Primary Productivity and Water Balance of Grassland Vegetation on Three Soils in a Continuous CO2 Gradient: Initial Results from the Lysimeter CO2 Gradient Experiment

Authors

Philip A. Fay, USDA-ARS Grassland Soil and Water Research LaboratoryFollow
Alexia M. Kelley, Duke University
Andrew C. Procter, Duke University
Dafeng Hui, Tennessee State University
Virgina L. Jin, USDA-ARS Grassland Soil and Water Research LaboratoryFollow
Robert B. Jackson, Duke UniversityFollow
Hyrum B. Johnson, USDA-ARS Grassland Soil and Water Research Laboratory
H. Wayne Polley, USDA-ARS Grassland Soil and Water Research LaboratoryFollow

Document Type

Article

Date of this Version

2009

Comments

Published in Ecosystems (2009) 12: 699–714.

Abstract

Field studies of atmospheric CO₂ effects on ecosystems usually include few levels of CO₂ and a single soil type, making it difficult to ascertain the shape of responses to increasing CO₂ or to generalize across soil types. The Lysimeter CO₂ Gradient (LYCOG) chambers were constructed to maintain a linear gradient of atmospheric CO₂ (~250 to 500 µ 1^-1) on grassland vegetation established on intact soil monoliths from three soil series. The chambers maintained a linear daytime CO₂ gradient from 263 µ 1^-1 at the subambient end of the gradient to 502 µ 1^-1 at the superambient end, as well as a linear nighttime CO₂ gradient. Temperature variation within the chambers affected aboveground biomass and evapotranspiration, but the effects of temperature were small compared to the expected effects of CO₂. Aboveground biomass on Austin soils was 40% less than on Bastrop and Houston soils. Biomass differences between soils resulted from variation in biomass of Sorghastrum nutans, Bouteloua curtipendula, Schizachyrium scoparium (C₄ grasses), and Solidago canadensis (C₃ forb), suggesting the CO₂ sensitivity of these species may differ among soils. Evapotranspiration did not differ among the soils, but the CO₂ sensitivity of leaf-level photosynthesis and water use efficiency in S. canadensis was greater on Houston and Bastrop than on Austin soils, whereas the CO₂ sensitivity of soil CO₂ efflux was greater on Bastrop soils than on Austin or Houston soils. The effects of soil type on CO₂ sensitivitymay be smaller for some processes that are tightly coupled to microclimate. LYCOG is useful for discerning the effects of soil type on the CO₂ sensitivity of ecosystem function in grasslands.