A Vineyard Agroecosystem: Disturbance and Precipitation Affect Soil Respiration under Mediterranean Conditions

Abstract

We investigated impacts of agricultural management practices on soil respiration (Rs) in a Cabernet Sauvignon (Vitis vinifera) vineyard (Oakville, CA; November 2003–December 2005). We determined (i) response of Rs to cover cropping, mowing and tillage; (ii) environmental factors controlling Rs; and (iii) total annual C lost through Rs A winter cover crop was either mown (CC+mow), or mown and tilled (CC+Till), and resident vegetation was tilled (RV+Till). Precipitation amount and pattern differed between years, and low Rs rates occurred during summer drought and high rates during wet periods. Total CO2 emissions differed only in Year 2 (RV+Till: 10.99 ± 0.30, CC+Till: 10.11 ± 0.49, CC+mow: 8.57 ± 0.54 Mg CO2–C ha−1). After tillage or mowing, Rs increased five‐ to six‐fold in tilled treatments and two‐fold in the mown treatment (Year 1). In Year 2, Rs increased two‐ to three‐fold after tillage only. Rs increased after ‘post‐management’ rainfall in spring and was 1.5‐ to 2‐fold greater in tilled than mown treatments in both years due to prior incorporation of plant biomass during tillage. After fall rainfall, Rs was 1.7‐fold greater in mown than tilled treatments (Year 1). Our findings suggest that the interaction of management practice with climate and soil conditions before disturbance (i.e., management and rainfall) influenced Rs Polynomial regressions of Rs on GWC and soil temperature indicated that Rs increased until gravimetric water content (GWC) reached 14 to 15% in tilled treatments and 20% in the mown treatment, subsequently declining, indicating thresholds of GWC at which soil temperature more strongly influences Rs