Effects Of Broad-leaved Trees Leaf Litter On Soil Chemical Properties Of Needle-leaved Forests In Loess Plateau

Because of simple composition of species, single characteristics of bio-ecological,selective use or absorption to materials, and the special effects on the environment, long-termgrowth or continuous planting of artificial pure forest will lead to soil degradation and soilpolarization, which serious restricts the stability and sustainable development of forest. Thisthesis studied effects of broad-leaved trees leaf litter on soil chemical properties of Pinustabulaeformis and Pinus sylvestris Linn forests in semi-arid and sandy areas of northernShaanxi, Pinus tabulaeformis, Platycladus orientalis and Larix principis-rupprechtii forests insemi-humid loess hilly area of northern Shaanxi and Pinus tabulaeformis and Platycladusorientalis forests in sub-humid ruins of gully region in the north of Weihe river of loessplateau through the method of indoor cultivation by mixing leaf litters and soils together andaimed to guide the local forest management, rapidly determine mixed tree species forplantation and provide theoretical basis for controlling soil degradation and soil polarization.The main conclusions of this thesis were as follows:(1) Long-term continuous growth of needle-leaved forests in loess plateau led part of soilchemical properties to degradation. Significant or very significant soil alkalization and Nshortage happened in all the Pinus tabulaeformis forests in3different regions; Significant soilalkalization happened in Pinus sylvestris Linn forest; Significant K shortage, very significantsoil alkalization and N shortage happened in Larix principis-rupprechtii forest; Verysignificant shortage of humic acid happened in Platycladus orientalis forest in semi-humidloess hilly area of northern Shaanxi and Very significant soil alkalization, significant shortageof organic matter and fulvic acid happened in Platycladus orientalis forest in sub-humid ruinsof gully region in the north of Weihe river.(2) Under the influence of leaf litter decomposing, responsivity of soil chemicalproperties from high to low was humin> fulvic acid>oganic C>available P> humic acid>available N> available K>CEC>pH; responsivity of soil chemical property in semi-arid andsandy areas of northern Shaanxi was much higher than the other two regions; soil chemicalproperty responsivity of Pinus tabulaeformis forest was lower than Pinus sylvestris Linnforest in semi-arid and sandy areas of northern Shaanxi, soil chemical property responsivity of Pinus tabulaeformis, Larix principisrupprechtii, and Platycladus orientalis forest was nearlythe same in semi-humid loess hilly area of northern Shaanxi, soil chemical propertyresponsivity of Platycladus orientalis forest was lower than Pinus tabulaeformis forest insub-humid ruins of gully region in the north of Weihe river.(3) In semi-arid and sandy areas of northern Shaanxi, all of leaf litters were suitable forimproving soil chemical property of Pinus tabulaeformis forest and improving effects wereCaragana microphylla> Hippophae rhamnoides> Populus simonii> Ulmus pumila> Salixmatsudana> Robinia pseudoacia> Amorpha fruticosa; all of leaf litters were suitable forimproving soil chemical property of Pinus sylvestris Linn forest and improving effects werePopulus simonii> Hippophae rhamnoides> Caragana microphylla> Ulmus pumila>Amorpha fruticosa> Salix matsudana> Robinia pseudoacia.(4) In semi-humid loess hilly area of northern Shaanxi, all of leaf litters were suitablefor improving soil chemical property of Pinus tabulaeformis forest and improving effectswere Robinia pseudoacia> Betula platyphylla> Populus simonii> Quercus liaotungensis; allof leaf litters were suitable for improving soil chemical property of Larix principis-rupprechtiiforest and improving effects were Robinia pseudoacia> Quercus liaotungensis> Betulaplatyphylla> Populus simonii; all of leaf litters were suitable for improving soil chemicalproperty of Platycladus orientalis forest and improving effects were Populus simonii> Betulaplatyphylla> Quercus liaotungensis> Robinia pseudoacia.(5) In sub-humid ruins of gully region in the north of Weihe river, leaf litters of all theafforestation trees were suitable for improving soil chemical property of Pinus tabulaeformisforest and improving effects were Hippophae rhamnoides> Caragana microphylla> Quercusliaotungensis> Populus simonii> Robinia pseudoacia; leaf litters of all the roadside treesbesides Acermono Maxim and Magnolia grandi flora were suitable for improving soilchemical property of Pinus tabulaeformis forest and improving effects were Prunuscerasifera>Aesculus parviflora>Koelreteria interifolia> Sophora japonicaLinn.> Salixbabylonica Linn.> Paulownia>Cortex Eucommiae> Ginkgo biloba L.> Platanus hispanicaa>Stercul-iaceae>Ligustrum>Magnolia grandi flora>Acermono Maxim. Leaf litters of all theafforestation trees besides Robinia pseudoacia were suitable for improving soil chemicalproperty of Platycladus orientalis forest and improving effects were Populus simonii>Hippophae rhamnoides> Quercus liaotungensis> Caragana microphylla; Paulownia,Sophora japonica Linn, Acermono Maxim, Prunus cerasifera and Platanus hispanica ofroadside trees were suitable for improving soil chemical property of Platycladus orientalisforest and improving effects were Paulownia> Sophora japonica Linn> Acermono Maxim>Prunus cerasifera> Platanus hispanica. In order to controlling soil degradation and soil polarization, we can carry out leaf litterreplacement near the roots of needle-leaved trees using leaf litters of the suitable broad-leavedtrees as the short-term measure and carry out mixed planting of needle-leaved andbroad-leaved trees as long-term measure.