木论喀斯特自然保护区土壤微生物生物量的空间格局

土壤微生物是森林生态系统中的重要分解者,在森林生态系统物质循环和能量转换中占有特别重要的地位。以典型喀斯特峰丛洼地为试验对象,利用经典统计学和地统计方法分析了土壤微生物量的空间变异特征。结果表明:土壤微生物量的变异程度均很大,土壤微生物量碳(Cmic)、土壤微生物量氮(Nmic)、土壤微生物量磷(Pmic)的变化范围依次为:44.29—5209.63,20.91—1894.37,0.34—77.06 mg/kg。Cmic、Nmic呈极显著的相关关系,Cmic/Nmic为4.78,明显低于其它生态系统。半变异函数分析表明,Cmic和Nmic的最佳拟合模型为高斯模型,Pmic的最佳拟合模型为球状模型,Cmic/Nmic的最佳拟合模型为指数模型。土壤微生物量的块金值/基台值均介于25%—75%之间,表现为中等空间相关性,说明其受随机因素和结构因素的综合影响。Cmic、Nmic的自相关距离约为50 m,随着滞后距离的增大,自相关函数逐渐向负方向增长,达到显著的负相关。Pmic的Moran’s I在滞后距大于70 m后反而增大,表现为正相关。Cmic/Nmic的Moran’s I较小,在-0.2—0.2之间波动。Cmic、Nmic的空间分布具有很高的相似性,呈凸型片状分布,坡中含量高且向两边递减。Pmic表现为明显不同的分布格局,其在坡中上位和洼地含量较高。Cmic/Nmic呈相反的凹形零星斑块状分布。土壤微生物存在着一定的空间格局,受干扰后其含量急剧降低,因此应加强喀斯特原生生态系统的保护。

Spatial heterogeneity of soil microbial biomass in Mulun National Nature Reserve in Karst area

Soil microbe is the most important decomposer in forest ecosystems, and plays a key role in material recycling and energy conversion. In this study, the spatial patterns of soil microbial biomass in typical Karst peak-cluster depressions were analyzed through both geo-statistical and traditional statistical methods. The results showed that large variation existed in soil microbial biomass. Soil microbial biomass carbon(C_mic), soil microbial biomass nitrogen(N_mic), and soil microbial biomass phosphorus(P_mic) varied from 44.29-5209.63, 20.91-1894.37, 0.34-77.06 mg/kg, respectively. The C_mic was significantly positively correlated with N_mic. The value of C_mic/N_mic is 4.78, which obviously lower than that in other ecosystems. Semivariance analysis revealed that the Gaussian model fitted best for C_mic and N_mic, the Spherical model fitted best for P_mic, and the Exponential model fitted best for C_mic/N_mic. The SH%(C/(C+C₀)×100%) of soil microbial biomass exhibited moderate spatial autocorrelation, ranging from 25% to 75%. Therefore, the spatial patterns were affected by both random and structure factors. The autocorrelation distance of C_mic and N_mic were about 50 m. Moran's I decreased gradually with the increase of separation distance, and showed a statistically negative correlation. Moran's I of P_mic increased when the separation distance was larger than 70 m, which indicated positive correlation. Moran's I of C_mic/N_mic was lower than others, ranging from -0.2 to 0.2 m. The spatial distribution of C_mic and N_mic were similar, and showed a convex-type distribution in which the contents were high in the middle and low on the two sides. In contrast, The P_mic was distributed with a pattern of high in the upper slope and depressions. The content of C_mic/N_mic showed a concave-type distribution with many small patches. We conclude that soil microbes exist in a certain spatial pattern, and that its contents sharply reduced after disturbing. As a result, the protection of Karst primary ecosystems against human disturbing should be strengthened.