My research focuses on what controls the exchanges of energy, water and carbon between land surfaces and the atmosphere and how it pertains to vegetation dynamics. This research is relevant to several environmental problems, including understanding changes in near-surface climate, pattern of biodiversity and the carbon cycle.
By now, there is little doubt in the research community that due to fossil fuel emissions and land use changes our planet is already experiencing environmental changes beyond the bounds of natural variability. Hence, in managing and preserving our natural resources to the best of our knowledge studies that address how such perturbations affect biological systems are utterly significant. In this context, I decided to join the Center for Tropical Research at UCLA’s Institute of the Environment.
In this research, we predict potential species distributions in terrestrial hot spots (e.g. Tropical Africa) by applying ecological niche models that combine satellite and ground-based measurements of abiotic and biotic variables describing a species habitat along with species occurrence data from field surveys.
Compared to climate research, this research venue is still in a pioneering state. Newly implemented ecological niche models with algorithms based on machine learning concepts are currently being tested in our group. In addition, sketching patterns of biodiversity with data from earth orbiting satellites is even more in its infant stage, and we currently investigate which satellite data at which resolution are most useful in predicting a species geographical distribution. Using outputs from climate models and land use change scenarios, we then can better predict a species future distribution, thereby also providing important input to the development of effective conservation priorities in a particular region.
Terrestrial and marine environments are currently absorbing roughly half of the carbon dioxide that is emitted by fossil fuel combustion; the buffering of CO2 increase by these environments prevents a more rapid warming. Over the last decade, various terrestrial carbon sink mechanisms have been identified with differing spatial and temporal signatures. These include changes in land use pattern (forest regrowth, fire prevention etc.), CO2 fertilization and nitrogen deposition, and longer active growing seasons associated with a general warming trend. In my previous postdoctoral research with Professor Inez Fung, a pioneer in carbon cycle and climate research, we also find evidence that large-scale continental droughts in the recent decade have influenced the terrestrial carbon balance.
In my second research venue, I intend to continue investigating how the terrestrial carbon balance might shift in different hydrologic regimes; that is, how would carbon exchange processes change in a warmer and drier climate (as currently observed) versus a warmer and wetter climate. The interaction of drought-rain cycles with biospheric processes also involves a multitude of time-scales, leading to various periodicities in carbon inventories and fluxes. These interactions may thus contribute to apparent short-term trends in atmospheric CO2 and must be better understood to predict more reliably the evolution of terrestrial carbon sinks. To explore these research questions, I am utilizing GCM outputs and along with new and improved surface based and remotely-sensed measurements of global vegetation (e.g., AVHRR, MODIS/MISR, SeaWiFS and ENVISAT), precipitation (e.g., CMAP), soil moisture (e.g., AMSR) and atmospheric CO2 in conjunction with improved assimilated products of the NCEP-reanalysis and other derived drought indices (e.g. PDSI). I expect that this research will contribute to the long-term goal of improving projections of the co-evolution of climate and the carbon cycle.