Dynamic Characteristics Of Soil Water Potential In Larch Forest In Growing Season

Water potential is the main index of soil moisture,which is an important environmental factor for plant growth and development.Xingan larch(Larix gmelini Rupr.)forest is a vegetation zone in northern China.Cold and wet conditions have formed the unique forest ecosystem.By the determination of soil water potential of different depths,environmental factors and growth of new branches of Xingan larch in growing season when May to October,I studied the monthly variations and diurnal variations of soil water potential in Xingan larch forest and its related environmental factors to reveal the mechanism of soil moisture and the growth of Xingan larch.The results show that:(1)The mean value of soil water potential decreased with the increase of depth.The soil water potential of the depth of 20cm and 80cm changes in a large extent,the depth of 40cm and 60cm changes more gently.The 60cm soil water potential values can reflect the soil water potential values in the forest.It is the soil water accumulation period from May to June.In this period,the soil water potential increased with time and decreased with the increase of depths.It is the soil water consumption period from July to October.In this period,the soil water potential decreased with time and increased with the increase of depth.(2)Soil water potential is affected by precipitation,seasonal frozen soil water,soil temperature and air relative humidity in Xingan larch forest during the growing season.Precipitation can be divided into rainfall,snow ablation.May soil water potential in(?)sponse to snow melt water.The correlation between monthly mean value of soil water(?)tential and monthly rainfall decreased with the increase of depth.The regression equation(?)monthly variation of soil water potential in 20cm:Y=0.19X-22.602.With the increase of soil depth,the soil water potential changed slowly to the rainfall response,and the change of soil water potential decreased.The response of soil water potential to heavy rainfall is obvious,and the response of soil water potential to small rainfall is not significant.Seasonal frozen soil is an important environmental factor with regional characteristics,and the soil water potential transfonnation is significantly responsive to(?)asonal frozen soil.When the depth of the seasonal frozen soil is thawed,the depth of the soil water potential rise.Soil water potential is affected by soil temperature,and soil water potential Increased with the increase of soil temperature.The soil water potential of the depth of 20cm in May is saturated.The diurnal variation of soil water potential is mainly related to the seasonal frozen soil and other environmental factors,and there is no obvious relationship between soil water potential and air relative humidity.Diurnal variation of soil water potential at different depths of each other in response to relative humidity.Soil water potential and air relative humidity showed the opposite trend.When the relative humidity decreased,the soil water potential increased and the soil water potential decreased with the increase of relative humidity.(3)Soil water potential of the depth of 80cm had little effect on the growths of new branches of Xingan larch.When the soil water potential of the other layers is larger,the growths of new branches are faster.Soil water potential of the depth of 20cm and 40cm in the rising period of the growth of new branches is greater than the decline of the period.The soil water potential in different layers is the same as that in two periods.the growths of new branches are faster in the period of high water potential.