| Wugong Mountain is located in the central and western Jiangxi Province,with an elevation of 1918.3m.There is a large area of mountain meadow in the high altitude area of Wugong Mountain,and there are obvious shrub-grass ecotone distributed at an altitude of about 1600 m.As the transition area between shrub community and meadow community,ecotone is vulnerable and sensitive from the perspective of ecology.Three slope surfaces with shrub-grass ecotone with different slope directions were selected,and the boundary of shrub-grass ecotone was set as slope position 1,and a slope position was set every 20 m along the slope face upward.Positions 1?3 of the east-facing slope are the under slope region,positions 4?7 are the middle slope region,and positions 8?10 are the upper slope region.Positions 1?2 on the southeast-facing and south-facing slopes are the under slope region,positions 3?4 are the middle slope region,and positions 5?6 are the under slope region.Through the study on the soil physicochemical property of different slope positions in shrub-grass ecotone meadow community,the differences of soil moisture and nutrients among different slope positions were analyzed,and then the main factors affecting the distribution of soil moisture and nutrients were explored through correlation analysis and path analysis.By establishing the regression equation of soil moisture,nutrients and slope position,the spatial pattern changes of soil moisture and nutrients in meadow community at slope scale were revealed,and the main influencing factors of the distribution of shrub and grass ecotone in Wugong Mountain were explained.The aim is to provide scientific basis for ecological restoration and sustainable development of mountain meadow in Wugong Mountain,and to provide theoretical reference for the protection of mountain meadow ecological environment in subtropical area.The results of the study are as following:(1)Through the research on the soil water-holding capacity of each slope of meadow community in shrub-grass ecotone,the maximum holding water capacity,capillary water holding capacity and field water holding capacity in the upper soil of meadow community were 928.41 g·kg-1,850.42 g·kg-1and 716.82 g·kg-1,and those in the lower soil were 784.64 g·kg-1,721.76 g·kg-1and 609.02 g·kg-1.The soil water holding capacity of the meadow community was significantly correlated with its mechanical composition and structural characteristics,soil total porosity,capillary porosity,bulk density,density and organic matter content were the main factors affecting soil water holding capacity,and total porosity had the greatest effect on soil water holding capacity.The looser the soil texture,the higher the content of organic matter,and the stronger the water holding capacity.At the slope scale,the spatial heterogeneity of soil water holding capacity was significant,and the lower the slope position,the better the soil water holding capacity.(2)This paper compared the soil water content of each slope in the shrub-grass ecotone in summer,autumn and winter and found that the soil water content of the meadow community changed obviously in different seasons.The moisture content of the upper soil in summer is 26.53%?45.23%,and that of the lower soil is 27.25%?43.72%.The moisture content of the upper soil in autumn is 31.52%-55.38%,and that of the lower soil is 38.53%-57.44%.The moisture content of the upper soil in winter is 38.82%?72.53%,and that of the lower soil is 42.47%?75.23%.The moisture content of the soil increases gradually from summer to winter.According to the regression analysis,the soil moisture content in three seasons was negatively correlated with slope position.At the slope scale,the farther from the shrub-grass ecotone boundary,the lower the soil moisture content.(3)In the study area,the initial infiltration rate and steady infiltration rate of the upper soil were 11.94?33.96 mm·min-1and 0.35?5.86 mm·min-1,and the lower soil were7.31?23.00 mm·min-1and 0.17?0.83 mm·min-1.The initial soil infiltration rate decreased with the slope position decreasing,but the steady soil infiltration rate did not change obviously at the slope scale.The relationship between soil infiltration capacity and physical and chemical properties is significant,but the main influencing factors of soil infiltration capacity are organic matter content,density,slope position and non-capillary porosity.(4)The effective water content and proportion of soil on each slope of meadow community in shrub-grass ecotone were obtained according to soil withering coefficient.The available water content and proportion of the upper soil in the study area are9.38%?53.52%and 14.41%?45.96%,and the available water content and proportion of the lower soil are 7.18%?36.21%and 11.48%?37.95%.At the slope scale,the lower the slope position,the higher the soil available water content and proportion.The larger the soil porosity,the stronger the water holding capacity,so that the soil available water content and proportion is higher.(5)The nutrient content of soil on each slope of meadow community in shrub-grass ecotone was studied.The contents of organic matter,total nitrogen,total phosphorus and total potassium in the upper soil of meadow community were 66.59?145.55 g·kg-1,1.35?3.73 g·kg-1,1.05?1.54 g·kg-1and 4.26?5.97 g·kg-1,while the contents of nutrients in the lower soil were 55.37?127.63 g·kg-1,1.43?3.67 g·kg-1,1.02?1.71 g·kg-1and 4.26?5.97g·kg-1.Soil is the carrier of nutrients,soil texture and structure characteristics and other conditions determine the nutrient content,the less erosion,the looser the structure of soil,the higher the nutrient content.The total potassium content was stable at each slope position,but the contents of organic matter,total nitrogen and total phosphorus showed significant spatial heterogeneity at slope scale.But overall,the lower the slope position,the higher the nutrient content of the meadow community soil.In conclusion,the distribution of soil moisture and nutrients in the Wugong Mountain meadow community has significant spatial heterogeneity.At the slope scale,the soil water and fertilizer conditions differed significantly,and the lower the slope position,the better the soil water and fertilizer conditions.In other words,the soil under the meadow community in the study area had the best water and fertilizer conditions located at the boundary of shrub-grass ecotone.The soil water and nutrients in the underslope area meet the growth needs of shrub community and form an ecotone of shrub and grass community.According to the text study,the soil moisture and nutrient conditions in the study area are determined by the mechanical composition and structural characteristics of the soil,so the distribution of shrub-grass ecotone in Wugong Mountain is mainly affected by the mechanical composition and structural characteristics of the soil.According to the text study,the soil moisture and nutrient conditions in the study area are determined by the mechanical composition,structural characteristics and topography of the soil. |
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