Aims The Wami River system is among the most important rivers for riparian plant biodiversity conservation but it is potentially threatened by anthropogenic activities. This study was aimed to determine riparian plant species diversity and distribution patterns in relation to the anthropogenic disturbances.
Methods The transect method was used to collect vegetation data. Transects were established perpendicular to the river at intervals of 50 m downstream and five plots were systematically established, separated by 5-m distance along each transect.
Important findings A total of 261 plant species in 68 families were recorded in the Wami River system with a Shannon diversity index in the range of 1.63–2.94 and a significantly decreasing trend downstream. Using the two-way indicator species analysis (TWINSPAN), three plant communities (A, B and C) emerged based on variations in riparian plant species composition among sites. Canonical correspondence analysis (CCA) indicated that the spatial pattern of riparian plant species was significantly influenced by environmental variables. This implies that the plant species composition gradients and spatial assemblages of vegetation communities are a result of human disturbances. Because of the fragile nature of the riparian system, some species are more vulnerable than others and hence there is an urgent need for better land use planning to conserve riparian plant biodiversity in the sub-basin of Wami River.

Aims Silvicultural management plays a major role in shaping understory diversity through its action on stand structure. In many parts of Europe, recent socioeconomic changes have led to the progressive abandonment of coppicing in favor of high forest (HF) management. In order to examine how this change impacts understory species, we compared old coppice-with-standards and HF stands in terms of structural features and understory richness and composition, also taking into account the diagnostic species pool of the habitat. Since the management systems for coppices and HFs differ in cutting regime, we expect that they would cause different changes in floristic composition and richness.
Methods The study area was the Montagne della Duchessa massif, in central Italy. Structural differences and floristic richness were compared, and the diagnostic species diversity was analyzed using rarefaction curves and Rényi diversity profiles. Differences in understory composition were analyzed through indicator species analysis.
Important findings Our results showed that, though the old coppices have a slightly higher number of understory species in general, the HF stands have greater mean species richness in both understory and diagnostic species, the latter being more evenly distributed inside the community. These finding were related to the cut regime, which favor a constant canopy cover over time and thus the maintenance of more stable microclimatic conditions, promoting the higher abundance and evenness of shade-tolerant and vernal species. Conversely, the dense canopy of the old coppice appears to affect the understory richness by reducing the presence of light-demanding species, but still without a complete recolonization of the shade-tolerant species. Overall, our findings provide the first insights supporting that, in a Mediterranean montane context, old coppice conversion to HF could over time improve the species diversity in these habitats and help maintain good conservation status of the typical mature beech forests.

Aims Extreme climatic events may have important consequences for plant community structure and composition. In 2005, a severe drought together with a cold winter promoted extensive damage and mortality in shrubland communities of southwest Spain (Do?ana National Park). Here, we aim to identify the mechanisms underlying community stability (resistance and resilience) in response to this extreme climatic event, considering changes in the functional structure of these communities.
Methods We used a trait-based approach, quantifying variations in 10 functional traits at the community level (community weighted means, CWM) and the functional diversity (functional richness, evenness and divergence) in 18 plots at three different times: predating the climatic event (estimated from the sum of the live and dead volume of each species in 2007), and 2 and 8 years after the 2005 episode. We also quantified the differences in functional traits and functional diversity between adult and recruit stages, which allowed us to better understand the contribution of the recruitment to the maintenance of the functional structure and diversity of the community.
Important findings Communities with higher functional divergence before the climatic event maintained nearly constant their levels of functional divergence 8 years after, but they were more prone to changes in species composition. Community resistance in terms of vegetation cover was positively correlated with root dry matter content, whereas community resilience was positively correlated with leaf chlorophyll (LChl). We also found that some values (weighted means) of functional community traits (such as root dry matter content and LChl) had increased 2 years after the event, returning to the pre-event conditions after 8 years. In addition, there was hardly any establishment of new species in the community and the recruits did not make substantial differences to the community functional structure. Only seed mass differed significantly between the adult and seedling stages. In summary, the extreme climatic event induced rapid vegetation changes, modifying several functional properties of the community, but, in spite of the occurrence of changes in species composition, a rapid convergence of these shrubland communities took place due to the replacement of species with functional redundancy, thus recovering the initial conditions and supporting the existence of strong mechanisms of functional resilience.

Aims We aimed to test the hypothesis that plants that grow at lower latitudes will be better structurally defended than plants from higher latitudes.
Methods We collated binary spinescence data for 5145 species across Australia and New Zealand. Our dataset spanned 35° of latitude, and included over 1 million observations, making it the largest empirical study ever conducted for a single physical defence trait. A weighted logistic regression was applied first within Australia and New Zealand separately, and then across the combined dataset.
Important findings There was no significant latitudinal gradient in the proportion of species with spinescence in Australia or New Zealand, or in the overall dataset. That is, plant species are no more likely to be defended by spines at low latitudes than at high latitudes. This finding is counter to the idea that plant defences increase with latitude due to increased selective pressure from higher levels of herbivory. We suggest that future studies should investigate the relationship between herbivory and defence directly, without using latitude as a proxy.

Aims Long-term nitrogen (N) fertilization has profound impacts on community structure and ecosystem function, but little is known about its effects on plant phenology. Furthermore, no published study has examined effects of N chemical forms on plant phenology.
Methods In an alpine meadow on the Tibetan Plateau, we monitored reproductive phenology of six common plant species after 8 years of fertilization with different N chemical forms (addition of 7.5g N m ?2 yr^-1 in the forms of ammonium, nitrate and ammonium nitrate), with no N addition as the control.
Important findings Eight years of N fertilization affected plant reproductive phenology, and such effects depended on the species, N form and phenological phase. Fertilization with ammonium generally delayed, advanced or did not change flowering and fruiting phases of the alpine plants. Furthermore, fertilization with ammonium affected the temporal dispersion of reproductive phenology among the six species, especially among the late-flowering species. This could reduce the overlap of flowering and fruiting and increase phenological complementarity. Fertilization with nitrate only delayed the senescence phase of Elymus nutans, and fertilization with ammonium nitrate did not affect reproductive phenology of the six alpine plants. N fertilization with any form increased the overlap in senescence among the six species. We conclude that long-term N fertilization can cause shifts in plant phenology and such effects depend on N chemical forms. Our results also suggest that phenological complementarity could be a mechanism underlying resource partitioning and thus species coexistence in the face of changing N availability with different chemical forms.

Aims Variation in precipitation strongly influences plant growth, species distributions and genetic diversity. Intraspecific variation in phenotypic plasticity, the ability of a genotype to alter its growth, morphology or physiology in response to the environment, could influence species responses to changing precipitation and climate change. Despite this, the patterns and mechanisms of intraspecific variation in plasticity to variable precipitation, and the degree to which genotype responses to precipitation are influenced by variation in edaphic conditions, remain poorly understood. Thus, we determined whether genotypes of a widespread C₄ grass (Panicum virgatum L., switchgrass) varied in aboveground productivity in response to changes in precipitation, and if site edaphic conditions modified genotype aboveground productivity responses to precipitation. We also determined if genotype productivity responses to precipitation are related to plasticity in underlying growth and phenological traits.
Methods Nine P. virgatum genotypes originating from an aridity gradient were grown under four treatments spanning the 10th to the 90th percentiles of annual precipitation at two sites in central Texas: one site with deep, fine-textured soils and another site with shallow, coarse-textured soils. We measured volumetric soil water content (VWC), aboveground net primary productivity (ANPP), tiller production (tiller number), average tiller mass, canopy height, leaf area index (LAI) and flowering time on all plants at both sites and examined genotype responses to changes in precipitation.
Important findings Across precipitation treatments, VWC was 39% lower and more variable at the site with shallow, coarse-textured soils compared to the site with deep, fine-textured soils. ANPP averaged across genotypes and precipitation treatments was also 103% higher at the site with deep, fine-textured soils relative to the site with shallow, coarse-textured soils, indicating substantial differences in site water limitation. Where site water limitation was higher, ANPP of most genotypes increased with increasing precipitation. Where site water limitation was less, genotypes expressed variable plasticity in response to precipitation, from no change to almost a 5-fold increase in ANPP with increasing precipitation. Genotype ANPP increased with greater tiller mass, LAI and later flowering time at both sites, but not with tiller number at either site. Genotype ANPP plasticity increased with genotype tiller mass and LAI plasticity at the site with deep, fine-textured soils, and only with genotype tiller mass plasticity at the site with shallow, coarse-textured soils. Thus, variation in genotype ANPP plasticity was explained primarily by variation in tiller and leaf growth. Genotype ANPP plasticity was not associated with temperature or aridity at the genotype's origin. Edaphic factors such as soil depth and texture may alter genotype ANPP responses to precipitation, and the underlying growth traits contributing to the ANPP response. Thus, edaphic factors may contribute to spatial variation in genotype performance and success under altered precipitation.

Aims Supratidal plant communities fulfil a vital role in coastal protection, but despite an increased likelihood of seawater flooding resulting from anthropogenic climate change, we understand little about how tidal inundation affects these habitats or interactions between their component species. Our aim was to determine how three common coastal grassland species responded to simulated seawater flooding and how subsequent changes to their ecophysiology, growth and survival might affect plant–plant interactions in mixed assemblages.
Methods Seeds of three widely distributed European coastal grassland species (Leontodon autumnalis Asteraceae, Plantago lanceolata Plantaginaceae and Trifolium pratense Fabaceae) were collected from a coastal grassland site in South West England. In Experiment 1, we quantified changes in leaf ion (K +, Na +, Cl ?) concentrations as a response to short-duration (0, 2, 8 or 24h) immersion in seawater of the root-zone before monitoring longer-term effects on plant survival and growth. In a second experiment, we examined community-level responses by subjecting mixed assemblages of all three species to seawater immersion for (0, 12, 24 or 96h).
Important findings When grown individually, one species (Trifolium) had markedly reduced survival with increasing soil immersion time, but a consistent decline in plant growth for all species with flooding duration was most likely linked to osmotic and ionic stresses caused by salt ion accumulation. In mixed assemblages, all species suffered increased mortality and reduced growth following seawater flooding, although the relative contribution of one species (Leontodon) to total biomass increased in flooded microcosms. We thus demonstrate a number of species-specific responses to simulated seawater flooding and show that when grown together, interactions between plants are altered as a consequence. We argue that variation in the responses of component plant species will dictate how coastal plant communities respond to, and recover from, expected changes in sea levels and transient floods following storm surge events. Such information is vital in order to predict future impacts of seawater floods on supratidal vegetation.

Aims Relative growth rate (RGR) is an indicator of the extent to which a species is using its photosynthates for growth and it is affected by environmental factors, including temperature. Nevertheless, most of plant growth studies have been carried out at a single growth temperature or at different temperature treatments, resulting in the lack of information on the relationship between RGR and changing mean daily air temperature. We analyzed the temporal changes in RGR during early growth stages in three Cistus species grown outdoor in a common garden from seeds of different provenances. Moreover, we wanted to define the relationship between daily changes in RGR and mean daily air temperature for the considered provenances. The hypothesis that intra-specific temporal variations in RGR can reflect differences in the behavior to maximize RGR (RGR max) in response to temperature was tested.
Methods Seedlings of C. salvifolius, C. monspeliensis and C. creticus subsp. eriocephalus were grown outdoor in the experimental garden of the Sapienza University of Rome under a Mediterranean climate. We analyzed early growth with non-linear growth models and calculated function-derived RGRs as the derivative with respect to time of the parameterized functions used to predict height divided by current height. The relationships between function-derived RGRs and mean daily air temperature were analyzed by linear and non-linear models, which were ranked according to their standard errors and correlation coefficients. The temperature dependency of RGR max per each provenance was evaluated through the relationship between RGR max and the coefficients of the best regression model obtained.
Important findings A parameter that could summarize the temperature dependency of RGR up to RGR max during the early growth stages for the selected provenances was defined. This allowed us to highlight that a greater RGR temperature responsiveness was related to a delay in the time to reach RGR max independently by the species. Nevertheless, a greater temperature sensitivity of RGR lead to a reduced maximum height which reflects a negative trade-off between the length of the developmental phases and the extent of RGR temperature responsiveness. Thus, variations in temperature responsiveness of RGR up to RGR max have a significant role in shaping the early growth for the investigated species. Our findings quantitatively define provenance dependent strategies by which the selected species cope with daily air temperature variations during early growth.

Aims The pine rocklands of southern Florida are a fire-dependent forest associated with outcrops of limestone. Pine rockland plants have several adaptations to fire, and for many species, burning increases plant growth, flowering and seedling establishment. The pine rockland forest has been reduced and fragmented in recent decades. Outside of Everglades National Park, only 2% of the original pine rocklands remain, and they are in the form of small fragments. Our objective is to investigate the effects of fragmentation and habitat quality on abundance and plant reproductive fitness of Angadenia berteroi (A.D.C.) Miers, a threatened species of the southern Florida pine rockland.
Methods We estimated the density of plants using a stratified random sampling design, and reproductive fitness (in terms of percentage of plants with flowers and fruit) by walking transects in an array of habitat fragments of different sizes and degrees of isolation (distance to the nearest fragment) as well as in continuous habitat. Structural equation modeling (SEM) was employed to investigate how A. berteroi reproductive fitness was affected by fragmentation and habitat quality.
Important findings Habitat fragment size was correlated with the density of A. berteroi, but did not have a great impact on its reproductive success. However, habitat quality represented by litter depth and subcanopy cover had strong negative effects on the reproductive fitness of A. berteroi, suggesting that increased light availability and low litter cover resulting from recent fires may favor reproduction.

Aims Vegetation succession depends on the availability of suitable propagules in the soils, thus knowledge of soil seed banks is essential for formulating effective strategies for restoring the vegetation of degraded sites. The W National Park, the only trans-boundary biosphere reserve in West Africa, is being extensively fragmented and degraded in recent decades. The aims of this study were to assess the reserve's soil seed banks, their relationships with standing vegetation and bundle of disturbances and their potential significance for vegetation restoration.
Methods The size and composition of the above-ground species vegetation were assessed in nine plots of 1 ha each representing a range of habitats with differing disturbance severity (low, intermediate and high). A total of 702 soil samples were taken from three layers (0–3, 3–6 and 6–9cm) and soil seed bank was analyzed using the seedling emergence technique.
Important findings Generally, seeds of non-woody taxa dominated in samples from all soil depths and habitats of all disturbance severities. The mean soil seed density was 17.8, 24.4 and 26.3 seeds/dm 3 in samples from the least, intermediate and most disturbed sites, respectively, and highest in the upper soil layers in all cases. The results indicate that there is limited potential for restoring woody vegetation solely from soil seed banks, and that woody species in the region rely more on recently shed seeds trapped in the standing dead biomass and litter on the ground than soil seed banks for regeneration. Thus, human intervention is needed to accelerate forest recovery, mainly through alleviating anthropogenic impacts on the ecosystem (for instance, avoiding destruction of new seeds by intense fire), and site manipulation to improve environmental conditions for seedling establishment and growth. Other ways of restoring forests than through the soil seed bank (e.g. sowing seeds collected elsewhere, and planting tree seedlings) could also be relevant.

Aims Positive plant interactions can promote higher species density of beneficiary species in deserts. However, there is limited evidence examining the trait sets of seeds from beneficiary species. In this study, we examined the hypothesis that shrubs (benefactors) influence the germination of desert annuals (beneficiaries) and promote ecotypic differentiation by generating distinct microhabitats through abiotic stress amelioration. The following predictions were tested using growth chambers and field-collected seeds: (i) seed mass and viability will be greater and less variable for seeds collected from within shrub understory relative to seeds from open microhabitats, (ii) germination of seeds from shrub and open microhabitats will be greatest under simulated home (source) conditions, (iii) seeds from the shrub microhabitat will adaptively accelerate their germination rate when germinated in simulated home (source) microhabitats relative to their simulated away (reciprocal) microhabitat.
Methods Seeds and their associated maternal plants were collected from four annual species found within a shrub understory (Larrea tridentata) and open microhabitats in the Mojave Desert of California (35.30oN, 117.26oW, 793 m. a.s.l.), and then reciprocally germinated in growth chambers simulating both microclimatic conditions. Cumulative germination and germination rate was measured every 4–5 days for 42 days.
Important findings There was no significant difference in the mean or coefficient of variation for seed mass and viability between the shrub and open microhabitats. The source of the seeds did not significantly impact the cumulative germination, and there was no accelerated rate of germination within potential species ecotypes thereby suggesting no ecotypic differentiation. Cumulative germination was significantly higher within the shrub-simulated microhabitat for three out of the four species examined. Cumulative germination and germination rate were significantly different between species. Hence, shrubs influence the germination of desert annuals, and the outcome of this interaction is species specific, but shrub microhabitats do not necessarily alter the more conserved seed biology traits. Future studies should examine the influence of gene flow on beneficiary adaptation and the influence of species-specificity on beneficiary species response to facilitation.

Aims The study of the adaptive potential of the germination patterns of invading species enables us to identify some traits linked with their capacity to colonize new sites, and to gain a better understanding of their area of distribution. The aim of this study is to determine the germination pattern of Ulex europaeus, a cosmopolitan invasive species, in relation to temperature and to explore its potential evolution and invasiveness in a tropical region, following its introduction from Europe.
Methods We studied the germination pattern of U. europaeus (the common gorse) to test both physical dormancy and germination capacity within the range of temperatures found in the native and invasive regions. To understand its germination pattern and its evolution, the rate and the speed of germination, as well as the percentage of seeds that became mouldy during the experiment, have been compared between a native habitat, France and a habitat into which it has been introduced, the tropical island of La Reunion.
Important findings The results show that gorse seeds germinate in large quantities, possess the ability to germinate under a wide range of temperatures and they confirm the physical dormancy of the seeds (caused by seed coat impermeability).The decrease in germination from 25oC upwards, coupled with an increase in the rate of moulding help to explain its restricted distribution at altitude in tropical environments. For scarified seeds, we have not detected any difference between the two regions, neither in the percentage of germinated seeds, nor in the percentage of mouldy seeds. However, seeds from Reunion germinate faster at 20oC than seeds from France and a greater number of seeds from Reunion are able to germinate without scarification (10–60% for Reunion versus 0–10% for France). These results suggest that while preserving the advantages of the native habitat, in Reunion gorse develops a strategy which favours the rapid occupation of new sites.

Aims More data are needed about how genetic variation (GV) and environmental factors influence phenotypic variation within the natural populations of long-lived species with broad geographic distributions. To fill this gap, we examined the correlations among environmental factors and phenotypic variation within and among 13 natural populations of Pinus tabulaeformis consisting of four demographically distinct groups within the entire distributional range.
Methods Using the Akaike's Information Criterion (AIC) model, we measured 12 morphological traits and constructed alternative candidate models for the relationships between each morphological trait and key climatic variables and genetic groups. We then compared the AIC weight for each candidate model to identify the best approximating model for ecogeographical variation of P. tabulaeformis. The partitioning of variance was assessed subsequently by evaluating the independent variables of the selected best models using partial redundancy analysis.
Important findings Significant phenotypic variation of the morphological traits was observed both within individual populations and among populations. Variation partition analyses showed that most of the phenotypic variation was co-determined by both GV and climatic factors. GV accounted for the largest proportion of reproductive trait variation, whereas local key climatic factors (i.e. actual evapotranspiration, AET) accounted for the largest proportion of phenotypic variation in the remaining investigated traits. Our results indicate that both genetic divergence and key environmental factors affect the phenotypic variation observed among populations of this species, and that reproductive and vegetative traits adaptively respond differently with respect to local environmental conditions. This partitioning of factors can inform those making predictions about phenotypic variation in response to future changes in climatic conditions (particularly those affecting AET).

Aims Nectar is one of the most common floral rewards offered to pollinators by plants. Depending on the plant species, nectar is offered openly or in tubes of various lengths restricting accessibility of this resource for flower visitors with short mouthparts. If attracting pollinators that match floral morphology increases pollination efficiency, flowers could profit from signaling nectar-tube depth to pollinators. Since flower colors are important signals in plant–pollinator communication, we investigated whether and which different chromatic or achromatic aspects of flower color might indicate nectar-tube depth or whether flower colors facilitate the differentiation between flowers with long nectar tubes by means of high chromatic uniqueness.
Methods To this end, we collected flower reflectance spectra of 135 grassland plant species. We analyzed flower colors as raw reflectance spectra in principal component analysis (PCA) and in the color space of honeybees.
Important findings The correlation between flower colors and tube depths was weak. From the bee's point of view, blue flowers had on average deeper tubes than green, blue-green and UV-green flowers potentially allowing insects to predict tube depths based on blue color. Spectral purity did not correlate with nectar-tube depth, nor did the chromatic uniqueness of flower colors in the honeybee color space. Dominant wavelength showed a significant but very weak correlation with tube depth. The achromatic green contrast decreased with increasing tube depth as did brightness; thus deep tubes were less conspicuous than shallow tubes. Chromatic components resulting from PCA did not or only slightly correlate with tube depth. Our results illustrate that flower colors may have a certain potential to indicate tube depth, i.e. nectar accessibility, from a bee's perspective.

Aims Floral traits in animal-pollinated plants are proposed to be selected by the behavior of pollinators, which create differential fitness. However, fitness estimation is not trivial and there is no agreed or universal measure of fitness. In plants, fitness can be measured in various ways, including the number of fruits or seeds, probability of survival, or growth rate.
Methods Because each fitness measure can be associated with different pollinator behavior, estimating pollinator-mediated selection on floral traits can differ among various fitness measures. We used the annual Mediterranean plant, Linum pubescens, as a model to assess the relative role of various fitness measures in estimating pollinator-mediated selection on floral traits. We compared four maternal fitness measures and estimated their relative advantage in assessing natural selection on floral traits of L. pubescens. To identify whether each trait is under pollinator-mediated selection, we used mediational analysis.
Important findings We found that each floral trait was under natural selection assessed by a different fitness measure. The color combination of floral tube throat and stamen color was under selection when using seed mass as a fitness measure, and floral diameter was under positive directional selection when the number of seeds or number of fruits was used as a fitness measure. Selection on floral color was not mediated by pollinators' visitation rates, while flower diameter showed partial pollinator-mediated selection. We conclude that using several fitness measures gives an insight into the mechanisms underlying phenotypic selection on a floral trait, and facilitates the understanding of pollinator-mediated selection.