bioRxiv2022

Abiotic niche predictors of long-term trends in body mass and survival of Eastern Himalayan birds

The synergistic impacts of climate change and habitat degradation threaten tropical species worldwide. However, how species abiotic niches affect their demographic vital rates and phenotypic changes under anthropogenic change remains poorly understood. Using an 11-year mark-recapture dataset from primary and selectively logged forest in the Eastern Himalayas, we investigated how temperature-humidity niche characteristics predicted body mass and survival trends in understorey insectivorous birds over time in each habitat. Our results show that logged forest is hotter and drier than primary forest, and the arthropod community shows dramatic shifts in composition upon selective logging. In understorey insectivores, the degree of dissimilarity between species-specific primary and logged forest niches was strongly and negatively correlated with survival and body mass trends in logged forest. Here, we show that temperature-humidity niche shifts in response to anthropogenic habitat modification can impact demographic vital rates and body condition crucial for population persistence. This work has the potential to inform prompt, targeted conservation efforts toward species that are the most threatened in a warmer and more degraded world.

ecology↗

bioRxiv2022

The effect of selective logging on microclimates, arthropod abundance and the foraging behaviour of Eastern Himalayan birds

1. Selective logging--the practice of removing a subset of commercially important trees from a forest--is a globally pervasive form of forest degradation. Selective logging alters both the structure and function of forests and the composition of ecological communities. 2. Tropical insectivorous birds are highly vulnerable to microhabitat alterations in logged forest. Such altered microhabitats might affect the foraging of forest birds by altering (a) resource availability, and (b) foraging behaviour. 3. We investigated the effect of selective logging on microclimates, prey availability, foraging behaviour and the foraging success of eastern Himalayan birds in the breeding season. 4. Selective logging alters temperature-humidity microclimates and the composition of arthropod communities, both of which are likely to then collectively alter foraging behaviour by birds. We show that birds spent a lower proportion of their time foraging in primary compared with logged forest. Further, selective logging interacts with species traits such as body mass, preferred foraging stratum (understorey, midstorey or canopy) and foraging manoeuvre to influence foraging success. Gleaners generally foraged more successfully in primary forest and salliers in logged forest, although these patterns were modified by body mass and foraging stratum. 5. Synthesis and applications: Our study shows how altered microclimates in anthropogenically modified habitats can influence resource availability and have downstream impacts on the behaviour of species at higher trophic levels.

ecology↗