Varun Varma (PhD student)
varunv [at] ncbs [dot] res [dot] in

My PhD project looks at the effects of nitrogen and phosphorus deposition on the vegetation of tropical dry forests in India. Atmospheric deposition of nutrients resulting from human activities is recognised as a major global change driver and has resulted in changes to productivity, diversity and function of marine, aquatic and terrestrial ecosystems.

With future increases in the rates of deposition a certainty, it is critical to assess the future of ecosystems globally. Currently, most information on ecosystem responses to increased nutrient availability comes from temperate regions, with tropical ecosystems relatively understudied.

In India, tropical dry forests form the largest forest type of the country. This tropical mixed tree-grass ecosystem is of considerable value in terms of the biodiversity it houses and ecosystem services it provides. As with other tropical mixed tree-grass ecosystems around the world, tropical dry forest vegetation to a large extent is shaped by frequent fires which impose a control on tree recruitment.

Using germination, common garden and field burning experiments, my project aims to quantify changes in tree recruitment in tropical dry forests via direct effects on germination and seedling growth, as well as indirectly through nutrient mediated alterations in the ecosystem's fire regime. The project uses a functional group approach, where by differential responses to nutrient fertilisation in leguminous and non-leguminous trees will be quantified.

Other research interests

• Using geo-processing tools such as GIS and remote sensing for vegetation classification and species distribution modelling.
• Assessing and developing methods to construct Species-Area Relationships (SAR) to predict large scale diversity.
• Quantifying plant-pollinator interactions using network analysis.

Software – Black Spot Leaf Area Calculator

Black Spot is a stand alone software and method to estimate leaf area from images of leaves captured using any standard flatbed scanner. This easy to use software allows the user to batch process a large number of samples across multiple species with minimal user input. The software was developed in collaboration with Anand M Osuri and is available as a free download. Visit the Black Spot webpage for more details.

Publications

• Varma, V., Iyengar, S.B. and Sankaran, M. (2016). Effects of nutrient addition and soil drainage on germination of N-fixing and non-N-fixing tropical dry forest tree species. Plant Ecology. DOI:10.1007/s11258-016-0630-9 [link]
   
• Osuri, A.M., Ratnam, J., Varma, V., Alvarez-Loayza, P., Astaiza, J.H., Bradford, M., Fletcher, C., Ndoundou-Hockemba, M., Jansen, P.A., Kenfack, D., Marshall, A.R., Ramesh, B.R., Rovero, F. and Sankaran, M. (2016). Contrasting effects of defaunation on aboveground carbon storage across the global tropics. Nature Communications 7: doi:10.1038/ncomms11351 [link] Open Access

• Varma, V., Ratnam, J., Viswanathan, V., Osuri, A.M., Biesmeijer, J.C., Madhusudan, M.D., Sankaran, M., Krishnadas, M., Barua, D., Budruk, M., Isvaran, K., Jayapal, R., Joshi, J., Karanth, K.K., Krishnaswamy, J., Kumar, R., Mukherjee, S., Nagendra, H., Niphadkar, M., Owen, N., Page, N., Prasad, S., Quader, S., Nandini, R., Robin, V.V., Sait, S.M., Shah, M.A., Somanathan, H., Srinivasan, U. and Sundaram, B. (2015). Perceptions of priority issues in the conservation of biodiversity and ecosystems in India. Biological Conservation 187:201-211. DOI: 10.1016/j.biocon.2015.04.031 [link]
   
• Savory, F.R., Varma, V. and Ramakrishnan, U. (2014). Identifying geographic hotspots of reassortment in a multipartite plant virus. Evolutionary Applications DOI: 10.1111/eva.12156 [link] Open Access
   
• Savory, F.R., Benton, T.G., Varma, V., Hope, I.A. and Sait, S.M. (2014). Stressful environments can indirectly select for increased longevity. Ecology and Evolution. DOI: 10.1002/ece3.1013 [link] Open Access
   
• Varma, V & Osuri, A.M. (2013). Black Spot: a platform for automated and rapid estimation of leaf area from scanned images. Plant Ecology 214: 1529-1534. DOI 10.1007/s11258-013-0273-z [link] [pdf]

• Campbell, A.J., Biesmeijer, J.C., Varma, V. and Wackers, F.L. (2012). Realising multiple ecosystem services based on the response of three beneficial insect groups to floral traits and trait diversity. Basic and Applied Ecology 13: 363-370. [link]