林下植被去除与氮添加对樟子松人工林土壤化学和生物学性质的影响

Effects of understory removal and nitrogen addition on the soil chemical and biological properties of Pinus sylvestris var.mongolica plantation in Keerqin Sandy Land

通过析因试验设计,研究了科尔沁沙地樟子松人工林生态系统内土壤无机氮(NO3--N+NH4+-N)含量,潜在净氮矿化(PNM)、硝化速率(PNN),微生物生物量碳(MBC)、氮(MBN)及MBC/MBN,土壤脲酶、酸性磷酸单酯酶活性和土壤有效磷(Olsen-P)含量对林下植被管理(对照和去除)和氮添加(对照和添加8g.m-2)的短期响应.结果表明:林下植被去除显著降低了土壤NH4+-N含量、PNM、MBC和MBC/MBN比值,提高了土壤Olsen-P含量,而对土壤NO3--N含量、PNN和土壤酶活性的影响不显著.氮添加提高了土壤NO3--N含量、PNM和PNN,但对其他指标的影响不明显,可能与试验处理时间较短有关.土壤NH4+-N含量对林下植被去除与氮添加的交互作用的响应显著;而NO3--N含量虽对林下植被去除与氮添加处理的交互作用响应不显著,但在氮添加同时进行林下植被去除的样地中的土壤NO3--N含量比只进行氮添加处理的样地提高了27%,有可能导致土壤中NO3-的淋失.林下植被是影响樟子松人工林土壤化学和微生物学性质的重要因素,因此在森林管理和恢复过程中,不能忽视林下植被的作用.

A full factorial experiment was conducted to study the effects of understory removal and nitrogen addition （8 g . m-2） on the soil NO3--N and NH4＋-N concentrations, potential net nitro- gen mineralization rate （PNM） and nitrification rate （PNN） , microbial biomass C （ MBC ） and N （MBN） , MBC/MBN, urease and acid phosphomonoesterase activities, and Olsen-P concentration in a Pinus sylvestris var. mongolica plantation in Keerqin Sandy Land during a growth season. Un- derstory removal decreased the soil NH4＋-N concentration, PNM, MBC, and MBN/MBN signifi- cantly, increased the soil Olsen-P concentration, but had little effects on the soil NO3^-N concen- tration, PNN, and urease and acid phosphomonoesterase activities. Nitrogen addition increased the soil NO3^-N concentration, PNM and PNN significantly, but had little effects on the other test prop- erties. The interaction between understory removal and nitrogen addition had significant effects on the soil NH4＋-N concentration, but little effects on the soil NO3^-N concentration. However, the soil NO3^-N concentration in the plots of understory removal with nitrogen addition was increased by 27% , compared with the plots of nitrogen addition alone, which might lead to the leaching of NO3^. It was suggested that understory vegetation could play an important role in affecting the soil