Leaf damage and functional traits along a successional gradient in Brazilian tropical dry forests

Herbivory has significant impacts on individual plants and plant communities, both at ecological and evolutionary time scales. In this context, this study aims to evaluate herbivore damage and its relationship with leaf chemical and structural traits, nutritional status, and forest structural complexity along a successional gradient. We predicted that trees in early successional stages support conservative traits related to drought tolerance (high specific leaf mass and phenolics), whereas trees in light-limited, late successional stages tend to enhance light acquisition strategies (high nitrogen content). We sampled 261 trees from 26 species in 15 plots (50 × 20 m; five per successional stage). From each tree, twenty leaves were collected for leaf trait measures. Phenolic content increased whereas specific leaf mass and nitrogen content decreased from early to late stages. However, leaf damage did not differ among successional stages. Our results partially corroborate the hypothesis that early successional plants in tropical dry forests exhibit leaf traits involved in the conservative use of water. The unexpected decrease in nitrogen content along the chronosequence is likely related to the fact that thinner leaves with low specific leaf mass could have less nitrogen-containing mesophyll per unit area. Mechanisms affecting herbivory intensity varied across scales: at the species level, leaf damage was negatively correlated with tannin concentration and specific leaf mass; at the plot level, leaf damage was positively affected by forest structural complexity. Herbivory patterns in tropical forests are difficult to detect because abiotic factors and multiple top-down and bottom-up forces directly and indirectly affect herbivores.     

Interspecific variation of plant traits associated with resistance to herbivory among four species of Ficus (moraceae)

• Background and aims To understand the defensive characteristics of interspecies varieties and their responses to herbivory damage, four species of Ficus plants (Ficus altissima, F. auriculata, F. racemosa and F. hispida) were studied. They were similar in life form, but differed in successional stages. Of these, Ficus altissima is a late successional species, F. hispida is a typical pioneer and F. auriculata and F. racemosa are intermediate successional species. We addressed the following questions: (1) What is the difference in plant traits among the four species and are these traits associated with differences in herbivory damage levels? (2) What is the difference in the damage-induced changes among the four species?• Methods Herbivory damage was measured in the field on randomly planted seedlings of the four species of the same age. Defences to herbivory were also tested by feeding leaves of the four species to larvae of Asota caricae in the laboratory. A total of 14 characters such as water content, thickness, toughness, pubescence density on both sides, leaf expansion time, lifetime and the contents of total carbon (C), nitrogen (N), phosphorous (P), potassium (K), magnesium (Mg) and calcium (Ca) were measured. Leaf calcium oxalate crystal (COC) density, total Ca and N content, leaf toughness and height were measured to investigate induced responses to artificial herbivory among the four species.• Key results and conclusions Herbivory damage in the four studied species varied greatly. The pioneer species, F. hispida, suffered the most severe herbivory damage, while the late successional species, F. altissima, showed the least damage. A combination of several characteristics such as high in content of N, Ca and P and low in leaf toughness, lifetime and C : N ratio were associated with increased herbivore damage. The late successional species, F. altissima, might also incorporate induced defence strategies by means of an increase in leaf COC and toughness.Key words: Calcium oxalate crystals, defensive characteristics, Ficus; herbivory, induced defence     

Herbivory in canopy gaps created by a typhoon varies by understory plant leaf phenology

1. Availabilities of light and soil nitrogen for understory plants vary by extent of canopy gap formation through typhoon disturbance. We predicted that variation in resource availability and herbivore abundance in canopy gaps would affect herbivory through variation in leaf traits among plant species. We studied six understory species that expand their leaves before or after canopy closure in deciduous forests. We measured the availabilities of light, soil nitrogen, soil water content, and herbivore abundance in 20 canopy gaps (28.3–607.6 m²) formed by a typhoon and in four undisturbed stands. We also measured leaf traits and herbivory on understory plants. 2. The availabilities of light and soil nitrogen increased with increasing gap size. However, soil water content did not. The abundance of herbivorous insects (such as Lepidoptera and Orthoptera) increased with increasing gap size. 3. Concentrations of condensed tannins, total phenolics, and nitrogen in leaves and the leaf mass per area increased in late leaf expansion species with increasing gap size, whereas none of the leaf traits varied by gap size in early leaf expansion species. 4. Herbivory increased on early leaf expansion species with increasing gap size, but decreased on late leaf expansion species. In these late leaf expansion species, total phenolics and C : N ratio had negative relationships with herbivory. 5. These results suggested that after typhoon disturbance, increased herbivory on early leaf expansion species can be explained by increased herbivore abundance, whereas decreased herbivory on late leaf expansion species can be explained by variation in leaf traits.     

Shade tolerance and herbivory are associated with RGR of tree species via different functional traits

• Relative growth rate (RGR) plays an important role in plant adaptation to the light environment through the growth potential/survival trade‐off. RGR is a complex trait with physiological and biomass allocation components. It has been argued that herbivory may influence the evolution of plant strategies to cope with the light environment, but little is known about the relation between susceptibility to herbivores and growth‐related functional traits.
• Here, we examined in 11 evergreen tree species from a temperate rainforest the association between growth‐related functional traits and (i) species’ shade‐tolerance, and (ii) herbivory rate in the field. We aimed at elucidating the differential linkage of shade and herbivory with RGR via growth‐related functional traits.
• We found that RGR was associated negatively with shade‐tolerance and positively with herbivory rate. However, herbivory rate and shade‐tolerance were not significantly related. RGR was determined mainly by photosynthetic rate (A_max) and specific leaf area (SLA). Results suggest that shade tolerance and herbivore resistance do not covary with the same functional traits. Whereas shade‐tolerance was strongly related to A_max and to a lesser extent to leaf mass ratio (LMR) and dark respiration (R_d), herbivory rate was closely related to allocation traits (SLA and LMR) and slightly associated with protein content.
• The effects of low light on RGR would be mediated by A_max, while the effects of herbivory on RGR would be mediated by SLA. Our findings suggest that shade and herbivores may differentially contribute to shape RGR of tree species through their effects on different resource‐uptake functional traits.

     

Leaf traits and water relations of 12 evergreen species in Costa Rican wet and dry forests: patterns of intra-specific variation across forests and seasons

This study examined variation in leaf traits and water relations in 12 evergreen and semideciduous woody species that occur in both seasonal wet and dry forests in Costa Rica and compared intra-specific leaf–trait correlations to those found in inter-specific global studies. The following traits were measured in both forests across seasons for 2 years: leaf nitrogen (N), leaf carbon (C), specific leaf area (SLA), toughness, cuticle thickness, leaf thickness, and leaf lifespan (LLS). Leaf water potential (LWP) and water content (LWC) were measured as indices of plant available water. Canopy openness, soil moisture, and herbivory were also measured to compare environmental variation across sites. Although species contributed the greatest amount to variation in traits, season, forest, and their interaction had a large influence on patterns of intra-specific leaf–trait variation. Leaf traits that contributed most to variation across sites were C, LWP, leaf thickness, and SLA. Traits that contributed most to variation across seasons were leaf toughness, LWP, and LWC. Furthermore, leaf traits were more correlated (i.e., number and strength of correlations) in the dry than in the wet forest. In contrast to results from global literature syntheses, there was no correlation between LLS and N, or LLS and SLA. Both light and water availability vary seasonally and may be causing variation in a number of leaf traits, specifically those that relate to water relations and leaf economics. Strong seasonality may cause leaf–trait relationships at the local scale to differ from those documented in continental and global-scale studies.     

The predictability of traits and ecological interactions on 17 different crosses of hybrid oaks

Herbivory on hybrid plants has the potential to affect patterns of plant evolution, such as limiting gene-flow through hybrids, and can also affect herbivore biodiversity. However, few studies have surveyed multiple hybrid species to identify phylogenetic patterns in the inheritance of plant traits that may drive herbivory. We surveyed 15 leaf traits and patterns of chewing, mining, and galling herbivory in a common garden of 17 artificially crossed hybrid oak species and each of their parental species over a 2-year period. Using a phylogeny of oaks, we tested whether hybrids that resulted from more divergent parents received more herbivory than those derived from closely related parents (as would be predicted by a build-up of incompatibilities in defensive systems over evolutionary time) and found only marginal evidence in support of this. We found that chewing damage to hybrids was weakly predicted by the relatedness of a parental species to the single native oak. The levels of chewing and mining herbivory on hybrids were typically intermediate to those of their parental species, though less than the parental mean for chewing damage in 2008. Most leaf traits of hybrids were also intermediate to those of their parental species. There was no clear pattern in terms of an association between 11 species of cynipid gall wasps and hybrids. The patterns of (1) intermediate levels of herbivory on hybrids and (2) no trend in herbivory on hybrids based on the phylogenetic relatedness of parental species suggest that herbivory may not play a general role in limiting hybrid fitness (and thus gene-flow through hybrids) in oaks.     

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.     

Palatability, decomposition and insect herbivory: patterns in a successional old-field plant community

We tested the hypothesis that selective feeding by insect herbivores in an old‐field plant community induces a shift of community structure towards less palatable plant species with lower leaf and litter tissue quality and may therefore affect nutrient cycling. Leaf palatability of 20 herbaceous plant species which are common during the early successional stages of an old‐field plant community was assayed using the generalist herbivores Deroceras reticulatum (Mollusca: Agriolomacidae) and Acheta domesticus (Ensifera: Gryllidae). Palatability was positively correlated with nitrogen content, specific leaf area and water content of leaves and negatively correlated with leaf carbon content and leaf C/N‐ratio. Specific decomposition rates were assessed in a litter bag experiment. Decomposition was positively correlated with nitrogen content of litter, specific leaf area and water content of living leaves and negatively correlated with leaf C/N‐ratio. When using phylogentically independent contrasts the correlations between palatability and decomposition versus leaf and litter traits remained significant (except for specific leaf area) and may therefore reflect functional relationships. As palatability and decomposition show similar correlations to leaf and litter traits, the correlation between leaf palatability and litter decomposition rate was also significant, and this held even in a phylogenetically controlled analysis. This correlation highlights the possible effects of invertebrate herbivory on resource dynamics. In a two‐year experiment we reduced the density of above‐ground and below‐ground insect herbivores in an early successional old‐field community in a two‐factorial design by insecticide application. The palatability ranking of plants showed no relationship with the specific change of cover abundance of plants due to the reduction of above‐ or below‐ground herbivory. Thus, changes in the dominance structure as well as potentially associated changes in the resource dynamics are not the result of differences in palatability between plant species. This highlights fundamental differences between the effects of insect herbivory on ecosystems and published results from vertebrate‐grazing systems.     

Congruency analysis of species ranking based on leaf traits: which traits are the more reliable?

Nine leaf traits (area, fresh weight, dry weight, volume, density, thickness, specific leaf area (SLA), dry matter content (LDMC), leaf nitrogen content (LNC)) from ten plant species at eight sites in southern mediterranean France were investigated in order to assess their variability along a climatic gradient and their ranking congruency power. After examination of trait correlation patterns, we reduced the nine initial leaf traits to four traits, representative of three correlation groups: allometric traits (dry weight), functional traits (SLA and dry matter percentage) and Leaf Thickness. We analysed the variability of these four leaf traits at species and site level. We observed that between species variation (between 64.5 for SLA and 91% for LDMC) is higher than within species variation. Allowing a good congruency of species ranking assessed by spearman rank correlation () and a good reallocation of individuals to species by discriminant analysis. A site level variability (between 0.7% for Dry weight and 6.9% for SLA) was identified and environmental parameters (altitude, temperature, precipitation, nitrogen, pH) were considered as probable control factors. We found significant correlation between SLA, LDMC and the average minimum temperature (respectively r=0.87 and r=-0,9) and no correlation for the other traits or environmental parameters. Furthermore, we conclude that two leaf traits appear to be central in describing species: specific leaf area (SLA), percentage of dry matter (LDMC. While, SLA and LDMC are strongly correlated, LDMC appears to be less variable than SLA. According to our results the Dry Matter Content (or its reversal Leaf Water Content) appears the best leaf trait to be quantified for plant functional screening. Leaf thickness appeared to be rather uncorrelated with other leaf traits and show no environmental contingency; its variability could not have been explained in this study. Further studies should focus on this trait. This revised version was published online in June 2006 with corrections to the Cover Date.     

Assessing the latitudinal gradient in herbivory

Plant–herbivore interactions occur in all ecosystems and provide a major avenue for energy flow to higher trophic levels. A long‐standing hypothesis to explain the latitudinal gradient in species diversity proposes that the relatively stable and frost‐free climate of the tropics should lead to more intense biotic interactions in tropical compared with temperate environments, giving rise to a greater diversity of plants and herbivores. Herbivory rates have been compared across latitudes to test this biotic interactions hypothesis, with herbivory typically being measured from observable leaf damage. However, we argue that a measure of percentage leaf damage alone does not straightforwardly reflect the cost of herbivory to the plant, and on its own does not constitute an appropriate test of the biotic interactions hypothesis. For a given amount of herbivory, the impact of herbivory is dependent upon many factors, such as the construction cost of the leaf, the growth and replacement rates and leaf life span. We investigate the latitudinal gradient in herbivory by analysing a large dataset of herbivory rates for 452 tree species and separating the species into those with short and long leaf life spans. We show that annual herbivory rates tend to be greater at lower latitudes for evergreen species (which have long‐lived leaves), but no trend in herbivory rate with latitude was found for species with short leaf life spans. Phylogenetic least squares regression assuming Ornstein‐Uhlenbeck processes also showed a negative effect of latitude on herbivory rate for evergreen trees, but we caution that viewing herbivory as a species trait is problematic. An integrative approach that incorporates leaf life span, as well as the costs of investment in growth and potential costs of losing leaf tissue, is needed to further our understanding of the ecological and evolutionary dynamics of herbivory.     

海南岛热带山地雨林演替后期幼树的叶片特征

植物的生理生态特征决定了植物在生态系统中的分布模式和物种的丰度。本文在开展样地调查的基础上,应用Li-6400光合测定系统研究了海南岛热带山地雨林原始林3个层次的6个优势种与9个伴生种幼树的光合作用参数,并测定了相应叶片的比叶面积（SLA）和氮、磷含量。15个种的SLA为38.2~143.7 cm²·g^-1、单位面积最大光合速率（A_-area）为2.77~7.61 μmol·m^-2·s^-1、单位干重最大光合速率（A_-mass）为21.2~83.4 μmol·kg^-1·s^-1,单位面积暗呼吸速率（R_d-area）为0.02~1.15 μmol·m^-2·s^-1、单位干重暗呼吸速率（R_d-mass）为0.19~12.61 μmol·kg^-1·s^-1,光补偿点（LCP）为2.5~32.2 μmol·m^-2·s^-1,表观量子效率（Ф）为0.006 6~0.042 8 μmol·μmol^-1 photon,叶片氮（LN）含量为7.98~23.63 mg·g^-1,叶片磷（LP）含量为3.98~13.40 mg·g^-1。中上层种的幼树具有较高的比叶面积、单位干重最大光合速率和表观量子效率;上层种的暗呼吸速率最低;幼树叶片的氮、磷含量随物种成树所在层次升高而减少,次序为下层种>中层种>上层种,但差异均不显著（P>0.05）。优势种和伴生种的光响应参数与SLA存在相关关系。伴生种的LN与SLA正相关（P<0.01）,LP与SLA负相关（P<0.05）;优势种的LN、LP与SLA不相关（P>0.05）。     

Leaf herbivory and nutrients increase nectar alkaloids

Correlations between traits may constrain ecological and evolutionary responses to multispecies interactions. Many plants produce defensive compounds in nectar and leaves that could influence interactions with pollinators and herbivores, but the relationship between nectar and leaf defences is entirely unexplored. Correlations between leaf and nectar traits may be mediated by resources and prior damage. We determined the effect of nutrients and leaf herbivory by Manduca sexta on Nicotiana tabacum nectar and leaf alkaloids, floral traits and moth oviposition. We found a positive phenotypic correlation between nectar and leaf alkaloids. Herbivory induced alkaloids in nectar but not in leaves, while nutrients increased alkaloids in both tissues. Moths laid the most eggs on damaged, fertilized plants, suggesting a preference for high alkaloids. Induced nectar alkaloids via leaf herbivory indicate that species interactions involving leaf and floral tissues are linked and should not be treated as independent phenomena in plant ecology or evolution.     

Reprint of: Drivers of within-tree leaf trait variation in a tropical planted forest varying in tree species richness

In plant ecology, community-weighted trait means are often used as predictors for ecosystem functions. More recently, also within-species trait variation has been confirmed to contribute to ecosystem functioning. We here go even further and assess within-individual trait variation, assuming that every leaf in a plant individually adjusts to its micro-environment. Using forest plots varying in tree species richness (Sardinilla experiment, Panama), we analysed how leaf traits within individual trees vary along the vertical crown gradient. Furthermore, we tested whether niche partitioning in mixed stands results in a decrease of within-species leaf trait variation and whether niche partitioning can be also observed at the level of individual trees. We focused on leaf traits that describe the growth strategy along the conservative-acquisitive spectrum of growth. We found a decrease in within-species variation of specific leaf area (SLA) with increasing neighbourhood species richness. Both sampling height and local neighbourhood richness contributed to explaining within-species leaf trait variation, which however, varied in importance among different species and traits. With increasing sampling height, leaf dry matter content (LDMC), carbon to nitrogen ratio and lignin content increased, while leaf nitrogen concentration (leaf N), SLA, cellulose and hemicellulose decreased. Variation in leaf N decreased with increasing neighbourhood species richness, while the magnitude of within-individual variation of most traits was unaffected by neighbourhood species richness. Our results suggest an increased niche partitioning with increasing species richness both in a plant community and at the level of individual plants. Our findings highlight the importance of including within-individual trait variation to understand biodiversity-ecosystem functioning relationships.     

Drivers of within-tree leaf trait variation in a tropical planted forest varying in tree species richness

In plant ecology, community-weighted trait means are often used as predictors for ecosystem functions. More recently, also within-species trait variation has been confirmed to contribute to ecosystem functioning. We here go even further and assess within-individual trait variation, assuming that every leaf in a plant individually adjusts to its micro-environment. Using forest plots varying in tree species richness (Sardinilla experiment, Panama), we analysed how leaf traits within individual trees vary along the vertical crown gradient. Furthermore, we tested whether niche partitioning in mixed stands results in a decrease of within-species leaf trait variation and whether niche partitioning can be also observed at the level of individual trees. We focused on leaf traits that describe the growth strategy along the conservative-acquisitive spectrum of growth. We found a decrease in within-species variation of specific leaf area (SLA) with increasing neighbourhood species richness. Both sampling height and local neighbourhood richness contributed to explaining within-species leaf trait variation, which however, varied in importance among different species and traits. With increasing sampling height, leaf dry matter content (LDMC), carbon to nitrogen ratio and lignin content increased, while leaf nitrogen concentration (leaf N), SLA, cellulose and hemicellulose decreased. Variation in leaf N decreased with increasing neighbourhood species richness, while the magnitude of within-individual variation of most traits was unaffected by neighbourhood species richness. Our results suggest an increased niche partitioning with increasing species richness both in a plant community and at the level of individual plants. Our findings highlight the importance of including within-individual trait variation to understand biodiversity-ecosystem functioning relationships.     

Convergent succession of plant communities is linked to species’ functional traits

Functional traits reflecting the resource economy and growth strategy of plants vary widely both within and among ecosystems. Theory suggests that trait variation within a community may determine the relative abundance of species, though this idea requires more empirical support.We set up a long-term succession experiment in a nutrient-poor wetland, planting seedlings of twelve fenland species in different relative abundances and absolute densities, thereby creating 24 communities. The biomass of these species and the soil water and nutrient status of the system were monitored over ten years. Using these data, we could relate the changing relative abundance of species to five traits – leaf dry matter content (LDMC), leaf nitrogen concentration (LNC), specific leaf area (SLA), relative growth rate (RGR), and seed mass (SM).The initial communities converged after ten years to a common dominance–diversity structure, with two species accounting for 82% of total biomass. Soil water and nutrient conditions remained largely constant. By the end of the experiment, community trait structure had changed so that species functional traits were significantly related to their relative abundance. The most abundant species had high LDMC and SM, but low RGR and SLA, and varied little in LNC, suggesting that investment in leaf structure and retention of nutrients were most important for species dominance under low nutrient conditions. Our results provide experimental evidence that dominance–subdominance structures in plant communities are governed by functional traits.     

黄土高原不同退耕年限坡地植物比叶面积与养分含量的关系

对黄土高原不同退耕年限坡地植物比叶面积(SLA)和养分含量进行研究,探明其随生境条件而发生的变异及其与土壤理化特性之间的关系.结果表明,立地和物种水平植物SLA存在显著差异,SLA变化范围各不相同,植物叶片C、N和P含量以及C/N 、N/P和C/P在不同退耕年限坡地间不具有一致性的变化,这表明不同物种叶性因子随生境发生的变化较为复杂.草地植物叶片SLA和叶片C含量为负相关,与N、P含量呈极显著的正相关(P<0.01).土壤理化特性对叶片SLA和养分含量的关系因物种而异,综合所有植物进行分析,土壤理化特性与植物SLA的相关性不明显,但与叶片养分含量关系密切.所以,生境条件的差异可能是植物叶片结构特性和养分组成发生变化的重要原因,但调控植物叶性特征的因素较为复杂,不同的植物具有各自相应的对生境条件的适应机制.     

Defence against vertebrate herbivores trades off into architectural and low nutrient strategies amongst savanna Fabaceae species

Herbivory contributes substantially to plant functional diversity and in ways that move far beyond direct defence trait patterns, as effective growth strategies under herbivory require modification of multiple functional traits that are indirectly related to defence. In order to understand how herbivory has shaped plant functional diversity, we need to consider the physiology and architecture of the herbivores and how this constrains effective defence strategies. Here we consider herbivory by mammals in savanna communities that range from semi‐arid to humid conditions. We posited that the saplings of savanna trees can be grouped into two contrasting defence strategies against mammals, namely architectural defence versus low nutrient defence. We provide a mechanistic explanation for these different strategies based on the fact that plants are under competing selection pressures to limit herbivore damage and outcompete neighbouring plants. Plant competitiveness depends on growth rate, itself a function of leaf mass fraction (LMF) and leaf nitrogen per unit mass (N_m). Architectural defence against vertebrates (which includes spinescence) limits herbivore access to plant leaf materials, and partly depends on leaf‐size reduction, thereby compromising LMF. Low nutrient defence requires that leaf material is of insufficient nutrient value to support vertebrate metabolic requirements, which depends on low N_m. Thus there is an enforced tradeoff between LMF and N_m, leading to distinct trait suites for each defence strategy. We demonstrate this tradeoff by showing that numerous traits can be distinguished between 28 spinescent (architectural defenders) and non‐spinescent (low nutrient defenders) Fabaceae tree species from savannas, where mammalian herbivory is an important constraint on plant growth. Distributions of the strategies along an LMF‐N_m tradeoff further provides a predictive and parsimonious explanation for the uneven distribution of spinescent and non‐spinescent species across water and nutrient gradients.     

Differences in response to simulated herbivory between <Emphasis Type="Italic">Quercus crispula</Emphasis> and <Emphasis Type="Italic">Quercus dentata</Emphasis>

To evaluate the responses of Quercus crispula and Quercus dentata to herbivory, their leaves were subjected to simulated herbivory in early spring and examined for the subsequent changes in leaf traits and attacks by chewing herbivores in mid summer. In Quercus crispula, nitrogen content per area was higher in artificially damaged leaves than in control leaves. This species is assumed to increase the photosynthetic rate per area by increasing nitrogen content per area to compensate leaf area loss. In Quercus dentata, nitrogen content per area did not differ between artificially damaged and control leaves, while nitrogen content per mass was slightly lower in artificially damaged leaves. The difference in their responses can be attributable to the difference in the architecture of their leaves and/or the severeness of herbivory. The development of leaf area from early spring to mid summer was larger in artificially damaged leaves than in control leaves in both species, suggesting the compensatory response to leaf area loss. Leaf dry mass per unit area was also larger in artificially damaged leaves in both species, but the adaptive significance of this change is not clear. In spite of such changes in leaf traits, no difference was detected in the degree of damage by chewing herbivores between artificially damaged and controlled leaves in both species.     

Leaf damage decreases fitness and constrains phenotypic plasticity to drought of a perennial herb

Mediterranean-type ecosystems are increasingly prone to drought stress. Herbivory might limit plant functional responses to water shortage. This may occur as a result of plant resource depletion or due to the fact that leaf damage and drought may elicit opposite phenotypic responses. We evaluated the impact of herbivory on plant fitness in the field, and the effects of leaf damage on phenotypic plasticity to reduced soil moisture in a greenhouse. The study species was Convolvulus demissus, a perennial herb endemic to central Chile, which has a Mediterranean-type climate. Controlled herbivory by chrysomelid beetles (natural herbivores) in the field had a negative impact on plant fitness, estimated as number of fruits. Whereas reduced soil moisture alone did not affect seedling survival, damaged seedlings (simulated herbivory) had greater mortality when growing under water shortage. The hypothesis that herbivory would constrain phenotypic plasticity was supported by significant statistical interactions between leaf damage and soil moisture, followed by inspections of reaction norms. This was verified both overall (all phenotypic traits taken together, MANOVA) and in four of the six traits evaluated (ANOVAs). When plants were damaged, the reaction norms in response to low soil moisture of water use efficiency, root:shoot ratio and xylem water potential showed reduced slopes. While undamaged plants increased root biomass in response to low moisture, the opposite trend was found for damaged plants. The simultaneous occurrence of herbivory and drought events might curtail recruitment in plant populations of central Chile and other Mediterranean-type ecosystems due to the inability of damaged seedlings to show functional responses to low soil moisture. This finding is of ecological significance in view of current and projected trends of increased aridity in these ecosystems.     

真红树和半红树植物叶片氯含量及叶性状的比较

 依据红树植物在潮间带的分布,将其分为真红树植物和半红树植物两大类。但对一些过渡地带种类的归属问题一直存在争议。该研究选取国内大部分红树植物,比较其成熟叶片中的Cl含量、肉质化程度、比叶面积（SLA）、单位重量叶氮含量（N_mass）和单位面积叶氮含量（N_area）,并对争议树种重新进行界定。结果表明：1）真红树植物叶片中Cl含量和肉质化程度远高于半红树植物;2）真红树植物具有低SLA和高N_area的特点,除水芫花(Pemphis acidula)外半红树植物具有高SLA和低N_area的特点。3）争议的7种红树植物中,银叶树（Heritiera littoralis）、海漆（Excoecaria agallocha）、卤蕨（Acrostichum aureum ）和尖叶卤蕨（Acrostichum speciosum）归为半红树植物更合适;老鼠（Acanthus ilicifolius）和小花老鼠（Acanthus ebrecteatus）归为真红树植物。木果楝（Xylocarpus granatum）有待进一步研究。