Study On Rainfall Redistribution Characteristic Of Eucommia Ulmoides Plantation

Xiangxi is economically backward in China, the ecology of this region is fragile and water and soil erosion is serious. Eucommia ulmoides is listed as one of the main afforestation tree species in the forest project construction in Xiangxi because its economic and ecological benefits. Eucommia ulmoides also plays an important role in water conservation and soil maintenance in this region. In this paper, we study the Eucommia ulmoides plantation rainfall redistribution process, further understanding of the relationship of forest vegetation in this area and hydrological process, with the help of surveillance data recorded by Observation and of Cili Ecological Station study of Hunan Academy of forestry. We analyze the Rainfall distributioninfluence on precipitation redistribution, the relationships between the hydrology componentand rainfall, the relationships between features of the hydrology component in different phenology conditions and rainfall, the water holding capacity features of shrub and herb layer and litter layer. The results of our work make sense in sustainable management of Eucommia ulmoides plantations and ecology protection.The total amount of precipitation of research area in2012is1379.6mm. The precipitation changes with seasons. Summer precipitation which accounts for53.55%of total amount is most, while the autumn precipitation is least. The inter-monthly changes of precipitation are also obvious. July is the most while November is the least. The precipitation differs between12.15times. During the seven rainfall degree, the precipitation frequency is most in interval of1-5mm.42.55%of precipitation happens in this interval. The frequency of precipitation is least in>50mm.The annual throughfall, canopy interception, stemflow of the forest is1117.19mm,247.21mm and15.20mm, which accounts for80.98%,17.92%and80.98%of the precipitation respectively. Precipitation redistribution presents the pattern of seasonal change. The maximum values of rainfall, throughfall and canopy interception all appears in July. The critical value of precipitation of stemflow generated by Eucommia ulmoides is0.4mm while the maximum value appears in January in spring. The monthly change trends of stemflow, rainfallandthroughfall are different. The maximum values of stemflow and monthly precipitation do not appear in the same month. In differentrainfall degree, throughfall rate increases withrainfall degree, but canopy interceptionrate decreases. throughfall andcanopy interceptionpresent a significant linear positive correlation with precipitation (R2is0.9971,0.897respectively). the canopy interception rate is significant negative correlated with precipitation (r=-0.384, N=141, P<0.01). stemflow is positive correlated with precipitation (r=0.642, N=141, P<0.01).Eucommia ulmoides phenological stage has a significant influence on precipitation redistribution. throughfall and rainfall present a linear correlation in four phenological stages. The fit parameter R2is located in interval between0.9910and0.9997. The relationship between throughfallrate and waterfall is modeled by quadratic function only in defoliation. Logarithmic function is used to model the relationship in other three periods with R2changing from0.8247to0.8824. The relationship between stemflow and rainfall presents a power function feature in defoliation and dormancy, and R2is0.837. The correlation between canopy interception and canopy interception rate with rainfall in defoliationis low, R2is only0.338. But the R2is located from0.811to0.974in other phenological stages. The equal precipitation in different phenological stages does not mean the same precipitation redistribution. The relationships between each the hydrology component and rainfall are different in different phenological stages.There exist significant differences between species in shrub and herb layer. The maximum water holding capacity per unit area does not equal to the maximum water holding capacity measured by the plant mass itself. Thewater holding capacity of litters increases with the immersion time. The increase is most significant in the first hour of immersion. The water holding rate decreases with the immersion. The degree of decomposition depends on the ability of water holding. The maximum water holding capacity of litters in non decomposing layer is4561.03g·kg-1, while the maximumwater holding rate is456.12%. The maximum water holding capacity of litters in half decomposing layer is1054.86g·kg-1, while the maximumwater holding rate is105.49%.The former is4.32times of the latter.