【作者】 高函；

【导师】 吴斌； 张宇清；

【作者基本信息】 北京林业大学 ， 复合农林学， 2010， 博士

【摘要】 为了改善干旱半干旱地区生态环境,各地开展了大面积的植树造林工作。但由于西北地区降水资源匮乏,土壤水储量有限,大面积造林往往造成土壤水环境恶化,致使许多人工林生态系统衰退并功能丧失。本研究在“最大限度防止风蚀的同时尽量减小土壤水分过渡消耗”的前提下,探讨灌木防护林的最佳配置模式以及其合理密度,本研究通过野外观测、野外模拟实验、风洞实验、生物量调查等研究方法进行研究,旨在解决沙区生态建设中柠条防护林建设的配置问题,并为沙区退化草场生态建设提供科学依据。研究结果表明：(1)根据对研究区风沙运动基本参数的律定结果,研究区在观测时期内风力强劲,侵蚀发生频繁,且主要风向为NW、WNW或者NNW。研究区流沙地2m高度起动风速为冲击起动瞬时风速观测值变化于4.73～4.94 m／s之间,平均为4.83 m／s。退化草地起动瞬时风速观测值变化于6.46～6.62 m／s之间,平均为6.54 m／s。退化草地粗糙度在1.61～2.57 cm内,平均粗糙度为2.09 cm,流沙地的粗糙度比较小,流沙地粗糙度在0.37～0.64 cm,平均粗糙度为0.51 cm。在流沙地和退化草地两种不同的下垫面上,风速都随着高度的上升而增加,且两者符合对数相关关系。输沙率随着风速的增加而增加,且二者符合乘幂函数相关关系。(2)单株柠条周围风场基本符合圆柱绕流模型,其防护效应发挥最佳的部位位于植株的中下部,防护范围在背风面2H以内。不同行数林带的防风阻沙效应相比较,三行>双行>单行。其中单行配置防风阻沙能力最弱,三行配置林带略优于双行。不同带距配置的带状柠条林,随着带距的增加,防护效应有所下降。(3)风洞实验结果表明,不同带距柠条林模型防护距离分别是带距4H配置：19H；带距6H配置：15H；带距8H配置：13H；带距10H配置：9H；带距12H配置：8H。风洞实验弥补了野外模拟实验中大气紊流和精度不高的缺陷,是野外观测的支持和补充,二者结果拟合较好,风洞实验方法和材料是有效可行的。(4)通过对不同带距柠条林带间的风场、输沙率进行的野外观测与调查,从不同带距柠条林实际表现论证了模拟实验的可靠性。随着带距的增加,林内输沙率呈上升趋势。(5)不同带距柠条林带间植物多样性分析结果表明,带距越小、带间植物多样性越低。在干旱半干旱区的退化草地营造灌木防护林时,应合理控制带状柠条林带距和盖度,以利于带间草地植被恢复与正向演替。(6)综上所述,通过合理配置,低覆盖度带状柠条林能够满足防风阻沙和植被恢复的需求。在沙区植被建设中应选择双行配置,使其疏透度在0.5左右,带距以8H至10H之间为宜。本研究以沙区人工灌木防护林为研究对象,采用野外实测、野外模拟试验、风洞试验相结合的方法,探索了灌木林的适宜配置规格和密度问题,在研究方法上有一定创新,结果对干旱、半干旱地区防护林建设类型、适宜盖度、配置方式的确定,具有一定的指导意义。更多还原

【Abstract】 There are a lot of large-scale afforestation work in China in order to improve the ecological environment in arid and semi arid areas. However, lack of precipitation and soil moisture reserves in the Northwest region of China limits afforestation area and often results soil degradation of the environment, causing many plantation ecosystem decline and loss of function. On the Premise of "maximum wind erosion control while minimizing excessive moisture consumption", the research discuss most optimum and reasonable coverage of Caragana windbreak using method of field observation, field simulation experiment, wind tunnel experiment and biomass survey. The research purpose is solving the problem of configuration mode and providing scientific basis for ecological construction of degraded grassland in desertification area. The results show as follows.(1) According to determination results of basic aeolian physical parameter, the main wind direction of research area in observation time is NW, WNW or NNW, wind power of research area in observation time strong and frequent. Threshold instantaneous velocity of shifting sandy land changes between 4.73～4.94 m/s,4.83 m/s; threshold instantaneous velocity of degraded grassland changes between 6.46～6.62 m/s, average value 6.54 m/s. Roughness of shifting sandy land changes between 1.61-2.57 cm, average value 0.51 cm; roughness of degraded grassland changes between 6.46～6.62 cm; average value 2.09 cm. Wind speed increases with heigt rising, and they are logarithmic correlation. Sediment transport rate increases with wind speed rising, and they are power function relative.(2) Wind field around per plant shrub is in conformity with flow around cylinder model. The best protective effect of per plant appears on the lower part of lee side. The protected range is within 2 times of plant height (2H) and the effect of shrub on wind finite on 1.5 m height. Effect on windspeed reduction and sand-break by shelterbelt with different number of row is triple rows>double rows> single row in sequence. Effect on windspeed reduction and sand-break by single row is minimum, triple rows shelterbelt is slightly better than double rows. Effect on windspeed reduction and sand-break by shelterbelt with different band spacing decreases with band spacing increasing.(3) The wind tunnel test results show that shelterbelt models with different band spacing have different protective distances. The protective distances of 4H band spacing configuration is 19H; the protective distances of 6H band spacing configuration is 15H; the protective distances of 8H band spacing configuration is 13H; the protective distances of 10H band spacing configuration is 9H; the protective distances of 12H band spacing configuration is 8H. Wind tunnel simulation experiments make up the deficiency of field simulation experiment, such as effect of atmospheric turbulence and low precision. The wind tunnel test is effective supplement and support of field simulation experiment. (4) Reliability demonstration of simulation experiment is done by field survey of wind field and sediment transport rate between shelterbelts with different band spacing, the results show that sediment transport rate increases by band spacing extension.(5) The results of biodiversity analysis between the shelterbelts with different band spacing show that biodiversity and species richness increase while band spacing extension. We should control shelterbelts with reasonable coverage and band spacing in order to promoting vegetation restoration and positive succession.(6)Low coverage belt Caragana Korshinskii kom. Plantation can reduce windspeed and break sand effectively if the shelterbelt is rational allocated.We suggest shrub afforestation in arid and semi arid areas allocates with belts. Recommended row number is 2, recommended transparence degree is 0.5 and recommended belt spacing is 8H～10H.In this study, research object is belt Caragana Korshinskii kom. plantation. Using method of field observation, field simulation experiment, wind tunnel experiment and biomass survey, making a exploration of reasonable configuration mode and coverage of belt Caragana Korshinskii kom. plantation. There is a innovative point of research method. The research results are meaningful to guide the type, configuration mode and reasonable coverage of plantation in arid and semi arid areas.更多还原