Evidence of a general 2/3-power law of scaling leaf nitrogen to phosphorus among major plant groups and biomes

Scaling relations among plant traits are both cause and consequence of processes at organ-to-ecosystem scales. The relationship between leaf nitrogen and phosphorus is of particular interest, as both elements are essential for plant metabolism; their limited availabilities often constrain plant growth, and general relations between the two have been documented. Herein, we use a comprehensive dataset of more than 9300 observations of approximately 2500 species from 70 countries to examine the scaling of leaf nitrogen to phosphorus within and across taxonomical groups and biomes. Power law exponents derived from log–log scaling relations were near 2/3 for all observations pooled, for angiosperms and gymnosperms globally, and for angiosperms grouped by biomes, major functional groups, orders or families. The uniform 2/3 scaling of leaf nitrogen to leaf phosphorus exists along a parallel continuum of rising nitrogen, phosphorus, specific leaf area, photosynthesis and growth, as predicted by stoichiometric theory which posits that plants with high growth rates require both high allocation of phosphorus-rich RNA and a high metabolic rate to support the energy demands of macromolecular synthesis. The generality of this finding supports the view that this stoichiometric scaling relationship and the mechanisms that underpin it are foundational components of the living world. Additionally, although abundant variance exists within broad constraints, these results also support the idea that surprisingly simple rules regulate leaf form and function in terrestrial ecosystems.     

氮磷施肥对拟南芥叶片碳氮磷化学计量特征的影响

研究植物碳(C)氮(N)磷(P)化学计量特征, 有助于了解C、N、P元素的分配规律和确定限制植物生长的元素类型, 理解生长速率调控的内在机制。该研究基于盆栽施肥试验, 测定不同N、P供应水平下拟南芥(Arabidopsis thaliana)叶片的生物量和C、N、P含量, 分析拟南芥的限制元素类型、验证生长速率假说、探讨N、P的内稳性差异和C、N、P元素间的异速生长关系。主要结果如下: 盆栽试验基质中限制元素是P, 施N过多可能引起毒害作用; 拟南芥的生长符合生长速率假说, 即随着叶片N:P和C:P的增加, 比生长速率显著减小; 叶片P含量存在显著的调整系数(3.5), 但叶片N含量与基质N含量之间无显著相关; 叶片N和P含量具有显著的异速生长关系, 但不符合N-P^3/4关系, 施P肥导致表征N、P异速生长关系的幂指数(0.209)显著低于施N肥处理(0.466)。该研究首次基于温室培养实验分析了拟南芥C、N、P的化学计量特征及其对N、P添加的响应, 研究结果将为野外研究不同物种、群落或生态系统的化学计量特征提供参考。     

Allocation strategies for nitrogen and phosphorus in forest plants

The allocation of limiting elements, such as nitrogen (N) and phosphorus (P), in plants is an important basis for structural stability and functional optimization in natural plant communities. However, because of the lack of systematic investigation data, the mechanisms of optimal nutrient allocation in plants in natural forests are still unclear. Using consistent measurements of N and P contents in 930 plant species, we explored the allocation strategies for N and P in different plant organs and plant functional groups (PFGs) in natural communities. The N and P contents and N:P ratio were the highest in the leaf (the most active organ) at the organ level. At the PFG level, the N and P contents were higher in herbs than in woody plants, but the trend was opposite for the N:P ratio. The elemental plasticity of root was higher than that of leaf. Furthermore, at the large scale, the allometric exponents of N and P were less than 1 and showed no difference, indicating strong conservatism of the scaling relationship in plants. In summary, higher element content in more active organs, higher element plasticity in underground organs, and conservative allometric allocation among different organs and among different PFGs jointly constitute the optimal strategies for the allocation of limiting elements.     

Allometric and trait‐based patterns in parasite stoichiometry

We measured the elemental content (%C, N and P) and ratios (C:N, C:P, N:P) of a diverse assemblage of parasitic helminths to ask whether taxonomy or traits were related to stoichiometric variation among species. We sampled 27 macroparasite taxa, spanning four phyla, infecting vertebrate and invertebrate hosts from freshwater ecosystems in New Jersey. Macroparasites varied widely in elemental content, exhibiting 4.7‐fold variation in %N, 4.6‐fold variation in %P, and 11.5‐fold variation in N:P. Across all species, parasite %P scaled negatively and C:P scaled positively with body size. Similar relationships between parasite P content and body size occurred at the phylum level and within individual species. The allometric scaling of P across species supports the growth rate hypothesis, which predicts that smaller taxa require more P to support relatively higher growth rates. Life cycle stage was related to %N and C:N, with non‐reproductive parasite stages lower in %N and higher in C:N than actively reproducing parasites. Parasite phylum, functional feeding group, and trophic level did not explain elemental variation among species. Organismal stoichiometry is linked to ecological function, and wide variation in macroparasite stoichiometry likely generates diverse patterns in host–parasite nutrient dynamics and variable relationships between parasitism and nutrient cycling.     

Detrital nutrient content determines growth rate and elemental composition of bromeliad‐dwelling insects

相似文献   

湘西南石漠化地区灌丛植物叶N、P化学计量特征

以湘西南石漠化地区灌丛植物叶片为研究对象,分析了不同功能群植物以及3种不同石漠化程度(轻度、中度、重度)下植物叶片N、P化学计量特征.结果表明: 湘西南石漠化地区常见植物叶片平均N含量为12.89 g·kg^-1,P含量为1.19 g·kg^-1,N/P值为11.24,大部分植物生长受到N的限制.不同生活型之间植物叶片N含量为落叶灌木>常绿灌木>一年生草本>多年生草本,P含量与N/P值为落叶灌木>多年生草本.不同科植物之间叶片N、P含量和N/P值差异显著,禾本科植物叶片N、P含量最低,与其他科植物共同受N限制;豆科植物叶片N含量和N/P值最高,主要受P限制.双子叶植物与C3植物叶片N、P含量分别高于单子叶植物与C4植物,N/P值差异均不显著.固氮植物叶片N含量以及N/P值均高于非固氮植物,P含量差异不显著.各样地中植物叶片N、P含量之间的相关性显著,N/P值与N含量的相关性显著,仅与中度石漠化样地P含量差异显著.不同石漠化程度之间植物叶N、P含量以及N/P值差异不显著.     

Stoichiometry in an ecological context: testing for links between <Emphasis Type="Italic">Daphnia</Emphasis> P-content,growth rate and habitat preference

We used laboratory experiments with ten Daphnia taxa to test for links between Daphnia P-content, growth rate and habitat preference. The taxa represent a wide range of body sizes and most show distinct preferences for one of three habitats: shallow lakes, deep, stratified lakes or fishless ponds. Previous studies show that taxa from shallow lakes and fishless ponds experience high predation risk and rich food resources, whereas taxa from deep lakes experience low predation risk, strong food limitation and potentially P-deficient resources. Thus, we predicted higher P-content and higher maximal growth rates in taxa from ponds and shallow lakes and lower P-content, lower maximal growth but reduced sensitivity to P-limitation in taxa preferring stratified lakes. In each of 25 experiments, a clonal Daphnia cohort was cultured for 4 days on a P-sufficient (molar C:P ratio 70) or a P-deficient (C:P 1,000) diet of a green alga at a high concentration (1 mg C l^–1). The P-content of adult Daphnia fed the P-sufficient diet ranged from 1.52 to 1.22% mass. Small-bodied taxa from shallow lakes had higher P-content than larger-bodied taxa from deep lakes or fishless ponds. However, we found a nonsignificant negative correlation between P-content and growth on the P-sufficient diet, rather than the positive relationship predicted by the growth rate hypothesis. The P-deficient diet resulted in declines in both growth rate and P-content compared with the P-sufficient controls and the extent of the declines differed between taxa. Taxa from ponds showed a marginally greater decline in growth with the P-deficient diet compared with taxa from shallow or deep lakes. However, contrary to stoichiometric theory, no relationship was found between a species P-content and growth depression on the P-deficient diet. Although we found evidence for habitat adaptations, our results show that factors other than Daphnia P-content are important in determining differences between Daphnia species in both maximal growth rate and sensitivity to P-limited growth.     

N、P施肥对塔里木河上游绿洲棉花C、N、P生态化学计量特征的影响

施肥通过外源物质的添加直接干预了农田生态系统中作物元素的运移循环过程。通过野外N、P施肥试验,测定棉花各生育期碳(C)、氮(N)、磷(P)元素含量及其生物量,分析棉株C、N、P元素的分配规律,探讨棉株对生长速率调控的内在机制,获得棉株体内N、P元素的内稳性指数,并判断其限制性元素类型。结果表明:棉花C、N、P元素平均含量分别为388.7、20.97、3.43 g/kg;棉花比生长速率与N∶P、C∶P间均存在负相关关系,棉花生长符合生长速率假说;N、P元素内稳性指数H分别在1.02—5.28、1.01—4.55范围内。叶片N∶P可表征植物限制性元素类型,棉花最大生长速率所对应的叶片N∶P为13,是判断限制元素的标准;综合棉花生长速率和内稳性指数研究可知研究区棉花生长受到N、P元素的共同限制,同时,在生长前期更易受P元素的限制,生长后期更易受N元素的限制。     

Functional diversity and coexistence of herbaceous plants in wet,species‐rich savannas

Trait differences among plant species can favor species coexistence. The role that such differences play in the assembly of diverse plant communities maintained by frequent fires remains unresolved. This lack of resolution results in part from the possibility that species with similar traits may coexist because none has a significant fitness advantage and in part from the difficulty of experimental manipulation of highly diverse assemblages dominated by perennial species. We examined a 65‐year chronosequence of losses of herbaceous species following fire suppression (and subsequent encroachment by Pinus elliottii) in three wet longleaf pine savannas. We used cluster analysis, similarity profile permutation tests, and k‐R cluster analysis to identify statistically significant functional groups. We then used randomization tests to determine if the absence of functional groups near pines was greater (or less) than expected by chance. We also tested whether tolerant and sensitive species were less (or more) likely to co‐occur by chance in areas in savannas away from pines in accordance with predictions of modern coexistence theory. Functional group richness near pines was lower than expected from random species extirpations. Wetland perennials with thick rhizomes and high leaf water content, spring‐flowering wetland forbs (including Drosera tracyi), orchids, Polygala spp., and club mosses were more likely to be absent near pines than expected by chance. C3 grasses and sedges with seed banks and tall, fall‐flowering C4 grasses were less likely to be absent near pines than expected by chance. Species sensitive to pine encroachment were more likely to co‐occur with other such species away from pines at two of the three sites. Results suggest that herb species diversity in frequently burned wet savannas is maintained in part by a weak fitness (e.g., competitive) hierarchy among herbs, and not as a result of trait differences among co‐occurring species.     

Responses of foliage‐living spider assemblage composition and traits to a climatic gradient in Themeda grasslands

For speciose, but poorly known groups, such as terrestrial arthropods, functional traits present a potential avenue to assist in predicting responses to environmental change. Species turnover is common along environmental gradients, but it is unclear how this is reflected in species traits. Community‐level change in arthropod traits, other than body size, has rarely been explored across spatial scales comparable to those examined here. We hypothesized that the composition and morphological traits of spider assemblages would differ across a gradient of climate and habitat structure. We examined foliage‐living spider assemblages associated with Themeda triandra grasslands along a 900 km climatic gradient in south‐eastern Australia. We used sweep‐netting to collect T. triandra‐associated spiders and counted juveniles and identified adults. We also measured morphological traits of adult spiders and noted their hunting mode. Associations with measures of habitat structure were less consistent than relationships with climate. Both juvenile and adult spiders were more abundant in warmer sites, although species richness was not affected by temperature. We found distinct turnover in species composition along the climatic gradient, with hunting spiders, particularly crab spiders (Thomisidae), making up a greater proportion of assemblages in warmer climates. A range of traits of spiders correlated with the climatic gradient. For example, larger spider species and species that were active hunters were more common in warmer climates. Changes in morphological traits across species, rather than within species drove the morphology‐climate relationship. Strong climate‐trait correlations suggest that it may be possible to predict changes in functional traits of assemblages in response to anthropogenic disturbances such as climate change.     

Niche separation and weak interactions in the high tidal zone of saltmarsh‐mangrove mixing communities

1. Saltmarsh‐mangrove ecotones occur at the boundary of the natural geographic distribution of mangroves and salt marshes. Climate warming and species invasion can also drive the formation of saltmarsh‐mangrove mixing communities. How these coastal species live together in a “new” mixed community is important in predicting the dynamic of saltmarsh‐mangrove ecosystems as affected by ongoing climate change or human activities. To date, the understanding of species interactions has been rare on adult species in these ecotones.
2. Two typical coastal wetlands were selected as cases to understand how mangrove and saltmarsh species living together in the ecotones. The leaves of seven species were sampled from these coastal wetlands based on their distribution patterns (living alone or coexisting) in the high tidal zone, and seven commonly used functional traits of these species were analyzed.
3. We found niche separation between saltmarsh and mangrove species, which is probably due to the different adaptive strategies they adopted to deal with intertidal environments.
4. Weak interactions between coexisting species were dominated in the high tidal zone of the two saltmarsh‐mangrove communities, which could be driven by both niche differentiation and neutral theory.
5. Synthesis. Our field study implies a potential opportunity to establish a multispecies community in the high tidal zone of saltmarsh‐mangrove ecotones, where the sediment was characterized by low salinity and high nitrogen.

     

Interaction of nitrogen and phosphorus nutrition in determining growth

In this paper we discuss the differences and similarities in the growth response of tomato plants to N and P limitation, and to their interaction. Two detailed growth experiments, with varied N or P supply, were conducted in order to unravel the effects of N and P limitation on growth of young tomato plants (Lycopersicon esculentum Mill.). Relative growth rate (RGR) initially increased sharply with increasing plant P concentration but leveled off at higher plant P concentrations. In contrast, RGR increased gradually with increasing plant N concentration before it leveled off at higher plant N concentrations. The relationship of RGR with organic leaf N and P showed the same shape as with total N and P concentrations, respectively. The difference in response is most likely due to the different roles of N and P in the machinery of the plant's energy metabolism (e.g., photosynthesis, respiration). Plant N concentration decreased with increasing P limitation. We show that this decrease cannot be explained by a shift in dry-mass partitioning. Our results suggest that the decrease in N concentration with increasing P limitation may be mediated by a decrease in leaf cytokinin levels and is less likely due to decreased energy availability at low P conditions. Dry-mass partitioning to the roots was closely linearly related to the leaf reduced-N concentration. However, treatments that were severely P limited deviated from this relationship.     

黄土丘陵区不同功能群植物碳氮磷生态化学计量特征及其对微地形的响应

研究黄土丘陵区植物碳氮磷生态化学计量特征及其对微地形变化的响应,对于深入理解植物对丘陵山地环境的适应策略具有重要的意义。以黄土丘陵区森林草原带不同微地形环境(坡向、坡位)下的不同功能群植物为研究对象,对不同功能群植物叶片和细根的C、N、P含量及其化学计量特征进行了研究。结果表明:(1)叶氮含量(LN)、叶磷含量(LP)、根氮含量(RN)、根碳含量(RC)、叶碳/叶氮(LC/LN)、叶碳/叶磷(LC/LP)、叶氮/叶磷(LN/LP)、根碳/根氮(RC/RN)和根氮/根磷(RN/RP)在科属间差异显著(P0.05),而叶碳含量(LC)、根磷含量(RP)和根碳/根磷(RC/RP)在科属间差异不显著(P0.05)。(2)不同科属植物生态化学计量特征对微地形变化的响应不同,禾本科细根C/N在阴坡、阳坡差异性显著,豆科植物根N含量在不同坡位间差异显著(P0.05);菊科植物叶N含量、叶C含量、根N含量、叶片C/N和细根C/N在不同坡位间差异显著(P0.05)。(3)禾本科植物在中坡位受N、P元素共同影响,在其它坡位主要受N元素限制;豆科植物在中坡位和上坡位主要受P元素限制,在下坡位和峁顶受N、P元素共同影响;菊科植物上坡位受N、P元素共同影响,在其他坡位主要受N元素限制。研究表明,不同科属植物在不同微地形条件下受限的营养元素不同,对丘陵多变环境也存在不同的适应策略。     

Role of phosphorus and nitrogen for bacteria and phytopankton development in a large shallow lake

Nutrient (P and N) enrichment experiments in small enclosures (20 l) were carried out to determine P and/or N limitation of bacterioplankton in Lake Võrtsjärv. The specific interest of the study was to test if it is possible to detect nutrient `physiological' or growth (rate) limitation of bacterioplankton and competition for nutrients (N and P) with phytoplankton in generally nutrient rich lake. Thymidine and leucine incorporation; leucine aminopeptidase, -D-glucosidase and alkaline phosphatase activity, total count of bacteria, chlorophyll a concentration and primary production as well as the concentrations of different chemical forms of N and P were followed during 4–5 days of the experiment. To address the question of the interactions between nutrients, bacterio- and phytoplankton, experimental and seasonal data sets were included in the analyses. Phosphorus (P) had a positive effect on bacterioplankton in enclosure experiments in June 1997; no effects of nutrients were found in September 1996, while in May 1996, P affected mainly the phytoplankton. On the seasonal scale, the development of bacterioplankton was connected to primary production, total phosphorus and temperature. In enrichment experiments, bacterioplankton was mainly related with primary productivity but the possible importance of bacterial grazers could be presumed. Thus, no evidence was found for nutrient growth limitation and/or competition for N and/or P, rather bacterioplankton depended on organic food supply originating from phytoplankton.     

云南普洱季风常绿阔叶林优势物种不同生长阶段叶片碳、氮、磷化学计量特征北大核心CSCD

为探索植物叶片氮(N)、磷(P)、碳(C)生态化学计量特征随植物生长发育的变化规律,在普洱季风常绿阔叶林中,选取6种优势植物种(红锥(Castanopsis hystrix)、短刺锥(Castanopsis echidnocarpa)、泥柯(Lithocarpus fenestratus)、截果柯(Lithocarpus truncatus)、西南木荷(Schima wallichii)、茶梨(Anneslea fragrans))采集叶片,分析其N、P、C含量及化学计量比随植物生长发育的变化。结果显示:6种植物在不同生长阶段的N含量变化范围为7.90–17.72 mg·g–1,P为0.34–1.39 mg·g–1,C为458.48–516.87 mg·g–1,C:N为28.04–65.70,N:P为11.41–63.50,C:P为355.23–1 878.17,且不同生长阶段6种植物及总体叶片N、P、C含量及其化学计量比变化趋势各异。在变异系数上,N:P比整体变异最大,为36.46%(变化范围19.19%–91.65%),其次为C:P,为34.80%(变化范围15.99%–91.60%),C的整体变异最小,为3.12%(变化范围1.61%–5.89%)。变异来源分析结果显示,N含量、C含量、C:N、N:P及C:P均主要受植物生长阶段的影响,而P含量主要受物种与生长阶段的交互作用影响。     

氮磷添加对树木生长和森林生产力影响的研究进展

人为活动所导致的氮、磷输入和大气氮、磷沉降使生态系统中的氮、磷可利用性大幅提高, 对陆地生态系统的碳循环过程产生了显著影响。树木生长和森林生产力在全球碳循环中发挥着重要作用, 它决定着陆地碳固存的大小和方向。目前, 在全球范围内开展了很多氮、磷添加调控树木生长和森林生产力的野外控制实验, 但是研究结果并不一致, 受到多种生物、环境和实验处理条件等因素的影响。该文从野外氮添加和磷添加实验的文献数量、实验数量及其全球空间分布三个方面概述了氮、磷添加对树木生长和森林生产力影响的研究现状, 并总结了氮、磷添加实验中树木生长和森林生产力的评估方法, 包括相对生长速率和绝对增长量。基于相关的研究结果, 阐述了氮、磷添加影响树木生长和森林生产力的调控因素及其潜在影响机制, 包括气候、树木径级与林龄、植物功能性状(共生菌根类型、树木固氮属性和保守性与获得性性状)、植物和微生物相互作用关系、区域养分沉降速率和实验处理条件等。最后, 基于当前的研究进行了系统总结, 并指出今后需要加强的几个方面的研究, 以期为后续研究提供参考: 树木生长响应氮、磷添加的生理学机制, 树木各部分生长对氮、磷添加响应的权衡与分配, 植物功能性状在调节与预测树木生长响应氮、磷添加中的作用, 树木之间的竞争关系如何调控氮、磷添加对树木生长的影响, 以及开展长期的和联网的氮、磷添加对树木生长和森林生产力影响的野外控制实验。     

刨花楠不同相对生长速率下林木叶片碳氮磷的适应特征

分别对9年生与13年生刨花楠林木叶片氮磷养分之间关系及林木生物量相对生长速率与叶片碳氮磷化学计量比关系进行分析,探讨不同相对生长速率下的林木叶片N、P养分适应特征,并检验相对生长速率假说理论对刨花楠树种的适应性。结果表明:两种年龄刨花楠林木生物量相对生长速率、叶片C、N、P含量及其计量比值均存在显著差异;同一年龄的林木叶片N、P之间存在显著相关性,二者具有协同相关性;9年生林木叶片P含量及C∶P、N∶P与生物量相对生长速率呈二次曲线相关,而13年生林木叶片N、P含量及C∶N、C∶P、N∶P则与生物量相对生长速率均呈线性相关。研究表明,在能满足植物生长所需养分供给的土壤环境中,叶片N、P含量与林木相对生长速率间呈线性正相关,但当土壤中养分供应满足不了植物高速生长时,植物则会对有限的养分资源进行适应性调整。