不同取样尺度下亚高山草甸土壤呼吸的空间变异特征

基于对4个取样尺度(10、5、2.5、1.25 m)下亚高山草甸土壤呼吸速率的观测,对不同尺度土壤呼吸的空间变异特征进行了研究,分析了不同尺度土壤全氮、有机碳、碳氮比、全硫、土壤温度和土壤水分对土壤呼吸空间异质性的影响,并对各尺度不同置信水平与估计精度下的必要采样数量进行了计算.结果表明:除1.25 m和2.5 m尺度上土壤温度的空间变异属于弱变异外,土壤呼吸及其相关因子的空间变异均属于中等变异,土壤呼吸和土壤温度的变异系数随着取样尺度的增大而增大,而土壤全氮、有机碳、全硫和土壤水分的变异系数随着取样尺度的增大均有减小的趋势;不同取样尺度,影响土壤呼吸的关键因子不同.在10 m尺度,土壤呼吸与土壤全氮、有机碳呈极显著正相关,与土壤温度呈显著正相关,与土壤全硫、碳氮比和土壤水分相关性不显著;在5 m尺度,与土壤全氮和有机碳呈极显著正相关,与土壤全硫、碳氮比、土壤水分和土壤温度相关性不显著;在2.5 m尺度,与土壤有机碳、全氮和土壤水分呈极显著正相关,与土壤全硫、碳氮比和土壤温度相关性不显著;在1.25 m尺度,与土壤全氮、有机碳和土壤水分呈极显著正相关,与碳氮比呈显著负相关,与土壤温度呈极显著负相关,与土壤全硫相关性不显著.随着取样尺度的减小,土壤水分所起的作用逐渐增大,相关系数从0.27~0.49,土壤温度与土壤呼吸的相关性由显著正相关向极显著负相关变化;4个取样尺度95%置信水平误差在10%和20%内必要采样数量分别为28、21、18、14个和7、5、4、4个,随着取样尺度的减小,必需的采样数量减少.

Spatial Heterogeneity of Soil Respiration in a Subalpine Meadow at Different Sampling Scales

At four different sampling scales (10, 5, 2.5 and 1.25 m) we measured soil respiration and the environmental factors affecting soil respiration in a subalpine meadow at Yundin mountain of Shanxi province. The purpose of the paper was to study the spatial heterogeneities of soil respiration and the environmental factors including soil temperature, soil moisture, total nitrogen, organic carbon, ratio of carbon and nitrogen, and total sulfur. Based on those measurements we analyzed the required sampling number at the four scales. The results showed that spatial variations of the soil respiration and environmental factors at all scales were in the middle range but for the soil temperature at 1.25 m and 2.5 m scales; and that the coefficients of variation in soil respiration and soil temperature increased with increasing sampling scale, but for total nitrogen, organic carbon, total sulfur and soil moisture the coefficients of variation decreased with increasing sampling scales. The environmental factors had different impacts on soil respiration at different sampling scales. Simple correlation analysis showed that at 10 m scale the relationship of soil respiration with total nitrogen (P<0.01), organic carbon (P<0.01) and soil temperature (P<0.05) was significant, but not with total sulfur, C/N and soil moisture; at 5 m sampling scale it was highly significant with total nitrogen, organic carbon, but not with total sulfur, C/N and soil moisture and soil temperature; at 2.5 m scale it was highly significant with total nitrogen, organic carbon and soil moisture, but not with total sulfur, C/N, and soil temperature; and at the smallest sampling scale it was highly significant with total nitrogen, organic carbon and soil moisture, negatively significant with C/N, and negatively significant with soil temperature, but not with total sulfur. The required sampling numbers for 10, 5, 2.5 and 1.25 m sampling scales within±10% and±20% of its actual mean at the 95% confidence level were 28, 21, 18, 14, and 7, 5, 4, 4, respectively. The results showed a decreasing trend of required sampling number with decreasing sampling scale.