Variation in species assemblages due to micro-topography and flow regime govern vegetation carbon stock in seasonal floodplain wetlands

Hypothesis:Variation in species assemblages due to micro-topographic features and flow regime determine vegetation carbon stock in floodplain wetlands.Material and method:We tested this hypothesis in Chatla—a tropical floodplain wetland located in northeast India.Five sampling stations characterized by contrasting micro-topographic and flow parameters were selected in the wetland for study.Species composition,assemblage pattern,and vegetation carbon stock were studied in these stations during three flood phases,i.e.,early,middle,and late flood phases following standard methods.Univariate and multivariate statistics were used to determine the relationship between the selected environmental parameters,plant species assemblages,and vegetation carbon stock of the wetland.Results:Thirty-one species of herbs and five species of shrubs were recorded from the five stations in Chatla floodplain wetland.Flow regime characterized by water flow velocity and discharge showed substantial variations across the stations.These parameters in turn are related to variations in the micro-topographic characteristics namely depth,width,and cross-sectional area of the stations.Plant species composition and abundance differed significantly with respect to micro-topography and flow regime as revealed by the cluster diagram.The canonical correspondence analysis revealed strong association of plant species assemblages with the micro-topography and flow regime within the wetland.Multiple regression analysis revealed a significant positive relationship of the vegetation carbon stock with the water discharge.Conclusions:Spatial variation in plant species diversity because of micro-topography and flow regime determines the vegetation carbon stock in floodplain wetlands.Modification of these parameters by anthropogenic activities such as mining and quarrying may potentially influence the carbon stocking potential of seasonal floodplain wetlands.Therefore,appropriate measures should be taken to maintain the integrity of the natural topographic features of such wetlands.

Abundance and habitat-suitability relationship deteriorate in fragmented forest landscapes:a case of Adinandra griffithii Dyer,a threatened endemic tree from Meghalaya in northeast India

Introduction:A strong positive‘abundance and habitat-suitability’relationship is crucial for conservation of species.Nevertheless,anthropogenic alteration of natural landscapes leading to land use and land cover change,habitat loss,and species extinctions(may)have putatively disturbed this relationship.Hence,it is important to study the nature of the relationship in such human influenced landscapes.Methods:In this study,we endeavored to understand the consistency of the relationship in the fragmented natural landscapes in the Khasi,Garo,and Jaintia hills of Meghalaya in northeast India,with Adinandra griffithii(an endangered endemic tree)as a model species.We reconstructed the distribution of its suitable habitats as a function of the remotely sensed vegetation phenology(i.e.,EVI data),using point occurrence data and ecological niche modeling(ENM)tool.Estimation of the abundance and habitat characterization was done through field surveys following standard methods.Results:The study revealed that remotely sensed landscape-level vegetation phenology could effectively discriminate the suitable and unsuitable habitats of threatened species.Linear regression model showed a weak positive correlation between abundance and predicted habitat suitability for adult trees indicating(plausible)deterioration in the relationship.However,sapling and seedling populations did not show a precise trend in this respect.Field-based studies revealed that removal of the species from the suitable habitats because of anthropogenic disturbances possibly weakened the abundance-suitability relationship.Conclusions:The findings of the study enjoin the need for re-establishment of the species in the suitable areas for its conservation and perpetuation.