干旱区盐湖沿岸不同植物群落土壤CO_2排放特征

Characteristic of soil CO_2 emission under different plant communities in the shores of saline lake in arid region

为探究盐湖区不同植物群落土壤CO_2排放速率及影响因素,以新疆达坂城盐湖沿岸小獐毛、鸢尾、芨芨草、黑果枸杞群落和撂荒地土壤为研究对象,在2016年4～12月采用Li–8100A监测了不同植物群落土壤CO_2排放特征,分析了CO_2排放与5(ST5),10(ST10),15cm(ST15)土壤温度、含水量、电导率的关系.结果如下:4～12月小獐毛群落土壤CO_2日排放呈单峰曲线,7月土壤CO_2排放速率最高,峰值出现在14:00左右;7月鸢尾、芨芨草、黑果枸杞和撂荒地土壤CO_2排放呈双峰曲线,峰值出现在10:00和14:00～16:00左右,其余月份均呈单峰曲线,峰值出现在12:00～14:00;不同植物群落类型、同一植物类型不同月份土壤CO_2排放存在显著差异(P<0.001).4～12月芨芨草群落土壤CO_2累积排放量最高(2508.01g/m^2),大于撂荒地(2235.01g/m^2)、鸢尾(1903.03g/m^2)、黑果枸杞(1690.27g/m^2)和小獐毛(550.34g/m^2)植物群落处理.小獐毛群落土壤CO_2排放与ST15显著相关(R^2=0.739,P<0.05),且对ST15变化最敏感;鸢尾、芨芨草、黑果枸杞群落和撂荒地处理土壤CO_2排放与ST5相关性较高(R^2=0.708～0.821),对ST10变化响应敏感.小獐毛群落土壤温度敏感系数(Q_(10))最大值出现在6月(7.97),鸢尾(21.74)、芨芨草(13.21)、黑果枸杞(18.23)和撂荒地(7.65)处理则出现在11,12月.不同植物群落土壤CO_2排放与含水量相关性较低;一元线性方程(loge_cC_f=-0.149EC+0.943)能较好的模拟土壤电导率(EC)与CO_2排放(C_f)的关系.除土壤温度外,盐分也是影响盐湖沿岸土壤碳排放的重要因素.因此,在考虑陆地生态系统碳收支时不能忽略盐湖生态系统,以及盐分对土壤碳过程的影响.

In order to investigate the emission rate of soil CO2 and its influencing factors under different plant communities in arid saline lakes, four plant communities including Aeluropus pungens, Iris tectorum, Achnatherum splendens, Lycium ruthenicum Murr and abandoned land in Danbancheng Saline Lake were selected. The soil CO2 emission rates, under the five plant communities were measured from April to December, 2016 using the LI-8100 A. Meanwhile, the soil temperature in 5, 10 and 15 cm depth, soil water content and electric conductivity were also measured. Results showed that the diurnal variation of soil CO2 emission rate under Aeluropus pungens showed obvious single peak, the highest emission rate happened in July around 14:00. For other plant communities, the emission rates showed the sing peak in 12:00~14:00 in all months except July during which the emission rates had two peaks in 10:00 and 14:00 to 16:00. There were significant difference in the emission rate between different plant communities and among different months under the same plant community(P<0.001). During the research period, the cumulative soil CO2 emission was highest under Achnatherum splendens(2508.01 g/m^2), followed by abandoned land(2235.01 g/m^2), Iris tectorum(1903.03 g/m^2), Lycium ruthenicum Murr(1690.27 g/m^2), and Aeluropus pungens(550.34 g/m^2). The correlation between soil CO2 emission rate and soil temperature in 15 cm depth under Aeluropus pungens was significant(R^2=0.739, P<0.05), and it was sensitive to the changes of soil temperature in 15 cm depth. Under other plant communities, soil CO2 emission rate have highest correlations with soil temperature in 5 cm depth(R^2=0.708~0.821), indicating they are sensitive to the changes of soil temperature in 5 cm depth.Plant communities had great effect on the temperature sensitive of soil CO2 emission(Q10) with largely ranging from 0.60 to 21.74.Values of Q10 was significantly different from April to December. The greatest Q10 under Aeluropus pungens was found at June(7.97),while the highest values under other plant communities were found at November or December: Iris tectorum(21.74), Achnatherum splendens(13.21), Lycium ruthenicum Murr(18.23) and abandoned land(7.65). Regression analysis results showed that the correlation between the CO2 emission(Cf) and the soil moisture was low, the correlation with soil electric conductivity could be modeled(logeCf=-0.149 EC+0.943). Our result also indicated that salinity was an important factor affecting soil carbon emissions among the saline lake. To conclude, the soil carbon process of the saline lake ecosystem in the arid area and the influence of soil salt content on the carbon emissions of the saline lake ecosystem should not been ignored when considering the carbon budget and carbon cycle of the terrestrial ecosystem.