Kumar Manish

Aim: Energy availability is often assumed to be a primary driver of variation in biodiversity across large‐scale environmental gradients such as elevation, but support for the role of energetic constraints is far from universal. Here, we assume that these variations in energy–richness relationships might arise from the degree of match between the scale of the response of organisms to energy (response scale) and the scale of the observation made (observation scale). Location: 41 mountain ecosystems worldwide, with detailed case studies on Dongling Mountain, China. Time Period: Contemporary. Major Taxa Studied: Trees, shrubs, herbs, ferns, birds, ants, bees, Lepidoptera, Coleoptera, Orthoptera, soil fauna, litter‐layer fauna, bacteria, fungi. Methods: First, we quantify the response scale on the basis of energy requirements, and then, we develop a general scaling model that explicitly describes how the scale matching between response and observation scale influences the predictive power of energy in determining elevational richness patterns; this model holds across taxonomic groups, trophic guilds, and ecosystems across mountains globally. Results: Global analyses strongly supported the model's prediction that scale matching determines the detectability of energy‐richness relationships. On Dongling Mountain, energy availability best explained richness patterns at the predicted response scales for trees, herbs, and litter fauna. Main Conclusions: Our model advances the understanding of montane biodiversity distributions by demonstrating the critical role of scale matching in energy–richness relationships. Our findings strongly support the existing mechanistic foundation for predicting biodiversity changes across spatial scales in montane ecosystems. The scale‐matching principle we identified is likely to be applicable to a wide range of taxa and other ecosystems where energy availability varies across scales.

The Himalayan forests are highly threatened due to anthropogenic pressures ranging from agriculture intensification, deforestation, hydropower development, etc. The present study attempts to document the floristic diversity, composition and structure of vegetation communities in the tropical semi-evergreen forest of North Cachar Hills in Assam. A one-time assessment was made during the peak growing season in a 4000 m² forest area to make an inventory of vegetation structure by using the nested quadrat method. A total of 445 individuals belonging to 52 tree species were recorded from the overstorey, while 161120 individuals belonging to 72 species were recorded from the understorey vegetation. The forest stand structure exhibited a reverse J-shaped population curve, and most tree species showed no regeneration (57%), while others showed either good (23%) or poor (17%) regeneration. This study highlights that the understorey vegetation is as important as the overstorey vegetation with respect to species diversity. This study can serve as a baseline for assessing the impacts of different natural and anthropogenic threats on biodiversity in the study area. Additionally, this study highlights the need to conserve the natural forests of Northeast India and protect them from different threats.

Studies documenting anthropogenic disturbance-driven changes in forest communities of the Eastern Himalaya, a global biodiversity hot spot, are largely lacking. We studied six forest sites of tropical semi-evergreen forests in Arunachal Pradesh in the Eastern Himalaya to understand the effects of varying disturbance intensities on the forest community structure and composition. Based on the magnitude of disturbance, forest sites were classified as experiencing low, moderate and high disturbance. Mean species richness (SR) of trees and shrubs decreased from low disturbance to high disturbance. Mean SR of herbs was maximum in moderately disturbed forest sites. Maximum values of the Shannon-Wiener Diversity Index (SD) were recorded for trees at sites with low disturbance, for shrubs at sites with high disturbance and for herbs in moderately disturbed forests. Pilelou Evenness Index (EI) values were maximum for trees at sites with high disturbance, while maximum EI values for shrubs and herbs were recorded in the forest sites with low disturbance. The number of tree families decreased from 18 to 13 in the forests with low and high disturbance, respectively. Moderate disturbance led to increased herb species richness and diversity, while increasing disturbance produced contrasting effects on trees. High anthropogenic disturbance led to low species richness, but high diversity amongst shrubs. Our investigations suggest that the magnitude of disturbance elicits differential responses in different physiognomic classes in the forest ecosystems and further our understanding of the effects of disturbance in tropical forest ecosystems of a global biodiversity hotspot.

The Himalaya started with mostly immigrant flora but is today home to about 3500–4000 endemic plants that have evolved within a time span of 40–50 million years. It is, however, still unknown as to what factors have been responsible for the development of such high endemism within such a short evolutionary time. It is also unclear as to how plant diversity patterns are structured across the present-day environmental gradients in the Himalaya and whether these diversity patterns will change in the future. My results point towards a positive coincidence between endemic plant species diversification, changes in geo-physical characteristics, and climate in the Himalaya. The present-day plant species richness patterns are hump-shaped, life-form and endemic specific, and scale-dependent. Furthermore, shrublands would emerge as the most successful plant community in future climates, and there would be a need to redesign the Protected Area network due to ensuing climate change in the Himalaya.