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Quantifying Rhizosphere Respiration for Two Cool‐Season Perennial Forages
Author(s) -
Skinner R. Howard
Publication year - 2011
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci2011.03.0155
Subject(s) - biology , soil respiration , rhizosphere , respiration , agronomy , red clover , dactylis glomerata , growing season , trifolium repens , forage , botany , poaceae , genetics , bacteria
Understanding the regulation of ecosystem CO 2 flux from forage production systems requires knowledge of component fluxes, including photosynthetic uptake and respiratory loss. Experimental separation of soil respiration into heterotrophic and rhizosphere respiration has been difficult, complicating efforts to quantify management and environmental effects on grazing land C sequestration. This study takes advantage of differences in the natural abundance of 13 C between C 3 and C 4 plant species to separate microbial respiration of C 4 –derived soil organic matter from root respiration by C 3 forage species. Respiratory flux and C isotope data were collected in May, July, and September 2008 and 2009 from plots containing either orchardgrass ( Dactylis glomerata L.) or white clover ( Trifolium repens L.). The site had been a big bluestem ( Andropogon gerardi Vitman) field for about 30 yr before grass and clover establishment. Thus, the soil organic C had a strong C 4 signature. At each sampling period, respiration measurements were made at the midpoint of the regrowth cycle, 2 wk following mowing. Rhizosphere respiration accounted for about 50% of soil respiration in July and September but only 40% in May. Rhizosphere respiration under orchardgrass averaged 50% of total soil respiration compared with 43% under white clover. Accurate quantification of the components of ecosystem respiration will aid in the development of realistic models to simulate ecosystem C flux.