Abstract
Abstract. The behavior of whole ecosystems in humid climate zone in response to drought is less well documented. Continuous measurements of carbon dioxide and water vapor exchange using the eddy covariance technique during 2003–2007 were made above a subtropical evergreen coniferous plantation in Southeast China. Seasonal distribution of precipitation and temperature was inconsistent during the summer, which resulted in droughts frequently. Gross ecosystem photosynthesis (GEP), ecosystem respiration (RE) and net ecosystem production (NEP) showed clear seasonality, with low rates during droughts and in winter. With statistical significance, the monthly GEP and RE increased exponentially with air temperature, but the monthly NEP was less sensitive and only increased linearly with air temperature. However, the function response of monthly NEP and its components (GEP and RE) disappeared under high temperature and low soil moisture. Monthly and yearly RE showed a statistically linear and positive dependence on the corresponding GEP. Annual NEP varied among years from 306 to 430 g C m−2 (mean 395, SD 50). Interannual variability in NEP was controlled primarily by air temperature and the ratio of precipitation and evapotranspiration that affected the RE/GEP ratio, which varied between 0.76 and 0.81 (mean 0.78, SD 0.02).
Highlights
Not as commonly recognized, it is evident that ecosystem water balances are changing due to altered rainfall and evaporation patterns (Rambal and Debussche, 1995; Waple and Lawrimore, 2003; Reichstein et al, 2007)
The changing precipitation regime accompanying with increased air temperatures has a profound impact on ecosystem carbon exchanges (e.g. Ciais et al, 2005; Niu et al, 2008)
A 30 percent reduction in gross ecosystem photosynthesis (GEP) occurred during 2003 Europe-wide heat and drought, which resulted in a strong anomalous net source of carbon dioxide (0.5 Pg C yr−1) to the atmosphere (Ciais et al, 2005)
Summary
Not as commonly recognized, it is evident that ecosystem water balances are changing due to altered rainfall and evaporation patterns (Rambal and Debussche, 1995; Waple and Lawrimore, 2003; Reichstein et al, 2007). In the future warmer climate with increased air temperatures, future heat waves in areas of Europe and North America will become more intense, more frequent, and longer lasting (Meehl and Tebaldi, 2004). The changing precipitation regime accompanying with increased air temperatures has a profound impact on ecosystem carbon exchanges A 30 percent reduction in gross ecosystem photosynthesis (GEP) occurred during 2003 Europe-wide heat and drought, which resulted in a strong anomalous net source of carbon dioxide (0.5 Pg C yr−1) to the atmosphere (Ciais et al, 2005)
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