金沙江干热河谷地区植物叶片中各生源要素的化学计量特征以及异速增长关系

植物生源要素的化学计量比在生物地球化学循环以及植物生理代谢中具有极为重要的作用。迄今为止, 对植物叶片的N、P元素与其他生源要素含量间相关关系的研究较少, 限制了生态化学计量学的应用广度。为了解金沙江干热河谷地区植物叶片中各种生源要素间的异速增长关系, 该研究通过对当地51个样方中107个样本的测量, 探索个体水平、物种水平和样方水平上各生源要素间的异速增长关系。结果显示: 叶片中各元素的比例N:P:K:S:Fe:Ca为100.00:6.64:88.20:11.59:2.48:91.64, N、P含量分别为11.21和0.744 mg·g ^-1, 明显低于全国平均值, 而N:P与全国平均值相当, 表明植物生长受到N、P的双重限制。各种生源要素间存在正相关增长关系, 在个体水平上, 植物叶片中N-P大致呈等速增长关系, Fe与Ca元素相对于N、P、K的增长速率显著大于1, Fe的增长速率最大, 依次为Fe > Ca > P > N > S > K; 物种水平上Fe与Ca相对于N、P、K的增长速率显著大于1; 样方水平上, Fe元素相对于N、P、K的增长速率依旧显著大于1, 但Ca、S相对于N的增长速率显著大于1, 元素增长速率为Fe > Ca > P > S > K > N, 其中N相对于P的异速增长斜率与2/3极为接近, K相对于P的异速增长斜率接近3/4。个体水平和样方水平上各种元素间的相关关系以及拟合优度不一致, 表明群落构建在介导不同层次上元素关系中发挥着重要作用。     

Scaling of respiration to nitrogen in leaves, stems and roots of higher land plants

Using a database of 2510 measurements from 287 species, we assessed whether general relationships exist between mass-based dark respiration rate and nitrogen concentration for stems and roots, and if they do, whether they are similar to those for leaves. The results demonstrate strong respiration–nitrogen scaling relationships for all observations and for data averaged by species; for roots, stems and leaves examined separately; and for life-forms (woody, herbaceous plants) and phylogenetic groups (angiosperms, gymnosperms) considered separately. No consistent differences in the slopes of these log–log scaling relations were observed among organs or among plant groups, but respiration rates at any common nitrogen concentration were consistently lower on average in leaves than in stems or roots, indicating that organ-specific relationships should be used in models that simulate respiration based on tissue nitrogen concentrations. The results demonstrate both common and divergent aspects of tissue-level respiration–nitrogen scaling for leaves, stems and roots across higher land plants, which are important in their own right and for their utility in modelling carbon fluxes at local to global scales.     

茂兰喀斯特区68种典型植物叶片化学计量特征

研究茂兰喀斯特区不同功能(类)群植物叶片的养分含量及化学计量特征,揭示其在时间和空间尺度上的变化规律,阐明碳(C)、氮(N)、磷(P)、钾(K)等养分含量与C∶N∶P间的相互关系,探讨N∶P对该区域植物生长的指示作用,以期能够更深入的了解其养分利用状况及适生性,为喀斯特森林的稳定性及维持机制提供理论依据。以茂兰喀斯特区68种典型植物为研究对象,分别测定不同生长阶段植物叶片的C、N、P和K含量,并计算其化学计量比。结果表明:研究区68种植物分属40科62属;其叶片C、N、P和K含量的几何平均值分别为445.87 g/kg、17.32 g/kg、1.35 g/kg和9.86 g/kg,C∶N的算术平均值为26.93,C∶P、C∶K、N∶P、N∶K和P∶K的几何平均值分别为330.93、45.22、12.85、1.76和0.137;C与N呈极显著负相关,N与P、K以及P与K均呈极显著正相关,N与C∶P和C∶K、P与C∶N、C∶K和N∶K以及K与C∶N、C∶P和N∶P均呈极显著负相关,且它们之间均具有二次函数、指数函数或幂函数的非线性耦合关系;从变异程度来看,C含量为弱变异,N、P、K含量及各元素的化学计量比则均属中等变异或强变异。从植物不同生活型来比较,各生长阶段的C含量均表现为灌木乔木草本,N、P和K含量均为草本灌木乔木,各元素的化学计量比则均为乔木灌木草本。从植物不同系统发育来分析,各生长阶段蕨类植物的N、P、K含量均要高于种子植物,而各元素的化学计量比则正好相反。从不同生长阶段来看,各功能(类)群植物生长期(或生长盛期)的养分含量均要高于落叶期(或生长末期);乔木、灌木和草本等不同生活型植物落叶期的C∶P、C∶K、N∶P和N∶K均要高于生长期;蕨类植物各元素的化学计量比不同生长阶段间差异都不显著;而种子植物的C∶P、C∶K、N∶P和N∶K则均表现为落叶期生长期。对比我国其他地区及全国和全球尺度上的研究结果,该区域植物的生长发育易受N和P素的双重限制,但又因功能(类)群及生长阶段的不同其受限的养分元素也存在一定差异,体现了对高度异质的喀斯特生境不同的适应策略;而植物体内较高的K含量则可能是提高其自身抗性、适应恶劣环境的重要因素。减少人为干扰、加之适当的保护,在植物生长期配以适量的N素添加,有利于其更好的生长发育,有助于提高喀斯特森林生态系统的稳定性和抗干扰性。研究结果揭示了喀斯特森林植物的适生机制,对喀斯特森林的保护具有重要的指导意义。     

Is Mass‐based Metabolism Rate Proportional to Surface Area in Plant Leaves? A Data Re‐analysis

We re-analyzed two large published databases on leaf traits of plant species from seven different biomes, and determined the scaling relationship between leaf metabolism rate (mass-based photosynthesis capacity, Amass, and mass-based dark respiration, Rdmass) and specific leaf area (SLA) across biomes, using a standardized major axis (SMA) method. Overall pooled data produced a scaling exponent of 1.33 for the relationship between Amass and SLA, significantly larger than 1.0; and 1.04 between Rdmass and SLA. The scaling exponent of the relationship between Amass and SLA ranged between 1.23 (in tropical forest) and 1.66 (in alpine biome), and it was significantly larger in alpine (1.66) and grass/meadow (1.52) biomes than in tropical forest (1.23) and wetland (1.27). The exponent of the relationship between Rdmass and SLA, however,was much smaller in wetland (1.05) than in temperate forest (1.29) and tropical rainforest (1.65). In general, the predicated universal scaling relationship that the mass-based metabolism rate should be proportional to surface area in organisms is not applicable at the leaf-level in plants. Rather, the large slope difference of the relationship between leaf metabolism rate and SLA found among biomes indicates that the strength of the selective forces driving the scaling relationship is different among the biomes. The result basically suggests the importance of increasing SLA to plant carbon gain in stressful environments and to carbon loss in favorable habitats, and therefore has an important implication for survival strategies of plants in different biomes.     

入侵植物曼陀罗对本地植物功能性状和土壤碳、氮、磷化学计量特征的影响

为探讨不同入侵压力下入侵植物对本地植物功能性状土壤碳、氮、磷化学计量特征的影响,以入侵植物曼陀罗（Datura stramonium）及共存本地植物为研究对象,调查了无入侵区、轻度入侵区和重度入侵区（按入侵种盖度比例划分）的植物种类、株数、株高及本地植物群落的物种多样性,分析了各区入侵植物和本地植物叶片的比叶面积、碳含量、氮含量、碳氮比、叶片建成成本以及不同土层的碳、氮、磷化学计量特征。结果显示：随曼陀罗入侵压力的增加,本地植物种类及株数逐渐减少;曼陀罗株高和叶片氮含量在不同入侵压力下均显著高于本地植物,且随入侵压力的增加具有升高趋势;叶片碳氮比显著低于无入侵区本地植物;比叶面积、叶片碳含量和叶片建成成本等与入侵区本地植物相比不具有显著差异。随曼陀罗入侵压力的增加,土壤全氮含量、全碳含量、氮磷比与碳磷比显著增加,而全磷含量与碳氮比显著下降;土壤碳氮化学计量特征呈现出一定的表聚效应。这些研究结果表明,曼陀罗具有较高的资源捕获能力,并且改变了入侵地土壤特性,进而增强自身竞争能力以提高入侵力,这些可能是曼陀罗成功入侵的原因之一。     

Interspecific difference in the photosynthesis–nitrogen relationship: patterns,physiological causes,and ecological importance

The photosynthesis–nitrogen relationship is significantly different among species. Photosynthetic capacity per unit leaf nitrogen, termed as photosynthetic nitrogen-use efficiency (PNUE), has been considered an important leaf trait to characterise species in relation to their leaf economics, physiology, and strategy. In this review, I discuss (1) relations between PNUE and species ecology, (2) physiological causes and (3) ecological implications of the interspecific difference in PNUE. Species with a high PNUE tend to have high growth rates and occur in disturbed or high productivity habitats, while those with a low PNUE occur in stressful or low productivity habitats. PNUE is an important leaf trait that correlates with other leaf traits, such as leaf mass per area (LMA) and leaf life span, irrespective of life form, phylogeny, and biomes. Various factors are involved in the interspecific difference. In particular, nitrogen allocation within leaves and the mesophyll conductance for CO₂ diffusion are important. To produce tough leaves, plants need to allocate more biomass and nitrogen to make thick cell walls, leading to a reduction in the mesophyll conductance and in nitrogen allocation to the photosynthetic apparatus. Allocation of biomass and nitrogen to cell walls may cause the negative relationship between PNUE and LMA. Since plants cannot maximise both PNUE and leaf toughness, there is a trade-off between photosynthesis and persistence, which enables the existence of species with various leaf characteristics on the earth.     

Tissue nutrient concentrations in freshwater aquatic macrophytes: high inter-taxon differences and low phenotypic response to nutrient supply

1. The elemental composition and stoichiometry of aquatic plants has often been suggested to reflect the nutrient enrichment of aquatic habitats. However, the relationship is often weak. Moreover, uncertainties remain in the relevance of laboratory derived critical plant tissue nutrient concentrations to maximum yield or growth rates in the field.
2. Aquatic vascular plants and bryophytes, overlying water and sediment samples were collected to test whether freshwater aquatic macrophytes: (i) show tissue nutrient deficiencies when growing in oligotrophic freshwater habitats, and (ii) have strict homeostatic stoichiometry.
3. Plant nutrient concentrations were significantly related to total inorganic nitrogen (or nitrate), total dissolved phosphorus and sediment total phosphorus. However, these relationships were weak. Virtually all the variance in plant tissue nutrient concentrations, however, could be explained by species (taxon) identity.
4. Critical tissue nutrient concentrations for 95% maximum yield or 95% maximum growth rate in aquatic angiosperms, determined from laboratory bioassays, suggested that nutrients should not limit yield in wild aquatic macrophytes. However, there were a substantial number of samples where potential growth rate limitation was possible, particularly due to phosphorus.
5. Strict C : N : P stoichiometric ratios were found for both vascular plants and bryophytes, suggesting little scope for plants as indicators of nutrient enrichment, but provide robust stoichiometric data for studies on ecosystem metabolism and nutrient cycling.     

延河流域植物叶性状间关系及其在不同植被带的表达

以延河流域不同植被带的地带性植物群落为研究对象,对群落优势种和主要伴生种的6种叶片性状进行测定,分析这些性状及其关系随环境梯度的变化,以了解该区域植物对环境变化的适应策略.结果表明: 植物比叶面积(SLA)与叶组织密度(LTD)、叶片单位面积氮和磷含量均呈显著负相关,与单位质量叶片磷含量呈显著正相关;各性状间的尺度关系和生存对策在不同植被带不同,典型草原带和森林草原带植物LTD SLA的尺度依赖关系比森林带植物的强,而森林带植物叶片单位〖JP2〗面积N、P含量与SLA、LTD间的尺度关系较草原带更明显,植物对环境的适应策略发生了位移.在干旱贫瘠的草原带和森林草原带,植物以防御和抗胁迫策略为主,而在环境条件相对湿润、富养的森林带,植物以快速生长和资源优化配置策略为主.     

鄱阳湖湿地两种优势植物叶片C、N、P动态特征

2011年2—6月在鄱阳湖南矶湿地国家级自然保护区逐月测定了灰化苔草(Carex cinerascens)、南荻(Triarrhena lutarioriparia)叶片C、N、P含量及其地上生物量,以阐明鄱阳湖湿地优势植物C、N、P含量及化学计量比动态特征与控制因子,探讨湿地养分利用与限制状况。结果表明：1）两种优势植物叶有机碳含量变化范围分别为365.3—386.6 mg/g和352.6—393.2 mg/g,平均值(?标准差)分别为(375.5?17.4) mg/g和(371.7?12.5) mg/g;叶N含量分别为6.96—17.59 mg/g和5.50—20.68 mg/g,平均值分别为(11.35?1.40) mg/g和(11.54?0.84) mg/g;叶P含量变化范围为0.65—2.14 mg/g和0.57—2.25 mg/g,平均含量为(1.56?0.69) mg/g和(1.55?0.68) mg/g。两种植物C:N、C:P、N:P平均值分别为37.65、413.60、9.62和41.05、410.29、9.57,C、N、P及其化学计量比种间差异不显著(P>0.05)。2）气温与地上生物量是N、P及其化学计量比季节变化的主要控制因子,气温和生物量对两种优势植物叶片氮、磷含量的影响要高于对叶有机碳含量的影响。3）植物C:N、C:P与地上生物量变化趋势基本一致,显示N、P养分利用效率随植物的快速生长而提高;根据两种优势植物及土壤N、P含量与化学计量比来判断,研究区植物更多地受氮限制。     

Leaf phosphorus influences the photosynthesis–nitrogen relation: a cross-biome analysis of 314 species

The ecophysiological linkage of leaf phosphorus (P) to photosynthetic capacity (A _max) and to the A _max–nitrogen relation remains poorly understood. To address this issue we compiled published and unpublished field data for mass-based A _max, nitrogen (N) and P (n = 517 observations) from 314 species at 42 sites in 14 countries. Data were from four biomes: arctic, cold temperate, subtropical (including Mediterranean), and tropical. We asked whether plants with low P levels have low A _max, a shallower slope of the A _max–N relationship, and whether these patterns have a geographic signature. On average, leaf P was substantially lower in the two warmer than in the two colder biomes, with the reverse true for N:P ratios. The evidence indicates that the response of A _max to leaf N is constrained by low leaf P. Using a full factorial model for all data, A _max was related to leaf N, but not to leaf P on its own, with a significant leaf N ×  leaf P interaction indicating that the response of A _max to N increased with increasing leaf P. This was also found in analyses using one value per species per site, or by comparing only angiosperms or only woody plants. Additionally, the slope of the A _max–N relationship was higher in the colder arctic and temperate than warmer tropical and subtropical biomes. Sorting data into low, medium, and high leaf P groupings also showed that the A _max–N slope increases with leaf P. These analyses support claims that in P-limited ecosystems the A _max–N relationship may be constrained by low P, and are consistent with laboratory studies that show P-deficient plants have limited ribulose-1,5-bisphosphate regeneration, a likely mechanism for the P influence upon the A _max–N relation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

不同管理模式对茶树碳氮磷含量及其生态化学计量比的影响

植物不同器官的碳(C)、氮(N)、磷(P)含量及其生态化学计量特征能够反映植物内部的养分分配与平衡关系。该研究以福建安溪3种不同管理模式的铁观音茶园为研究对象, 设置了常规管理模式下的茶园(M1)、间作套种模式下的茶园(M2)和现代技术管理模式下的茶园(M3) 3种样地, 分析茶树根、茎、叶器官的C、N、P含量及其化学计量学特征, 养分的变异特征与异速生长关系。结果表明: M2和M3管理模式下茶树根、茎、叶N、P含量均显著高于M1管理模式, C含量差异不明显; 茶树根、茎、叶C:N、C:P、N:P均表现为M1 > M2 > M3。茶树不同器官C、N、P含量差异较大, 根据变异来源分析, 管理模式因素对C、N、P含量变异的影响均达到显著水平。根茎叶N-P的异速生长关系表明茶树不同器官的养分需求存在相似性; 土壤pH和容重是影响C:N、C:P、N:P的重要因素, 而土壤含水量和盐度对茶树根和叶C含量的影响较大。总体来讲, 间作套种以及现代化滴灌、水肥等管理模式可以改善茶树对养分的吸收效率, 对解决土壤养分不均衡问题具有正面效应。     

长白山森林不同演替阶段植物与土壤氮磷的化学计量特征

以长白山森林不同演替阶段的典型群落为对象,研究了不同层次优势种茎和叶化学计量特征及其与土壤因子的关系,并对不同演替阶段群落化学计量进行了比较.结果表明: 叶氮浓度(LNC)与叶磷浓度(LPC)、茎氮浓度(SNC)呈极显著正相关,与茎磷浓度(SPC)显著正相关;LPC与SNC呈显著正相关,与叶N/P、茎N/P显著负相关;叶N/P与茎N/P呈极显著正相关;SNC与SPC呈极显著正相关;SPC与茎N/P呈极显著负相关.各演替群落间的乔木层化学计量特征均有显著差异,灌木层除了叶N/P差异显著以外,其他指标均无显著差异;随演替的进行, LNC明显增加,而LPC呈减少趋势.通过RDA约束排序分析发现,演替前期植物群落主要受氮素的影响,演替中后期主要受氮磷共同影响,以磷素的作用更为强烈.     

植物叶寿命及其相关叶性状的生态学研究进展

 科学家早已注意到,具有长叶寿命的植物通常生长于营养和（或）水分较为缺乏的环境,而具短叶寿命的植物一般生长在具有较高的营养可利用性地带。国外大量的实验研究结果表明,单位重量的叶氮含量（Nmass）与叶的最大光合速率存在密切正相关,而比叶面积（单位干重量的叶面积）与植物生产单位叶面积的物质成本呈负相关,二者又随叶寿命的增加而降低,这种相互关系几乎在所有植物种群和群落中都普遍存在,反映了植物对环境适应的趋同进化特征,是进一步理解生态系统行为特征的基础。松属(Pinus)及云杉(Picea)、冷杉(Abies)等常绿针叶树种的叶寿命一般随海拔的升高而增大,其相关叶性状也普遍存在明显的垂直分布格局：随着海拔升高,单位面积的叶氮含量（Narea）及最大光合速率增加,而比叶面积则减少。一般认为,长的叶寿命是对高寒及养分、水分贫乏等胁迫环境的适应,而短的叶寿命和（或）落叶性被认为是植物为了快速生长以及对干旱或寒冬等季节性胁迫环境的适应结果。根据成本-效益分析理论,在特定环境条件下叶寿命大小取决于形成并维护单位叶面积所需要的物质消耗与叶片碳收获的平衡,与常绿/落叶森林植被纬向/垂直地带性分布存在一种内在联系机理。因此,叶寿命及其相关叶性状成为将叶片水平上的生理生态实验数据扩展到整个群落冠层乃至生物地理群区的关键因子。加强叶寿命及其相关叶性状的格局分析研究,可为现有的区域生物地球化学循环模型与植被地理模型的连接（即区域植被动态模型）提供科学依据,这将有助于从机理上解释区域植被对全球变化的适应与响应机制。但是,以往植物生理生态研究大多注重于个体叶片水平的测定,仍不清楚如何实现这些叶性状在不同尺度间的转换,尤其是从叶片水平上升至整个群落冠层。国际上至今仍缺乏在生态系统水平上的大量野外观测数据来定量描述这些叶性状与群落特征、气候因子的数量关系;国内相关研究基本尚属空白。     

Resorption proficiency and efficiency of leaf nutrients in woody plants in eastern China

Aims (i) To explore variations in nutrient resorption of woody plants and their relationship with nutrient limitation and (ii) to identify the factors that control these variations in forests of eastern China.Methods We measured nitrogen (N) and phosphorus (P) concentrations in both green and senesced leaves of 172 woody species at 10 forest sites across eastern China. We compared the nutrient resorption proficiency (NuRP) and efficiency (NuRE) of N and P in plant leaves for different functional groups; we further investigated the latitudinal and altitudinal variations in NuRP and NuRE and the impacts of climate, soil and plant types on leaf nutrient resorptions.Important findings On average, the leaf N resorption proficiency (NRP) and P resorption proficiency (PRP) of woody plants in eastern China were 11.1mg g ? 1 and 0.65 mg g ? 1, respectively; and the corresponding N resorption efficiency (NRE) and P resorption efficiency (PRE) were 49.1% and 51.0%, respectively. Angiosperms have higher NRP (are less proficient) values and lower NRE and PRE values than gymnosperms, but there are no significant differences in NRP, PRP and PRE values between species with different leaf habits (evergreen vs. deciduous angiosperms). Trees have higher NRE and PRE than shrubs. Significant geographical patterns of plant nutrient resorption exist in forests of eastern China. In general, NRP and PRE decrease and PRP and NRE increase with increasing latitude/altitude for all woody species and for the different plant groups. Plant functional groups show more controls than environmental factors (climate and soil) on the N resorption traits (NRP and NRE), while site-related variables present more controls than plant types on PRP and PRE. NRP increases and PRP and NRE decrease significantly with increasing temperature and precipitation for the overall plants and for most groups, except that significant PRE–climate relationship holds for only evergreen angiosperms. Leaf nutrient resorption did not show consistent responses in relation to soil total N and P stoichiometry, probably because the resorption process is regulated by the relative costs of drawing nutrients from soil versus from senescing leaves. These results support our hypothesis that plants growing in P-limited habitats (low latitudes/altitudes or areas with high precipitation/temperature) should have lower PRP and higher PRE, compared with their counterparts in relatively N-limited places (high latitudes/altitudes or areas with low precipitation/temperature). Our findings can improve the understanding of variations in N and P resorption and their responses to global change, and thus facilitate to incorporate these nutrient resorption processes into future biogeochemical models.     

Site fertility and leaf nutrients of sympatric evergreen and deciduous species of Quercus in central coastal California

Leaf and soil nutrient levels interact with and may each influence the other. We hypothesize that to the extent soil fertility influences the nutritional state of trees, soil fertility should correlate with summer leaf nutrient levels, whereas to the extent that trees influence soil nutrient levels, the quality of leaf litterfall should correlate with soil fertility. We examined these correlations for five sympatric oak species (genus Quercus) in central coastal California. Soil fertility, including both nitrogen and especially phosphorus, correlated significantly with summer leaf nutrient levels. In contrast, phosphorus, but not nitrogen, in the leaf litterfall correlated positively with soil nutrients. These results suggest that soil nitrogen and phosphorus influence tree nutrient levels and that leaf phosphorus, but not leaf nitrogen, influence soil fertility under the trees. Feedback between the soil and the tree for phosphorus, but not nitrogen, is apparently significant and caused by species-specific differences in leaf quality and not by litterfall quality differences within a species. We also compared functional differences between the evergreen and deciduous oak species at our study site. There were no differences in soil nitrogen and only small differences for soil phosphorus between the phenological types. Differences in leaf nutrient concentration were much more pronounced, with the evergreen species having substantially lower levels of both nitrogen and phosphorus. Evergreen species conserved more phosphorus, but not more nitrogen, than the deciduous species, but there was no consistent relationship between retranslocation and either soil nitrogen or phosphorus. These results do not support the hypothesis that evergreenness is an adaptation to low soil fertility in this system.     

Convergence and correlations among leaf size and function in seed plants: a comparative test using independent contrasts

Prior studies of a broad array of seed plants have reported strong correlations among leaf life span, specific leaf area, nitrogen concentration, and carbon assimilation rates, which have been interpreted as evidence of coordinated leaf physiological strategies. However, it is not known whether these relationships reflect patterns of evolutionary convergence, or whether they are due to contrasting characteristics of major seed plant lineages. We reevaluated a published data set for these seven traits measured in over 100 species, using phylogenetic independent contrasts calculated over a range of alternative seed plant phylogenies derived from recent molecular systematic analyses. In general, pairwise correlations among these seven traits were similar with and without consideration of phylogeny, and results were robust over a range of alternative phylogenies. We also evaluated relationships between these seven traits and lamina area, another important aspect of leaf function, and found moderate correlations with specific leaf area (0.64), mass-based photosynthesis (0.54), area-based nitrogen (−0.56), and leaf life span (−0.42). However, several of these correlations were markedly reduced using independent contrasts; for example, the correlation between leaf life span and lamina area was reduced to close to zero. This change reflects the large differences in both these traits between conifers and angiosperms and the absence of a relationship between the traits within these groups. This analysis illustrates that most interspecific relationships among leaf functional traits, considered across a broad range of seed plant taxa, reflect significant patterns of correlated evolutionary change, lending further support to the adaptive interpretation of these relationships.     

Assessing the generality of global leaf trait relationships

Global-scale quantification of relationships between plant traits gives insight into the evolution of the world's vegetation, and is crucial for parameterizing vegetation-climate models. A database was compiled, comprising data for hundreds to thousands of species for the core 'leaf economics' traits leaf lifespan, leaf mass per area, photosynthetic capacity, dark respiration, and leaf nitrogen and phosphorus concentrations, as well as leaf potassium, photosynthetic N-use efficiency (PNUE), and leaf N : P ratio. While mean trait values differed between plant functional types, the range found within groups was often larger than differences among them. Future vegetation-climate models could incorporate this knowledge. The core leaf traits were intercorrelated, both globally and within plant functional types, forming a 'leaf economics spectrum'. While these relationships are very general, they are not universal, as significant heterogeneity exists between relationships fitted to individual sites. Much, but not all, heterogeneity can be explained by variation in sample size alone. PNUE can also be considered as part of this trait spectrum, whereas leaf K and N : P ratios are only loosely related.     

C:N:P Stoichiometry and Leaf Traits of Halophytes in an Arid Saline Environment,Northwest China

Salinization is an important and increasingly prevalent issue which has broad and profound effects on plant survival and distribution pattern. To understand the patterns and potential drivers of leaf traits in saline environments, we determined the soil properties, leaf morphological traits (specific leaf area, SLA, and leaf dry matter content, LDMC), leaf chemical traits (leaf carbon, C, nitrogen, N, and phosphorus, P, stoichiometry) based on 142 observations collected from 23 sites in an arid saline environment, which is a vulnerable ecosystem in northwest China. We also explored the relationships among leaf traits, the responses of leaf traits, and plant functional groups (herb, woody, and succulent woody) to various saline environments. The arid desert halophytes were characterized by lower leaf C and SLA levels, higher N, but stable P and N:P. The leaf morphological traits were correlated significantly with the C, N, and P contents across all observations, but they differed within each functional group. Succulent woody plants had the lowest leaf C and highest leaf N levels among the three functional groups. The growth of halophytes might be more limited by N rather than P in the study area. GLM analysis demonstrated that the soil available nutrients and plant functional groups, but not salinity, were potential drivers of leaf C:N:P stoichiometry in halophytes, whereas species differences accounted for the largest contributions to leaf morphological variations. Our study provides baseline information to facilitate the management and restoration of arid saline desert ecosystem.     

Nitrogen/phosphorus leaf stoichiometry and the scaling of plant growth

We adopted previous N : P stoichiometric models for zooplankton relative growth to predict the relative growth rates of the leaves μ _L of vascular plants assuming that annual leaf growth in dry mass is dictated by how leaf nitrogen N _L is allocated to leaf proteins and how leaf phosphorus P _L is allocated to rRNA. This model is simplified provided that N _L scales as some power function of P _L across the leaves of different species. This approach successfully predicted the μ _L of 131 species of vascular plants based on the observation that, across these species, N _L scaled, on average, as the 3/4 power of P _L, i.e. N _L ∝  P     . When juxtaposed with prior allometric theory and observations, our findings suggest that a transformation in N : P stoichiometry occurs when the plant body undergoes a transition from primary to secondary growth.     

武夷山不同海拔植物水分利用效率的变化及其与养分变化的关系

以武夷山不同海拔(600、900、1300、1500、1800、2000和2100 m)的乔木、灌木和草本3种生活型植物为研究对象,观测其水分利用效率和叶片氮、磷养分浓度随海拔的变化趋势,旨在探索海拔梯度间水分、养分变化与植物水分利用效率变化的关系.结果表明: 植物水分利用效率随海拔的增加呈显著上升趋势,乔木叶片δ¹⁸O随海拔变化不显著.总体上看,叶片氮浓度未观测到规律性的变化,高海拔地区的叶片磷浓度显著高于低海拔地区.水分利用效率与叶片磷浓度呈显著正相关,而与叶片氮浓度相关性不显著.不同海拔植物水分利用效率变化主要由光合速率的变化引起,水分状况对植物水分利用效率的影响不显著.海拔梯度间植物叶片磷浓度的差异对光合速率影响显著,进而影响水分利用效率.