Current Science

C. S. Jha ¹, Rakesh ¹, J. Singhal ¹, C. S. Reddy ¹, G. Rajashekar ¹, S. Maity ², C. Patnaik ², Anup Das ², Arundhati Misra ², C. P. Singh ², Jakesh Mohapatra ², N. S. R. Krishnayya ³, Sandhya Kiran ³, Phil Townsend ⁴, Margarita Huesca Martinez ⁵

Affiliations
1 National Remote Sensing Centre, Indian Space Research Organisation, Hyderabad 500 037, IN
2 Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, IN
3 MS University of Baroda, Vadodara 390 002, IN
4 University of Wisconsin, Madison 53706, US
5 University of California, Davis 95616, US

Abstract

Species diversity and vegetation health are two critical components to be monitored for sustainable forest management and conservation of biodiversity. The present study characterizes species dominance and α -diversity of a forest for the selected region in Mudumalai Wildlife Sanctuary (MWS), Western Ghats, which represents one of the most economically important forest types in India – the tropical dry deciduous forest. NASA’s Next-Generation Airborne Visible and Infrared Imaging Spectrometer (AVIRIS-NG) data at spectral resolution of 5 nm and spatial resolution of 5 m were used to analyse the forest matrix. Biodiversity (α -diversity) map thus generated from airborne platform over 14.5 sq. km area mostly represents the forest tree species diversity. Dominant tree species in the study area were also mapped using AVIRIS data for 21.7 sq. km. Canopy emergent dominant species, viz. Anogeissus latifolia, Tectona grandis, Terminalia alata, Grewia tiliifolia, Syzygium cumini and Shorea roxburghii were classified using spectral angle mapper technique and image-based spectra in the MWS study site. The study shows that nearly 40% area is dominated by A. latifolia and 27.5% by T. grandis in the study site. This study concludes that AVIRIS data can be used in the delineation of species and α -diversity mapping at community level; however, the accuracy achieved for species classification is moderate (60%) due to intermixing of species in the study area. For the Shimoga study site in Karnataka, the field spectra were collected using a spectroradiometer and used for the classification for the three dominant tree species using absorption peak decomposition technique. Fieldcollected pure spectra were analysed and species-wise absorption peaks (Gaussian) with central wavelength, peak amplitude and dispersion were used as the endmembers for classification. AVIRIS-NG data over Shoolpaneshwar Wildlife Sanctuary (SWS) study site used for fuel load estimation with narrow band indices calculated from AVIRIS-NG datasets. AVIRIS-NG data for MWS and Shimoga study site were collected during 2 and 5 January 2016, while for SWS site data were collected on 8 February 2016.

Keywords

Airborne Sensors, Forest Health, Hyperspectral Imaging, Species Diversity.

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Amrita N. Chaurasia ¹, Reshma M. Parmar ¹, Maulik G. Dave ¹, Nirav Mehta ¹, Rajesh Kallaje ², Aradhana Sahu ³, Indu K. Murthy ⁴, C. P. Singh ⁵, N. S. R. Krishnayya ¹

Affiliations
1 Ecology Laboratory, Department of Botany, The Maharaja Sayajirao University of Baroda, Vadodara 390 002, IN
2 Aranya Bhavan, Naya Raipur 492 001, IN
3 Kothi Building, Vadodara 390 001, IN
4 Centre for Sustainable Technologies, Indian Institute of Science, Bengaluru 560 012, IN
5 EPSA Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, IN

Abstract

Variability in the leaf phenology of tropical trees impacts their growth. How phenology of tree species responds over rainfall gradient is relevant to study in the light of current climatic changes. Airborne visible and infrared imaging spectrometer-next generation (AVIRIS-NG) spectral datasets have been considered for this study as they not only provide wider area of coverage, but also high spatial and spectrally resolved output. Canopy-level spectra of 16 common species of four different forest covers in India were synced with observed phenology phase and the annual rainfall in each forest cover was recorded. Reflectance spectra of the same species in the four forest covers distinctively differed over rainfall gradient, indicating intra-species pliability. Consistent lower reflectance/higher absorp-tion at chlorophyll bands of all the common deciduous species in the higher annual rainfall region over that with relatively lower rainfall indicated that deciduous species acclimate green foliage phase of the phenology cycle. Boxplots of reflectance values of chlorophyll absorption band of 16 species showed a decrease in the variability of the datasets over the four forest co-vers, revealing that increasing rainfall provides better synchrony in the phenology phase of the observed tree species. The study highlights the importance of AVIRIS-NG spectral datasets in monitoring different phases of forest phenology associated with growth potential dynamics effectively under changing rainfall pattern.

Keywords

Absorption Band, Canopy-level Spectra, Forest Cover, Phenology Phase, Rainfall Gradient, Tree Species.

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