Effects Of Pastures Leaf Litters On Controlling Soil Polarization Of Pureconifer Forests In Loess Plateau

Nutrient selective utilization and litter special effects are considered to be fundamentalreasons leading to soil polarization in the pure forests. Based on previous studies on soilpolarization of mono-species coniferous forests in the Loess Plateau, anincubation-for-decomposition experiment was conducted of mixtures of soil samples collectedfrom humus layers of Platycladus orientalis, Pinus tabulaeformis and Larixprincipis-rupprechtii forests in the semi-humid loess hilly region of Shaanxi and the humuslayers of Pinus tabulaeformis and Platycladus orientalis pure forest in the Loess Gullied Areawith litters of seven species of forage grass to explore effects of forage litters remedying pureconiferous forest soils and hence to accumulate scientific data for selection of suitablesoil-remedying species of forage grass. Results show that:(1) For the pure forerst in the semi-humid Loess Hilly Area of Northern ShaanxiThe litter of Astragalus adsurgens had the most obvious comprehensive effect mitigatingthe negative polarization of soil form purePlatycladus orientalis forest, followed by Coronillavaria, Leapedeza bicolor and Vicia villosa. Specifically, the negative polarization for the purePlatycladus orientalis forest, all the litters displayed significant effects mitigating the negativepolarization of readily available K; the litters of Medicago sativa, Leapedeza bicolor,Astragalus adsurgens and Vicia villosa had similar effects on the activity of protease.The litter of Medicago sativa had the most obvious comprehensive effect mitigating thenegative polarization of soil form purePlatycladus orientalis forest, followed by Coronillavaria and Melilotus officinalis. Specifically, the negative polarization for the pure Pinustabulaeformis forest, the litters of Medicago sativa, Coronilla varia, Melilotus officinalis,Vicia villosa, Leapedeza bicolor and Astragalus adsurgens displayed significant effectsmitigating the negative polarization of alkalytic N; and the litters of Vicia villosa, Medicagosativa and Melilotus officinalis had similar effects on the available P; and the litters ofMedicago sativa displayed significant effects mitigating the negative polarization of activityof sucrase.The litter of Medicago sativa had the most obvious comprehensive effect mitigating thenegative polarization of soil form pure Larix principis-rupprechtii forest, followed by Melilotus officinalis and Onobrychis viciaefolia. Specifically, the negative polarization for thepure Larix principis-rupprechtii forest, the litters of Leapedeza bicolor, Onobrychisviciaefolia, Astragalus adsurgens, Melilotus officinalis and Coronilla varia displayedsignificant effects mitigating the negative polarization of Organic matter; the litters ofMedicago sativa, Melilotus officinalis, Vicia villosa, Coronilla varia and Astragalusadsurgens had similar effects on the Alkalytic N; the litters of Medicago sativa, Onobrychisviciaefolia, Coronilla varia and Vicia villosa had similar effects on the available P; and thelitters of Leapedeza bicolor, Astragalus adsurgens, Coronilla varia, Vicia villosa, Melilotusofficinalis and Onobrychis viciaefolia had similar effects on the Phosphatas.Thus, based on the point of view of the comprehensive restoration on the polarization ofsoil from pure forests of the semi-humid loess hilly area in Northen Shaanxi, Astragalusadsurgens, Coronilla varia, Vicia villosa and Leapedeza bicolor are suitble forage species tobe planted with P. Orientalis; Medicago sativa, Coronilla varia and Melilotus officinalis aresuitble forage species to be planted with P. Tabulaeformis; and Medicago sativa, Melilotusofficinalis and Onobrychis viciaefolia are suitble forage species to be planted with L.principis-rupprechtii.(2) For the pure forerst in the Loess Gullied AreaThe litter of Medicago sativa had the most obvious comprehensive effect mitigating thenegative polarization of soil form pure Platycladus orientalis forest, followed by Coronillavaria and Melilotus officinalis. Specifically, the negative polarization for the pure Platycladusorientalis forest, the litters of Medicago sativa、 Onobrychis viciaefolia and Melilotusofficinalis displayed significant effects mitigating the negative polarization of Organic matter;the litters of Medicago sativa, Astragalus adsurgens, Leapedeza bicolor and Onobrychisviciaefolia had similar effects on the available P; the litters of Coronilla varia, Vicia villosa,Melilotus officinalis and Medicago sativa had similar effects on the Available K; the litters ofMedicago sativa, Onobrychis viciaefolia and Melilotus officinalis had similar effects on thealkalytic N; the litters of Coronilla varia, Astragalus adsurgens, Vicia villosa, Leapedezabicolor and Melilotus officinalis had similar effects on the Urease; and the litters ofOnobrychis viciaefolia, Coronilla varia and Medicago sativa had similar effects on theBacteria.The litter of Medicago sativa, followed by Onobrychis viciaefolia. Specifically, thenegative polarization for the pure Pinus tabulaeformis forest, the litters of Medicago sativaand Astragalus adsurgens displayed significant effects mitigating the negative polarization ofOrganic matter; the litters of Onobrychis viciaefolia, Melilotus officinalis and Coronilla variahad similar effects on the available P; the litters of Coronilla varia and Vicia villosa had similar effects on the Available K,; the litters of Onobrychis viciaefolia, Astragalus adsurgens,Vicia villosa and Leapedeza bicolor had similar effects on the Sucrase; and the litters ofMedicago sativa and Coronilla varia had similar effects on the Alkalytic N.Thus, based on the point of view of the comprehensive restoration on the polarization ofsoil from pure forests of the Loess Gullied Area, Onobrychis viciaefolia、Medicago sativa andMelilotus officinalis are suitble forage species to be planted with Platycladus Orientalis, andMedicago sativa and Onobrychis viciaefolia are suitble forage species to be planted withPinus tabulaeformis.