| Selecting the Platycladus orientalis plantation in Jiulong Mountain as the research object, which is characteristic of natural condition and vegetational status in the rocky mountain of North China, on the basis of setting experimental plots with different structure(different types of canopy closure and under branch height) in the pure forest of Platycladus orientalis, the relationship between stand structure and hydrological function was anlyzed by using the permanent plot method. The hydrological factors, i.e. throughfall,stemflow,canopy interception,litter interception, soil evaporation and soil moisture in various layers of canopy, litter and soil and the forest microclimate factors such as temperature, humidity and illumination are analyzed based on the data measured 2014, and the forest hydrological effects are also studied. The main results fllows as:1. The throughfall rates of under branch height of 1/2 in level of 0.4, 0.6, 0.8 are respectively 76.3%, 67.3%,and 59.2%, their stemflow rate are 4.2%, 2.6%, and 1.7%, and their canopy interception rate are 17.1%, 24.4%, and 34.4%.2. The throughfall rates of under branch height of 1/3 in level of 0.4, 0.6, 0.8 are respectively 78.7%, 73.0%,and 63.9%, their stemflow rate are 3.6%, 2.1%, and 1.4%, and their canopy interception rate are 20.1%, 30.6%, and 39.4%.3. The difference between throughfalls of canopy closure in the same height under branch is not significant tested by analysis of variance. The stemflow of canopy closure 0.4 has significant difference compared with that of 0.8 in each under branch height,and the rest were not significant. The stemflow happens when the rainfall is greater than 5.1mm.4. The canopy interception of under branch height of 1/3 in level of 0.4, 0.6, 0.8 are respectively 1.17,1.25 and 1.14 times of the canopy interception of under branch height of 1/2 in level of 0.4, 0.6, 0.8. The canopy interception in diffrent canopy closure of each under branch height has significant difference.5. The relationship between throughfall and rainfall can be described with the function TF=a P+b, the general equation is TF=0.801P-0.879. The relationship between stemflow and rainfall can be described with the function SF=a P+b, the general equation is SF=0.060P-0.345. The relationship between canopy interception and rainfall can be expresseded with the function Ic=a Pb, the general equation is Ic=0.790P0.536, also can ues the general equation 1.134 1 exp 0.1471.134 c PI Pé ? ?ù=-- +ê? ÷ú?è ??. All equation has high fitting accuracy to be applied for the study areas.6. The relationship between litter interception and rainfall can be described with I=a Pb, the general equation of canopy closure in level of 0.4, 0.6, 0.8 is I=0.765P0.445.7. The parameters of litter interception model and litter interception with throughfall model have much invariable, but the regression model from someone of canopy closure is not fit for description of the codition with another ones, and the limitation of model is obvious, then the factor of canopy closure should be considered carefully when the model is used. The canopy closure factor is introduced into the litter interception model, and the modified litter interception model I=a(PC) b is appropriate to be apllied.8. There are significant positive relationship between litter interception and rainfall, duration, rainfall internsity; and that there are significant negative correlation relationship with the interval, relative humidity; and also that there are no significant relationship between litter interception and temperature, wind velocity.9. The trend of evaporation of soil moisture about different canopy closure and under branch height is consistent,and the magnitude of change is comparely similar, and the difference of evaporation is not significant. Namely the influence on evaporation of soil moisture about different circumstance is not different in this test observation period. The soil water content difference about levels of 10 cm,20cm,30 cm for both in the forest and outside the forest is not significant.10. For the middle-aged Platycladus orientalis plantation in north mountain region, the structure of under branch height of 1/2,and the canopy closure of 0.4-0.6 is the reasonable stand structure, because this type can reduce the canopy interception maximumly and increase soil moisture input,which is can be occurred while considered to maintain the integrity of canopy and stable forest environmental conditions. |
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