On an annual basis terrestrial ecosystems exchange vast quantities of carbon (C) with the Earth’s atmosphere. This exchange is fueled by the efficient use of soil resources such as water, nitrogen and phosphorus, which are essential for plant growth. Acquisitions of soil resources require C investments belowground that necessarily come at the expense of aboveground growth. What biogeophysical processes control this fundamental tradeoff and what are its implications for the global C cycle?
Research in my lab focuses on the plant – microbe – soil nexus. We use a combination of experimental, observational, meta-analytical and modeling approaches to understand biogeochemical cycles at micron to global scales. In this presentation, I will discuss the results of two recent meta-analytic research activities. First, we studied global allocation of C belowground to understand how nutrient supply rates, plant nutrient uptake strategies and nutrient-use efficiency feedback on primary production and soil C storage. Second, we studied how C allocation to roots and the associated rhizosphere affect rates of decomposition of soil organic matter and plant nutrient acquisition. Together, these analyses suggest the primary limitation on productivity in terrestrial ecosystems transitions from belowground resources at high latitudes to aboveground resources at low latitudes as C-intensive root- and mycorrhizal-mediated nutrient capture is progressively replaced by rapidly cycling, enzyme-derived nutrient fluxes when temperatures approach the thermal optimum for biogeochemical transformations. I conclude with some speculations as to the implications of these results for the global C cycle and global change.