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Concerns over the increasing cost and environmental impact of high inorganic nitrogen (N) inputs have led to a reappraisal of the role of legumes, particularly clover, in maintaining soil fertility in improved grasslands. Clover and other legumes host the symbiotic root bacteria Rhizobium that fix N, reducing the need for N fertiliser application. Grass plus clover swards are comparable to grass monocultures given medium to high inorganic N inputs in terms of companion grass growth, livestock performance and, yield of subsequently planted crops. Reduced N fertiliser input also reduces associated N leaching into water and greenhouse gas emissions during manufacture, transport, and application. In addition, increased use of clover in grasslands also benefit flower-visiting insects by providing an abundant source of nectar and pollen in summer. This is a critical period due to high levels of competition for these in summer. Because temporary and improved grassland covers almost half (47%) of UK land area this habitat type has great potential in wildlife conservation. Further research is needed on the agronomic and conservation benefits of more diverse swards, as incorporation of additional forb species may complement clovers and legumes to benefit a wider range of flower-visiting insect species. In addition, more information on the attitudes of farmers for or against using clover and legumes in grasslands is needed, as they make the management decisions for most agricultural land in the UK. Implications for insect conservation: increased use of clover is a low-cost way to improve the food supply for flower-visiting insects, while to sustaining agricultural productivity and reducing environmental impact.

The increasing frequency of wildfires in Southern California’s Mediterranean-type habitats has been facilitating the displacement of native plants by invasive annuals. Black mustard (Brassica nigra) is an abundant, allelopathically harmful, invasive forb, which readily colonizes soil niches following most disturbances. Wildfires, however, are unlike other forms of disturbance because they can fundamentally alter plant–soil interactions through both physical and chemical changes in the soil. Here, a comparative field study of burned and unburned sites suggests that the Woolsey Fire—the largest wildfire ever recorded in California’s Santa Monica Mountains—inhibited dispersal of B. nigra and changed how it interacts with other plant species in the second year of post-fire recovery. More surprisingly, native plants were more likely to replace B. nigra than non-native plants in burned sites. These results indicate the possibility of post-fire seeding with specific “fire follower” native plant species may allow native flora to occupy soil niche space until longer-lived, competitive native shrubs establish.

20 Pág. Departamento de Medio Ambiente y Agronomía​, Restoration of degraded drylands is urgently needed to mitigate climate change, reverse desertification and secure livelihoods for the two billion people who live in these areas. Bold global targets have been set for dryland restoration to restore millions of hectares of degraded land. These targets have been questioned as overly ambitious, but without a global evaluation of successes and failures it is impossible to gauge feasibility. Here we examine restoration seeding outcomes across 174 sites on six continents, encompassing 594,065 observations of 671 plant species. Our findings suggest reasons for optimism. Seeding had a positive impact on species presence: in almost a third of all treatments, 100% of species seeded were growing at first monitoring. However, dryland restoration is risky: 17% of projects failed, with no establishment of any seeded species, and consistent declines were found in seeded species as projects matured. Across projects, higher seeding rates and larger seed sizes resulted in a greater probability of recruitment, with further influences on species success including site aridity, taxonomic identity and species life form. Our findings suggest that investigations examining these predictive factors will yield more effective and informed restoration decision-making., We would like to thank the supporters of the Global Arid Zone Project. The intellectual and energetic input of the network participants made this work possible. We also acknowledge the many employers and funding agencies that supported projects and the authors’ time in preparing this work and contributing data to the GAZP database. Please note that any use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the US Government

We investigated whether plant resistance to soil impoverishment would depend on their flexibility in taking up nutrients and on maintaining elemental stoichiometry. We mixed sand with grassland soil in mass proportions of 0, 10, 30, 50 and 70% to simulate soil impoverishment as caused by a gradient of desertification intensity and examined how plant nitrogen (N) uptake (15NH4NO3 and NH415NO3 labelling) and nutrient stoichiometry were associated with plant growth responses of a sedge (Carex duriuscula) and a forb (Potentilla chinensis). With increasing intensity of soil impoverishment, plant biomass, cover and density decreased for C. duriuscula, but not for P. chinensis. Interestingly, uptake of both 15NO3− and 15NH4+ increased for the sedge but not for the forb, with the former species showing stronger preference of NO3−. However, the sedge showed decreasing nutrient contents and concentrations of phosphorus (P) and magnesium (Mg), and thus increasing stoichiometric ratios of N:P and calcium (Ca):Mg. In contrast, the forb maintained its biomass by showing strong stability in nutrient content, concentration and stoichiometry. Stability of N uptake and nutrient stoichiometry were associated with higher resistance to soil impoverishment of the forb than the sedge. Our study highlights the importance of stability in nutrient uptake and stoichiometry for determining plant-species resistance to nutrient-poor conditions.

Silicon (Si) accumulation is known to alleviate various biotic and abiotic stressors in plants with potential ecological consequences. However, for dicotyledonous plants our understanding of Si variation remains limited. We conducted a comparative experimental study to investigate (1) interspecific variation of foliar Si concentrations across 37 dicotyledonous forbs of temperate grasslands, (2) intraspecific variation in foliar Si concentration in response to soil Si availability, the influence of (3) phylogenetic relatedness, and (4) habitat association to moisture. Foliar Si differed markedly (approx. 70-fold) across the investigated forbs, with some species exhibiting Si accumulation similar to grasses. Foliar Si increased with soil Si availability, but the response varied across species: species with higher Si accumulation capacity showed a stronger response, indicating that they did not actively upregulate Si uptake under low soil Si availability. Foliar Si showed a pronounced phylogenetic signal, i.e., closely related species exhibited more similar foliar Si concentrations than distantly related species. Significant differences in foliar Si concentration within closely related species pairs nevertheless support that active Si uptake and associated high Si concentrations has evolved multiple times in forbs. Foliar Si was not higher in species associated with drier habitats, implying that in dicotyledonous forbs of temperate grasslands high foliar Si is not an adaptive trait to withstand drought. Our results demonstrated considerable inter- and intraspecific variation in foliar Si concentration in temperate forbs. This variation should have pervasive, but so far understudied, ecological consequences for community composition and functioning of temperate grasslands under land-use and climate change. Supplementary Information The online version contains supplementary material available at 10.1007/s00442-021-04978-9.

Arbuscular mycorrhizal fungi (AMF) represent important players in the structure and function of many ecosystems. Yet, we learn about their roles mostly from greenhouse-based experiments, with results subjected to cultivation bias. This study explores multiple aspects of this bias and separates the effect of increased nutrient availability from other cultivation specifics. For 15 grassland plant species from two functional groups (C3 grasses vs dicotyledonous forbs), we compared AMF communities of adults collected from non-manipulated vegetation with those in plants grown in a greenhouse. Nutrient availability was comparable to field conditions or experimentally elevated. We evaluated changes in AMF community composition, diversity, root colonisation, and the averages of functional traits characterising hyphal soil exploration. Additionally, we use the data from the greenhouse experiment to propose a new plant functional trait-the change of AMF colonisation in response to nutrient surplus. The AMF community differed profoundly between field-collected and greenhouse-grown plants, with a larger change of its composition in grass species, and AMF community composition in grasses also responded more to fertilisation than in forbs. Taxonomic and phylogenetic diversity declined more in forbs under cultivation (particularly with elevated nutrients), because in their roots, the AMF taxa from families other than Glomeraceae largely disappeared. A decline in AMF colonisation was not caused by greenhouse cultivation itself but selectively by the elevation of nutrient availability, particularly in grass host species. We demonstrate that the extent of decrease in AMF colonisation with elevated nutrients is a useful plant functional trait explaining an observed response of the plant community to manipulation.

The aim of the study was to explore whether the encroachment of an East-African savannah ecosystem by the invasive shrub Dichrostachys cinerea L. Wight & Arn has resulted in changes in the Arbuscular Mycorrhizal Fungus (AMF) communities which are associated with roots of the extant herbaceous plant communities. We hypothesized that this could happen either through introducing new AMF taxa, or through inducing changes in the savannah soil environment or plant community composition. We selected five blocks in the savannah plains of the Nech Sar National Park, southern Ethiopia, and in each block, we established nine vegetation plots along a gradient of D. cinerea encroachment. We sampled roots from the encroaching shrub D. cinerea and from three dominant graminoids (Brachiaria deflexa, Chrysopogon plumulosus, Lintonia nutans) and two forbs (Commelina forskaolii, Ruellia prostrata), and used a metagenomics approach to identify the AMF taxa associated with their roots. D. cinerea exhibited higher AMF richness and diversity, and a significantly different AMF community composition, compared with the sampled herbaceous plants in the unencroached plots. Herbaceous plants in sparsely encroached plots harbored a higher AMF diversity as compared to the control plots, while those in densely encroached plots exhibited an intermediate AMF diversity. D. cinerea encroachment, host plant lifeform, soil characteristics and extant herbaceous plant species diversity all affected AMF community composition associated with the herbaceous plant roots. Woody encroachment might have affected AMF communities of the extant herbaceous vegetation in savannah ecosystems both directly, through introducing novel AMF taxa associated with the encroaching shrub species, and indirectly, through encroachment effects on the environment. Restoration of encroached savannahs should therefore take into account the legacy effects of the invader on the microbial communities.

Functional traits are often used to examine ecological patterns and processes. Ontogeny—changes that occur over time as the result of development—generates variation in traits within individual organisms. We aimed to quantify the role of ontogeny in structuring functional trait variation across a range of co-existing herbaceous perennial species and hypothesized that ontogenetic variation in traits would be greater in younger vs. older plants. We grew eight herbaceous perennial forb species common in tallgrass prairies from seed in a greenhouse in Madison, Wisconsin, USA to determine how and when time-related variation in functional traits is large relative to other sources of variation, such as differences between leaves and species. We destructively measured common functional traits on four individuals of each species every two weeks for 19 weeks, including leaf mass fraction, root mass fraction, stem mass fraction, specific leaf area, leaf dry matter content, and leaf area. We found that most functional traits indeed change through time, that the direction of many changes are consistent between species but the magnitude of change is species specific, and most time-related variation occurred earlier in development. These results emphasize the importance of considering sampling timing and differences between young and old plants when measuring functional traits. Our results suggest that ontogenetic intraspecific variation can be substantial, especially early in life. It may be problematic to use traits measured from mature plants to interpret the importance of processes that occur at earlier life stages or vice versa; using seedling traits to understand adult plant responses may also be inappropriate.

With changes in global climate and land use, the area of desertified farmland in southeastern Horqin Sandy Land (HSL) has increased in recent years, and farmlands are being abandoned. These abandoned farmlands (AFs) negatively impact the local ecology. Therefore, the aim of the present study was to select suitable trees and shrubs for those AFs to prevent and control the desertification tendency. In this study, three AFs were fenced for 2 years, then 37 arbor and shrub species or varieties of 21 families were planted in the fenced AFs and grown for 10 years. The ecological adaptability of the species was evaluated and ranked using a principal component analysis. The results showed that the biodiversity of the AFs significantly improved after 2 years of fencing; the Shannon–Wiener index and species richness of perennial grasses and forbs were 1.45 and 3.6 times higher, respectively, than for the unfenced AF. Among all species planted in fenced AFs, nine tree species had positive comprehensive F (CF) values; Pinus sylvestris (Russian Shira steppe provenance), Populus alba ‘Berolinensis’ and Gleditsia triacanthos had CF greater than 1, and the first (PC1), second (PC2) and third (PC3) principal component values (F1, F2, F3) were all positive. Among the shrubs, only Lespedeza bicolor and Rosa xanthina f. normalis had CF greater than 0. All these results suggest that fencing improves biodiversity and that planting trees and shrubs that have higher CF values on the basis of fencing is an effective way to green and beautify AFs in HSL.

Grime’s competition–stress–ruderal (CSR) theory is widely used to study plant species’ responses to multiple environmental factors. We compared two models to allocate CSR types the global “StrateFy” model (Pierce et al. Funct Ecol, 31:444–457, 2017) and a locally developed morpho-physiological model (Novakovskiy et al. Int J Ecol, p e1323614, 2016). The “StrateFy” model is based on three morphological leaf traits: leaf area (LA), leaf dry matter content (LDMC) and specific leaf area (SLA). The morpho-physiological model additionally uses plant height (PH), leaf dry weight (LDW), photosynthetic capacity (PN) and respiration rate (RD), leaf nitrogen, and carbon concentration (LNC, LCC). We applied both models to 74 plant species, the traits of which were measured at mountain (Northern Urals) and plane (Komi Republic, Russia) landscapes of European Northeast. The comparison of the calculated C, S, and R scores showed two groups of species with large and unidirectional differences. The first group consists of species with a shift from S (morpho-physiological model) to CR (StrateFy model) strategy. Species of this group are typical for deep shaded habitats and characterized by low LDMC (10–25%) and high SLA (30–60 mm(2) mg(−1)). The second group consists of C species (morpho-physiological model) which were classified as S (StrateFy model) strategy. This group includes mainly tall shrubs, graminoids, and forbs with relatively small leaves (300–2000 mm(2)). In our opinion, the CSR strategies obtained by the morpho-physiological model showed better agreement with the basic principles underlying Grime's theory. The use of a limited number of morphological traits (LA, LDMC, SLA) in the StrateFy model does not always allow to determine the life strategy correctly. For example, these traits are insufficient for a clear separation of deeply shaded stress-tolerant species and ruderals. On the other hand, the use of the morpho-physiological model requires a large number of field measurements, which makes it difficult to use this model to allocate CSR strategies for a large number of species. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12298-021-00973-9.

Top-down and bottom-up factors affecting invasive populations are rarely considered simultaneously, yet their interactive responses to disturbances and management interventions can be essential to understanding invasion patterns. We evaluated post-fire responses of the exotic perennial forb Chondrilla juncea (rush skeletonweed) and its biocontrol agents to landscape factors and a post-fire combined herbicide (imazapic) and bacteria (Pseudomonas fluorescens strain MB906) treatment that targeted invasive annual grasses in a sagebrush steppe ecosystem. Biocontrol agents released against C. juncea in previous decades included Cystiphora schmidti (gall midge), Aceria chondrillae (gall mite), and Puccinia chondrillina (rust fungus). C. juncea abundance was greater in sprayed than unsprayed plots, and where soils were coarser, slopes faced southwest, solar heat loads and topographic water accumulation were greater, and cover of deep-rooted native perennials was lower. Mite infestation was greater in unsprayed plots, midge infestation was greater at higher elevations on steeper slopes, and midges were more abundant while rust was less abundant on gravelly soils. Biocontrol infestation levels varied considerably between years and could not be predicted in 2019 from 2018 infestation levels. Multiple biocontrol species were often present at the same plots but were rarely present on the same C. juncea individuals. These results suggest that spatial patterns of invasion by C. juncea are related to deep-soil water availability, warmer conditions, and alleviation of competition. Treatments designed to reduce invasive annual grasses may inadvertently release C. juncea by both reducing plant competition for soil resources and affecting biocontrol agent (mite) abundance.

Context Ensembles of artificial neural network models can be trained to predict the continuous characteristics of vegetation such as the foliage cover and species richness of different plant functional groups. Objectives Our first objective was to synthesise existing site-based observations of native plant species to quantify summed percentage foliage cover and species richness within four functional groups and in totality. Secondly, we generated spatially-explicit, continuous, landscape-scale models of these functional groups, accompanied by maps of the model residuals to show uncertainty. Methods Using a case study from New South Wales, Australia, we aggregated floristic observations from 6806 sites into four common plant growth forms (trees, shrubs, grasses and forbs) representing four different functional groups. We coupled these response data with spatially-complete surfaces describing environmental predictors and predictors that reflect landscape-scale disturbance. We predicted the distribution of foliage cover and species richness of these four plant functional groups over 1.5 million hectares. Importantly, we display spatially explicit model residuals so that end-users have a tangible and transparent means of assessing model uncertainty. Results Models of richness generally performed well (R2 0.43–0.63), whereas models of cover were more variable (R2 0.12–0.69). RMSD ranged from 1.42 (tree richness) to 29.86 (total native cover). MAE ranged from 1.0 (tree richness) to 20.73 (total native foliage cover). Conclusions Continuous maps of vegetation attributes can add considerable value to existing maps and models of discrete vegetation classes and provide ecologically informative data to support better decisions across multiple spatial scales.

Climate change and disturbance are two major factors affecting the establishment of invasive species, yet few studies to date have assessed the individual and interactive effects of these two factors in a common setting. Disturbance has often been found to facilitate the establishment of invading species, while climate change may affect them positively or negatively through altering abiotic conditions, or indirectly by modifying species interactions. In a full-factorial field experiment in a semiarid temperate grassland in Central Hungary, we studied the effects of drought (40% rain exclusion throughout the year) and soil disturbance on the emergence, survival and aboveground biomass of four invasive plant species that represent different life forms and that are of concern in the region and at a broader scale. We added seeds of Ambrosia artemisiifolia (annual forb), Cenchrus incertus (annual grass), Asclepias syriaca (perennial forb) and Ailanthus altissima (deciduous tree) in drought and non-drought plots with and without soil disturbance. Ailanthus germinated poorly irrespective of treatments. Disturbance facilitated while drought suppressed seedling emergence in the other three species. Ambrosia was more sensitive to disturbance, while Cenchrus was more responsive to drought. Asclepias achieved substantial emergence in disturbed non-drought plots only, as drought strongly suppressed its emergence even in the presence of disturbance. Seedling survival and late-season aboveground biomass of Ambrosia and Cenchrus were positively affected by disturbance but were unaffected by drought, while no Asclepias seedling survived until late summer. Our results highlight that both drought and disturbance may considerably impact the establishment of invasive plants, with potential interactive effects, but responses may greatly differ among species and life stages. Overall, our findings in this study suggest that although drought may negatively affect seedling establishment, a drier climate may not suppress or eliminate invasive species if soil disturbance is present. They also highlight the importance of including disturbance in studies assessing the potential effects of climate change on plant invasions.

Vineyards can be valuable habitats for biodiversity conservation. For example, in Rhineland-Palatinate (Germany) over a third of the state’s critically endangered Woodlark (Lullula arborea) population breeds in vineyards along the western margin of the Upper Rhine Valley. We here aim to elucidate how local ground cover management, food availability and the proximity to settlements affect territory selection by this bird species in the region. As climate, site conditions and management differ greatly from more continental or Mediterranean wine-growing areas, conditions for Woodlark conservation may differ as well.We compared 26 Woodlark territories in vineyards with 26 nearby reference areas from which Woodlarks were absent. We recorded vineyard ground cover in the inter-rows (% cover) as well as vegetation height and composition (forbs vs. grasses). Arthropods were sampled using pitfall traps, since they are the main food resource of Woodlarks during the breeding season. In addition, the distance to built-up areas was measured. The vegetation in Woodlark territories was shorter (mean 14.2 vs. 19.6 cm) and more dominated by forbs (39% vs. 27% cover) than in absence areas. The vegetation cover in the inter-rows had no effect on Woodlark territory presence or absence. Woodlarks also favoured areas with a higher abundance of arthropods (mean abundance 69.1 vs. 57.5) and a greater distance to built-up areas (mean distance 554 vs. 373 m). We conclude that to promote the Woodlark in wine-growing areas, short, forb-rich swards should be created, facilitating arthropod detectability. This is likely to require low levels of nitrogen fertilization since fertilizers favour tall-growing grasses that outcompete forbs. Pesticide applications should be kept at a minimum to enhance arthropods as the main food source for Woodlarks and their chicks. In addition, the expansion of settlements into breeding areas of Woodlarks should be avoided.

Invasive plants cause changes to native plant communities and nutrient cycling, and by doing so, may alter the amount and quality of habitat available for animals at multiple trophic levels, including arthropods. Arthropods are generally abundant, diverse, and contribute to energy flow and nutrient cycling and are, therefore, an important group to study as a way of determining the effects of changes to ecosystem functioning. Spotted knapweed (Centaurea stoebe L.), a perennial forb native to Eastern Europe, is considered one of the most ecologically harmful invasive species in Western North America. Here, we test if spotted knapweed alters plant community, ground litter and ground temperature, and arthropod functional group structure and biomass in grassland habitats in British Columbia, Canada. Pitfall traps, installed at 20 sites that differed in spotted knapweed density, were sorted into herbivores, omnivores, predators, detritivores, and parasites. Decreases in herbivore and detritivore biomass was associated with increasing spotted knapweed density. The first two coordinates of a Principle Coordinates Analysis explained a cumulative 60% of the variation, and herbivores were separated from predators on both axes. The results suggest that spotted knapweed density may affect arthropod functional groups through changes in plant community composition, and surface soil temperatures. The results suggest that in terms of relative abundance and biomass, increasing knapweed density had positive effects on some arthropod functional groups, neutral effects on others, and negative effects on others. Thus, not all arthropod functional groups responded equally to knapweed invasion, and knapweed invasion does not necessarily decrease arthropod functional group diversity

Declaring the drought-resistance of plant communities in grassland and the underlying mechanisms is crucial under climatic change scenario. Here we aimed to quantify aboveground & belowground net primary productivity (ANPP & BNPP) and their allocation in response to extreme droughts, and to uncover any underlying factors of drought resistance. We experimentally reduced growing season rainfall by 66% for four years in two grassland sites (Sandy and Loamy site respectively), and measured ANPP and BNPP yearly and evaluated the relatedness of drought-induced changes for them to plant traits (Plant height, δ13C, SLA and LNC) and community composition. Experimental drought decreased species richness, ANPP of forbs and the total at both sites, but decreased ANPP of grasses only at the Sandy site. Experimental drought has non-significant effect on total BNPP at both sites, but increased 10–20 cm BNPP and decreased 0–10 cm BNPP. BNPP ratio was kept unchanged at the Loamy site but increased at the Sandy site. Moreover, the communities at the Loamy site showed lower δ13C, SLA and LNC, but greater height. Our study demonstrates that extreme drought can impact community productivity and structure, and highlights the importance of plant traits, community composition and soil properties in modulating the responses and resistance of steppe communities to extreme drought.

We quantified the potential influence of arbuscular mycorrhizal fungi (AMF) on primary productivity and community stability and tested whether the effects of AMF depend on soil phosphorus (P) availability and grazing intensity in a semiarid grassland. We manipulated the abundance of AMF and soil P availability (P addition and no P addition) under four levels of grazing intensity. The aboveground biomass of plant species, functional groups and community, as well as community temporal stability were examined under these conditions. Under no to moderate grazing, benomyl decreased the aboveground biomass in C4 grasses and forbs, but increased the aboveground biomass in C3 grasses under low P conditions; thus no obvious changes in community primary productivity were observed. These results indicated that the mycorrhizal dependency of C4 grasses and forbs is higher than that of C3 grasses under low P conditions. However, community primary productivity was greatly enhanced by benomyl due to the increased biomasses of C3 grasses and forbs under high P conditions. Under heavy grazing conditions, benomyl increased community primary productivity under both low and high P conditions. AMF presence increased the community temporal stability by promoting the compensatory effects between plant species under no to moderate grazing conditions; whereas AMF decreased the community stability by forming a parasitic symbiosis with their plant hosts under heavy grazing conditions. Our findings demonstrate that the effects of benomyl application to suppress AMF on primary productivity and community stability are strongly mediated by soil P availability and grazing intensity, which improves our understanding for the roles of AMF-plant symbiosis on ecosystem functioning in grazed systems.

Nutrient resorption from senescing tissues is the most critical nutrient source for plants in degradation grasslands, playing critical roles to primary productivity and interspecies competitiveness. Hence within-species and among-species variation of nutrient resorption is one of the mechanisms explaining the increasing productivity and decreasing biodiversity after enclosure. Yet, the response of plant nutrient resorption to enclosure remains poorly documented. We conducted a 6-year manipulative field study to estimate the effects of enclosure on nutrient resorption efficiency in five dominant species in a degraded subalpine pasture. Both soil, mature and senesced leaves showed significant increases in N, P, and K contents in response to enclosure. Despite some species-specific differences, enclosure generally increased the nutrient resorption in graminoids, but decreased in forbs (with the exception of phosphorus for Potentilla anserine), indicating an important difference in the adaptation of plant functional types to enclosure which may in turn strongly impact the productivity and structure of pasture vegetation under long-term enclosure. This study shows the positive effects of enclosure management on soil and plant nutrients accumulation, and our results highlight the importance of among-species and within-species variations in plant nutrient resorption to explain the effects of enclosure on biodiversity loss and productivity increase in a degraded ecosystem.

Vein traits influence photosynthesis and drought resistance and are sensitive to climate change. It is unclear whether vein traits, similar to other leaf traits, have obvious regional characteristics and covariance with other leaf traits, especially in Tibetan Plateau grasslands. We collected 66 species from 37 sites in late July of 2012 and early August of 2013 to investigate leaf vein traits and their relationships with other leaf traits in comparison with the available global database data and to elucidate vein investment of plants with different vein types. The average vein length per area (VLA) of plants in the Tibetan Plateau was within the range of the global dataset, and the relationships among vein traits and other leaf traits of alpine plants were consistent with the global models. The VLAs of parallel-veined grasses and pinnate-veined forbs were significantly lower and higher than the global mean value, respectively. The leaf mass per area and total nitrogen content of parallel-veined grasses were significantly lower and higher, respectively, than the global mean values; the opposite was observed in pinnate-veined forbs. The parallel-veined grasses exhibited almost a four-fold higher vein biomass investment (i.e., vein mass per leaf mass) than pinnate-veined forbs in the same region. The average VLA and its relationships with other leaf traits of the alpine grassland plants on the Tibetan Plateau had no regional characteristics, suggesting a convergence in plant leaf functioning. Plants with different leaf types differ in their adaptation strategies to plateau environments, and this may relate to biomass investment into leaf veins. Our study fills the gap with regard to vein density in alpine grassland species and provides a new perspective for understanding plant physiology and ecology by calculating and comparing the proportion of vein investment among different vein types.

The sword lily Gladiolus palustris Gaudin is protected on European level and listed in Annexes II and IV of the EC Habitat Directive 92/43/EEC. It grows in nutrient-poor, calcareous meadows in central and eastern Europe. Tree encroachment in montane meadows of the European Alps as a result of recent land use changes and the abandonment of traditional farming practices threaten the survival of this species. Conservation-driven mowing is considered a feasible conservation measure for maintaining high species diversity in abandoned semi-natural grasslands. To assess the effects of ten years of biennial mowing on a grassland community in the Dolomiti Bellunesi National Park, Italy (Site of Community Importance, Natura 2000 network), ten 25 m2 plots were established whereby four plots were placed in the mowed area, four in the non-mowed area and two in a small non-mowed patch of grassland inside the mowed area. In each plot the following variables were recorded, total percentage of plant cover, percentage cover of woody species, percentage cover of herbaceous species, percentage cover and number of flowering ramets of G. palustris and a complete list of species and their percentage abundance. Mowed plots showed a higher species richness than non-mowed plots. The number of G. palustris flowering ramets and percentage cover increased manifold in mowed plots compared to non-mowed plots. The resumption of mowing for conservation purposes undertaken by the managing authority halted the process of tree encroachment and avoided a drastic change in plant composition. Periodic mowing (every second or third year) was demonstrated to be a cost-effective conservation measure in non-productive grasslands to keep grasses at bay in favour of forbs of high conversation value.

Worldwide, invasive alien plant species (IAS) threaten the biodiversity and the functioning of ecosystems. Most invasion research so far has focused on the properties underlying species invasiveness and community invasibility, yet IAS impact and the underlying causal pathways remain largely unknown. Here we dealt with this knowledge gap by extending the traditional functional trait framework to spectral data, by using traits estimated from reflectance measurements obtained through proximal field spectroscopy, as a surrogate for conventionally measured traits. We focused on two functionally distinct species that are invasive in Belgium: the annual forb Impatiens glandulifera Royle, and the rhizomatous perennial forb Solidago gigantea Ait. By means of trait-based linear mixed models and structural equation models we studied their impact on six ecosystem functions involved in the cycling of carbon and nutrients, and the mechanisms mediating these changes. Analyses based on either conventionally or optically measured traits revealed similar results: the IAS altered aboveground biomass (decrease and increase under I. glandulifera and S. gigantea respectively), litter stabilization (decrease under both IAS) and soil available phosphorus (increase under both IAS) through mass ratio effects, rather than through decreasing the functional diversity of the community. Whereas S. gigantea did so by shifting the community towards more conservative traits, I. glandulifera achieved this by making the community taller and richer in leaf nutrients. The use of remote sensing through optically measured traits, is not only useful to advance our understanding of the mechanisms and consequences of plant invasion, but may also be valuable to the broader field linking plant community composition to ecosystem functioning. Its potential for studying larger spatial scales over time may contribute to even more comprehensive insights.

Overyielding, the primary metric for assessing biodiversity effects on ecosystem functions, is often partitioned into “complementarity” and “selection” components, but this reveals nothing about the role of increased resource use, resource-use efficiency, or trait plasticity. We obtained multiple overyielding values by comparing productivity in a five-species mixture to expected values from its component monocultures at a) six levels of nitrogen addition (spanning 0–500 kg N ha–1 year–1) and b) across four seasons. We also measured light, water, and nitrogen use, resource-use efficiency, and three functional traits—leaf nitrogen content, specific leaf area, and leaf area ratio—n mixtures and monocultures. We found strong evidence for non-transgressive overyielding. This was strongest in spring, with mixture productivity exceeding expected values by 20 kg dry matter ha–1 day–1. Peak overyielding was driven by enhanced complementarity, with the two non-N2-fixing forb species far exceeding expected productivity in mixtures. Peak overyielding also coincided with higher water use in the mixture than for any monoculture, and enhanced mixture-resource-use efficiency. There was only weak evidence that trait plasticity influenced overyielding or resource use. Our findings suggest that when complementarity drives overyielding in grassland mixtures, and this is made possible both by increased water use and enhanced efficiency in water, nitrogen, and light use. Our results also suggest that mixtures offer a viable compromise between productivity, resource-use efficiency, and reduced environmental impacts (i.e., nitrate leaching) from intensive agriculture.

Context Intact tropical rainforests are considered robust to plant invasions. However, land-use change alters the structure and species composition of native forest, opening up tropical landscapes to invasion. Yet, the relative roles of key drivers on tropical forest invasions remain little investigated. Objectives We examine factors affecting plant invasion of rainforest remnants in oil-palm dominated landscapes in Sabah, Malaysian Borneo. We hypothesized that invasion is greater in highly fragmented landscapes, and in disturbed forests with lower native plant diversity (cf. old-growth rainforests). Methods Native and exotic plants were surveyed in 47 plots at 17 forest sites, spanning gradients in landscape-scale fragmentation and local forest disturbance. Using partial least squares path-modelling, we examined correlations between invasion, fragmentation, forest disturbance, propagule pressure, soil characteristics and native plant community. Results We recorded 6999 individuals from 329 genera in total, including eight exotic species (0–51% of individuals/plot, median = 1.4%) representing shrubs, forbs, graminoids and climbers. The best model (R2 = 0.343) revealed that invasion was correlated with disturbance and propagule pressure (high prevalence of exotic species in plantation matrix), the latter being driven by greater fragmentation of the landscape. Our models revealed a significant negative correlation between invasion and native tree seedlings and sapling community diversity. Conclusions Increasing landscape fragmentation promotes exotic plant invasion in remnant tropical forests, especially if local disturbance is high. The association between exotic species invasion and young native tree community may have impacts for regeneration given that fragmentation is predicted to increase and so plant invasion may become more prevalent.

Lawns provide green infrastructure and ecosystem services for anthropized areas. They have a strong impact on the environment in terms of inputs (water and fertilizers) and maintenance. The use of warm-season grasses, such as Cynodon dactylon (L.) Pers., provides a cost-effective and sustainable lawn in the dry summers of the Mediterranean. In winter, Bermudagrass is dormant and brown, which instead of being a problem could be an opportunity for biodiversity through the coexistence of flowering species. This study assesses the possibility of growing autumn-to-spring-flowering bulbs and forbs with Bermudagrass, to provide ecosystem services in urban areas. Eight geophytes and 18 forbs were incorporated into a mature turf of hybrid Bermudagrass, Cynodon dactylon × C. transvaalensis cv. “Tifway”. At the same time, a commercial flowering mix was sown in the same conditions. Two different soil preparations, scalping and turf flaming, and two different nitrogen doses, 50 and 150 kg ha−1, were carried out before sowing and transplanting. The flowering plants were counted. All the bulbs and six of the 18 forbs were able to grow and flower in the first and second years. The commercial mix was in full bloom from April until the cutting time for the hybrid Bermudagrass, at the end of May. Adding the flowering species did not affect the healthy growth of the warm-season grass. The fertilization dose had no effect, while turf flaming led to a wider spread of Bellis perennis L. and Crocus spp. Several flower-visiting insects were observed in the spring.

During environmental change, invasive species may be favored by increased resource input or reduced resource use of the resident community. Plasticity in certain plant traits of invasive species may be one possible mechanism behind their ability to quickly exploit unused resources. We tested whether rainfall manipulations (severe drought, moderate drought, watering) alter the growth and reproductive success of the invasive annual Conyza canadensis, and if it translates into a change in the abundance of the species in a semiarid perennial grassland in Central Hungary. Overall, C. canadensis exhibited greater individual performance and higher abundance in drought plots than in control and watered plots. At individual level, plants showed the strongest response to moderate drought: they grew 2.5-times taller than in control and watered plots, and produced twice and 2.5-times more seeds than in watered and control plots, respectively. Reproductive phenology was advanced in response to rain exclusions. Although severe drought caused 40% mortality, the cumulative performance of C. canadensis, expressed as plot-level aboveground biomass, was consistently greater in severe drought plots than in control and watered plots throughout the 3 years of the study. The higher performance of C. canadensis in drought plots is most likely due to the decreased abundance and, thus, decreased competitive effect of previously dominant perennial grasses caused by the rain exclusions. We conclude that drier summers that suppress perennial grasses will favor this alien annual forb, and phenotypic plasticity in growth and reproduction may contribute to its invasion success. Electronic supplementary material The online version of this article (10.1007/s00442-020-04711-y) contains supplementary material, which is available to authorized users.

Spontaneous plant communities found in abandoned post-industrial landscapes develop in unique conditions which can create novel community assemblages. We examined changes in plant community composition and its relation to soil properties in an urban brownfield more than 40 years following site abandonment to better understand the community’s long-term trajectory. A former railyard and industrial area built on fill material, the study site includes four primary habitat types: grasslands, perennial forb assemblages, shrubland, and early successional forest. Plant species cover was measured in permanent plots in 2008 and 2016/17. In 2008, soil samples were collected and analyzed for a suite of properties. Species richness and Shannon diversity increased across the site from 2008 to 2016 (40 and 48 years post-abandonment) though increases in these parameters were highest in plots with lower metal concentrations. Evenness changed little in this time period. Percent cover of woody species increased in grassland and forb plots while percent cover of vines increased across all habitat types. Forb species tended to be associated with higher nutrient concentrations while woody species distribution was correlated with higher concentrations of heavy metals. The mitigation of soil stress, limitations in propagule availability, and loss of tree canopy cover following disturbances may have all played a role in influencing increases in diversity in this time period. Considering difficulties in comparing post-industrial abandoned landscapes to other anthropogenic and natural habitats, long-term study is needed to refine our understanding of community assembly in urban brownfields and better guide management practices.

Plants often exhibit positive responses to multiple nutrient additions, but generalities about the life form and traits of the most responsive species are few. Findings from long-term experiments in dry meadow alpine tundra in Colorado, USA, were used here to examine univariate and multivariate analyses of plant and plant trait responses. We found transient responses for community richness–biomass relationships, but a consistent increase in forb dominance in nitrogen (N) and phosphorus (P) addition plots. The response seen in the N + P plots was not affected by additions of micronutrients or potassium. Multivariate analyses corroborate transient responses in community shifts over shorter-time scales, and directional shifts in N + P over two decades. Using species-level aboveground trait data when available, we found N + P may favor species with resource-acquisitive traits, regardless of their lifeform, as well as relatively tall grasses, regardless of their resource strategy. In the absence of N and P limitation but with the environmental constraints found in dry alpine meadows, plant richness and community structure continued to exhibit transient states for decadal time frames.

Floral volatile organic compounds (VOCs) are traits that influence plant interactions with pollinators and other species. Interspecific and intraspecific variation in traits can strongly influence community and ecosystem processes. Yet, we lack an understanding of patterns of variation in floral VOCs among individuals of a species and across species at the community-level across years, and the degree to which phylogenetic relatedness among species influences these patterns. Such an understanding is crucial to accurately interpret more complex patterns and predict consequences for pollination services and plant reproduction. We measured floral VOCs within forb populations and across forb species in a subalpine meadow in the Northern Rocky Mountains of USA over 3 years. Forb species varied in their per-flower VOC emissions as well as in the composition, originality (distance from community mean) and uniqueness (distance from nearest neighbor) of their floral VOCs. The originality of a species’ floral VOCs tended to be more consistent through time than uniqueness. Although not related to phylogeny, there were species-specific differences in originality and uniqueness which may reflect responses of forbs to differences in environmental conditions among years. Interestingly, while species harbored different amounts of intraspecific variation (dispersion) in floral VOCs, species were relatively consistent in this variation across years, and there was significant phylogenetic signal in intraspecific variation. The implications of this temporal consistency for plant–pollinator interactions deserve further attention. Investigating links between interspecific and intraspecific variation in floral VOCs with pollination services and plant reproductive success will help establish the consequences of variation in this important trait.

Vacant spaces, such as unplanted, unmanaged, or infrequently accessed green roofs, may play a critical role in sustaining biodiversity in cities. Initial plant composition of these spaces likely is contingent on seed dispersal and growing medium, yet no studies have directly characterized the effects of location or growing medium depth on plant diversity of unplanted green roofs. To address this gap, we studied first-year community composition of five unplanted green roofs in New York City (NY, USA). On each roof, 12 plots were established with media depths ranging from 5 to 13 cm. Four months after installation, all plants were harvested. We observed 29 species across locations; five species were found on all five roofs, while 13 species each were observed on a single roof. Introduced species accounted for 14 of the 29 species found across roofs. Species richness and composition differed among roofs, while functional richness varied within, but not among, roofs. About 80% of the variation in species richness was accounted for by total green space in the neighborhoods within 100 to 200 m of each roof. Functional richness and plant cover increased with increased growing medium depth, as did the relative abundance of annual and forb species. Our results suggest both location and growing medium depth will affect initial community composition of unmanaged green roofs, but with differential effects on community assembly. These results also highlight the potential role of unmanaged vacant roofs as reservoirs of plant diversity, both native and invasive, in urban spaces.

Non-native plant invasions are often catalyzed by wildfires and may alter the structure, function, and composition of ecosystems. Of particular concern are non-native annual grasses that promote increased fire frequency and compete with native vegetation for early season moisture. While these effects are well studied in non-forested ecosystems, relatively few studies document invasions of non-native annual grasses in forested ecosystems. We document non-native plant invasion following repeated high-severity wildfire in mixed-conifer/hardwood forests dominated by Douglas-fir (Pseudotsuga menziesii) in the Klamath Mountains of northern California. Despite great concern regarding the loss of conifer dominance and transitions to non-forested states related to recent and projected increases in wildfire activity, there is little known about invasions of non-native plant species following fire in this region. Non-native plant species capable of long-distance dispersal had an average total cover of 26% and were ubiquitous across a systematic, gridded sample of twenty 800 m2 plots. Non-native forbs included multiple species of common post-disturbance invaders (e.g. Cirsium vulgare, Senecio sylvaticus, Lactuca serriola). Non-native annual grasses comprised more of the vegetative cover than non-native forbs (17% vs. 9%), and were dominated by two species, Aira caryophyllea and Vulpia myuros, which reached as high as 80% cover. Our findings indicate that non-native annual grasses are a novel stressor that may accelerate projected loss of conifer dominance in the Klamath Mountains by facilitating fire spread and increasing competition for early season soil moisture. Additional monitoring will be crucial to understanding the impacts of non-native plants as fire activity in this region continues to increase.

Aims Saprophytic fungi are important agents of soil mineralization and carbon cycling. Their community structure is known to be affected by soil conditions such as organic matter and pH. However, the effect of plant species, whose roots provide the litter input into the soil, on the saprophytic fungal community is largely unknown. Methods We examined the saprophytic fungi in a grassland biodiversity experiment with eight plant species belonging to two functional groups (grasses and forbs), combining DNA extraction from plant roots, next-generation sequencing and literature research. Results We found that saprophyte richness increased with plant species richness, but plant functional group richness was the best predictor. Plant functional group was also the main factor driving fungal saprophytic community structure. This effect was correlated with differences in root lignin content and C:N ratio between grasses and forbs. In monocultures, root traits and plant functional group type explained 16% of the variation in community structure. The saprophyte taxa detected in mixed plant communities were to a large extent subsets of those found in monocultures. Conclusions Our work shows that the richness and community structure of the root-associated saprophytic fungi can largely be predicted by plant functional groups and their associated root traits. This means that the effects of plant diversity on ecosystem functions such as litter decomposition may also be predictable using information on plant functional groups in grasslands.

Fire is a natural disturbance occurring every few years in many grasslands ecosystems. However, since European colonization, fire has been highly reduced or even suppressed in Argentinean grasslands, fostering ignitable material accumulation. This has led to occasional catastrophic control-demanding fire events, extended for larger areas. The aims of this work are to study vegetation recovery and change after a non-natural fire event in mountain grasslands. The study area is located in the Ventania mountain system, mid-eastern Argentina. We studied vegetation recovery after fire (January 2014) in two different communities: grass-steppes (grasslands) and shrub-steppes (open low shrublands). We measured vegetation cover, species richness and bare ground percentage in burned and unburned areas 1, 4, 8, 11 and 23 months after fire. Vegetation surveys were also performed at the end of the growing season (December) 11 and 23 months after fire. Data were analyzed using regression analysis, ANOVA and multivariate analysis (NMS, PERMANOVA). Both communities increased their vegetation cover at the same rate, without differences between burned and unburned areas after two years. Species richness was higher in shrublands and their recovery was also faster than in grasslands. Considering functional composition, besides transient changes during the first year after fire, there were no differences in abundance of different functional vegetation groups two years after fire. At the same time, shrublands showed no differences in species composition, while grasslands had a different species composition in burned and unburned plots. Also, burned grassland showed a higher species richness than unburned grassland. Data shown mountain vegetation in Pampas grassland is adapted to fire, recovering cover and richness rapidly after fire and thus reducing soil erosion risks. Vegetation in mountain Pampas seems to be well adapted to fire, but in grasslands species composition has changed due to fire. Nonetheless, these changes seem to be not permanent since pre-fire species are still present in the area. Fil: Loydi, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; Argentina Fil: Funk, Flavia Alejandra. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina Fil: García, Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina

Leafhoppers (Hemiptera: Cicadellidae) form a large, diverse insect family that contributes significantly to trophic interactions and pathogen transmission in grasslands. We compared leafhopper communities of five remnant prairies and five prairie reconstructions in northeastern Kansas, USA. We hypothesized that leafhopper communities would be more conservative (i.e., greater dependence on prairies) and diverse on remnant as compared to reconstructed prairies, and that remnants would support more grass-feeders. We also predicted that sites surrounded by natural/semi-natural landscapes would have greater leafhopper diversity. We found grass feeders represented a higher proportion of leafhoppers on remnants. We found, however, no difference in mean conservatism between remnants and reconstructions, and overall levels of conservatism were lower than other grassland data sets. Mean conservatism was greater in the mid-summer than in early summer, where migratory pests such as Macrosteles were abundant. Although remnants and reconstructed prairies didn’t differ in leafhopper diversity, diversity increased with forb percent cover. The amount of natural and semi-natural land cover around sites had complex relationships with leafhopper diversity and composition. For future studies, we encourage coordinated studies on leafhopper communities across the tallgrass prairie region, with a particular focus on conservatism. Deciphering the effect of survey times, and grassland size and management, on prairie-dependent leafhoppers is important. We predict that large numbers of migratory species may lead to greater homogeneity in leafhopper communities across sites early in the season. Over time, site types and landscape features may progressively filter species and amplify local specialists, resulting in more late-season variation among sites.

Background Over the last century, fire exclusion has caused dramatic structural and compositional changes to southern New England forests, highlighting the need to reintroduce fires into the historically pyrogenic landscape to study the response. We investigated the effects of a single overstory thinning and midstory removal to create an open oak-hickory woodland structure, followed by repeated prescribed burns. We hypothesized that burning would create greater floristic diversity comprising fire-tolerant woody regeneration and shade-intolerant herbaceous flora. We followed shifts in plant structure, composition, and diversity over a 23-year period, using a before-after-control-impact design with data collected once prior to burning and twice after burn treatments had begun and with soil samples collected after nearly 20 years of burning. Results We observed a dense ingrowth of saplings on unburned plots that were largely absent from burned plots and a shift in midstory composition to favor mesic sweet birch (Betula lenta L.) in the unburned treatment, as opposed to the hickories (Carya Nutt. spp.) and oaks (Quercus L. spp.) that dominated the burned treatment. Burning resulted in a significantly greater density, richness, Shannon diversity, and evenness of understory vegetation (forbs, shrubs, tree seedlings). These four measures remained high on burned plots, despite a decrease in both floristic diversity and evenness on unburned plots and a reduction in unburned site-level richness. Understory composition varied significantly by year and burn treatment, with unburned plots largely characterized by shade-tolerant species while burned plots showed an enhanced abundance of heliophilic plants. Conclusions Our results suggest that periodic burning increases nutrient microsite heterogeneity and periodically maintains greater understory light, both of which in turn increase understory plant density and diversity and cause a shift in understory composition. This study shows that repeated prescribed burns in an open New England woodland have lasting structural and compositional effects capable of restoring pre-settlement, pyrogenic vegetation patterns.

Studying the effects of fertilisation on the seed production of grassland species can help understand the vegetation changes and biodiversity losses due to soil eutrophication. The seed production of fifteen grasses and seventeen forbs from a temperate hay meadow was studied under three fertilisation treatments: 0-0-0, 0-54-108 and 192-108-216 kg N, P2O5 and K2O respectively, per year. Fertile shoots collected at the seed maturation stage were analysed for all main traits of the gamic reproduction. On average, forbs produced more ovules and viable seeds per shoot (199 and 65, respectively) than grasses (112 and 35, respectively). Fertilisation increased the number of inflorescences per shoot in both grasses and forbs and had a limited but variable effect on germinability and viability in the two functional groups: viability increased in grasses but often decreased in forbs. This pattern resulted in 55% and 11% increases in viable seed production in grasses and forbs, respectively. At the higher level of fertilisation, shoot density was positively related to the number of viable seeds per shoot in grasses and to the seed size in forbs. These results highlight that the traits of the gamic reproduction can contribute to explain the relationship between soil nutrient richness and grassland species composition and richness.

Drastic seasonal changes in higher latitudes and altitudes impact the phenology of plant growth forms differently and thus diet of ungulates feeding on them. We examined how fecal nitrogen (N), an indicator of diet quality, varied with season against the background variation in forage biomass and N in habitats of two sympatric ungulates in subtropical Himalaya. We conducted this study in Kyongnosla Alpine Sanctuary, Sikkim, where the Himalayan goral Naemorhedus goral occurred from 3000 to 3600 m and Himalayan musk deer Moschus chrysogaster from 3300 to 4200 m. We measured biomass and N content of forbs and graminoids and browse in their habitats and proportions of monocots and dicots and N content in their fecal pellets. Seasonal variation in biomass, primarily determined by forbs, was similar in goral and musk deer habitats. Goral had a graminoid-dominated diet switching to dicots in autumn and winter. Musk deer had a dicot-dominated diet in all seasons. Fecal N in both the ungulates was higher than forage N in all seasons except spring when the latter was greater. Forage and fecal N declined sharply from spring as seasons progressed. Fecal N in goral was considerably lower than in musk deer in all seasons, probably below maintenance levels in autumn and winter. As evident from peaks and duration of high diet quality, goral is likely a capital breeder and musk deer an income breeder. Results suggest that linkages between diet and reproductive seasonality in ungulates will have important implications in face of climate change.

In Australia, the regulatory framework for assessing the risk of soil contamination assumes there is minimal risk from the natural enrichment of potentially toxic elements in soil. When this assumption is applied to land cleared for anthropogenic purposes, non-adapted biota including humans, domestic animals and garden plants can be exposed to these soils. While the impacts of natural arsenic (As) and fluorine (F) in waterways are widely reported, little is known about the biological impacts of natural As and F in non-aquatic soils. We investigated four field sites with naturally elevated soil As and F around Melbourne, Australia. All sites were assessed for As and F in soil, tree and herb (grasses and forbs) foliage. Soil concentrations of As and F ranged from near to above mean ambient background concentrations for Victoria. Soil As and F under trees were consistently higher than under herbs, suggesting deeper tree roots resulted in translocation and accumulation of As and F from deeper soil layers. While surface soil enrichment by plants is known for nutrients, there is less information about enrichment of potentially toxic elements. No clear relationships between soil and foliar As/F concentrations were found. However, there was a range of As and F accumulations in foliage across the four sites: from low to concentrations representative of contaminated sites and above regulatory guidelines. We demonstrated that soils naturally enriched in As and F can be bioavailable and accumulated in plant foliage. Thus, we suggest reassessment of the assumption in Australian guidance that naturally elevated concentrations of potentially toxic elements are not bioavailable and pose minimal risk.

Pollination is an ecosystem service that is in jeopardy globally. Decreasing trends in wild pollinator populations are primarily attributed to habitat loss and degradation. These concerns are especially apparent in the Rainwater Basin of Nebraska, USA where more than 90% of the land has been cultivated and 90% of the wetlands have been lost. We compared hymenopteran and dipteran pollinator abundance, richness, and diversity in 28 wetlands and their adjacent uplands within 3 dominant land-condition types: cropped, restored, and reference state. We used vane traps to capture local pollinator insects and sweep nets to collect insect pollinators on flowers. Vane-trap captures revealed a greater abundance, richness, and diversity of hymenopteran pollinators in uplands as compared to wetlands over the entire growing season in all land-condition types. However, net collections showed that hymenopterans foraged more in wetlands than in uplands, especially in restored wetlands. The exception was September when hymenopterans were captured in uplands more than wetlands while feeding on late season forbs. Dipteran vane-trap and sweep-net captures primarily consisted of hoverflies (Syrphidae). Hoverflies were more abundant in wetlands than uplands. All pollinators used both wetlands and uplands for resources. Thus, insect-pollinator conservation can be enhanced by promoting native forb communities and pollinator habitat through wetland restoration and the planting of buffer strips.

Invasion by exotic plant species can profoundly affect native plant species performance and the inferred proximate cause is typically competition. We used invaded grasslands in the semi-arid Western USA to separate resource competition from structural interference of an exotic grass on native forb performance, specifically evaluating the role of competition from living vegetation versus litter accumulation (hereafter, thatch). We simultaneously tested whether a positive thatch-feedback exists for the dominant exotic grass species, Bromus diandrus. Thatch and B. diandrus density were manipulated and coupled with native seed addition to separate the effect of B. diandrus competition relative to thatch accumulation. To determine the response of native forb species and B. diandrus to varying thatch abundance, we created a gradient of thatch densities and measured species response, soil moisture and light availability. The thatch of B. diandrus greatly reduced native forb performance (number of individuals and biomass) and resulted in near complete exclusion of many species. The effect of living B. diandrus density on native forb performance was minimal and inconsistent. Forb performance and light availability both exhibited exponential declines with thatch build-up suggesting that light reduction is a primary mechanism through which thatch affects forbs. Simultaneous with forb suppression, B. diandrus performance was positively affected by thatch, consistent with a positive feedback initiated by invasion of this species. Our results demonstrate that thatch accumulation, rather than competition for resources, is the primary cause of native species decline in grasslands invaded by this exotic annual grass. In addition, the dominance of B. diandrus in many invaded grasslands may be reinforced through a positive thatch-feedback and require active management, such as grazing or fire, to be broken.

Coastal sandplains provide habitat for a suite of rare and endangered plant and wildlife species in the northeastern United States. These early successional plant communities were maintained by natural and anthropogenic disturbances including salt spray, fire, and livestock grazing, but over the last 150 years, a decrease in anthropogenic disturbance frequency and intensity has resulted in a shift towards woody shrub dominance at the expense of herbaceous taxa. This study quantified the effects of more than a decade of dormant season disturbance-based vegetation management (mowing and prescribed fire) on coastal sandplain plant community composition on Nantucket Island, Massachusetts, USA. We used time-series plant cover data from two similar sites to evaluate the effectiveness of disturbance management for restoring herbaceous species cover and reducing woody shrub dominance. Our results indicate that applying management outside of the peak of the growing season has not been effective in maintaining or increasing the cover of herbaceous species. While management activities resulted in significant (P

Grasslands and grassy woodlands worldwide have experienced declines in extent and condition, with substantial changes to their ground-layer biodiversity. In Australia, this decline has coincided with the extinction of many digging mammals that may have once created regeneration niches for native ground layer plants. These digging mammals are widely recognised as ‘ecosystem engineers’, due to their influence on biopedturbation and resultant soil functions. Yet there is uncertainty as to the benefits of digging in restoring grassland diversity with current levels of modification and the presence of exotic plants. We investigated the effect of digging by the reintroduced eastern bettong (Bettongia gaimardi) on seedling germination in a temperate grassy woodland in south-eastern Australia. We marked fresh bettong foraging pits and undisturbed control plots in dense and open grassland. We added seeds of seven native forb species and monitored germination and establishment over 2 years. We found significantly more seedlings in bettong pits than controls, particularly in dense grassland. This effect persisted beyond 1 year, suggesting that pits may have increased seedling survival in dry conditions. Surprisingly, native species displayed a stronger positive response to pits than exotic species, particularly in a wet year. There was an initial reduction in exotic species, but this was followed by their increase in 1-year-old pits, suggesting that the disturbance created by digging could eventually lead to an increase in weed abundance. Our results demonstrate that while bettong pits provide a germination niche for native forbs, reintroducing digging animals will not necessarily result in the desired restoration outcomes. Ongoing persistence of exotic species is to be expected, and seed addition may be required for species that are seed-limited.

Fossorial rodents are recognized as diversity drivers in grassland ecosystems and are therefore considered ecosystem engineers and keystone species. However, there is a lack of evidence regarding this function for species in temperate grasslands, especially one of the most threatened, the European ground squirrel. We examined the effect of the European ground squirrel on plant species composition and diversity along the disturbance gradient mediated by their different population density and subsequently different disturbance intensity. We evaluated the effect of ground squirrel disturbance on plant diversity patterns in two plant communities with different species richness to determine whether the same pattern exists in contrasting habitats. In each plant community, we established transect of 25 × 250 m composed of 10 quadrats with different disturbance intensities of the ground squirrels. Vascular plant species were recorded in 320 plots of 1 m2. The distribution of individual species along the ground squirrel-mediated disturbance gradient was analysed using redundancy analysis. Diversity measures were calculated and modelled as a function of disturbances using generalized additive models. We observed significant compositional changes in plant communities accompanied by a reduction in dominant graminoid cover and a non-decreasing trend in forb cover along the disturbance gradient in both types of communities. We found that increasing disturbance activity leads to an increase in diversity at coarse spatial scale (625 m2) and spatial heterogeneity in species composition of both species-poor and species-rich plant community. The fine-scale (1 m2) diversity increased significantly only in species-poor community. Our results demonstrate that the European ground squirrel can be deservedly labelled as an important ecosystem engineer and keystone species promoting the diversity and heterogeneity of European temperate grasslands.

Disturbance regimes are changing rapidly, along with the generation of patchy habitats, and the consequences of such changes for ecosystems will be profound. Plateau zokor mounds are a common natural disturbance on the Tibetan Plateau, and this disturbance leads to bare patches, and catalyse new paradigms of plant community dynamics in alpine ecosystems. We investigated, over 6 consecutive years, the dynamic changes of new zokor mounds, the effects of different zokor mound densities on plant diversity in alpine meadows at the spatial scale, and successional shifts in plant community on the bare mound patches at the temporal scale. The results showed that as the mound density increased, the species diversity and biomass of the plant communities (within mound-free regions between the mounds) significantly increased. Zokor mounds representing different successional stages comprise a mosaic and together constitute the alpine meadow. The cycle of plant succession on the bare mounds is about 6 years in length. The pioneer species were mainly rhizomatous grasses and broadleaf forbs. As succession progressed, the dominant species differed among the different mound patches. However, at the end of succession, the dominant species were grasses, and the species compositions were similar in the communities. The plant succession on the bare mound patches of the alpine meadow is a developmental process from founder-controlled to dominance-controlled communities. The coupling between patch-to-patch mosaic on different phases and year-to-year succession on bare mound patches is very important for species coexistence and promotes alpine meadow renewal.

Changing precipitation regimes can profoundly affect plant growth in terrestrial ecosystems, especially in arid and semi-arid regions. However, how changing precipitation, especially extreme precipitation events, alters plant diversity and community composition is still poorly understood. A 3-year field manipulative experiment with seven precipitation treatments, including - 60%, - 40%, - 20%, 0% (as a control), + 20%, + 40%, and + 60% of ambient growing-season precipitation, was conducted in a semi-arid steppe in the Mongolian Plateau. Results showed total plant community cover and forb cover were enhanced with increased precipitation and reduced under decreased precipitation, whereas grass cover was suppressed under the - 60% treatment only. Plant community and grass species richness were reduced by the - 60% treatment only. Moreover, our results demonstrated that total plant community cover was more sensitive to decreased than increased precipitation under normal and extreme precipitation change, and species richness was more sensitive to decreased than increased precipitation under extreme precipitation change. The community composition and low field water holding capacity may drive this asymmetric response. Accumulated changes in community cover may eventually lead to changes in species richness. However, compared to control, Shannon-Weiner index (H) did not respond to any precipitation treatment, and Pielou's evenness index (E) was reduced under the + 60% treatment across the 3 year, but not in each year. Thus, the findings suggest that plant biodiversity in the semi-arid steppe may have a strong resistance to precipitation pattern changes through adjusting its composition in a short term.

Plant-microbe interactions are crucial components of ecosystem development but are understudied during early succession. The goal of this study was to investigate species-specific effects of plants on unvegetated soils being colonized by plants as climate changes, and assess how plant-soil feedbacks influence plant succession. We used lab and field litter additions in an early successional unvegetated ecosystem in the Front Range of the Colorado Rocky Mountains to examine litter-driven changes in soil bacterial and fungal communities. We then used plant litter-trained soil as inocula in a greenhouse experiment to test plant-soil feedbacks. We found species-specific effects of litter additions on bacterial and fungal communities in unvegetated soils, which are likely due to both differences in tissue litter chemistry and differences in the litter microbiome. We identified a negative effect of soil trained by litter from the conservative forb Silene acaulis on the growth of the fast-growing bunchgrass Deschampsia cespitosa, likely due to changes in microbial communities that resulted in lowered nitrification rates or to a litter-driven increase in N-immobilization. Our study demonstrates the importance of plant specificity and potential negative litter-driven feedbacks in primary succession, which could lead to patchy distribution of plant colonists as climate change allows colonization of these areas.

Net primary production (NPP) is an indicator of rangeland ecosystem function. This research assessed the potential of the Carnegie Ames Stanford Approach (CASA) model for estimating NPP and its spatial and temporal changes in semi-arid rangelands of Semirom County, Iran. Using CASA model, we estimated the NPP values based on monthly climate data and the normalized difference vegetation index (NDVI) obtained from the MODIS sensor. Regression analysis was then applied to compare the estimated production data with observed production data. The spatial and temporal changes in NPP and light utilization efficiency (LUE) were investigated in different rangeland vegetation types. The standardized precipitation index (SPI) was also calculated at different time scales and the correlation of SPI with NPP changes was determined. The results indicated that the estimated NPP values varied from 0.00 to 74.48 g C/(m2·a). The observed and estimated NPP values had different correlations, depending on rangeland conditions and vegetation types. The highest and lowest correlations were respectively observed in Astragalus spp.-Agropyron spp. rangeland (R2=0.75) with good condition and Gundelia spp.-Cousinia spp. rangeland (R2=0.36) with poor and very poor conditions. The maximum and minimum LUE values were found in Astragalus spp.-Agropyron spp. rangeland (0.117 g C/MJ) with good condition and annual grasses-annual forbs rangeland (0.010 g C/MJ), respectively. According to the correlations between SPI and NPP changes, the effects of drought periods on NPP depended on vegetation types and rangeland conditions. Annual plants had the highest drought sensitivity while shrubs exhibited the lowest drought sensitivity. The positive effects of wet periods on NPP were less evident in degraded areas where the destructive effects of drought were more prominent. Therefore, determining vegetation types and rangeland conditions is essential in NPP estimation. The findings of this study confirmed the potential of the CASA for estimating rangeland production. Therefore, the model output maps can be used to evaluate, monitor and optimize rangeland management in semi-arid rangelands of Iran where MODIS NPP products are not available.

Variations in plant nitrogen (N) and phosphorus (P) concentrations and ratios have great implications for primary productivity and nutrient cycling. Here, we reported their changes at functional group and community levels along an aridity gradient. We carried out a field investigation and set up 26 sampling sites along a transect in the drylands of northern China to examine the responses of plant nutrient status to increasing aridity and the relationships between plant and soil nutrients. The responses of N and P concentrations to increasing aridity differed between woody (sub-) shrubs and herbaceous species (including annual/biennial forbs and grasses, perennial forbs and perennial grasses). Nitrogen and P concentrations of shrubs decreased while those of herbs generally increased with increasing aridity. Plant N:P ratios increased significantly with increasing aridity for the plant functional groups and at the community level. At both organizational levels, nutrient concentrations in plants were negatively related to those in soils. Our results indicated that the responses of plant nutrition to aridity were dependent on plant functional group. Plant growth appeared increasingly limited by P, and plant and soil nutrients become increasingly decoupled at large spatial scale with increasing aridity.

Nothofagus antarctica forests at the Chilean Patagonia are valued for both their ecological and livestock production value. Despite their importance, there is not enough information about the understory associated to these forests. Previous studies have reported the dependence of the understory on the light intensity reaching the sward. Thus, our objective was to study the effect of the tree canopy cover on the plant community composition and productivity of the forests´ understory. We established four experimental sites along a 100-km transect covering an area of 700 km2 in Southern Chilean Patagonia. 73 1-m2 metal exclusion cages (quadrats) were randomly distributed along tree cover gradients on the sites. Bare soil, litter and understory cover were registered. Plant botanical composition was also recorded. At the end of the growing season plant biomass was harvested to estimate yield. Species frequency and abundance were analyzed. Species richness and biodiversity were determined. We found 37 species distributed in 20 families. Woody species represented 13.5%, grasses 24.3% and forbs 62.2% of the total. Species richness was higher in grasslands than forests. There was a trend in decreasing biodiversity when increasing tree canopy cover. Differences in yield between grasslands and open forests were not significant. High forage value species presented higher abundance in open forests than grasslands. We conclude that open forests of N. antarctica have higher grazing potential than their associated grasslands. These findings support the facilitation effect of trees over understory species reported previously.

Exotic species are often predicted to successfully invade when their functional traits differ from species in recipient communities. Many studies have related trait differences among natives and invaders to competitive outcomes. Few studies, however, have tested whether functionally similar invaders have similar competitive impacts on natives. We investigated interactions in communities of a native annual forb Waitzia acuminata (Asteraceae) and two invasive annual grasses that are ecologically similar and co-occur in southwestern Australia. Using a combination of field and laboratory experiments and several performance measures, we assessed impacts of these grasses on W. acuminata. We also examined differences among species in their responses to intraspecific versus interspecific competition, including their frequency dependence. The two similar exotic grasses differed in interaction impacts, with one facilitating and the other suppressing the native. In general, intraspecific competition was stronger than interspecific competition for the native, while evidence of competition was weak for the exotics. These patterns may reflect that W. acuminata does well in these communities due to the combined impacts of stabilization and facilitation, whereas the exotics benefit from limited stabilization (mediated by their weak intraspecific competition) or weak interspecific competition with W. acuminata. We found divergent impacts of the exotic species despite their similar functional traits. We demonstrate that a native species may benefit from interactions with an exotic "benefactor" species, highlighting the potential importance of positive interactions in invaded communities. Our findings underscore the necessity of considering neutral and positive interactions in addition to competition in understanding invasion dynamics in real plant communities.

Helimulching is commonly applied after high-severity wildfires in North America because of its effectiveness in reducing post-fire runoff and erosion. However, its use in other parts of the world is still very limited and information about its effects in different environments is scarce. In this study, the effects of helimulching on vegetation recovery and species composition were assessed in 70 experimental plots (80 m2 each) established in five shrubland areas in Northwest Spain affected by wildfire in summer 2013. The effects on shrub, forb, fern and grass cover, and on total vegetation cover, as well as on species richness, Shannon diversity index and heterogeneity were studied over the 2 years following the fire. The impacts of soil burn severity and mulch depth on these variables were also considered. Overall, the mulching treatment had little effect on the cover variables. Although it had a positive effect on forb cover, these species represented only a small portion of the total vegetation cover. Soil burn severity was not a significant factor in explaining the variation in the variables under study. The treatment had a low impact on species composition. In the mulched plots only three non-native species were recorded and these displayed a limited capacity to act as invasive species as they were absent at the end of the period of study. The results indicate that helimulching is a feasible soil stabilization treatment with neutral effects on vegetation cover and the composition of shrubland in coastal areas of Northwest Spain.