Precipitation Events, Soil Type, and Vineyard Management Practices Influence Soil Carbon Dynamics in a Mediterranean Climate (Lodi, California)

To characterize the effect of precipitation events, management practices, and soil type on vineyard carbon (C) dynamics, we monitored CO₂ emissions and labile C pools from nine vineyards in Lodi Wine Grape District, California, from April 2011 to December 2012. These commercial vineyards are replicates of three soil series (Redding, San Joaquin, and Tokay), representing a spectrum of soil texture and degree of soil development. We hypothesized that soil characteristics would influence the magnitude of CO₂ efflux occurring in response to precipitation and management events in a Mediterranean climate. During each field visit—bimonthly (April–October) and monthly (November–March)—we measured CO₂, soil temperature, and gravimetric water content (GWC) from vine and intervine (alleys) rows. Monthly, we collected soil samples for dissolved organic C (DOC), which tended to be greater in the alleys of San Joaquin and Redding than Tokay in summer but decreased after the onset of precipitation. In mid-May and mid-October 2012, CO₂ efflux was higher in Tokay than in San Joaquin or Redding. Carbon dioxide efflux across all soils increased as a result of seasonal management practices (i.e., tillage and mowing of cover crops). Management practices distinguished soil DOC between vine rows and alleys from June to October 2012. Soil type or clay content influenced CO₂ efflux across these vineyards, as did GWC and soil temperature. This 20-mo study indicated that CO₂ efflux responded to soil disturbance from management practices, precipitation, and irrigation.