科尔沁沙地自然恢复沙质草地生态系统碳通量特征

Characteristics of Carbon Flux in Sandy Grassland Ecosystem under Natural Restoration in Horqin Sandy Land

以科尔沁沙地围封后自然恢复的沙质草地生态系统为研究对象,基于全年运行的涡动相关系统,观测分析了2017年该生态系统净CO2通量(NEE)在不同时间尺度的变化特征。结果表明:(1)日尺度上,NEE呈“单峰型”,其中生长季(5-9月)出现明显的吸收峰,而非生长季(10月至次年4月)出现明显的排放峰;季节尺度上,NEE表现为吸收峰值和释放峰值交替出现,生长季为碳汇(净吸收202.11 g·m^-2),非生长季为碳源(净释放298.13 g·m^-2);全年尺度上,NEE表现为碳源(净释放96.02 g·m^-2·a^-1)。(2)NEE在生长季与温度(空气温度和土壤温度)呈显著(P<0.01)线性负相关关系,而在非生长季反之;NEE与土壤含水量在生长季和非生长季均呈显著(P<0.01)线性正相关关系;温度和土壤含水量的协同作用对NEE亦有重要影响。

The characteristics of net ecosystem CO2 exchange (NEE) at different time scales were investigated in sandy grassland ecosystem under natural restoration in Horqin Sandy Land, based on the year-round (1 January 2017~31 December 2017) eddy covariance system. The results showed that:1) The monthly mean diurnal variation of NEE changed apparently with a single peak curve;there were obvious absorption peaks during the growing season (from May to September) while obvious release peaks during the non-growing season (from October to April). At the seasonal scale, the absorption peak and the release peak appeared alternately;the growing season was a carbon sink (with a net CO2 absorption of 202.11 g·m^-2), whereas a carbon source for non-growing season (with a net CO2 release of 298.13 g·m^-2). The annual carbon budget of the sandy grassland ecosystem showed a carbon source, with a net CO2 release of 96.02 g·m^-2·a^-1. 2) The NEE was significantly (P<0.01) negatively linearly related to the temperature (both air and soil temperatures) during the growing season, but on the contrary during the non-growing season. However, the NEE was significantly (P<0.01) positively linearly related to the soil water content during both the growing and non-growing seasons. The temperature and soil water content had significant synergistic effect on NEE.