The Research Of Lower Timberline And Soil Moisture In Zagunao River Basin Of The Upper Reaches Of Min River

Based on the soil moisture and soil properties,the paper discussed the spatial and temporal distribution of the lower timberline in the two periods of 1999?2013.Distribution rules and correlations between soil moisture and soil properties of the lower timberline revealed the evolution law between spatial move of the lower timberlines and soil moisture.It provided a theoretical basis for mountain environmental recovery.The main contents and achievements of this paper are as following:(1)The lower timberline mainly concentrated in the upper apart of V-shaped valley with large than 25° slope and altitude ranged from 1700?3200m.The distribution of lower timberlines varied significantly with slope.The southern slope was obviously higher than the northern,and eastern slope was obviously higher than western.The lower timberline had the trend of moved downward.(2)Soil moisture content of woodland ranged from 14.25%?18.65%.Soil moisture content suitable for trees growth should not be less than 18%in shade slope,and 23%in sunny slope,respectively.(3)Soil porosity and water holding capacity of the lower timberline increased firstly and then decreased with increase in elevation.Both the soil porosity and soil water retention in shady slopes were significantly higher than that of the sunny slope.(4)The soil sand content and pH value of woodland decreased with the increasing of the altitude,however soil silt?clay content and C/N showed opposite trends,The soil bulk density firstly decreased and then increased with the increasing of the altitude.The soil sand content and C/N in shady slopes were higher than that of the sunny slope,and the density and pH values were lower in sunny slope.(5)Soil moisture content suitable for trees growth should not be less than 18%with lower timberline of low altitude(moved distance:2250?2400m),and 23%in lower timberline with high altitude(moved distance:2390?2450m).Under the same elevation range,the total soil porosity,soil water retention and C/N with low altitude in the lower timberline were higher than that in the high altitude.The correlation analysis showed that soil moisture and soil properties had significantly positive correlation.The moving of the lower timberline was affected by the changes of soil moisture content.Therefore,the regional vegetation restoration in the Upper reaches of Min River should focus on shade slope and that soil moisture content constraint was not less than 18%.