藓结皮对陕北黄土高原两种质地土壤呼吸的影响

Effects of moss-dominated biological soil crusts on soil respiration in two types of soil in the Loess Plateau of Northern Shaanxi Province,China

使用LI-840便携式土壤碳通量分析仪，测定了黄土高原典型小流域砂土（风沙土）和砂质壤土（黄土）上典型藓结皮与无结皮的呼吸速率，分析两种质地土壤上藓结皮对土壤呼吸的影响。结果显示，在小时尺度上，砂土和砂质壤土上有无藓结皮的呼吸速率均呈单峰型曲线，峰值出现在14：00时，大小分别为2．49和2．66Ixmol·m-2·s-1；相较于无结皮，有藓结皮的两种质地土壤的呼吸速率峰值分别降低了8．6％和5．8％。在日尺度上，有藓结皮的砂土和砂质壤土的日均呼吸速率分别较无结皮降低了9．1％和5．3％，且有藓结皮的砂土日均呼吸速率比有藓结皮的砂质壤土低7．1％。此外，两种质地土壤的呼吸速率与表层2cm土壤温度均呈显著线性相关，表明表层土壤温度是影响生物结皮土壤呼吸的主要因素；同时，藓结皮使表层土壤温度降低0．3～0．5℃，因此推测藓结皮可能会通过降低土壤温度进而影响土壤呼吸速率。研究表明，黄土高原两种质地土壤上广泛发育的藓结皮均能显著降低土壤呼吸速率，其中砂土上的藓结皮更为突出，因此在区域碳通量估算和碳循环研究中应予以充分重视。

The soil respiration rates of sandy soil （ Ust Sandic Entisols） and sandy loam soil （ Los Orthic Entisols） with and without the coverage of moss-dominated biological soil crusts （moss crusts） were measured by a portable CO2 analyzer （LI-840） in a small watershed on the Loess Plateau of China. The effects of moss crusts on soil respiration were determined by the differences of soil respiration rates with and without moss crusts. The results showed that, on hourly scale, the soil respiration rates of the two soils without moss crusts had similar peak values at 14：00, which were 2.49 and 2.66 txmol · m-2 · s-1, respectively. The presence of moss crusts decreased the soil respiration rates of the two soils by 8.6% and 5.8%, respectively. On daily scale, the daily soil respiration rates of the sandy soil and sandy loam soil were 9.1% and 5.3% lower with moss crusts than those without moss crusts, respectively; while with the presence of moss crusts, the daily soil respiration rate of the sandy soil was 7.1% lower than that of the sandy loam soil. In addition, the soil respiration rates of the two types of soil had a significant relationship with sur- face （2 cm） soil temperature, implying that surface soil temperature had important influences on the respiration of the two soils with and without moss crusts. Therefore, we speculated that the moss crusts possibly decreased the soil respiration rate through their effect of decreasing soil sur- face temperature, with an average reduction of 0.3-0.5 ℃ during the experiment. In conclusion,the moss crusts, especially developed on sandy soil, significantly decreased soil respiration on the Loess Plateau of China. Thus, biological soil crusts should be considered in the regional estima- tion of CO2 flux and carbon cycling in the Loess Plateau of China and other similar environments.