Linking leaf and root trait syndromes among 39 grassland and savannah species

Here, we tested hypothesized relationships among leaf and fine root traits of grass, forb, legume, and woody plant species of a savannah community. CO2 exchange rates, structural traits, chemistry, and longevity were measured in tissues of 39 species grown in long-term monocultures. Across species, respiration rates of leaves and fine roots exhibited a common regression relationship with tissue nitrogen (N) concentration, although legumes had lower rates at comparable N concentrations. Respiration rates and N concentration declined with increasing longevity of leaves and roots. Species rankings of leaf and fine-root N and longevity were correlated, but not specific leaf area and specific root length. The C3 and C4 grasses had lower N concentrations than forbs and legumes, but higher photosynthesis rates across a similar range of leaf N. Despite contrasting photosynthetic pathways and N2-fixing ability among these species, concordance in above- and below-ground traits was evident in comparable rankings in leaf and root longevity, N and respiration rates, which is evidence of a common leaf and root trait syndrome linking traits to effects on plant and ecosystem processes.     

Changes in individual plant traits and biomass allocation in alpine meadow with elevation variation on the Qinghai-Tibetan Plateau

Plant traits and individual plant biomass allocation of 57 perennial herbaceous species, belonging to three common functional groups (forbs, grasses and sedges) at subalpine (3700 m ASL), alpine (4300 m ASL) and subnival (⩾5000 m ASL) sites were examined to test the hypothesis that at high altitudes, plants reduce the proportion of aboveground parts and allocate more biomass to belowground parts, especially storage organs, as altitude increases, so as to geminate and resist environmental stress. However, results indicate that some divergence in biomass allocation exists among organs. With increasing altitude, the mean fractions of total biomass allocated to aboveground parts decreased. The mean fractions of total biomass allocation to storage organs at the subalpine site (7%±2% S.E.) were distinct from those at the alpine (23%±6%) and subnival (21%±6%) sites, while the proportions of green leaves at all altitudes remained almost constant. At 4300 m and 5000 m, the mean fractions of flower stems decreased by 45% and 41%, respectively, while fine roots increased by 86% and 102%, respectively. Specific leaf areas and leaf areas of forbs and grasses deceased with rising elevation, while sedges showed opposite trends. For all three functional groups, leaf area ratio and leaf area root mass ratio decreased, while fine root biomass increased at higher altitudes. Biomass allocation patterns of alpine plants were characterized by a reduction in aboveground reproductive organs and enlargement of fine roots, while the proportion of leaves remained stable. It was beneficial for high altitude plants to compensate carbon gain and nutrient uptake under low temperature and limited nutrients by stabilizing biomass investment to photosynthetic structures and increasing the absorption surface area of fine roots. In contrast to forbs and grasses that had high mycorrhizal infection, sedges had higher single leaf area and more root fraction, especially fine roots.     

Alpine climate alters the relationships between leaf and root morphological traits but not chemical traits

Leaves and fine roots are among the most important and dynamic components of terrestrial ecosystems. To what extent plants synchronize their resource capture strategies above- and belowground remains uncertain. Existing results of trait relationships between leaf and root showed great inconsistency, which may be partly due to the differences in abiotic environmental conditions such as climate and soil. Moreover, there is currently little evidence on whether and how the stringent environments of high-altitude alpine ecosystems alter the coordination between above- and belowground. Here we measured six sets of analogous traits for both leaves and fine roots of 139 species collected from Tibetan alpine grassland and Mongolian temperate grassland. N, P and N:P ratio of leaves and fine roots were positively correlated, independent of biogeographic regions, phylogenetic affiliation or climate. In contrast, leaves and fine roots seem to regulate morphological traits more independently. The specific leaf area (SLA)–specific root length (SRL) correlation shifted from negative at sites under low temperature to positive at warmer sites. The cold climate of alpine regions may impose different constraints on shoots and roots, selecting simultaneously for high SLA leaves for rapid C assimilation during the short growing season, but low SRL roots with high physical robustness to withstand soil freezing. In addition, there might be more community heterogeneity in cold soils, resulting in multidirectional strategies of root in resource acquisition. Thus our results demonstrated that alpine climate alters the relationships between leaf and root morphological but not chemical traits.     

Variation in structural and physiological leaf traits of eight species in karst desertification area of China

Leaf traits have long been recognized as influential factors in the acquisition and processing of resources by plants. However, there is less knowledge of between-species variations in seasonal changes in leaf traits and trait interrelationships. Therefore, we examined variations in leaf area (LA), dry biomass (DM), specific leaf area (SLA), and leaf gas-exchange parameters in one non-native and seven native tree species under field environmental conditions, in a karst area in China subjected to desertification. Measurements were taken three times during the growing season. The results show that the seven native trees had higher LA, DM, and water-use efficiency (WUE) than the non-native Cinnamomum camphora. In contrast, all the native tree species except Ligustrum lucidum had lower photosynthetic rates (P _N) than the non-native species. In all species, the relationship between LA and DM was less variable than the relationship between SLA and LA. However, leaves of the non-native C. camphora and native species Sterculia lanceolata, Cleidiocarpon cavalerei and Cyclobalanopsis glauca were highly sensitive to seasonal conditions, leaves of Sapindus mukorossi and Ligustrum lucidum were less sensitive to seasonal changes, and leaves of Syzygium cumini and Cephalomappa sinensis were insensitive. An understanding of leaf traits will aid the selection of suitable species for land restoration.     

Traits of an invasive grass conferring an early growth advantage over native grasses

Aims Invasive species often have higher relative growth rates (RGR) than their native counterparts. Nutrient use efficiency, total leaf area and specific leaf area (SLA) are traits that may confer RGR differences between natives and invasives, but trait differences are less prominent when the invasive species belongs to the same plant functional type as the dominant native species. Here, we test if traits displayed soon after germination confer an early size advantage. Specifically, we predicted that invasive species seedlings grow faster than the natives because they lack trade-offs that more strongly constrain the growth of native species.Methods We quantified plant morphological and physiological traits and RGR during early seedling growth at high and low nutrient levels in three dominant perennial native C₄ grasses: Panicum virgatum L. (switchgrass), Schizachyrium scoparium (Michx.) Nash (little bluestem) and Andropogon gerardii Vitman (big bluestem); and a perennial C₄ exotic invasive grass, Sorghum halepense (L.) Pers. (Johnsongrass).Important findings After 2 weeks of growth, Johnsongrass seedlings had greater biomass, SLA and photosynthetic nitrogen use efficiency, but lower leaf N concentrations (% leaf N) and root:shoot ratio than natives. As growth continued, Johnsongrass more quickly produced larger and thicker leaves than the natives, which dampened the growth advantage past the first 2 to 3 weeks of growth. Investment in carbon gain appears to be the best explanation for the early growth advantage of Johnsongrass. In natives, growth was constrained by an apparent trade-off between allocation to root biomass, which reduced SLA, and production of leaves with high N content, which increased carbon gain. In Johnsongrass, root:shoot ratio did not interact with other traits, and % leaf N was decoupled from RGR as a result of a trade-off between the positive indirect association of % leaf N with RGR and the negative direct association of % leaf N with RGR.     

Leaf life spans in wild perennial herbaceous plants: a survey and attempts at a functional interpretation

Summary Leaf longevity in 29 herbaceous plant species of Central Europe was studied by inspecting tagged leaves at weekly intervals. About half of the species are elements of the lowland meadow flora, the other half comprises a representative sample of species from the highest sites where vascular plants grow in the Alps. Shaded and water-stressed sites were avoided. Overall mean leaf longevity did not differ significantly between sites and amounted to 71±5 days at low and 68±4 days at high altitude. Leaf life spans ranged (with no clear altitudinal trend) from 41 to 95 days. Low-altitude forbs and grasses produced several leaf cohorts during their growth period, while most alpine species produced only one. Correlations were found between leaf duration and percent nitrogen content and carbon-cost/carbon-gain ratios, but not with leaf dry mass per unit leaf area and photosynthetic capacity alone. As leaf life spans increase, more C tends to be invested per unit CO₂ uptake and less N is invested per unit invested C. Thus, mass relationships rather than area relationships seem to be linked to leaf life span in these species, suggesting that leaf duration is associated with properties other than the efficiency of light utilization (e.g. mechanical strength, herbivory or pathogen resistance). It seems that the explanations of leaf duration that have been developed for evergreen/deciduous plants and for plants along steep light gradients do not apply to the variable life spans in leaves of perennial herbaceous plants of open habitats.     

Similar responses in morphology,growth, biomass allocation,and photosynthesis in invasive <Emphasis Type="Italic">Wedelia trilobata</Emphasis> and native congeners to CO<Subscript>2</Subscript> enrichment

Both global change and biological invasions threaten biodiversity worldwide. However, their interactions and related mechanisms are still not well elucidated. To elucidate potential traits contributing to invasiveness and whether ongoing increase in CO₂ aggravates invasions, noxious invasive Wedelia trilobata and native Wedelia urticifolia and Wedelia chinensis were compared under ambient and doubled atmospheric CO₂ concentrations in terms of growth, biomass allocation, morphology, and physiology. The invader had consistently higher leaf mass fraction (LMF) and specific leaf area than the natives, contributing to a higher leaf area ratio, and therefore to faster growth and invasiveness. The higher LMF of the invader was due to lower root mass fraction and higher fine root percent. On the other hand, the invader allocated a higher fraction of leaf nitrogen (N) to photosynthetic apparatus, which was associated with its higher photosynthetic rate, and resource use efficiency. All these traits collectively contributed to its invasiveness. CO₂ enrichment increased growth of all studied species by increasing actual photosynthesis, although it decreased photosynthetic capacities due to decreased leaf and photosynthetic N contents. Responses of the invasive and native plants to elevated CO₂ were not significantly different, indicating that the ongoing increase in CO₂ may not aggravate biological invasions, inconsistent with the prevailing results in references. Therefore, more comparative studies of related invasive and native plants are needed to elucidate whether CO₂ enrichment facilitates invasions.     

Response of purely symbiotic and NO3-fed nodulated plants of Lupinus luteus and Vicia atropurpurea to ultraviolet-B radiation

The effects of elevated UV-B radiation on growth, symbiotic function and concentration of metabolites were assessed in purely symbiotic and NO3-fed nodulated plants of Lupinus luteus and Vicia atropurpurea grown outdoors either on tables under supplemental UV-B radiation or in chambers covered with different types of plexi-glass to attenuate solar ultraviolet radiation. Moderately and highly elevated UV-B exposures simulating 15% and 25% ozone depletion as well as sub- ambient UV-B did not alter organ growth, plant total dry matter and N content per plant in both L. luteus and V. atropurpurea. In contrast, elevated UV-B increased (P <0.05) flavonoid and anthocyanin concentrations in roots and leaves of L. luteus, but not of V. atropurpurea. Feeding nodulated plants of L. luteus under elevated UV-B radiation with 2 mM NO3 increased (P <0.05) nodule, leaf and total dry matter, and whole plant N content. With V. atropurpurea, NO3 reduced (P <0.05) nodule activity, root %N and concentrations of flavonoids, anthocyanins in roots and leaves and soluble sugars in roots, in contrast to an observed increase (P <0.05) in nodule dry matter per plant. Similarly, supplying 2 mM NO3 to L. luteus plants exposed to sub-ambient UV-B radiation significantly reduced individual organ growth, plant total biomass, nodule dry matter, nodule %N, and whole plant N content, as well as root concentrations of flavonoids, anthocyanins, soluble sugars, and starch of L. luteus, but not V. atropurpurea plants. These results show no adverse effect of elevated UV-B radiation on growth and symbiotic function of L. luteus and V. atropurpurea plants. However, NO3 supply promoted growth in L. luteus plants exposed to the highly elevated UV-B radiation.     

Dorsoventral asymmetry of photosynthesis and photoinhibition in flag leaves of two rice cultivars that differ in nitrogen response and leaf angle

Rice is believed to show photosynthetic symmetry between adaxial and abaxial leaf sides. To verify this, we re‐examined dorsoventral asymmetry in photosynthesis, chlorophyll fluorescence and anatomical traits in flag leaves of two Oryza sativa cultivars that differ in nitrogen (N) response and in leaf angle: ‘Akenohoshi’, a cultivar that can adapt to low‐N (LN), with low leaf angle (more erect leaves), and ‘Shirobeniya’, a cultivar that is unable to adapt to LN, with higher leaf angle. Plants were grown under standard‐N (SN) and LN conditions. LN leaves of both cultivars became more erect than SN, but LN Akenohoshi still had more erect ones than Shirobeniya. Contrary to results of previous studies, leaves of both cultivars showed an asymmetry in photosynthetic rate between adaxial and abaxial sides (higher on the adaxial side) under SN. SN leaves of both cultivars showed lower susceptibility to photoinhibition on the adaxial side than on the abaxial side. However, leaves of Akenohoshi showed less asymmetry in these traits under LN than under SN, whereas leaves of Shirobeniya had similar degrees of asymmetry in these traits under both SN and LN. Both cultivars also showed dorsoventral asymmetry in anatomical traits of mesophyll tissue regardless of N level, but the degree of asymmetry was lower in LN Akenohoshi. These data reveal that rice leaves exhibit dorsoventral asymmetry in photosynthetic and anatomical features, and that the degree of asymmetry varies with cultivar and N level. It is suggested that lower leaf angles (particularly in Akenohoshi) in the presence of LN represent a light acclimation to prevent photoinhibition.     

The nutritional status of plants from high altitudes

Summary Are plants at high altitudes short in nutrients? In order to answer this question the mineral nutrient content of leaves from over 150 plant species from 9 different mountain areas of all major climatic zones were analyzed (Kjeldahl nitrogen in all, phosphate in half of the samples, K, Mg, Mn, Ca in the Alps only). The majority of data are from herbaceous perennials, but shrubs and trees were studied as well. N-partitioning was studied in 45 herbaceous species from contrasting altitudes in the Alps. The survey falls into three categories: (1) comparisons of whole communities of species from contrasting altitudes, (2) analysis of altitudinal gradients, and (3) additional collections from high altitude sites alone. Unlike the other mineral nutrients, nitrogen content follows consistent altitudinal and latitudinal trends. The higher altitude sample always had higher N content per unit leaf area, irrespective of life form, wherever comparable plants (the same or related species) were investigated at contrasting altitudes. N content per unit dry weight (%) increased with altitude in herbaceous plants (in some species >4%), but was remarkably stable in evergreen woody plants (around 1%). The mean fraction of total plant N allocated to leaves of herbaceous plants in the Alps was the same at low and high altitude (1/3 of total). Leaf N (%) from the regional upper limits of higher plant life reveals a latitudinal decrease from subarctic to equatorial mountains, which may be related to the duration of annual leaf activity. Since mean N content per leaf area hardly differs between the uppermost sites, life span expectation (sink-duration) seems to control carbon investments rather than N input per leaf area. The growth of leaves at high altitude seems to be controlled in a way that leads to comparatively high nutrient contents, which in turn support high metabolic activity. Inherent developmental growth constraints inhibit nutrient dilution in the plant body and thus defy the application of classical concepts of plant-nutrient versus soil-nutrient relations developed for lowlands and in particular for cultivated plants. The results re-emphasize the global significance of links between nitrogen content, leaf sclerophylly, leaf longevity and photosynthetic capacity.Dedicated to Prof. Walter Larcher on the occasion of his 60th birthday, with thanks for leading me to comparative plant ecology     

Early stages of root and leaf decomposition in Hawaiian forests: effects of nutrient availability

We examined the effects of soil nutrient availability and tissue chemistry on decomposition of both fine roots (<2 mm diameter) and leaves in three sites along a forest chronosequence in the Hawaiian Islands. These sites form a natural fertility gradient, with the youngest and oldest sites having lower nutrient availability than the intermediate-aged site. Nitrogen (N) limits aboveground net primary productivity (ANPP) in the youngest site, while phosphorus (P) limits ANPP in the oldest site. Both root and leaf litter decomposed most slowly in the 4.1-Myear-old site. We also investigated root decomposition in fertilized plots at the youngest and oldest sites; when roots were produced and decomposed in fertilized plots, root decomposition rates increased with N and P additions at the 4.1-Myear-old site. At the 300-year-old site, however, root decomposition rates did not respond to N or P additions. Roots decomposed faster than leaves at the more infertile sites, in part because of lower lignin-to-nitrogen ratios in roots than in leaf litter. Decomposing roots immobilized more nutrients than did decomposing leaves, and may serve an important role in retaining nutrients in these forests. Received: 30 November 1998 / Accepted: 12 August 1999     

大兴安岭典型森林沼泽植物叶片和细根碳氮磷化学计量特征

探究大兴安岭典型森林沼泽不同植物叶片和细根生态化学计量特征,能够为进一步认识高纬度气候敏感生态系统养分利用策略和物质循环过程提供依据。对大兴安岭地区兴安落叶松-苔草、兴安落叶松-笃斯越桔-藓类和兴安落叶松-杜香-泥炭藓3种典型森林沼泽19种优势和亚优势维管植物叶片和细根碳氮磷计量特征(C∶N∶P)进行比较,分析不同森林沼泽类型、植物生长型和菌根类型叶片和细根C∶N∶P差异,通过标准化主轴回归分析叶片与细根C∶N∶P的关系。结果表明: 叶片C∶N∶P在种间水平具有最大的变异(42.5%～84.6%),且叶片和细根种间变异大小均为N∶P>C∶N>C∶P。土壤养分和水分含量较高的兴安落叶松-苔草沼泽叶片与细根C∶N和C∶P值较低,且3种森林沼泽植物叶片和细根N∶P均小于10,受N限制。草本植物叶片C∶P和细根C∶N、C∶P显著低于木本植物。外生菌根和杜鹃花类菌根植物叶片和细根C∶N和C∶P高于丛枝菌根和无菌根植物,且杜鹃花类菌根植物叶片和细根C∶P显著高于外生菌根植物。不同森林沼泽、生长型、菌根类型植物叶片和细根C∶N和C∶P差异明显,而N∶P相对稳定。森林沼泽植物叶片与细根C∶N、C∶P和N∶P呈线性正相关,植物地上与地下部分在生态化学计量特征上存在协同。     

黄土丘陵区植物叶片与细根功能性状关系及其变化

通过植物叶片功能性状(比叶面积、叶组织密度、叶氮含量)和细根功能性状(比根长、根组织密度、根氮含量)间的相互关系,分析植物对环境的适应途径;然后根据性状间的差异进行了层次聚类,将物种划分为3大功能型,并分析了不同功能型对环境的适应策略.结果表明:黄土丘陵区延河流域149种植物的叶氮含量与比叶面积和根氮含量正相关、与叶组织密度负相关,比根长与根组织密度负相关,除了根氮含量,其余根性状与叶性状不相关.此外,功能性状间关系变化和适应策略在不同功能型之间也存在差异.功能型1的植物具有最强的耐旱力和防御力;功能型3的植物具有最强的养分维持能力用以对抗营养贫瘠的环境;功能型2的植物居中,生长速率最高,具有较强的竞争力、分布最广;根据C-S-R理论,功能型1和3属于“胁迫忍耐型”策略(S策略),功能型2则属于“竞争型”(C)和“干扰型”(R)策略的综合.研究结果为黄土丘陵区植被恢复规划及物种配置等提供依据.     

Is N‐resorption efficiency related to secondary compounds and leaf longevity in coexisting plant species of the arid Patagonian Monte,Argentina?

Leaf longevity and nutrient resorption efficiency are important strategies to conserve plant nutrients. Theory suggests a negative relationship between them and also proposes that high concentration of phenolics in long‐lived leaves may reduce nutrient resorption. In order to provide new evidence on these relationships, we explored whether N‐resorption efficiency is related to leaf longevity, secondary compounds and other leaf traits in coexisting plant species of different life forms in the arid Patagonian Monte, Argentina. We assessed N‐resorption efficiency, green leaf traits (leaf mass per area (LMA), leaf longevity and lignin, total soluble phenolics and N concentrations) and N concentration in senescent leaves of 12 species of different life forms (evergreen shrubs, deciduous shrubs and perennial grasses) with contrasting leaf traits. We found that leaf longevity was positively correlated to LMA and lignin, and negatively correlated to N concentration in green leaves. N concentrations both in green and senescent leaves were positively related. N‐resorption efficiency was not associated with the concentration of secondary compounds (total soluble phenolics and lignin) but it was negatively related to LMA and leaf longevity and positively related to N concentration in green leaves. Furthermore, leaf traits overlapped among life forms highlighting that life forms are not a good indicator of the functional properties (at least in relation to nutrient conservation) of species. In conclusion, our findings indicated that differences in N‐resorption efficiency among coexisting species were more related to N concentration in green leaves, leaf lifespan and LMA than to the presence of secondary compounds at least those assessed in our study (soluble phenolics and lignin). Accordingly, N‐resorption efficiency seems to be modulated, at least in part, by the productivity–persistence trade‐off.     

Variations in leaf and root stoichiometry of Nitraria tangutorum along aridity gradients in the Hexi Corridor,northwest China

Nitrogen (N) and phosphorus (P) concentrations and N: P ratios between leaves and roots of Nitraria tangutorum along aridity gradients were studied. N. tangutorum was relatively limited by N in April (mean leaf N: P ratio = 11.13) and by P in August (mean leaf N: P ratio = 38.78). N and P in both leaves and roots were highly correlated across sampling sites. In April both leaf and root N and P concentrations increased along aridity gradients. Mean leaf N: P ratios changed slightly, but mean root N: P ratios increased with increasing aridity gradients. We suggest that leaf N: P ratios can indicate nutrient status at different plant growth stages, and root N: P ratios can signify if the amount of soil nutrients is insufficient.     

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.     

Altitudinal differences in UV absorbance,UV reflectance and related morphological traits of Quercus ilex and Rhododendron ferrugineum in the Mediterranean region

We studied the variations in different physiological parameters associated with UV-B radiation defense: UV-B radiation absorbance, UV-visible spectral reflectance, carotenoids concentration, leaf thickness, SLW (specific leaf weigth) and trichome density in Quercus ilex growing at 200 and 1200 m and Rhododendron ferrugineum growing at 2200 m. We examined the role of these parameters as protection mechanisms in an altitudinal gradient of increasing UV radiation in northern Catalonia and in sun and shade leaves. The concentration of UV-B radiation absorbing pigments was 15% higher in sun leaves of Q. ilex at 1200 m than in those from 200 m altitude. Sun leaves of R. ferrugineum presented concentrations three times higher than those of Q. ilex. Reflectance ranged between 5% (in the region 300–400 nm) and 12% (in the region 280–300 nm). The variation of reflectance with altitude followed an inverse trend respect to absorbance in the 280–300 nm region, with higher values the lower the altitude, but in the 300–400 nm region, reflectance of the lower site was the lowest. In both species and altitudes sun leaves presented higher concentrations of UV-B radiation absorbing pigments and UV reflectance than shade leaves. Quercus ilex trees of the higher location presented higher NDPI (Normalized Difference Pigment Reflectance Index) values, indicating higher carotenoids/chlorophyll a ratio. Actual measurements of carotenoid/chlorophyll a ratio confirmed this pattern. The photochemical reflectance index (PRI) presented higher values the higher the location indicating lower photosynthetic radiation-use efficiency. Specific leaf weight (SLW) and leaf thickness were larger in Q. ilex trees of higher location than in those of lower location. In both sites, sun leaves also presented larger SLW values than shade leaves. Adaxial leaf hair density in sun leaves was significantlly higher in the lower location. UV absorption and linked morphological traits (SLW, leaf thickness measured in Q. ilex) presented the larger differences among studied plants at different altitudes and seem to be the dominant UV protecting mechanisms.     

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。     

Relative growth rate and biomass allocation in 20 Aegilops (Poaceae) species

This paper analyses relationships between relative growth rate ( rgr ), seed mass, biomass allocation, photosynthetic rate and other plant traits as well as habitat factors (rainfall and altitude) in 20 wild species of Aegilops L. and one closely related species of Amblyopyrum (Jaub. & Spach) Eig., which differ in ploidy level (diploid, tetraploid and hexaploid). The plants were grown hydroponically for 20 d in a growth chamber. The relationships between parameters were calculated either using the phylogenetic information (phylogenetically independent contrasts, PIC) or without using the phylogenetic information (trait values of taxa, TIP). The results using the two approaches were very similar, but there were a few exceptions in which the results were different (e.g. rgr vs. seed mass). Specific leaf area ( sla ) was positively correlated with leaf area ratio ( lar ) and negatively correlated with net assimilation rate ( nar ), which together resulted in the absence of a correlation between sla and rgr . Leaf photosynthetic rates (expressed on a mass or area basis) showed no correlation with rgr . rgr was positively correlated with the stem mass ratio and negatively with root mass ratio. Species with a lower d. wt percentage have a higher rgr . Aegilops species from locations with higher annual rainfall invested less biomass in roots and more in shoots (leaves and stems) and had a higher rgr . Diploid species had a lower seed mass and initial mass than the hybrids (tetraploid and hexaploid species), but there was no correlation of rgr with ploidy level. Polyploid species, which have higher seed mass, occur at a higher altitude than diploid species. Our results show that variation in rgr in Aegilops and Amblyopyrum spp. is associated mainly with variation in biomass allocation (proportion of biomass in stems and roots) and d. wt percentage, and not with variation in sla , leaf photosynthetic rates or seed mass.     

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.