Gross Primary Productivity of Terrestrial Plant Communities and the Potential to Store Carbon in Soils.

Considerable concern exists about the accumulation of atmospheric CO₂ and its impact on global climate change.  Photosynthesis is the primary biological process by which CO₂ is removed from the atmosphere and stored in plant components, organisms that consume plants, or potentially for long periods of time in soils as organic carbon (SOC).  Gross primary productivity (GPP) refers to the net photosynthesis rate, photosynthesis minus respiration rate, of plants living in a community.  Many farmed soils in the U.S. have experienced significant depletion of SOC and now represent a significant opportunity for the storage of atmospheric carbon.  Pierce Cedar Creek Institute (PCCI) near Hastings, Michigan consists of a diverse landscape of forests, meadows (tall grass prairie and unrestored fields), and wetlands, some exposed to intensive agriculture.  Significant potential exists to optimize canopy GPP and store carbon in soils.  The goal of this project was to measure leaf-level photosynthesis rates as a function of light intensity and SOC, then use GIS tools to scale up an estimate of GPP and potential for SOC storage for the main plant communities comprising the PCCI landscape.  Significant differences existed among the light use efficiency relationships of the 13 plant species that comprise the majority of the leaf area in each plant community type.  Consequently, significant differences existed among the communities they comprise such that restored prairie and brushy fields were the largest contributors to fixed carbon because of fast CO₂ uptake rates. Old woodlands were less productive than young. Restoration practices to optimize carbon assimilation rates and sequestration as SOC could include selective harvest of wood products from old woodlands and conversion of shrubby fields to native tall grass prairie.