喀斯特常绿落叶阔叶混交林旱季CO2通量特征及其影响因子

对广西木论国家级自然保护区喀斯特常绿落叶阔叶混交林旱季生态系统CO₂净交换（NEE）的变化特征及其与环境因子的关系进行初步分析,计算研究期间碳汇大小,与其他相似气候条件下的不同生态系统进行对比,以期为准确估算该生态系统的年碳汇量提供基础。利用涡度相关法对该地区旱季（2018年10月1日~2019年3月31日）CO₂通量进行连续观测,同时开展降水量（P）、光合有效辐射（PAR）、空气温度（T_air）、土壤温度（T_soil）以及土壤含水量（SWC）等环境因子监测。观测期内该生态系统CO₂通量及浓度具有明显的"单谷"状日变化特征,白天表现为明显的碳汇,夜间则表现为明显的碳源,NEE在12：00最强,为-0.309±0.330 mg CO₂/（m²·s）,18：30最弱,为0.074±0.061 mg CO₂/（m²·s）;观测期内NEE、生态系统呼吸（Re）、生态系统总生产力（GEP）分别为-121.4、209.2、330.6 g C/m²,该生态系统在2019年2月的碳吸收能力最强,Re、GEP在2018年10月达到最强;光合有效辐射是白天生态系统CO₂净交换（NEE_d）变化的主要控制因素（R²=0.40,p<0.01）,空气温度与夜间生态系统CO₂净交换（NEE_n）存在指数关系（R²=0.1267,p<0.01）;观测期内的降雨抑制了该生态系统的碳汇能力,即降水对NEE产生了抑制作用。旱季该生态系统整体表现出明显的碳汇,碳汇值为1.214 t C/ha,明显低于相似气候条件下的其他生态系统。

CO2 Flux and Its Driving Factors in a Karst Evergreen Deciduous Broadleaf Mixed Forest in Dry Season

The variation of net ecosystem CO₂ exchange (NEE) and the environmental factors was analyzed preliminarily in a karst evergreen deciduous broad-leaf mixed forest ecosystem, Mulun National Nature Reserve in Guangxi, SW China, in dry season to estimate the carbon sinks of the ecosystem during the study period and try to provide a basis for accurately estimating the annual carbon sinks of this ecosystem, in addition, values obtained from other ecosystems under similar climatic conditions were compared. Open-path eddy covariance system was used to continuously measure the CO₂ flux in a dry season from October 1^st, 2018 to March 31^st, 2019. Meanwhile, environmental factors such as precipitation (P), photosynthetic active radiation (PAR), air temperature (T_air), soil temperature (T_soil), and soil water content (SWC) were also monitored. CO₂ flux and concentration have obvious diurnal variation of single-valley shape. NEE is highest at 12:00 with -0.309±0.330 mg CO₂/(m²·s), and is lowest at 18:30 with 0.074±0.061 mg CO₂/(m²·s). The accumulated NEE, Ecosystem Respiration (Re), and Gross Ecosystem Productivity (GEP) during the study period are -121.4, 209.2 and 330.6 g C/m², respectively. The carbon sink capacity of this ecosystem is strongest in February 2019, while, Re and GEP reach the maximum in October 2018. PAR is the main controlling factor for the change of daytime NEE (R²=0.40, p<0.01), and air temperature exponentially correlates with nighttime NEE (R²=0.1267, p<0.01). Precipitation has an inhibitory effect on the carbon sink capacity of the ecosystem. Overall, this ecosystem in dry season performs as a carbon sink with 1.214 t C/ha, that significantly lower than other ecosystems under similar climate conditions.