【作者】 高艳鹏；

【导师】 赵廷宁；

【作者基本信息】 北京林业大学 ， 工程绿化学， 2011， 博士

【摘要】 本文以山西省方山县峪口镇土桥沟流域内的人工林(刺槐林、白榆林、油松林、侧柏林、油松—刺槐混交林)为研究对象,通过野外调查、定性与定量分析相结合的研究方法,分析了不同树种、不同密度的林分结构特征和生长特点,对林下植物群落特征、枯落物水文效应以及土壤理化性状做了较深入系统的研究,并且运用主成分分析方法首次对该区的人工林密度效应进行评价,为黄土丘陵沟壑区选择高效的人工林密度配置方式和低效低质残次林改造提供理论依据。结果表明：(1)林木生长特征。在密度相同时,阔叶林的平均胸径大于针叶林。利用Weibull分布函数对所有林分直径进行拟合,结果表明密度为475株/hm2的刺槐林、925株/hm2的刺槐林、925株/hm2的白榆林、1600株/hm2的油松林、550株/hm2的油松—刺槐混交林、1850株/hm2的油松—刺槐混交林不符合Weibull分布,林木直径分布特征数分析结果表明林木直径分布规律性较差,分布曲线均存在偏离正态分布的现象；树高分布主要有单峰或双峰不对称山状分布以及近正态分布。(2)生物多样性。所有草本层物种丰富度和多样性明显高于灌木层。针阔混交林草本层丰富度指数、多样性和均匀度指数最好,其次为刺槐林、油松林,最差的为白榆林、侧柏林；进行聚类分析表明,草本层可分成猪毛蒿(Artemisia scoparia)群系,长芒草(Stipa bungeana)群系,赖草(Leymus scalinu)群系,铁杆蒿(Artemisia gmelini)4个群系；针阔混交林林下物种数量最多,其次是油松林和刺槐林,白榆林生境条件最差；密度相同时,油松—刺槐混交林林下干生物量明显大于其它同密度的林分。(3)枯落物水文效应。不同林分类型枯落物蓄积量的范围为2.36～8.08t/hm2；针阔混交林枯落物蓄积量大于阔叶林,而阔叶林又好于针叶林；针阔混交林枯落物层的最大持水量好于纯林,油松林好于刺槐林、白榆林,最小的为侧柏林；林下枯落物的持水量与浸水时间可以用公式W=klnt+b来拟合,t为时间；林下枯落物吸水速率与浸泡时间可以用公式V=ktn来拟合,t为浸水时间；流域内各林分类型有效拦蓄水深为0.29～1.22mm；针阔混交林枯落物水文效应要好于纯林。(4)土壤物理性质。刺槐林、油松林、侧柏林、油松—刺槐混交林等土壤机械组成的分形维数都比农田小,密度为1150株/hm2和1850株/hm2白榆林分的土壤机械组成的分形维数大于农田；林地土壤容重较农田均有所降低,不同林分类型土壤容重均随深度的增加而增大；刺槐林、油松林的土壤孔隙度和通气度都要好于农田,密度为1150株/hm2和1850株/hm2白榆林、1600株/hm2和1850株/hm2侧柏林、550株/hm2的油松—刺槐混交林孔隙度较差；在刺槐林分中,最大持水量和毛管持水量都好于农田；在白榆林中,密度为925株/hm2林分持水量最好；油松林、侧柏林持水量好于农田；密度相同时,针阔混交林的土壤改良作用好于纯林。在所有林分内,密度为1600株/hm2刺槐林分土壤饱和含水量最大,密度为925株/hm2白榆林分土壤非毛管持水量最高,不同林分土壤涵蓄降水量不同,密度为925株/hm2白榆林分最大,密度为1600株/hm2油松林分有效涵蓄量最大,为383.83mm。(5)土壤化学性质。土壤有机质、全氮、速效氮、速效钾的含量随土壤深度的增加有减小的趋势,有明显的表聚现象；不同的林分,土壤化学性质差异性较大；密度相同时,油松—刺槐混交林的土壤有机质含量、速效磷、速效钾的平均含量>刺槐林>油松林>侧柏林>白榆林,针阔混交林较纯林好；土壤全氮和速效氮平均含量,刺槐林>油松—刺槐混交林>油松林>侧柏林>白榆林。密度为1600株/hm2的刺槐林分土壤质量最好,密度为875株/hm2油松—刺槐混交林次之；最差的林分为密度为1850株/hm2的白榆。(6)密度效应评价。1600株/hm2的刺槐林分密度效应综合评价指数最高,密度为875株/hm2的针阔混交林次之；密度为1150株/hm2和1850株/hm2的白榆林与侧柏林密度效应较差；在林分密度相同时,针阔混交林密度效应综合评价指数要好于纯林。更多还原

【Abstract】 A variety of plantations(Robinia pseudoacacia, Ulmus pumila, Pinus tabulaeformis, Platycladus orientalis, Pinus tabulaeformis and Robinia pseudoacacia mixed forests) were investigated in Tuqiaogou basin, Fangshan County, Shanxi province. Through field survey, qualitative and quantitative analysis, the structure and growth character of forest stands with different species in different density were determined, and plant community feature, hydrological effects of litter, and soil physicochemical properties in the plantations were systematically studied, and plantation density effect was assessed through principal component analysis (PCA). These data were theoretically valuable for selection of artificial vegetation restoration modes and deteriorated forest innovation. The main results are shown as follow:(1) Plantation structure character. The average diameter at breast height (DBH) of broad-leaved forest is bigger than that of evergreen needle-leaf forest at the same stand density. Stand diameter was simulated using Weibull distribution function, and it is shown that Robinia pseudoacacia plantation with density of 925 plants/hm2, Ulmus pumila plantation with density of 925 plants/hm2, Pinus tabulaeformis and Robinia pseudoacacia mixed forests with density of 550 plants/hm2 and 1850 plants/hm2 do not match Weibull distribution. In those plots, the distributions of DBH is in confusion and deviated from normal distribution, while the height distribution shows a single or double peak pattern, or shows normal distribution, and the stand volume increased firstly and then decrease with increasing stand density.(2) Biodiversity. The plant species diversity and richness of herb layer is obviously higher than those of shrub layer. In herb layer, all indexes of richness, diversity and evenness of evergreen conifer and broad-leaved mixed forest are higher than those of pure forests, and Robinia pseudoacacia or Pinus tabuleaformis pure forest is better than Ulmus pumila and Platycladus orientalis pure forest. The species in herb layer are divided into 4 groups according their relations:Artemisia scoparia group, Stipa bungeana group, Leymus scalinu group, and Leymus scalinu group. Evergreen conifer and broad-leaved mixed forest have the most plants, while the habitat condition of Robinia pseudoacacia or Pinus tabuleaformis pure forest is worst. Under the same conditions, the biomass of shrub layer in Pinus tabuleaformis and Robinia pseudoacacia mixed forest is obviously more than other plantation with the same density.(3) The hydro-ecological effects of litter. The litter mass (LM) in different plantation type vary in 2.36～8.08 t/hm2. LM of evergreen conifer and broad-leaved mixed forest is higher than that of broad-leaved forest, and LM of evergreen conifer is the lowest. The maximum water holding capacity (MWHC) of litter layer in evergreen conifer and broad-leaved mixed forest is higher than that of pure forest, in which MWHC of Pinus tabuleaformis pure forest is higher that of Ulmus pumila pure forest and Platycladus orientalis forest is with the lowest one. The relation between water holding capacity of litter and immersion time can be simulated by the following equation:W=klnt+b, in which t was time. And the equation of V=ktn can show the relation between litter absorption rate and immersion time, in which t was immersion time. The modified interception of litter under different stands varys in 2.94～12.22 t/hm2, and the difference of effective interception depth is 0.29～1.22mm. The hydro-ecological effect of litter in evergreen conifer and broad-leaved mixed forest is better than that of evergreen conifer or broad leaved pure forest.(4) Soil physical properties. All the fractal dimensions of soil particle in Robinia pseudoacacia, Pinus tabuleaformis, and Platycladus orientalis pure forest and mixed forest of Robinia pseudoacacia and Pinus tabuleaformis are smaller than that in farmland, while high density Ulmus pumila pure forest is with bigger one. On the contrary, the soil bulk density (SBD) in all kinds of forest is lower than that in farmland, and the SBD increases with increasing the soil depth under all forests. Soil porosities and aeration degrees in Robinia pseudoacacia or Pinus tabuleaformis pure forest are higher that in farmland, while porosities are lower in high density Ulmus pumila or Platycladus orientalis pure forest and low density mixed forest of Robinia pseudoacacia with Pinus tabuleaformis. In Robinia pseudoacacia pure forest, MWHC and capillary water capacity are higher than that in farmland, and water holding capacity in low density forest is higher than that in high density one. Pinus tabuleaformis and Platycladus orientalis plantation have higher water holding capacity than farmland. Under those same conditions, evergreen conifer and broad-leaved mixed forest hold higher capacity to improve soil conditions than pure forest.The Robinia pseudoacacia plantation with density of 1600 plants/hm2 is with the biggest saturated soil water content, and the Ulmus pumila pure forest with density of 925 plants/hm2 holds the biggest non-capillary water-holding capacity. Soil precipitation storage is varied in different plantations, the Ulmus pumila pure forest with density of 925 plants/hm2 is with the biggest one, while the Pinus tabuleaformis pure forest with density of 1600 plants/hm2 holds the biggest available soil water storage of 383.83mm.(5) Soil chemical properties. The content of soil organic matter, total nitrogen, available nitrogen, available kalium decrease with increasing soil depth, and show obvious surface assembly phenomenon. Soil chemical properties are obvious different in different plantations. In the same density stands with different species, the average content of soil organic matter, available phosphor, available kalium show the following order:mixed forest of Pinus tabuleaformis with Robinia pseudoacacia>Robinia pseudoacacia plantation>Pinus tabuleaformis plantation>Platycladus orientalis plantation>Ulmus pumila plantation, in general, evergreen conifer and broad-leaved mixed forest is better than pure forest. However, the average content of total nitrogen and available nitrogen show a different order:Robinia pseudoacacia plantation>mixed forest of Pinus tabuleaformis with Robinia pseudoacacia>Pinus tabuleaformis plantation>Platycladus orientalis plantation>Ulmus pumila plantation.After the conversion of cropland to forest, the soil is better than that in the farmland. The best one is Robinia pseudoacacia plantation with 1600 plants/hm2, and mixed forests of Pinus tabuleaformis and Robinia pseudoacacia with 875 plants/hm2 are better than Ulmus pumila plantation with 1850 plants/hm2.(6) Density effect assessment. Robinia pseudoacacia plantation with 1600 plants/hm2 holds the best comprehensive assessment values, and the evergreen conifer and broad-leaved mixed forests with 875 plants/hm2 is with better ones, and the density effect is worst in height density Ulmus pumila plantation and Platycladus orientalis plantations. In general, the evergreen conifer and broad-leaved mixed forests are better than pure forest under the same conditions.更多还原