林窗对根际和非根际土壤化学性质季节变化的影响

为了解林窗干扰对侧柏林土壤化学性质的影响情况，2012年1月在徐州市九里山东南坡侧柏人工纯林中随机开设27个小、中、大3种尺度的近圆形林窗进行试验，对不同尺度的林窗内根际和非根际土壤的pH、碳、氮等的季节变化进行对比分析。结果表明：林窗降低了根际和非根际土壤含水率，不同尺度林窗内根际与非根际土壤pH均中性偏碱性；根际土壤和非根际土壤的全碳、全氮含量在林窗形成后总体下降；林窗降低非根际土壤C/N，小尺度林窗根际土壤C/N值显著大于对照，小林窗对根际效应的提升更为显著。林窗对土壤C/N值根际效应的影响存在季节上的双反馈作用，林窗尺度、位置会对土壤养分循环造成影响，进而影响林分生产力，开设半径为4 m大小的林窗对林分发育及养分循环最有利。研究结果可为深入了解林窗对土壤养分动态根际效应的作用，揭示林窗干扰对森林生态系统稳定性机理提供一定的参考依据。

Effects of Canopy Gaps on the Physical and Chemical Properties of Rhizosphere and Bulk Soil with Seasonal Changes

In order to understand canopy gap disturbance effects on soil nutrient dynamics in Platycladus orientalis plantations, soil physicochemical properties of pH, carbon and nitrogen in rhizosphere and non rhizosphere soil under 27 different scales of canopy gaps including small, medium and large were studied in southeastern slope of Jiuli Mountain in Xuzhou. The results showed that the water content of the rhizosphere and bulk soil was decreased by canopy gaps. The pH of rhizosphere and bulk soil under different scale canopy gaps was neutral and alkaline. The total content of carbon and nitrogen in rhizosphere and bulk soil decreased after forest canopy gaps formation. Canopy gaps reduced C/N in bulk soil. C/N ratio in rhizosphere soil under small scale canopy gaps was significantly higher than that in control group. This indicates that the effect of canopy gaps on the rhizosphere effect of soil C/N has a double feedback effect with the season. A canopy gap with a radius of 4 m is most favorable for forest development and nutrient cycling. The results can provide a scientific basis for the further understanding of the effect of canopy gaps on soil nutrient dynamics and the ability of forest disturbance to respond to stability mechanism of forest ecosystem.