黄土残塬沟壑区利用阔叶树种枯落叶对针叶林土壤极化的防治效应

EFFECTS OF USE BROAD-LEAVED TREE LITTERS TO CONTROL POLARIZATION OF SOIL UNDER STANDS OF CONIFER FORESTS IN GULLIED LOESS PLATEAU

人工纯林的长期连续生长或连栽所引起的土壤极化是导致土壤退化和影响人工林生态系统稳定及可持续发展的重要原因,防治的根本途径是引入其他树种形成针阔混交林或者利用其他树种枯落叶进行根系附近的局部客置。针对在黄土残塬沟壑区的针叶纯林,通过野外采集典型林地腐殖质层土壤和不同森林和城市道路绿化阔叶树种当年枯落叶后进行室内混合培养试验,研究表明:(1)油松枯落叶会引起土壤有机质、有效磷含量、微生物数量增加和脱氢酶、磷酸酶、多酚氧化酶等多种酶活性增强的正向极化,但同时却会引起土壤碱解氮含量和脲酶、蔗糖酶活性降低的负向极化。与小叶杨和沙棘混交或将其枯落叶客置可以明显改善油松林地土壤性质,而柠条、刺槐和辽东栎则反会恶化土壤性质。客置七叶树、紫叶李、泡桐枯落叶可以明显改善油松林地土壤性质,其次为银杏,而其他树种均不适宜。(2)侧柏枯落叶会引起土壤有效磷、速效钾含量、微生物数量增加和蔗糖酶、脱氢酶、磷酸酶、蛋白酶、多酚氧化酶活性增强的正向极化,但同时却会引起土壤碱解氮含量和脲酶活性降低的负向极化。与辽东栎、刺槐混交或将其枯落叶客置可以明显改善侧柏林地土壤性质,其次是沙棘和柠条,而小叶杨则反会恶化土壤性质。客置玉兰、七叶树、法桐枯落叶可以明显改善侧柏林地土壤性质,其次为杜仲、五角枫,而其他树种均不适宜。该研究结果将对于大面积人工纯林改造、混交林营建等方面具有重要的理论指导和实践意义。

Soil polarization,as a result of long-term cultivation of mono-species tree stands,is the main cause of soil degradation that undermines the stable and sustainable development of forest ecosystems.To control soil poliarization,a fundmental way is to bring in other friendly tree species to form mixed forest or mulch the soil around the tree root with litters from trees of other species.Aiming at the mono-species conifer forests in the gullied leoss plateau,an indoor experiment was carried out incubating litters from different forests and roadside broad-leaved trees in soils collected from the humus layers of forests typical of the region.Results show that（1）litters of Pinus tabulaeformis could promote positive polarization of the soil,that increased the contents of organic matter and available P,and the count of microorganisms and improved the activities of such enzymes as dehydrogenase,phosphatase and polyphenoloxidase,while causing negative polarization that decreased the content of available N and dulled the activities of a few enzymes,such as urease and sucrase.Introducing Populus simonii and Hippophae rhamnoides into P.tabulaeformis forest or mulching the forest soil with their litters could greatly improve properties of the soil,whereas Caragana microphylla,Robinia pseudoacia,and Quercus liaotungensis were not fit for this purpose.However,litters of Aesculus parviflora,Prunus cerasifera,Paulownia fortunei could also significantly improve properties of the soil,and no litters from other species of trees,except from Ginkgo biloba,could.（2）Litters of Platycladus orientalis forest could stimulate positive soil polarization that increased the contents of available P and K,and the count of microorganisms and improved the activities of a number of enzymes such as sucrase,dehydrogenase,phosphatase,protease and polyphenoloxidase.However,they could as well cause negative polarization that decreased the content of available N and the activity of urease.Introducing Q.liaotungensis and R.pseudoacia into Platycladus orientalis forest or mulching the soil with their litters could greatly improve properties of the soil of the P.orientalis forest,and H.rhamnoides and C.microphylla,were also fit for the purpose,whereas P.simonii could only degrade the soil properties.In addition,mulching the forest soil with litters of Magnolia grandiflora,A.parviflora and Platanus hispanica could improve its properties,and litters of Cortex Eucommiae and Acer mono Maxim,could also do,but no litters from other tree species were suitable for the job.The findings of this study would be of some important theoretical and practical significance for modification of artificial mono-species forests and plantation of mixed forests.