Different responses of biomass allocation and leaf traits of Dodonaea viscosa to concentrations of nitrogen and phosphorus

调整叶性状和生物量分配格局是植物适应环境变化的主要途径, 研究车桑子(Dodonaea viscosa)幼苗生物量分配与叶性状对氮磷浓度的响应对认识车桑子在氮磷浓度变化下的适应策略具有重要意义。该研究通过砂培法, 测定不同氮浓度(3、5、15、30 mmol·L^-1)与不同磷浓度(0.25、0.5、1、2 mmol·L^-1)下车桑子幼苗的生长、生物量分配、叶性状的响应特征及其相互关系。结果表明: 高浓度氮(30 mmol·L^-1)促进了车桑子幼苗生长、叶片氮含量和生物量积累, 其余氮添加条件(3、5、15 mmol·L^-1)下车桑子幼苗各性状无显著差异, 但相比高氮水平, 其生物量积累和叶片氮含量显著降低, 根冠比和氮利用效率显著增加。随着磷添加浓度的增加, 车桑子幼苗生物量显著增加, 低磷条件(0.25、0.5 mmol·L^-1)限制了车桑子幼苗生长和生物量积累, 其根冠比和磷利用效率均没有发生显著变化, 但比叶面积和叶/茎生物量比例显著增加, 叶干物质含量显著降低。氮处理下, 叶片氮含量与根冠比显著负相关; 磷处理下, 叶片氮含量与比叶面积显著正相关。同时, 氮处理下, 车桑子幼苗株高、基径、总生物量等生长性状均与根冠比显著负相关, 与叶片氮含量显著正相关, 表明根冠比和叶片氮含量的调整在车桑子适应氮限制中发挥重要作用; 而磷处理下, 株高、基径、总生物量与比叶面积显著负相关, 与叶干物质含量显著正相关, 表明叶片结构性状的调整在车桑子适应低磷环境中具有重要意义。该研究表明, 车桑子幼苗生物量分配和叶性状及性状间的权衡策略对氮、磷的响应具有明显差异性, 在今后的研究中, 应关注氮和磷对植物性状影响的差异性。     

喜旱莲子草对遮荫的可塑性反应:入侵地与原产地种群的比较

表型可塑性可能在外来植物的成功入侵和随后的扩散中起到至关重要的作用。一些研究者推测喜旱莲子草(Alternanthera philoxeroides)入侵地种群可能比原产地种群对光强具有更强的可塑性反应。为了验证该假说,我们在正常光照和遮荫(30%正常光照)条件下研究了喜旱莲子草原产地(阿根廷)和入侵地(美国)种群在形态特征和生物量分配上是否存在显著差异。结果表明:(1)喜旱莲子草对光照强度具有很强的可塑性。在遮荫处理下,其根冠比和分枝生物量比显著降低,而比茎长和比叶面积显著增加;(2)原产地和入侵地喜旱莲子草的总生物量和比叶面积对遮荫的可塑性没有显著差异。入侵地种群的根冠比、分枝强度和比茎长的可塑性显著小于原产地种群;(3)无论在正常或低光照条件下,入侵地种群的根冠比(–20.8%)、分枝强度(–54.6%)、比茎长(–18.5%)和比叶面积(–8.6%)均显著低于原产地种群。这些结果表明,喜旱莲子草对光照强度具有很强的可塑性,这可能是该物种可以分布于从河岸带草丛到疏林灌丛等各种生境的主要原因;从原产地到入侵地,喜旱莲子草与耐阴性有关的性状对光照的可塑性显著降低,可能是该物种在入侵地能够形成单优势种群的主要原因。     

常绿和落叶阔叶物种当年生小枝茎长度和茎纤细率对展叶效率的影响

枝和叶是组成树冠的两个最主要的结构单元,枝条的结构特征及其与叶性状之间的变化关系决定了植物对光照、空间等资源的利用和适应策略。该研究以小枝茎长度和茎纤细率表征茎结构,以叶面积比(即单位小枝茎干质量的总叶面积)、叶密度(即单位茎长度的叶数量)和叶茎生物量比(即单位小枝茎干质量的总叶干质量)表征展叶效率,以浙江省清凉峰自然保护区25个常绿阔叶物种和60个落叶阔叶物种为对象,探讨小枝茎结构变化对展叶效率的影响。结果显示,展叶效率无论是用叶面积比、叶密度还是用叶茎生物量比表示,常绿和落叶物种小枝的茎长结构性状均与展叶效率呈显著的负相关关系,即随着小枝茎长度和茎纤细率的增加,展叶效率逐渐降低,可能反映了机械安全和光照限制的作用。同时,尽管茎长度-展叶效率的斜率在常绿和落叶物种间无显著差异,并且常绿物种叶密度与小枝茎结构性状之间的关系截距显著大于落叶物种,即常绿物种具有较高的出叶强度。但由于单叶面积和比叶面积显著小于落叶物种,在某一给定的小枝茎长结构下,常绿物种每单位质量的茎生物量投资获得的总叶面积和总叶质量都比落叶物种少,即常绿物种的展叶效率比落叶物种低。这可能反映了常绿物种高消耗慢收益的保守型策略。这些结果表明,小枝茎长结构对展叶效率具有显著的影响,并将随叶习性的不同而改变,与植物对环境的适应策略密切相关。     

不同生境植物幼苗对光照时间异质性的响应

光照时空异质性对植物影响的重要性早已被认识,但大多数研究集中于植物如何响应光照空间异质性,关于植物如何响应光照时间异质性过程的实验证据较少。本文以喀斯特生境物种单性木兰、非喀斯特生境物种石栎和两种生境的共有种朴树的一年生幼苗为对象,通过比较它们在光照时间异质性(全光照-重度遮阴交替)和时间同质性(一直中度遮阴、一直全光照)处理中形态、生物量和生理特征的响应,探讨这3个物种对光环境变化的响应能力和策略。与中度遮阴处理相比,光照时间异质性处理提高了植物的基径,降低了总生物量。相比全光照和中度遮阴处理,光照时间异质性处理提高了植物的渗透物质含量、丙二醛含量和抗氧化酶活性。早期光照时间异质性处理引起植物细胞渗透压和膜脂过氧化程度升高,抑制了植物当前生长,但在处理末期,却提高了植物对后期压力事件下的总生物量日累积速率,植物的各渗透调节物质含量和抗氧化酶活性也有显著的下降趋势。在整个光照时间异质性处理过程中,喀斯特生境物种单性木兰的丙二醛含量水平最稳定,而且总生物量日累积速率在处理末期最高。总而言之,3个物种对同种光照条件产生的趋同适应与处理早期的光照经历息息相关。单性木兰在长期适应喀斯特生境过程...     

麻栎和闽楠幼苗叶功能性状及生物量对光照和施肥的响应

光照和养分条件是影响植物生长的重要环境因子,不同生活型植物对环境异质性的响应机制不同。以落叶阔叶树种麻栎和常绿阔叶树种闽楠幼苗为研究对象,设置2个光照梯度（全光照和45%全光照）和4个施肥梯度（不施肥、氮磷供应比为5、15和45）共8种处理,研究光照和施肥及其交互作用对麻栎和闽楠生物量和叶形态、生理及化学性状的影响,并探讨了叶功能性状和生物量的关系。结果表明：（1）光照、施肥及其交互作用对光合气体交换参数（除水分利用效率外）、叶绿素荧光参数、叶形态指标（除比叶面积外）、单位质量叶氮含量和根冠比影响显著（P<0.05）。此外,光照和施肥对地上生物量和总生物量影响显著（P<0.05）。（2）全光照显著增加了麻栎和闽楠单株总叶面积和地上、地下生物量及总生物量（P<0.05）,而遮荫降低了非光化学猝灭系数、光合氮利用率和根冠比,增加了单位质量叶氮含量。（3）在全光照处理中,施肥显著增加了麻栎和闽楠水分利用效率（P<0.05）;在遮荫处理中,氮磷供应比45显著增加了麻栎和闽楠净光合速率和水分利用效率（P<0.05）。（4）麻栎和闽楠在全光照中倾向于资源获取策略,在遮荫中偏向于资源保守策略。在光照和施肥处理中,麻栎和闽楠单株总叶面积与地上生物量均显著正相关（P<0.05）。总之,单株总叶面积是预测麻栎和闽楠幼苗地上生物量变化的稳定指标,施肥有助于增加低光环境下麻栎和闽楠幼苗的生态适应能力。     

喜旱莲子草在青藏高原对模拟增温的可塑性: 引入地和原产地种群的比较

气候变暖背景下植物可通过关键性状的表型可塑性来适应环境温度的增加。表型可塑性增强进化假说预测定植到新环境中的入侵植物种群具有演化出更强表型可塑性的潜力。此前对可塑性进化的研究涵盖了外来植物性状对水分条件、光照变化、土壤养分、邻体根系以及天敌防御等的响应, 而较少有研究关注增温条件下植物重要性状的可塑性进化。已有的部分研究多集中在温带和热带地区, 而较少关注入侵植物在高寒地区对增温的响应; 且研究多集中在植物生长相关性状, 较少关注功能性状和防御性状。本研究采用同质园实验比较了喜旱莲子草6个引入地(中国)种群和6个原产地(阿根廷)种群, 在西藏拉萨模拟全天增温2℃处理下的适合度性状、功能性状和防御性状的响应差异。结果表明: (1)高寒地区模拟全天增温显著提高了喜旱莲子草总生物量(+36.4%)、地上生物量(+34.5%)、贮藏根生物量(+51.4%)和毛根生物量(+33.6%), 降低了分枝强度(-19.8%)和比茎长(-30.2%); (2)模拟全天增温使引入地种群的比叶面积和黄酮含量增加, 而原产地种群则相反。这些结果表明高寒地区全天增温2℃对喜旱莲子草可能是一种有利条件。引入地种群的适合度性状对模拟全天增温2℃的响应比原产地种群更强, 而其光能利用相关性状和防御性状的响应可能提升了其在高寒地区的适合度。因此, 在未来全球气候变暖的背景下, 高寒地区温度升高可能更有利于喜旱莲子草引入地种群的定植和扩散。     

不同养分水平对飞机草生长与生物量分配的影响

采用温室盆栽模拟实验研究了不同养分水平对外来入侵植物飞机草(Chromolaena odorata)的生长性状、生物量积累以及生物量分配格局的影响。实验共设置5 种养分浓度处理, 分别为Hoagland 标准营养液的10%、25%、50%、100%和200%溶液。结果表明: 养分水平对飞机草植株的生长性状以及生物量的积累、分配产生显著影响。随着养分水平的增加, 飞机草的总分枝数量、长度以及一级分枝数量、长度持续增加, 并且100%、200%处理还能促进二级分枝的萌发生长。飞机草的叶片数、总叶面积、总生物量以及茎、叶两器官生物量随养分水平的上升显著增加, 但株高、根生物量不受养分浓度变化的影响。根生物量比、根冠比随养分水平的提高显著下降, 叶生物量比则显著上升, 但茎生物量比在各养分浓度保持稳定。叶面积比、叶根比、RGR 亦随养分含量的上升显著增加。说明养分资源丰富的环境将促进飞机草的地上部生长, 而生物量分配格局的变化可能是其在入侵蔓延过程中适应养分异质性生境的重要生态策略。     

青藏高原东缘大耳叶风毛菊繁殖特征对海拔的响应

研究了青藏高原东缘不同海拔12个居群大耳叶风毛菊(Saussurea macrota Franch.)繁殖分配对海拔的响应。结果表明:(1)随着海拔的升高,大耳叶风毛菊个体大小呈现减小的趋势,但其繁殖分配随海拔升高而增大,这是为了保证顺利完成有性繁殖而采取的生存策略;(2)大耳叶风毛菊部分花部特征发生变异,以响应随海拔升高面临的传粉困难问题,保证花期传粉的最大成功几率;(3)随着海拔的升高,大耳叶风毛菊产生的种子数目减少,种子百粒重增加;花序和管状小花的数量均减少,而它们的重量均增加,即权衡现象在大耳叶风毛菊的这些器官中普遍存在。     

营养和光照对不同生态幅风毛菊属植物幼苗形态可塑性的影响

以青藏高原东部4种不同生态幅的风毛菊属植物为试验对象,研究了不同营养和光照条件对风毛菊幼苗相对生长率、根冠比和比叶面积的可塑性影响.结果表明: 营养和光照条件对4个物种幼苗的3个形态特征变化呈现显著影响并存在一定的交互作用.这些形态特征的可塑性及其对营养和光照变化的响应模式存在一定的种间差异.物种与营养、光照的交互作用对风毛菊属幼苗的根冠比和比叶面积(P<0.001)存在一定的显著影响.4种植物幼苗的平均形态表型可塑性指数的大小与其生态分布相关,风毛菊幼苗的平均表型可塑性指数最大(0.71),是分布生境最多的一个物种.风毛菊属植物形态可塑性与其分布生态幅呈一定正相关关系.     

不同光照处理下青藏高原克隆植物黄帚橐吾(Ligulariavirgaurea)种子大小对其幼苗生长的影响

以高寒草甸克隆植物黄帚橐吾为实验材料,通过遮荫网模拟植被遮荫,研究种子大小与萌发及幼苗生长能力的关系和幼苗对光照条件的反应。结果表明:(1)在自然光照下,黄帚橐吾种子大小对种子萌发的影响显著,大种子的萌发率高于小种子。遮荫生境下,大、小种子萌发率有所降低,但遮荫对小种子萌发的影响比大种子显著。小种子的萌发率下降了近1/8,而大种子的萌发率仅下降了1/11。(2)黄帚橐吾种子大小对幼苗生物量积累影响显著,大种子幼苗总生物量(TB)大于小种子幼苗的。但生物量的分配与播种时间相关,播种后60d,在自然光照条件下,大种子幼苗对根生物量的分配大于小种子幼苗,而对叶生物量的分配则正好相反。在遮荫环境中,大、小种子幼苗普遍对根的生物量分配增加,大种子幼苗根冠比(R/S)大于小种子幼苗。(3)黄帚橐吾种子大小对幼苗的生长也有明显影响。在自然光照下,小种子幼苗的相对生长速率(RGR)较大于大种子幼苗,但叶面积比率(LAR)、叶面积干质量比(SLA)、叶干质量(LWR)差别不明显。在遮荫条件下,幼苗的LAR、SLA、LWR显著增加,但大、小种子幼苗间差异不显著,幼苗的RGR减小,小种子幼苗的减小趋势大于大种子幼苗。     

Competitive ability of two Brassica varieties in relation to biomass allocation and morphological plasticity under varying nutrient availability

Green cabbage (Brassica campestris, leafy variety) and turnip (Brassica campestris var. rapifera, rooty variety) were grown in both monocultures and mixtures at three nutrient levels to investigate their responses to nutrient availability with respect to biomass allocation, morphological plasticity and competitive ability. Their allocation parameters and leaf morphological traits were affected by both nutrient availability and developmental stage. Both of the varieties had a smaller biomass allocation to leaf blades, but a greater allocation to petioles at high nutrient levels. Root:shoot ratio (RSR) of green cabbage decreased with increasing nutrient availability, whereas that of turnip increased. Turnip had a smaller leaf blade weight ratio (LBWR) than cabbage, being compensated for by larger leaf area ratio (LAR) and specific leaf area (SLA). Leaf area ratio and SLA of both the varieties increased with increasing nutrient availability as did their mean dry weights. The mean dry weight of turnip was slightly greater than that of green cabbage in their respective monocultures, while that of green cabbage was greater than that of turnip in their 1:1 mixture. Therefore, green cabbage, having inherently greater biomass allocation to leaves, was generally more competitive than turnip with more biomass allocation to roots, especially at higher nutrient levels. However, within a variety, morphological plasticity (variation in LAR and SLA) was more important than the plasticity in biomass allocation (e.g. variation in RSR and LBWR) in determining competitive ability. The implication of our results is that competition models based on biomass allocation pattern alone may fail to predict competitive outcomes and that such models should also take morphological plasticity into full account.     

Effects of light and nutrient availability on dry matter and N allocation in six successional grassland species

Summary Recent discussions on determinants of competitive success during succession require the study of the combined effect of light and nutrient availability on growth and allocation. These effects can be used to predict the outcome of competition at changing resource availabilities. This work is part of a study on the successional sequence in permanent grassland starting after fertilizer application is stopped, but with continued mowing, in order to restore former species-rich communities. This yields a successional sequence which proceeds from grasslands with a high nutrient availability and a closed canopy, to grasslands with a low nutrient availability and an open canopy. If allocation is related to competitive ability, species from the productive stages would be expected to allocate more biomass and nitrogen to leaves, which could make them better competitors for light, while species from the unproductive stages would allocate more biomass to roots, which could make them better nutrient competitors. This study reports on growth, specific leaf area (SLA), vertical display of leaves, and allocation of biomass and nitrogen of six grassland species from this successional sequence at 16 combinations of light and nutrient supply. Species from the poorer successional stages reached a lower final dry weight than species from the richer stages, over all treatment combinations. The experimental design made it possible to test for unique effects of the resource ratio effect of light and nutrients on allocation characteristics. This resource-ratio effect was defined as the ratio light intensity/(light intensity + nutrient supply rate), using standardized levels for the treatments. The within-species variation (plasticity) in both allocation of dry matter and nitrogen was linearly related to this resource-ratio effect. Some interspecific differences in this relationship were found which could be related to the position of the species along the successional gradient. However, the range of plasticity in allocation pattern expressed within each species was much larger than the differences between species. It was concluded that allocation differences between these grassland species are relatively unimportant, given the large amount of plasticity in these traits. Interspecific differences in SLA and vertical stature seemed to be more important in explaining the position of species along the successional gradient.     

Trait means predict performance under water limitation better than plasticity for seedlings of Poaceae species on the eastern Tibetan Plateau

Water availability may be altered by changes in precipitation under global climate change in alpine areas. Trait means and plasticity are important for plants in response to a changing environment. In an examination of alpine plant responses to changed water availability, and for determination of how trait means and plasticity predict the performance (e.g., biomass) of these species, seeds of ten Poaceae species from the eastern Tibetan Plateau were sown and grown in a manipulated environment during a growing season in which rainfall was removed and other climate conditions remained unchanged. Growth and leaf traits of these species were measured. We found significant effects of moderate water stress on the seedling biomass of these species; however, the responses of these species to changed water condition were strongly dependent on species identity. For example, the biomass of some species significantly decreased under moderate drought, whereas that of others were either significantly increased or unaffected. This pattern was also observed for growth and leaf traits. Overall, the alpine Poaceae species showed low plasticity of traits in response to water availability relative to reports from other areas . Notably, the results show that trait means were better correlated with the productivity than with the plasticity of traits; thus, we argue that the trait means were better predictors of performance than plasticity for alpine Poaceae species. Poaceae species in alpine areas are important for forage production and for water catchment health worldwide, and these species may face water shortage because of current and future climate change. Understanding the response of alpine Poaceae species to water availability would facilitate our ability to predict the impacts of climate change on the alpine vegetation.     

放牧对内蒙古锡林河流域草地群落植物茎叶生物量资源分配的影响

以内蒙古锡林河流域沿水分梯度分布的灰脉苔草(Carex appendiculata)、贝加尔针茅(Stipa baicalensis)、羊草(Leymus chinensis)、大针茅(Stipa grandis)、小叶锦鸡儿(Caragana microphylla)和冷蒿(Artemisia frigida) 6个草地群落为对象, 研究了围封禁牧与放牧样地中144个共有植物种的高度、丛幅面积、茎、叶和株(丛)生物量、茎叶比等性状。结果表明: 1)在个体水平上, 放牧样地中植物的生殖枝高度、营养枝高度、丛幅面积、单株(丛)生物量、茎、叶生物量和茎叶比均显著低于围封禁牧样地, 植物在放牧干扰下表现出明显的小型化现象; 2)在群落水平上, 放牧亦显著降低了群落总生物量和茎、叶生物量; 3)过度放牧显著改变了物种的资源分配策略, 使生物量向叶的分配比例增加, 向茎的分配比例减少。资源优先向同化器官分配可能是植物对长期放牧干扰的一种重要适应对策; 4)轻度放牧对物种的资源分配没有显著影响, 单株(丛)生物量和群落茎、叶及总生物量均表现出增加趋势, 这与过度放牧的影响正好相反。过度放牧引起的植物个体小型化改变了生态系统中物种的资源分配策略, 进而对生态系统功能产生重要的影响。     

不同光环境对海南龙血树幼苗表型可塑性及生存策略的影响

为了解光照对海南龙血树(Dracaena cambodiana)幼苗生长的影响,研究了不同光照环境下海南龙血树幼苗形态、生理特性和生物量分配的变化,并分析了其生态适应性。结果表明,海南龙血树幼苗的形态、生理和生物量分配指标在不同光照强度间存在显著差异,各指标的可塑性指数为0.08~0.86,其中根茎叶及总生物量的可塑性指数普遍较高(0.67~0.86),表明海南龙血树幼苗有较好的光照适应性,其策略主要是通过调整根茎叶生物量的分配来适应光照的变化。随着光照强度的降低,海南龙血树幼苗的比叶面积、叶根比呈现显著增大趋势,表明幼苗可通过增加单株叶面积比例,扩大光合作用面积,有效调节自身生物量配置。37.3%自然光照(L2)是海南龙血树幼苗生长的最佳光照强度。现存海南龙血树生境改变,生境缺少林荫以致光照强度过大,不利于幼苗根系生长,难以度过干旱季节,可能是海南龙血树自然更新失败的重要原因之一。     

Variations and Trade‐offs in Functional Traits of Tree Seedlings during Secondary Succession in a Tropical Lowland Rain Forest

The seedling stage is generally the most important bottleneck for the successful regeneration of trees in forests. The traits of seedlings, particularly biomass allocation and root traits, are more easily quantified than the traits of adults. In this study, we tested the hypothesis that seedling traits vary and trade‐off tracking the changing environment during secondary succession. We measured the major morphological traits of 27 dominant species and the major environmental factors in a chronosequence (30‐yr‐old fallow, 60‐yr‐old fallow, and old growth forest) after shifting cultivation in a tropical lowland rain forest on Hainan Island, China. The 30‐yr‐old fallow had higher light and nutrient availability, and the older forests had higher soil water content. Redundancy analysis based on species abundance and environmental factors revealed groups of seedlings that dominate in different stages of succession. Seedlings in different stages of succession had different strategies of biomass allocation for harvesting resources that varied in availability. Species characteristic of younger forest had higher allocation to roots and higher specific leaf area, while species characteristic of older forest had higher allocation to leaves. Our study suggests that the variations and trade‐offs in the major functional traits of tree seedlings among successional classes may reflect changes in environmental conditions during succession.     

Plasticity in seedling morphology,biomass allocation and physiology among ten temperate tree species in response to shade is related to shade tolerance and not leaf habit

• Mechanisms of shade tolerance in tree seedlings, and thus growth in shade, may differ by leaf habit and vary with ontogeny following seed germination. To examine early responses of seedlings to shade in relation to morphological, physiological and biomass allocation traits, we compared seedlings of 10 temperate species, varying in their leaf habit (broadleaved versus needle‐leaved) and observed tolerance to shade, when growing in two contrasting light treatments – open (about 20% of full sunlight) and shade (about 5% of full sunlight).
• We analyzed biomass allocation and its response to shade using allometric relationships. We also measured leaf gas exchange rates and leaf N in the two light treatments.
• Compared to the open treatment, shading significantly increased traits typically associated with high relative growth rate (RGR) – leaf area ratio (LAR), specific leaf area (SLA), and allocation of biomass into leaves, and reduced seedling mass and allocation to roots, and net assimilation rate (NAR). Interestingly, RGR was not affected by light treatment, likely because of morphological and physiological adjustments in shaded plants that offset reductions of in situ net assimilation of carbon in shade. Leaf area‐based rates of light‐saturated leaf gas exchange differed among species groups, but not between light treatments, as leaf N concentration increased in concert with increased SLA in shade.
• We found little evidence to support the hypothesis of a increased plasticity of broadleaved species compared to needle‐leaved conifers in response to shade. However, an expectation of higher plasticity in shade‐intolerant species than in shade‐tolerant ones, and in leaf and plant morphology than in biomass allocation was supported across species of contrasting leaf habit.

     

Phenotypic plasticity of lianas in response to altered light environment

The growth, morphology and biomass allocation of 11 liana species (six light-demanding and five shade-tolerant) were investigated by growing plants in three contrasting light environments (i.e., field, forest edge and forest interior). Our objectives were to determine: (1) changes in plant traits at the species level; and (2) differences in light-demanding and shade-tolerant species in response to altered light environment. We found that all seedlings of liana species increased in total biomass, total leaf area, relative growth rate (RGR), net assimilation rate (NAR), height, basal diameter, root length, leaf number, root mass/total plant mass (RMR) and root-to-shoot dry biomass (R/S ratio), and decreased in leaf area ratio (LAR), specific leaf area (SLA), leaf size, stem mass-to-total plant mass ratio (SMR) and leaf mass-to-total plant mass ratio (LMR) with increasing light availability. Under the three light environments, the two types of species differed significantly in total biomass, total leaf area, RGR, NAR, LAR, SLA and leaf number, and not in leaf area. Only light-demanding species differed significantly in height, root length, basal diameter, RMR, SMR, LMR and R/S ratio. The mean plasticity index of growth and biomass allocation were relatively higher than the morphological variables, with significant differences between the two groups. Our results showed that liana species respond differently to changing light environments and that light-demanding species exhibit higher plasticity. Such differences may affect the relative success of liana species in forest dynamics.     

高寒草甸退化对鹅绒委陵菜克隆生长特征的影响

为了揭示高寒草甸典型匍匐茎克隆植物对不同生境的生态适应对策,验证生境适应假说,并为高寒草地的退化演替机理研究提供依据,以调查统计和比较样地法研究了江河源区高寒草甸退化对鹅绒委陵菜克隆生长特征的影响。研究表明,重度退化草甸的植物群落结构、功能以及土壤特征发生了明显的变化,继而对鹅绒委陵菜无性系的克隆生长行为和形态特性产生了影响。高寒草甸退化后鹅绒委陵菜的匍匐茎增多,分支强度加大。退化草甸内鹅绒委陵菜的基株高度小于未退化草甸,根长大于未退化草甸,基株的叶片数目问没有明显差别。退化草甸的分株高度显著小于未退化草甸,而分株叶数大于未退化草甸,根长小于未退化革甸且差异不显著。未退化草甸内鹅绒委陵菜无性系的问隔子长度、粗度和匍匐茎长度大于退化草甸,间隔子平均数目少于退化草甸,差异都不显著。随着鹅绒委陵菜无性系匍匐茎数目的增加,不论重度退化草甸与未退化草甸,用于鹅绒委陵菜克隆繁殖的能量投资也逐渐增加。鹅绒委陵菜在未退化草甸用于克隆繁殖的能量投资比例高于退化草甸,其中未退化草甸内鹅绒委陵菜基株的干重占无性系总生物量的比例略低于退化草甸,分株和匍匐茎的干重占无性系总生物量的比例高于退化草甸。高寒草甸退化对鹅绒委陵菜克隆生长特征的这些影响,与植物群落结构和功能的变化导致生境变异密切相关,是其对高寒草甸退化导致的资源和生境差异的反应,也是对资源利用达到的最合理状态,是一种选择适应的结果,有利于克隆繁殖潜力的发挥。同时为生境适应假说提供了又一例证。