The Altitudinal Patterns of Leaf C∶N∶P Stoichiometry Are Regulated by Plant Growth Form,Climate and Soil on Changbai Mountain,China

Understanding the geographic patterns and potential drivers of leaf stoichiometry is critical for modelling the nutrient fluxes of ecosystems and to predict the responses of ecosystems to global changes. This study aimed to explore the altitudinal patterns and potential drivers of leaf C∶N∶P stoichiometry. We measured the concentrations of leaf C, N and P in 175 plant species as well as soil nutrient concentrations along an altitudinal transect (500–2300 m) on the northern slope of Changbai Mountain, China to explore the response of leaf C∶N∶P stoichiometry to plant growth form (PGF), climate and soil. Leaf C, N, P and C∶N∶P ratios showed significant altitudinal trends. In general, leaf C and C∶N∶P ratios increased while leaf N and P decreased with elevation. Woody and herbaceous species showed different responses to altitudinal gradients. Trees had the largest variation in leaf C, C∶N and C∶P ratios, while herbs showed the largest variation in leaf N, P and N∶P ratio. PGF, climate and soil jointly regulated leaf stoichiometry, explaining 17.6% to 52.1% of the variation in the six leaf stoichiometric traits. PGF was more important in explaining leaf stoichiometry variation than soil and climate. Our findings will help to elucidate the altitudinal patterns of leaf stoichiometry and to model ecosystem nutrient cycling.     

青藏高原东缘主要针叶树种叶片碳氮磷化学计量分布格局及其驱动因素

理解植物叶片化学计量特征及其驱动因素对认识植物种群分布规律及预测植物对环境变化响应具有重要意义。该研究采集了青藏高原东缘针叶林84个样点共29种主要针叶树种叶片, 探讨该区域常绿针叶树种叶片碳(C)、氮(N)、磷(P)化学计量特征和分布格局及其驱动因素。结果表明: (1)在科和属水平上, 不同针叶树种叶片C、N含量和C:N差异显著; 叶片N:P < 14, 表明该区域针叶树种主要受N限制。(2)叶片N、P含量在环境梯度上表现出一致的分布规律: 均呈现出随纬度和海拔增加而显著降低, 随年平均气温(MAT)和年降水量(MAP)增加而显著增加的趋势; 而叶片C含量与纬度、海拔、MAT和MAP均未表现出显著相关性。(3)叶片C:N、C:P呈现出与N、P含量变化相反的分布格局: 均随纬度和海拔增加而显著增加, 随MAT和MAP增加而显著降低; 而叶片N:P与海拔、MAT和MAP均无显著相关性。(4)进一步分析表明, 叶片C、N、P含量及其化学计量比的主要驱动因素不尽相同。具体而言: 土壤特性是叶片C含量和N:P变异的主要驱动因子, 而叶片N、P含量和C:N、C:P的变异主要由气候因素决定。总之, 该区域针叶树种叶片化学计量沿环境梯度的变异规律有力地支持了温度生物地球化学假说, 在一定程度上丰富了对环境变化下植物叶片化学计量分布格局及其驱动机制的认识。     

Stoichiometry of leaf nitrogen and phosphorus of grasslands of the Inner Mongolian and Qinghai-Tibet Plateaus in relation to climatic variables and vegetation organization levels

Nitrogen (N) and phosphorus (P) are most commonly the limiting essential elements that affect the functioning of plants and ecosystems. However, their stoichiometry in relation to climatic variables and vegetation organization levels has not been comprehensively characterized. N and P concentrations were measured for 329 leaf samples collected at 132 sites along the 5000 km long China Grassland Transect that traverses the Inner Mongolian and Qinghai-Tibet Plateaus. The patterns of these measurements were analyzed with reference to climate factors, plant species, plant functional groups, grassland communities and grassland ecosystems. The aim was to explore whether geographical patterns of plant leaf elements are related to zonal climatic variables, and at which vegetation organization levels changes of plant leaf N and P stoichiometric characteristics and pattern occur. Results showed that interspecific differences of N and P concentrations were most significant for the three vegetation organization levels of species, community and ecosystem. Plant leaf N and P concentrations were higher, coefficients of variation of N and P lower, and N/P, C/N and C/P ratios were also lower for leaf samples from the cold high altitude Qinghai-Tibet Plateau than for those from the relatively lower altitude and warmer Inner Mongolian Plateau. Correlation of N and P for Inner Mongolian grassland was higher than that for the Qinghai-Tibet Plateau. The study indicates plant species are the most basic unit influencing plant stoichiometric geographic patterns, and that climatic variables affect leaf element concentrations mainly through their effect on changes of plant species composition of vegetation.     

Stoichiometry and large-scale patterns of leaf carbon and nitrogen in the grassland biomes of China

Nitrogen (N) and carbon–nitrogen (C:N) ratio are key foliar traits with great ecological importance, but their patterns across biomes have only recently been explored. We conducted a systematic census of foliar C, N and C:N ratio for 213 species, from 41 families over 199 research sites across the grassland biomes of China following the same protocol, to explore how different environmental conditions and species composition affect leaf N and C:N stoichiometry. Leaf C:N stoichiometry is stable in three distinct climatic regions in Inner Mongolia, the Tibetan Plateau, and Xinjiang Autonomous Region, despite considerable variations among co-existing species and among different vegetation types. Our results also show that life form and genus identity explain more than 70% of total variations of foliar N and C:N ratio, while mean growing season temperature and growing season precipitation explained only less than 3%. This suggests that, at the biome scale, temperature affects leaf N mainly through a change in plant species composition rather than via temperature itself. When our data were pooled with a global dataset, the previously observed positive correlation between leaf N and mean annual temperature (MAT) at very low MATs, disappeared. Thus, our data do not support the previously proposed biogeochemical hypothesis that low temperature limitations on mineralization of organic matter and N availability in soils lead to low leaf N in cold environments.     

松嫩草地80种草本植物叶片氮磷化学计量特征

以松嫩草地常见草本植物为研究对象, 分析了各生活型和功能群叶片氮磷化学计量特征。结果显示: 松嫩草地80种草本植物的叶片氮、磷质量浓度分别为(24.2 ± 0.96) mg·g ^-1和(2.0 ± 0.10) mg·g ^-1, 面积浓度分别为(13.0 ± 0.54) mg·cm ^-2和(1.0 ± 0.05) mg·cm ^-2, 氮磷比为13.0 ± 0.39, 氮磷比与叶片磷质量浓度、叶片氮、磷面积浓度有显著相关关系; 松嫩草地植物生长受到氮限制。一年生植物叶片氮、磷质量浓度和变异系数高于其他生活型, 各生活型之间氮面积浓度和氮磷比差异不显著。豆科植物叶片氮的质量浓度、面积浓度和氮磷比高于其他功能群。在不同生活型或功能群之间, 植物叶片磷的面积浓度差异不显著, 都在1.0 mg·cm ^-2左右; 适当地增加群落中豆科植物的比例, 可能有助于提高松嫩草地产量和质量。     

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.     

Close linkages between leaf functional traits and soil and leaf C:N:P stoichiometry under altered precipitation in a desert steppe in northwestern China

Leaf functional traits are important for characterizing plant nutrient strategies. The C:N:P stoichiometric balance in soils and plants, which could indicate types of nutrient limitation, is altered under changing precipitation patterns. However, whether such alterations affect leaf functional traits remains unclear. We conducted a three-year simulated precipitation experiment in a desert steppe in northwestern China to determine changes in leaf photosynthetic traits and nutrient conservation traits in five plant species and tested the relationships of these traits with soil and leaf C:N:P stoichiometry. The five species showed few changes in their leaf traits under drought conditions, but they adjusted these traits (especially P traits) under extremely wet conditions (50% increase in precipitation). Improved leaf photosynthetic N and P use, lowered leaf P uptake, and enhanced leaf N resorption might help Lespedeza potaninii to rely less on soil nutrients in extremely wet environments than other species do. Leaf photosynthetic traits were regulated primarily by soil and leaf C:N:P stoichiometry. Leaf nutrient conservation traits were controlled by both leaf C:N:P stoichiometry and soil properties (i.e., enzyme activity and microbial biomass), a condition especially true for P traits. The results suggest that precipitation-induced alteration in the C:N:P stoichiometric balance might have important influences on plant nutrient use strategies and even on the nutrient cycling of desert steppes.

     

内蒙古草地叶片磷含量与土壤有效磷的关系

植物体内特别是叶片的P含量特征及其与环境的关系一直是植物生理生态学研究的一个热点。已有研究发现, 与全球植物数据相比, 中国植物叶片的P含量相对较低, 导致N/P高于全球平均水平, 并推测这是由于中国土壤全P含量较低引起的。该研究选取内蒙古草地来验证这一假设, 分析了36个样地57种优势植物叶片的P含量与土壤全P和有效P含量的关系。主要结果如下: 内蒙古草地叶片P含量较低而N/P较高, 与之前的研究结论一致; 在种群、样地和物种3个水平上, 叶片P含量、N/P与土壤P含量都没有显著的相关关系, 尽管土壤有效P含量的解释力高于土壤全P; 另一方面, 内蒙古草地土壤的有效P含量与全国土壤普查的结果接近, 高于美国及澳大利亚的平均值, 但低于世界土壤信息库里报道的全球土壤有效P平均值。鉴于内蒙古草地土壤的全P和有效P含量都不能准确反映叶片P含量, 且土壤的有效P含量也并不明显低于世界其他地区, 因此植物叶片P含量低、N/P高是由于土壤P含量低引起的这一假设在内蒙古草地不成立, 而且叶片P含量也与土壤P的可利用性无关。     

阿拉善荒漠区6种主要灌木植物叶片C:N:P化学计量比的季节变化

为了解同一生活型不同种植物叶片碳(C)、氮(N)、磷(P)生态化学计量学特征随季节变化的响应规律,在生长季不同月份,对阿拉善荒漠区6种主要灌木植物霸王(Zygophyllum xanthoxylum)、白刺(Nitraria tangutorum)、红砂(Reaumuria soongorica)、驼绒藜(Ceratoideslatens)、猫头刺(Oxytropis aciphylla)、沙冬青(Ammopiptanthus mongolicus)的物候期进行了连续的观察,并采集植物叶片,分析了其C、N、P含量及计量比在不同月份的变化.结果显示:1)同一生活型的6种植物的叶片C、N、P及C:N、C:P和N:P在整个生长季内的变化规律不同,且以上各指标季节间的变异系数在6种植物之间也存在差异;2)单个植物种叶片C、N、P含量及其计量比的季节变异分析显示,叶片C、N含量及C:N的季节变异较小,叶片P含量及C:P和N:P的季节变异较大,6种植物叶片C、N含量及C:N由于季节变异所计算的变异系数变化范围分别为0.60％-10.20％、6.09％-20.50％和5.87％-18.78％,6种植物叶片P含量的季节变异所产生的变异系数范围为16.43％-43.43％,叶片C:P和N:P的变异系数范围分别为8.48％-31.95％和11.86％-40.73％;3)综合分析6种植物叶片C、N、P及其计量比各指标在整个生长季节内的变异,变异系数由大到小排序为:P(28.85％)＞C:P(25.02％)＞N:P(22.18％)＞N(14.22％)＞C:N(12.48％)＞C(4.62％);4)生长季节与植物种类对植物叶片C、N、P及其计量比影响的交叉分析显示,植物叶片C、N含量的变异主要受植物种类影响,植物叶片P含量的变异主要受生长季节影响,植物叶片C:N、C:P和N:P的变异都主要受植物种类影响.     

Nutrient levels within leaves,stems, and roots of the xeric species Reaumuria soongorica in relation to geographical,climatic, and soil conditions

Besides water relations, nutrient allocation, and stoichiometric traits are fundamental feature of shrubs. Knowledge concerning the nutrient stoichiometry of xerophytes is essential to predicting the biogeochemical cycling in desert ecosystems as well as to understanding the homoeostasis and variability of nutrient traits in desert plants. Here, we focused on the temperate desert species Reaumuria soongorica and collected samples from plant organs and soil over 28 different locations that covered a wide distributional gradient of this species. Carbon (C), nitrogen (N), and phosphorus (P) concentrations and their stoichiometry were determined and subsequently compared with geographic, climatic, and edaphic factors. The mean leaf C, N, and P concentrations and C/N, C/P, and N/P ratios were 371.6 mg g⁻¹, 10.6 mg g⁻¹, 0.73 mg g⁻¹, and 59.7, 837.9, 15.7, respectively. Stem and root C concentrations were higher than leaf C, while leaf N was higher than stem and root N. Phosphorus concentration and N/P did not differ among plant organs. Significant differences were found between root C/N and leaf C/N as well as between root C/P and leaf C/P. Leaf nutrient traits respond to geographic and climatic factors, while nutrient concentrations of stems and roots are mostly affected by soil P and pH. We show that stoichiometric patterns in different plant organs had different responses to environmental variables. Studies of species-specific nutrient stoichiometry can help clarify plant–environment relationships and nutrient cycling patterns in desert ecosystems.     

Variation in leaf nitrogen and phosphorus stoichiometry in the nitrogen-fixing Chinese sea-buckthorn (Hippophae rhamnoides L. subsp. sinensis Rousi) across northern China

Nitrogen (N) and phosphorus (P) concentrations and N:P ratios in terrestrial plants and their patterns of change along environmental gradients are important traits for plant adaptation to changes. We determined the leaf N and P concentrations of Chinese sea-buckthorn (Hippophae rhamnoides L. subsp. sinensis Rousi), a non-legume species with symbiotic N fixation (SNF), at 37 sites across northern China and explored their geographical patterns in relation to climate and soil factors. (1) The mean leaf N, P, and N:P ratio were 36.5, 2.1 mg g^?1, and 17.6, respectively, higher than the mean values of most shrub species in the region. (2) Leaf N was correlated with soil mineral N in cool areas (mean annual temperature MAT <3 °C) but with temperature in warm areas (MAT >3 °C). The high leaf N and divergent leaf N–soil N relationship suggested the importance of SNF in plant N uptake; SNF increases with temperature and is probably the major N source in warm areas. (3) Leaf P was positively related to mean annual precipitation. Leaf N:P ratio was primarily driven by changes in leaf P. The high leaf P reflected the greater requirements of the N-fixing species for P. Our results represent a major advance in understanding the elemental stoichiometry of non-legume N-fixing plants, indicating high P and N requirements and a shift in N source from SNF to soil as temperature declines. This knowledge will help in assessing the habitat suitability for the species and predicting the species dynamics under environmental changes.     

滇池流域富磷区不同土壤磷水平下植物叶片的养分化学计量特征

滇池流域是我国典型的富磷区, 分析该区域内不同土壤磷含量下主要植物的化学计量特征, 有助于理解该区域的生态环境特点和生态恢复的特殊性。该研究测定了滇池流域滇中地区75种常见植物叶片的碳(C)、氮(N)、磷(P)及钾(K)含量, 综合分析了该区域不同土壤磷水平(富磷和正常)下不同生活型植物叶片的C、N、P和K的计量特征。结果表明, 研究区域植物叶片C、N和K含量的算术平均数分别是441.42、16.17和13.57 mg·g^-1, P含量的几何平均数为1.92 mg·g^-1, 植物叶片的N、P和K含量之间呈显著的正相关; 富磷区域植物叶片的P和K含量显著高于正常区域, N/P、K/P显著低于正常区域。无论是富磷还是正常区域, 草本植物的N、P和K含量均高于木本植物, 乔木与灌木差异不明显。植物叶片的P含量及N/P与土壤磷水平呈显著相关; 叶片N/P分析结果表明, N是影响滇池流域植物生长和群落恢复的主要限制元素。研究指出, 在滇池流域增加陆地植物群落及生态系统的氮素来源是进行生态修复和面源污染防治的重要切入点。     

基于地理种源的刨花楠苗木比叶面积与叶片化学计量学关系

探讨植物比叶面积(SLA)与叶片碳(C)、氮(N)、磷(P)化学计量学关系,能够反映植物为获取最大光合生产所采取的内部调控机制,共同体现植物的适应策略。利用生长于同一土壤与气候环境中培育的刨花楠(Machilus pauhoi)1年生苗木,对其SLA与叶片C、N、P含量进行测定,并对SLA与叶片C、N、P化学计量学特征及其与种源地环境因子的关系进行分析。结果表明:(1)叶片养分含量的变异系数大小排序为CNP;SLA与叶片N、P含量呈显著的正相关,与叶片C∶N及C∶P呈极显著的负相关。(2)SLA与经度、年均温、年降水量呈显著负相关;叶片C、N、P含量也受种源地环境因子影响,其中以海拔最为重要。研究结果有助于理解刨花楠苗木的生存适应对策,对探究刨花楠对养分的资源利用效率等具有重要意义。     

Taxonomic identity, phylogeny, climate and soil fertility as drivers of leaf traits across Chinese grassland biomes

Although broad-scale inter-specific patterns of leaf traits are influenced by climate, soil, and taxonomic identity, integrated assessments of these drivers remain rare. Here, we quantify these drivers in a field study of 171 plant species in 174 sites across Chinese grasslands, including the Tibetan Plateau, Inner Mongolia, and Xinjiang. General linear models were used to partition leaf trait variation. Of the total variation in leaf traits, on average 27% is due to taxonomic or phylogenetic differences among species within sites (pure species effect), 29% to variation among sites within species (pure site effect), 38% to joint effects of taxonomic and environmental factors (shared effect), and 6.2% to within-site and within-species variation. Examining the pure site effect, climate explained 7.8%, soil explained 7.4%, and climate and soil variables together accounted for 11%, leaving 18% of the inter-site variation due to factors other than climate or soil. The results do not support the hypothesis that soil fertility is the “missing link” to explain leaf trait variation unexplained by climatic factors. Climate- and soil-induced leaf adaptations occur mostly among species, and leaf traits vary little within species in Chinese grassland plants, despite strongly varying climate and soil conditions.     

Leaf nitrogen and phosphorus concentrations of woody plants differ in responses to climate,soil and plant growth form

Leaf chemistry is important in predicting the functioning and dynamics of ecosystems. As two key traits, leaf nitrogen (N) and phosphorus (P) concentrations set the limits for plant growth, and leaf N:P ratios indicate the shift between N‐ and P‐limitation. To understand the responses of leaf chemistry to their potential drivers, we measured leaf N and P concentrations of 386 woody species at 14 forest sites across eastern China, and explored the effects of climate, soil, and plant growth form on leaf N, P and N:P ratios. In general, leaf N and P were both negatively related to mean annual temperature and precipitation, and positively related to soil N and P concentrations. Leaf N:P ratios showed opposite trends. General linear models showed that variation in leaf N was mainly determined by a shift in plant growth form (from evergreen broadleaved to deciduous broadleaved to conifer species) along the latitudinal gradient, while variations in leaf P and N:P were driven by climate, plant growth form, and their interaction. These differences may reflect differences in nutrient cycling and physiological regulations of P and N. Our results should help understand the ecological patterns of leaf chemical traits and modeling ecosystem nutrient cycling.     

陕西省3种主要树种叶片、凋落物和土壤N、P化学计量特征

以陕西省29个县(市)39个样点的刺槐、辽东栎和油松林为研究对象,分析比较不同树种乔木叶片、凋落物与土壤N、P化学计量特征及其与经纬度、海拔、年均温度和年降水等环境因子间关系的异同以及三者之间可能存在的关系,以期为认识陕西省主要森林树种养分限制状况、制定合理的植被管理和恢复措施提供理论依据。结果表明:3树种叶片N、P含量及比值均为刺槐辽东栎油松,与叶片相比,凋落物中N、P含量变化幅度较小,为刺槐辽东栎油松,N∶P比值为油松辽东栎刺槐。10—20 cm与0—10 cm土层相比,3树种中除辽东栎中P含量差异不显著外,其它指标N、P含量及N∶P比值均显著下降(P0.05)。刺槐、辽东栎和油松叶片N、P含量与土壤N、P含量均没有显著相关性,以刺槐、辽东栎和油松3种植物叶片为总体来说,P含量与土壤P含量显著正相关(P0.05)。叶片N、P含量均大致表现出随着年均温度和年降水的增加而增加,随着经纬度的增加而降低的趋势,这一点在刺槐叶中最为明显。凋落物N含量随着年均温度和年降水的增加而增加,随着纬度和经度的增加而降低;P含量随着年降水和经度的增加而降低;N∶P比值随着年均温度和年降水的增加而增加,随着纬度的增加而降低。研究区内,土壤N、P含量随着纬度、海拔的增加和年均温度、年降水、经度的降低而增加,N∶P比值则呈相反的趋势。3树种土壤N、P含量及N∶P比值中,P含量比N含量受环境影响更大,且0—10 cm和10—20 cm土层N、P含量及N∶P比值与各环境因子的关系基本一致。     

放牧对全球草地生态系统碳氮磷化学计量特征影响的Meta分析

为明确全球尺度下放牧管理措施对草地生态系统碳(C)、氮(N)、磷(P)化学计量特征的影响,提高草地生态系统管理水平,本研究选取国内外83篇中英文文献进行Meta分析,并通过亚组分析探讨了放牧家畜组合(羊单牧、牛单牧和牛羊混牧)和放牧强度(轻度、中度、重度)对草地生态系统叶片、凋落物、根系,以及土壤C、N、P化学计量特征的影响。结果表明: 放牧会显著降低叶片和凋落物C含量、C/N、C/P,增加N、P含量及N/P;显著降低根系和土壤C、N含量,C/P和N/P,增加P含量和C/N。叶片、凋落物化学计量特征变化对牛、羊单独放牧响应更为明显,而根系、土壤化学计量特征变化则对混牧响应更为明显,重度放牧会对草地生态系统化学计量特征产生更大的影响。放牧会降低土壤N含量,增加P含量,表明放牧对草地N、P含量的影响路径不同。进一步研究N、P含量变化对放牧活动不平衡响应机制,将放牧方式、强度的影响纳入草地生态系统预测、管理模型,能够有效提高草地生态系统管理水平。     

Plasticity in latitudinal patterns of leaf N and P of Oryza rufipogon in China

Characterising the adaptability in nature of plant stoichiometric patterns across geographic or environmental gradients is important in advancing our understanding of the organisation of plant–nutrient relationships. We examined correlations between plant nutrient traits, latitude, longitude, climate and soil variables in 34 populations of Oryza rufipogon across its range. We further compared the responses of population transplants at two experimental gardens: one beyond its northern natural range and another near the southern limit, to assess the nature of geographic variation in plant nutrients. The study showed that leaf P of O. rufipogon in the field was negatively correlated with latitude and largely depended on temperature and soil P availability. Leaf N was not related to latitude but was significantly correlated with precipitation and soil N concentration. Leaf N:P ratio was largely determined by absorption efficiency of P. Transplantation revealed that there were no significant associations of leaf nutrients with geographic, climatic or soil variables of origin in either of the experimental gardens, indicating phenotypic plasticity. However, examination of relationships between response ratios of leaf nutrients and change ratio of climate and soil environments, as well as norms of reaction in the transplantation experiment, revealed more complexity, suggesting both substantial genotypic diversity and the existence of genotype × environment interactions in these populations of O. rufipogon. These data indicate that adaptive plasticity response of plants to temperature and soil P availability significantly explain the observed shifts in leaf N, P and N:P of O. rufipogon along latitudinal gradients.     

Sampling Date,Leaf Age and Root Size: Implications for the Study of Plant C:N:P Stoichiometry

Plant carbon : nitrogen : phosphorus (C:N:P) ratios are powerful indicators of diverse ecological processes. During plant development and growth, plant C:N:P stoichiometry responds to environmental conditions and physiological constraints. However, variations caused by effects of sampling (i.e. sampling date, leaf age and root size) often have been neglected in previous studies. We investigated the relative contributions of sampling date, leaf age, root size and species identity to stoichiometric flexibility in a field mesocosm study and a natural grassland in Inner Mongolia. We found that sampling date, leaf age, root size and species identity all significantly affected C:N:P stoichiometry both in the pot study as well as in the field. Overall, C:N and C:P ratios increased significantly over time and with increasing leaf age and root size, while the dynamics of N:P ratios depended on species identity. Our results suggest that attempts to synthesize C:N:P stoichiometry data across studies that span regional to global scales and include many species need to better account for temporal variation.     

微生境对黄梅秤锤树野生种群叶片功能性状的影响

植物功能性状可以反映植物应对环境变化的适应策略。本文以黄梅秤锤树(Sinojackia huangmeiensis)当前唯一野生种群为对象, 比较了3种微生境(湖边、种群中心、耕地边)中该物种的叶片功能性状均值、种内变异和叶片生态化学计量特征的差异, 分析了黄梅秤锤树对湖岸带微生境变化的响应及其适应策略。结果表明: (1) 3种微生境中土壤C、N、P含量没有显著性差异(P > 0.05), 但土壤C∶N和C∶P具有显著性差异(P < 0.05), 土壤类型和养分条件有所不同。(2)黄梅秤锤树叶片功能性状的比较用单因素方差分析和贝叶斯方差分析得出的结果一致, 均为叶长、叶面积和比叶面积在中心区域显著高于湖边(P < 0.05), 而耕地边与湖边和中心区域均没有显著差异(P > 0.05); 叶N含量在湖边显著高于中心区域和耕地边(P < 0.05), 而中心区域和耕地边间没有显著差异(P > 0.05); 叶宽、叶长/叶宽、叶干物质含量、叶C和叶P含量在3种微生境间都没有显著性差异(P > 0.05)。(3)黄梅秤锤树叶片的N∶P在湖边显著高于中心区域和耕地边(P < 0.05), C∶N在湖边显著小于中心区域和耕地边(P < 0.05), N∶P和C∶N在中心区域和耕地边没有显著性差异(P > 0.05), C∶P在3种微生境间都没有显著性差异(P > 0.05)。(4)黄梅秤锤树叶片功能性状的总体变异程度在0.02-0.28之间, 其中叶片C和N含量在湖边和中心区域的种内变异程度显著较低, 表明3种生境中湖边和中心区域黄梅秤锤树种群的稳定性相对较差。(5)湖边黄梅秤锤树主要通过增加叶N含量促进生长; 中心区域黄梅秤锤树主要通过增加叶面积和比叶面积以及提高叶N的利用效率来提高光捕获能力促进生长; 耕地边黄梅秤锤树的叶N含量和叶面积、比叶面积都处于中等水平, 通过性状之间的共同作用使植株生长达到最佳水平。以上结果表明, 由于微地形、水位波动和土壤环境条件的差异, 黄梅秤锤树对3种生境中的适应策略有所不同, 并且不是通过单一性状调整来适应环境的变化, 而是通过多种性状之间的权衡达到更好的适应效果。