Ecosystem carbon exchange over a warm-temperate mixed plantation in the lithoid hilly area of the North China

In recent decades, forest area in China increased rapidly by afforestation and reforestation, especially in its temperate parts. However, lack of information on carbon exchange in temperate plantations in China reduced the accuracy of estimation on regional carbon budget. In this study, CO2 flux was measured using the eddy covariance method over a broadleaf dominant mixed plantation in the lithoid hilly area of the North China. The results showed that annual maximum photosynthetic capacity (A(max)) varied from 0.81 to 1.22 mg CO2 m(-2) s(-1) and annual initial light use efficiency (alpha) from 0.014 to 0.026. Net CO2 uptake was depressed when vapor pressure deficit (VPD) was more than 2.5 kPa. Annual temperature sensitivity coefficient (Q(10)) for ecosystem respiration, ranged from 1.84 to 2.35, was negatively correlated with base ecosystem respiration (R-0) (P < 0.05). Annual R-0 decreased but Q(10) increased evidently when winter drought occurred. From 2006 to 2010, annual net ecosystem carbon exchange (NEE), Gross primary productivity (GPP) and ecosystem respiration (R-ec) were -355 +/- 34, 1196 +/- 21 and 841 +/- 43 g C m(-2) yr(-1), respectively. The warm-temperate mixed plantation in the lithoid hilly area of the North China was a strong carbon sink of the atmosphere, which was usually weaken when spring drought happened. (C) 2011 Elsevier Ltd. All rights reserved.