北京山区不同林分水文生态效应特征

发布时间：2019-02-27 06:41

【摘要】：北京及周边地区森林经营的主要目标是提高森林植被的生态效益,水文生态效应是其重要组成部分。为探索不同森林植被的水文生态效应,本文以北京及周边地区人工林主要建群树种(树种组成)和不同密度结构的典型林分(油松林、元宝枫林、侧柏林和侧柏-黄栌混交林)为研究对象,采用野外定位监测、人工降雨模拟试验、水文模型分析相结合的技术手段,在分析研究区主要气象因子和不同林分的生物量特征的基础上,研究了冠层截留、蒸发散、土壤入渗、地表径流和水量平衡等水文过程及其动态特征。探讨了林分组成、密度结构与林分水文生态过程要素、林分水分利用(固碳)效率的关系,提出了以高效用水和固碳为目标的林分管理技术模式。以期为该地区不同林分的科学管理与经营工作提供理论依据。主要研究内容与结论如下：(1)在林分的生长处在环境承载力的范围内时,林分乔木的生物量会随着林分密度的增加而增加,当林分的生长超过环境承载力的范围时,林分乔木的生物量会随着林分密度的增加而降低(特定林龄条件下)。分析结果表明：阴坡油松林、阳坡油松林、阳坡元宝枫林林分乔木生物量最大时所对应的林分密度分别为3567株/hm2、1985株/hm2、1830株/hm2。(2)基于修正的Gash模型对研究区典型林分的林冠截留量进行了模拟,模型验证结果表明,改进的Gash模型精度可以接受,但受模型结构限制,模型无法及时反映林冠的湿润程度,所以会在连续性降雨或阵性降雨发生时高估林冠截留量的现象。模拟结果表明,大部分林分的冠层截留能力和树干持水能力均随着林分密度的增加而增加,阳坡油松林的冠层截留能力则随着林分密度的增加而降低。(3)人工模拟降雨条件下,枯落物截留量占最大持水能力的比例随着降雨量的增加而增加,当降雨量达到35mm～45mm时,枯落物截留量占最大持水能力的比例达到稳定状态,即达到枯落物的有效持水量,该比例可以用于枯落物有效截留量的估算。(4)利用标准SCS-CN模型对研究区不同林分条件的坡面地表产流进行模拟,通过耦合雨前0-20cm土壤的含水量、LAI、林分密度、下层植被盖度、坡度等因子,构建了不同林分结构和立地条件下的CN值的统计模型,改进后的SCS-CN模型的精度得到的显著提高。(5)本研究采用Brook90生态水文模型模拟不同林分结构条件下生态水文过程,模型的参数率定和检验结果可以接受。模拟结果显示生长季的蒸发散是降雨分配主要的去向,其次为林冠截留和土壤水量变动,最小的水量分配形式为地表径流；不同降雨年型条件下,整体上有冠层截留、地表径流、蒸发散、土壤蓄水量变化等分量均随着降雨的增加而增加,但蒸发散量和土壤层含水量变化量占生长季降雨量的比例变化不大。(6)在本研究涉及的不同坡向和树种条件下,存在对应的林分密度阈值,随着林分密度的增加,在到达该林分密度阂值之前,林分水分生产效率与林分密度呈正相关关系,当林分密度大于该阈值之后,林分水分利用效率则与林分密度呈负相关关系。不同林分(中龄林)的水分利用效率较高时所对应的林分密度(或密度范围)为：阴坡油松林为2100株/hm2,阳坡油松林适宜的林分密度不应小于1746株/hm2；元宝枫林适宜的林分密度范围为2700株/hm2～3000株/hm2。在相同林分密度条件下(1600株/hm2左右),元宝枫林的水分利用效率最大,油松林、侧柏林依次次之。
[Abstract]:The main objective of forest management in Beijing and the surrounding area is to improve the ecological benefit of forest vegetation, and the hydrological and ecological effect is an important part of the forest. In order to explore the hydrological and ecological effects of different forest vegetation, this paper is the study object of the main species of tree species (tree species) and different density structures in Beijing and the surrounding area (Pinus tabulaeformis, Acer truncatum, side Berlin and Platycladus orientalis mixed forest). Based on the technical means of field location monitoring, artificial rainfall simulation test and hydrological model analysis, the canopy interception, evaporation and soil infiltration were studied on the basis of the analysis of the main meteorological factors and the biomass characteristics of different stands. The hydrological processes and their dynamic characteristics of surface runoff and water balance. The relationship between the stand composition, the density structure and the hydrological and ecological process factors of the stand and the efficiency of the water utilization (carbon fixation) of the stand is discussed, and the stand management technology model with high efficiency water and carbon fixation is put forward. So as to provide a theoretical basis for scientific management and operation of different stand in the region. The main research contents and conclusions are as follows: (1) when the growth of the stand is in the range of the environmental carrying capacity, the biomass of the stand tree increases with the increase of the stand density, and when the growth of the stand exceeds the environmental bearing capacity, The biomass of the stand trees decreased with the increase of the density of the stand (under the specific age of the forest). The results showed that the density of the stand was 3567/ hm ~ 2,1985/ hm ~ 2 and 1830/ hm ~ 2, respectively. (2) Based on the modified Gash model, the canopy interception of the typical stand in the study area is simulated, and the model verification results show that the improved Gash model accuracy is acceptable, but is limited by the model structure, and the model cannot reflect the wetting degree of the canopy in time. So that the interception amount of the canopy can be overestimated in the event of continuous rainfall or formation of rainfall. The simulation results show that the canopy interception capacity and the trunk water holding capacity of most stand are increased with the increase of the stand density, and the canopy interception capacity of the pines of the Yangpo pine forest is decreased with the increase of the stand density. (3) Under the condition of artificial simulated rainfall, the proportion of the interception of the litter to the maximum water-holding capacity is increased with the increase of the rainfall, and when the rainfall reaches 35-45 mm, the proportion of the dead-drop interception amount in the maximum water-holding capacity reaches a stable state, that is, the effective water-holding capacity of the dry-falling object is reached, This ratio can be used for the estimation of the effective retention of the litter. and (4) using a standard SCS-CN model to simulate the surface runoff of the slope surface of different stand conditions of the study area, and constructing a statistical model of the CN value under different stand structures and vertical conditions through the factors of water content, LAI, stand density, lower vegetation cover degree and slope of the soil before the coupling rain of 0-20 cm, And the improved SCS-CN model improves the accuracy of the improved SCS-CN model. (5) The study adopted the Brook90 eco-hydrological model to model the ecological hydrological process under different stand structure conditions, and the parameters of the model and the test result can be accepted. The simulation results show that the evaporation of the growth season is the main direction of the rainfall distribution, the second is the interception of the canopy and the variation of the soil water quantity, the minimum water distribution is the surface runoff, and under the condition of different rainfall, the canopy interception, the surface runoff and the evaporation are all over the whole. The changes of soil water storage volume and other components increase with the increase of rainfall, but the amount of evaporation and the change of water content in the soil layer account for the change of the rainfall in the growing season. (6) in the condition of different slope and tree species involved in the study, the corresponding stand density threshold exists, and as the stand density is increased, the water production efficiency of the stand is in a positive correlation with the stand density before reaching the density value of the stand, and when the density of the stand is greater than the threshold, The water use efficiency of stand was negatively correlated with the stand density. The stand density (or density range) corresponding to the high water use efficiency of the different stand (medium-aged forest) is:2100 plant/ hm2 in the cloudy slope, and the suitable stand density of the pines in the sunny slope should not be less than 1746 plants/ hm2; the suitable stand density of the Acer truncatum is 2700/ hm2 to 3000 plants/ hm2. Under the condition of the same stand density (about 1600 plants/ hm2), the water use efficiency of the Acer truncatum forest was the largest, the oil pine forest and the side Berlin were the second.
【学位授予单位】：北京林业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：S715

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