山东省暖性草丛生态系统碳库现状和碳通量季节变化特征

Carbon stock and seasonal dynamics of carbon flux in warm-temperature tussock ecosystem in Shandong Province, China

了解山东省草地生态系统碳库现状和碳通量变化规律对于全国尺度草地生态系统碳源/汇核算有着重要的意义。该研究采用野外面上调查取样和固定加强点静态箱法(LI-840红外分析仪联用)相结合的方法,分析了山东省暖性草丛生态系统的固碳现状、碳通量季节动态以及净生态系统CO_2交换(NEE)对各种环境因子的响应。研究结果表明:山东暖性草丛生态系统平均碳密度为2.74 Mg C·hm^(–2),碳密度的构成排序为土壤碳密度(89%)>生物量碳密度(9%)>凋落物碳密度(2%),山东暖性草丛碳库总储量约为15.88 Tg C;结缕草(Zoysia japonica)暖性草丛生态系统NEE的季节动态总体表现为夏季低,冬季高,非生长季节(11月至次年4月)向外界净排放CO_2,表现为碳源效应;生长季节(4–9月)则为净吸收CO_2,表现为碳汇效应,峰值月份的平均固碳速率在–2.58––4.46μmol CO_2·m^(–2)·s^(–1)之间;2012和2013年泰山小流域暖性草丛NEE年平均值分别为–0.43μmol CO_2·m^(–2)·s^(–1)和–0.31μmol CO_2·m^(–2)·s^(–1),都表现为碳汇效应;光合有效辐射(PAR)、大气温度(Ta)、饱和水汽压差(VPD)和土壤10cm深度温度(Ts)和含水量(W)是结缕草暖性草丛生态系统NEE动态的主要影响因素,但不同月份NEE动态的影响因素各异,且因子间存在着互作效应,主成分分析表明,NEE的季节动态主要受温度、水分和光强等因子控制。

Aims The project was to analyze the carbon stock, seasonal dynamics of carbon flux and the responses of net ecosystem CO2 exchange（NEE） to various environmental factors of Zoysia japonica warm tussock ecosystem in Shandong Province. Methods We used field sampling and fixed-point observation-static chamber method（LI-840 infrared analyzer）. Important findings（1） The average carbon density（carbon stock per area） of Z. japonica warm tussock ecosystem in Yaoxiang small watershed was about 2.74 Mg C·hm^-2 and the order of carbon density was as follows： soil carbon（89%） vegetation carbon（9%） litter carbon（2%）, the total amount of carbon stock of warm tussock in Shandong Province was about 15.88 Tg C.（2） The NEE seasonal dynamics of Z. japonica warm tussock ecosystem was low in summer but high in winter. This ecosystem functioned as carbon source（i.e., CO2 emissions） during the non-growing seasons（October to March of next year）, but acted as carbon sink（net absorption of CO2） during the growing seasons（April to September）. The average carbon sequestration rate during the peak monthswas –2.58– –4.46 μmol CO12·m^-2·s^-1. The annual average NEE of small watershed warm tussock was respectively –0.43 and –0.31 μmol CO2·m^-2·s^-1 in the year of 2012 and 2013, indicating this ecosystem exhibited carbon sink effect.（3） The photosynthetic active radiation（PAR）, atmospheric temperature（Ta）, vapor pressure deficit（VPD） and the temperature and water content of 10 cm soil depth were the major factors regulating NEE dynamics in Z. japonica warm tussock ecosystem, but drivers of NEE dynamics in different months were different and had the interaction effects between factors. Principal component analysis indicated that the seasonal dynamics of NEE was mainly controlled by the temperature, moisture and light intensity.