CONTROLS OF CANOPY ACTIVITIES ON ROOTS AND SOIL CARBON DYNAMICS IN A YOUNG PONDEROSA PINE FOREST

Principal Investigators:
Alien Goldstein, Associate Professor, Division of Ecosystem Science, UC Berkeley
Ye Qi, Assistant Professor, Division of Forest Science, UC Berkeley
Weixin Cheng, Associate Professor, Department of Environmental Studies, UC Santa Cruz

Duration of Project: 2 years

Project summary

Globally, belowground C fluxes in forest ecosystems constitute a major link between atmospheric C and the soil C pools. However, a lack of understanding of belowground carbon fluxes in forest ecosystems in general, and specifically the role of roots in belowground C dynamics is one of the primary limitations in our ability to assess the contribution of forests as global C processors. This proposed project combines the ongoing canopy scale and soil chamber gas flux measurements at the Blodgett Forest research site with measurements of root dynamics using a minirhizotron approach, and addresses the issue of aboveground controls on root turnover and soil carbon sequestration. We propose to test three hypotheses:

(1) In contrast to the tight coupling of root activities with photosynthesis in herbaceous systems, root dynamics in forests are decoupled from photosynthetic activity in the short-term, but strongly linked with photosynthesis in the medium-term via regulating root demography.
(2) Root dynamics exert a major control over the spatial and seasonal patterns of the soil surface CO₂ efflux; and such control is the most apparent when roots are active.
(3) Inter-annual variations of precipitation, drought stress, total photosynthetic activity, and root production are key controlling factors determining the overall ecosystem carbon balance of ponderosa pine forests in the Mediterranean climate of California.

By testing these hypotheses, we aim to contribute to the two goals of the mission of the Kearney Foundation: (1) understand mechanisms and processes governing the storage and flow of carbon in soils that support California's diverse ecosystems, and (2) assess the roles of soils in emissions and consumption of greenhouse carbon gases.