黄土高原丘陵沟壑区不同退耕还林模式对土壤微生物的影响

目的]探讨黄土高原丘陵沟壑区不同退耕还林模式对土壤养分和土壤微生物的影响。方法]对甘肃省天水市秦州区退耕还林(草)工程9年后3种不同造林模式和农田对照的土壤养分和土壤微生物数量进行了比较研究。结果]不同退耕模式下,土壤有机碳、全氮、全磷、全钾、速效氮、速效磷和速效钾含量呈逐渐增加的趋势;不同退耕模式下,细菌数量最多,放线菌次之,真菌最少。细菌和放线菌的平均值都是农田对照>经济林型>乔草型>乔木型,而真菌表现为乔草型>乔木型>经济林型>农田对照。土壤三大类微生物数量的垂直变化趋势是随土壤深度增加而降低。结论]不同退耕还林模式提高了土壤养分含量,增强了微生物的活性,促进了主要微生物数量的增加;巩固退耕还林(草)后续工程可改善土壤肥力;乔草型造林模式比单一树种造林模式(乔木型和经济林型)更有利于改善土壤质量。

Effects of Different Models Used in Conversion of Cropland to Forest on Soil Microorganism in A Gully-hilly Region of the Loess Plateau

Objective] To study effects of different afforestation models after 9 years on soil nutrients and microorganism in gully-hilly region of Loess Plateau.Method] The soil nutrient and soil microorganism were compared under 3 afforestation models used in the engineering of returning farmland to forest(grass) in Qinzhou District in Tianshui City of Gansu Province.Result] The results showed that soil organic carbon,TN,TP,TK,AN,AP and AK increased with returning control to agricultural land.There were three principal microbes in the soil,bacteria being the most,followed by actinomycetes and fungi.The order of different components including bacteria and actinomycetes was: cropland control > economic forest > tree and grass types> tree types.In a contrary,fungi showed that tree and grass types> tree types> economic forest> cropland control.The soil microorganism quantity decreased with the increase of soil depth.Conclusion] After returning cropland to forest,soil fertility quality was significantly improved as compared to agricultural land,the activation of microorganism would be accelerated and the main microbial quantity would be increased too.Afforestation of ecological forest is an effective measure for increasing the quality of the soil,mingled forest of tree and grass would be the best example in gully-hilly region at Loess Plateau.