Environmental controls on soil and whole-ecosystem respiration from a tallgrass prairie

ABSTRACT piration and heterotrophic microbial respiration. Net ecosystem exchange of CO2 as an integration of photo-Environmental controls on C cycling in terrestrial ecosystems are synthesis, plant dark respiration, and soil respiration indifficult to define, because (i) C fluxes from plant vs. microbial activity are difficult to separate, and (ii) controlling variables are often inter- grasslands can be obtained with various micrometeoro-correlated. We investigated temporal and spatial determinants of soil logical techniques, which integrate across large land areas respiration and whole-ecosystem respiration using nighttime exposure (Verma, 1990; Norman et al., 1992). Knowing the contri-of static chambers to alkali absorption during 2 yr on a tallgrass prairie bution of soil respiration to these fluxes would improve in northeastern Kansas. Soil respiration (mg CO2-C m2 h1) was pos- our understanding of the C cycle and help determine rates itively related to soil organic C (SOC, kg m2 0.1 m1) through linear of ecosystem C sequestration. Separation of soil res-regression [CO2-C44 (40 SOC), r 2 0.71]. Temporal variations in piration from whole-ecosystem respiration is best suitedrespiration were related to soil temperature, water-filled pore space during the nighttime, when photosynthetic fixation of(WFPS), and a plant growth rate function, with a combined R 2 of 0.76 CO2 is not a factor. There is also a need to better under-for soil respiration and of 0.84 for whole-ecosystem respiration. Tem-stand whole-ecosystem respiration during the nighttime,poral variograms suggested that both soil and whole-ecosystem respi-ration became increasingly dissimilar the longer the time between mea- since micrometeorological techniques for net ecosystem surements up to 30 d, while dissimilarity in soil temperature and WFPS exchange of CO2 are generally less suited during the night