Yan WenDe;Xu WangMing;Chen XiaoYong;Tian DaLun;Peng YuanYing;Zhen Wei;Zhang Cao;Xu Jie

National Engineering Laboratory for Applied Forest Ecological Technology in Southern China, Changsha 410004 (China);Forest Ecology Program, College of Life Science and Technology, Central South University of Forestry and Technology, Changsha 410004 (China)

broadleaved forest;carbon;coniferous forest;soil temperature;soil water content

The flux of carbon dioxide (CO₂) from soil surface presents an important component of carbon (C) cycle in terrestrial ecosystems and is controlled by a number of biotic and abiotic factors. In order to better understand characteristics of soil CO₂ flux (FCO₂) in subtropical forests, soil FCO₂ rates were quantified in five adjacent forest types (camphor tree forest, Masson pine forest, mixed camphor tree and Masson pine forest, Chinese sweet gum forest, and slash pine forest) at the Tianjiling National Park in Changsha, Hunan Province, in subtropical China, from January to December 2010. The influences of soil temperature (T_soil), volumetric soil water content ( theta _soil), soil pH, soil organic carbon (SOC) and soil C/nitrogen (N) ratio on soil FCO₂ rates were also investigated. The annual mean soil FCO₂ rate varied with the forest types. The soil FCO₂ rate was the highest in the camphor tree forest (3.53+or-0.51 micro mol m^-2 s^-1), followed by, in order, the mixed, Masson pine, Chinese sweet gum, and slash pine forests (1.53+or-0.25 micro mol m^-2 s¹). Soil FCO₂ rates from the five forest types followed a similar seasonal pattern with the maximum values occurring in summer (July and August) and the minimum values during winter (December and January). Soil FCO₂ rates were correlated to T_soil and theta _soil, but the relationships were only significant for T_soil. No correlations were found between soil FCO₂ rates and other selected soil properties, such as soil pH, SOC, and C/N ratio, in the examined forest types. Our results indicated that soil FCO₂ rates were much higher in the evergreen broadleaved forest than coniferous forest under the same microclimatic environment in the study region.