Meadow Plant Research Articles

Effects of experimentally reduced snowpack and passive warming on montane meadow plant phenology and floral resources

AbstractClimate change can have a broad range of effects on ecosystems and organisms, and early responses may include shifts in vegetation phenology and productivity that may not coincide with the energetics and forage timing of higher trophic levels. We evaluated phenology, annual height growth, and foliar frost responses of forbs to a factorial experiment of snow removal (SR) and warming in a high‐elevation meadow over two years in the Rocky Mountains, United States. Species included arrowleaf balsamroot (Balsamorhiza sagittata, early‐season emergence and flowering) and buckwheat (Eriogonum umbellatum, semi‐woody and late‐season flowering), key forbs for pollinator and nectar‐using animal communities that are widely distributed and locally abundant in western North America. Snow removal exerted stronger effects than did warming, and advanced phenology differently for each species. Specifically, SR advanced green‐up by a few days for B. sagittata to >2 wk in E. umbellatum, and led to 5‐ to 11‐d advances in flowering of B. sagittata in one year and advances in bud break in 3 of 4 species/yr combinations. Snow removal increased height of E. umbellatum appreciably (~5 cm added to ~22.8 cm in control), but led to substantial increases in frost damage to flowers of B. sagittata. Whereas warming had no effects on E. umbellatum, it increased heights of B. sagittata by >6 cm (compared to 30.7 cm in control plots) and moreover led to appreciable reductions in frost damage to flowers. These data suggest that timing of snowmelt, which is highly variable from year to year but is advancing in recent decades, has a greater impact on these critical phenological, growth, and floral survival traits and floral/nectar resources than warming per se, although warming mitigated early effects of SR on frost kill of flowers. Given the short growing season of these species, the shifts could cause uncoupling in nectar availability and timing of foraging.

Coastal meadow management for threatened waders has a strong supporting impact on meadow plants and amphibians

Wet grasslands provide unique habitats for several taxa and offer multiple ecosystem services. Their degradation is therefore of increasing concern in many parts of the world. Baltic coastal meadows, which host diverse plant and bird communities and provide an essential breeding ground for amphibians, belong to the most threatened habitat types in Europe. In spite of the EU agri-environmental schemes, the threatened wader and toad populations, characteristic to these meadows, have not recovered, suggesting that the management efforts are failing to provide sufficiently high habitat quality for these species. In this paper we report the results of a large-scale survey determining the factors that influence the patterns of breeding habitat selection of four Charadriiform bird species on 24 coastal meadows in Estonia. We also examined whether the habitat conditions required by the threatened waders would benefit breeding amphibians and meadow plants and whether the threatened waders might act as focal species for managing coastal meadow biodiversity. In total, we analysed 23 landscape-variables, applying co-inertia analysis to discover common multivariate patterns in coastal meadow characteristics, breeding waders, plants and amphibians. We demonstrated that large (≥100ha) and wide (mean width ≥200m) meadows with extensive grazing, high water-table and no woody vegetation provide favourable breeding conditions for waders of conservation concern, but at the same time also support other Charadriiform birds, larger amphibian populations, and more diverse plant communities. Meadow management should therefore be targeted at threatened waders, especially Baltic dunlin, which could be considered as a focal species, and focus on the establishment of large and wide meadow areas with extensive grazing.

Leaf acclimation to experimental climate warming in meadow plants of different functional types

The use of open-top chambers (OTCs) installed in natural plant cover is one of the approaches to study plant responses to climate change. Three OTCs made from polyethylene film were installed on a herbgrass meadow in the subzone of the southern taiga before the beginning of the growing season. A significant increase in the average daily temperature values (by 0.5°C) and the relative humidity (by 10%) compared to control conditions was observed inside the chambers. Plant height, leaf parameters, and the pigments content were studied for six species of meadow plants during the growing season in two variants—inside the chamber and outside the chamber (control); more than 20 quantitative parameters of the mesophyll were studied for four of the species. It was found that the differences in microclimatic conditions had no effect on plant height and leaf area. A slight decrease in the thickness and density of the leaves and an increased water content were noted inside the OTCs. In contrast to weak changes in external leaf parameters, the internal leaf structure and the content of photosynthetic pigments varied considerably. Warming caused the reduction of the content of chlorophyll and carotenoids per unit leaf area in the majority of studied species, except for Veronica chamaedrys L., but the ratio of pigment forms did not change. Changes in the pigments content in the leaf were associated with some structural rearrangements in the mesophyll, whose mechanism depended on the functional properties of the species. Increased size of palisade cells and the number of chloroplasts per cell was noted in the ruderal species (R/CSR-strategist) Taraxacum officinale Wigg. s. l.; the reduction of chlorophyll content per leaf area occurred due to the decrease in chlorophyll content per a single chloroplast. Decreased number of cells and chloroplasts per leaf unit area without any changes in their size was marked for the species with S/CSR strategy Alchemilla vulgaris L. s. 1. and V. chamaedrys L. in a chamber, but the content of chlorophyll per a chloroplast increased. An increase in the number of cells and a simultaneous decrease in their size was observed in CR-strategist Cirsium setosum (Willd.) Bess. inside the OTC; the chlorophyll content per chloroplast did not change. It was concluded that the acclimation of plants to short-term climate warming was associated with the restructuring of leaf mesophyll, whose mechanism depended on the functional properties of the species.

Functional dissimilarity, not phylogenetic relatedness, determines interspecific interactions among plants in the Tibetan alpine meadows

The hypotheses suggesting that the nature and strength of species interactions should be determined by phylogenetic relatedness have important implications for the understanding of community structure. However, to date, there is limited empirical evidence to support them. At least two basic conditions need to be met in order to expect species interactions to be determined by evolutionary relatedness: a phylogenetic signal in the traits involved in the interactions and changes in the interactions as species are more ecologically similar. Here, we report results of a removal experiment in the Chinese Tibetan plateau in which we directly assessed if the nature and/or strength of interactions among twelve alpine meadow plant species were influenced by their phylogenetic relatedness and/or their functional dissimilarity. For each plant species, we compared its biomass production when grown alone to its biomass in presence of another species and used it as a measure of species interactions. Competition between pairs of species was more frequent than facilitation, with 60% of interactions resulting in plants producing less biomass when a second species was present. We found no effect of phylogenetic relatedness on the prevalence or intensity of competition or facilitation, presumably as none of the studied traits showed phylogenetic signal. Functional dissimilarity based on maximum plant height alone was the best predictor of both the prevalence and strength of competition and facilitation, followed by functional dissimilarity using all five functional traits. Our results pinpoint the limited capacity of phylogenetic relatedness as predictor of species interactions; underlining the limitations of using phylogenetic dispersion patterns to infer mechanisms of community assembly. On the contrary, when the right functional traits are used, functional dissimilarity among species can predict both the nature and strength of their interactions; accentuating the relevance of trait‐based approaches in community ecology research.

Alterations to biological soil crusts with alpine meadow retrogressive succession affect seeds germination of three plant species

Biological soil crusts (BSCs) are the important components of alpine meadow ecosystems. The extent and morphology of BSCs vary greatly with alpine meadow retrogressive succession due to grazing pressure. There is significant interest in impacts of crust composition on plant seed germination, especially in (semi-) arid environments. However, little is known about the influences of BSCs, and their associations with alpine meadow succession, on germination of typical alpine meadow vascular plant species. In a full factorial common-garden experiment, we studied effects of: (1) crust type, (2) seed position, and (3) surface texture on seed germination. We chose three typical alpine meadow plant species (i.e. Poa pratensis, Tibetia himalaica and Potentillen nivea), which belonged to different functional groups (graminoids, legumes, and forbs) and play important roles in all alpine meadow succession stages. Crust type and seed position influenced seed germination, and the inhibitory effects of BSCs depended on the crust type and seed species tested. The major factors influencing seed germination were BSC type, seed position, soil texture, and the interactions between BSC type and seed position; species and seed position; species and surface texture; and species, crust type, and surface texture. Cyanobacteria crust significantly inhibited germination of all seeds. Seed position also had a significant effect on seed germination (p < 0.001). Fewer seedlings germinated on the surface than below the surface, this was especially true for P. nivea. seeds within cyanobacteria and lichen crusts. Only germination rates of T. himalaica on the soil surface were significantly correlated with plant occurrence frequency within the alpine meadow community. The poor correlation for the other two species is possibly that they are perennials. Our results clearly demonstrated that BSCs can be biological filters during seed germination, depending on the BSC succession stage. Through their influences on seed germination, BSCs can strongly influence community assemblages throughout alpine meadow retrogressive succession.

Links between shoot and plant longevity and plant economics spectrum: Environmental and demographic implications

The tacit assumption of functional ecology is that traits affect plant fitness. However, this link is mediated by demography, e.g. specific leaf area is not affecting changes in abundance directly but through vegetative multiplication or generative reproduction of plants − it means via demographic processes. We propose that in herbaceous perennials, architectural traits that capture shoot development constitute simple morphological surrogates of a number of demographic functions (shoot lifespan, lateral spread, multiplication rate). A shoot is a reiterated basic unit of a plant body in herbs and is easily recognizable as an individual. We propose that potential shoot lifespan (shoot cyclicity) may serve as a simple character relevant to demographic processes of clonal herbs while whole plant longevity plays a similar role for non-clonal herbs. Therefore we examined relationships of shoot and whole-plant lifespans with a key trait of the plant economic spectrum (specific leaf area, SLA) for a large set of Central European temperate zone herbs. We also investigated whether shoot and whole-plant lifespan are non-randomly distributed along environmental gradients, using indicator values and their distribution among plant community types. Finally, we analysed whether shoot cyclicity underlies differences in temporal turnover of plants in species-rich meadows. Our analyses showed that fast-growing species had shorter shoot and/or plant lifespan and preferred more productive environmental conditions, but the relationship was not strong. In addition, the two lifespan measures were independent of each other, indicating that shoot lifespan captures a rather different aspect of plant demography than whole-plant longevity. Turnover of perennial plants with annual shoots in meadow community was much higher than that of plants with long-lived shoots. Whole-plant and shoot lifespan constitute promising proxy variables for a mechanistic link between functional traits and community ecology in the temperate zone and deserves further attention.

Grazing‐induced shifts in community functional composition and soil nutrient availability in Tibetan alpine meadows

SummaryThe functional structure of plant communities can be altered by grazing through two main mechanisms: species turnover (i.e. changes in species occurrence and relative abundance) and intraspecific trait variability (ITV), which is driven by phenotypic responses of individual plants and shifts in the relative abundance of genotypic variants within species. Studies of grassland ecosystem function under grazing often focus on community changes induced by species turnover, which ignores the effects ofITVon biomass productivity, soil carbon or nutrient availability. By quantifying the relative contribution of both effects on shifts in community‐wide traits, we highlight the role ofITVin community functional response to grazing and its implications for ecosystem function in Tibetan alpine meadows.We measured three chemical traits (LC: leaf carbon,LN: leaf nitrogen andLP: leaf phosphorus concentrations) and two morphological traits (SLA: specific leaf area,LDMC: leaf dry matter content) that are critical components of plant production and forage quality in grazed and ungrazed plots. Using variance decomposition of community‐weighted means (CWM) for these foliar traits, we distinguished the relative importance ofITVvs. change in species occurrence and abundance in response to grazing and the associated changes in soil carbon and nutrient availability.TheCWMfor foliar nutrients andSLACWMincreased in response to grazing together with decreases in soil carbon and nutrient stores, especiallyLPCWMenrichment and loss of available soil P. TheLPCWMwas strongly negatively correlated withLDMCCWM, which was significantly higher in ungrazed plots. These community‐wide trait responses to grazing were generally best captured byITVand not changes in species occurrence and abundance, althoughITVwas consistently correlated with species turnover for all traits.Synthesis and applications. In response to continuous grazing, plants in Tibetan alpine meadows increase specific leaf area and foliar nutrients but tend to have lower leaf dry matter content, a response consistent with faster growth and regrowth under grazing. This intraspecific trait variability response drives a shift in community function from conservative, slow‐growing resource use in ungrazed meadows to exploitative resource use under grazing. This community‐wide functional response enhances forage quality, in turn favouring the secondary productivity of small herbivorous mammal communities, but also contributes to accelerated depletion of soil available phosphorus. We discuss the implications of these results for biodiversity conservation, ecosystem function and rangeland sustainability in the Qinghai–Tibetan Plateau, especially with regard to managing grazing rotation to strike a balance between favouring secondary productivity of domesticated stock vs. small herbivorous mammals.

Metabolic pathways of benzimidazole anthelmintics in harebell (Campanula rotundifolia)

Benzimidazoles anthelmintics, which enter into environment primarily through excretion in the feces or urine of treated animals, can affect various organisms and disrupt ecosystem balance. The present study was designed to test the phytotoxicity and biotransformation of the three benzimidazole anthelmintics albendazole (ABZ), fenbendazole (FBZ) and flubendazole (FLU) in the harebell (Campanula rotundifolia). This meadow plant commonly grows in pastures and comes into contact with anthelmintics through the excrements of treated animals. Suspensions of harebell cells in culture medium were used as an in vitro model system. ABZ, FLU and FBZ were not found to be toxic for harebell cells, which were able to metabolize ABZ, FLU and FBZ via the formation of a wide scale of metabolites. Ultrahigh-performance liquid chromatography coupled with high mass accuracy tandem mass spectrometry (UHPLC-MS/MS) led to the identification of 24, 18 and 29 metabolites of ABZ, FLU and FBZ, respectively. Several novel metabolites were identified for the first time. Based on the obtained results, the schemes of the metabolic pathways of these anthelmintics were proposed. Most of these metabolites can be considered deactivation products, but a substantial portion of them may readily be decomposed to biologically active substances which could negatively affect ecosystems.

Diversity and distribution patterns of root-associated fungi on herbaceous plants in alpine meadows of southwestern China

The diversity of root-associated fungi associated with four ectomycorrhizal herbaceous species, Kobresia capillifolia, Carex parva, Polygonum macrophyllum and Potentilla fallens, collected in three sites of alpine meadows in southwestern China, was estimated based on internal transcribed spacer (ITS) rDNA sequence analysis of root tips. Three hundred seventy-seven fungal sequences sorted to 154 operational taxonomical units (sequence similarity of ≥ 97% across the ITS) were obtained from the four plant species across all three sites. Similar taxa (in GenBank with ≥ 97% similarity) were not found in GenBank and/or UNITE for most of the OTUs. Ectomycorrhiz a made up 64% of the fungi operational taxonomic units (OTUs), endophytes constituted 4% and the other 33% were unidentified root-associated fungi. Fungal OTUs were represented by 57% basidiomycetes and 43% ascomycetes. Inocybe, Tomentella/Thelophora, Sebacina, Hebeloma, Pezizomycotina, Cenococcum geophilum complex, Cortinarius, Lactarius and Helotiales were OTU-rich fungal lineages. Across the sites and host species the root-associated fungal communities generally exhibited low host and site specificity but high host and sampling site preference. Collectively our study revealed noteworthy diversity and endemism of root-associated fungi of alpine plants in this global biodiversity hotspot.

Methods of Analysis of Environmental Diversity of Plants

There are considered new approaches to the analysis of an ecological variety of plants with use of ecological scales. There are offered the quantitative methods of determination of ecological valency and tolerance of species of plants. There are estimated ecological positions of forest and meadow plants in different parts of areas in the Mari El Republic, the Mos- cow, Tver regions of Russia. The carried-out analysis of conditions of cenopopulations’ habitats (central processing unit) of plants of various vital forms showed that all of them borrow in different parts of areas of the territory with rather narrow ranges of the considered abiotic factors. It testifies to their fitness to cumulative influence of a certain set of climatic and soil factors of different regions. Determination of potential ecological valency and the characteristic of species on scales of factors gives the chance to solve a problem of a quantitative assessment of ecological tolerance of t species of various vital forms and strategy in relation to separate factors. The indicators of the potential and realized ecological valency and an index of tolerance offered by us can widely be applied to the characteristic of ecosystems in which cenopopulation of plants, for an assessment of ecological positions of types are presented. Use of this approach is also actually in compar- ative floristics and in the ecological analysis of the protected plants.

Конфлікти природоохоронних територій великих міст: причини і наслідки

The main geoecological problems of protected areas within large cities and the reasons for their occurrence were researched on the example of the regional landscape park (RLP) “Lysa Gora” in Kiev. The absence of proper information about the importance and value of protected area in combination with the lack of funds for protection service raise a number of problems associated with non-compliance with environmental treatment area. In particular, visiting a park on private vehicle leads to destruction of rare plant species, animals deterrence, trampling natural vegetation. As a result of mass recreation of Kyiv residents during the holidays, solid waste pollution has a devastating effect on natural ecosystems. Burning fires leads to the death of Red Book and rare plant species, destruction of mountain steppe areas and all seed fund. In the tract area and around it formed the powerful centers of reproduction of invasive plants. Progressive erosion, landslides activate, degrade valuable meadow and deciduous plant communities. Illegal deforestation is happening in some Kyiv areas; the snow collected from city streets is stored in the protective zone of the river Lybid. Together with the snow a huge amount of debris, dirt and salt get into water and change the geochemical regime of surrounding area. Analysis of the above-mentioned and other negative influences and their implications for protected area allows to make a conclusion about the need for elimination or mitigation of the existing natural-using conflicts, particularly by establishing of park recreational capacity to prevent the destruction of especially valuable parcels natural components; functional zoning RLP area considering environmental, recreational, scientific, health, recreational, historical, cultural and other values; documentary consolidation of land plots with their strict subordination; establish effective penalties for areas special regime violations and excessive recreation load. In the future, the successful solution of the existing problems should conduct thorough research on functional zoning for the purpose of reserved kernel allocation, to implement measures for the resettlement of rare flora species and reintroduction of lost species, restoration of vegetation and more. Mapped scheme of main nature using conflicts within RLP is developed. A set of preventive and remedial measures to minimize existing conflicts and optimization of nature protection institutions in urban environment is proposed.

季节性冻融期间土壤动物对高山草甸两种凋落叶失重的贡献

季节性冻融期间土壤动物对高山草甸两种凋落叶失重的贡献

Substrate depth and roof age strongly affect plant abundances on sedum-moss and meadow green roofs in Helsinki, Finland

Green (i.e. vegetated) roofs are an increasingly popular measure to improve climate regulation in residential areas. However, there is limited knowledge on the effect of green roof characteristics (e.g. substrate depth and roof age, size and height), especially in northern climates, on plant species composition of the roofs, even though roof performance is mediated through the plants. We hypothesized that substrate depth and roof age, size and height shape the vegetation on green roofs. We inventoried vegetation on 51 green roofs in the metropolitan area of Helsinki in 2011 and found 230 plant species, of which seven are red-listed. We showed that substrate depth and roof age were predominant in structuring plant communities on green roofs. Thin substrates and young roofs maintained sedum and moss species, while thick substrates and older green roofs supported meadow plants. Roof size and height had variable effects on the vegetation. Our results provide knowledge on the dependence of plant species on roof parameters, which is useful in the planning for particular vegetation on roofs taking into account, e.g. load capacity and substrate depth, the wanted functional properties of the roof, and maintenance.

Abiotic mediation of a mutualism drives herbivore abundance.

Species abundance is typically determined by the abiotic environment, but the extent to which such effects occur through the mediation of biotic interactions, including mutualisms, is unknown. We explored how light environment (open meadow vs. shaded understory) mediates the abundance and ant tending of the aphid Aphis helianthi feeding on the herb Ligusticum porteri. Yearly surveys consistently found aphids to be more than 17-fold more abundant on open meadow plants than on shaded understory plants. Manipulations demonstrated that this abundance pattern was not due to the direct effects of light environment on aphid performance, or indirectly through host plant quality or the effects of predators. Instead, open meadows had higher ant abundance and per capita rates of aphid tending and, accordingly, ants increased aphid population growth in meadow but not understory environments. The abiotic environment thus drives the abundance of this herbivore exclusively through the mediation of a protection mutualism.

First report of Fusarium poae associated with and/or causing silvertop on loloid-type Festulolium in the Czech Republic

Silvertop is a serious disease of grasses, and severe infestations cause a great deal of damage every year (particularly to seed producers). Inflorescences of infected plants dry prematurely and are sterile. The genera Festuca, Poa, Agrostis, Trisetum, and Cynosurus are the most frequent hosts of this disease, which has newly been reported in a loloid-type intergeneric Festulolium hybrid. The disease was also observed in the genus Lolium, with only rare previous description. The suspicion that Fusarium poae is the causal agent of severe silvertop was confirmed, and the pathogen was morphologically described and confirmed by molecular analysis. The meadow plant bug (Leptopterna dolabrata) may be a vector transferring the pathogen to plants, although a direct pathogen transfer was not demonstrated. Grass colonisation by the pathogen therefore apparently occurs after plant tissues injury by sucking of the meadow plant bug.

Historical and recent fragmentation of temperate floodplain grasslands: Do patch size and distance affect the richness of characteristic wet meadow plant species?

Patch size and isolation are thought to have a large influence on the extinction risk of specialist plant species in grassland fragments in the modern agricultural landscape. We combined a re-sampling study in semi-permanent floodplain grassland plots with a GIS-based analysis of historical (1950s/1960s) and recent landscape patterns. Based on historical and recent vegetation maps and releves from six study areas (plus a protected reference area) covering 50–60 years of vegetation change following agricultural intensification, we aimed at analysing the importance of fragmentation on the diversity of potentially sensitive specialist species of wet floodplain meadows in northern Germany. On the plot scale, we found 30–66 % reductions in species richness of these characteristic wet meadow plant species over time and an associated increase in the fragmentation of grassland habitats. Distance to the nearest suitable habitat had a modest negative effect on modern plot-scale richness, while the other tested landscape metrics (total meadow area, mean patch size and landscape proximity index distribution) had no significant influence. There was also no evidence for a legacy of historical landscape structure on current richness of specialist species. Instead, management intensity and its change over the past decades, as indicated by altered Ellenberg indicator values for nutrients and moisture, had a strong influence on plot-scale diversity. The results suggest that fragmentation is not the proximate cause of impoverishment and point to habitat deterioration as a main driver. We conclude that conservation measures in Central-European floodplain meadows should not only focus on large continuous grassland areas, but should also consider small meadow patches if they remained species-rich.

Cuticular waxes in alpine meadow plants: climate effect inferred from latitude gradient in Qinghai-Tibetan Plateau.

Alpine meadow ecosystems are susceptible to climate changes. Still, climate impact on cuticular wax in alpine meadow plants is poorly understood. Assessing the variations of cuticular wax in alpine meadow plants across different latitudes might be useful for predicting how they may respond to climate change. We studied nine alpine meadows in a climate gradient in the east side of Qinghai-Tibetan Plateau, with mean annual temperature ranging from -7.7 to 3.2°C. In total, 42 plant species were analyzed for cuticular wax, averaged 16 plant species in each meadow. Only four plant species could be observed in all sampling meadows, including Kobresia humilis,Potentilla nivea,Anaphalis lacteal, and Leontopodium nanum. The amounts of wax compositions and total cuticular wax in the four plant species varied among sampling meadows, but no significant correlation could be observed between them and temperature, precipitation, and aridity index based on plant species level. To analyze the variations of cuticular wax on community level, we averaged the amounts of n-alkanes, aliphatic acids, primary alcohols, and total cuticular wax across all investigated plant species in each sampling site. The mean annual temperature, mean temperature in July, and aridity index were significantly correlated with the averaged amounts of wax compositions and total cuticular wax. The average chain length of n-alkanes in both plant and soil linearly increased with increased temperature, whereas reduced with increased aridity index. No significant correlation could be observed between mean annual precipitation and mean precipitation from June to August and the cuticular wax amounts and average chain length. Our results suggest that the survival of some alpine plants in specific environments might be depended on their abilities in adjusting wax deposition on plant leaves, and the alpine meadow plants as a whole respond to climate change, benefiting the stability of alpine meadow ecosystem.

Plant species richness is not consistently associated with productivity in experimental subalpine meadow plant communities

The relationship between species richness and productivity has been a central issue in community ecology, and this issue has resulted in much debate in the ecological literature. To evaluate whether species richness is consistently associated with productivity and the underlying mechanisms, a potted experiment with various combinations of three perennial plant species (Elymus nutans, Roegneria nutans and Festuca sinensis) was conducted under three fertilization levels over three years with interannual variation in rainfall in a subalpine meadow on the Tibetan plateau, China. The additive partitioning method was used for measuring net, selection and complementarity effects. The results suggest that species richness, composition and density had significant effects on aboveground biomass, but their effects were much less than abiotic factors (fertility and year). Relative yield total (RYT), net, selection and complementarity effects were not consistently positive or negative across years in the mixed communities. Both the interaction of year and species richness and the interaction of year and composition had significant effects on aboveground biomass, selection and complementarity effects. Fertilization and density had no significant effects on net, selection and complementarity effects. Our results indicate that plant richness is not consistently associated with productivity in these experimental plant communities, considering that selection and complementarity effects can vary with complex environmental conditions, and that these factors influence plant productivity. We suggest that different forms of relationships between species richness and productivity may be exhibited based on biotic or abiotic factors in plant communities.

Grazing increases functional richness but not functional divergence in Tibetan alpine meadow plant communities

Plant community diversity and ecosystem function are conditioned by competition among co-occurring species for multiple resources. Previous studies suggest that removal of standing biomass by grazing decreases competition for light, but coincident grazing effects on competition for soil nutrients remain largely unknown in Tibetan rangelands where grazing tends to deplete soil phosphorus availability. We measured five functional traits indicative of plant productivity and stoichiometry leaf carbon concentration (LCC), leaf nitrogen concentration (LNC), leaf phosphorus concentration (LPC), specific leaf area (SLA), leaf dry matter content (LDMC) for component species of plant communities in grazed and ungrazed plots in five Tibetan alpine meadows. We examined the diversity of traits singly Rao index of functional diversity (FDrao) and in aggregate functional richness (FRic), functional divergence (FDiv), and functional evenness (FEve) in response to grazing. We tested whether foliar trait diversity increases with nutrient competition but decreases with light competition when competitive exclusion is reduced by grazing. The FDrao of LPC significantly increased under grazing, but FDrao for LCC, LNC and SLA tended to decrease. The FDrao of LDMC increased at the drier site but decreased at the wettest site. There was a strong negative association between increase in FDrao of LPC and decrease in soil nutrients, especially soil phosphorus availability. The FRic for all five traits together increased with species diversity following grazing, but neither FDiv nor FEve differed significantly between grazed and ungrazed plots at most sites. Grazing in Tibetan alpine meadows tends to increase competition for soil phosphorus while decreasing competition for light, resulting in an increase in the functional richness in grazed plant communities without any significant changes in the overall functional diversity of foliar traits. Our study highlights the potential importance of grazing mediated competition for multiple resources in alpine meadow ecosystems.

Using functional trait diversity to evaluate the contribution of multiple ecological processes to community assembly during succession

Successional chronosequences provide a unique opportunity to study the effects of multiple ecological processes on plant community assembly. Using a series of 0.5 × 0.5 m2 plots (n = 30) from five successional sub‐alpine meadow plant communities (ages 3, 5, 9, 12, and undisturbed) in the Qinghai‐Tibetan Plateau, we investigated whether community assembly is stochastic or deterministic for species and functional traits. We tested directional change in species composition, functional trait composition, and then functional trait diversity measured by Rao's quadratic entropy for four traits – plant height, leaf dry matter content, specific leaf area, and seed mass – along two comparable successional chronosequences. We then evaluated the importance of species interactions, habitat filtering and stochasticity by comparing with random communities and partitioning the environmental and spatial components of Rao's quadratic entropy. We found no directional change in species composition, but clear directionality in functional trait composition. None of the abiotic environmental variables (except P) showed linear change with successional age, but soil moisture and nitrogen were positively related to functional diversity within meadows. Functional trait diversity increased significantly with the increase in successional age. Comparison with random communities showed a significant shift from trait divergence in early stages of succession (3‐ and 5‐yr) to convergence in the later stages of succession 9‐, 12‐yr and undisturbed). The relative importance of abiotic variables and spatial structure for functional trait diversity changed in a predictable manner with successional age. Stochasticity at the species level may indicate dispersal limitation, but deterministic effects on functional trait distributions show the role of both habitat effects and biotic interactions.