云贵高原喀斯特坡耕地土壤微生物量 C、N、P空间分布

土壤微生物是地球生物演化进程中的先锋种类,具有重要的生态修复功能,但空间分布格局是否存在的争议很大。以云贵高原典型喀斯特坡耕地为对象,基于网格法取样,用经典统计学和地统计学综合分析了土壤微生物生物量的空间变异特征。结果表明,云贵高原喀斯特坡耕地土壤微生物生物量碳(C_mic)、磷(P_mic)以及碳氮比(C_mic/N_mic)适宜,氮(N_mic)的含量较低,变异均很大,空间自相关性明显,最佳拟合模型均为指数模型。块金值C₀较小(0.0016-0.0087),C₀/(C₀+C)均<25%(2.6%-10.2%),变程a较短(22.2-51.0 m),其强烈的空间变异主要由结构性变异引起。Kriging等值线图表明,C_mic、N_mic和C_mic/N_mic的高值区分布在坡的中上部,P_mic的高值区则在坡的中下部和坡脚。云贵高原喀斯特坡耕地土壤微生物不仅存在着小尺度的空间分布格局,而且不同土壤微生物属性的空间分布不同。

Spatial heterogeneity of soil microbial biomass carbon, nitrogen, and phosphorus in sloping farmland in a karst region on the Yunnan-Guizhou Plateau

Soil microorganisms have played a vital role in the evolution of organisms, and have an important function in ecological restoration. However, there is much controversy about whether soil microorganisms show spatial distribution patterns. Many forest types have been destroyed in karst regions around the world, and because of the fragile ecological conditions in such regions, it is difficult to restore their vegetation and ecosystems. Here, we conducted a field study to analyze the soil microbial biomass in typical sloping farmland in a karst region on the Yunnan-Guizhou plateau. We selected a typical area of sloping farmland for the field study. The total area was 340 × 320 m, and it was divided into a 20 × 20 m grid using an Electronic Total Station, giving 294 sample points. We examined the spatial patterns of soil microbial biomass using geo-statistical and statistical methods. The soil microbial biomass carbon (C_mic), soil microbial biomass phosphorus (P_mic), and the ratio of soil microbial biomass carbon to nitrogen (C_mic/N_mic) showed moderate values in this karst region on the Yunnan-Guizhou Plateau. The average values for C_mic,P_mic,C_mic/N_mic were 383.80, 15.41, and 5.61 mg/kg, respectively. There was a low soil microbial biomass nitrogen (N_mic) content (71.50 mg/kg). There was a strong correlation between C_mic and N_mic, but not between C_mic and P_mic,or between N_mic and P_mic. All of these factors showed wide variations in magnitude and differences in their spatial distribution patterns. The variation coefficients for these factors ranged from 39.96 to 87.50%, and the smallest Moran's I result for C_mic,N_mic,P_mic, and C_mic/N_mic was -0.088, -0.0539, -0.060, and -0.093, respectively, indicating that the soil microbial biomass showed a high degree of spatial heterogeneity. The best model for all the four variables in the sloping farmland was an exponential model. The RSS values were very small, indicating the good fit of the model. The nugget (C₀) was low (0.0016-0.0087) and all C₀/(C₀+C) values were less than 25%, indicating that the soil microbial biomass showed strong spatial autocorrelation, and that the spatial patterns of microbial biomass were less influenced by random factors. The spatial patterns in microbial biomass showed a small range (22.2-51.0 m). The ranges of the patterns in C_mic and P_mic were similar (51.0 and 50.1 m), and were greater than that of N_mic (22.2 m). This indicated that the four variables showed strong spatial variability, which was caused by structural variability. The Kriging contour maps showed high values for C_mic, N_mic, and C_mic/N_mic on the middle and upper parts of the slope. On these parts of the slope, C_mic showed a clear spatial distribution pattern but N_mic did not. The plaque was thicker and broken and showed higher heterogeneity on the while slope. The spatial distribution pattern of P_mic was more evident on the middle and lower parts of the slope and the slope foot. Therefore, there is not only a small-scale spatial distributional pattern of the microbial biomass on sloping farmland in the karst region on the Yunnan-Guizhou Plateau, but there are also different spatial patterns in soil microbial variables.