Spatial Distribution Of Meadow Vegetation Root And Its Influencing Facters In Wugong Mountain

Meadow in Wugong mountain is one of the largest grassland ecosystem in south of China,which play a important role in improving land productivity and maintaining the ecological balance.The grassland,however has been severely destroyed due to overgrazing at the end of last century and excessive tourism utilization today.The community and productivity of the meadow are severely degradeg,and mountain meadow fragmentation is presented obviously.The damage of mountain meadow which cause vegetation degradation and loss of couple effect between vegetation and soil will exacerbate the trend of soil and water loss.This paper made meadow in Wugong mountain as the research object to study the interaction between root and soil by field observation and lab analysis.The study including:（1）the relationships between soil and root;（2）the relationship between soil organic carbon and root biomass of five meadow vegetation;（3）The morphological characteristics and response to soil environmental factors;（4）the effects of degradation on root growth,distribution and soil factors;（5）the effects of nitrogen fertilizer,phosphate fertilizer and potassium fertilizer on the root growth of vegetation.In this paper the effects of the different impact factors（soil depth,altitude,community types,degradation and fertilization）on the temporal-spatial evolution of soil and root as well as the mechanism of interaction between root and soil was illustrated,and theoretical basis for protection and restoration of meadow in Wugong mountain was provided.Main result for the study were as follows:（1）Root parameters decreased with the increase of soil depth.About 80%of the roots distributed in 0 to 20 cm soil layer.Power function was fitted between different soil layers and root parameters.Power functions between different soil layers and root parameters（biomass density,root length density and the root surface area density）were y=238x^-1.5559（R²=0.89114）,y=169.9x^-0.88205（R²=0.40836）and y=22.397x^-0.92614（R²=0.36457）,respectively.The content of soil organic matter,total N,total P,available P and available K decreased with the depth of soil in 0 to 40 cm soil layer while the content of total K,available N fluctuated slightly.Correlations between soil nutrients and root parameters differed among nutrients,while organic matter,total N and total K（P<0.05）correlated positively with root parameters.In a word,fertilizing properly at the top soil is beneficial for root development and nutrient uptake.（2）The root biomass density in five meadow vegetation from highest to lowest were Miscanthus sinensis,Arundinella setosa,Fimbristylis dichotoma,Carex chinensis and Fargesia spathacea successively.The root biomass density in 0-20 cm soil layer of five meadow vegetation were significantly highter than the root biomass density in 20-40 cm soil layer;The SOC density of Miscanthus sinensis community was higher than the SOC density of Fimbristylis dichotoma,Carex chinensis and Fargesia spathacea.The SOC density of Arundinella setosa,Fimbristylis dichotoma and Carex chinensis were higher than the SOC density of Fargesia spathacea respectively.The SOC density in 0-20 cm soil layer of five meadow vegetation were significantly highter than the SOC density in 20-40cm soil layer respectively;there were extremely linear positive correlations between SOC density and root biomass density/root biomass carbon density.Root biomass played a key role in SOC content,but it was not the only important element to consider.（3）Root parameters increased with the increase of elevation.Root growth and death developed unevenly during the vegetative period and they changed according to the variation of soil environment（soil temperature and soil moisture content）.the root with diameter of 0-2 mm had the greatest contribution to the root system.Meadow roots in wugong mountain were influenced markedly by the soil temperature and soil moisture content.The effect of altitudinal gradient on root morphological characteristics was regulated by soil temperature and soil moisture content.（4）There were changes of root morphology and distribution,R/S and soil factors affecting root.The root biomass density,root length density and the root surface area density at the degraded meadow were lower than those at the non-degraded meadow in 0 to40 cm soil layer（P<0.05）;The R/S at the degraded meadow were higher than those at the non-degraded meadow in 0 to 20 cm soil layer（P<0.05）;All the soil factors other than soil density were lower at the degraded meadow than at the non-degraded meadow,and soil moisture,soil organic,soil total N,soil avail P,soil total K,soil avail K increased remarkably;Soil moisture,soil avail N and soil Avail P were the mayor factors on root,and soil organic,soil avail P and soil avail K were the primary factors on root.The direct effect on root of the aforementioned soil factors was greater than the indirect effect.（5）Fertilization within a certain range improved root system growth and nutrient absorption.Root length,root surface area and root diameter were suggested to be the important index in the study of effect of root on phosphorus absorption.The application of potassium promoted the increase of soluble sugar content in the root system of meadow vegetation,which was beneficial to improve the resistance of vegetation.In conclusion soil depth,altitude and community type were important factors affecting root growth and distribution in natural state.Soil depth influenced the growth and distribution of the root system by affecting the vertical distribution of soil organic matter and soil nutrients.The effect of altitudinal gradient on root morphological characteristics was regulated by soil temperature and soil moisture content.