【作者】 程杰；

【导师】 呼天明；

【作者基本信息】 西北农林科技大学 ， 草业科学， 2011， 博士

【摘要】 针对黄土高原生态环境建设的需要及草原学、生态学与环境科学研究的前沿性问题,在总结前人相关领域研究的基础上,以可覆盖黄土高原地区的草甸草原、典型草原、荒漠草原和灌丛草原类型区的草地植被分布与气候响应为研究对象,通过对105县有关资料收集、野外样地调查与采样和室内实验与统计分析及科学推断等相结合的研究方法,从系统分析黄土高原不同经度草地植被与气候变化特征入手,研究不同草地植被类型退化与恢复的水分、养分时空变化过程,揭示不同植被地带指示种群与气候变化的响应趋势及空间变异特征,提出黄土高原不同气候带植被恢复建设的调控措施,为实现黄土高原植被生产力的不断提高与持续稳定发展提供基础数据和理论依据,为维持黄土高原生态平衡和人与自然和谐及西部生态环境建设工程提供科学依据和实践指导。主要研究结论如下:(1)研究了黄土高原典型区域主要气候因子与不同植被地带指示种的变化趋势。表明50年来黄土高原半干旱区年降水量总体上呈现出明显减少的趋势, 51年降水量共减少40.31 mm,降幅为7.9 mm/10 a,近10年(1999～2008年)平均降水量仅为392.85mm,比51年平均值减少47.86 mm,下降10.86%,使草原植被破坏已达极限;30年平均温度上升1.2℃,增温幅度为0.4℃/10 a。因受气候暖干化影响,典型指示植物个体分化明显,并向不同地带延伸,使一些优势种逐渐退化为伴生种。(2)揭示了黄土高原草地植被土壤水分的变异特征。在黄土高原经度100°～114°之间,0～100cm土壤水分变异幅度,草甸草原为17.28～24.68%;典型草原为11.7～21.84%;荒漠草原为5.5～17.0%;灌丛草原为13.96～21.26%。草地土壤剖面水分垂直分布趋势总体为:0～30cm受降雨量影响为速变层;30～60cm受降雨强度和土壤容重的影响,为水分利用亏缺层;60cm～100cm受土壤水库的影响,为缓慢回升层。(3)分析了黄土高原草地植被土壤养分的变化状况。在黄土高原不同草原地带土壤养分排序均为草甸草原>典型草原>灌丛草原>荒漠草原地带;各地带草地受封禁年限与不同退化程度的影响,植被生长与土壤养分的变化差异显著,在4种类型草原地带土壤养分均随封禁年限的延长而提高,随退化程度的加重及土层的加深而降低。(4)探讨了黄土高原不同地带草地生产力与气候响应关系。黄土高原从西向东随经度的变化,年降水量相应上升,在经度100°～114°之间,降水量平均由410mm上升到660mm,4种草原类型的生产力随降雨量提高均呈逐渐增强的趋势,且呈极显著的相关性,同时还存在累加效应,这与牧草的生长和需水规律相一致,表明在黄土高原的经度范围,水分是影响草原生产力的首要驱动因子。(5)揭示了黄土高原典型种群与气候变化响应特征。近年来受全球气候变化的影响,草地种群对气候反应较为敏感,其分布幅度在逐渐扩大。草甸草原以白羊草为代表的4个典型种群,已由该地带建群种扩展为典型草原优势种。典型草原10个种群可分为3种类型,以禾本科为主的旱生中旱生植物,从草甸草原到典型草原均有分布;以菊科为主的旱生及旱中生植物,已由典型草原地带向草甸草原和荒漠草原地带扩展;以豆科和其它科为主的中旱生植物,不仅为典型草原地带的建群种,且已延伸到荒漠草原地带,表明气候暖干化的变化趋势在加剧。荒漠草原4个典型种群不仅成为该地带的建群种,且已延伸到草原化荒漠地带与极干旱植物驴驴蒿等混生组成群落。灌丛草原7个种群,适宜草甸草原生长的白刺花等种群已扩展到典型草原以优势种出现;典型草原地带生长的柠条锦鸡儿等种群已扩展到荒漠草原地带以优势种出现;荒漠草原地带的杠柳等种群已伸展到典型草原与荒漠草原交错区以伴生种或偶见种出现。以上种群分布均为气候变化的指示信号和重要标志,为我国气候变化与物种多样性及种群分布格局的研究提供了重要科学依据。(6)研究发现黄土高原草地植被地带迁移趋势明显。根据植被地理分布、植物区系成分、环境条件以及目前植被分布状况,结合黄土高原植被调查研究与文献资料考证,由于现代气候具有向暖干化发展趋势,加之人类活动对植被的重复破坏,致使森林草原地带的分界线向南退缩,典型草原地带分界线在不断扩大,向南迁移直接进入森林草原地带,而荒漠草原也在不断南移,伸入到典型草原地带,出现了目前黄土高原森林草原地带、典型草原地带和荒漠草原地带镶嵌分布的植被群落类型表现较为明显。更多还原

【Abstract】 Taking into account frontier problems that the eco-environmental construction of the Loess Plateau involve in grassland science, ecology and environment sciences, depending on the summarization of previous relevant research achievements, taking grassland vegetation distributions and their climatic responses of the meadow, typical, desert and scrub grasslands distributing in the loess Plateau as its subjects, and proceeding from the angle of grassland vegetations and climatic variations against different longitudes in the loess Plateau, the study collected relevant data of 105 counties by field survey and sampling, lab and statistic analysis and scientific deduction and probed into temporal and spatial water and nutrient variations during the degeneration and rehabilitation of the different types of grasslands according to the data, with the purpose of revealing climatic response and spatial variation patterns of indicator species in different vegetation zones, putting forward regulating measures for rehabilitating different vegetations under the different climatic zones in the loess plateau, and providing basic data and theoretical basis for sustainably and stably improving the vegetation productivity as well as scientific and theoretical guidance for maintaining the ecological balances, human beings-nature harmony in the loess plateau and carrying out eco-environment construction projects for West China. The main results and conclusions of the study were as follows:(1) The study investigated the tendencies of major climatic factors of typical regions and different indicator species of the grasslands in the loess plateau. It revealed that in the past fifty years the annual rainfall of the semi arid regions of the loess plateau generally tended to decline with its decrements totaling 40.31 mm, averagely 7.9 mm every 10 years, and in the latest ten years, its annual rainfall amounted to only 392.85mm, reducing 47.86mm by 10.86% compared with its annual rainfall in the past fifty years, so that the grassland vegetation damage reached its extreme; in the latest thirty years, its average annual temperature increased 1.2℃, averagely 0.4℃every ten years. It appeared obvious that because of global climatic drying, the typical indicator species varied in their roles and that spread into the other grasslands so as to cause some dominant species to gradually become companion ones.(2) The study revealed the characteristics in soil water variations of the different grasslands in the loess plateau. In the loess plateau, where the longitude ranged within 100°～ 114°, the 0～100cm soil water contents of the meadow, typical, desert and scrub grasslands varied within17.28～24.68%, 11.7～21.84%, 5.5～17.0% and 13.96～21.26%, respectively; the different soil layers of the grasslands presented different soil water variations: the 0～30cm soil presented a soil water content that varied rapidly because of the rainfall, thus a layer where the soil water was quick to change ; 30～60 soil suffered water deficiency arising from water use because of the influence of the rainfall intensity and the soil bulk weight, thus a layer that suffered water deficiency ; The soil below 60～100cm deep was slow to recover its water because of the soil water reservoirs, thus a layer where the soil water was slow to recover.(3) The study examined soil nutrients of the grasslands in the loess plateau. In the loess plateau , the soil nutrients of the different grasslands ranked in the order of meadow grassland>typical grassland>scrub grassland>desert grassland ; Because the different grasslands had different grazing-prohibiting periods and degeneration degrees, their vegetation growths and soil nutrients significantly differed, all the four steppes increasing their soil nutrients as their grazing prohibiting periods prolonged and decreasing their nutrients as their degeneration degrees and soil depths increased.(4) The study probed into the productivities and climatic responses of the different grasslands in the loess plateau. In the loess plateau, the rainfall increased as the longitude increased from west to east; and the rainfall increased from 410mm to 660mm as the longitude increased from 100°to 114°, the productivities of the four grasslands correspondingly tended to gradually increase and appeared extremely significantly correlated with the rainfall variation and that the effects of the rainfall on the productivities were additional. This corresponded with the growths and water requirement patterns of the grasslands, which indicated that within the longitude range of the loess plateau, water was the primary driving factor affecting the grassland productivity.(5) The study revealed typical species and their response characteristics to climatic changes in the loess plateau. In the recent years, because of the influences of global climatic changes, the grassland species appear sensitive and their distributions are gradually expanding. The Bothriochloa ischcemum keng-represented four typical species of the meadow grassland had transformed from edificator species into typical grassland dominant species. The ten species of the typical grassland could be divided into three types, gramineae-dominant xerophytes and mesoxerophytes, which distributed in both the meadow and typical grasslands; Compositae dominant xerophytes and mesoxerophytes, which expanded from the typical grassland into the meadow and desert grassland; mesoxerophytes over which legumes and other plant families dominated , which were not only the edificator species of the typical grassland but also expanded into the desert grassland, which indicated that the climatic drying got intensified. The four typical species of the desert grassland were not only its own edificator species, but also expanded into desertifying grassland areas and mixed communities composed of such extreme xerophytes as Artermisia Dalailamae. Among the seven species of the scrub grassland. such species suitable for growing on the meadow grassland as Sophora davidii had expanded into the typical grassland and become its dominant species; among the species that grew on the typical grassland, such species as Caragana korshinskii had expanded into the desert grassland and become its dominant species; Periploca sepium that grew on the desert grassland had expanded into the ecotone between the typical and desert grasslands and appeared as the companion species or occasional species of the ectone. All The above described species distributions could be used as indicators or important markers for the climatic changes and that provided scientific basis for researching on climatic changes, species diversity and distributions of China.(6) The study found it out that in the loess plateau, the grasslands appeared obvious to change their distributions. Analysis according to the geographical distributions and floral elements and environmental conditions and in combination with the survey and research data and literatures about the vegetations in the loess plateau indicated that the tendency of modern climate tending to warm and dry as well as repeated human vegetation damages caused the border line of the forest grassland to recede south, the borderline of the typical grassland to continue expanding, moving south and directly invading into the forest grassland, the desert grassland to continue moving south into the typical grassland, so that currently the forest grassland, typical grassland and desert grassland presented obvious mosaic vegetation distributions in the loess plateau.更多还原