木论喀斯特自然保护区土壤微生物生物量的空间格局

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

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。

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（Cmic）,soil microbial biomass nitrogen（Nmic）,and soil microbial biomass phosphorus（Pmic） varied from 44.29—5209.63,20.91—1894.37,0.34—77.06 mg/kg,respectively.The Cmic was significantly positively correlated with Nmic.The value of Cmic/Nmic is 4.78,which obviously lower than that in other ecosystems.Semivariance analysis revealed that the Gaussian model fitted best for Cmic and Nmic,the Spherical model fitted best for Pmic,and the Exponential model fitted best for Cmic/Nmic.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 Cmic and Nmic 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 Pmic increased when the separation distance was larger than 70 m,which indicated positive correlation.Moran′s I of Cmic/Nmic was lower than others,ranging from-0.2 to 0.2 m.The spatial distribution of Cmic and Nmic 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 Pmic was distributed with a pattern of high in the upper slope and depressions.The content of Cmic/Nmic 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.