Habitat suitability of Gymnocladus assamicus - A critically endangered plant of Arunachal Pradesh, India using machine learning and statistical modeling

Ujjal Deka Baruah

Acta Ecologica Sinica , 2022 , https://doi.org/10.1016/j.chnaes.2022.05.009

Abstract:

 

The present study sought to identify the potential distribution range of critically endangered Gymnocladus
assamicus in Arunachal Pradesh based on published data and fild collection. We used the Maxent model to
estimate the range of distribution and the result was then compared with three other models, i.e., the Generalized Linear Model (GLM), the Bioclim and the Random Forest model to assess the species' habitat suitability. A total of 23 different environmental variables were used, including bioclimatic ones, monthly minimum and maximum temperature, monthly precipitation and elevation data. The Maxent output listed 12 variables explaining 99.9% variation in the model. In comparison, Maxent showed the maximum region under habitat suitability criteria (1884.48 km2), followed by Random Forest (70.73 km2) and Bioclim (11.62 km2) model. Except for the Maxent model, suitable habitats predicted by other models are highly restricted within and across the study species' current distribution range. The average model prediction shows an expanded distribution range for the species up to Tawang which is the closest district of currently known distribution of the species in the state. Thus, the present study recognizes the importance of the geographic range of G. assamicus, a critically endangered species with very limited spatial distribution range and also provides some specifi details to explore possible habitats for the species in new areas of potential occurrence in Arunachal Pradesh, India.
 


Spatio-temporal characterization of tropospheric ozone and its precursor pollutants NO2 and HCHO over South Asia

Ujjal Deka Baruah

Science of The Total Environment , vol: 809 , 151135, 2022 , https://doi.org/10.1016/j.scitotenv.2021.151135

Abstract:

In recent decades, South Asia has experienced declining air quality, with much of the attention being focused on extremely high levels of particulate matter. Here, we analyze tropospheric ozone (O3), formaldehyde (HCHO), and nitrogen dioxide (NO2) to assess other measures of air quality across South Asia from 2008 to 2018. The IASI-Forli retrieved tropospheric ozone data was validated with ozonesonde, reanalysis (ERA5), satellite (TES), and model simulation products (GEOS-Chem and TOMCAT/SLIMCAT). Space-based observations of these three trace gases were used to conduct a spatio temporal analysis over South Asia using trend analysis (Theil-Sen and linear regression), change-point detection (Pettitt's test), and hotspot identification (Getis-Ord Gi*). We used the formaldehyde-nitrogen dioxide ratio (FNR) to identify NOx limited, VOC limited, and transitional regimes in South Asia. Counter to previous studies, a statistically significant decrease of HCHO (−0.0041 DU yr−1) and O3 (−0.064 DU yr−1) was detected for South Asia; however, NO2 is increasing the 0.001 DU yr−1 over South Asia during 2008–18. The Indo-Gangetic Plains emerged as being critically affected by the three trace gases. Certain parts of southern and south-eastern India are gradually emerging as NO2 and HCHO hotpots. No significant O3 hotspots were discernible, though coldspots existed along the Himalaya belt of India, Nepal, and Bhutan and mountainous tracts of Pakistan. FNR indicates the reduction of NOx in NOx-limited regime of the Indo-Gangetic Plains reduced the formation of tropospheric O3 over South Asia.


Geochemical Characteristics of Metasomatised Diorites in and around Umsopri of Ri-bhoi District, Meghalaya, India

Dr. Anamika Gogoi and Dr. Balen Bhagabaty

Journal of Geography, Environment and Earth Science International , vol: 15 , 1-14, 2018

Abstract:


Mineral Chemistry and Geothermometry of Biotite in the Granitoids , Located in and around Jirang -Patharkhamah Area,Ri-Bhoi District,Meghalaya,India

Dr. Anamika Gogoi and Dr. Balen Bhagabaty

Journal of the Geological Society of India , vol: 98 , 245–259, 2022

Abstract: