1. Recovering biological diversity and ecosystem functioning are primary objectives of ecological restoration, yet these outcomes are often unpredictable. Assessments based on functional traits may ...help with interpreting variability in both community composition and ecosystem functioning because of their mechanistic and generalizable nature. This promise remains poorly realized, however, because tests linking environmental conditions, functional traits, and ecosystem functioning in restoration are rare. 2. Here, we provide such a test through what is to our knowledge the first empirical application of the 'response-effect trait framework' to restoration. This framework provides a trait-based bridge between community assembly and ecosystem functioning by describing how species respond to environmental conditions based on traits and how the traits of species affect ecosystem functioning. 3. Our study took place across 29 prairies restored from former agricultural fields in southwestern Michigan. We considered how environmental conditions affect ecosystem functioning through and independently of measured functional traits. To do so, we paired field-collected trait data with data on plant community composition and measures of ecosystem functioning and used structural equation modelling to determine relationships between environmental conditions, community-weighted means of functional traits and ecosystem functioning. 4. Environmental conditions were predictive of trait composition. Sites restored directly from tillage (as opposed to those allowed to fallow) supported taller species with larger seeds and higher specific leaf area (SLA). Site age and fire frequency were both negatively related to SLA. We also found a positive relationship between soil moisture and SLA. 5. Both trait composition and environmental conditions predicted ecosystem functioning, but these relationships varied among the measured functions. Pollination mode (animal pollination) increased and fire frequency decreased floral resource availability, seed mass had a negative effect on below-ground biomass production, and vegetative height increased decomposition rate. Soil moisture and fire frequency both increased while site age decreased above-ground biomass production, and site age and soil moisture both increased decomposition rate. 6. Synthesis and applications. Our results suggest that both trait composition and environmental conditions play a role in shaping ecosystem function during restoration, and the importance of each is dependent on the function of interest. Because of this, environmental heterogeneity will be necessary to promote multiple ecosystem functions across restored landscapes. A trait-based approach to restoration can aid interpretation of variable outcomes through insights into community assembly and ecosystem functioning.
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There is strong evidence for a positive relationship between biodiversity and ecosystem functioning at local spatial scales. However, how different aspects of biodiversity relate to multiple ...ecosystem functions (multifunctionality) across heterogeneous landscapes, and how the magnitude of biodiversity, dominant species, and environmental effects on functioning compare, remain poorly understood. We compared relationships between plant phylogenetic, functional, and taxonomic diversity and ecosystem multifunctionality across 29 restored grasslands. Functional diversity was positively associated with multifunctionality, more strongly than other diversity measures; however, landscape composition explained nearly four times more variation in multifunctionality than did functional diversity, with plots within human-modified landscapes supporting lower multifunctionality. Individual functions were typically more strongly correlated with environmental variables than with diversity. We also found that abundance of the dominant species, Andropogon gerardii, was positively correlated with multifunctionality. Plant diversity, dominant species, and underlying environmental conditions underpin ecosystem multifunctionality in grasslands, but how biodiversity is measured matters for the strength and direction of biodiversity–ecosystem function relationships. Finally, in natural systems environmental variation unrelated to local biodiversity is important for determining ecosystem functioning.
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Understanding priority effects, in which one species in a habitat decreases the success of later species, may be essential for restoring native communities. Priority effects can operate in two ways: ...size‐asymmetric competition and creation of “soil legacies,” effects on soil that may last long after the competitive effect. We examined how these two types of priority effects, competition and soil legacies, drive interactions between seedlings of native and exotic California grassland plants. We established native and exotic communities in a mesocosm experiment. After 5 weeks, we removed the plants from half the treatments (soil legacy treatment) and retained the plants in the other half (priority effect treatment, which we interpret to include both competition and soil legacies). We then added native or exotic seed as the colonizing community. After 2 months, we measured the biomass of the colonizing community. When germinating first, both natives and exotics established priority effects, reducing colonist biomass by 86 and 92%, respectively. These priority effects were predominantly due to size‐asymmetric competition. Only exotics created soil legacies, and these legacies only affected native colonizers, reducing biomass by 74%. These results imply that exotic species priority effects can affect native grassland restorations. Although most restorations focus on removing exotic seedlings, amending soil to address soil legacies may also be critical. Additionally, because native species can exclude exotics if given a head start, ensuring that natives germinate first may be a cost‐effective restoration technique.
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Ecology Letters (2010) 13: 1400-1410 ABSTRACT: Stability in ecosystem function is an important but poorly understood phenomenon. Anthropogenic perturbations alter communities, but how they change ...stability and the strength of stabilizing mechanisms is not clear. We examined temporal stability (invariability) in aboveground productivity in replicated 18‐year time series of experimentally perturbed grassland plant communities. We found that disturbed annual‐dominated communities were more stable than undisturbed perennial communities, coincident with increases in the stabilizing effect of mean-variance scaling. We also found that nitrogen‐fertilized communities maintained stability despite losses in species richness, probably because of increased compensatory dynamics and increased dominance by particularly stable dominant species. Among our communities, slight variation in diversity was not the strongest mechanism driving differences in stability. Instead, our study suggests that decreases in individual species variabilities and increases in the relative abundance of stable dominant species may help maintain stability in the functioning of ecosystems confronted with eutrophication, disturbance, and other global changes.
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Theory suggests that cheaters threaten the persistence of mutualisms, but that sanctions to prevent cheating can stabilize mutualisms. In the arbuscular mycorrhizal symbiosis, reports of parasitism ...suggest that reductions in plant carbon allocation are not universally effective. I asked whether plant species differences in mycorrhizal responsiveness would affect both their susceptibility to parasitism and their reduction in allocation to non-beneficial arbuscular mycorrhizal fungi (AMF) in high-phosphorus soils. In a greenhouse experiment, I found that two C
3
grasses,
Bromus inermis
and
Elymus repens
, effectively suppressed root colonization and AMF hyphal abundance. Increases in soil phosphorus did not reduce the degree to which AMF increased plant biomass. In contrast, two C
4
grasses,
Andropogon gerardii
and
Schizachyrium scoparium
, more weakly reduced root colonization and failed to suppress AMF hyphal abundance. Consequently, they experienced strong declines in their response to AMF, and one species suffered parasitism. Thus, species differ in susceptibility to parasitism and their reduction in allocation to non-beneficial AMF. These differences may affect the distribution and abundance of plants and AMF, as well as the stability of the mutualism.
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A central goal of ecological restoration is to promote diverse ecosystems dominated by native species, but restorations are often plagued by exotic species. A better understanding of factors ...underlying positive correlations between native and exotic species richness, a pattern that is nearly ubiquitous at large scales in plant communities, may help managers modify these correlations to favor native plant species during restoration. Across 29 tallgrass prairie sites restored through seed sowing onto former agricultural lands, we examined whether the relationship between native and exotic richness is (1) altered by management, such as seed additions and prescribed fire; (2) controlled instead by environmental conditions and successional processes; or (3) altered by management in certain environments and not in others. As is commonly found, native and exotic richness were positively correlated at large scales (i.e., across sites) in this study. Management actions explained much of the remaining variation in native richness, while environmental conditions explained very little. Sites sown with more species at higher seeding rates, especially forb species, had higher native richness than predicted by the native–exotic richness relationship. In contrast, native richness was lower in older restorations than predicted by the native–exotic richness relationship, because native richness, and not exotic richness, declined with restoration age. We show that management actions such as seed sowing can modify the native–exotic richness relationship to favor native species during restoration. The development of management actions that mitigate native species richness declines over time will further benefit native species restoration.
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Global change is impacting plant community composition, but the mechanisms underlying these changes are unclear. Using a dataset of 58 global change experiments, we tested the five fundamental ...mechanisms of community change: changes in evenness and richness, reordering, species gains and losses. We found 71% of communities were impacted by global change treatments, and 88% of communities that were exposed to two or more global change drivers were impacted. Further, all mechanisms of change were equally likely to be affected by global change treatments—species losses and changes in richness were just as common as species gains and reordering. We also found no evidence of a progression of community changes, for example, reordering and changes in evenness did not precede species gains and losses. We demonstrate that all processes underlying plant community composition changes are equally affected by treatments and often occur simultaneously, necessitating a wholistic approach to quantifying community changes.
Synthesising community responses to global change driver treatments is necessary to make predictions of future communities. Across 219 control–treatment comparisons, we find that communities are consistently being impacted by global change treatments, and multiple resource treatments result in the greatest community changes. However, communities are changing in many ways, and there is no ordered progression to these changes.
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By definition, mutualisms involve the exchange of goods or services between partners. It has been shown that mutualism can grade into parasitism, but even when exchange is mutually beneficial, a ...conflict of interest remains because each partner benefits from reaping more benefits at a lower cost. Metaphorically, the partners negotiate the conditions of trade, the outcome of which will determine the net benefit to each partner. Each partner can adjust its allocation to self-provisioning while negotiating the ratio at which benefits are exchanged. To understand how these two features of trade affect mutualisms, we used the example of the plant–arbuscular mycorrhizal mutualism and modeled uptake and trade of two resources, phosphorus and carbon. In most contexts, the fungus specialized on phosphorus uptake while the plant took up both phosphorus and carbon. However, when phosphorus was abundant and light was scarce, the plant specialized, taking up only carbon and relying on trade for phosphorus. Resource availability was the most important factor determining specialization and the outcome of negotiation and trade, but other aspects of the context were also important. These results suggest experiments to link these two key features of trade with environmental conditions to determine the outcome of mutualism.
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Abstract In our changing world, understanding plant community responses to global change drivers is critical for predicting future ecosystem composition and function. Plant functional traits promise ...to be a key predictive tool for many ecosystems, including grasslands; however, their use requires both complete plant community and functional trait data. Yet, representation of these data in global databases is sparse, particularly beyond a handful of most used traits and common species. Here we present the CoRRE Trait Data, spanning 17 traits (9 categorical, 8 continuous) anticipated to predict species’ responses to global change for 4,079 vascular plant species across 173 plant families present in 390 grassland experiments from around the world. The dataset contains complete categorical trait records for all 4,079 plant species obtained from a comprehensive literature search, as well as nearly complete coverage (99.97%) of imputed continuous trait values for a subset of 2,927 plant species. These data will shed light on mechanisms underlying population, community, and ecosystem responses to global change in grasslands worldwide.
Agricultural land use commonly leaves a persistent signature on the ecosystems that develop after agricultural abandonment. This agricultural legacy limits the biodiversity supported by ...post-agricultural habitats compared to remnant habitats that have never been used for agriculture. In particular, beta diversity (variation in community composition across space) at both large and small spatial scales can differ between post-agricultural and remnant habitats, but we do not understand the mechanisms driving these differences. We surveyed plant communities at 29 pairs of post-agricultural and remnant longleaf pine woodlands (58 total woodlands) to test for patterns consistent with two hypothesized mechanisms for why post-agricultural ecosystems support altered beta diversity. 1) Post-agricultural sites support different levels of underlying environmental heterogeneity than remnants. 2) Establishment of species associated with remnant habitats into post-agricultural woodlands is limited by dispersal and/or environmental conditions. We found no support for the environmental heterogeneity hypothesis and strong support for the idea that species establishment limits reassembling communities. Our results revealed a novel and important nuance to the establishment limitation hypothesis: spatially constrained, but not completely prevented, re-establishment of remnant-associated species in post-agricultural woodlands increased within-site beta diversity, contrary to results at larger among-site (landscape) scales. Our use of a powerful paired-site design permits these insights into how agriculture and abandonment affect beta diversity at two spatial scales, highlighting the prominent influence of edges even a half century after agricultural abandonment. The importance of constrained species establishment during ecosystem recovery, and its scale-dependent effect, could provide valuable guidance to enhance the utility of post-agricultural habitats for biodiversity conservation.
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