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ARS Home » Plains Area » Temple, Texas » Grassland Soil and Water Research Laboratory » Research » Publications at this Location » Publication #324354
Title: Biotic regulation of CO2 uptake-climate responses: Links to vegetation properties

Author
item Polley, Herbert
item Gibson, Anne
item Fay, Philip
item WILSEY, BRIAN - Iowa State University

Submitted to: Ecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2016
Publication Date: 11/24/2016
Publication URL: http://handle.nal.usda.gov/10113/63334
Citation: Polley, H.W., Gibson, A.E., Fay, P.A., Wilsey, B.J. 2016. Biotic regulation of CO2 uptake-climate responses: Links to vegetation properties. Ecosystems. 19:1376:1385.

Interpretive Summary: Plant species differ in traits that regulate the response of carbon uptake (photosynthesis) and growth to seasonal and inter-annual changes in climatic variables such as temperature and precipitation. Identifying traits and patterns of trait distribution relevant to photosynthesis is a priority for predicting climate impacts on plant productivity. We measured photosynthesis and canopy-level traits in field plots in central Texas, USA that had been planted to different combinations of perennial grassland species. Our goal was to determine links between canopy traits and photosynthesis-climate relationships of multi-species plant communities. Climatic variables alone explained much of the variation in photosynthesis of communities during 3 years of measurements. Photosynthesis was highly correlated with changes in air temperature and precipitation, but also differed substantially among communities of differing species composition. Photosynthesis differed among communities partly because the sensitivity of photosynthesis to seasonal and inter-annual changes in temperature and precipitation differed among communities. The differing sensitivities of photosynthesis to temperature and precipitation resulted because communities differed in the amount of nitrogen (N) present per unit of leaf area and in photosynthesis per unit of intercepted light (light use efficiency). Our results indicate that predictions of the climate response of photosynthesis and growth of mixed-species grasslands could be improved by incorporating measurements of two canopy-level traits, leaf N and light use efficiency.

Technical Abstract: Identifying the plant traits and patterns of trait distribution in communities that are responsible for biotic regulation of CO2 uptake-climate responses remains a priority for modelling terrestrial C dynamics. We used remotely-sensed estimates of GPP from plots planted to different combinations of perennial grassland species in order to determine links between traits and GPP-climate relationships. Climatic variables explained >50% of the variance in temporal trends in GPP of grassland communities despite large variation in CO2 uptake among seasons, years, and communities of differing composition. GPP was highly correlated with contemporary changes in air temperature (AT) and precipitation deficit (potential evapotranspiration minus precipitation), but was weakly and negatively correlated with precipitation summed over both 15 days and 210 days prior to flux measurements. GPP varied by as much as a factor of three among communities of differing composition. Communities differed in GPP-AT and GPP-water (deficit, precipitation) relationships. Accounting for community-specific differences in GPP-climate relationships explained an additional 12% of variance in GPP. Community differences in GPP-water (deficit, precipitation) slopes were linked to differences in community-level light use efficiency (GEE*). Community differences in GPP-AT slopes were linked to community differences in a species abundance-weighted index of specific leaf N (SLN). GEE* and weighted SLN represent community-level vegetation properties that may regulate how CO2 uptake responds to climatic variation in grasslands.