江汉平原杨树人工林连栽对林地土壤质量的影响

Impact of Successive Cropping of Poplar Plantation on Soil Quality in Jianghan Plain

采用空间序列代替时间序列的方法，研究了连栽对江汉平原杨树人工林土壤理化性质、微生物数量变化及酶活性的影响。结果表明：与第1代林相比，第2代林土壤物理结构退化，土壤容重增大0．71％，土壤总孔隙度和毛管持水量分别降低0．41％和6．89％，土壤团聚体粒径分布的分形维数增大，土壤平均重量直径减小；土壤有机质、大量元素及微量元素等养分含量均有不同程度下降。连栽导致大量元素下降2．88％～12．20％，其中对N影响最大，K次之，P最小；连栽导致微量元素下降2．27％～53．37％，其中对Zn影响最大，其后依次是Cu、Fe、Mn和S；连栽对土壤微生物数量也有影响，随着连栽代数增加，土壤真菌、放线菌、细菌的数量分别下降34．38％、14．38％、56．63％；第2代林地土壤磷酸酶、脲酶、蔗糖酶、蛋白酶和过氧化氢酶较第1代林分别下降20．00％、11．54％、29．39％、50．00％和1．92％。

The effects of successive plantation cropping on soil physical and chemical and biological characteristics of poplar forest were studied in Jianghan Plain by using space instead of time method. The results showed that firstly, the soil physical structure of the second generation forest（SGF） had a degradation tendencies compared with the first generation forest（FGF）, which included soil bulk density increasing 0. 71%, total porosity and water in capillary porosity decreasing 0. 41% and 6. 89% respectively,and the fractal dimension of soil aggregate getting bigger and the smaller to mean weight diameter. According to soil nutrient changes, secondly, the lower content of organic matter, macro-elements and micro-elements in SGF than in FGF to some extent. It was obviously resulted by successive plantation that macro-element content decreasing 2.88%-12.20%, and soil N element was the most sensitive to successive plantation followed by K and P. Soil micro-elements content decreased 2. 27%-53.37% which sensitive order was Zn, Cu, Fe, Mn and S. Thirdly, it was also decreasing soil microbe quantities for successive plantation that fungous, actinomycial and bacterial numbers cut down 34. 38%, 14. 38% and 56.63% respectively. The similar effected regularity to soil enzyme activities which the activities of phosphatase, urease, sucrase, proteinase and catalase decreased 20. 00%, 11. 54%, 29. 39%, 50.00% and 1.92% respectively in SGF than in FGF.