Current Science

N. S. R. Krishnayya ¹, Binal Christian ¹, Dhaval Vyas ¹, Manjit Saini ¹, Nikita Joshi ¹, K. R. Manjunath ², Tanumi Kumar ², Hitendra Padalia ³, Rajee George ⁴, S. P. S. Kushwaha ³

Affiliations
1 Ecology Laboratory, Department of Botany, The M.S. University of Baroda, Vadodara 390 002, IN
2 Space Applications Centre, India Space Research Organization (ISRO), Ahmedabad 380 015, IN
3 Forest and Ecology Department, Indian Institute of Remote Sensing, ISRO, Dehradun 248 001, IN
4 Department of Environment and Forest, Andaman and Nicobar Islands, Port Blair 744 102, IN

Abstract

Tropical forests are the most diverse and complex terrestrial systems. India is one of the mega diverse countries supporting rich floral diversity coming from diverse climatic conditions spread across the length and breadth of the country. Unique characteristics of these forest covers coupled with immense pressure of human activities make their monitoring essential so as to ensure their long-term sustainability. More reliable evaluation of forest cover can give better inputs to the National Mission for a Green India. Imaging spectroscopy is an appropriate technique to address some of these vital issues. This technique has seen an exponential growth in the past two decades, addressing various forestry applications such as tree species identification, invasive species mapping, monitoring phenology, biophysical and biochemical characterization, to name a few. Data acquisition through imaging spectroscopy can be done across different spatial and spectral ranges according to the needs of the user. The review highlights important measures to be taken in using imaging spectroscopy for forestry studies, specifically in the Indian context. It emphasizes future outlook of the technology for a sustained assessment of tropical forest cover.

Keywords

Forest Cover, Imaging Spectroscopy, Parameter Estimation, Sustained Assessment.

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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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Nirav Mehta ¹, Sergio Sanchez ², Prashanth Marpu ², Ankur R. Desai ³, N. S. R. Krishnayya ¹

Affiliations
1 Ecology Laboratory, Department of Botany, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara 390 002, IN
2 Institute Center for Water and Environment (iWATER), Masdar Institute of Science and Technology, PO Box 54224, Abu Dhabi, AE
3 University of Wisconsin-Madison, Department of Atmospheric and Oceanic Sciences, 1225 W Dayton St, AOSS 1549, Madison, WI 53706, US

Abstract

Water availability is the central limiting factor for vegetation carbon allocation in semi-arid forests. However, the sensitivity of this relationship likely varies as a function of total tree cover and tree diversity. In the present study, a set of re-measured semiarid forest plots in India were analysed to test how sensitive biomass, productivity and soil organic carbon (SOC) accumulation were to variability in precipitation from plot-level and remote sensing solarinduced fluorescence (SIF) measurements. Variability in mean precipitation at zones I and II impacted tree density, recorded as 150 and 400 trees ha^–1 respectively. Results show that low tree cover plots had lower woody biomass NPP (NPP_wood) and lower SIF sensitivity to inter-annual variation of precipitation. Increment in NPP_wood over a five-year period was significantly smaller (P < 0.05) in zone I (0.21 Mg ha^–1 year^–1, CI₉₅, 0.14–0.28) than at zone II (2.44 Mg ha^–1 year^–1, CI₉₅, 1.43–3.45). Mean annual SOC increment at 0–5 cm depth varied between 0.13 and 0.75 Mg ha^–1 year^–1 across the study area. Results highlight the importance of tree cover diversity in modulating the response of semi-arid forests to carbon storage across a precipitation gradient.

Keywords

Annual Rainfall, Carbon Storage, Precipitation Variability, Semi-arid Forest, Tree Cover And 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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