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对 1 962年以来采集的表层土壤和深层土壤样品进行培养实验 ,以研究退耕还林 40年来土壤氮的动态变化以及植被恢复对土壤氮库矿质化的影响 .供试土样在专门设计的矿质化培养系统中 ,以温度 30℃、通气并保持土壤湿度的条件下培养 30d ,以 2mol LKCl溶液浸提培养土并测定其氮含量 .结果表明 ,土壤矿质氮及全氮含量均在造林的头 2 0年迅速下降 ,在 2 0年的林木生长过程中 ,生物吸收积累了土壤中约 80 %— 90 %的有效氮 ,表明耕地中施入的氮对树木早期生长有着重要作用 ;树龄达 40年时 ,土壤原有矿质氮的 5 0 %— 80 %已返还土壤 .这一结果表明 ,森林地被已成为土壤营养的重要来源 ,并且森林生态系统提供的这种有机质可成为可持续利用的土壤氮资源 .
The experiment of surface soil and deep soil samples collected since 1962 was carried out to study the dynamic changes of soil nitrogen and the effects of vegetation restoration on the mineralization of soil nitrogen in the past 40 years since the conversion of cropland to forest for soil samples in specially designed mineral Culture system and cultured at 30 ℃ for 30 days with aeration and keeping the humidity of the soil for 30 days.The contents of nitrogen and nitrogen in soil were measured by 2mol LKCl solution.The results showed that the contents of mineral nitrogen and total nitrogen in soil were in the head of afforestation 20 years of rapid decline in the process of 20 years of forest growth, bioaccumulation accumulated about 80% - 90% of the available nitrogen in the soil, indicating that arable land in the early growth of trees on nitrogen plays an important role; age 40 In 2005, 50% to 80% of the original mineral N in the soil had been returned to the soil, indicating that forestland has become an important source of soil nutrition and that the organic matter provided by forest ecosystems can be made sustainable Soil nitrogen resources.