Spatial Characteristics Of Soil Enzyme Activities And Soil Nutrient In Different Coniferous Forests Of West Qinling Mountains

The study was conducted at Shaba Forest Experimental Station of West Qinling Mountain located in Xiaolong Mountain. Based on P.tabulaeformis and L.kaempferi plantation with different development stages, different tree species with same ages in coniferous forest and secondary forest as control, we studied soil physicochemical properties, soil enzyme activity of litter decomposed layer and topsoil as well as the relationships between different measured items by field investigation and laboratory analysis. After natural forest was replaced by coniferous plantation, the effect of the succession on soil physicochemical properties and soil biochemical process were discussed. The results showed that:(1) All of nutrient content and enzyme activity were ranked in order litter decomposed layer> topsoil layer in different forest types. pH in litter decomposed layer was lower than that of topsoil in different stands of forest.(2) Under P.tabulaeformis and L.kaempferi plantation stands at different development stages, soil nutrient and the activities of all the other enzyme were decreased at early development stages and increased afterwards with the stands development, except for cellulose activity presented an increase first and then decreased from juvenile to medium plantation, then to nearly mature plantation. The dehydrogenase, sucrase, cellulase as well as acid phosphatase activities in litter decomposed layer of the Pinus tabulaeformis Carr, also were increased at early development stages and decreased afterwards then increased or keep a steady tendency. the chemical properties and enzyme activity in soil showed a greater fluctuation in L.kaempferi stands than in P.tabulaeformis stands from juvenile to nearly mature plantation, suggesting that introduction of L.kaempferi influenced the intensity and direction of soil biochemical process to some extent.(3) Soil pH in stands of different forest types showed a tendency of spruce forest>pinus forest>larch forest, and soil conductivity were ranked in order larch forest>spruce forest>pinus forest. The organic content in soil was the highest in the stand of secondary forest, then in the stand of larch forest, and was the lowest in the stand of Pinus rigida Mill. Total nitrogen content was highest in the stand of secondary forest, and was lowest in the Pinus rigida Mill. Content of available nitrogen in the stand of the Pinus tabulaeformis Carr was higher than others, was low under the stands of secondary forest and Pinus rigida Mill. Soil phosphorus content under the stands of the Larix kaempferi Carr and the picea aspirate Mast was higher, and was lower under the stand of Pinus rigida Mill. Under the stands of different forest types change tendency of enzyme activities in soil were different. Except the cellulase in litter decomposed layer as well as the invertase and the alkalinity phosphatase in topsoil, the other enzyme activities were highest under the stand of secondary forest than the other stands of coniferous forests. Dehydrogenase and polyphenol oxidase activity were higher in the stand of spruce forest. The invertase and cellulase activity involving in soil carbon cycle were higher in the stand of larch forest. In topsoil of different forest type, urease and protease had litter differences. Enzyme activities in the litter decomposed layer were higher under the stand of spruce forest. Under the stand of larch forest the acid phosphatase activity showed a higher value, whereas alkaline phosphatase activity was higher under the stand of spruce forest.(4) In litter decomposed layer, there is a close relationship each other between indicators measured in soil, in which soil organic matter, organic phosphorus with other chemical indicators showed a significant positive correlation. Except there is a significant or highly significant negative correlation between cellulase and polyphenol oxidase, urease, protease, alkaline phosphatase, it was showed that significant positive correlation between the most of soil enzymes. Except there is a low negatively correlation between cellulose and pH, organic matter, total nitrogen and organic phosphorus, soil chemical properties and the other enzymes in soil had significant positive correlation, while no significant correlation was found between available nitrogen, available phosphorus and enzyme activities in soil. In topsoil, there is a lower correlation between indicators measured in soil. A lower correlation was found between soil organic phosphorus and various physical, chemical properties. The relationships between soil enzymes in topsoil were lower than that of litter decomposed layer. The relationships between enzymes activities and physicochemical properties showed there is no relationship between P nutrient and enzymes activities. There was a significant positive correlation relationship between organic matter, total nitrogen and soil enzymes. In short, the most of significant or highly significant correlation were found between all the soil physical, chemical properties and soil enzymes in all forests types, especially closer in that of litter decomposed layer in this study.