Suaeda salsa)是滨海湿地典型植被之一, 研究其化学计量特征变化对于了解滨海湿地植被健康状况具有重要意义。该文比较了盐地碱蓬生长期、成熟期和衰退期内叶片C、N、P营养元素的化学计量特征, 并做了相关性分析。结果表明, 叶片C含量在不同生长阶段差异性显著, 生长期最低, 衰退期最高; 叶片N含量在衰退期较生长期和成熟期显著降低; 叶片P含量较为稳定, 在不同生长阶段无显著性差异。C:N、C:P在植物整个生长发育期内呈现逐渐增大的趋势, 而N:P表现出逐渐减小的趋势。相关性分析显示, 在盐地碱蓬3个不同的生长阶段, C:N和C:P与相应的N、P含量呈显著负相关, 随着N、P的变化以对数方程的形式减小; N含量与P含量之间呈显著正相关, 体现了植物体内两营养元素含量需求变化的相对一致性。同时发现, N元素已经成为滨海湿地盐地碱蓬生长发育过程中的主要限制性因子。]]>

Nitrogen (N), phosphorus (P) and their stoichiometry play pivotal roles in plant structure and functions, development and ecological strategies in terrestrial ecosystems due to their coupling with each other and their irreplaceability. Plant N and P can be influenced by biotic and abiotic factors, such as individual traits, climate change and human disturbance, and it is those factors that determine the plant community composition and structure that finally affect the ecosystem processes. According to previous studies, there is an allometric relationship between N and P. Relationships between plant N and P depend on the soil nutrient condition and species plasticity in N and P. Understanding the relationships between plant N and P in major ecological gradients can further our knowledge about vegetation restoration, succession, biodiversity, ecosystem trophic structure and biogeochemical cycles. This information could help predict potential changes in terrestrial ecosystems in response to future climate change. We review recent advances in the influencing factors and mechanism of stoichiometry in order to improve understanding of plant responses to global change.

因化学功能的耦合和元素的不可替代性, 植物对N、P的需求和利用存在严格的比例。植物N、P化学计量在不同功能群、生长地区、生长季、器官之间以及环境梯度下存在明显的变化规律。多数研究从N、P浓度、N:P及N、P间异速指数等角度分析了植物化学计量变化规律, 并探讨其在全球范围内的具体数值。为增进对植物响应全球变化的理解, 该文综述了N、P化学计量的影响因素及其机理的最新研究进展, 并指出未来拟重点研究的方向。

A global data set including 5,087 observations of leaf nitrogen (N) and phosphorus (P) for 1,280 plant species at 452 sites and of associated mean climate indices demonstrates broad biogeographic patterns. In general, leaf N and P decline and the N/P ratio increases toward the equator as average temperature and growing season length increase. These patterns are similar for five dominant plant groups, coniferous trees and four angiosperm groups (grasses, herbs, shrubs, and trees). These results support the hypotheses that (i) leaf N and P increase from the tropics to the cooler and drier midlatitudes because of temperature-related plant physiological stoichiometry and biogeographical gradients in soil substrate age and then plateau or decrease at high latitudes because of cold temperature effects on biogeochemistry and (ii) the N/P ratio increases with mean temperature and toward the equator, because P is a major limiting nutrient in older tropical soils and N is the major limiting nutrient in younger temperate and high-latitude soils.

Despite striking differences in climate, soils, and evolutionary history among diverse biomes ranging from tropical and temperate forests to alpine tundra and desert, we found similar interspecific relationships among leaf structure and function and plant growth in all biomes. Our results thus demonstrate convergent evolution and global generality in plant functioning, despite the enormous diversity of plant species and biomes. For 280 plant species from two global data sets, we found that potential carbon gain (photosynthesis) and carbon loss (respiration) increase in similar proportion with decreasing leaf life-span, increasing leaf nitrogen concentration, and increasing leaf surface area-to-mass ratio. Productivity of individual plants and of leaves in vegetation canopies also changes in constant proportion to leaf life-span and surface area-to-mass ratio. These global plant functional relationships have significant implications for global scale modeling of vegetation-atmosphere CO2 exchange.

Bringing together leaf trait data spanning 2,548 species and 175 sites we describe, for the first time at global scale, a universal spectrum of leaf economics consisting of key chemical, structural and physiological properties. The spectrum runs from quick to slow return on investments of nutrients and dry mass in leaves, and operates largely independently of growth form, plant functional type or biome. Categories along the spectrum would, in general, describe leaf economic variation at the global scale better than plant functional types, because functional types overlap substantially in their leaf traits. Overall, modulation of leaf traits and trait relationships by climate is surprisingly modest, although some striking and significant patterns can be seen. Reliable quantification of the leaf economics spectrum and its interaction with climate will prove valuable for modelling nutrient fluxes and vegetation boundaries under changing land-use and climate.

Aims Homeostasis constrains the elemental composition of individual species within narrow bounds no matter the chemical composition of the environment or the resource base. Our objective was to determine the dynamics of leaf stoichiometry during the growth period of plants and the optimum time for stoichiometry study. Methods We monitored leaf N, P stoichiometry of Scirpus mariqueter, Carex scabrifolia and Phragmites australis, the dominant species in Hangzhou Bay coastal wetlands, at different growth stages from May to October 2007. Important findings Leaf N, P stoichiometry of the Scirpus, Carex and Phragmites species showed differences: 7.41–17.12, 7.47–13.15 and 6.03–18.09 mg·g–1 for N, 0.34–2.60, 0.41–1.10 and 0.35–2.04 mg·g–1 for P, and 7.19–30.63, 11.58–16.81 and 8.62–21.86 for N:P ratios, respectively. The arithmetic means for the three species were (11.69 ± 2.66), (10.17 ± 1.53) and (11.56 ± 3.19) mg·g–1 for N, (0.93 ± 0.62), (0.74 ± 0.23) and (0.82 ± 0.53) mg·g–1 for P, and 16.83 ± 8.31, 14.53 ± 3.91 and 16.49 ± 5.51 for N:P, respectively, but there was no sig-nificant difference of N, P stoichiometry (p > 0.05). It showed high N, P concentrations at the early stage of growth because of small biomass and then decreased greatly with leaf expansion during the fast growth period, increased as leaf growth became stable and decreased again with leaf senescence. Leaf N:P was low at the early stage of growth and then increased, decreased strongly at the fast growth period, and became stable after leaf maturation.]]>

Scirpus mariqueter)、糙叶薹草(Carex scabrifolia)和芦苇(Phragmites australis)叶片N、P生态化学计量特征的季节变化。结果发现, 3种植物叶片N含量范围分别是7.41–17.12、7.47–13.15和6.03–18.09 mg·g–1, 平均值(±标准差)分别为(11.69 ± 2.66)、(10.17 ± 1.53)和(11.56 ± 3.19) mg·g–1; 叶片P范围分别是0.34–2.60、0.41–1.10和0.35–2.04 mg·g–1, 平均值为(0.93 ± 0.62)、(0.74 ± 0.23)和(0.82 ± 0.53) mg·g–1; N:P范围分别是7.19–30.63、11.58–16.81和8.62–21.86, 平均值为16.83 ± 8.31、14.53 ± 3.91和16.49 ± 5.51, 可见不同植物其生态化学计量值范围存在一定差异, 但经方差分析发现3种草本植物间生长季节内N、P元素含量差异并不显著(p > 0.05)。各物种叶片N、P含量均表现出在生长初期显著大于其他生长季节(p < 0.05), 生长旺季(6、7月)随着叶片生物量的持续增加, N、P含量逐渐降低并达到最小值, 随后8–9月叶片不再生长而N、P含量逐渐回升, 在10月叶片衰老时N、P含量再次下降; 叶片N:P则在生长初期较小, 在生长旺季先升高后降低, 随后叶片成熟不再生长时又逐渐增加并趋于稳定。]]>

Aims Leaf N and P stoichiometry has been widely studied at the species level in both aquatic and terrestrial ecosystems, however, it lacks research at the community level. Since the ecological stoichiometric characteristics could play important roles in connecting different levels of ecological studies and former studies mainly focused on the individual level, in this study, we try to figure out the pattern of foliar N and P at the community level of grassland ecosystems in Qinghai-Tibetan Plateau. Additionally, we also try to find out the relationships between community level leaf N, P and site climate factors. Methods Leaf samples were collected from 47 research sites in Qinghai-Tibetan Plateau at the end of the grow-ing season yearly from 2006 to 2008. We measured the leaf N concentrations by using an elemental analyzer and the leaf P concentration based on a molybdate/stannous chloride method. Climate data of annual mean tempera-ture and annual mean precipitation (65 national standard stations) between 2006 and 2008 were used to interpolate into gridded data with a resolution of 1 km × 1 km through the tchebycheffian spline function. Important findings Leaf N, P concentrations and N:P ratios at the community level over the southern part of Qinghai-Tibetan Plateau were 23.2 mg·g–1, 1.7 mg·g–1and 13.5, respectively. Significant inter-annual differences were presented in leaf N, P concentrations and N:P ratios. Mean annual temperature was strongly correlated with leaf N, P and N:P ratios. Besides, the correlations between climate factors and leaf N, P, N:P ratios were generally consistent with the previous results found at the global scale. Our results suggest that the high variation in leaf P concentration and its strong correlation with environmental factors reveal that, to some extent, stoichiometric traits at the community level are adaptive to local environmental conditions.]]>

–1, 平均为23.2 mg·g–1; P含量变化范围为0.8–2.8 mg·g–1, 平均为1.7 mg·g–1; N:P比值变化范围为6.8–25.6, 平均为13.5。群落叶片N含量与P含量呈显著正相关关系, 叶片的N:P比值与P含量呈显著负相关关系, N:P比值的变化主要由P含量变化决定。另外发现: 群落水平叶片N、P含量及N:P比值存在着显著的年际变化, 叶片的N、P含量及N:P比值与年平均气温之间存在着极显著的相关关系。通过该研究结果推测: P含量较高的变异系数及其与环境因子表现出的显著相关性, 在一定程度上体现了植物群落对当地气候条件的一种适应。]]>

20世纪以来，生物科学的发展异军突起，成为发展最快的学科，不仅学科分类逐渐细化，而且研究领域也逐渐深入，然而，这种分化和深入也可能会掩盖生物的一些最普遍特征。地球上的生物是否具有统一的、更本质的特征？能否把不同生物学领域和不同层次的知识联系起来？随着对这些问题的不断探索，一门新兴的学科——生态化学计量学，在最近20年悄然兴起。生态化学计量学结合了生物学、化学和物理学等基本原理，是研究生物系统能量平衡和多重化学元素（主要是C、N、P）平衡的科学。这一研究领域使得生物学科不同层次（分子、细胞、有机体、种群、生态系统和全球尺度）的研究理论能够有机地统一起来。目前，生态化学计量学已经广泛应用于种群动态、生物体营养动态、微生物营养、寄主_病原关系、生物共生关系、消费者驱动的养分循环、限制性元素的判断、生态系统比较分析和森林演替与衰退及全球C、N、P生物地球化学循环等研究中，并取得了许多研究成果。该文概述了生态化学计量的概念、历史起源和基本理论，重点介绍了生态化学计量学理论在消费者驱动的养分循环、限制性养分元素判别以及全球C、N、P循环等方面的应用进展，并对生态化学计量学未来的研究方向进行了展望，期望引起国内同行的重视并有助于推动我国在此领域开展相关研究。