【作者】 赵维军；

【导师】 朱清科； 张岩；

【作者基本信息】 北京林业大学 ， 复合农林学， 2014， 博士

【摘要】 20世纪80年代以来,黄土高原人工造林根据立地类型划分尺度,沿等高线按照一定的等株距等行距布置栽植点,部分栽植点布设在了土壤水分等生境条件较差的位置上,导致坡面人工植被成活率和保存率均较低,甚至形成了“小老树林”,即忽略了坡面微地形及其带来的生境差异。因此,本研究以陕北黄土区坡面微地形及林分为研究对象,选择陕西省延安市吴起县为试验研究区,通过采用三维激光测量、高分辨率遥感影像解译等高技术手段,结合野外实地调查林分数据以及土壤水分、养分数据,利用ArcGIS、标准化降水指数、Mann-Kendall趋势检验以及Ripley’s K函数等空间分析方法,揭示坡面微地形的分布规律,微地形土壤水分养分特征及对近56年来该区域干旱演变特征的响应,最后探讨了微地形对林分生长特征及空间分布格局的影响。结果表明：(1)浅沟、切沟、塌陷、缓台以及陡坎等微地形面积分布差异显著,从大到小依次为：切沟>缓台>浅沟>陡坎>塌陷,其分布规律受坡度、坡向以及土地利用类型的影响较大。(2)雨季,切沟、缓台、塌陷等微地形土壤的集水能力约为陡坎和原状坡土壤的2倍；生长季,陡坎、原状坡的土壤水分对大气降水的依赖性最大,切沟、缓台、浅沟的依赖性居中,塌陷的依赖性最小。(3)切沟、塌陷及缓台等林地的土壤含水量在0-120cm土层变化范围为15%-18%,陡坎林地的土壤含水量在0-80cm土层变化范围为13%-16%；缓台、切沟及塌陷等林地土壤含水量比陡坎微地形出现土壤干层深约40cm。(4)人工林地土壤的速效氮、速效磷、速效钾、全效氮以及有机质等养分含量在不同微地形的变化差异较大,且缓台、切沟、塌陷以及浅沟的土壤养分表聚现象比陡坎的弱。(5)阴坡树种的生长指标与坡位指数呈显著正相关,与坡度指数呈显著负相关；阳坡树种的树高、枯落物厚度与坡度指数呈显著负相关。同一树种在不同微地形上的生长差异显著,林分树种树高随胸径生长速度由大到小依次为：切沟内的刺槐、柳树以及小叶杨>塌陷内的山杏>陡坎上的榆树。(6)微地形内林分单种空间格局的最大聚集半径介于20-30m。均匀坡面在0-l00m空间尺度内,种间空间关联性为显著负相关；在含有微地形的坡面上,刺槐-杜梨、刺槐-山杏、刺槐-小叶杨、刺槐-榆树,以及河北杨-榆树等种间在0-30m空间尺度内为显著负相关变化到60-100m空间尺度内的显著正相关关系,而杜梨-河北杨、杜梨-山杏、杜梨-小叶杨、杜梨-榆树、河北杨-山杏、河北杨-小叶杨以及山杏-榆树等种间则表现为无空间关联性。(7)阴坡造林陡坎以榆树、缓台以山杏、切沟以刺槐为宜,缓台可混交小叶杨、杜梨等树种,切沟可混交河北杨,阳坡造林缓台以刺槐、切沟以榆树为宜。更多还原

【Abstract】 Since the1980s, reforestation was designed according to the site type scale and along the contours with certain planting distance spaced arrangement in the loess plateau. Some plantation points were lainon the poor soil moisture habitat conditions of the slope. It led to the survival rate of artificial vegetation was low in the slope, and even formed a "small old trees", which ignores the effects of microtopography and microhabitat in the slope.Therefore, the soil and water conservation forest and microtopography were selected as the research object, and we considerd Wuqi County as the study area.Combined with the field survey of nutrients and soil water data, the3D laser measurement and high resolution remote sensing image interpretation technology were used, using ArcGIS, standardized precipitation index, Mann-Kendall trend test and Ripley ’K function, to reveal the area distribution of the microtopography and soil water and nutrient characteristics, and the response characteristic to regional drought evolution in recent56years.Finally, the effects of microtopography on growth characteristics and the spatial distribution pattern of forest standswere analyzed.The results showed that:(1)The difference among the area distribution of the microtopography was significant, and the area percentage of differerent microtopography types,from large to small, were gully>platform>ephemeral gully>scarp>sink hole.Meanwhile, the area distribution was effected by slope, aspect and the land use types.(2) The catchment of gully, platform and sink hole was about twice ability of scarp and uniform slope in the rainy season; there was positive correlation between the SPI of growing season and the change value of soil water layer thickness of microtopographies, and the dependence of soil moisture of microtopography with the precipitation, from large to small, was scarp, sunny uniform slope and half sunny uniform slope> gully, platform and ephemeral gully> sink hole.(3) The soil moisture of gully, sink hole and platform ranged from15%to18%at the layer of0-120cm, but that of scarp changed from13%to16%at the layer of0-80cm. The dry soil layers of platform, gully and sink hole appeared at the layer of120-140cm, but that of scarp appeared at80-100cm.(4) The soil nutrient content of available nitrogen, available P, available potassium, total N and organic matters displayed significant difference among the microtopography types, and the soil nutrient content of scarp had obvious topsoil accumulation.(5) In shady slope,height, DBH and litter depth had significantly positive correlations with the slope position index and significantly negative correlations with the slope index; while in sunny slope,height and litter depth had significantly negative correlations with the slope index; Conditions of same tree species in different microtopography types displayed the significant difference, especially,the growth rate of trees height with the DBH displayed the sequence, from large to small:Robinia pseudoacacia Linn., Salix matsudana Koidz and Populus simonii Carr in gully>Armeniaca sibirica Lam. in sink hole>Ulmus pumila Linn. in scarp.(6) The maximal aggregation radiuses of tree species on the microtopography slope fell in20-30m, but those of tree species on the uniform slope were larger than40m; andon the microtopography slope, Robinia pseudoacacia Linn. varied from strong negative association at microtopography scales (0-30m) to positive association (60-100m) with Pyrus betulifolia Bunge, Armeniaca sibirica Lam., Populus simonii Carr.and Ulmuspumila Linn., and Populus hopeiensis Hu&Chow-U. pumilashowed the same association pattern,while the others species pairs including P. betulifolia-P. hopeiensis,P. betulifolia-A. sibirica,P. betulifolia-P. simonii, P. betulifolia-U. pumila, P. hopeiensis-A. sibirica,P. hopeiensis-P. simonii, andA. sibirica-U. pumila showed no association.(7) Ulmuspumila-scarp, Armeniacasibirica+Pyrusbetulifolia and Populussimonii-platform, and Robiniapseudoacacia+Populus hopeiensis-gully could be appropriate forestation pattern in shady slopes respectively.Robiniapseudoacacia-platform and Ulmuspumila-gully could be appropriate forestation pattern in sunny slope respectively.更多还原