Dibyendu Adhikari

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

IntroductionA 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.MethodsIn 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.ResultsThe 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.ConclusionsThe findings of the study enjoin the need for re-establishment of the species in the suitable areas for its conservation and perpetuation.

Pterocymbium tinctorium (Merrill, 1901) (Magnoliophyta: Malvales: Sterculiaceae: Sterculioideae): new record from mainland India and extension of geographic distribution

We present a new record of the winged-boot tree ( Pterocymbium tinctorium ) discovered in the Khasi Hills of Meghalaya on the Indian mainland. With this record, the known geographical distribution of P . tinctorium is now extended up to the foothills of the Eastern Himalayas in Southeast Asia. The species was recorded from the tropical moist deciduous forests of Meghalaya. The habitat of P. tinctorium was characterized by the presence of surface lime-stone with karst topography. Future investigations should aim at identifying the factors responsible for the restricted distribution of this species so that appropriate conservation measures can be taken.

Microenvironmental heterogeneity caused by anthropogenic LULC foster lower plant assemblages in the riparian habitats of lentic systems in tropical floodplains

Anthropogenic land use and land cover (LULC) create a heterogeneous environment in the floodplains. This heterogeneity may be governing plant species assemblages, diversity, and dominance patterns in the riparian habitats of the lentic systems in tropical floodplains. We tested this hypothesis in the floodplains of Barak river basin in northeast India following standard methods of plant and soil sampling/analysis and multivariate statistical tools. Plant community studies in the riparian habitats of the selected lentic systems were done at monthly intervals for a period of one year, while soil sampling and analysis were done at bimonthly intervals. Standard data visualization plots and canonical correspondence analysis (CCA) were used to assess spatiotemporal variations in species richness and diversity, environmental heterogeneity, and species-environment association. The study revealed that anthropogenic land use and land cover significantly affects species assemblage, diversity, and dominance in the riparian habitats. The variations in vegetation structure and composition with respect to the adjoining land use type plausibly have implications on the structure and functioning of the lentic systems. Thus, the study recommends that a holistic approach involving the riparian areas is required for effective management of tropical floodplains.

Selection of Bradyrhizobium or Ensifer symbionts by the native Indian caesalpinioid legume Chamaecrista pumila depends on soil pH and other edaphic and climatic factors

Nodules of Chamaecrista pumila growing in several locations in India were sampled for anatomical studies and for characterization of their rhizobial microsymbionts. Regardless of their region of origin, the nodules were indeterminate with their bacteroids contained within symbiosomes which were surrounded by pectin. More than 150 strains were isolated from alkaline soils from the Thar Desert (Rajasthan), wet-acidic soils of Shillong (Meghalaya), and from trap experiments using soils from four other states with different agro-ecological regions. Molecular phylogenetic analysis based on five housekeeping (rrs, recA, glnII, dnaK andatpD) and two symbiotic (nodA and nifH) genes was performed for selected strains. Chamaecrista pumila was shown to be nodulated by niche-specific diverse strains of either Ensifer or Bradyrhizobium in alkaline (Thar Desert) to neutral (Tamil Nadu) soils and only Bradyrhizobium strains in acidic (Shillong) soils. Concatenated core gene phylogenies showed four novel Ensifer-MLSA types and nine Bradyrhizobium-MLSA types. Genetically diverse Ensifer strains harbored similar sym genes which were novel. In contrast, significant symbiotic diversity was observed in the Bradyrhizobium strains. The C. pumila strains cross-nodulated Vigna radiata and some wild papilionoid and mimosoid legumes. It is suggested that soil pH and moisture level played important roles in structuring the C. pumila microsymbiont community.

Diversity of Lianas in Eastern Himalayas and North-Eastern India

Lianas constitute an important component of plant diversity in a wide range of ecosystems. The liana diversity has been reported to have critical role in maintaining ecosystem structure and function, with a predicted greater role to play under changing climate conditions. However, our understanding on the diversity pattern of lianas in different forest ecosystems along an elevation gradient is limited. Studies on lianas in the Eastern Himalayas and North-eastern region of India are very few. In this paper, we review the status of liana research in the two biodiversity hotspots viz., the Himalayas and Indo-Myanmar, and conducted primary studies in selected high diversity forests of the region to understand the patterns of liana diversity along elevation gradient in the Himalayas. The diversity and distribution of lianas in three major forest types representing the dominant ecological zones of the region viz. tropical, montane-subtropical and temperate were studied using liana census protocol of Gerwing et al. (2006). We recorded 196 liana species in three forest types in the states of Arunachal Pradesh, Sikkim and Meghalaya in north-eastern India through plot-based field survey. The diversity and abundance of lianas were greater in sub-tropical and tropical forests than temperate forests. Threat assessment for liana conservation was suggested for their in situ conservation.