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题名 青藏高原高寒草甸植物群落退化过程和恢复机理的研究
姓名 韩文武
院系 草业农业科技学院
专业 草业科学
学位名称 农学硕士
外文题名 Study on degradation progress and restoration mechanism of plant community in Qinghai Tibetan plateau
第一导师姓名 杜国祯
关键词 施肥;模拟放牧;刈割;功能群;物种多样性;地上生物量;个体密度;补偿;退化与恢复;青藏高原
外文关键词 fertilization;simulated grazing;clipping;functional group;species diversity;aboveground biomass;individual density;compensation;degradation and restoration; Qinghai Tibetan plateau
学科 农学
摘要 由于物质生产和经济利益的需求,畜牧业经营者最大化地养殖家畜,致使大面积的草地超载过牧,从而导致草地生态系统出现了不同程度地退化或更严重的荒漠化,如青藏高原的典型高寒草甸生态系统,一些地方出现了大面积草地的退化和沙化现象。因此,对于草地的退化过程与恢复机理问题的研究,是当今全世界生态学界最为关注的热点问题之一。地上部分植被多样性、生产力等特征,植物群落结构组成和地下营养循环是其研究的关键所在。鉴于此,通过施肥和模拟放牧对青藏高原东缘高寒草甸生态系统的作用进行了研究,试图探明其退化过程与恢复的机理。许多研究业已表明,恢复的成功与否是建立在群落的特征、物种多样性或生态系统的作用过程,近十年以来,尤其生物多样性损失因果关系以及功能群多样性的效应,引起了生态学家的巨大的关注与广泛的争议。 我们的实验研究结果显示,在没有施肥的情况下,物种多样性较高,施肥导致物种多样性显著下降,而且其下降的程度随施肥梯度的增加而增加。施肥后生产力显著增加,但随时间持续性地施肥,生产力在各个施肥梯度都在逐渐下降,这说明持续性地施肥并不能够维持高寒草甸群落高的生产力。这是以往研究前所未有的。尽管施肥也使总的个体密度降低,但禾草植物的密度和生物量却显著上升,这是因为添加限制性资源后,尤其是在高肥力下,禾草植物依其本身特征的优势发生了补偿效应。而且,在高肥力下,当施肥导致仅有少数功能群存活时,中等水平的刈割增加了功能群多样性。以生物量指标为衡量的依据,高肥力区的模拟放牧使禾草植物发生了补偿效应;中等肥力区轻度模拟放牧时发生了超补偿现象。结果还发现,当植物地上部分烘干的生物量超过50g/0.25m2,禾草类植物占优势;在25-50g/0.25m2范围内,主要为莎草科植物;而杂草,有毒草以及豆科植物主要分布在0-25g/0.25m2之间。这种分布格局有利于预测植物群落结构和组成的变化。在生长季末,对控制区和各施肥梯度上基本的土壤资源进行分析,发现速效氮在施肥梯度上没有发生显著变化,而速效磷随施肥梯度的增加而显著的增加。由此可以推断,高寒草甸生态系统土壤资源可能受氮元素的限制,而不是磷;有机质没有发生显著变化,而土壤酸度随施肥梯度的增加有减小的趋势。施肥后植物群落的结构也发生了显著的变化,而短时间的模拟放牧除降低了植物的覆盖度之外,没有发生大的变化。在高施肥区,五年后物种丰富度从当初平均30个/0.25m2,下降至平均8个/0.25m2。显然从保护生物多样性的角度出发,大量的持续性的施肥并不能解决草地管理所存在地问题,况且随时间持续性的施肥,生产力还在显著地下降。也不能因那些有毒杂草适口性较差而消除,因为他们为维持高寒草甸的生态系统起着不可替代的平衡作用。各功能群植物对模拟放牧的反应不同,不仅取决于功能群植物的生长能力等特点,还与土壤中的有效资源和干扰的强度有关。理解这些机理有助于较好地管理面临退化的草地或草甸。 干扰假说一般认为,由于中等水平的干扰而抑制优势物种使得物种丰富度达到最大值,即具有单峰模式的关系,基于此假说,我们预测将刈割作为干扰来分...
外文摘要 Rapid land degradation and desertification have taken place in grassland and meadow of many sites in the world, by overgrazing due to very high stocking rates to sustain development of production and economy of human. And as well known stock farmers are keen to maintain high stock rates to reach topmost production; as a result, there is degradation and desertification in some places of Alpine meadow ecosystem in China. Hence it is key problem that understand the degradation progress and restoration mechanism of an ecosystem. Therefore, the study of degradation and restoration on grassland or meadow is one of the hot issues in ecology. The aim of this study was to detect degradation progress and restoration mechanism in Alpine meadow ecosystem of east Qinghai Tibetan plateau through simulated grazing at different soils fertility. Most studies have suggested that restoration success could be based on vegetation characteristics, species diversity or ecosystem processes, especially, the ecological consequence of biodiversity loss and effect of functional groups have aroused considerable interest and controversy during recently years. Ecosystem processes (productivity and nutrient recycling) result directly from the diversity of functional traits in the biotic communities, which is in turn determined by the species composition and diversity. As a result, species diversity was higher at the control plots and decreased significantly after five years of nutrient addition, and the trend of declining increased with fertilization levels increasing. Although the total species density was significantly decreased after nutrient addition, the graminoids density and aboveground biomass were significantly increased with nutrient increasing due to limited nitrogen for graminoids was compensated after limited resources addition, especially in the highest nutrient addition plots. Productivity increased significantly with fertilization adding to the community, but the trend of increasing significantly drop with time continuing, that is continued fertilization can not maintain high productivity.However, intermediate clipping increased functional diversity at higher fertility in soils where only few functional groups survive. The compensation that was observed resulted from plants biomass subsequent to simulated grazing in the highest fertility plots. Over-compensation was detected only when lightly simulated grazing at intermediated fertility. The compensation and over-c...
研究领域 草地生态
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