【作者】 高慧；

【导师】 高玉葆；

【作者基本信息】 南开大学 ， 生态学， 2013， 博士

【摘要】 植物对干扰的响应和群落构建机理是生态学研究的两个核心问题。近年来利用功能性状来揭示物种生存策略和群落组配机理被广泛接受。功能性状是指间接的通过影响物种的“生长一生殖一生存”三方面的个体表现,而影响物种适合度的任何一种“形态一生理一物候”性状。基于植物性状的方法为解释物种的生存策略和群落组配的不同生态学过程提供了有利手段。本研究采用以性状为基础的研究方法研究了不同草地利用方式下物种的适应策略和资源可利用性梯度上草地群落结构形成过程的可能机理。即：内蒙古草原放牧和割草条件下大针茅和克氏针茅的表型可塑性和繁殖策略,美国北加州山谷草地模拟放牧梯度上食草动物选择性取食和物种响应的关系以及坡地资源可利用性梯度上植物群落的构建机理。本文主要得出以下结论：1.在放牧干扰下,群落优势种克氏针茅具有较大的叶表型可塑性,而另一个优势种大针茅则表现出较大的整株表型可塑性。放牧条件下克氏针茅比大针茅具有更高的比叶面积和叶片/叶鞘比值,因此可能具有更强的再生速率和光合能力；放牧条件下大针茅的基面积和根冠比的变异增大,放牧可能导致了大针茅株丛破碎化和分蘖数的增加,克氏针茅具有更强的耐牧适应性。大针茅和克氏针茅在放牧条件下的可塑性均大于割草条件下的可塑性。2.放牧对大针茅和克氏针茅的繁殖过程有明显不同的影响。放牧能显著增加克氏针茅的营养枝数/生殖枝数比例,能显著降低大针茅的营养枝重/生殖枝重比例,说明放牧能显著地增加克氏针茅对营养繁殖的投入,能显著地提高大针茅对有性繁殖的投入；两个物种在繁殖策略上的逆向调节,可能是它们在放牧干扰下能够互相取代的重要机制。3.物种的高度、相对生长速率决定着物种的放牧响应,不同的物种采取不同的策略适应放牧干扰。并不是所有的增加者都是耐受性物种。许多物种的性状表明它们有着明显较高的营养品质(即较高的SLA,较低的LDMC),但实际上是采用避牧性策略应对食草动物的取食(较矮的高度、带刺以及叶片中较高的硅含量)。4.功能多样性格局表明低生产力群落可能主要是由环境筛滤作用和地下部竞争作用产生的,而高生产力群落更多的是由地上部竞争和物种的优势度决定的。5.在美国北加州山谷草地,近几十年的放牧干扰活动对植物群落的演替过程产生了重要影响,特别是对植株高度和种子大小有较强的选择性。更多还原

【Abstract】 Plant responses to disturbance and community assembly mechanisms have been central to the study of ecology for decades. The trait-based approaches is growing in recent ecology studies. Functional traits are defined as ’morpho-physio-phenological’ traits that impact fitness indirectly via their effects on growth, reproduction and survival of individual plant performance. Trait-based approaches have been advocated as a useful tool to explain species adaptive strategies and explore the different processes suggested to affect community assembly. This dissertation uses trait-based approaches to explore plant species adaptive strategies under different landuse types of arid-and semi-arid grassland, additionally, we examine the community assembly mechanisms along a resource availability gradient mainly mediated by elevation. Specifically, chapter2and chapter3examine the plasticity and reproductive strategy of two constructive species Stipa grandis and S. krylovii in response to grazing and mowing in Inner Mongolia steppe; Chapter4examines the relationship between herbivore diet selectivity and species response to a manipulated grazing gradient in California Valley grassland; Chapter5examines the pattern of functional traits diversity along a resource availability gradient and relates these results to the different processes suggested to affect species coexistence within plant communities. We get several useful results:1. The dominant species S. krylovii had higher leaf plasticity while the other dominant species S. grandis had higher whole plant traits plasticity in grazing treatment. Specifically, S. krylovii had higher SLA and leaf blade/sheath ratio than that of S. grandis under grazing, it indicated that S. krylovii had stronger regeneration rate and photosynthetic capacity than that of S. grandis in grazing.’The variability of basal area and root/shoot ratio of S. grandis were increased under grazing treatment, it suggested that grazing induced tussock fragmentation and the tiller increment of S. grandis. Thus, S. krylovii was more tolerant to grazing than S. grandis. The plasticity of both species under grazing was larger than under mowing condition. 2. Grazing had different effects on reproductive processes of S. grandis and S. krylovii. Grazing significantly increased vegetative tiller to flowering tiller biomass ratio of S. krylovii, while significantly decreased vegetative tiller to flowering tiller biomass ratio of S. grandis. It suggested that S. krylovii investigated more resources into vegetative reproduction, while S. grandis investigated more resources into sexual reproduction in grazing. The reverse reproductive strategies of both species in grazing would be one of important mechanisms of species replacement.3. Plant height and RGR were good predictor traits of species in response to grazing; different species took different adaptive strategies in response to grazing, not all increasers were tolerant species, although some of them had high foliage quality (high SLA, low LDMC), they used avoidance strategies through short stature, thorn and high silica content to increase their abundance in grazing.4. The results of functional trait patterns showed that less productive communities were structured by environmental filters, belowground competition, while more productive communities were structured by aboveground competition and species abundance.5. In northern California Valley grassland, the long history grazing management had been playing an important role in evolutionary process of plant communities; especially it had stronger selective pressure on plant height and seed size.更多还原