毛乌素沙地生物结皮覆盖土壤碳通量日动态特征及其影响因子

Diurnal Dynamic Characteristics and Influencing Factors of the Carbon Flux in Biocrusted Soil in Mu Us Sandland

生物结皮是干旱半干旱地区重要的地表景观,它能够进行光合作用和呼吸作用,对荒漠生态系统的碳循环具有重要影响。研究以毛乌素沙地广泛分布的藓类、藻类结皮为研究对象,采用Li-8100土壤碳通量观测系统,探讨了不同类型生物结皮日变化特征及其与环境因子之间关系。结果表明:(1)生物结皮具有较高生理活性时,能够显著降低土壤CO_2通量,藓类结皮的土壤呼吸速率和光合速率均显著(p<0.01)高于藻类结皮。(2)生物结皮光合速率日变化趋势近似为双峰曲线,峰值出现在9:00,16:00左右;生物结皮土壤呼吸速率的日变化趋势呈单峰曲线,于12:00左右达到峰值。(3)相关分析表明,2cm深度处的土壤含水量和空气湿度对生物结皮光合速率影响最为显著;2cm处的土壤温度和含水量对生物结皮土壤呼吸速率影响最为显著。

Biocrust,a community of cyanobacteria,lichens,and mosses that live on the soil surface,is a critical part of land cover types in most arid and semi-arid regions.It can play a significant role in carbon fluxes and exchange in desert ecosystems through their own photosynthesis and respiration.In the present study,we used two dominant biocrust types（moss and algae）found in the Mu Us Sandland.The diurnal dynamic of soil carbon flux under the effects of biocrusts at different succession stages was measured by using a modified LI-8100 automated CO2 flux system,and the effects of environmental factors on photosynthesis and respiration of biocrust were analyzed.The main results include：（1）the biocrust with physiological activity can significantly reduce CO2 flux of soil and both the photosynthetic rate（Pn）and respiration rate（DR）of moss crust were significantly higher（p0.01）than those of the algae crust;（2）the diurnal variation of photosynthetic rate of biocrust was a typical bimodal curve,with the peaks appearing at 9：00 and 16：00;and the diurnal variation of soil respiration rate followed a single-peak curve,with the peaks appearing at 12：00;（3）the correlation analysis result indicated that the soil water content in the depth of 2 cm and air humidity had the most significant effect on the photosynthetic rate of the biocrust;the soil temperature and water content in the depth of 2 cm had the most significant effect on the respiration rate.