Current Projects
Biodiversity and Traits in Chinese Grasslands
I'm working on a large-scale experiment designed to detect the effects of biodiversity on ecosystem functioning in the grasslands of Inner Mongolia in conjunction with the Institute of Botany at the Chinese Academy of Sciences. My work is focusing on plant-herbivore interactions and how plant traits determine the way species assemble into communities. More about the project here.
Previously I was part of a team of researchers from Department of Ecology at Peking University that traveled thousands of kilometers across Chinese grasslands, collecting grassland data both to parameterize a complete carbon budget of Chinese grasslands and coll, plant diversity, and grassland ecophysiology was collected.
The most important leaf traits vary together in predictable ways across biomes. These principally include photosynthetic capacity, leaf nitrogen content, and leaf lifespan, and describe a fundamental axis of variation which has been constrained by evolutionary forces. Researchers at the Department of Ecology at Peking University found that global patterns for leaf traits held true even in the extreme environments of high-altitude,cold-temperature grasslands on the Tibetan Plateau (He, Wang, Wang, et al. 2006).Looking at the entire geographical range, we examined the influence of climate, geography, and taxonomic identity on foliar carbon (C) and nitrogen (N) content (He, Fang, Wang, et al. 2006). We expected that since warmer areas have typically been found to have lower soil N in global data sets (since tropical soils are N-impoverished), we would find a negative relationship between C:N and temperature across our grassland sites. However, across all biomes and temperature/precipitation gradients, leaf C:N remained remarkably stable. We followed up this work with a detailed analysis of nitrogen-to-phosphorus (N:P) ratios in these same individuals, finding to our surprise that climate exterted very little influence on this key measure of growth rate (He, Wang, Flynn, Ma, Wang, and Fang 2008). We have two further studies in review looking specifically at the effects of soil and also at the covariance between traits, asking how phylogeny, climate, and other factors control the tradeoffs between leaf persistence and leaf productivity.
Functional Diversity
Taxonomic diveristy may range from 3 to 300 million species globally. What are they all doing here? Interest in the how changes in diversity (through extinctions or invasions) alter the way ecosystems function has recently focused on the traits of organisms, rather than their identity -- functional diversity. I worked with a group of graduate students organized through the National Center for Ecological Analysis and Synthesis to assess how functional diversity changed across agricultural land use intensity gradients. FD fell starkly in bird and mammal communities, and in many cases fell more than expected by chance, given the changes in species richness, in more intensively managed systems (Flynn et al, Ecology Letters).
I have also been working with Dan Bunker and Shahid Naeem to address how functional diversity measurement can and should address species compensation, redundancy, and complementarity. In addition, I worked with a BioMERGE group to prepare a summary chapter on functional diversity measurement.