密度调控对油松人工林土壤肥力的影响

Effected of Tree Density on Soil Fertility in Pinus tabulaeformis Plantations

2001年,在北京市延庆县营盘村附近中山,对保存密度为3 300株.hm-2的25 a生油松人工林设置27.3%、41.7%、48.5%和57.6%4个间伐强度的处理。4 a后,通过比较土壤物理性质、化学性质和土壤酶的变化,探讨用土壤肥力评价间伐效果的可行性。结果表明:土壤有效磷含量、速效钾含量、毛管孔隙度随间伐强度的增大而增大,非毛管孔隙度与间伐强度成反比。5种土壤酶活性、最大持水量和毛管持水量均以间伐强度48.5%时最大。碱性磷酸酶活性峰值均出现在4月,脲酶活性、有机质含量、速效钾含量、有效磷含量高峰值多出现在10月。脲酶活性谷值均出现在6月,多酚氧化酶、碱性磷酸酶谷值出现在10月。土壤过氧化氢酶活性、碱性磷酸酶活性、脲酶活性、最大毛管持水量和毛管持水量可以作为油松林地土壤肥力评价的指标。用土壤肥力评价间伐效果可行、易测,25 a生保留密度3 300株.hm-2的油松人工林以57.6%左右的间伐强度土壤肥力维持最优。

As the main afforestation tree species in the warm temperature humid and semi-humid climatic region in China,it is important to study the soil fertility and understory vegetation from the aspect of sustainable management for Pinus tabulaeformis plantations.In 2001,the effects of thinning intensities with four different treatments of 27.3%(Ⅰ),41.7%(Ⅱ),48.5%(Ⅲ) and 57.6%(Ⅳ),on the soil fertility were manipulated in the 25-year-old P.tabulaeformis stands with preserved density of 3300 trees·hm-2,in middle hilly lands of Yingpan,Yanqing Country,Bejing.In 2005,whether the thinning effect could be evaluated by soil fertility or not was carried out through the comparison of soil physiochemical properties and soil enzymes in the four stands.The results showed that contrary to non capillary soil porosity,both capillary soil porosity and the content of soil available P and K were enhanced by thinning intensity.However,five types of enzymes,maximum soil moisture capacity and capillary moisture capacity were optimized in the stands with Ⅲ thinning intensities.Also,the maximum activity of alkaline phosphatase was showed in April mostly and that of urease,organic C,available K and available P were in October.For the four stands,the lowest value of urease was exhibited in June,while those of both polyphenol oxidase and alkaline phosphatas were in October.Among the sixteen indexes,soil catalase,alkaline phosphatase,urease,maximum capillary moisture capacity,and capillary moisture capacity could be perceived as indicators to assess soil fertility.Specifically,the method for the evaluation of the thinning effect by soil fertility was feasible and simple.Generally,for the 25-year-old forest with standing density of 3 300 trees·hm-2,the reasonable thinning intensity should be about 57.6%.