Trait‐abundance relation in response to nutrient addition in a Tibetan alpine meadow: The importance of species trade‐off in resource conservation and acquisition

In competition‐dominated communities, traits promoting resource conservation and competitive ability are expected to have an important influence on species relative abundance (SRA). Yet, few studies have tested the trait‐abundance relations in the line of species trade‐off in resource conservation versus acquisition, indicating by multiple traits coordination. We measured SRA and key functional traits involving leaf economic spectrum (SLA, specific leaf area; LDMC, leaf dry matter content; LCC, leaf carbon concentration; LNC, leaf nitrogen concentration; LPC, leaf phosphorus concentration; Hs, mature height) for ten common species in all plots subjected to addition of nitrogen fertilizer (N), phosphorus fertilizer (P), or both of them (NP) in a Tibetan alpine meadow. We test whether SRA is positively related with traits promoting plant resource conservation, while negatively correlated with traits promoting plant growth and resource acquisition. We found that species were primarily differentiated along a trade‐off axis involving traits promoting nutrient acquisition and fast growth (e.g., LPC and SLA) versus traits promoting resource conservation and competition ability (e.g., large LDMC). We further found that SRA was positively correlated with plant height, LDMC, and LCC, but negatively associated with SLA and leaf nutrient concentration irrespective of fertilization. A stronger positive height‐SRA was found in NP‐fertilized plots than in other plots, while negative correlations between SRA and SLA and LPC were found in N or P fertilized plots. The results indicate that species trade‐off in nutrient acquisition and resource conservation was a key driver of SRA in competition‐dominated communities following fertilization, with the linkage between SRA and traits depending on plant competition for specific soil nutrient and/or light availability. The results highlight the importance of competitive exclusion in plant community assembly following fertilization and suggest that abundant species in local communities become dominated at expense of growth while infrequent species hold an advantage in fast growth and dispersals to neighbor meta‐communities.     

Grazing increases functional richness but not functional divergence in Tibetan alpine meadow plant communities

Plant community diversity and ecosystem function are conditioned by competition among co-occurring species for multiple resources. Previous studies suggest that removal of standing biomass by grazing decreases competition for light, but coincident grazing effects on competition for soil nutrients remain largely unknown in Tibetan rangelands where grazing tends to deplete soil phosphorus availability. We measured five functional traits indicative of plant productivity and stoichiometry leaf carbon concentration (LCC), leaf nitrogen concentration (LNC), leaf phosphorus concentration (LPC), specific leaf area (SLA), leaf dry matter content (LDMC) for component species of plant communities in grazed and ungrazed plots in five Tibetan alpine meadows. We examined the diversity of traits singly Rao index of functional diversity (FDrao) and in aggregate functional richness (FRic), functional divergence (FDiv), and functional evenness (FEve) in response to grazing. We tested whether foliar trait diversity increases with nutrient competition but decreases with light competition when competitive exclusion is reduced by grazing. The FDrao of LPC significantly increased under grazing, but FDrao for LCC, LNC and SLA tended to decrease. The FDrao of LDMC increased at the drier site but decreased at the wettest site. There was a strong negative association between increase in FDrao of LPC and decrease in soil nutrients, especially soil phosphorus availability. The FRic for all five traits together increased with species diversity following grazing, but neither FDiv nor FEve differed significantly between grazed and ungrazed plots at most sites. Grazing in Tibetan alpine meadows tends to increase competition for soil phosphorus while decreasing competition for light, resulting in an increase in the functional richness in grazed plant communities without any significant changes in the overall functional diversity of foliar traits. Our study highlights the potential importance of grazing mediated competition for multiple resources in alpine meadow ecosystems.     

去除干扰对内蒙古典型草原植物叶片功能属性的影响

以内蒙古典型草原为研究对象,选取放牧和割草、去除放牧、去除放牧和割草样地进行群落调查和叶片属性测量,比较分析各样地土壤性质、群落生产力及主要物种的比叶面积(SLA,Specific Leaf Area)、叶片干物质含量(LDMC,Leaf Dry Matter Content)、叶片氮含量(LNC,Leaf Nitrogen Concentration)在个体、功能群和群落水平对去除干扰的响应。结果表明,1)去除干扰处理在短期对土壤特性和群落生产力的影响不显著;2)多数物种在放牧和割草样地SLA较低,说明典型草原多数物种的SLA表现为放牧逃避;3)不同功能群植物叶片属性对去除干扰的响应不一致,去除放牧后,多年生杂类草的SLA和LDMC不受影响,但LNC变小;多年生禾草的SLA增加,而LDMC和LNC无显著变化。一年生植物在去除放牧和割草后,LNC显著增加。去除割草后,多年生禾草SLA减小,而多年生杂类草SLA、LNC增加,LDMC减小;4)在群落水平,放牧和割草样地由于较占优势的多年生禾草SLA较低,群落比叶面积最低,在去除放牧和割草样地,群落叶片氮含量显著增加;5)在内蒙古典型草原,LDMC能够很好地将多年生禾草和多年生杂类草区分,SLA在个体、功能群和群落水平均比LDMC敏感。     

Contrasting effects of plant inter‐ and intraspecific variation on community trait responses to restoration of a sandy grassland ecosystem

Changes in plant community traits along an environmental gradient are caused by interspecific and intraspecific trait variation. However, little is known about the role of interspecific and intraspecific trait variation in plant community responses to the restoration of a sandy grassland ecosystem. We measured five functional traits of 34 species along a restoration gradient of sandy grassland (mobile dune, semi‐fixed dune, fixed dune, and grassland) in Horqin Sand Land, northern China. We examined how community‐level traits varied with habitat changes and soil gradients using both abundance‐weighted and non‐weighted averages of trait values. We quantified the relative contribution of inter‐ and intraspecific trait variation in specific leaf area (SLA), leaf dry matter content (LDMC), leaf carbon content (LCC), leaf nitrogen content (LNC), and plant height to the community response to habitat changes in the restoration of sandy grassland. We found that five weighted community‐average traits varied significantly with habitat changes. Along the soil gradient in the restoration of sandy grassland, plant height, SLA, LDMC, and LCC increased, while LNC decreased. For all traits, there was a greater contribution of interspecific variation to community response in regard to habitat changes relative to that of intraspecific variation. The relative contribution of the interspecific variation effect of an abundance‐weighted trait was greater than that of a non‐weighted trait with regard to all traits except LDMC. A community‐level trait response to habitat changes was due largely to species turnover. Though the intraspecific shift plays a small role in community trait response to habitat changes, it has an effect on plant coexistence and the maintenance of herbaceous plants in sandy grassland habitats. The context dependency of positive and negative covariation between inter‐ and intraspecific variation further suggests that both effects of inter‐ and intraspecific variation on a community trait should be considered when understanding a plant community response to environmental changes in sandy grassland ecosystems.     

An intraspecific application of the leaf‐height‐seed ecology strategy scheme to forest herbs along a latitudinal gradient

We applied the leaf‐height‐seed (LHS) ecology strategy scheme (a combination of three ecologically important traits: specific leaf area (SLA), seed mass and plant height) intraspecifically to two widespread European forest herbs along a latitudinal gradient. The aims of this study were to quantify LHS trait variation, disentangle the environmental factors affecting these traits and compare the within‐species LHS trait relationships with latitude to previously established cross‐species comparisons. We measured LHS traits in 41 Anemone nemorosa and 44 Milium effusum populations along a 1900–2300 km latitudinal gradient from N France to N Sweden. We then applied multilevel models to identify the effects of regional (temperature, latitude) and local (soil fertility and acidity, overstorey canopy cover) environmental factors on LHS traits. Both species displayed a significant 4% increase in plant height with every degree northward shift (almost a two‐fold plant height difference between the southernmost and northernmost populations). Neither seed mass nor SLA showed a significant latitudinal cline. Temperature had a large effect on the three LHS traits of Anemone. Latitude, canopy cover and soil nutrients were related to the SLA and plant height of Milium. None of the investigated variables appeared to be related to the seed mass of Milium. The variation in LHS traits indicates that the ecological strategy determined by the position of each population in this three‐factor triangle is not constant along the latitudinal gradient. The significant increase in plant height suggests greater competitive abilities for both species in the northernmost populations. We also found that the studied environmental factors affected the LHS traits of the two species on various scales: spring‐flowering Anemone was affected more by temperature, whereas early‐summer flowering Milium was affected more by local and other latitude‐related factors. Finally, previously reported cross‐species correlations between LHS traits and latitude were generally unsupported by our within‐species approach.     

Variations in leaf morphological and chemical traits in response to life stages,plant functional types,and habitat types in an old-growth temperate forest

Intraspecific leaf trait variations are becoming a topic of interest for many ecologists because individual-based traits are essentially the drivers of variations at the community level. Six coexisting major tree species in an old-growth temperate forest, Northeast China (i.e., Abies nephrolepis, Pinus koraiensis, Acer mono, Fraxinus mandshurica, Tilia amurensis, and Ulmus laciniata) were sampled, and three habitat types (i.e., Hab I: high soil organic carbon with a moderate slope; Hab II: low soil organic carbon with a gentle slope; and Hab III: low soil organic carbon with a strong slope) were used in the plot. We performed a two-way ANOVA to compare the specific leaf area (SLA), leaf dry matter content (LDMC), leaf nitrogen content (LNC), leaf phosphorus content (LPC), and leaf carbon content (LCC) between saplings (1 < DBH ≤ 5 cm) and adults (DBH ≥ 10 cm) and between habitat types within species. We simultaneously evaluated the effects of life stage, plant functional type, and habitat type on the six leaf traits. Our results showed that life stage and habitat type had varied influences on the leaf traits of the six species. Life stage was an important determinant for all leaf traits. Plant functional type was included in the best models for SLA, LNC, and LCC. Habitat type had a greater influence on LDMC than SLA. Meanwhile, habitat type had a greater influence on LNC and LPC than LCC. The correlation between leaf traits with local environmental factors varied across different plant functional types and life stages. We suggest conducting individual-based analyses of leaf trait variations according to plant functional type and life stage to understand the plant life strategies along an environmental gradient may improve understanding of the forest dynamics in an old-growth temperate forest.     

黄土高原子午岭不同森林群落叶功能性状

对黄土高原子午岭地区5种主要森林群落中重要值>0.1的物种叶功能性状进行了比较,结果表明:1)叶干物质含量(LDMC)与比叶面积(SLA)呈负相关;SLA与叶厚度(LT)呈负相关,但与叶氮含量(LNC)和叶磷含量(LPC)呈正相关;LT与LNC、LPC和叶钾含量(LKC)呈负相关;LNC、LPC和LKC三者之间均呈正相关。2)坡位是影响叶大小(LS)、LT、LNC和LKC的主要地形因子,海拔对LPC和SLA的影响最大,而坡向则是影响LDMC的主要因子。因此,叶功能性状之间所呈现的特征及其对立地条件的适应都表现出了植物的生态策略。3)各群落间的乔木层叶功能性状均有显著差异,灌木层的叶功能性状无显著差异,而草本层除了LDMC无显著差异(P>0.05)外,其他叶功能性状均有显著差异,说明群落的叶功能性状的大小取决于群落内物种的叶功能性状及其重要值。     

摩天岭北坡森林木本植物叶性状在物种和群落水平沿海拔梯度的变化

该研究采用样线和样地相结合的方法,对甘肃省白水江国家级自然保护区摩天岭北坡大垭子梁森林不同海拔(1 600~2 100m)的植物群落进行野外调查、采样分析,并运用线性回归分析、Pearson相关性分析及曲线拟合分析方法,研究木本植物的比叶面积(SLA)、叶干物质含量(LDMC)、叶碳氮磷含量(LCC、LNC、LPC)及其计量比(C/N、C/P、N/P)等叶性状变化特征,以及在物种和群落水平随海拔梯度的变化趋势和相关性。结果表明:(1)摩天岭北坡大垭子梁山地森林为落叶阔叶林带,共有木本植物13科23种,其中乔木6种,灌木17种,且整体上灌木种类较为丰富。此外,有些物种在不同海拔间都有分布,如华北落叶松(Larix principis-rupprechtii)、胡枝子(Lespedeza bicolor)等,反映出不同植物对于异质环境的适应。(2)8个叶功能性状中变异系数最小的是LCC(4.6%),属于弱变异,最大的是SLA(42.1%),其他叶性状都属于中等变异,表明在其他叶性状的协同作用下,使得木本植物的碳获取保持在一定的水平以确保群落的稳定性。(3)叶片功能性状间的关联性普遍存在,是植物适应环境的一种对策.该研究表明SLA-LNC以及LNC-LPC在物种和群落水平上的相关性及其相关程度均一致,而其他叶性状间相关关系则有所不同,这为以后进行大尺度研究时对叶性状的选择提供了一定的依据。(4)叶性状随海拔的变化趋势,除C/N和N/P在物种和群落水平上变化趋势不一致外,其他各个性状随海拔的总体变化趋势基本一致,但显著程度只有LNC一致外其他均不同,反映了木本植物的不同叶片功能性状对海拔造成的不同环境的适应。     

松嫩草地66种草本植物叶片性状特征

植物叶片功能性状及其相互关系越来越受到关注.以松嫩草地66种草本植物为研究对象,测量叶片干物质含量、比叶面积、叶片厚度、叶片氮含量、叶片磷含量、叶绿素含量和类胡萝卜素含量,检验性状间的相互关系,比较不同功能群(多年生根茎禾草,多年生丛生禾草,多年生杂类草,1年生或2年生草本)间性状的差异性.结果表明,叶片厚度变异系数最大,比叶面积、叶片氮含量、叶片磷含量、叶绿素含量和类胡萝卜素含量之间存在显著的正相关关系;叶片于物质含量与叶片磷含量没有显著的相关关系,与其它叶片性状呈显著的负相关关系;叶片厚度只与叶片干物质含量和比叶面积呈显著的负相关关系,与其它叶片性状不相关.叶片干物质含量、比叶面积、叶片厚度、叶片氮、磷含量在4个功能群间差异显著,叶绿素含量和类胡萝卜素含量在各个功能群间差异不显著;多年生根茎禾草和多年生丛生禾草叶片的7个性状差异不显著;多年生根茎禾草和多年生丛生禾草的叶片干物质含量高于多年生杂类草和1年生或2年生草本,其它性状小于这两个功能群.     

放牧干扰对荒漠草原植物叶性状及其相互关系的影响

以宁夏退化荒漠草原优势植物牛心朴子、乳浆大戟、甘草和牛枝子为对象,分析放牧干扰对植物的比叶面积(specific leaf area, SLA)、叶干物质含量(leaf dry matter content, LDMC)、叶面积和叶干质量等叶性状的影响,探讨荒漠草原生态系统中不同物种对环境改变的响应和适应对策.结果表明: 随着放牧强度的降低,牛心朴子、乳浆大戟、甘草和牛枝子的SLA总体呈显著降低的趋势;SLA在不同放牧强度间差异显著,而LDMC则无显著差异.不同植物的叶性状相关性存在差异,牛心朴子和甘草的SLA和LDMC呈显著负相关,而乳浆大戟和牛枝子的SLA和LDMC呈正相关.牛心朴子、甘草、乳浆大戟和牛枝子的SLA对生存环境改变的反应比LDMC更敏感.植物的SLA可以作为荒漠草原植物资源利用对策的指示指标.     

海岛植物不同演替阶段植物功能性状与环境因子的变化规律

植物功能性状与环境之间的关系是功能性状研究的重点,环境因子驱使植物功能性状发生变化,进而推动群落发生演替。以平潭岛4个不同演替阶段的森林植被(灌草丛、针叶林、针阔混交林、常绿阔叶林)为研究对象,结合不同群落演替阶段的物种特征和群落结构,分析海岛不同演替阶段茎、叶功能性状的变化规律,以及功能性状与环境因子的关系。结果表明:(1)随着演替的进行,土壤养分和水分逐渐增加,土壤pH逐渐下降。比叶面积(SLA)、叶片氮含量(LNC)、叶片磷含量(LPC)、茎氮含量(SNC)、茎磷含量(SPC)下降后上升,叶厚度(LT)、叶片碳含量(LCC)、茎碳含量(SCC)与之相反,叶干物质含量(LDMC)、茎组织密度(STD)逐渐上升。(2)冗余分析表明,演替早期植物主要分布在土壤pH、容重高的贫瘠环境,拥有较高SLA、SNC、SPC、LPC的性状组合;演替后期植物主要分布在土壤养分和水分高的肥沃环境,拥有较高的STD、LDMC、LCC、LNC的性状组合。其中,土壤有机质和全氮含量是影响海岛植物演替过程中功能性状变化的关键环境因子。研究海岛植物功能性状与环境之间的关系随演替的变化规律,探讨各演替阶段功能性状和环境特征,以及功能性状如何响应环境变化。旨在为今后选择合适的树种进行海岛植被修复和重建提供依据。     

Intraspecific variability improves environmental matching,but does not increase ecological breadth along a wet‐to‐dry ecotone

It is widely assumed that higher levels of intraspecific variability in one or more traits should allow species to persist under a wider range of environmental conditions. However, few studies have examined whether species that exhibit high variability are found in a wider range of environmental conditions, and whether variability increases the ability of a species to adapt to prevailing ecological gradients. We used four plant functional traits, specific leaf area (SLA), leaf dry matter content (LDMC), leaf carbon to nitrogen ratio (C:N) and maximum plant height in 49 species across a strong environmental gradient to answer three questions: 1) is there evidence for ‘high‐variability’ species (that is, species which show high variability in multiple traits, simultaneously)? 2) are species with more variable traits present across a wider range of environmental conditions than less variable species? And 3) whether more variable species show better trait–environment matching to the prevailing abiotic (soil moisture) gradient at the site? We found little evidence for a ‘high‐variability’ species. Variability was correlated for two leaf traits, SLA and LDMC, while variability in leaf traits and plant height were not correlated. We found little evidence that more variable species were present in more diverse conditions: only variation in SLA was correlated with a wider ecological niche breadth. For plant traits along the soil‐moisture gradient, higher variability led to better trait–environment matching in half of measured traits. Overall, we found little support for the existence of ‘high‐variability’ species, but that variability in SLA is correlated with a wider ecological breadth. We also found evidence that variation in traits can improve trait–environment matching, a relationship which may facilitate our understanding ecological breadth along prevailing gradients, and community assembly on the basis of traits.     

Components of ‘competitive ability’ in the LHS model: Implication on coexistence for twelve co-occurring Mediterranean grasses

The leaf–height–seed (LHS) model has been proposed as a simple trait-based functional classification. We investigated whether the two components of competitive ability, i.e. competitive response (CR) and competitive effect (CE), are captured by the LHS model and whether these two components are independent for 12 coexisting Mediterranean grasses. Two greenhouse experiments were conducted to estimate competitive effect and response of 12 coexisting grass species from Mediterranean habitats in Jordan. We applied a phytometer design and calculated CR and CE using the relative interaction index (RII). Mature plant height, seed mass and leaf dry matter content (LDMC, used as the leaf trait) were measured for each species. Correlations and trade-offs between the three traits and the components of competitive ability, CR and CE, were analyzed with principal components analysis (PCA). The LHS model was a good predictor of competitive ability but CR and CE were independent and related to different traits. CR was positively correlated with seed mass and CE with plant height. LDMC was neither correlated to CR nor to CE. Based on these findings, we suggest that there are three primary strategies allowing coexistence in Mediterranean communities, which are related to competition: (1) large CE, i.e. large negative impact on other species associated with large stature, (2) large CR, i.e. resistance to competition associated with large seeds, and (3) competition avoidance associated with small seeds.     

井冈山鹿角杜鹃群落灌木层植物叶功能性状对海拔梯度的响应

为揭示鹿角杜鹃(Rhododendron latoucheae)群落灌木层植物叶功能性状及其对环境变化的响应趋势,对分布于井冈山不同海拔梯度鹿角杜鹃群落灌木层植物的叶功能性状进行了研究。结果表明,海拔梯度对灌木植物的叶功能性状有显著影响。随海拔的升高,叶片的干物质含量(LDMC)、厚度(LT)、氮含量(LNC)、磷含量(LPC)呈显著上升趋势,比叶面积(SLA)和N/P呈显著下降趋势,而叶大小(LS)呈先上升后下降的变化趋势;灌木植物叶片的LDMC与SLA、LS呈负相关,与LT、LNC、LPC呈正相关;SLA与LT、LNC呈负相关;LS与LT呈负相关;LNC与LPC呈正相关;N/P与LPC呈负相关;环境因子对灌木植物叶功能性状有重要影响,除受海拔的影响外,LPC、N/P还受坡位的影响,LS、LNC则分别还受到坡向和坡度的影响。因此,井冈山地区鹿角杜鹃群落灌木层植物通过改变叶功能性状来适应海拔和其它环境因子的变化。     

Plant traits link hypothesis about resource-use and response to herbivory

Grazing by large herbivores, in interplay with environmental productivity, is a key driver of the composition of the vegetation with important consequences on the ecosystem and, consequently, for land management. We tested the predictions of the resource availability – resource–acquisition theory by assessing the extent to which community averages of plant traits, known to be related to plant growth, competitive ability and response to grazing were correlated with resource gradients within local (200 km²) geographical ranges. Second, we assessed the applicability of the same set of plant traits to make inferences on ecological effects of grazing by sheep in alpine ecosystems in Norway, using a data set consisting of 16 sites in central Norway. We estimated grazing intensity by free-ranging sheep based on GPS telemetry, soil properties, plant species composition and species traits i.e. specific leaf area (SLA), leaf dry matter content (LDMC), leaf size and plant height. Soil fertility and the interaction between soil fertility and grazing, but not grazing intensity alone, were significantly related to plant species and traits composition. Generally, average SLA showed lower correspondence with soil fertility and grazing than the other traits. Leaf size and plant height were lowest at sites with high grazing intensity and in sites with low fertility, and increased with soil fertility in little and moderately grazed sites, but declined at high fertility sites when grazing was intense. LDMC showed the opposite trend. Grazing intensity was more related to the variability in plant composition and average plant traits when environmental productivity was high. Our results therefore are indicative of a convergence of responses to grazing and nutrient limitation.     

环境因子对海岛植物茎、叶功能性状的影响

植物功能性状与环境之间的关系是功能性状研究的重点,海岛作为独特的生态系统,其植物功能性状必然和大陆存在差异。为了明确海岛植被的生态适应机制,该文以平潭岛森林群落为研究对象,通过测定茎、叶10个功能性状,以及地形和土壤9个环境因子,探讨了植物功能性状之间的权衡关系,分析了环境因子对海岛植物功能性状的影响。结果表明:(1)比叶面积(SLA)与叶氮含量(LNC)、叶磷含量(LPC)呈正相关,与叶厚度(LT)、叶干物质含量(LDMC)、茎组织密度(STD)、叶碳含量(LCC)呈负相关; LDMC与LNC、茎氮含量(SNC)呈负相关; LT与STD呈正相关,与LNC和LPC呈负相关; LPC与LNC、SNC呈正相关;茎和叶C、N含量均呈正相关。(2)土壤有机质和TN是海岛植物功能性状的主要土壤影响因子。然而,由于土壤中磷含量的缺乏,LNC、茎磷含量(SPC)、SNC均与土壤全磷呈正相关; LDMC与土壤全氮呈正相关;STD与土壤有机质呈正相关; SLA随着土壤pH的增加而增加。(3)坡位和坡度是海岛植物功能性状的主要地形影响因子。SLA、SPC随着海拔上升而下降; STD、LDMC随着海拔和坡度增大而增大; LNC、LPC阴坡大于阳坡。该研究为海岛植被修复和重建提供了参考依据。     

茂兰喀斯特森林不同演替阶段植物叶片功能性状与土壤因子的关系

植物如何改变功能性状来适应环境一直是生态学的研究征点。为探究茂兰喀斯特森林不同演替阶段植物叶片的适应策略，该文以茂兰自然保护区5个不同演替阶段(草本、灌木、灌乔、乔木和顶极群落阶段)优势种为研究对象，测定不同演替阶段的优势植物叶片功能性状与土壤理化性质。结果表明：(1)随着植被正向演替的进行，土壤全氮(STN)含量、土壤有机质(SOM)含量、土壤含水量(SWC)逐渐增加，土壤全磷(STP)含量和土壤全钾(STK)含量先增加后减少，土壤pH值整体呈减小的趋势。(2)随着植被演替的进行，叶面积(LA)、叶干物质含量(LDMC)、叶厚度(LT)和叶片碳含量(LCC)逐渐上升，比叶面积(SLA)与叶片钾含量(LKC)则与之相反，叶片氮含量(LNC)呈先升后降的趋势，叶片磷含量(LPC)呈先降后升的趋势。(3)冗余分析表明，演替初期植物主要分布在土壤pH值高而STK、STP、SWC、SOM、STN相对低的环境中，群落内植物叶片采取高SLA、LNC、LPC,低LA、LDMC、LT、LWC的性状组合，演替晚期植物主要分布在土壤水分和养分含量较高的环境，LDMC、LT、LA、LWC与演替初期相比呈上升...     

东灵山地区不同森林群落叶功能性状比较

植物功能性状(plant functional trait)是近年来生态学研究的热点.其中叶功能性状(leaf functional trait)与植株生物量和植物对资源的获得、利用及利用效率的关系最为密切.研究了东灵山地区叶功能性状之间的关系、叶功能性状与地形因子的关系,并对不同群落叶功能性状进行了比较.通过Pearson相关分析发现,叶干物质含量(LDMC)与比叶面积(SLA)、叶氮浓度(LNC)、叶磷浓度(LPC)、叶钾浓度(LKC)负相关;叶大小与叶厚度正相关;SLA与 LNC、LPC、LKC正相关;LNC与LPC、LKC正相关;LPC与LKC正相关.通过灰色关联度分析发现,对叶大小、LNC、LKC来讲,海拔是各项地形因子中的首要影响因子;对LDMC、叶厚度来讲,坡度对其影响最大;对SLA、LPC来讲,坡位是其首要影响因子.依据乔木层的SLA和LDMC将5种群落分成3类,第一类是黑桦林和山杨林,第二类是辽东栎林,第三类是胡桃楸林和糠椴林.群落的分类情况符合该地带性植被优势度类型的分类情况,LDMC和SLA是最能体现群落间差异的叶功能性状.     

Plant Trait Assembly Affects Superiority of Grazer's Foraging Strategies in Species-Rich Grasslands

Background

Current plant – herbivore interaction models and experiments with mammalian herbivores grazing plant monocultures show the superiority of a maximizing forage quality strategy (MFQ) over a maximizing intake strategy (MI). However, there is a lack of evidence whether grazers comply with the model predictions under field conditions.

Methodology/Findings

We assessed diet selection of sheep (Ovis aries) using plant functional traits in productive mesic vs. low-productivity dry species-rich grasslands dominated by resource-exploitative vs. resource-conservative species respectively. Each grassland type was studied in two replicates for two years. We investigated the first grazing cycle in a set of 288 plots with a diameter of 30 cm, i.e. the size of sheep feeding station. In mesic grasslands, high plot defoliation was associated with community weighted means of leaf traits referring to high forage quality, i.e. low leaf dry matter content (LDMC) and high specific leaf area (SLA), with a high proportion of legumes and the most with high community weighted mean of forage indicator value. In contrast in dry grasslands, high community weighted mean of canopy height, an estimate of forage quantity, was the best predictor of plot defoliation. Similar differences in selection on forage quality vs. quantity were detected within plots. Sheep selected plants with higher forage indicator values than the plot specific community weighted mean of forage indicator value in mesic grasslands whereas taller plants were selected in dry grasslands. However, at this scale sheep avoided legumes and plants with higher SLA, preferred plants with higher LDMC while grazing plants with higher forage indicator values in mesic grasslands.

Conclusions

Our findings indicate that MFQ appears superior over MI only in habitats with a predominance of resource-exploitative species. Furthermore, plant functional traits (LDMC, SLA, nitrogen fixer) seem to be helpful correlates of forage quality only at the community level.