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Interaction of global change drivers affects forest resilience. Land‐use changes (land abandonment) and climate change (a higher frequency and intensity of droughts) are interacting in the Mediterranean Region. Components of resilience in secondary stem growth have been widely studied but, despite the importance of root systems in forest functionality and resilience, non‐previous studies have assessed them in coarse roots.In this study, we use Juniperus thurifera tree‐ring chronologies in coarse roots and stems to assess biomass allometry and tree resilience to drought events comparing two stages of a forest expansion gradient (mature forests and transition zone) in Alto Tajo Natural Park. We extracted cores of stems and coarse roots in 48 trees distributed in different developmental stages and calculated cross‐sectional area increments, root‐stem allometric relationship and resilience components for both organs in each individual for two drought events (2005 and 2012).Stem and root growth as well as its allometric exponent were higher in the transition zone than in mature forests. Both organs exhibited a trade‐off between resistance and recovery in mature forests but maintenance of higher values in the transition zone. Resilience did not show differences between organs being higher in the transition zone than in mature forests. However, relative resilience in roots in the transition zone was higher than in mature forests, without differences in stems between stages. Finally, the 2012 drought event showed a higher impact on the components of resilience than the 2005 drought event.Synthesis. This study extends the knowledge of root response to drought events and highlights the potential of land‐use legacies to reduce the negative impact of climate change by promoting increased root recovery after drought events in trees established in past agricultural lands. [ABSTRACT FROM AUTHOR]

Competition simultaneously limits the availability of above‐ and below‐ground resources for plants. How plants respond to density with changes in patterns of biomass allocation is poorly understood. Previous studies had inconsistent results, but emphasised increased biomass allocation to stems in response to density. However, the response of plants to density may depend on environmental conditions and on characteristics of the species.We grew 43 herbaceous plant species at three densities (1, 8 and 64 individuals per pot) and two nutrient levels in a common garden and measured biomass allocation to roots (RMF), leaves (LMF) and stems (SMF), and specific root (SRL) and stem length (SSL). The species differed in functional group (grasses, forbs and legumes), life span and realised niche with respect to nutrients (Ellenberg's nutrient indicator value).Intraspecific competition and self‐thinning increased with nutrient supply. Overall, plants increased their RMF with density independent of nutrient level, indicating that competition was mainly for below‐ground resources. However, characteristics of the species influenced their responses to density and nutrients in terms of biomass allocation, SRL and SSL. At high densities, legumes were more productive than the other functional groups and hardly changed their allocation patterns, suggesting that they were less nutrient limited due to their mutualism with nitrogen‐fixing rhizobia. The SRL of perennials was lower, and their RMF was higher and increased more strongly in response to density than that of annuals, which could be interpreted as mechanisms to increase survival. The realised niche of species with respect to nutrients influenced the response to density and nutrients in terms of SMF, LMF, SRL and SSL in line with adaptations to both nutrient availability and competition for light in the typical habitats.Synthesis. We found that intraspecific competition was mainly for below‐ground resources, which may be typical for many species growing in moderately nutrient‐rich but high‐light habitats. Our results show that growth conditions, species characteristics and their interactions influence patterns of biomass allocation and plant morphology. [ABSTRACT FROM AUTHOR]

While tree diversity has been proven to enhance above‐ground forest biomass in many instances, the effect on below‐ground biomass has often been neutral, or even negative. This raises the questions of whether above‐ground results are the product of a reduced allocation below‐ground in more diverse forests, which could imply a more efficient acquisition of below‐ground resources per unit root, and whether the effects of diversity have been correctly quantified and interpreted in the past.We addressed these issues using data from a tree‐based functional diversity experiment where 24 mixtures and their respective monocultures were analysed in a fully replicated design. We used species‐level measurements of above‐ and below‐ground biomass to assess how adding below‐ground biomass changes our interpretations regarding the roles of complementarity effects (niche partitioning or facilitation between species) and selection effects (dominance of high‐yielding species within mixtures).Mixtures showed overyielding of above‐ground biomass but not below‐ground. Although remaining significantly positive, this translated into diversity effects of a lesser magnitude when adding below‐ground biomass. However, species did not reduce their allocation to below‐ground biomass within mixtures compared to monocultures. Rather, this combination of above‐ground overyielding and below‐ground neutral effect was caused by the dominance in mixtures of species with a low below‐ground allocation strategy. Another consequence of these species dominance is that their actual contribution to total productivity within mixtures was overestimated when using only above‐ground biomass, due to their relatively small below‐ground biomass. This caused an overestimation of the selection or dominance effects, thereby causing an underestimation of the relative importance of complementarity effects.Synthesis. This study emphasizes the need to consider both above‐ and below‐ground biomass components when determining the origin and strength of diversity effects, or when attempting to link tree diversity to ecosystem services such as carbon sequestration. The statistical partitioning of net effects is a widely used method, but one which can lead to an overestimation of the role of individual dominant species when below‐ground biomass is not taken into account, hence diminishing the role of positive interactions between species. [ABSTRACT FROM AUTHOR]

Groundwater flow through coastal wetlands plays an important role in the maintenance of productivity of intertidal ecosystems. Groundwater can reduce salinity and increase nutrient availability which can enhance plant growth and alter plant biomass allocation patterns.Here, we used stable isotopes of oxygen and hydrogen to assess how groundwater influences below‐ground and above‐ground growth in the widespread mangrove species Avicennia marina.We found source water within tree stems varied seasonally, with non‐saline water use higher in the wet season when rainwater availability was highest compared to the dry season. Stems with higher proportional contribution of non‐saline water had increased above‐ground growth but no effect on below‐ground growth. Below‐ground growth was however influenced by nutrient availability across the intertidal zone which was higher in the high‐ compared to the low‐intertidal zone.Synthesis. This study shows that mangroves use non‐saline groundwater and rainwater when available rather than saline water sources. Groundwater flows into the intertidal stimulates organic matter accumulation in above‐ground biomass suggesting the availability of non‐saline water sources, such as groundwater and rainfall, are important for the growth and productivity of mangrove forests. [ABSTRACT FROM AUTHOR]

Correlations among plant traits often reflect important trade‐offs or allometric relationships in biological functions like carbon gain, support, water uptake, and reproduction that are associated with different plant organs. Whether trait correlations can be aggregated to "spectra" or "leading dimensions," whether these dimensions are consistent across plant organs, spatial scale, and growth forms are still open questions.To illustrate the current state of knowledge, we constructed a network of published trait correlations associated with the "leaf economics spectrum," "biomass allocation dimension," "seed dimension," and carbon and nitrogen concentrations. This literature‐based network was compared to a network based on a dataset of 23 traits from 2,530 individuals of 126 plant species from 381 plots in Northwest Europe.The observed network comprised more significant correlations than the literature‐based network. Network centrality measures showed that size traits such as the mass of leaf, stem, below‐ground, and reproductive tissues and plant height were the most central traits in the network, confirming the importance of allometric relationships in herbaceous plants. Stem mass and stem‐specific length were "hub" traits correlated with most traits. Environmental selection of hub traits may affect the whole phenotype. In contrast to the literature‐based network, SLA and leaf N were of minor importance. Based on cluster analysis and subsequent PCAs of the resulting trait clusters, we found a "size" module, a "seed" module, two modules representing C and N concentrations in plant organs, and a "partitioning" module representing organ mass fractions. A module representing the plant economics spectrum did not emerge.Synthesis. Although we found support for several trait dimensions, the observed trait network deviated significantly from current knowledge, suggesting that previous studies have overlooked trait coordination at the whole‐plant level. Furthermore, network analysis suggests that stem traits have a stronger regulatory role in herbaceous plants than leaf traits. Correlations among plant traits often reflect important relationships in biological functions like carbon gain, support, water uptake, and reproduction. We illustrate the correlations among 23 traits of 126 plant species using a graphical network approach. The analysis suggests that biomass allocation traits and stem traits have a stronger regulatory role in herbaceous plants than leaf traits. [ABSTRACT FROM AUTHOR]

Trait differences among plants are expected to influence the outcome of competition; competition should be strongest between similar species (or individuals) under limiting similarity, and between dissimilar species within competitive hierarchies. These hypotheses are often used to infer competitive dynamics from trait patterns within communities. However, plant traits are frequently plastic in response to competition. This variation is poorly accounted for in trait-based studies of competition and community assembly., To explore the relationship between trait responses and competitive outcomes, we grew 15 species alone, in monoculture and in mixture. We measured traits relating to leaf and root tissue morphology as well as biomass allocation and related competition-induced changes in these traits to intra- and interspecific competition using multi-model inference. Additionally, we tested how traits from different competitive environments influenced potential community assembly inferences., The competitive environment had large effects on species' traits, although many effects were species specific. Differences among species in how competition affected trait expression were linked to both intra- and interspecific competition, frequently affecting competitive hierarchies. Intraspecific competition was lower for species that limited competition-induced increases in root allocation and had less variability in this trait overall. Interspecific competition was lower for species with larger leaves and lower specific leaf area than their neighbours. Switching to more stress-tolerant strategies by increasing root diameter and leaf tissue density also reduced competition. However, dissimilarity in root tissue density also minimized competition, consistent with limiting similarity affecting competitive outcomes. Moreover, changes in these traits were linked to changes in functional diversity, suggesting that competition affects functional diversity by affecting trait expression., Synthesis. Both trait hierarchies and trait dissimilarity affect the outcome of competition by acting on different traits, although competition-induced changes in trait expression can alter competitive outcomes. Moreover, the magnitude of these trait changes suggests that the source environment where plant traits are collected can affect the inferences drawn from trait patterns within communities. Combined, our results suggest that considering the effect of competition on trait expression is critical to understanding the relationship between traits and community assembly. [ABSTRACT FROM AUTHOR]

Climate change and atmospheric deposition of nitrogen (N) affect the biodiversity patterns and functions of ecosystems world-wide. While many single-factor studies have quantified ecosystem responses to single global change drivers, less is known about the interaction effects of these drivers on ecosystem functions., Here, we present the results of a three-year field and a two-year glasshouse experiment, in which we assessed responses of Calluna vulgaris heathlands to the single and combined effects of drought events (D) and N fertilization (D: 25% precipitation reduction in the field experiment and 20-50% soil water content reduction in the glasshouse experiment; N fertilization: 35 kg N ha−1 year−1)., We examined the effects of D and N treatments on growth responses of the dominant dwarf shrub Calluna vulgaris (in terms of biomass production and allocation, tissue δ13C signatures and C:N ratios) in relation to two plant life-history stages and different 'ecotypes' (sub-Atlantic vs. subcontinental heathlands)., Plant responses varied strongly with life-history stage, and the interaction of N and D showed lower effects than would be expected based on additive responses to single factors. While D treatments had no effects on Calluna in the building phase (ca. ten-year-old plants), seedlings (particularly one-year-old plants) were highly susceptible to drought. Differences in response patterns were attributable to the high shoot-root ratios typical of young Calluna plants. These ratios decreased with progressing life history as a result of increasing below-ground biomass investments. Below-ground biomass production and shoot-root ratios differed between plants from the different heathland sites., Tissue δ13C signatures decreased and C:N ratios increased with plant age as a result of decreasing evaporative demands (per unit root biomass). N fertilization increases the shoot-root ratios and thereby the drought susceptibility of Calluna plants., Synthesis. Our findings suggest that plant responses to global change are difficult to anticipate by means of single-factor studies or by focusing on a single life-history stage. This highlights the need for global change research to include multiple factors and life-history stages when assessing an ecosystem's susceptibility to shifts in environmental conditions. [ABSTRACT FROM AUTHOR]

Rain forest understorey perennial plants can be frequently exposed to leaf area losses induced by herbivory or physical damage from falling canopy debris. In dioecious species, tolerance to defoliation may differ between genders (e.g. females may suffer more than males), but this topic has so far received little attention., Here, we quantified gender-dependent effects of increased levels (0-100%) of sustained defoliation (applied bi-annually for 2 years) on vital rates in three economically important dioecious understorey palm species in the genus Chamaedorea ( C. elegans, C. ernesti- augustii and C. oblongata). We also quantified gender differences in functional and life-history traits and assessed the direct reproductive costs in terms of biomass allocation to reproduction., In the three species, non-defoliated (control) females were smaller and had three to seven times higher reproductive allocation than males., Defoliation did not affect survivorship in any of the three species, except in the 100% defoliation treatment. Stem growth ( RGR) and especially reproduction (probability of reproduction and reproductive output) were negatively affected by defoliation. Females of C. ernesti-augustii suffered higher mortality than males at 100% defoliation, but this was not the case for the other two species. Also, only in C. ernesti-augustii females exhibited lower RGR than males. In all species, the probability of reproduction did not differ between genders. The reproductive output (production rate of inflorescences) differed among genders only in C. ernesti-augustii, where males were more productive than females., Interestingly, in most cases, defoliation effects on vital rates did not differ significantly between males and females, indicating that tolerance to defoliation was similar between genders. Such results were independent of plant size (stem length)., Synthesis. Our results do not support the prevailing theory that the greater reproductive costs of females will lead to reduced tolerance to stresses such as defoliation. The implications of these results and their importance for designing sustainable leaf harvesting regimes are discussed. [ABSTRACT FROM AUTHOR]

1. Plant plastic responses to herbivore damage may include rapid, active reallocation of plant resources to reduce the impact of herbivory on future plant fitness. However, whether these inducible tolerance responses can be extended to pine trees and how these responses could be modulated by genetic and environmental factors remains unclear. 2. Biomass allocation and phosphorus (P) and nitrogen (N) concentrations in above- and below-ground tissues were measured in Pinus pinaster juveniles belonging to 33 open-pollinated families grown under two P availabilities (P-deficient and complete fertilization). Measurements were taken 15 days after half of the plants received a foliar spray treatment of 22 mmol L−1 methyl jasmonate (MJ) to simulate above-ground herbivore attack. 3. Simulated above-ground herbivory promoted a strong preferential allocation of biomass below ground in the form of fine roots, leading to an almost two-fold increase in fine root biomass in MJ-treated plants and a significant reduction in above-ground tissues and coarse roots. In addition, MJ signalling increased P and N concentrations in the shoots while reducing (P) or maintaining (N) concentrations in the roots. These results suggest that induced resource sequestration is not a generalized strategy in this pine species. Fine root biomass and concentration of N and P in plant tissues showed additive genetic variation, but responses to MJ signalling did not vary among families. Allocation of biomass to fine roots was not affected by P availability, whereas allocation of P to the shoot was more intense under complete fertilization. 4. Synthesis: Two new putative tolerance mechanisms inducible by MJ signalling may help to minimize the impact of above-ground herbivore damage on the future fitness of young pine trees by (i) allocation of carbon to fine roots, this appeared to be a generalized strategy with weak environmental modulation and (ii) reallocation of P and N from roots to shoots, which was largely affected by P availability, and thus susceptible to greater phenotypic variation in heterogeneous environments. We provide evidence that changes in tolerance-related traits are rapidly inducible by herbivory cues in this pine species. These results should be integrated with induced resistance responses to fully understand the costs and benefits associated with induced responses to herbivory. [ABSTRACT FROM AUTHOR]

Summary 1. The modules of plants experience different levels of resources, and clonal plants can integrate resource heterogeneity. However, no studies have tested whether the benefits of clonal integration depend on patterns of heterogeneity in multiple resources, like high levels of above-ground and below-ground resources in the same patches ('coincident patchiness') or different patches ('reciprocal patchiness'). 2. We hypothesized that the benefits of clonal integration can vary depending on whether patchiness is reciprocal or coincident, and that clonal species experience greater benefits from integration when qualitative patterns of resource heterogeneity are more like those likely to occur in their habitats. To test these hypotheses, we grew pairs of connected ramets of Cynodon dactylon and Potentilla reptans under high and low levels of light and of water and soil nutrients, and measured the growth and physiological traits of the plants. 3. Consistent with the hypotheses, connection between ramets in contrasting patches increased final dry mass of Cynodon by 30% compared with connection between ramets within the same type of patch when resource patchiness was coincident, whereas connection decreased mass by 60% when patchiness was reciprocal. Inconsistent with the hypotheses, between-patch connection increased mass of Potentilla by 70% over within-patch connection whether patchiness was reciprocal or coincident; although the species did grow accumulate more mass when patchiness was reciprocal. 4. In Cynodon, treatments had little effect on allocation of mass to roots or specific leaf area; analysis of mass of ramets within pairs suggested that constraints on translocation may have underlain differential effects of reciprocal and coincident patchiness on performance. In Potentilla, treatments affected all measured characteristics, suggesting a higher degree of clonal integration that may have allowed clones to benefit strongly from integration regardless of pattern of resource patchiness. 5. Synthesis. The ability of some plant species to benefit from clonal integration can depend strongly on whether resource heterogeneity is coincident or reciprocal, while other species may benefit equally from integration under both resource patterns. Our results provide an initial indication that the ecological range of some clonal species may be linked to patterns of resource patchiness via traits of clonal integration. [ABSTRACT FROM AUTHOR]

1. The quantitative relationship between size and reproductive output is a central aspect of a plant’s strategy: the conversion of growth into fitness. As plant allocation is allometric in the broad sense, i.e. it changes with size, we take an allometric perspective and review existing data on the relationship between individual vegetative ( V, x-axis) and reproductive ( R, y-axis) biomass within plant populations, rather than analysing biomass ratios such as reproductive effort ( R/( R+ V)). 2. The allometric relationship between R and V among individuals within a population is most informative when cumulative at senescence (total R– V relationship), as this represents the potential reproductive output of individuals given their biomass. Earlier measurements may be misleading if plants are at different developmental stages and therefore have not achieved the full reproductive output their size permits. Much of the data that have been considered evidence for plasticity in reproductive allometry are actually evidence for plasticity in the rate of growth and development. 3. Although a positive x-intercept implies a minimum size for reproducing, a plant can have a threshold size for reproducing without having a positive x-intercept. 4. Most of the available data are for annual and monocarpic species whereas allometric data on long-lived iteroparous plants are scarce. We find three common total R– V patterns: short-lived, herbaceous plants and clonal plants usually show a simple, linear relationship, either (i) passing through the origin or (ii) with a positive x-intercept, whereas larger and longer-lived plants often exhibit (iii) classical log–log allometric relationships with slope <1. While the determinants of plant size are numerous and interact with one another, the potential reproductive output of an individual is primarily determined by its size and allometric programme, although this potential is not always achieved. 5. Synthesis. The total R– V relationship for a genotype appears to be a relatively fixed-boundary condition. Below this boundary, a plant can increase its reproductive output by: (i) moving towards the boundary: allocating more of its resources to reproduction, or (ii) growing more to increase its potential reproductive output. At the boundary, the plant cannot increase its reproductive output without growing more first. Analysing size-dependent reproduction is the first step in understanding plant reproductive allocation, but more integrative models must include time and environmental cues, i.e. development. [ABSTRACT FROM AUTHOR]

1. Soil communities and their interactions with plants may play a major role in determining the success of invasive species. However, rigorous investigations of this idea using cross-continental comparisons, including native and invasive plant populations, are still scarce. 2. We investigated if interactions with the soil community affect the growth and biomass allocation of the (sub)tropical invasive shrub Chromolaena odorata. We performed a cross-continental comparison with both native and non-native-range soil and native and non-native-range plant populations in two glasshouse experiments. 3. Results are interpreted in the light of three prominent hypotheses that explain the dominance of invasive plants in the non-native range: the enemy release hypothesis, the evolution of increased competitive ability hypothesis and the accumulation of local pathogens hypothesis. 4. Our results show that C. odorata performed significantly better when grown in soil pre-cultured by a plant species other than C. odorata. Soil communities from the native and non-native ranges did not differ in their effect on C. odorata performance. However, soil origin had a significant effect on plant allocation responses. 5. Non-native C. odorata plants increased relative allocation to stem biomass and height growth when confronted with soil communities from the non-native range. This is a plastic response that may allow species to be more successful when competing for light. This response differed between native and non-native-range populations, suggesting that selection may have taken place during the process of invasion. Whether this plastic response to soil organisms will indeed select for increased competitive ability needs further study. 6. The native grass Panicum maximum did not perform worse when grown in soil pre-cultured by C. odorata. Therefore, our results did not support the accumulation of local pathogens hypothesis. 7. Synthesis. Non-native C. odorata did not show release from soil-borne enemies compared to its native range. However, non-native plants responded to soil biota from the non-native range by enhanced allocation in stem biomass and height growth. This response can affect the competitive balance between native and invasive species. The evolutionary potential of this soil biota-induced change in plant biomass allocation needs further study. [ABSTRACT FROM AUTHOR]

1. Water availability is the main determinant of species’ distribution in lowland tropical forests. Species’ occurrence along water availability gradients depends on their ability to tolerate drought. 2. To identify species’ traits underlying drought-tolerance we excavated first year seedlings of 62 dry and moist forest tree species at the onset of the dry season. We evaluate how morphological seedling traits differ between forests, and whether functional groups of species can be identified based on trait relations. We also compare seedling traits along independent axes of drought and shade-tolerance to assess a hypothesized trade-off. 3. Seedlings of dry forest species improve water foraging capacity in deep soil layers by an increased below-ground biomass allocation and by having deep roots. They minimize the risk of cavitation by making dense stems, and reduce transpiration by producing less leaf tissue. Moist forest seedlings have large leaf areas and a greater above-ground biomass, to maximize light interception, and long, cheap, branched root systems, to increase water and nutrient capture. 4. Associations among seedling traits reveal three major drought strategies: (i) evergreen drought-tolerant species have high biomass investment in enduring organs, minimize cavitation and minimize transpiration to persist under dry conditions; (ii) drought-avoiding species maximize resource capture during a limited growing season and then avoid stress with a deciduous leaf habit in the dry season; (iii) drought-intolerant species maximize both below- and above-ground resource capture to increase competitiveness for light, but are consequently precluded from dry habitats. 5. We found no direct trade-off between drought- and shade-tolerance, because they depend largely on different morphological adaptations. Drought-tolerance is supported by a high biomass investment to the root system, whereas shade-tolerance is mainly promoted by a low growth rate and low SLA. 6. Synthesis. We conclude that there are three general adaptation strategies of drought-tolerance, which seemingly hold true across biomes and for different life forms. Drought- and shade-tolerance are largely independent from one another, suggesting a high potential for niche differentiation, as species’ specialization can occur at different combinations of water and light availability. [ABSTRACT FROM AUTHOR]

1. We related above-ground biomass allocation to light interception by trees and lianas growing in three tropical rain forest stands that were 0.5, 2 and 3-year-old regeneration stages after slash and burn agriculture. 2. Stem height and diameter, leaf angle, the vertical distribution of total above-ground biomass and leaf longevity were measured in individuals of three short-lived pioneers (SLP), four later successional species (LS) and three lianas (L). Daily light capture per individual (Φd) was calculated with a canopy model. Mean daily light interception per unit leaf area (Φarea), leaf mass (Φleaf mass) and above-ground mass (Φmass) were used as measures of instantaneous efficiency of biomass use for light capture. 3. With increasing stand age, vegetation height and leaf area index increased while light at the forest floor declined from 34 to 5%. The SLP, Trema micanthra and Ochroma pyramidale, dominated the canopy early in succession and became three times taller than the other species. SLP had lower leaf mass fractions and leaf area ratios than the other groups and this difference increased with stand age. 4. Over time, the SLP intercepted increasingly more light per unit leaf mass than the other species. Lianas, which in the earliest stage were self-supporting and started climbing later on, gradually became taller at a given mass and diameter than the trees. Yet, they were not more efficient than trees in light interception. 5. SLP had at least three-fold shorter leaf life spans than LS and lianas. Consequently, total light interception calculated over the mean life span of leaves (Φleaf mass total = Φarea × SLAdeath leaves× leaf longevity) was considerably lower for the SLP than for the other groups. 6. Synthesis. We suggest that early dominance in secondary forest is associated with a high rate of leaf turnover which in turn causes inefficient long-term use of biomass for light capture, whereas persistence in the shade is associated with long leaf life spans. This analysis shows how inherent tradeoffs in crown and leaf traits drive long-term competition for light, and it presents a conceptual tool to explain why early dominants are not also the long-term dominants. [ABSTRACT FROM AUTHOR]

1 Combining long-term observational studies with comparative physiological ecology can yield a deeper understanding of the contribution of individual function to population and community dynamics. Sonoran Desert winter annuals exhibit striking year-to-year variation in population dynamics that is driven by variable precipitation, but species differ in the strength of demographic response to precipitation and hence in the degree of temporal variance in population dynamics. To understand the physiological mechanisms of differing population dynamic responses to environmental variation, we investigated interspecific differences in functional traits that mediate responsiveness to precipitation. 2 We conducted sequential harvests throughout the growing season to examine relative growth rate and biomass allocation patterns. We then related growth parameters to leaf-level carbon isotope discrimination (a time-integrated measure of water-use efficiency) and long-term demographic variation. 3 We hypothesized that water-use efficiency should trade-off with rapid growth rates. Furthermore, we hypothesized that species having efficient water use should have buffered population dynamics in dry years but sacrifice high growth and fecundity in wet years, resulting in low long-term variance in demographic success. Conversely, species with high growth capacity should be very responsive to infrequent periods of high precipitation and thus exhibit high temporal variance. 4 Species differed in seasonal relative growth rate and allocation patterns. Species with the highest relative growth rates rapidly deployed large leaf area displays following mid-season rainfall. Species with intermediate relative growth rates exhibited high biomass assimilation rates per unit leaf area. Species with low relative growth rates exhibited low leaf area ratios and low assimilation rates per unit leaf area. 5 Relative growth rate was positively related to leaf carbon isotope discrimination, consistent with a trade-off between growth rate and water-use efficiency. 6 Seasonal relative growth rate did not predict long-term demographic variance. However, leaf area plasticity in response to precipitation was positively related to long-term demographic variance. Our results illustrate how morphological and physiological traits influence demographic tracking of environmental variability and demonstrate how species differences in functional strategies determine population and community dynamics. [ABSTRACT FROM AUTHOR]

Summary 1 A field-experiment was used to determine how plant species might retain dominance in an arctic ecosystem receiving added nutrients. We both measured and modelled the above-ground and below-ground biomass allocation and root morphology of non-acidic tussock tundra near Toolik Lake, Alaska, after 4 years of fertilization with nitrogen and phosphorus. 2 Compared with control plots, the fertilized plots showed significant increases in overall root weight ratio, and root biomass, root length and root nitrogen concentration in the upper soil layers. There was a strong trend towards relatively more biomass below ground. 3 We constructed an individual teleonomic (i.e. optimality) plant allocation and growth model, and a competition model in which two plants grow and compete for the limiting resources. 4 The individual plant model predicted a strong decrease in root weight ratio with increased nutrient availability, contrary to the results obtained in the field. 5 The increased investment in roots in the fertilized plots found in the field could be explained in the competition model in terms of luxury consumption of nutrients (i.e. the absorbance of nutrients in excess of the immediate plant growth requirements). For slow-growing species with relatively low phenological and physiological plasticity it can be advantageous to increase relative investment into root growth and root activity. This increased investment can limit nutrient availability to other fast-growing species and, thereby, preclude the successful invasion of these species. 6 These results have implications for the transient response of communities and ecosystems to global change. [ABSTRACT FROM AUTHOR]

Summary 1 Many narrowly endemic species are restricted to distinctive edaphic environments. The adaptations that make these species successful in their restricted habitat may incur a cost, and decrease their success in more common habitats. We compared growth, biomass allocation and root morphology of two narrowly endemic Hakea species (Proteaceae) of Mediterranean south-western Australia with those of five more widespread congeners, in a glasshouse study. The rare Hakea species occur in endangered winter-wet shrublands that grow on skeletal (0–20 cm deep) soils overlying massive ironstone rock, whereas their common congeners occur nearby on deeper wetland and non-wetland soils. 2 The ironstone endemics differed consistently from their widespread congeners in some important root characteristics. During early development they allocated relatively more biomass to their roots, and had a higher specific root length due to a lower average root diameter and a lower root mass density. Therefore, when compared at the same plant mass, the ironstone endemics had a considerably greater total root length. 3 The ironstone endemics also favoured root growth in deeper layers of the substrate: they invested up to 64% of their root mass in the bottom 10 cm of 40-cm-deep pots, vs. 35% for common species. Only in the ironstone endemics did the extension of the main root axis continue at the same rate after reaching the bottom of the pot. 4 We suggest that the observed differences are the consequence of evolutionary trade-offs, and represent specializations of the endemic species to increase the chances of getting access to water before the onset of severe summer drought in these habitats. However, while adaptive in a shallow-soil habitat, these traits may reduce success on deeper soils by compromising both below-ground and above-ground competitive abilities. [ABSTRACT FROM AUTHOR]

1 The morphological plasticity of sun and shade branches of Pinus sylvestris growing at the edge of a ‘tree-patch’ created in 1989, when surrounding trees were removed, was compared with that of branches of trees growing in the centre of the patch. 2 In 1992, we selected 10-year-old branches. Yearly growth increments (long-shoots) and emerging buds were individually marked, architectural parameters measured, the branch topology mapped, and the number of male and female cones counted. In 1993, the survival of growth increments and buds was recorded and the branches were harvested to determine dry mass of growth increments and needles. 3 The size of growth increments produced after 1989, i.e. their length, total dry mass and needle dry mass, decreased in the order sun branches of edge trees > branches of centre trees > shade branches of edge trees. Thus, the growth increments produced on the shade branches of trees that also had branches in the sun were consistently smaller than the growth increments on the branches of centre trees growing completely in the shade. 4 The number of new growth increments produced after 1989 was highest in sun branches and lowest in shade branches of edge trees. Survival of growth increments and buds was higher in edge than in centre trees; no difference was found between sun and shade branches of edge trees. 5 In shade branches of edge trees, branching angles between first- and second-order growth increments were highest and increased from older to younger growth increments. This was interpreted as ‘bending’ towards the edge of the patch. 6 Production of female cones was almost totally restricted to edge trees and higher in sun than in shade branches. 7 One prediction of an optimal foraging strategy, i.e. the production of more growth increments and buds in higher light, was supported by the data, whereas the other prediction, i.e. decreased length of growth increments, could only be supported when it was... [ABSTRACT FROM AUTHOR]

1 Acer mono is one of the earliest germinating species in hardwood forests of northern Japan. To evaluate the advantage of early germination for the seedling establishment, differences in the temporal pattern of leaf development between the seedlings and overstorey trees were investigated, together with the timing of dry mass gain and allocation, survival and mortality agents of seedlings. These traits were contrasted at four sites with different types of foliage phenology in the overstorey trees (FU-1 and FU-2, forest understorey in which overstorey trees unfolded and shed the leaves as a flush and succeedingly, respectively; SG, small gaps; and FE, forest edge). 2 Seasonal growth patterns of the seedlings were greatly affected by the differences in the coupling of leaf development between the seedlings and the overstorey trees. For early germinating cohorts of Acer mono, 79, 61, 50 and 53% of annual dry mass gain occurred within 2 months of germination, in FU-1, FU-2, SG and FE, respectively. After this point (canopy closure) mass increment decreased abruptly in both FU sites, but continued to increase in both SG and FE. Seedling mass, however, increased after September again in FU-2 but not in FU-1, mainly due to earlier leaf shedding of the canopy trees in FU-2. 3 After canopy closure, leaf mass ratio was greatest in FU-1 where light was most limited, but lowest in FE. In contrast, root mass ratio was greatest in FE but lowest in FU-1 where soil moisture was most abundant. These traits might lead to the optimization of growth by making all resources equally limiting even after canopy closure in forest understorey. 4 Higher seedling survival resulting from early germination was observed in all four sites, since predators and pathogens selectively attacked late germinating individuals. The advantage of early germination was greater in both FU-1 and FU-2 than in FE, mainly due to large differences in... [ABSTRACT FROM AUTHOR]

1. Veronica chamaedrys. V. montana and V. officinalis were grown in either shaded or unshaded conditions in a field experiment lasting 18 months. V. officinalis failed to grow beneath shading as a result of slug grazing. Between May and October of the first year. unshaded V. officinalis had the highest relative growth rate (RGR) and shading significantly reduced RGR in both V. chamaedrys and V. montana but to a greater extent in V chamaedrys. 2. The proportion of biomass allocated to roots was rapidly reduced by shading, hut at the end of the experiment differences between species and light environments were negligible. Root phenology was unaffected by shading. In unshaded plants. allocation to stem (SWR) was higher in both V. chamaedrys and V. montana than in V. officinalis. Shading increased SWR and allocation to petioles but only altered stem phenology. The difference in SWR between shaded and unshaded plants of V. montana became less with time. Total allocation to leaves (TLWR) in unshaded plants was ranked V. montana > V. officinalis > V. chamedrys. The contribution of dead leaves to TWLR was greatest in unshaded plants. Shading increased TLWR in V. chamaedrys but not in V. montana. 3. In unshaded plants, biomass allocation to sexual reproduction was ranked V. officinalis > V. chamaedrys > V. montana. Whilst shading reduced allocation to sexual reproduction in V. chamaedrys, it increased allocation in V. montana. Inufiorescences were subdivided into: pedicels plus peduncles: capsules plus calyces; and seeds. A second quotient (`relative allocation') was devised by expressing the biomass allocated to each of these subgroups as a proportion of the total allocated to inflorescences. [ABSTRACT FROM AUTHOR]