以天宝岩国家级自然保护区长苞铁杉(Tsuga longibracteata W. C. Cheng)林为研究对象,研究了有无倒木覆盖以及倒木腐烂程度对土壤8 项理化指标(包括含水量,容重,总孔隙度,有机碳、全N、全P 和全K 含量以及C/ N比)的影响,并比较了经倒木覆盖后不同季节和不同类型林分中土壤8 个理化指标的变化。结果显示:与无倒木覆盖的土壤相比,经倒木覆盖后土壤容重降低,总孔隙度及含水量提高,有机碳、全N 及全K 含量均增加,说明倒木覆盖总体上提高了长苞铁杉林下土壤的肥力,但有无倒木覆盖对土壤理化性质无显著影响。经不同腐烂程度倒木覆盖后土壤有机碳含量有显著差异(P<0. 05)并随倒木腐烂程度提高大体呈现逐渐升高的趋势,但土壤的其他7 个理化指标无显著差异;经中等(Ⅲ级)腐烂倒木覆盖后土壤的全N、全P 和全K 含量均最高。经倒木覆盖后,不同季节土壤的全P 含量无显著变化,而其他7 个理化指标在不同季节均有显著变化(P<0. 05);经倒木覆盖后秋、冬、春、夏土壤容重和全K 含量依次增加,总孔隙度和有机碳含量依次降低,土壤含水量在秋季最低、春季则最高。整体来看,在长苞铁杉林的不同类型林分内经倒木覆盖后土壤8 个理化指标均有显著差异(P<0. 05);与供试的4 类混交林相比,在长苞铁杉纯林内经倒木覆盖后土壤的含水量、容重和全K 含量均最高,总孔隙度最低,有机碳含量相对较低,C/ N 比及全N 和全P 含量居中。研究结果表明:在天宝岩国家级自然保护区长苞铁杉林内,倒木覆盖有利于改善土壤理化性质、提高土壤肥力。

Taking Tsuga longibracteata W. C. Cheng forest in Tianbaoyan National Nature Reserve as research object, effects of covering with fallen logs or not and decay degree of fallen logs on eight soil physicochemical indexes ( including water content, bulk density, total porosity, contents of organic carbon, total N, total P and total K, and C/ N ratio) were researched, and change of these indexes of soil after covered with fallen logs was compared in different seasons and different type forests. The results show that after covered with fallen logs, soil bulk density decreases, total porosity and water content increase, contents of organic carbon, total N and total K all increase as compared with no covering with fallen logs, meaning that covering with fallen logs generally improve soil fertility under T. longibracteata forest. But there is unsignificant effect of covering with fallen logs or not on soil physicochemical property. After covered with fallen logs at different decay degrees, there is a significant difference (P< 0. 05) in soil organic carbon content with a basically gradually increasing trend as increasing of decay degrees of fallen logs, while there are unsignificant differences in other seven soil physicochemical indexes. Contents of total N, total P and total K in soil covered with fallen logs of moderate decay (Ⅲ class) all are the highest. After covered with fallen logs, there is an unsignificant change in soil total P content in different seasons, while there are significant changes in other seven soil physicochemical indexes in different seasons (P<0. 05). After covered with fallen logs, bulk density and total K content of soil in autumn, winter, spring and summer increase in order while total porosity and organic carbon content decrease in order, and water content of soil is the lowest in autumn and the highest in spring. On the whole, after covered with fallen logs, there is a significant difference (P <0. 05) in eight soil physicochemical indexes in difference type forests of T. longibracteata forest. Comparing with four mixed forests, water content, bulk density and total K content of soil covered with fallen logs in T. longibracteata pure forest all are the highest, while total porosity is the lowest, organic carbon content is relatively low, C/ N ratio and contents of total N and total P are in middle. It is suggested that in T. longibracteata forest of Tianbaoyan National Nature Reserve, covering with fallen logs is beneficial to improving soil physicochemical property and enhance soil fertility.