硬化地表对油松和白蜡树下非根围及根围土壤微生物量碳氮的影响

硬化地表是城市化发展的重要特征,为了明确硬化地表下土壤环境的变化,以北京典型绿化树油松和白蜡为试验材料,设置透水硬化地表(PP)、不透水硬化地表(IPP)和自然地表(Ctr)3个水平的地表类型,探讨硬化地表对非根围和根围土壤微生物量碳(MBC)、氮(MBN)的影响。结果表明,与对照(Ctr)相比,PP和IPP显著降低了油松和白蜡树下非根围土壤MBC、MBN、MBC/OC(微生物量碳/有机碳)和MBN/TN(微生物量氮/全氮)(P<0.05),并显著降低了油松树下根围土壤MBN/TN(P<0.05);PP显著降低了白蜡树下根围土壤MBN、MBC/OC、MBN/TN和油松树下根围土壤MBC(P<0.05)。硬化地表引起的土壤MBC、MBN的变化与土壤全碳、全氮、有机碳的变化显著正相关(P<0.05),MBN的变化与含水量呈显著负相关(P<0.05)。可见,硬化地表不利于土壤微生物的生长,并且在非根围土壤中表现更为明显,这种不利影响将可能进一步影响城市绿地的养分循环、树木生境和生态系统服务功能。

Effects of pavements on soil microbial biomass carbon and nitrogen in non-rhizosphere and rhizosphere of Pinus tabulaeformis and Fraxinus chinensis

The objective of this study is to evaluate effects of urban pavements on soil microbial biomass in different trees. In-situ simulation test was arranged in the suburb of Changping District, Beijing, China. Pine (Pinus tabulaeformis) and ash (Fraxinus chinensis) were planted at the 1.0 m×1.0 m density in three different treatment plots:pervious brick pavement (PP) with a permeability coefficient of more than 0.4 mm/s, impervious brick pavement (IPP) with a permeability coefficient near zero, and non-pavement for control (Ctr). Topsoil (0-20 cm depth) which includes rhizosphere (tree pool) and non-rhizosphere (0.7 m away from trunk) were analyzed by the chloroform fumigation and extraction methods for soil microbial biomass carbon and nitrogen. The results showed the following:compared to Ctr, the soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), MBC/OC (organic carbon) and MBN/TN (total nitrogen) in non-rhizosphere of pine and ash and MBN/TN in rhizosphere of pine were significantly decreased by PP and IPP treatments. The MBN, MBC/OC, and MBN/TN in rhizosphere of ash and MBC in rhizosphere of pine were reduced by PP treatment. The soil MBC and MBN which were changed by pavements were positively correlated to soil total carbon (TC), TN and OC, and the soil MBN was negatively correlated to soil moisture. In general, pavements adversely affect the soil microorganisms, especially in non-rhizosphere,which may further affect the nutrient cycle, tree habitat, and ecosystem service of urban green space at a large scale.