【作者】 牛克昌；

【导师】 杜国祯； Philippe Choler；

【作者基本信息】 兰州大学 ， 生态学， 2008， 博士

【摘要】 以植物功能特征重建群落生态学需要广泛而深入地比较研究群落组分种植物特征对环境变化的响应。理论上植物个体特征的响应可以逐层转化为群落对环境变化的响应——作为基础权衡的个体功能特征响应可以转化为个体竞争、存活和繁殖等表现特征之间的次级权衡,即个体水平的表现特征响应;个体的表现响应进而能够影响到种群动态和物种在特定生境中的多度格局,即群落水平的响应。因此,综合研究从植物特征到物种多度各生态水平对环境变化的响应以及各响应水平之间的联系被称为植物生态学研究的“圣杯”。然而,很少有以植物功能特征响应揭示了从个体到群落结构各层次对环境变化响应机理的实验研究。植物功能特征响应是个体低级水平的权衡,它易受多种因素影响;与此相比植物表现特征由于是个体适合度的主要成分,对个体的表现和物种的适合度体现更具决定性的作用。作为重要的表现特征之一,植物繁殖分配长久以来深受种群生态和进化生态研究的关注。在本论文研究中,我们选择植物重要的繁殖特征繁殖分配为指标探究植物群落组分种生活史对策和群落结构对环境变化的响应以及两个响应水平之间的联系。我们的主旨如下:(ⅰ)探讨群落组分种繁殖分配对施肥和放牧干扰响应的一般性模式;(ⅱ)分离大小变化和适应可塑性在繁殖分配响应中的相对重要性;(ⅲ)揭示植物生物量分配响应在植物群落结构变化中的作用;我们在选择容易测定植物繁殖分配而且群落组成简单的青藏高原东部典型高寒草甸群落为研究对象,连续三年测定了32种主要群落组分种的繁殖特征和群落结构对人工施肥和长期放牧的响应。我们选择组分种果期在高施肥、禁牧对照和放牧群落中的生物量数据分析植物繁殖分配对施肥和放牧响应的一般性模式;并以这些生物量响应与植物每年生长季末物种多度响应之间的相关关系分析生物量分配响应在群落结构变化中的作用。我们用异速模型拟合所有组分种花期和果期在低施肥、禁牧对照和放牧群落中取样个体的生物量和对应的繁殖部分生物量之间的关系用以分离繁殖分配与个体大小的关系。我们得出主要结果如下:ⅰ)群落组分种繁殖分配对施肥和放牧响应的一般性模式。施肥和放牧明显影响多数组分种个体生物量和生物量分配模式,即群落大多数组分种在施肥群落中的平均个体生物明显大于在不施肥群落中的平均个体生物量,而繁殖分配则比不施肥群落群落中的小;大多数组分种在放牧草地中的个体生物量明显小于禁牧地中的个体生物量,而放牧草地中繁殖分配则明显大于禁牧草地中的繁殖分配。物种个体生物量和生物量分配对放牧和施肥的响应程度因种而异,不同功能群间常常也有着明显的差异,例如:在个体生物量的响应上禾类草明显大于同群落中的杂类草。ⅱ)繁殖分配的个体大小依赖性和个体大小不依赖性。我们发现四分之一的物种个体生物量和繁殖生物量异速回归的斜率因放牧而发生了明显的改变;在施肥处理中,斜率发生明显改变的物种占五分之一左右。当斜率没有明显的改变时,大多数物种个体生物量和繁殖生物量异速回归的截距因放牧而明显减小或因施肥而明显增加。在物种水平上,禾类草和杂类草的个体生物量和繁殖生物量异速回归的截距因施肥和放牧都明显改变,异速斜率在禾类草中有所改变。ⅲ)生物量分配响应与物种多度变化之间的关系。群落施肥后,物种的个体生物量响应和叶分配响应都与物种相对多度的变化明显正相关;而物种的茎分配与物种相对多度变化负相关;物种的繁殖分配响应和物种相对多度变化并不相关。对禁牧6-7年的群落和长期放牧的群落比较可知,物种的个体大小响应和叶分配响应都与物种的相对多度变化正相关;物种的茎分配响应和繁殖分配响应都与物种的相对多度变化都负相关。无论是对人工施肥还是对长期放牧干扰,物种的茎分配响应和繁殖分配响应与叶分配响应都有着强烈的负相关关系。根据以上结果我们可得结论和展望如下:ⅰ)青藏高原高寒草甸群落组分种常以明显的增大个体大小和繁殖阀值同时减小繁殖分配来响应群落施肥;以减小个体大小和繁殖阀值而同时增大繁殖分配来响应持续的放牧干扰。我们认为物种生活史对策、植物生活型和物种功能的差异共同决定了群落组分种间在个体生物量和生物量分配响应上的差异。ⅱ)施肥和放牧导致的繁殖分配的响应主要是由于植物个体大小变化的结果。个体大小变化导致了大小依赖的繁殖分配响应和繁殖阀值变化;不依赖于个体大小变化的物种的适应可塑性在繁殖分配响应中也有着重要的作用。ⅲ)植物生物量分配响应能够解释群落结构的响应。通过群落组分种个体生物量和生物量分配对环境变化的响应与组分种相对多度响应之间的关系分析,施肥后个体大小和叶分配增加越多的物种多度减小越大;放牧后繁殖分配增加越大茎分配减小越多的物种多度减小越多;反之亦然。由于物种水平茎分配响应、叶分配响应和繁殖分配响应之间的权衡作用,施肥后叶分配或放牧后繁殖分配的增加往往以茎分配减小为代价。除此之外,我们认为物种繁殖和生长的权衡在植物群落构建中有着重要的作用;施肥和放牧导致群落物种多样性变化明显,而功能多样性可能并不伴随物种多样性的改变而变化。我们相信本论文的研究在一定程度上揭示了青藏高原高寒甸植被放牧退化的机理,也为该高寒草甸生态系统恢复重建提供了理论依据。更多还原

【Abstract】 Background and AimsBuilding communities ecology with functional traits need intensively and extensively comparative study response of plant trait of community’s compent species to land use and environment change.Scaling plant trait to community in response to variable environment following such theoretical framework:plant functional trait response as a fundamental trade-offs in individual level;this basic trade-offs can translate to secondary trade-offs-the trade-offs among individual ability of competition,survival and reproduction,as performance traits response;this species process response could translate to high trade-off-species abundance and distribution,as a response in community level.Therefor,the synthetic study of plant trait and species abundance in response to environment change,and linking individual trait response to community response,has been described as the "Holy Grail" of plant ecology.However,the linkage between functional trait response and species abundance distribution along environmental gradients often fail in field study.Compareing to low-level functional trait,plant performance trait as fitness components are more effectively in determine to plant performance and species fitness.As an important performance trait,plant reproductive allocation(RA)has long been a central topic in population ecology and species evolution.In this study,we choice plant RA as a proxy to compare component species in response environment change and linking individual response to vegetation process over common land use (fertilization and grazing)in Tibetan grassland.Our gist as following:(ⅰ)Seeking a general pattern of species RA in response to long-term grazing and short-term fertilization.(ⅱ)Disentangling size-dependent and size-independent plant RA in response to fertilization and grazing.(ⅲ)Studying the role of biomass allocation strategy in change of community structure due to fertilization and grazing. MethodsWe conducted 3 years experiments in perennial herbaceous communities in an alpine meadow on Tibetan Plateau.The location is The Alpine Meadow Ecosystem Field Station of Lanzhuo University,MaQu(101°53′E,35°58′N).We chose 32 component species and sampled 25-30 individual of each species at their flower and fruit phases in fertilizing(two level),natural control and grazing communities from 2004 to 2006,which was for measure biomass response in individual level. Correspondingly,10 quadrants were sampled in each treatment at middle of July and September in each year for investigates the response in communities’ level.Light and soil resource in treatment was measured at same time of vegetation monitoring.From data sets,we chose collected biomass data of 32 species in fruit phase from high level fertilized,control and grazing treatment for analyse to general response pattern of biomass allocation.Total biomass was represented by totaled three parts biomass,and RA was the proportion of biomass of fruit to total biomass;stem allocation was the proportion of stem biomass to total biomass;leaf allocation was the proportion of leave biomass to total biomass.We then used these to estimate the species biomass response to fertilization and grazing with the Log Response Ratio (LRR).Same method used in mearsure to species abundance response(at September). To test for the effect of the fertilization and grazing on species abundance and biomass(allocation),we used an independent-sample t-test.The mean LRR of each functional group was calculated for relative abundance,individual biomass and biomass allocation.We performed non-parametric Kruskal-Wallis tests to test the differences among groups,and Mann-Whitney U tests for post-hoc comparisons.For disentangling size-dependent and size-independent plant reproductive allocation in response to fertilization and grazing,we chose collected data of 32 species from low level fertilized,control and grazing treatment in 2005 and 2006.We performed allometric model for best fitting relationship between reproductive biomass (RB)and vegetative biomass(VB)for each population of each species.We estimated the allometric coefficients(slope and Y-intercept)for 301 RB-VB bivariates,using typeⅡregression analyses in order to test the diference of allometic coefficients between control and fertilized(or grazing)treatement.Using data sets of the general response of species abundance and biomass,we examined the relationships between the response in species relative abundance and the response in species biomass(and biomass allocation)by calculating Kendall’s tau-b correlation coefficients.Data for each growing season were analyzed separately.Key Resultsⅰ)Gerneral response pattern of RA to land useWe found fertilization and grazing significantly affected the biomass and the biomass allocation of most species.In whole,individual biomass increased and RA decrease following fertilization,and individual biomass decreased and RA increase due to grazing.The degree of RA response to fertilization and grazing were different among comonpent species and functional groups within same community,such as:the biomass response of graminoids was of stronger magnitude.ⅱ)Size-dependent and size-independent RA in response to land useOur results indicated significant changes in the RB-VB slope for 26 out of 102 cases in grazed plots,and 16 out of 88 cases in fertilized plots.Moreover,when slopes were not affected by treatment,more than 50%of the allometric models showed a significant change in the Y-intercept.Y-intercepts generally increased in fertilized treatment and decreased in grazed treatment.At the interspecific level,the Y-intercept,but not the slope,of the RB-VB relationships was significantly affected by land use.The allometry of RA for graminoids and forbs responded similarly to treatmentⅲ)Relationship between biomass allocation response and species abundance change.Following fertilization in community,a strong positive correlation exists between species relative abundance response and individual biomass response,and change in species relative abundance has a positive correlation with leaf allocation response,a negative correlation with stem allocation response,and no significant correlation with RA response. Following grazing,change in species relative abundance strong positive correlated with individual biomass response and week positive correlated with leaf allocation response;change in species relative abundance strong negative correlated with stem allocation response and RA response.Whatever plant response to fertilization or grazing,stem allocation response strong negative correlated with leaf allocation response.ConclusionsWe found that grazing/fertilization triggered a marked decrease/increases in the plant size and reproductive threshold and increase/decrease in RA for most of the component species.We considered that the difference of species life history strategy, plant form and function leads to species and functional groups different in degree of the response.We conclude that the RA response to grazing and fertilization in grasslands result from mostly change in reproductive threshold and size dependent RA,and lesser adaptive plasticity of size independent RA.The occurrence of shifts in RA was neither related to functional group nor to the magnitude of biomass changes following grazing and fertilization.The response of species biomass allocation strategy is very important in vegatation process following land use.We found species with larger response in individual biomass and leaf allocation will response more in species abundance following fertiliazation and grazing.Due to trade-offs among response of stem allocation,leaf allocation and reproductive allocation,we found increase in leaf allocation or reproductive allocation often at expense of stem allocation.We discuss the role of growth/reproduction trade-offs in structuring plant community and the response of functional diversity to land use in Tibetan grassland.更多还原