Prof.  R.K.  Chaturvedi
Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences,  China

Title: Disturbance pressure in tropical dry forests becomes more severe with decreasing soil moisture

Abstract:

We evaluated how the severity of four disturbance types (harvesting, browsing, drought and fire) change in tropical dry forest (TDF) fragments in central India arrayed across a soil moisture gradient. We asked the following questions: (1) Which disturbances (harvesting, browsing, drought and fire) are important for tree mortality in a TDF and do these change with size class (juvenile, sapling, adult)? (2) How is mortality and recruitment in a TDF related to soil moisture content (SMC) and does the relationship change for different size classes? (3) Is disturbance-related mortality selective?We analysed the structure of a TDF in central India in terms of the tree composition of juveniles, saplings and adults at five distinct sites located along a gradient of SMC, and recorded the numbers of individuals in each size class killed by the four disturbance types over two years. We also recorded total stem density and recruitment at each site. We compared annual mortality index (AMI) and its four disturbance components (harvesting, browsing, drought, fire) and annual recruitment index (ARI), against the mean SMC of each site using simple linear regression. The impact of all disturbances and total AMI decreased as SMC increased whereas ARI increased as SMC increased. Mortality due to harvesting was substantially greater than other disturbances for adult and sapling trees whereas both harvesting and browsing were important drivers of mortality for juveniles. There was little evidence that particular species were being deliberately selected for harvesting across sites.Tree saplings and adults in this TDF were mainly killed by harvesting, indicating that anthropogenic impacts on tree mortality are more important than non-anthropogenic impacts in the TDF, and impacts of all disturbances are more severe with increasing water stress. Thus changes in TDF structure due to harvesting are likely to be more rapid in more arid environments.

Keywords:Tropical dry forest; Harvesting; Browsing; Drought; Recruitment; Mortality

Biography:

Dr. Chaturvedi is a postdoctoral researcher in Xishunagbanna Tropical Botanical Garden (XTBG), Yunnan, China. Born on 20 June 1981 in Varanasi, Uttar Pradesh, India, graduated in 2002, from the University of Allahabad, India. He completed his Masters (2002-2004) and PhD (2004-2010) from Banaras Hindu University, Varanasi India. During his PhD and post-PhD period, he also worked as a Senior Research Fellow (2008-2011) in a Ministry of Environment and Forests, Govt. of India funded project in Banaras Hindu University. Before moving to XTBG, China in 2016, he was employed as a Research Associate (Council of Scientific and Industrial Research, Govt. of India) (2012-2015) in the Institute of Environment and Sustainable Development, Banaras Hindu University. From his PhD and postdoctoral research, Chaturvedi has published 20 articles in refereed, high impact journals. He has also published three books.Recently, he has received the National Natural Science Foundation of China (NSFC) Research Fund for International Young Scientists.

Chaturvedi’s primary research interest is in plant functional traits and carbon sequestration in woodlands, with particular emphasis on the effect of environmental conditions on the ecosystem processes. HisPh.D. research was conducted in a mature, naturally established and unmanaged tropical dry forest (TDF) of India, on the topic, “Plant Functional Traits in Dry Deciduous Forests of India”. His research reported that even small scale variations in soil moisture content (SMC), clay, organic C, total N, total P and canopy light attenuation affected distribution of tree species in the forest. He observed that growth response of the trees at various life stages is modulated by alterations in key functional traits such as specific leaf area, leaf nitrogen and chlorophyll concentration. His study showed that at seedling and sapling stages, stomatal conductance is the most important variable, emphasizing its role in shaping the growth patterns across spatial and temporal gradients of soil water availability. However, at the adult stage photosynthetic rate is the most important determinant of the tree growth in TDFs.

During postdoctoral period, Chaturvedi studied the effects of disturbance and edaphic properties on carbon accumulation in the tree species of TDF in India. In this study, he observed significant difference in the abundance of livestock dung pellets, damaged juveniles, saplings and adult tree stumps across the study sites, which reflected very high anthropogenic pressure and improper management of forest resources. The disturbance intensity across the study sites showed negative relationships with SMC, species richness, stem density, carbon density and carbon accumulation. Annual mortality index (AMI) and annual recruitment index (ARI) was significantly different across the juvenile and sapling species. During this study,Chaturvedi developed regression models for non-destructive estimation of tree biomass at juvenile, sapling and adult stages by incorporating wood specific gravity (ρ) as a simple multiplication factor in the models.

In China, Chaturvedi is working on the topic, “Community assembly and functional diversity in the savannas and woodlands of the dry valleys of Yunnan”.In this project, he is estimating biodiversity and functional diversity in the pine woodlands, dry valley savanna, high altitude oak woodlands, limestone grasslands and tropical montane grasslands across the Yunnan province.