ABSTRACT
Ever-growing human population and nutritional demands, supply chain disruptions, and advancing climate change have led to the realization that changes in diversity and system performance are ...intimately linked. Moreover, diversity and system performance depend on heterogeneity. Mitigating changes in system performance and promoting sustainable living conditions requires transformative decisions. Here, we introduce the heterogeneity–diversity–system performance (HDP) nexus as the conceptual basis upon which to formulate transformative decisions. We suggest that managing the heterogeneity of systems will best allow diversity to provide multiple benefits to people. Based on ecological theory, we pose that the HDP nexus is broadly applicable across systems, disciplines, and sectors, and should thus be considered in future decision making as a way to have a more sustainable global future.
This review paper suggests that managing the heterogeneity of systems will best allow diversity to provide multiple benefits to people. Based on ecological theory, we pose that the heterogeneity-diversity-performance nexus is broadly applicable across systems, disciplines, and sectors, and should thus be considered in future decision making as a way to have a more sustainable global future.
Understanding why species respond to climate change is critical for forecasting invasions, diversity, and productivity of communities. Although researchers often predict species’ distributions and ...productivity based on direct physiological responses to environments, theory suggests that striking shifts in community composition could arise if global change alters indirect feedbacks mediated by resources, mutualists, or antagonists. To test whether global change influences plant communities via soil‐mediated feedbacks, we grew model communities in soils collected from a seven‐year field manipulation of CO2, warming, and invasion. We evaluated mechanisms underlying variation in the model communities by comparing species’ growth in equivalent soil histories with, and without, experimentally reduced soil biota (via sterilization) and nutrient limitation (via fertilization). We show that grasses performed consistently across all soil history scenarios and that soil biota limited grasses more than nutrients. In contrast, forbs were differentially sensitive to soil history scenarios, with the magnitude and direction of responses to soil biota and nutrients dependent upon plant species and global change scenario. The asymmetry in importance of soil history for grasses and forbs is likely explained by differences in life history strategy. We conclude that accounting for species’ growth strategies will improve predictions of species sensitivity to altered soil feedbacks in future climates.
•We tested 5 dyes for bait-lamina stripes to improve precision of visual assessment.•Textile dye significantly increased the precision of visual assessment.•Textile dye and Easter Grass decomposed at ...similar rates as control substrate.•These two dyes had no detectable side effects on Collembola and soil microbes.•We recommend organic textile dye due to improved precision and easy handling.
Rapid ecosystem assessments are needed for large-scale ecotoxicological studies and coordinated distributed experiments. Bait-lamina stripes are commonly used as a standardized method to assess decomposer activity, but it is often difficult to distinguish bait substrate from soil. In the present study our aim was to identify a dyeing method that improves the precision of visual assessment of decomposition rates, while having negligible side effects. We compared five different dyes (food dye, Easter Grass, organic textile dye, ink, and wall paint) with control substrate in microcosms containing either acidic or alkaline soil with two introduced Collembola species (Folsomia candida and Sinellacoeca). Organic textile dye showed the highest precision of visual assessment, and had no detectable side effects on decomposition rates, soil microbial activity (biomass and respiration), or Collembola densities. We recommend using organic textile dye to improve the bait-lamina test due to the high precision and the ease of preparation.
Summary
Three common goals for restoration are (i) rapid plant establishment, (ii) long‐term plant persistence and (iii) restoration of functioning ecosystems. Restoration practitioners often use ...cultivars optimized for rapid plant establishment under highly disturbed conditions to achieve the first goal; locally adapted genotypes are championed for the second because they can be well suited for local environmental conditions. Restoring functioning ecosystems is considered a loftier goal that practitioners struggle to achieve because we lack proven techniques.
Similar to the demonstrated benefits of species, functional and phylogenetic diversity for ecosystem functions (EFs), recent genetic diversity (GD)–ecosystem function (EF) experiments have shown that increases in plant GD can positively influence many different EFs. Would the introduction of diverse plant genotypes of a given species into a restoration enhance ecosystem functioning and the evolutionary potential of restored populations?
In this review, we first examine three propagule‐sourcing approaches: cultivar, local adaptation and GD. Next, we raise questions that if addressed, could help practitioners implement a GD approach in restoration: (i) How might the selection, relatedness and arrangement of genotypes be optimized to restore functioning ecosystems, (ii) How do traits that affect an EF relate to neutral or adaptive diversity, more common measures of GD and (iii) at which spatial and temporal scales does GD influence EFs in restorations?
Synthesis and applications. Although each propagule‐sourcing approach may be best suited for a particular restoration goal, each approach may simultaneously benefit other goals. Yet cultivars and locally adapted populations that have experienced artificial and/or natural selection may not possess the levels of diversity that will confer expected benefits to different ecosystem functions. Future research should determine the relative value of each approach (or a combination of approaches) for simultaneously achieving multiple restoration goals. Restoration experiments, where plant genetic diversity (GD) is manipulated and monitored over scales relevant to restoration, could reveal the true promise of a GD approach to restoration.
Although each propagule‐sourcing approach may be best suited for a particular restoration goal, each approach may simultaneously benefit other goals. Yet cultivars and locally adapted populations that have experienced artificial and/or natural selection may not possess the levels of diversity that will confer expected benefits to different ecosystem functions. Future research should determine the relative value of each approach (or a combination of approaches) for simultaneously achieving multiple restoration goals. Restoration experiments, where plant genetic diversity (GD) is manipulated and monitored over scales relevant to restoration, could reveal the true promise of a GD approach to restoration.
Editor's Choice
Historically, terrestrial food web theory has been compartmentalized into interactions among aboveground or belowground communities. In this study we took a more synthetic approach to understanding ...food web interactions by simultaneously examining four trophic levels and investigating how nutrient (nitrogen and carbon) and detrital subsidies impact the ability of the belowground microbial community to alter the abundance of aboveground arthropods (herbivores and predators) associated with the intertidal cord grass Spartina alterniflora. We manipulated carbon, nitrogen, and detrital resources in a field experiment and measured decomposition rate, soil nitrogen pools, plant biomass and quality, herbivore density, and arthropod predator abundance. Because carbon subsidies impact plant growth only indirectly (microbial pathways), whereas nitrogen additions both directly (plant uptake) and indirectly (microbial pathways) impact plant primary productivity, we were able to assess the effect of both belowground soil microbes and nutrient availability on aboveground herbivores and their predators. Herbivore density in the field was suppressed by carbon supplements. Carbon addition altered soil microbial dynamics (net potential ammonification, litter decomposition rate, DON dissolved organic N concentration), which limited inorganic soil nitrogen availability and reduced plant size as well as predator abundance. Nitrogen addition enhanced herbivore density by increasing plant size and quality directly by increasing inorganic soil nitrogen pools, and indirectly by enhancing microbial nitrification. Detritus adversely affected aboveground herbivores mainly by promoting predator aggregation. To date, the effects of carbon and nitrogen subsidies on salt marshes have been examined as isolated effects on either the aboveground or the belowground community. Our results emphasize the importance of directly addressing the soil microbial community as a factor that influences aboveground food web structure by affecting plant size and aboveground plant nitrogen.
Upland salt marsh vegetation is particularly prone to habitat fragmentation and nutrient run-off due to coastal development and nearby agriculture. By examining how communities of sap-feeding insects ...respond to natural variation in plant-patch size and an experimental nutrient addition we explored how species with particular life history traits (e.g. dispersal ability and over-wintering style) might be used to indicate the effects of habitat fragmentation (patch area) and nitrogen subsidies on food webs. Sap-feeders that were superior dispersers or over-wintered in concealed microhabitats persisted well in small patch sizes. In contrast, species that were both immobile and over-wintered in exposed stages were more sensitive to decreasing patch size. Furthermore, mobile sap-feeders colonized and established populations on nitrogen-subsidized patches more rapidly than less mobile taxa. Thus, patterns in community composition (mobile vs. sedentary sap-feeders) can be used as key indicators of both habitat fragmentation and allochthanous nitrogen subsidies. Both patch size and nutrient subsidy altered trophic structure with a higher predator to herbivore ratio occurring in small compared to large patches and in control compared to nitrogen-subsidized habitats where herbivore outbreaks occurred. Our data suggest that conserving large habitat patches and minimizing nitrogen input is critical for maintaining sap-feeder diversity and preserving food-web structure.PUBLICATION ABSTRACT
Ecosystems world-wide experience changes in species composition in response to natural
and anthropogenic changes in environmental conditions. Research to date has
greatly improved our understanding ...of how species affect focal ecosystem functions.
However, because measurements of multiple ecosystem functions have not been consistently
justified for any given trophic group, it is unclear whether interpretations of
research syntheses adequately reflect the contributions of consumers to ecosystems.
Using model communities assembled in experimental microcosms, we examined the
relationship between four numerically dominant detritivore species and six ecosystem
functions that underpin fundamental aspects of carbon and nitrogen cycling aboveand
below-ground. We tested whether ecosystem responses to changes in detritivore
identity depended upon species trait dissimilarity, food web compartment (aboveground,
belowground, mixed) or number of responses considered (one to six). We
found little influence of detritivore species identity on brown (i.e. soil-based) processes.
Only one of four detritivore species uniquely influenced decomposition, and
detritivore species did not vary in their influence on soil nitrogen pools (NO3
− and
NH4
+), or root biomass. However, changes in detritivore identity influenced multiple
aboveground ecosystem functions. That is, by serving as prey, ecosystem engineers and
occasionally also as herbivores as well as detritivores, these species altered the strength
of aboveground predator–herbivore interactions and plant–shoot biomass. Yet, dissimilarity
of detritivore functional traits was not associated with dissimilarity of ecosystem
functioning. These results serve as an important reminder that consumers influence
ecosystem processes via multiple energy channels and that food web interactions set
important context for consumer-mediated effects on multiple ecosystem functions.
Given that species are being lost, gained and redistributed at unprecedented rates, we
can anticipate that changes in species identity will have additional ecosystem consequences
beyond those predicted by species’ primary functional role.
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