Research On The Soil Nutrients Seasonal Dynamics And Its Response To Altitude At The Dry Valley In The Upper Reaches Of The Minjiang River

The soil nutrient is the necessary foundation for forest growing, and also, it plays an important role in the constituent of forest ecosystem. There is a linkage between soil nutrient and vegetation, the soil nutrient provides necessary material base for vegetation existence and development, meanwhile, vegetation reacts soil through the roots and the regression of litter. The soil nutrient exists diversity in various time and space, The time-space continuum of soil nutrient is mainly affected by elevation, vegetation, water and human interference. Based on arid valley of minjiang river area as the research object, through date analysis, we discuss the variability of soil nutrient content at different elevations and relationship between each index. In the meantime, we discuss the interaction mechanism between spatial variability of soil nutrient and vegetation at different elevations, revealing spatical distribution characteristics and variation patterns of soil nutrient in arid valley area ecosystem. Main results are as follows:1)Arid valley area of soil water content as well as in all samples MCWI>MCSP>MCSU >MCAU, with altitudinal gradients and gradually reduce reduced, at the same time, the summer 0-30cm soil moisture content in with soil increases.This because of the summer and autumn rainfall evaporation air temperature is higher, more than for the local choose appropriate afforestation time provided a reference, but also for planting by water greatly restricted along altitudinal gradients provide a gradual recovery from top to bottom of the effective way.2) Soil nutrients in the arid valley area exhibit regularly seasonal variations, except for the ammonium nitrogen content highest in summer and lowest in winter, the other soil nutrients content is dynamic autumn content> winter content> spring content> summer content. From spring to summer, the soil nutrient have 16.49% reduction averagely,54.53% increase from summer to autumn, and 13.68% decrease from autumn to winter, showing that the soil nutrients are greatly influenced by season.3) At the soil profile in arid valley area, the soil nutrient content reduces gradually with the increasing of soil depth, there is average 22.00% reduction from layer T1 to T2, 19.04% decrease from layer T2 to T3, the fall diminish gradually with the deepening of the soil layer, showing obvious accumulation in surface soil. Thereinto, the rangeability of microbial biomass nitrogen is greatest-41.83%, available potassium is least-only 0.26%.4)Study found that the arid valley area of soil nutrient content and converting cropland to forest and closing hillsides to facilitate afforestation, pasture is closely related to the action of returning farmland longer than the sample of short high soil nutrient content, and at the same time, high altitude samples and shrub land grazing interference and man-made interference by the local soil nutrient content is less than the interference of low altitude large intensity was high.5) There is significant correlation among soil Total nitrogen, Total phosphorus, Nitrogen nitrate, Effective phosphorus, Rapidly-available potassium, Hdrolysis nitrogen, Organic carbon, Microbial biomass carbon and Microbial biomass nitrogen, which indicates a interaction and interdependence between soil nutrient along the altitudinal gradients. Meanwhile, soil moisture content and altitude correlate significantly with soil nutrient, so not only soil moisture content is the major limiting factor to local vegetation recovery but also altitude is the vital factor to the soil nutrient distribution. While there is no significant correlation between pH value and soil nutrient, which shows pH value has little influence on distribution of soil nutrient.6) In the arid valley area, soil nutrient is bound up with vegetation growth situation, the vegetation is in good condition at high-altitudes, the soil nutrient content is higher relatively, vegetation restoring plays an important role in protecting and accumulating to the soil nutrients, especially, the soil nutrient content increased signally in some low altitude sample plots since our country have carried out return the grain plots to forestry.