【作者】 郭连金；

【导师】 张文辉；

【作者基本信息】 西北农林科技大学 ， 植物学， 2005， 硕士

【摘要】 黄土丘陵区是世界上水土流失最严重的地区之一,生态环境十分脆弱。由于该区人口增长过快,盲目开垦耕地以及过度放牧和土地资源的不合理利用,造成生态环境进一步恶化。天然森林已全部遭受破坏,植被类型主要为零星分布的旱生小灌木狼牙刺、虎榛子等及以生态修复为目的的人工林沙棘、小叶杨、刺槐等。但近年来发现,部分人工林由于不适应当地环境而逐步衰退,不能起到保持水土,改善环境的作用。本研究以该区主要的人工灌木林沙棘和乔木林小叶杨为例,系统研究了其种群结构、群落物种多样性、水分养分效益、环境因子影响,并进行了稳定性评价、确定其适生环境,为黄土高原丘陵沟壑区植被恢复和重建提供理论依据。研究结论如下: 沙棘是一个良好的人工林天然化灌木物种,在黄土丘陵区该种群更新良好。在一个发育系列里,随着时间的推移,种群结构逐步呈进展型、物种多样性持续增加、土壤水分、养分明显好转,群落越来越稳定。在非阳坡地段,幼龄、中龄个体多,属于进展型的种群,能够长期稳定存在下去;半阳坡和半阴坡地段的沙棘人工林具有较高的物种多样性,强的种间的关联度以及较优越的土壤水分、养分条件,这些对群落稳定发展提供了保障。因此,在黄土高原植被恢复建设工程中,应该利用沙棘特有生物学、生态学特性,在半阳坡、半阴坡条件下营造人工林,以发挥其加强水土保持、改善土壤理化结构的生态功能。　小叶杨种群在黄土丘陵区更新困难。在一个发育系列里,随着时间的推移,小叶杨在发育20 年时产生更新幼苗,30 年时幼苗相对较多,物种多样性较高,群落组成、结构较为合理,但乔木层仍然过于单一,并发育至45 年时表现出衰退现象,土壤养分虽有一定的改善,但仍不能为群落稳定发展提供水分和养分的保障。不同生境研究表明:小叶杨无法在阳坡更新,相比较而言,在水分条件较好的阴坡、沟坡等地段小叶杨长势较好,并产生少量幼苗,具有较高的物种多样性,土壤水肥条件达到最好,但仍不能改变整个种群的衰退趋势,随着时间的推移小叶杨种群将会消失,其所在群落也不稳定。因此小叶杨造林应选栽在阴坡、沟谷等水分条件较好的生境下栽植,并要实施适当的抚育措施,阻止其衰退,促进其更新。　如何提高人工植被的稳定性和生产力是目前生态环境重建亟待解决的问题。本研究表明提高人工植被的稳定性应从以下几个方面考虑:根据植被地带性分布规律,以建立与当地环境条件特别是水热条件相适应的植被类型(乔木、灌木或草本)为目标植被;重视乡土物种的选择和运用;选择抗逆性强和适应性好的物种;对于更新差的人工林,应进行适当的人工抚育措施;重视植被的合理配置方式,模拟天然植被的斑块格局促进群落自然更新,形成稳定群落。更多还原

【Abstract】 Hilly-gully region of Loess plateau is one of the places where there the problem of erosion of water and soil is very serious, and the ecology environment is very brittle in the world. Because of the human population of this area increasing sharply, the field reclaimed blindly, immoderate graze, and the irrationality utilization of land resource, the environment was made even worse. Natural forests were all destroyed. The main vegetation types are only Sophora davidii, Ostryopsis davidiana undershrub etc. and Hippophae rhamnoide, Populus simonii and Robinia pseudoacacia etc. built to restore the environment. Some phenomena were found these years that parts of plantations were not stable, and yet were deteriorated gradually for maladjustment to the location environment. Those plantations could not preserve the soil and water, and not improve the environment. So this research studied on the population structure, species diversity, moisture and nutrient in soil, and the infection of environment elements of the main plantations, Hippophae rhamnoide and Populus simonii. Systemically, and confirm the suitable environment of the main plantations, in order to offer theory bases to vegetation renewal and rebuilding. The result is showed as follows. Hippophae rhamnoide is a nicer shrub species for plantation becoming savageness. This population could renew very well in Hilly-gully region of Loess plateau. With the time going, the population structure took on a developing trend, biodiversity, moisture and nutrient in soil increased gradually, and community was more stable in a development sequence. The number of youth and adults was large on half-sunny, half cloudy slope and cloudy slope, which showed that this population was a developing one, and could survival in the future. There were higher biodiversity, strong intensity of Interspecific association, and better moisture and nutrition in soil in this plantation on the half-sunny and half cloudy slope which provided a guarantee for community stabilizing gradually. So, some measures should be adopted to build Hippophae rhamnoide plantations on half-sunny and half-cloudy slope by using its characters of biology and ecology, in order to exert its ecologic function to strengthen the water and soil retained, improve the soil physical and chemical structure. The Populus simonii population renew difficultly in Hilly-gully region of Loess plateau. In one development sequence, the renewal seedling appeared when the population developed at 20 years, and more renewal seedlings, higher species diversity, more reasonable community composing and structure at 30 years. However arbor layer was still only one species, and this plantation appeared to decline at 45 yeas. Although the soil nutrient had certain improvement, the community could not get the guarantee of enough nutrition for stably. The result of research on different habitats showed that this population could not renew at sunny slope. Compare with in the sunny slope, there were growing well Populus simonii, several seedlings appeared higher biodiversity and better soil nutrient content in the cloudy slope. But these could not change the declining trend of the whole population, the Populus simonii population disappeared gradually. So the Populus simonii should be planted at places where there has more soil water, such as cloudy slope, gully and so on, and some suitable upbringing measures should be adopted at a time, in order to prevent this community from declining and promote the population to renew. The fact that how to improve plantations’stability and productivity was a problem solved urgently in the eco-environment rebuilt field now. This research showed that some aspects should be taken into account to improve the plantation stability. First, to build certain vegetation types, arbor, shrub and herb, which should be adapt to the local environment, especially the water and hot, according to the distributing rule of the zone vegetation. Second, t o have important attach to selecting and using local species. Third, to select species which have strong resistance and adaptability. Forth, to adopt suitable upbringing measures for promoting plantations renew. Fifth, to pay more attention to reasonable configure fashion, and simulate the block pattern of natural vegetation to improve plantations evolving naturally, and form a stabile one.更多还原