[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 samoline scale.