New insights into leaf and fine‐root trait relationships: implications of resource acquisition among 23 xerophytic woody species

Functional traits of leaves and fine root vary broadly among different species, but little is known about how these interspecific variations are coordinated between the two organs. This study aims to determine the interspecific relationships between corresponding leaf and fine‐root traits to better understand plant strategies of resource acquisition. SLA (Specific leaf area), SRL (specific root length), mass‐based N (nitrogen) and P (phosphorus) concentrations of leaves and fine roots, root system, and plant sizes were measured in 23 woody species grown together in a common garden setting. SLA and SRL exhibited a strong negative relationship. There were no significant relationships between corresponding leaf and fine‐root nutrient concentrations. The interspecific variations in plant height and biomass were tightly correlated with root system size characteristics, including root depth and total root length. These results demonstrate a coordinated plant size‐dependent variation between shoots and roots, but for efficiency, plant resource acquisition appears to be uncoupled between the leaves and fine roots. The different patterns of leaf and fine‐root traits suggest different strategies for resource acquisition between the two organs. This provides insights into the linkage between above‐ and belowground subsystems in carbon and nutrient economy.     

羌塘高原降水梯度植物叶片、根系性状变异和生态适应对策

叶片和根系是植物获取资源的最重要的器官,其性状随环境梯度的变化反映了植物光合碳获取和水分与养分的吸收能力及其对环境变化适应的生态对策。羌塘高原降水梯度带高寒草地群落叶片和根系成对性状关系研究不仅能揭示环境梯度对植物性状的塑造作用,也可为理解寒、旱和贫瘠等极端环境下植物的适应策略提供依据。为此,选择3组具有代表性的叶片和根系成对性状:比叶面积(SLA)和比根长(SRL);单位质量叶氮含量(LN_(mass))和单位质量根氮含量(RN_(mass));单位面积叶氮含量(LN_(area))和单位长度根氮含量(RN_(length)),分析不同优势植物地上、地下成对性状变异特征及其与环境因子的关系,探讨植物性状对高寒生态系统水分和养分限制因素的适应策略。研究表明,区域气候和土壤环境导致的叶片性状变异大于根系性状的变异,干旱端的植物既具有高的SRL,又具有高的叶片和根系的养分含量(LN_(mass),LN_(area)和RN_(mass))。SLA-SRL、LN_(mass)-RN_(mass)、LN_(area)-RN_(length)均表现为权衡关系,在干旱端(年降雨量MAP 400 mm)的高寒草原、荒漠草原和极湿润端(MAP 600 mm)的高寒草甸这种权衡关系更为明显,而中间区域(400 MAP 600 mm)的高寒草甸养分和水分限制不是很强烈,叶片和根系性状更多地表现出协同关系。从植物功能类群来看,苔草和禾草类植物叶片和根系成对性状之间具有更强烈的权衡关系。干旱端植物通过增加SRL和叶片、根系养分含量来提高水分和养分的吸收能力,同时通过叶片高的氮含量提高光合碳获取能力,保障了根系生长的物质来源,表现出地上和地下同时投入的策略。干旱端植物保持较高的养分含量是抵御和适应严酷的寒、旱和贫瘠的环境胁迫的重要策略。而在湿润端植物则采取增加SLA,维持地上光合生产力的生态策略。     

Is there coordination of leaf and fine root traits at local scales? A test in temperate forest swamps

Examining the coordination of leaf and fine root traits not only aids a better understanding of plant ecological strategies from a whole‐plant perspective, but also helps improve the prediction of belowground properties from aboveground traits. The relationships between leaf and fine root traits have been extensively explored at global and regional scales, but remain unclear at local scales. Here, we measured six pairs of analogous leaf and fine root traits related to resource economy and organ size for coexisting dominant and subordinate vascular plants at three successional stages of temperate forest swamps in Lingfeng National Nature Reserve in the Greater Hinggan Mountains, NE China. Leaf and fine root traits related to resource acquisition (e.g., specific leaf area [SLA], leaf N, leaf P, root water content, and root P) decreased with succession. Overall, we found strong linear relationships between leaf dry matter content (LDMC) and root water content, and between leaf and root C, N, and P concentrations, but only weak correlations were observed between leaf area and root diameter, and between SLA and specific root length (SRL). The strong relationships between LDMC and root water content and between leaf and root C, N, and P held at the early and late stages, but disappeared at the middle stage. Besides, C and P of leaves were significantly correlated with those of roots for woody plants, while strong linkages existed between LDMC and root water content and between leaf N and root N for herbaceous species. These results provided evidence for the existence of strong coordination between leaf and root traits at the local scale. Meanwhile, the leaf–root trait relationships could be modulated by successional stage and growth form, indicating the complexity of coordination of aboveground and belowground traits at the local scale.     

Plasticity in above‐ and belowground resource acquisition traits in response to single and multiple environmental factors in three tree species

Functional trait plasticity is a major component of plant adjustment to environmental stresses. Here, we explore how multiple local environmental gradients in resources required by plants (light, water, and nutrients) and soil disturbance together influence the direction and amplitude of intraspecific changes in leaf and fine root traits that facilitate capture of these resources. We measured population‐level analogous above‐ and belowground traits related to resource acquisition, i.e. “specific leaf area”–“specific root length” (SLA–SRL), and leaf and root N, P, and dry matter content (DMC), on three dominant understory tree species with contrasting carbon and nutrient economics across 15 plots in a temperate forest influenced by burrowing seabirds. We observed similar responses of the three species to the same single environmental influences, but partially species‐specific responses to combinations of influences. The strength of intraspecific above‐ and belowground trait responses appeared unrelated to species resource acquisition strategy. Finally, most analogous leaf and root traits (SLA vs. SRL, and leaf versus root P and DMC) were controlled by contrasting environmental influences. The decoupled responses of above‐ and belowground traits to these multiple environmental factors together with partially species‐specific adjustments suggest complex responses of plant communities to environmental changes, and potentially contrasting feedbacks of plant traits with ecosystem properties. We demonstrate that despite the growing evidence for broadly consistent resource‐acquisition strategies at the whole plant level among species, plants also show partially decoupled, finely tuned strategies between above‐ and belowground parts at the intraspecific level in response to their environment. This decoupling within species suggests a need for many species‐centred ecological theories on how plants respond to their environments (e.g. competitive/stress‐tolerant/ruderal and response‐effect trait frameworks) to be adapted to account for distinct plant‐environment interactions among distinct individuals of the same species and parts of the same individual.     

Resource economics and coordination among above- and below-ground functional traits of three dominant shrubs from the Chilean coastal desert

Aims Plant functional traits determine how plants respond to environmental factors and influence ecosystem processes. Among them, root traits and analyses of relations between above and below-ground traits in natural communities are scarce. Methods we characterized a set of above- and below-ground traits of three dominant shrub species in a semiarid shrub-steppe that had contrasting leaf phenological habits (deciduous, semideciduous and evergreen). We analysed if there was coordination among above- and below-ground resource economics patterns: i.e. patterns of biomass allocation, construction costs and lifespan.Important findings Above- and below-ground traits and their resource economics relations pointed to species-specific functional strategies to cope with drought and poor soils and to a species ranking of fast to slow whole-plant strategies in terms of resource uptake, biomass construction costs and turnover. The deciduous shrub, Proustia cuneifolia, had relatively deep and even distribution of roots, and high proportion of short-lived tissues of low C construction costs: it had high fine to coarse root and high leaf-to-stem biomass ratios, high specific leaf area (SLA), and stems of low wood density. This strategy allows Proustia to maximize and coordinate above- and below-ground resources uptake as long as the most limiting factor (water) is available, but at the cost of having relative high plant biomass turnover. The evergreen Porlieria chilensis, instead, displayed a more conservative and slow strategy in terms of resource economics. It had ~80% of the roots in the 40cm topsoil profile, low proportion of fine compared with coarse roots and low leaf-to-stem ratios, low SLA and stems of high wood density, i.e. it invested in C costly tissues that, overall, persist longer but probably at the cost of having lower plant resource uptake rates. Traits in the semideciduous Adesmia bedwellii were in between these two functional extremes. Our results revealed high functional diversity and above- and below-ground complementarity in resource economics among these three codominant species in the Chilean coastal desert.     

Complex trait relationships between leaves and absorptive roots: Coordination in tissue N concentration but divergence in morphology

Leaves and absorptive roots (i.e., first‐order root) are above‐ and belowground plant organs related to resource acquisition; however, it is controversy over whether these two sets of functional traits vary in a coordinated manner. Here, we examined the relationships between analogous above‐ and belowground traits, including chemical (tissue C and N concentrations) and morphological traits (thickness and diameter, specific leaf area and root length, and tissue density) of 154 species sampling from eight subtropical and temperate forests. Our results showed that N concentrations of leaves and absorptive roots were positively correlated independent of phylogeny and plant growth forms, whereas morphological traits between above‐ and belowground organs varied independently. These results indicate that, different from plant economics spectrum theory, there is a complex integration of diverse adaptive strategies of plant species to above‐ and belowground environments, with convergent adaptation in nutrient traits but divergence in morphological traits across plant organs. Our results offer a new perspective for understanding the resource capture strategies of plants in adaptation to heterogeneous environments, and stress the importance of phylogenetic consideration in the discussion of cross‐species trait relationships.     

岷江上游4个栽培树种细根功能性状垂直分布的差异性

细根(直径≤2 mm)功能性状及垂直分布格局是反映植物对土壤资源吸收策略和影响森林地下生态过程的关键。本研究以岷江上游4个人工林树种连香树(Cercidiphyllum japonicum)、白桦(Betula platyphylla)、华山松(Pinus armandii)和油松(P.tabuliformis)为对象,调查不同海拔树木细根功能性状及其在不同土层间的垂直分布格局,并分析细根功能性状分布与构型之间的相关关系。结果表明:阔叶树种比针叶树种有更大的根长密度、生物量、比根长和比表面积,而直径反之;4个树种细根集中在0~20 cm土层,根长密度和生物量在较高海拔地段均显著大于较低海拔,且均随土壤深度增加而减少,但比根长、比表面积和直径无显著的海拔差异,随土层加深也无明显的垂直变化规律;针阔树种间的细根构型差异显著,但不受海拔差异的影响,阔叶树的细根分支强度与一级根数量显著大于针叶树种;一级根数和根尖密度与比根长以及分根比与根长密度和生物量均呈显著正相关,而分叉与几个细根功能参数均呈负相关;随着土层深度增加,细根总生长量明显减少,但细根资源利用效率和策略不变;5个细根功能性状的垂直分布格局差异明显,且受树种特性影响显著,细根分支构型对其垂直分布及资源获取策略具有显著影响。     

黄土高原白羊草、沙棘和辽东栎细根比根长特性

以黄土高原地区典型草本（白羊草）、灌木（沙棘）和乔木（辽东栎）为对象,研究了3种植物细根比根长在不同土层的分布状况以及与其它细根参数和土壤物理因子之间的相关性。结果表明,3种植物细根比根长的变化范围为6～55ram／rag。在0,80cm土层,白羊草、沙棘和辽东栎细根比根长变化范围分别为18—55mm／mg,14—4JDmm／mg,6—33mm／mg。3种植物0--80cm土层平均细根比根长从大到小依次为白羊草〉沙棘〉辽东栎。3种植物0-10cm土层细根比根长依次为沙棘〉辽东栎〉白羊草,10-80cm依次为白羊草〉辽东栎〉沙棘,表明3种植物细根比根长不仅在这两土层中的分布不具一致性,而且与0-80cm土层平均比根长也不具有一致性,进一步说明3种植物沿土壤剖面的生物量分配策略不同。相关分析表明,3种植物细根比根长与其它细根参数之间的相互关系各不相同,制约程度存在差异。与土壤物理因子的相关分析表明,3种植物细根比根长均随土壤含水量的增加而减少。土壤各级水稳性团聚体和土壤颗粒对3种植物细根比根长并无一致的影响。     

武夷山不同海拔毛竹细根功能性状

细根作为植物最重要的资源获取功能器官,是影响陆地生态系统的重要组成部分。定量化毛竹的细根功能性状对于理解其生理生态特征响应及生活史策略至关重要。为揭示毛竹细根功能性状随海拔梯度的变化规律以及细根的适应策略,对武夷山不同海拔(840 m、1040 m、1240 m)毛竹细根的碳(C)、氮(N)、磷(P)含量和比根长(SRL)、比根面积(SRA)等性状进行测定,分析细根性状在海拔上的差异及其异速生长关系。结果表明：(1)不同海拔毛竹细根养分性状存在显著差异。毛竹细根C含量在海拔1040 m最大。随海拔升高,细根N、P含量均呈下降趋势,细根C∶N、C∶P随着海拔的升高而增加。(2)细根的结构性状在海拔梯度上差异显著。随海拔升高,细根平均根直径(AvgDiam)、SRL及SRA均呈下降趋势,而根组织密度(RTD)呈升高趋势。(3)细根性状间存在显著的异速生长关系。细根N与P含量存在显著的等速生长关系,二者与C含量存在显著异速生长关系;SRL与SRA存在显著的等速生长关系,二者与RTD存在显著的负等速生长关系,与N含量存在显著的异速生长关系;细根AvgDiam与RTD存在显著的负异速生长关系。毛...     

Do Clonal and Bud Bank Traits Vary in Correspondence with Soil Properties and Resource Acquisition Strategies? Patterns in Alpine Communities in the Scandian Mountains

Plant traits associated with resource acquisition strategies (specific leaf area (SLA), leaf dry matter content (LDMC), leaf size and plant height) change along gradients of soil properties, being the most conservative in a resource-poor environment and the most dynamic in a resource-rich environment. Clonal attributes also vary along soil and other environmental conditions. We hypothesized that in alpine communities in the Scandian Mts. (1) the average composition of traits in a plant assemblage in terms of i) the predominance of different clonal growth organ types, ii) the number of buds in the bud bank, iii) the distribution of the bud-bank (above- and below ground), iv) the distance of lateral spread and v) the longevity of plant – offspring connections would change along a gradient of soil properties and (2) that this variation would be in correspondence with that of traits associated with resource acquisition strategies (SLA, LDMC, leaf size and plant height). Analysis of clonal and bud bank traits for species of alpine communities supported our first hypothesis: with decreasing soil quality the most common clonal growth organs were rhizomes, and there was a predominance of perennial bud banks located at the soil surface or below-ground, low rates of lateral spread and long persistence of plant – offspring connections. Our second hypothesis was partly supported. As predicted, at the level of the plant assemblage, these clonal and bud bank traits were positively associated with LDMC, and negatively with leaf size and plant height. These observations reinforce the hypotheses about trade-offs between acquisition and retention strategies in plants. The only result that was in contradiction with our expectations was the lack of correspondence between clonal and bud bank traits and SLA that could be attributed to errors associated to the measurement of the area of narrow and small leaves or to the dependence of the SLA index on species-specific morphological attributes.     

Consequences of phenotypic plasticity vs. interspecific differences in leaf and root traits for acquisition of aboveground and belowground resources

Trade-offs between acquisition capacities for aboveground and belowground resources were investigated by studying the phenotypic plasticity of leaf and root traits in response to different irradiance levels at low nutrient supply. Two congeneric grasses with contrasting light requirements, Dactylis glomerata and D. polygama, were used. The aim was to analyze phenotypic covariation in components of leaf area and root length in response to above- and belowground resource limitation and the consequences of this variation for resource acquisition and plant growth. At intermediate shading (30 and 20% of full sunlight) the plants were able to maintain their total root length, despite a strongly increased total leaf area and a reduced biomass allocation to roots. This was associated with an unaltered or slightly increased nutrient uptake and growth. At 5.5% relative irradiance, growth was severely reduced, especially in the shade-tolerant D. polygama. The results show that constraints on acquisition capacities for aboveground and belowground resources, caused by biomass allocation, may be alleviated by plasticity in other traits such as tissue-mass density and thickness of roots and leaves. The results also suggest different adaptive constraints for phenotypic plasticity and for genetically determined interspecific variation. Phenotypic plasticity tends to maximize resource acquisition and growth rate in the short term, whereas the higher tissue-mass density and the longer leaf life-span of shade-tolerant species indicate reduced loss rates as a more advantageous species-specific adaptation to shade in the long term.     

Independent evolution of leaf and root traits within and among temperate grassland plant communities

In this study, we used data from temperate grassland plant communities in Alberta, Canada to test two longstanding hypotheses in ecology: 1) that there has been correlated evolution of the leaves and roots of plants due to selection for an integrated whole-plant resource uptake strategy, and 2) that trait diversity in ecological communities is generated by adaptations to the conditions in different habitats. We tested the first hypothesis using phylogenetic comparative methods to test for evidence of correlated evolution of suites of leaf and root functional traits in these grasslands. There were consistent evolutionary correlations among traits related to plant resource uptake strategies within leaf tissues, and within root tissues. In contrast, there were inconsistent correlations between the traits of leaves and the traits of roots, suggesting different evolutionary pressures on the above and belowground components of plant morphology. To test the second hypothesis, we evaluated the relative importance of two components of trait diversity: within-community variation (species trait values relative to co-occurring species; α traits) and among-community variation (the average trait value in communities where species occur; β traits). Trait diversity was mostly explained by variation among co-occurring species, not among-communities. Additionally, there was a phylogenetic signal in the within-community trait values of species relative to co-occurring taxa, but not in their habitat associations or among-community trait variation. These results suggest that sorting of pre-existing trait variation into local communities can explain the leaf and root trait diversity in these grasslands.     

Effects of water supply on root traits and biological yield of Durum (Triticum durum Desf.) and Khorasan (Triticum turanicum Jakubz) wheat

The ability of a plant to change its root characteristics to increase the acquisition of soil water is an important adaptation mechanism to water limitation. In this regard, a field study was carried out in the Pannonian region of eastern Austria with two tetraploid wheat genotypes, i.e. Durum (Triticum durum Desf.) and Khorasan (Triticum turanicum Jakubz), during a comparatively wetter and drier year, i.e. 2008 and 2009, respectively. The genotypes showed significant differences in average root diameter and fine root length. All root traits varied with soil depth. The highest root length density and root biomass were observed with Khorasan wheat in 0–10 cm soil depth. Durum wheat showed a stronger response in fine roots to water availability and produced more fine roots in the moist year. Electric root capacitance was higher with Khorasan wheat. Durum showed higher biological yield stability across years with different precipitation with respect to above- and belowground biomass. It produced more leaf area under humid conditions. Khorasan allocated more assimilates to belowground organs in dry conditions, but without positive effect on aboveground biomass.     

杨树人工林细根数量和形态特征的季节动态及代际差异

采集欧美杨107Ⅰ代和Ⅱ代人工林细根样品,分析杨树不同根序细根数量特征(根长度、表面积和生物量)和形态特征(比根长、根长密度、根组织密度)对季节波动的响应及其代际差异.结果表明： 杨树各根序细根数量特征(根长度、表面积和生物量)均呈明显的季节变化,且具有明显的根序差异性.低级根序细根数量特征季节差异显著,细根生物量在生长季显著增加而生长季后显著下降.高级根序细根比根长季节波动显著,而根长密度和根组织密度等形态特征波动较小.连作导致人工林杨树1～2级细根长度、生物量、比根长和根长密度在生长季显著增大.1级细根数量特征与土壤温湿度呈显著正相关,与土壤有机质和速效氮含量呈显著负相关;而2级细根数量特征仅与土壤养分显著相关.杨树人工林细根特征的季节动态及代际差异体现了杨树对细根的碳投入变化,因连作引发的土壤养分匮乏可能引发植株对根系的碳投入增加,这种碳分配格局与人工林地上部分生产力形成密切相关.     

Decoupled drought responses of fine-root versus leaf acquisitive traits among six Prunus hybrids

要预测干旱对森林和果树种植的影响，就需要更好地了解干旱胁迫对叶片和细根的资源获取性状(比叶面积SLA、比根面积SRA以及比根长SRL)的影响。本研究试图验证以下科学假设：在重度干旱胁迫下，叶片与细根的资源获取性状具有协同效应，使得植物能够采取整合的资源节约策略。我们收集了不同干旱敏感性的六种李属砧木的幼树，通过在温室中对它们进行干旱试验来验证我们的科学假设。这些幼树被分为两组进行水分处理试验，即对照处理组(浇水量为100%田间持水量)与重度干旱处理组(每种砧木的浇水量为该砧木对照组植物每日蒸散量的33%)。在处理开始后的第30天和第60天，分别对两组处理下的六种砧木的植物叶片与细根进行取样。结果表明，在重度干旱胁迫下，没有任何一种植物同时显著降低了SLA和SRA(或SRL)。六种李属砧木植物的细根性状表现出两种主要的干旱响应组合：(1)根组织密度(RTD)增大，同时平均根径减小，而SRL没有显著变化；(2) RTD增大，同时SRL减小，而平均根径没有显著变化。六种砧木植物性状的干旱响应展现出两个相互垂直的变化梯度，这两个梯度均以从对照处理组到干旱处理组植物的资源节约性变化为特征，其中一个梯度展现了叶片气体交换，SRA，SRL以及RTD的干旱响应之间的密切相关关系，而另一个梯度以SLA的降低为特征。这些发现突出了(1)根系性状干旱响应的多维性；(2)重度干旱胁迫下，叶片经济性状与叶片水力性状之间的解耦联关系；(3)重度干旱胁迫下，叶片水力性状与根系水力性状之间的协同变化关系。这项研究有助于在种内尺度上确认根系干旱响应多维性的起源，并重点突出了不同植物如何通过不同的叶片与细根性状的干旱响应组合而得以在重度干旱胁迫下存活。     

Aridity increases below-ground niche breadth in grass communities

Aridity is an important environmental filter in the assembly of plant communities worldwide. The extent to which root traits mediate responses to aridity, and how they are coordinated with leaf traits, remains unclear. Here, we measured variation in root tissue density (RTD), specific root length (SRL), specific leaf area (SLA), and seed size within and among thirty perennial grass communities distributed along an aridity gradient spanning 190–540 mm of climatic water deficit (potential minus actual evapotranspiration). We tested the hypotheses that traits exhibited coordinated variation (1) among species, as well as (2) among communities varying in aridity, and (3) functional diversity within communities declines with increasing aridity, consistent with the “stress-dominance” hypothesis. Across communities, SLA and RTD exhibited a coordinated response to aridity, shifting toward more conservative (lower SLA, higher RTD) functional strategies with increasing aridity. The response of SRL to aridity was more idiosyncratic and was independent of variation in SLA and RTD. Contrary to the stress-dominance hypothesis, the diversity of SRL values within communities increased with aridity, while none of the other traits exhibited significant diversity responses. These results are consistent with other studies that have found SRL to be independent of an SLA–RTD axis of functional variation and suggest that the dynamic nature of soil moisture in arid environments may facilitate a wider array of resource capture strategies associated with variation in SRL.     

Fine root decomposition rates do not mirror those of leaf litter among temperate tree species

Elucidating the function of and patterns among plant traits above ground has been a major research focus, while the patterns and functioning of belowground traits remain less well understood. Even less well known is whether species differences in leaf traits and their associated biogeochemical effects are mirrored by differences in root traits and their effects. We studied fine root decomposition and N dynamics in a common garden study of 11 temperate European and North American tree species (Abies alba, Acer platanoides, Acer pseudoplatanus, Carpinus betulus, Fagus sylvatica, Larix decidua, Picea abies, Pseudotsuga menziesii, Quercus robur, Quercus rubra and Tilia cordata) to determine whether leaf litter and fine root decomposition rates are correlated across species as well as which species traits influence microbial decomposition above versus below ground. Decomposition and N immobilization rates of fine roots were unrelated to those of leaf litter across species. The lack of correspondence of above- and belowground processes arose partly because the tissue traits that influenced decomposition and detritus N dynamics different for roots versus leaves, and partly because influential traits were unrelated between roots and leaves across species. For example, while high hemicellulose concentrations and thinner roots were associated with more rapid decomposition below ground, low lignin and high Ca concentrations were associated with rapid aboveground leaf decomposition. Our study suggests that among these temperate trees, species effects on C and N dynamics in decomposing fine roots and leaf litter may not reinforce each other. Thus, species differences in rates of microbially mediated decomposition may not be as large as they would be if above- and belowground processes were working in similar directions (i.e., if faster decomposition above ground corresponded to faster decomposition below ground). Our results imply that studies that focus solely on aboveground traits may obscure some of the important mechanisms by which plant species influence ecosystem processes.     

环境及遗传背景对延河流域植物叶片和细根功能性状变异的影响

研究环境筛选作用和植物系统发育背景对植物群落构建产生的影响,有助于理解植物在生长过程中对资源的分配利用和对环境的适应规律。以延河流域3个植被带(森林带、森林草原带及典型草原带)稳定的自然植物群落为研究对象,调查了31个样地107种植物,隶属于35个科78个属,测量了6种叶片和3种细根性状。分别对3个植被带和不同植物科植物的叶片和细根性状做单因素方差分析,结果表明:叶片氮含量和细根氮含量在3个植被带间无显著差异,叶厚度、比叶面积、叶组织密度、叶片磷含量、叶片氮磷比、比根长、根组织密度在3个植被带间差异极显著。由南向北随着气候干旱的加剧,植物通过调节叶片和细根性状,表现出了不同的适应策略:森林带植物叶片相对生长速率高,根系防御力强;森林草原带植物叶片防御力强,根系相对生长速率快。不同科的植物在相同的环境条件下,对于资源的竞争力和胁迫的忍耐力也有所不同,比如豆科植物具有远远高于其他科的叶片和细根氮含量,但是对养分的利用效率并不高。GLM分析结果说明,所涉及的植物功能性状的空间变异主要来自于年均降雨量的变化及植物科的差异,如16.26%的比叶面积的变异可由年均降雨量变化解释,4.02%可由植物科的差异解释。物种水平上,叶厚度、比叶面积、叶组织密度、比根长、根组织密度、叶片磷含量是对气候干燥度变化响应敏感的植物功能性状,其空间变异主要由环境差异所致。延河流域的植物群落在形成过程中,存在明显的环境筛选效应。这表明,环境异质性在植被恢复实践中必须予以考虑。     

增温、施肥与种内竞争的交互作用对云杉根系属性的影响

增温、施肥与种内竞争的交互作用对云杉根系属性的影响 物种竞争、气温和土壤养分是青藏高原东部高寒地区影响树木生长的重要因素。虽然已开展了大量关于物种竞争、气温、施肥单因素对树木生长的影响研究,但关于这三者的交互作用对根系生长的影响还知之甚少。因此,本研究拟通过测量根系属性(细根长、根表面积、比根长、比表面积、根尖数、根系分支数等)、根生物量,以及根系养分吸收,研究施肥和增温对物种竞争的影响,并进一步探讨施肥、增温与物种竞争的交互作用对云杉(Picea asperata)生长的影响机制以及所采取的适应策略。研究结果表明,增温、施肥和竞争均提高了细根的氮、钾浓度,但并未影响细根生物量和根长、根表面积、根尖数和根分支数等根系特征。然而,无论是增温、施肥,或是它们的联合作用,与物种竞争进行交互时,均增加了根长、根表面积、根尖数、根系分支数和养分吸收。此外,施肥降低了根比表面积、比根长和单位面积的根尖数和根分支数,增温和竞争的交互作用使根比表面积、比根长下降,其他参数不受温度和竞争的影响。该结果表明,云杉在物种竞争、气候变暖、施肥及其交互作用下保持着保守的营养策略。该研究加强了对树木应对全球变化的生理和生态适应性的理解。     

Salt effects on functional traits in model and in economically important Lotus species

A common stress on plants is NaCl‐derived soil salinity. Genus Lotus comprises model and economically important species, which have been studied regarding physiological responses to salinity. Leaf area ratio (LAR), root length ratio (RLR) and their components, specific leaf area (SLA) and leaf mass fraction (LMF) and specific root length (SRL) and root mass fraction (RMF) might be affected by high soil salinity. We characterised L. tenuis, L. corniculatus, L. filicaulis, L. creticus, L. burtii and L. japonicus grown under different salt concentrations (0, 50, 100 and 150 mm NaCl) on the basis of SLA, LMF, SRL and RMF using PCA. We also assessed effects of different salt concentrations on LAR and RLR in each species, and explored whether changes in these traits provide fitness benefit. Salinity (150 mm NaCl) increased LAR in L. burtii and L. corniculatus, but not in the remaining species. The highest salt concentration caused a decrease of RLR in L. japonicus Gifu, but not in the remaining species. Changes in LAR and RLR would not be adaptive, according to adaptiveness analysis, with the exception of SLA changes in L. corniculatus. PCA revealed that under favourable conditions plants optimise surfaces for light and nutrient acquisition (SLA and SRL), whereas at higher salt concentrations they favour carbon allocation to leaves and roots (LMF and RMF) in detriment to their surfaces. PCA also showed that L. creticus subjected to saline treatment was distinguished from the remaining Lotus species. We suggest that augmented carbon partitioning to leaves and roots could constitute a salt‐alleviating mechanism through toxic ion dilution.