黄土高原不同侵蚀区生物结皮土壤CO_2通量日动态特征及其温度敏感性

Diurnal dynamic characteristics and temperature sensitivity of soil CO_2 flux of biocrusts in different erosion regions on the Loess Plateau

利用LI-8100土壤碳通量自动观测系统监测了黄土高原不同侵蚀区(水蚀区、水蚀风蚀交错区、风蚀区)生物结皮土壤CO2通量的日变化,分析了土壤呼吸的温度敏感性.结果表明:以去除生物结皮为对照,具有生理活性的生物结皮降低了土壤CO2通量,其中,水蚀区、交错区和风蚀区土壤日平均CO2通量分别降低了5.0%、8.9%和20.5%.水蚀区、交错区和风蚀区生物结皮土壤CO2通量日动态均呈单峰型曲线,峰值出现在12:00—14:00左右,大小分别为1.64、1.64和1.37μmol·m-2·s-1,但日变化幅度差异明显.土壤呼吸速率随温度的升高呈上升趋势,指数函数能够较好地描述二者的关系.生物结皮土壤呼吸的温度敏感性指数Q10在空间尺度上存在一定变异,其中,水蚀区、交错区Q10值变化范围为1.93～2.43,而风蚀区Q10值变化范围为4.80～5.56,说明风蚀区生物结皮土壤呼吸对温度的敏感性大于水蚀区和交错区.本研究表明,在探求黄土高原地区土壤碳交换时,应当考虑生物结皮的影响及不同侵蚀区生物结皮土壤CO2通量的差异性.

Biological soil crusts （biocrusts）, as ubiquitous living covers on soil surface in arid and semi-arid regions, exerted a potential effect on soil CO2 flux. In the study, the diurnal dynamic of soil CO2 flux of biocrusts in different erosion regions （water erosion region, water-wind alternated erosion region and wind erosion region） on the Loess Plateau was measured by LI- 8100 automated soil CO2 flux system and the temperature sensitivity of soil respiration was analyzed. The results showed that CO2 flux of soil with activated biocrusts decreased compared with the flux without biocrusts in the three regions. The daily soil CO2 flux with biocrusts was reduced by 5.0%, 8.9% and 20.5% in the water erosion region, water-wind alternated erosion region and wind erosion region, respectively. The soil CO2 fluxes in the daytime showed a simple peak curve. The peak fluxes were observed during 12：00—14：00. The value of CO2 flux in the water erosion region, the water-wind alternated erosion region and the wind erosion region was 1.64, 1.64 and 1.37 μmol · m-2 · s-1, respectively. Soil respiration rate increased along with the rising temperature, and the relationship can be described by an exponent model. The range of temperature sensitivity quotients （Q10） was changed between 1.93 and 2.43 in the water erosion region and in the water-wind erosion region while the range of Q10 values was 4.80~5.56 in the wind erosion region, which indicated that the effect of temperature on biocrusts soil respiration in the wind erosion region was more sensitive than that in the water erosion region and the water-wind erosion region. The study suggested that the effect of biocrusts on soil CO2 flux should be taken into consideration when discussing the soil carbon exchange on the Loess Plateau.