Throughout the last month, we have been featuring all the articles that were shortlisted for the Harper Prize 2020. The Harper Prize is an annual award for the best early career research paper published in Journal of Ecology.
Here we hear more from Atul Joshi, who was jointly awarded this year’s prize alongside Blanca Arroyo-Correa!
I grew up in the stunningly beautiful and biologically diverse Western Ghats, a global biodiversity hotspot in India and have always been interested in nature. I was especially interested in plants since my childhood. I used to spend hours in my backyard garden, farms and nearby wild places. Although my love for plants and mountains has been there since childhood, I never imagined that this passion could be turned into a profession until I finished a post-graduate diploma in Journalism and started working for a regional daily as a sub-editor. Here, I realised that there were different avenues where I could pursue my passion as a profession. I obtained admission to the Masters in Forestry course at Forest Research Institute, Dehradun. At this Institute, I got the opportunity visit diverse ecosystems across India.
My stint with ecology began in a real sense when I started dissertation work on coffee invasion in the rainforests of southern Western Ghats with TR Shankar Raman and Divya Mudappa at the Nature Conservation Foundation, Mysore. Shankar Raman and Divya Mudappa have been working on Rainforest Restoration in Annamalai hills in the Western Ghats. It was an awesome experience being part of their research team. I continued my stint with the Nature Conservation Foundation with MD Madhusudan and AJT Johnsingh to work on large mammal connectivity across the Western Ghats landscapes and to carry out capacity building programmes for the Forest Department. I later moved on to do a PhD on the role of humans and climate on the structure and function of forest-grassland mosaic ecosystems in the high elevation Western Ghats biodiversity hotspot with Mahesh Sankaran and Jayashree Ratnam at the National Centre for Biological Sciences, Bengaluru which became a memorable journey of a lifetime.
About the study
This study resolves a century-long academic debate on what maintains the forest-grassland mosaics in the tropical montane forest (shola) – grassland ecosystems in the high elevation Western Ghats Biodiversity Hotspot in India. The results of our research, reported in this paper, provide conclusive empirical evidence for a primary role of frost and freezing temperatures in limiting tree establishment in grasslands of these highly diverse mosaic ecosystems. We show that native tree seedlings do germinate in grasslands but incur very high mortality due to frost and freezing temperatures during winter. However, a non-native invasive tree species – Acacia mearnsii, being a better tolerant of frost and freezing temperatures due to its sub-tropical affinity, incur relatively less mortality and thereby able to establish and invade these grasslands.
Our results also suggest that future increase in temperatures due to global warming may release trees from this limitation and favour tree establishment in grasslands which would further contract the grasslands that are known to harbour very high diversity and endemism. Unfortunately, much greater rates of survival of non-native Acacia than that of native trees at elevated temperature indicates that ongoing Acacia invasion of grasslands will be further exacerbated as the climate warms.
Studies across a range of tropical forest-grassland mosaics across the globe have postulated a major role of fire and herbivory in maintaining these mosaics. However, the chronological sequences with frost occurring first and the more predictable occurrence of frost than fire point to frost and freezing temperatures as the major drivers in limiting native tree establishment in grasslands of our study system. This study suggests examining the role of low temperatures and frost would yield a revised view on the relative importance of frost and temperatures in maintaining alternate vegetation states in the tropics.
About the research
This research brought forward the important role of frost as a driving factor in tropical forest-grassland mosaic ecosystems. My PhD mentor Dr Jayashree Ratnam and I have recently started to review the literature to understand how the frost has been playing a role in other tropical mosaic ecosystems. Alongside, I have been interacting with peers and helping students who have been interested and researching similar topics and ecosystems.
Atul Joshi Ashoka Trust for Research in Ecology and the Environment, Bengaluru, India
You can read Atul’s winning article here: Frost maintains forests and grasslands as alternate states in a montane tropical forest–grassland mosaic; but alien tree invasion and warming can disrupt this balance by Joshi, Ratnam, & Sankaran.
You can also read all 8 shortlisted papers in our Harper Prize 2020 Virtual Issue.