| Larch (larix principis-rupprechtii Mayr.) is the broadest and the most forest growing stock species accumulated in Saihanba mechanical tree farm. In recent years, the Saihanba mechanical tree farm in the higher authority leadership and under various departments' concern and support, has obtained high economy and the social efficiency, and the tourism is also exuberant day by day.This article lives the larch artificial pure crop take the Saihanba mechanical tree farm condition of local growth basic consistent 28 years as the object of study, uses the type place survey procedure, to the different density (respectively was 600,850,1100,1350, 1600·hm"2) under North China fallen leaf pinery stand structure and the soil and water Conservation has conducted the research,The main conclusions are as follows:(1) using the diameter step tree distribution map and the three-parameter Weibull function to describe the different density of larch plantation diameter distribution, by fitting test, when the density was 850·hm-2 old stand approximate diameter Weibull distribution results.(2) when the density is 600 hm"2 and 850 hm-2, the herb arrives at the maximum value highly with the degree of cover, respectively is 35.8cm and 61.1%. Herb species richness in forest density 1350·hm"2, reaches a maximum of 29 species. In the density of stocking is in 1600 hm-2 situations, the bush species number achieves the maximum 6 kinds. In the density of stocking 1350 hm-2 situations, herbaceous species' multiple index H, Pielou uniformity index Jsw, the multiple index D maximizing, respectively is 2.9290, 0.8830,0.9313. In the density of stocking 1600 hm"2 situations, bush species' multiple index H, the multiple indices, Pielou the uniformity index Jsi maximizing, respectively is 1.7201,0.8104,0.9725.(3) the storage of litter and density showed a positive correlation, which increases with the density of the storage of litter also increased. Under different stand density of litter layer and the semi-decomposition does not decompose water absorption rate in different layers is the same. the different level withers and falls the absorbing water speed to have the remarkable power function correlational dependence with its immersion time relationship, the fitting model for the power curve model is the absorbing water speed (a, b is index).Litter of interception by litter size and the quantity, quality, characteristic values of precipitation and drought, and its moisture is closely related to rate. Precipitation in a long time, intensity, litter interception of water by up to saturation, if the rainfall continues will be reduce the rejection rate.(4) The soil bulk density with the density increased first and then decreased, under the different density the soil bulk specific gravity size relations are 1100>850>1350>1600>600 hm-2, capillary porosity, total porosity and the non-capillary porosity with density, the trend is 850> 1350> 110O> 600> 1600 hm-2, when the larch forest density of 850·hm-2, the capillary porosity, total porosity and non-capillary porosity maximum of 63.93%. The soil capillary tube water capacity, the biggest water capacity, the field capacity along with the density change tendency are 1100>1350>1600>850>600 hm-2.Regarding the different density's under prince rupprecht larch forest land, its infiltration rate is 850> 600> 1100> 1350> 1600·hm-2, for the 30-year old larch density retained in the 850·hm-2 its soil and water conservation function better.From different densities of soil chemical properties, when the density is 1100·hm-2, the PH value of soil nutrients and the situation is better.
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