Figure - available from: Ecology Letters
This content is subject to copyright. Terms and conditions apply.
Effects of proportion light transmission, aboveground live biomass, site richness and evenness on the slope (z), (log c) and x‐intercept (a) of the species–area relationships (SARs) in grasslands. Solid points show SAR parameters for the subset of sites with all fencing and nutrient addition treatments (16 sites). Open circles and dashed lines show SAR parameters from sites with control plots (black lines, 30 sites) and the subset of these with nutrient addition treatments but not fencing (red lines, 21 sites). Lines are shown only for significant regressions. Full analysis is presented in Table S5
Source publication
The effects of altered nutrient supplies and herbivore density on species diversity vary with spatial scale, because coexistence mechanisms are scale dependent. This scale dependence may alter the shape of the species–area relationship (SAR), which can be described by changes in species richness (S) as a power function of the sample area (A): S = c...
Similar publications
Ecological models predict that the effects of mammalian herbivore exclusion on plant diversity depend on resource availability and plant exposure to ungulate grazing over evolutionary time. Using an experiment replicated in 57 grasslands on six continents, with contrasting evolutionary history of grazing, we tested how resources (mean annual precip...
Citations
... increasing β diversity) because higher nutrient levels may promote both stochastic and density-dependent processes including priority effects and heterogeneity of diversity-limiting processes such as herbivory (17)(18)(19). Alternatively, adding nutrients may have weak effects on β diversity if nutrients impact plant diversity through scale-independent processes such as host-pathogen interactions (20). In this context, three independent meta-analyses show that grassland plant diversity decline are proportional at local and larger spatial scales under nutrient addition (20)(21)(22). ...
... Alternatively, adding nutrients may have weak effects on β diversity if nutrients impact plant diversity through scale-independent processes such as host-pathogen interactions (20). In this context, three independent meta-analyses show that grassland plant diversity decline are proportional at local and larger spatial scales under nutrient addition (20)(21)(22). Besides these three key studies, many single-site experiments and a few multi-site experiments have investigated scale-dependent plant diversity change but often found mixed results, with vegetation homogenization (23)(24)(25), differentiation (21,(26)(27)(28)(29)(30)(31), or no effects all reported (32,33). ...
... We focus on species richness or Hill number (36) with q of 0 for this analysis, because species richness is the most commonly examined plant diversity metric (37). Extending our understanding of scale-dependent plant diversity change (20)(21)(22)32), we found that, overall, adding nutrients decreased α and γ diversity through time ( Alpha diversity is the average number of species over 3 blocks, gamma diversity is the total number of species across 3 blocks for each treatment at each site. Species are recorded within 1 × 1 m sampling units. ...
Plant diversity decline under nutrient addition in local grassland communities is typically ascribed to the loss of rare species, species with particular traits ill-suited for high nutrient levels, and displacement of many localized species with a few widespread species. Whether these changes result in stronger diversity decline and vegetation homogenization at larger spatial scales (aggregated local communities) remains largely unknown. Using a standardized replicated fertilization experiment in 70 grasslands on six continents, we found proportional species loss at local and larger spatial scales but no vegetation homogenization under nutrient addition. Moreover, nutrient addition drove proportional species loss across spatial scales irrespective of species abundance, provenance, life form, or distribution. These results demonstrate that nutrient addition poses a potential threat to all plant functional groups including widespread dominant species that may be critical for ecosystem functions and services.
One-Sentence Summary
Nutrient addition did not lead to biotic homogenization in experimental grasslands across the world.
... Several studies constructed SAR curves using a series of quadrats or transects with a single sampling origin and direction (Schrader et al., 2019;Dengler et al., 2020;Liu et al., 2020). For instance, each plot is strictly nested within the next larger plot and then these plots build SARs (Type I curves, Scheiner, 2003;Type A.a.i, Dengler, 2009) from a corner of the research area and then double the sampling area in a fixed direction (He et al., 1996;Keeley & Fotheringham, 2003;Seabloom et al., 2021). However, this method generally does not account for the effects of sampling origin and direction, which might bias the SARs and minimum sampling area estimates. ...
Questions
The minimum sampling area (minimum area) is the smallest space that reflects species composition and characteristics of a plant community. The quantitative concept of minimum area is often estimated using species–area relationships (SARs) and has become the classical foundation for managing protected areas. However, sampling designs to determine the minimum area in different forest types have not been systematically evaluated.
Location
China.
Methods
We used tree census data from three forest dynamic plots, each with a size of 25–60 ha, in different climatic zones in China to determine the minimum areas of woody plants and to analyze the effects of species richness and topographic heterogeneity on the minimum areas by changing sampling origin and direction.
Results
We found that mainly sampling design affects the estimation of woody plant species richness and required minimum area in different forest types. The estimated size of the minimum areas required was several hectares and varied significantly with sampling origin and direction, and showed a difference of approximately 1.5–2 times in the forest plots. Topographic heterogeneity significantly affected the minimum area through changes in species composition.
Conclusions
Sampling origin and direction should be considered when using SARs to estimate the minimum area and species diversity in communities. Such a comprehensive approach of sampling can contribute to a better understanding of vegetation characteristics and the minimum area required for a conservation census in heterogeneous environments.
... This increase in N availability is associated with a decline in species diversity, especially in grassland communities (Stevens et al. 2004, Harpole et al. 2016, Midolo et al. 2019, Band et al. 2022, Eskelinen et al. 2022. Moreover, the magnitude of diversity loss following N addition often increases with spatial scale (Seabloom et al. 2021, but see Lan et al. 2015) and can be irreversible (Isbell et al. 2013). Currently, N deposition is considered the third greatest driver of biodiversity loss worldwide after climate and land-use changes (Sala et al. 2000, Bobbink et al. 2010, Borer and Stevens 2022 So far, numerous N addition experiments have been conducted worldwide, showing that elevated N levels lead to species loss and decline of forbs and legumes (Bobbink et al. 2010, Soons et al. 2017, Midolo et al. 2019, Tognetti et al. 2021, Band et al. 2022. ...
... Our results agree with previous empirical studies in the region (DeMalach et al., 2017b) as well as places (Xia and Wan 2008, Bobbink et al. 2010, Maskell et al. 2010, Eskelinen and Harrison 2015, DeMalach et al. 2017a, Seabloom et al. 2021, Vázquez et al. 2022, showing that tall competitive grasses like Avena benefit from N enrichment while legumes and forbs decline. However, our findings further suggest that this reduction is driven by different processes, density-dependent mechanisms for forbs and density-independent mechanisms for legumes. ...
Nitrogen (N) deposition is a primary driver of species loss in plant communities globally. However, the mechanisms by which high N availability causes species loss remain unclear. Many hypotheses for species loss with increasing N availability highlight density-dependent mechanisms, i.e., changes in species interactions. However, an alternative set of hypotheses highlights density-independent detrimental effects of nitrogen (e.g., N toxicity). We tested the role of density-dependent and density-independent mechanisms in reducing species performance. For this aim, we used 120 experimental plant communities comprised of annual species growing together in containers under four fertilization treatments: (1) no nutrient addition(, (2) all nutrients except N (P, K, and micronutrients), (3) Low N, and (4) high N. Each fertilization treatment included two sowing densities to differentiate between the effects of competition (N * density interactions) and other detrimental effects of N. We focused on three performance attributes: the probability of reaching the reproduction period, biomass growth, and population growth. We found that individual biomass and population growth rates decreased with increasing sowing density in all nutrient treatments, implying that species interactions were predominantly negative. The common grass had a higher biomass and population growth under N enrichment, regardless of sowing density. In contrast, the legume showed a density-independent reduction in biomass growth with increasing N. Lastly, the small forb showed a density-dependent reduction in population growth, i.e., the decline occurred only under high density. Our results demonstrate that density-dependent and density-independent mechanisms operate simultaneously to reduce species performance under high N availability. Yet, their relative importance varies among species and life stages.
... Alternatively, a larger species pool, coupled with variation in dispersal among years, could drive higher colonization rates by nothing more than demographic stochasticity (assuming a relationship between site-and plot-level diversity; Hubbell, 2005;MacArthur & Wilson, 1967). It is probable that both of these explanations contribute to the relationship observed, though in a highly scale-dependent manner (Chisholm & Lichstein, 2009;Seabloom, Batzer, et al., 2021). Notably, this is contrary to expectations of other frameworks like the diversity-resistance hypothesis (Kennedy et al., 2002). ...
Declines in grassland diversity in response to nutrient addition are a general consequence of global change. This decline in species richness may be driven by multiple underlying processes operating at different time‐scales. Nutrient addition can reduce diversity by enhancing the rate of local extinction via competitive exclusion, or by reducing the rate of colonization by constraining the pool of species able to colonize under new conditions. Partitioning net change into extinction and colonization rates will better delineate the long‐term effect of global change in grasslands.
We synthesized changes in richness in response to experimental fertilization with nitrogen, phosphorus and potassium with micronutrients across 30 grasslands. We quantified changes in local richness, colonization, and extinction over 8–10 years of nutrient addition, and compared these rates against control conditions to isolate the effect of nutrient addition from background dynamics.
Total richness at steady state in the control plots was the sum of equal, relatively high rates of local colonization and extinction. On aggregate, 30%–35% of initial species were lost and the same proportion of new species were gained at least once over a decade. Absolute turnover increased with site‐level richness but was proportionately greater at lower‐richness sites relative to starting richness. Loss of total richness with nutrient addition, especially N in combination with P or K, was driven by enhanced rates of extinction with a smaller contribution from reduced colonization. Enhanced extinction and reduced colonization were disproportionately among native species, perennials, and forbs. Reduced colonization plateaued after the first few (<5) years after nutrient addition, while enhanced extinction continued throughout the first decade.
Synthesis. Our results indicate a high rate of colonizations and extinctions underlying the richness of ambient communities and that nutrient enhancement drives overall declines in diversity primarily by exclusion of previously established species. Moreover, enhanced extinction continues over long time‐scales, suggesting continuous, long‐term community responses and a need for long‐term study to fully realize the extinction impact of increased nutrients on grassland composition.
... Thanks to a great deal of previous work on the effect of nutrient deposition on ecological communities, and after over a decade of the Nutrient Network , we know that the more resources (Nitrogen, Phosphorus and Potassium) that are added to grasslands, the more species richness declines and the more aboveground biomass and productivity increases (Fay et al., 2015;Harpole et al., 2016). We also know that there is an increasing effect of chronic nutrient enrichment on plant diversity loss and ecosystem productivity over time and that species loss due to nutrient addition increases with spatial scale (Seabloom et al., 2021). Here, we use an updated data set that includes more sites and longer time series than in this previous work, so we analyse the relationship between the addition of multiple limiting nutrients (a combination of Nitrogen, Phosphorus and Potassium -NPK hereafter) on species richness over time and biomass over time as a reference point with this updated data set ( Figure S5 and Tables S2-S5). ...
... Additionally, some variation in site-level responses may be due to water limitation, and may account for some cases where nutrients do not affect biomass in very high and very low ends of the precipitation gradient represented here ( Figure S11). Additional mechanisms driving patterns within and across sites ( Figure S11) (Avolio et al., 2021), spatial scales Chase et al., 2019;Seabloom et al., 2021) and according to species' functional identities and characteristics (Crawford et al., 2021) could also be further investigated. We now know that the risk of a species being lost from a plot decreases with its abundance and varies across functional forms (Wilfahrt et al., 2021). ...
Global change drivers, such as anthropogenic nutrient inputs, are increasing globally. Nutrient deposition simultaneously alters plant biodiversity, species composition and ecosystem processes like aboveground biomass production. These changes are underpinned by species extinction, colonisation and shifting relative abundance. Here, we use the Price equation to quantify and link the contributions of species that are lost, gained or that persist to change in aboveground biomass in 59 experimental grassland sites. Under ambient (control) conditions, compositional and biomass turnover was high, and losses (i.e. local extinctions) were balanced by gains (i.e. colonisation). Under fertilisation, the decline in species richness resulted from increased species loss and decreases in species gained. Biomass increase under fertilisation resulted mostly from species that persist and to a lesser extent from species gained. Drivers of ecological change can interact relatively independently with diversity, composition and ecosystem processes and functions such as aboveground biomass due to the individual contributions of species lost, gained or persisting.
... As the population size of herbivorous insects becomes larger, shifts in species composition may play a more important role in regulating the population dynamics by changing host plant quality and quantity (Sassi et al., 2012;Song et al., 2018). In this case, the feeding preference of herbivorous insects may also in turn influence plant community composition (Kempel et al., 2015;Seabloom et al., 2021b). In addition, we found that the stimulation of P addition for leaf P content (175%) was far larger than the stimulation of N addition for leaf N content (27%), although the amount of P addition was a half of N addition. ...
Based on resource availability hypothesis, increasing exogenous nutrient inputs may favour herbivores by improving quality and quantity of host plants. Such plant-herbivore interactions have been demonstrated under nitrogen (N) addition, but less examined in the context of simultaneous inputs of N and phosphorus (P). Here, we conducted a multiple-nutrient addition experiment (Control, N addition alone, P addition alone, both N and P additions) in a Tibetan alpine grassland, to explore how N addition interacts with P to affect the larval density of the grassland caterpillar Gynaephora menyuanensis. We showed that P addition alone did not obviously affect the larval density, but P suppressed N-induced increases in larval density when N and P were simultaneously added. We further found that changes in leaf N:P of host plants induced by nutrient additions regulated larval density more strongly than leaf N or P content. Both increased plant productivity and shifted species composition under nutrient additions contributed less to the larval density. Interactive effects of N and P suggest that the simultaneous inputs of multiple nutrients may boost the carrying capacity of grasslands and reduce the risk of herbivorous insect outbreaks. The work also reveals that the resource availability hypothesis does not well predict the response of insect herbivore to all nutrient inputs, implying the necessity of incorporating N:P stoichiometry in this hypothesis.
... Studies have reported variable responses of diversity to grazing effects at different scales and it is possible that our results would differ if using larger sample sizes. However, a recent study using NutNet data found no consistent effects of fencing on species area relationships 46 . Adjacent to this subplot, aboveground biomass of all plants was clipped at ground level within two 1 × 0.1 m 2 strips. ...
Ecological models predict that the effects of mammalian herbivore exclusion on plant diversity depend on resource availability and plant exposure to ungulate grazing over evolutionary time. Using an experiment replicated in 57 grasslands on six continents, with contrasting evolutionary history of grazing, we tested how resources (mean annual precipitation and soil nutrients) determine herbivore exclusion effects on plant diversity, richness and evenness. Here we show that at sites with a long history of ungulate grazing, herbivore exclusion reduced plant diversity by reducing both richness and evenness and the responses of richness and diversity to herbivore exclusion decreased with mean annual precipitation. At sites with a short history of grazing, the effects of herbivore exclusion were not related to precipitation but differed for native and exotic plant richness. Thus, plant species’ evolutionary history of grazing continues to shape the response of the world’s grasslands to changing mammalian herbivory. A NutNet experiment in 57 grasslands across six continents shows that when herbivores are excluded from grasslands with a long coevolutionary history of grazing plant diversity is reduced, while in grasslands without a long grazing history the evolutionary history of the plant species regulates the response of plant diversity.
... Thanks to a great deal of previous work on the effect of nutrient deposition on ecological communities, and after over a decade of the Nutrient Network , we know that the more resources (Nitrogen, Phosphorus and Potassium) that are added to grasslands, the more species richness declines and the more aboveground biomass and productivity increases (Fay et al., 2015;Harpole et al., 2016). We also know that there is an increasing effect of chronic nutrient enrichment on plant diversity loss and ecosystem productivity over time and that species loss due to nutrient addition increases with spatial scale (Seabloom et al., 2021). Here, we use an updated data set that includes more sites and longer time series than in this previous work, so we analyse the relationship between the addition of multiple limiting nutrients (a combination of Nitrogen, Phosphorus and Potassium -NPK hereafter) on species richness over time and biomass over time as a reference point with this updated data set ( Figure S5 and Tables S2-S5). ...
... Additionally, some variation in site-level responses may be due to water limitation, and may account for some cases where nutrients do not affect biomass in very high and very low ends of the precipitation gradient represented here ( Figure S11). Additional mechanisms driving patterns within and across sites ( Figure S11) (Avolio et al., 2021), spatial scales Chase et al., 2019;Seabloom et al., 2021) and according to species' functional identities and characteristics (Crawford et al., 2021) could also be further investigated. We now know that the risk of a species being lost from a plot decreases with its abundance and varies across functional forms (Wilfahrt et al., 2021). ...
Global change drivers such as anthropogenic nutrient inputs simultaneously alter biodiversity, species composition, and ecosystem functions such as aboveground biomass. These changes are interconnected by complex feedbacks among extinction, colonization, and shifting relative abundance. Here, we use a novel temporal application of the Price equation to quantify the functional contributions of species that are lost, gained, and persist under ambient and experimental nutrient addition in 59 global grasslands. Under ambient conditions, compositional and biomass turnover was high, but species losses (i.e., local extinctions) were balanced by gains (i.e. colonization). There was biomass loss associated with species loss under fertilization. Few species were gained in fertilized conditions over time but those that were, and species that persisted, contributed to net biomass gains, outweighing biomass loss. These components of community change are key to understanding the relationship between change in composition, diversity and functioning.
... Additionally, some variation in site-level responses may be due to water limitation, and may account for some cases where nutrient induced species-loss does not affect biomass ( Figure S8). Opportunities also exist for future work to explore additional mechanisms driving patterns within and across sites ( Figure S8) (Avolioet al. 2021), spatial scales Barryet al. 2021;Seabloom et al. 2021), and according to species' identities and characteristics (Crawford et al. 2021). The risk of a species being lost from a plot decreases with its abundance in both space and time, and varies across lifespans and functional forms (Wilfahrt et al. 2021). ...
... Additionally, some variation in site-level responses may be due to water limitation, and may account for some cases where nutrient induced species-loss does not affect biomass ( Figure S8). Opportunities also exist for future work to explore additional mechanisms driving patterns within and across sites ( Figure S8) (Avolioet al. 2021), spatial scales Barryet al. 2021;Seabloom et al. 2021), and according to species' identities and characteristics (Crawford et al. 2021). The risk of a species being lost from a plot decreases with its abundance in both space and time, and varies across lifespans and functional forms (Wilfahrt et al. 2021). ...
Global change drivers such as anthropogenic nutrient inputs simultaneously alter biodiversity, species composition, and ecosystem functions such as above ground biomass. These changes are interconnected by complex feedbacks among extinction, invasion, and shifting relative abundance. Here, we use a novel temporal application of the Price equation to separate species richness and biomass change through time and quantify the functional contributions of species that are lost, gained, and persist under ambient and experimental nutrient addition in 59 global grasslands. Under ambient conditions, compositional and biomass turnover was high, but species losses (i.e., local extinctions) were balanced by gains (i.e. colonization). Under fertilization, there was biomass loss associated with species loss. Few species were gained in fertilized conditions over time but those that were, and species that persisted, contributed to net biomass gains, outweighing biomass loss. These components of community change are associated with distinct effects on measures of ecosystem functioning.
