Exploring patterns and mechanisms of interspecific and intraspecific variation in body elemental composition of desert consumers

Key processes such as trophic interactions and nutrient cycling are often influenced by the element content of organisms. Previous analyses have led to some preliminary understanding of the relative importance of evolutionary and ecological factors determining animal stoichiometry. However, to date, the patterns and underlying mechanisms of consumer stoichiometry at interspecific and intraspecific levels within natural ecosystems remain poorly investigated. Here, we examine the association between phylogeny, trophic level, body size, and ontogeny and the elemental composition of 22 arthropod as well as two lizard species from the coastal zone of the Atacama Desert in Chile. We found that, in general, whole‐body P content was more variable than body N content both among and within species. Body P content showed a significant phylogenetic signal; however, phylogeny explained only 4% of the variation in body P content across arthropod species. We also found a significant association between trophic level and the element content of arthropods, with carnivores having 15% greater N and 70% greater P contents than herbivores. Elemental scaling relationships across species were only significant for body P content, and even the P content scaling relationship was not significant after controlling for phylogeny. P content did decrease significantly with body size within most arthropod species, which may reflect the size dependence of RNA content in invertebrates. In contrast, larger lizards had higher P contents and lower N:P ratios than smaller lizards, which may be explained by size‐associated differences in bone and scale investments. Our results suggests that structural differences in material allocation, trophic level and phylogeny can all contribute to variation in the stoichiometry of desert consumers, and they indicate that the elemental composition of animals can be useful information for identifying broad‐scale linkages between nutrient cycling and trophic interactions in terrestrial food webs.     

Vegetation pattern formation in a fog-dependent ecosystem

Vegetation pattern formation is a striking characteristic of several water-limited ecosystems around the world. Typically, they have been described on runoff-based ecosystems emphasizing local interactions between water, biomass interception, growth and dispersal. Here, we show that this situation is by no means general, as banded patterns in vegetation can emerge in areas without rainfall and in plants without functional root (the Bromeliad Tillandsia landbeckii) and where fog is the principal source of moisture. We show that a simple model based on the advection of fog-water by wind and its interception by the vegetation can reproduce banded patterns which agree with empirical patterns observed in the Coastal Atacama Desert. Our model predicts how the parameters may affect the conditions to form the banded pattern, showing a transition from a uniform vegetated state, at high water input or terrain slope to a desert state throughout intermediate banded states. Moreover, the model predicts that the pattern wavelength is a decreasing non-linear function of fog-water input and slope, and an increasing function of plant loss and fog-water flow speed. Finally, we show that the vegetation density is increased by the formation of the regular pattern compared to the density expected by the spatially homogeneous model emphasizing the importance of self-organization in arid ecosystems.     

The elemental stoichiometry of aquatic and terrestrial ecosystems and its relationships with organismic lifestyle and ecosystem structure and function: a review and perspectives

C, N and P are three of the most important elements used to build living beings, and their uptake from the environment is consequently essential for all organisms. We have reviewed the available studies on water, soils and organism elemental content ratios (stoichiometry) with the aim of identifying the general links between stoichiometry and the structure and function of organisms and ecosystems, in both aquatic and terrestrial contexts. Oceans have variable C:N:P ratios in coastal areas and a narrow range approximating the Redfield ratio in deep water and inner oceanic areas. Terrestrial ecosystems have a general trend towards an increase in soil and plant N:P ratios from cool and temperate to tropical ecosystems, but with great variation within each climatic area. The C:N:P content ratio (from now on C:N:P ratio) is more constrained in organisms than in the water and soil environments they inhabit. The capacity to adjust this ratio involves several mechanisms, from leaf re-absorption in plants to the control of excretion in animals. Several differences in C:N:P ratios are observed when comparing different taxa and ecosystems. For freshwater ecosystems, the growth rate hypothesis (GRH), which has consistent experimental support, states that low N:P supply determines trophic web structures by favoring organisms with a high growth rate. For terrestrial organisms, however, evidence not yet conclusive on the relevance of the GRH. Recent studies suggest that the N:P ratio could play a role, even in the evolution of the genomes of organisms. Further research is warranted to study the stoichiometry of different trophic levels under different C:N:P environment ratios in long-term ecosystem-scale studies. Other nutrients such as K or Fe should also be taken into account. Further assessment of the GRH requires more studies on the effects of C:N:P ratios on anabolic (growth), catabolic (respiration), storage and/or defensive allocation. Combining elemental stoichiometry with metabolomics and/or genomics should improve our understanding of the coupling of different levels of biological organization, from elemental composition to the structure and evolution of ecosystems, via cellular metabolism and nutrient cycling.     

塔克拉玛干沙漠腹地人工植被及土壤CNP的化学计量特征

生态化学计量学是研究生态过程和生态作用中化学元素平衡的科学。极端环境中进行植物叶片与土壤中营养元素含量及变化研究,对于揭示植物对营养元素的需要和当地土壤的养分供给能力,以及植物对环境的适应与反馈能力具有十分重要的意义。以塔克拉玛干沙漠腹地塔中植物园生长良好的25种人工植被及其生境为研究对象,运用方差分析、相关分析综合研究植物叶片及土壤的化学计量特征及其相互关系。结果显示:塔克拉玛干沙漠腹地25种人工植被叶片C、N、P的平均含量分别为(386.7±46.6)、(24.7±8.1)和(1.8±0.78) mg/g;叶片C:N、C:P及 N:P分别为(17.5±6.7)、(249.2±102.8)、(15.0±5.6)。其中豆科植物N含量极显著高于非豆科植物(P<0.001)。不同生活型植物的C、N、P含量均存在显著差异,C、N、P含量在3种生活型的大小顺序为草本>灌木>乔木。C:N和N:P在不同生活型植物间不存在显著差异(P>0.05),而乔木和灌木的C:P显著高于草本植物(P< 0.05)。相关分析表明植物的叶片C:N、C:P都与相应的N、P含量呈现极显著负相关性(P<0.001),而叶片N含量与P含量的变化并不相关(P> 0.05)。土壤C、N、P养分元素含量远低于全国的平均水平,尤其是N含量(<0.2 mg/g);土壤C与N存在着极显著的正相关关系(P<0.01),而C与P、N与P间的相关性并不显著(P>0.05)。以上研究结果表明,受极端环境的限制,塔克拉玛干沙漠人工植被植物对养分元素的利用效率显著低于全国陆地植物的平均水平,不同科和不同生活型功能群植物对环境的适应能力显著不同,表现出显著的养分适应策略差异性。     

Silicon supply modifies C:N:P stoichiometry and growth of Phragmites australis

Silicon is a non-essential element for plant growth. Nevertheless, it affects plant stress resistance and in some plants, such as grasses, it may substitute carbon (C) compounds in cell walls, thereby influencing C allocation patterns and biomass production. How variation in silicon supply over a narrow range affects nitrogen (N) and phosphorus (P) uptake by plants has also been investigated in some detail. However, little is known about effects on the stoichiometric relationships between C, N and P when silicon supply varies over a broader range. Here, we assessed the effect of silicon on aboveground biomass production and C:N:P stoichiometry of common reed, Phragmites australis, in a pot experiment in which three widely differing levels of silicon were supplied. Scanning electron microscopy (SEM) showed that elevated silicon supply promoted silica deposition in the epidermis of Phragmites leaves. This resulted in altered N:P ratios, whereas C:N ratios changed only slightly. Plant growth was slightly (but not significantly) enhanced at intermediate silicon supply levels but significantly decreased at high levels. These findings point to the potential of silicon to impact plant growth and elemental stoichiometry and, by extension, to affect biogeochemical cycles in ecosystems dominated by Phragmites and other grasses and sedges.     

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.     

Parasite and host elemental content and parasite effects on host nutrient excretion and metabolic rate

Ecological stoichiometry uses the mass balance of elements to predict energy and elemental fluxes across different levels of ecological organization. A specific prediction of ecological stoichiometry is the growth rate hypothesis (GRH), which states that organisms with faster growth or reproductive rates will require higher phosphorus content for nucleic acid and protein synthesis. Although parasites are found ubiquitously throughout ecosystems, little is understood about how they affect nutrient imbalances in ecosystems. We (1) tested the GRH by determining the carbon (C), nitrogen (N), and phosphorus (P) content of parasitic trematodes and their intermediate host, the freshwater snail Elimia livescens, and (2) used this framework to determine the trematode effects on host nutrient excretion and metabolism. Snail and parasite tissues were analyzed for elemental content using a CHN analyzer and soluble reactive phosphorus (SRP) methods. Ammonium and SRP assays were used to estimate N and P excretion rates. A respirometer was used to calculate individual snail metabolism. Trematode tissues contained lower C:P and N:P (more P per unit C and N) than the snail tissues. Snail gonadal tissues more closely resembled the elemental content of parasite tissues, although P content was 13% higher in the gonad than the trematode tissues. Despite differences in elemental content, N and P excretion rates of snails were not affected by the presence of parasites. Parasitized snails maintained faster metabolic rates than nonparasitized snails. However, the species of parasite did not affect metabolic rate. Together, this elemental imbalance between parasite and host, and the altered metabolic rate of infected snails may lead to broader parasite effects in stream ecosystems.     

Plant allometry, stoichiometry and the temperature-dependence of primary productivity

Aim While physical constraints influence terrestrial primary productivity, the extent to which geographical variation in productivity is influenced by physiological adaptations and changes in vegetation structure is unclear. Further, quantifying the effect of variability in species traits on ecosystems remains a critical research challenge. Here, we take a macroecological approach and ask if variation in the stoichiometric traits (C: N: P ratios) of plants and primary productivity across global‐scale temperature gradients is consistent with a scaling model that integrates recent insights from the theories of metabolic scaling and ecological stoichiometry. Location This study is global in scope, encompassing a wide variety of terrestrial plant communities. Methods We first develop a scaling model that incorporates potentially adaptive variation in leaf and whole‐plant nutrient content, kinetic aspects of photosynthesis and plant respiration, and the allometry of biomass partitioning and allocation. We then examine extensive data sets concerning the stoichiometry and productivity of diverse plant communities in light of the model. Results Across diverse ecosystems, both foliar stoichiometry (N : P) and ‘nitrogen productivity’ (which depends on both community size structure and plant nutrient content) vary systematically across global scale temperature gradients. Primary productivity shows no relationship to temperature. Main conclusions The model predicts that the observed patterns of variation in plant stoichiometry and nutrient productivity may offset the temperature dependence of primary production expected from the kinetics of photosynthesis alone. Our approach provides a quantitative framework for treating potentially adaptive functional variation across communities as a continuum and may thus inform studies of global change. More generally, our approach represents one of the first explicit combinations of ecological stoichiometry and metabolic scaling theories in the analysis of macroecological patterns.     

基于白刺个体大小的生态化学计量模型

生态化学计量的提出为认识C、N、P耦合循环特征、驱动力及机制等提供了新方法,但植物在生长过程中的生态化学计量变化尚缺乏相关报道。本研究以唐古特白刺为对象,通过对白刺分株2017年当年生枝、2年生枝、大于2年生枝、叶、根和压条生物量及营养元素的测定,拟合了基于构件大小的元素总量,并推导了白刺各构件及整株依赖于个体大小的生态化学计量模型。结果表明: 推导模型能够反映植物在生长过程中的生态化学计量动态,老枝和压条均具有较高的N∶P与C∶P,叶、当年生枝和根均具有较低的N∶P与C∶P,白刺整株3种元素含量在生长过程中的累积速率为P>N>C。本研究结果符合现有的生长速率假说和异速生长理论,同时也可从侧面印证养分重吸收现象,该方法可作为分析植物生长过程中元素计量动态特征的一种有效途径。     

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。     

宁夏燃煤电厂周边土壤、植物和微生物生态化学计量特征及其影响因素

大气酸沉降增加对陆地生态系统的影响已得到了广泛证实,但有关酸沉降累积下工业排放源周边植被-土壤系统元素平衡特征及其影响机制的研究较少。燃煤电厂是主要的工业酸排放源之一。因此,以宁东能源化工基地3个燃煤电厂为观测点,研究了电厂周边土壤-植物叶片-微生物生态化学计量特征,分析了叶片和微生物生物量生态化学计量特征与降水降尘S、N沉降量及土壤性质的关系。结果表明：土壤和微生物生物量C ： N ： P生态化学计量特征变异系数较大,叶片各指标的变异系数较小。与受人类活动影响较少的其他同类型区相比,研究区具有较高的土壤有机C水平和N、P供给,且P相对于N丰富。植物可能主要受N限制,而微生物主要受P限制;土壤及微生物元素间均存在极显著的线性关系（P<0.001）。叶片全C与全N、全P均无显著的关系（P>0.05）。叶片全N、全P和N ： P具有高的内稳性。微生物生物量N ： P内稳性较强,但生物量N和P内稳性较弱,对土壤环境的变化反应敏感;SO₄^2-沉降有助于促进叶片对P的摄取和微生物对C、N、P的固持。少量NO₃^-沉降有利于叶片N摄取,但持续增加的NO₃^-沉降可能会使土壤P受限性增强,进而抑制叶片P摄取和微生物生物量积累。土壤酶活性、Ca²⁺和含水量亦显著影响着植物和微生物元素生态化学计量关系（P<0.05）。因此,今后还需结合多个电厂的土壤性质和植被状况,从较长时间尺度上深入揭示酸沉降增加对工业排放源周边植被-土壤系统元素平衡特征的影响机制。     

植物生态化学计量特征及其主要假说

植物生态化学计量学是生态化学计量学的重要分支, 主要研究植物器官元素含量的计量特征, 以及它们与环境因子、生态系统功能之间的关系。19世纪, 化学家们通过室内实验, 分析了植物器官的元素含量, 开始了对植物化学元素之间关系的探索。如今, 生态学家通过野外采样和控制实验, 探索植物化学元素计量特征的变化规律、对全球变化的响应以及与植物功能属性之间的关系, 促进了植物生态化学计量学的快速发展。该文在概述植物生态化学计量学发展简史的基础上, 综述了19世纪以来该领域的研究进展。首先, 该文将植物生态化学计量学的发展历程概括为思想萌芽期、假说奠基期和理论构建期3个时期, 对各个时期的主要研究进行了简要回顾和梳理。第二, 概述了植物主要器官的化学计量特征, 尤其是陆生植物叶片氮(N)和磷(P)的计量特征。总体上, 全球陆生植物叶片N、P含量和N:P (质量比)的几何平均值分别为18.74 mg∙g^-1、1.21 mg∙g^-1和15.55 (与16:1的Redfield比一致); 在物种或群落水平上, 叶片N和P含量一般呈现随温度升高、降水增加而降低的趋势。不同生活型植物叶片N和P计量特征差异明显, 尤其是草本植物叶片N和P含量高于木本植物, 落叶阔叶木本植物叶片N和P含量高于常绿木本植物。与叶片相比, 细根和其他器官化学计量特征研究较少。第三, 总结了养分添加实验对植物化学元素计量特征的影响。总体上, N添加一般会提高土壤N的可利用性, 使植物器官中N含量和N:P升高, 在一定程度上提高植物生产力; P添加可能会缓解过量N输入导致的N-P失衡问题, 提高植物器官P含量。但是, 长期过量施肥会打破植物器官原有的元素间计量关系, 导致元素计量关系失衡和生产力下降。第四, 梳理总结了植物生态化学计量学的重要理论、观点和假说, 主要包括刻画化学计量特征与植物生长功能关系的功能关联假说、刻画化学计量特征与环境因子关系的环境关联假说或理论以及刻画化学计量特征与植物进化历史关系的进化关联假说。最后, 指出了植物生态化学计量学研究中存在的问题, 展望了10个未来需要重点关注的研究方向。     

Ecological Stoichiometry and Density Responses of Plant-Arthropod Communities on Cormorant Nesting Islands

Seabirds deposit large amounts of nutrient rich guano on their nesting islands. The increased nutrient availability strongly affects plants and consumers. Consumer response differs among taxonomic groups, but mechanisms causing these differences are poorly understood. Ecological stoichiometry might provide tools to understand these mechanisms. ES suggests that nutrient rich taxa are more likely to be nutrient limited than nutrient poorer taxa and are more favored under nutrient enrichment. Here, we quantified differences in the elemental composition of soil, plants, and consumers between islands with and without nesting cormorant colonies and tested predictions made based on ES by relating the elemental composition and the eventual mismatch between consumer and resource stoichiometry to observed density differences among the island categories. We found that nesting cormorants radically changed the soil nutrient content and thereby indirectly plant nutrient content and resource quality to herbivores. In contrast, consumers showed only small differences in their elemental composition among the island categories. While we cannot evaluate the cause of the apparent homeostasis of invertebrates without additional data, we can conclude that from the perspective of the next trophic level, there is no difference in diet quality (in terms of N and P content) between island categories. Thus, bottom-up effects seemed mainly be mediated via changes in resource quantity not quality. Despite a large potential trophic mismatch we were unable to observe any relation between the invertebrate stoichiometry and their density response to nesting cormorant colonies. We conclude that in our system stoichiometry is not a useful predictor of arthropod responses to variation in resource nutrient content. Furthermore, we found no strong evidence that resource quality was a prime determinant of invertebrate densities. Other factors like resource quantity, habitat structure and species interactions might be more important or masked stoichiometric effects.     

Foliar C,N, and P stoichiometry characterize successful plant ecological strategies in the Sonoran Desert

Ecological processes are centered to water availability in drylands; however, less known nutrient stoichiometry can help explain much of their structure and ecological interactions. Here we look to the foliar stoichiometry of carbon (C), nitrogen (N), and phosphorus (P) of 38 dominant plant species from the Sonoran Desert, grouped in four different functional types to describe ecological characteristics and processes. We found that foliar N, C:N, C:P, and N:P stoichiometric ratios, but not P, were higher than those known to most other ecosystems and indicate P but not N limitations in leaves. Biological N fixers (BNF) had even higher leaf N concentrations, but bio-elemental concentrations and stoichiometry ratios were not different to other non-N-fixing legume species which underscores the need to understand the physiological mechanisms for high N, and to how costly BNF can succeed in P-limiting drylands environments. Stoichiometry ratios, and to lesser extent elemental concentrations, were able to characterize BNF and colonizing strategies in the Sonoran Desert, as well as explain leaf attribute differences, ecological processes, and biogeochemical niches in this dryland ecosystem, even when no direct reference is made to other water-limitation strategies.     

Effects of different nitrogen:phosphorus levels on the growth and ecological stoichiometry of Glycyrrhiza uralensis北大核心CSCD

Aims The increase in atmospheric nitrogen (N) deposition has accelerated N cycling of ecosystems, probably resulting in increases in phosphorus (P) demand of ecosystems. Studies on the effects of artificial N:P treatment on the growth and carbon (C), N, P ecological stoichiometry of desert steppe species could provide not only a new insight into the forecasting of how the interaction between soils and plants responses to long-term atmospheric N deposition increase, but also a scientific guidance for sustainable management of grassland in northern China under global climate change. Methods Based on a pot-cultured experiment conducted for Glycyrrhiza uralensis (an N-fixing species) during 2013 to 2014, we studied the effects of different N:P supply ratios (all pots were treated with the same amount of N but with different amounts of P) on aboveground biomass, root biomass, root/shoot ratio, and C:N:P ecological stoichiometry both in G. uralensis (leaves and roots) and in soils. Additionally, through the correlation analyses between biomass and C:N:P ecological stoichiometry in leaves, roots, and soils, we compared the differences among the C:N:P ecological stoichiometry of the three pools, and discussed the indication of C:N:P ecological stoichiometry in soils for the growth and nutrient uptake of G. uralensis. Important findings The results showed that, reducing N:P decreased C:P and N:P ratios both in G. uralensis (leaves and roots) and in soils but increased aboveground biomass and root biomass of G. uralensis, indicating that low to moderate P addition increased P availability of soils and P uptake of G. uralensis. However, excessive low N:P (high P addition) led to great decreases in soil C:P and N:P ratios, thus hindering N uptake and the growth of G. uralensis. C:N:P ratios in the two pools of G. uralensis (especially in leaves) had close correlations with soil C:N:P ratio, indicating that the change in soil C:N:P ratio would have a direct influence on plants. Our results suggest that, through regulating C:N:P ratio in leaves and soils, appropriate amounts of P addition could balance soil P supply and plant P demand and compensate the opposite influences of long-term atmospheric N deposition increase on the structure of desert steppe.     

不同基因型甘蔗种质资源的表型遗传多样性

为探明甘蔗原种和地方种的遗传多样性和亲缘关系,以期筛选出优良甘蔗种质和优良杂交亲本.该研究对18份甘蔗原种和地方种的14个数量性状进行了表型遗传多样性分析.结果表明：通过14个数量性状的变异系数(coefficient of variance,CV)和性状之间的相关分析,18份甘蔗原种和地方种的数量性状遗传变异主要来自甘蔗蔗糖分、单茎重、叶宽、茎径和纤维分;对14个数量性状进行主成分分析提取获得了4个主成分因子,分别命名为“品质因子”、“生长因子”、“成熟度因子”和“光合因子”,主成分因子累积贡献率达83．482％;进一步通过对主成分因子开展综合评价分析,获得数量性状综合表型高于平均水平的10份材料,依次为 Sampana→甜圪塔→合庆草甘蔗→桂林竹蔗→坦桑尼亚→芒戈→古芝蔗→大岛再来→托江红→春尼;聚类分析基于不同的遗传距离可将18份种质聚为5个类别,潜在的优良杂交组合是 Sampana 和甜圪塔或 Sampana 和合庆草甘蔗,表明在甘蔗遗传育种亲本选择上既要考虑各性状主要因子的互补,又要保持一定的遗传距离.该研究认为,在甘蔗育种工作中,利用因子分析法进行表型遗传多样性分析,将更加有助于亲本和杂交组合的选择.     

不同基因型甘蔗种质资源的表型遗传多样性

植物的碳、氮、磷化学计量特征能反映植物对土壤营养元素的利用效率,岩溶区植物经过长期的进化形成了自身独特的生理生态和生态化学计量特征,通过岩溶区植物叶片碳、氮、磷化学计量可以揭示岩溶生态系统各组分之间的养分循环规律.该研究在桂林毛村岩溶区次生林中选择3个20 m×20 m 的样方,采用多元统计方法分析了岩溶区森林12种典型植物叶片共186个样品的碳、氮、磷的生态化学计量特征,研究它们之间的相互关系,探讨碳、氮、磷化学计量学在岩溶生态系统中的生态指示作用.结果表明：(1)虽然岩溶区石灰土氮和磷的含量较高,但由于其有效性低,植物对养分的吸收和利用缓慢,岩溶区石灰土植物的生长仍然受到 N 和 P 的共同限制;(2)由于岩溶区植物叶片中 N 和 P 的含量显著偏低导致较高的 C∶N 和 C∶P 值(C∶N 的平均值为80．86;C∶P 的平均值为639．65);(3)利用 N∶P＜14表明氮受限制,N∶P＞16表明磷受限制,14＜N∶P＜16表明 N 和 P 共同限制的标准判断植物叶片受 N 或 P 的限制在岩溶区不完全适合;(4)元素间相关性分析表明,叶片的 C 和 N 呈极显著负相关关系(P ＜0．01),C 和 P 呈显著负相关关系(P ＜0．05),N 和 P之间呈现极显著正相关关系(P ＜0．01).这体现了植物体内两营养元素含量需求变化的相对一致性.研究结果有助于了解岩溶区森林植物的适生机制及其生态地球化学过程,可为岩溶区生态治理提供理论依据.     

新疆67种荒漠植物叶碳氮磷计量特征及其与气候的关系

荒漠生态系统具有独特的耐旱植物种类和植物化学计量特征.本研究通过系统采集全疆63个荒漠地点的67种植物,探索荒漠植物叶碳、氮、磷(C、N、P)的计量特征及其与气候因子的关系.结果表明:荒漠植物叶C、N和P的平均含量分别为394、18.4和1.14 mg·g-1,C∶N、C∶P和N∶P平均值分别为28、419和18.灌木的N含量高于乔木和草本,灌木P含量比草本(乔木)低(高);C3植物叶的C、N、C∶P、N∶P高于C4植物.随年均降水量增加,叶C有先降低后升高的趋势,叶N、P先升高、后降低,叶C∶N、C∶P与叶N、P变化趋势相反,N∶P变化不显著;随年均温升高,叶C先降低后升高,叶N、P降低,C∶N变化不显著,C∶P、N∶P升高.年均降水量对叶片化学计量特征的影响大于年均温度和植物类型.本研究结果将有助于预测全球气候变化背景下的C、N、P元素循环规律的变化,并为干旱区生物地球化学建模提供参考和基础数据.     

鄱阳湖湿地优势植物叶片-凋落物-土壤碳氮磷化学计量特征

2013年11月初在鄱阳湖南矶湿地国家级自然保护区,采集芦苇(Phragmites australis)、南荻(Triarrhena lutarioriparia)、菰(Zizania latifolia(Griseb.))、灰化苔草(Carex cinerascens)、红穗苔草(Carex argyi)和水蓼(Polygonum hydropiper)等6种优势植物新鲜叶片、凋落物及表层0—15cm土壤样品测定了碳(C)、氮(N)、磷(P)含量,以阐明不同物种、不同生活型间C、N、P化学计量差异,探讨化学计量垂直分异。结果表明:1)C、N、P含量变化范围分别为:叶片380.6—432.2 mg/g,15.3—32.6 mg/g和1.3—2.0 mg/g;凋落物345.4—416.1 mg/g,10.8—20.8 mg/g和1.1—1.7 mg/g;土壤15.0—38.1 mg/g,1.2—3.1 mg/g和0.7—1.1mg/g,不同物种间叶片、凋落物及土壤C、N、P含量差异显著,且叶片C、N、P含量显著高于凋落物与土壤。2)土壤C∶N、C∶P及N∶P值显著低于叶片与凋落物,且土壤C、N、P化学计量关系与凋落物更为密切,凋落物的C∶N、N∶P分别能解释土壤C∶N、N∶P变异的35%、18%。3)挺水植物与湿生植物之间叶片C∶N、N∶P值差异显著,C∶P则差异不显著,凋落物C∶N、C∶P与N∶P均未达到显著性差异。