Plant Functional Diversity Research Articles

Diverse and larger tree islands promote native tree diversity in oil palm landscapes.

In monoculture-dominated landscapes, recovering biodiversity is a priority, but effective restoration strategies have yet to be identified. In this study, we experimentally tested passive and active restoration strategies to recover taxonomic, phylogenetic, and functional diversity of woody plants within 52 tree islands established in an oil palm landscape. Large tree islands and higher initial planted diversity catalyzed diversity recovery, particularly functional diversity at the landscape level. At the local scale, results demonstrated that greater initial planting diversity begets greater diversity of native recruits, overcoming limitations of natural recruitment in highly modified landscapes. Establishing large and diverse tree islands is crucial for safeguarding rare, endemic, and forest-associated species in oil palm landscapes.

The Indo–Pacific Pollen Database – a Neotoma constituent database

Abstract. The Indo–Pacific Pollen Database (IPPD) is the brainchild of the late professor Geoffrey Hope, who gathered pollen records from across the region to ensure their preservation for future generations of palaeoecologists. This noble aim is now being fulfilled by integrating the IPPD into the online Neotoma Paleoecology Database, making this compilation available for public use. Here we explore the database in depth and suggest directions for future research. The IPPD comprises 226 fossil pollen records, most postdating 20 ka but with some extending as far back as 50 ka or further. Over 80 % of the records are Australian, with a fairly even distribution between the different Australian geographical regions, with the notable exception being Western Australia, which is only represented by three records. The records are also well distributed in the modern climate space, with the largest gap being in drier regions due to preservation issues. However, many of the records contain few samples or have fewer than five chronology control points, such as radiocarbon, luminescence or Pb-210, for the younger sequences. Average deposition time for the whole database, counted as years per centimetre, is 64.8 yr cm−1, with 61 % of the records having a deposition time shorter than 50 yr cm−1. The slowest deposition time by geographical region occurs on Australia's east coast, while the fastest times are from the western Pacific. Overall, Australia has a slower deposition time than the rest of the Indo–Pacific region. The IPPD offers many exciting research opportunities to investigate past regional vegetation changes and associated drivers, including contrasting the impact of the first human arrival and European colonisation on vegetation. Examining spatiotemporal patterns of diversity and compositional turnover/rate of change, land cover reconstructions, and plant functional or trait diversity are other avenues of potential research, amongst many others. Merging the IPPD into Neotoma also facilitates inclusion of data from the Indo–Pacific region into global syntheses.

The Effect of Grazing on Central Anatolian Steppe Vegetation: A Modeling Approach Using Functional Traits.

Grazing is a major ecological driver that influences vegetation dynamics globally. We investigated the long-term effects of different grazing regimes on the vegetation structure of the Central Anatolian steppes, a region characterized by its unique convergence of biogeographical influences and historical land use. We employed the spatially explicit FATELAND model to simulate vegetation dynamics over a 50-year period under three distinct grazing scenarios: no grazing, moderate grazing, and overgrazing. Our simulations incorporated a range of plant functional traits to predict changes across five different vegetation types in Central Anatolia, including woodland steppes and treeless steppes. The simulations revealed that moderate grazing supports the diversity and abundance of various plant functional groups, excluding resprouter trees, which flourish under no grazing conditions. In contrast, overgrazing leads to significant reductions in the abundance of perennial forbs and both spiny and non-spiny subshrubs, often resulting in a shift toward grassland dominated by resprouter gramineae or an annual herb-dominated grassland, depending on the initial abundance of gramineae. Our findings highlight the critical role of grazing management in maintaining biodiversity and ecological stability in steppe ecosystems. While moderate grazing can enhance plant functional group diversity, overgrazing significantly threatens the ecological integrity of the Central Anatolian steppes. In conclusion, our modeling approach reveals that the grazing regime is a major driver in shaping the vegetation structure of Central Anatolian steppes. Grazing management strategies that are adjusted to the ecological characteristics and historical context of specific regions are required to prevent degradation and promote sustainable grassland vegetation.

Mutualistic interactions facilitate invasive species spread

Abstract Invasive species are major drivers of global ecosystem change. They often displace native species through competitive exclusion, creating novel species interactions. These interactions can lead to ecological cascades, where the presence of one invasive species enhances the fitness of another. Despite this, the mechanisms that underpin these mutualistic interactions and promote secondary invasions remain poorly understood. We assessed how the introduction of the invasive Argentine ant (Linepithema humile) alters mutualistic interactions within the recipient community, enhancing the dispersal and fitness of species of a secondary invasive plant genus (Acacia spp.). Our study examines these interactions at the community, individual species, and trait levels for a range of native and non‐native ant and plant species. Specifically, we aimed to investigate the direct and indirect effects of L. humile on seed dispersal mutualisms. We found that in L. humile invaded locations, seeds of the invasive Acacia plant species were approximately three times more likely to be dispersed than seeds of native endemic plant species. This preference is driven by indirect changes in the community structure of native seed‐dispersing ants, rather than direct interactions between the invasive ant and plant species. Moreover, we found that native ant species that co‐exist with L. humile, such as Tetramorium sericeiventre, respond to a narrower range of seed traits—traits which the invasive Acacia seeds possess. Our findings suggest that the invasion of L. humile has cascading effects on ant‐plant mutualisms, potentially increasing community permeability to secondary invasions. These results highlight that the impact of invaders like the Argentine ant may be greater than initially perceived, driving losses in both biological and functional plant diversity. Read the free Plain Language Summary for this article on the Journal blog.

The Inhibitory Tendency of Calamagrostis epigejos and Solidago spp. Depends on the Successional Stage in Postindustrial Vegetation

ABSTRACTIn spontaneously vegetated postindustrial areas, we have limited knowledge of whether the known inhibitory tendencies of herbaceous species—Calamagrostis epigejos and Solidago spp.—vary across successional stages. Our study fills this knowledge gap to assess the inhibitory role of the invasive alien and expansive native species with known behavior from the literature. Specifically, we hypothesized: (i) there will be an inhibitory effect of these species on diversity across successional classes; (ii) the effect of a species will depend on the successional class due to abiotic requirements of plant communities in each successional class. We recorded vascular plant species and their abundance across 400 plots on post‐coal mine heaps in Upper Silesia, Poland. We classified spoil heaps into three successional classes (early‐stage; mid‐stage; late‐stage). We calculated plant community taxonomic, functional, and phylogenetic diversity and, using generalized linear mixed‐effects models, we estimated predictors of diversity indices across successional classes. While we found no limiting effects of these species on diversity indices across successional classes, the effects of a species depended on the successional stage. We found the impacts of Calamagrostis and Solidago cover on diversity indices in the mid‐successional stage. This implies that the early‐successional stage is controlled by the lottery (random) model of community assembly. However, in the mid‐successional stage, the competitive exploitation mechanism is evident, resulting in declines in diversity indices. Thus, the impacts of Calamagrostis and Solidago on diversity indices are evident in the mid‐successional stage.

Modern pollen–plant diversity relationships for reliable pollen-based reconstruction of past plant taxonomic and functional diversity: A case study in southwest Shandong, China

Pollen diversity provides insights into our understanding of past plant diversity, a wide variety of diversity indices have been used to characterize plant diversity from sedimentary pollen. However, studies reported inconsistent associations between pollen-plant taxonomic diversity, this could be partly accounted for by biases due to interspecies differences in pollen production, pollen diffusion/deposition, and poorly specified dispersal distance of pollen-source plants. It is therefore crucial to improve the interpretation of the sedimentary pollen diversity by systematic studies of palynological and floristic diversity associations in contemporary landscapes.To test the reliability of pollen assemblages as a proxy of plant diversity, we collected pollen and vegetation from 36 surface sites in southwest Shandong. We detected the correlation between pollen-plant taxonomic and functional diversity indices from different spatial scales.Our results show pollen-plant correlations vary in spatial scales for different indices, the Spearman correlation analysis indicates significant and the strongest correlations between pollen-plant Shannon index around the RSAP (0.399 < ρ < 0.520), while the Pielou’s evenness shows significant and the highest correlations (0.411 < ρ < 0.425) around and beyond the RSAP, but only weak positive relationships can be detected between pollen-plant richness. Functional composition based on whole plant height and specific leave area and functional dispersion based on combined traits of whole plant height, specific leave area, seed mass, and leave dry mass shows significant positive pollen-plant associations, indicating that functional diversity may improve the pollen-plant link.Our results confirm that pollen data performs well in presenting plant taxonomic and functional diversity, which provides a solid theoretical basis for quantitative reconstruction of the long-term plant diversity dynamics and response of ecosystem functions to the environment in the future. Furthermore, the results demonstrate that the spatial scale of vegetation survey plays an important role in the representation of pollen diversity.

Effects of water limitation and competition on tree carbon allocation in an Earth system modelling framework

Abstract Earth system models (ESMs) have a limited capacity to represent plant functional diversity and shifts in trait distributions. Approaches to improving the representation of this complexity in ESMs include (i) optimality‐based approaches that predict trait–environment responses and (ii) explicitly modelling coexistence and community assembly. These approaches are expected to converge only when optimality‐based approaches identify competitively dominant strategies, which often differ from strategies that maximize ecosystem functioning or fitness components in monoculture. We used two models, LM3‐PPA (a vegetation demographic model designed as an ESM component) and BiomeE (a computationally efficient analog for LM3‐PPA), to explore how water limitation affects carbon allocation strategies of canopy trees. We compared competitive allocation strategies and those that maximize biomass or productivity in monoculture. We did not explicitly model coexistence or community assembly. Rather, we used model experiments to identify competitive and maximizing strategies in a two‐dimensional trait space under different precipitation and mortality scenarios. At 10 eastern US locations, we simulated historical, wet and dry climate scenarios, novel drought and three different mortality scenarios (low, medium or high sensitivity to water deficit). For each site and scenario, we identified the competitive strategy and three maximizing strategies (maximum biomass, productivity or drought‐tolerance). Root: leaf ratios tended to increase and leaf area tended to decrease with increasing water stress (increasing water limitation and its effects on mortality). However, relative to maximizing strategies, competitive strategies shifted towards greater allocation to roots and leaves with increasing water stress. Competitive overinvestments (greater allocation to roots and leaves by competitive strategies compared with maximizing strategies) were robust across different modelling contexts, including vegetation parameter sets (Acer vs. Populus), models (LM3‐PPA vs. BiomeE) and uncalibrated vsersus calibrated BiomeE versions. Synthesis: The theoretical prediction that competitive and maximizing allocation strategies differ under water limitation is confirmed for a demographic model designed as an ESM component. Optimality‐based trait predictions can simplify representing trait diversity in ESMs but do not always correspond to competitive outcomes. Explicitly modelling coexistence and community assembly in ESMs is challenging but is likely the most general approach to representing trait diversity.

Can we leverage botanical gardens to study global plant functional diversity?

AbstractBiodiversity is a multidimensional concept spanning the diversity of organismal form and function (functional diversity) together with taxonomic and genetic diversity. In the case of plants, botanical gardens have historically strived to preserve taxonomic diversity with a global scope. However, their success in preserving global functional diversity lacks testing. Given that living collections in botanical gardens span major global vegetation types and evolutionary histories, it is reasonable to expect that a species assemblage in a botanical garden is a representative random sample of global vegetation. In such a case, botanical gardens should contain global functional diversity. Testing for this could elect botanical gardens as laboratories for studying global plant functional diversity, providing a much‐needed alternative in the way we study global patterns of this diversity facet.

Subtle changes in plant diversity in the Bavarian Alps over the past eight decades.

Historical resurveys represent a unique opportunity to analyze vegetation dynamics over longer timescales than is typically achievable. Leveraging the oldest historical dataset of vegetation change in the Bavarian Alps, Germany, we address how environmental conditions, vegetation composition, and functional diversity in the calcareous grasslands of the Schachen region have changed across different elevational ranges over an 83-year timeframe. We document changes in regional average temperature and precipitation. We use indicator values (IV) for species' ecological preferences and their palatability to grazers to infer local conditions (temperature, soil moisture/fertility, and grazing regime). We further estimate changes in temporal beta-diversity and functional trait community composition between historical (1936) and contemporary (2019) surveys in two elevational (subalpine and alpine) belts. Both subalpine and alpine sites became drier; subalpine sites also became warmer with more palatable plants. Species occurrence and abundance in the Schachen region has not changed substantially over time despite changing macroclimate and local environmental conditions under anthropogenic change. Yet these grasslands have experienced several "invisible" changes in functional composition over the past 80 years. As the Schachen has become drier, species with traits related to drought tolerance and animal-based dispersal have increased in dominance. Specifically, in alpine sites, community-weighted means revealed that with low fecundity, higher potential for endo- and epizoochory (seed dispersal via animal gut and fur, respectively), higher foliar frost tolerance, and deeper dormancy increased in dominance. Similar trends were found for increasing dominance of low fecundity, epizoochorous species in subalpine sites. Vegetation data from resurveying historical plots in combination with changes in local conditions, classic biodiversity indices, and functional trait indices can provide more holistic insights into changes in the environment and potential impacts of those environmental changes on long-term plant community and functional diversity.

Varying patterns of taxonomic and functional plant composition and diversity across different types of urban and rural grasslands

AbstractSemi‐natural grasslands are found predominantly in agricultural landscapes; however, their counterparts are also found in cities, referred to as urban grasslands. We sampled the most extensive patches of urban grasslands in Wrocław (Poland, Europe) in urban parks and along a river valley. We compared urban grasslands to broadly defined rural grasslands in terms of compositional gradients and both taxonomic and functional diversity. We also tested for relationships between rare species and different facets of diversity. Urban grasslands corresponded to three rural grassland habitat types: mesic pastures, mesic meadows, and alluvial meadows. We conducted analogous analyses, including and excluding habitat‐level assignment, to determine if emerging patterns between rural and urban grasslands are habitat‐dependent. Rural pastures and their urban counterparts showed high taxonomic and functional similarity, implying that short‐ and frequent‐cutting, applied in cities, mimics grazing management on agricultural sites. Rural mesic hay grasslands and alluvial meadows showed high taxonomic and functional dissimilarities from their urban counterparts. We found that rare species contribute to taxonomic diversity while only affecting functional diversity in a few cases. Varying patterns of taxonomic and functional similarity were observed across different habitats. Comparisons of grasslands without regard for habitat types mask diverging patterns in taxonomic and functional diversity. Despite high environmental and management pressures in urban areas (higher nutrient levels and temperatures, decreased moisture, and intensified management and soil disturbances), we showed that urban grasslands hold a considerable portion of the plant diversity found in rural grasslands.

Do linear clearings in boreal peatlands recover? Comparing taxonomic, phylogenetic, and functional plant diversity

Land-use changes and anthropogenic disturbances are major threats to biodiversity, affecting ecosystem function and recovery. In boreal Alberta, Canada, petroleum development has led to extensive landscape fragmentation, notably through linear clearings created for seismic exploration that remove surface vegetation and microtopography. Despite partial recovery on forested seismic lines, peatland recovery is often arrested, impacting wildlife and carbon dynamics. Restoration efforts employ silviculture techniques to create microtopography and foster tree growth, but the efficacy of restoration treatments in restoring peatland plant diversity remains uncertain. We compared taxonomic, phylogenetic, and functional diversity of understory plant communities across treated and untreated seismic lines, alongside reference sites in treed bogs and fens. Treated lines generally had a twofold increase in plant height, leaf dry matter content, and foliar nitrogen and phosphorus contents compared to reference sites. In bogs, treated lines differed from reference conditions driven by increases in herbaceous taxa, while fens displayed disparities mainly in taxonomic and phylogenetic diversity. Differential responses of bogs and fens underline the necessity for tailored management strategies. Changes in plant diversity away from restoration targets have implications for ecosystem recovery, emphasizing the importance of long-term monitoring to evaluate the effectiveness of silviculture techniques in restoring boreal peatland plant communities.

Anti-seasonal flooding drives substantial alterations in riparian plant diversity and niche characteristics in a unique hydro-fluctuation zone.

Human-induced disturbances such as dam construction and regulation have led to widespread alterations in hydrological processes and thus substantially influence plant characteristics in the hydro-fluctuation zones (HFZs). To reveal utilization of limited resources and mechanisms of inter-specific competition and species co-existence of plant communities based on niche breadth and overlap under the different HFZs of the Three Gorges Reservoir (TGR) in China, we conducted a field investigation with 368 quadrats on the effects of hydrological alterations on plant diversity and niche characteristics. The results showed anti-seasonal flooding precipitated the gradual disappearance of the original diverse niches, resulting in the reduction of plant species richness and functional diversity and more obvious competition among plant species with similar resource requirements. Annuals, perennials and shrubs accounted for 71.23%, 27.39% and 1.37%, respectively, suggesting that annuals and flood-tolerant riparian herbs were favored under such novel flooding conditions. A consistent increase in species number, Shannon-Wiener diversity index and Simpson dominance index with altitude was inconsistent with hump-shaped diversity-disturbance relationship of the intermediate disturbance hypothesis, while the opposite trend was observed for the Pielou evenness index. This species distribution pattern might be caused by several synergetic attributes (e.g., the submergence depth, plant tolerant capacity to flooding, life form, dispersal mode and inter-specific competition). Vegetation types shifted from xerophytes to mesophytes and eventually to hygrophytes with the increasing flooding time in the HFZs. Hydrological alterations proved to be the paramount driver of vegetation distribution in the different HFZs. The niche analysis provided the first insights on the mechanisms of resource utilization and inter-specific competition, of which annuals could germinate quickly after soil drainage to achieve the greatest competitive advantages and occupy a larger niche space than other plants. Vegetation was still in the early stage of primary succession in the novel riparian forests. Therefore, vegetation restoration strategies should be biased towards herbaceous plants, due to annuals with better environmental adaptability, supplemented by shrubs and small trees. To establish a complete reference system for vegetation restoration, natural vegetation monitory plots in the different succession stages should be established in the different HFZs of the TGR, and their environmental conditions, community structures and inter-specific relationships further analyzed.

Functional responses of understory plants to natural disturbance-based management in eastern and western Canada.

Natural disturbance-based management (NDBM) is hypothesized to maintain managed forest ecosystem integrity by reducing differences between natural and managed forests. The effectiveness of this approach often entails local comparisons of species composition or diversity for a variety of biota from managed and unmanaged forests. Understory vegetation is regularly the focus of such comparison because of its importance in nutrient cycling, forest regeneration, and for wildlife. However, larger scale comparisons between regions with distinct species assemblages may require a trait-based approach to better understand understory responses to disturbance. We compared the long-term effects of retention harvesting on understory vegetation in two large experimental study sites located in eastern and western regions of the Canadian boreal forest. These sites included the Sylviculture en Aménagement Forestier Ecosystémique (SAFE) experiment and the Ecosystem Management Emulating Natural Disturbance (EMEND) experiment, located in the eastern and western regions of Canada, respectively. EMEND and SAFE share common boreal understory species but have distinct tree communities, soils, and climate. Both experiments were designed to evaluate how increasing tree retention after harvest affects biodiversity. Here, we examined taxonomic richness, functional diversity, and functional composition (using community trait mean values) of understory plant communities, and also examine intraspecific trait variability (ITV) for five species common and abundant in both experiments. We observed the limited impacts of retention level on richness, functional diversity, and functional composition of understory plants 20 years postharvest. However, ITV of leaf morphological traits varied between retention levels within each experiment, depending on the species identity. Common species had different functional responses to retention level, showing species-specific reactions to environmental variation. Our result suggests that understory plant communities in the boreal forest achieve resilience to disturbance both in terms of interspecific and intraspecific functional trait diversity. Such diversity may be key to maintaining understory biodiversity in the face of future disturbances and environmental change. Our results reveal the significance of ITV in plant communities for understanding responses to forest harvesting and the importance of choosing appropriate traits when studying species responses to the environment.

Correction: The functional diversity of plants dispersed via three upland rivers in humid subtropical monsoon climate

Correction: The functional diversity of plants dispersed via three upland rivers in humid subtropical monsoon climate

Grazing effects on vegetation: Biodiversity, management, and restoration

AbstractIn many regions, wild large herbivores have maintained open landscapes up to and including historic times, but, more recently, have been largely replaced by domestic livestock. By employing extensive and traditional grazing and browsing regimes, conservation actions support biodiversity and recovery in natural and degraded areas. However, grazing also plays other important ecological roles, for example, in the maintenance and/or recovery of important ecosystem services, such as biomass production and carbon sequestration. Understanding herbivore effects on plant composition and functional diversity, and ecosystem functioning and services, is essential for informing ecological theory and practice. The current Special Issue highlights that the effects of grazing on vegetation are strongly context‐dependent. The articles identify at least three major factors acting in concert, which are responsible for contrasting diversity and functional patterns of vegetation subjected to herbivores: (i) herbivore identity; (ii) grazing intensity; and (iii) vegetation type. Insights from this Special Issue imply that long‐term experiments across different habitat types and in underrepresented regions are needed to provide valuable information for grazing planning and management. They also demonstrate that integrating indigenous and traditional ecological knowledge, and considering socio‐economic contexts, can provide opportunities for improving sustainable grazing management.

Variation in near-surface soil temperature drives plant assemblage differentiation across aspect.

Quantifying assemblage variation across environmental gradients provides insight into the ecological and evolutionary mechanisms that differentiate assemblages locally within a larger climate regime. We assessed how vascular plant functional composition and diversity varied across microenvironment to identify ecological differences in assemblages in a mountainous fieldsite in northeastern Utah, USA. Then, we looked at how life-history strategies and information about phylogenetic differences affect the relationship between functional metrics and environment. We found less functionally dispersed assemblages that were shorter and more resource-conservative on south-facing slopes where intra-annual soil temperature was hotter and more variable. In contrast, we found more functionally dispersed assemblages, that were taller and more resource-acquisitive on north-facing slopes where intra-annual temperature was cooler and less variable. Herbaceous and woody perennials drove these trends. Additionally, including information about phylogenetic differences in a dispersion metric indicated that phylogeny accounts for traits we did not measure. At this fieldsite, soil temperature acts as an environmental filter across aspect. If soil temperature increases and becomes more variable, intra-annually, the function of north- versus south-facing assemblages may be at risk for contrasting reasons. On south-facing slopes, assemblages may not have the variance in functional diversity needed to respond to more intense, stressful conditions. Conversely, assemblages on north-facing slopes may not have the resource-conservative strategies needed to persist if temperatures become hotter and more variable intra-annually. Given these results, we advocate for the inclusion of aspect differentiation in studies seeking to understand species and assemblage shifts in response to changing climate conditions.

Plant silicon content as a proxy for understanding plant community properties and ecosystem structure

AbstractSilicon (Si) content in plant tissues is considered a functional trait that can provide multiple morpho‐physiological benefits to plant individuals. However, it is still unclear whether and how these individual benefits extend to plant community processes and ecosystem functioning. Here we investigated how plant Si content is associated with plant community properties and the ecosystem structure of herbaceous communities in Israel. We sampled 15 sites across the Mediterranean and desert ecosystems and built models to evaluate how plant silicon content (community‐weighted mean and standard variation) is associated with variables such as species richness, biomass production, plant cover, and functional diversity. Finally, we used model selection techniques to test whether models depicting plant Si content perform better than models using data on soil Si instead. Sites with lower susceptibility to drought had significantly more Si‐accumulating grass species and higher soils Si content. Models with plant Si content instead of soil Si, always performed better, although those considering Si content variation had overall stronger associations with community properties than only mean Si content. For instance, up to 51% of plant Si content variation was explained by climate, biomass production, and species richness, combined. Still, mean plant Si content and plant cover combined explained up to 42% of plant functional diversity. Our results suggest the that plant Si content serves as a proxy for understanding the ecological properties and functioning of arid and Mediterranean ecosystems. Nevertheless, the significance of Si has not been fully explored in other ecosystem types, where its influence may be less pronounced compared with the ecosystems examined in this study. In light of various global change scenarios, enhancing our understanding of Si as a plant functional trait could help bridge existing knowledge gaps and improve ecological modeling, thus enabling more accurate forecasts of changes in plant distributions.

Grasses don’t always win: Short-term effects of fertilization on taxonomic and functional diversity of a Mediterranean annual grassland

Nitrogen pollution has increased dramatically over the last decades, becoming a major contributor to biodiversity loss and compositional changes globally. While the main effects of excessive nutrients on plant communities are well established, Mediterranean grasslands have been less studied despite their high levels of biodiversity. Moreover, evidence has shown that the impacts of nutrients may depend on additional factors, namely soil conditions and grazing, increasing the uncertainty about the effects of increasing nutrient availability in these systems. In this work, we assessed the short-term effects (1 year) of fertilization in an extensively grazed oak open woodland (called montado, or dehesa), in Spain. Plots comprised a complete randomized design with four treatments: control (not fertilized), fertilization with nitrogen at a rate of 100 kg N ha−1, fertilization with phosphorous (50 kg P ha−1) and fertilization with both N and P (100 kg ha−1 N + 50 kg ha−1 P). We assessed changes in plant species composition and functional diversity and evaluated the association between species and fertilization treatments with an indicator species analysis. Our results showed that species diversity increased with NP fertilization and that forbs in particular increased in cover and richness. SLA and seed mass also showed differences compared to the control. The Community-weighted mean and functional dispersion of groups based on growth form and N-fixing ability were not influenced by fertilization. Two species were significantly associated with fertilized plots: the spiny forb Carlina racemosa and the latex-producing forb Tolpis barbata. Our study suggests that short-term fertilization may alleviate nutrient limitations in these systems, increasing plant diversity, although longer-term studies are needed to understand the effects of a continuous increase in nutrient availability.

Plant species diversity and functional diversity relations in the degradation process of desert steppe in an arid area of northwest China

Species and functional diversity play a major role in the stability and sustainability of grassland ecosystems. However, changes in species and functional diversity during grassland degradation in arid areas as well as the underlying mechanisms remain unclear. In this study, we surveyed the vegetation and soil properties of arid regions across a degradation gradient to explore the shifts in species and functional diversity in plant communities, their relationships and key determinants during desert steppe degradation. Our results found significant variability in species diversity and functional diversity across degradation stages. Species diversity (Shannon-Wiener index (H), and Pielou index) and functional diversity (functional evenness (FEve) index, and Rao's quadratic entropy (RaoQ) index) tended to increase initially and then decrease with increasing grassland degradation. The Patrick index, Simpson index, functional richness (FRic) index, functional divergence (FDiv) index, and functional dispersion (FDis) index declined as grassland degradation increased. The relationships between species diversity and functional diversity indices at different stages of degradation in the desert steppe were inconsistent. From no to heavy degradation grasslands, the correlation between species diversity and functional diversity gradually weakened. Specifically, there was a significant correlation between Patrick (R) and FRic indices (R2 > 0.7) on both non-degraded and light degraded grasslands, but there was no significant correlation between R and FRic indices in moderately and heavily degraded grasslands (R2 < 0.7), and R2 gradually decreased. Redundancy analysis and partial least squares path modeling showed that grassland degradation has a significant direct effect on the species diversity and functional diversity. In addition grassland degradation has direct and indirect effects on the species diversity through soil available nitrogen, organic matter and total nitrogen. Functional diversity is directly or indirectly affected by species diversity, soil available nitrogen, organic matter and total nitrogen, soil moisture content, soil bulk density, and pH value. In summary, the relationship between species and functional diversity indices gradually weakened from areas with no degradation to heavy degradation in arid desert grasslands. Our study reveals the patterns and relationships between species diversity and functional diversity throughout the process of grassland degradation, demonstrating a gradual decrease in ecosystem stability and sustainability as degradation advances. Our results have significant implications for the restoration of grassland degradation and the management of ecosystem services in arid steppe regions.

The functional diversity of plants dispersed via three upland rivers in humid subtropical monsoon climate

The functional diversity of plants dispersed via three upland rivers in humid subtropical monsoon climate