Multiple Global Change Drivers Research Articles

Plant diversity and grasses increase root biomass in a rainfall and grassland diversity manipulation

The loss of plant productivity with declining diversity is well established, exceeding other global change drivers including drought. These patterns are most clearly established for aboveground productivity, it remains poorly understood whether productivity increases associated with diversity are replicated belowground. To address this gap, we established a plant diversity-manipulation experiment in 2018. It is a full factorial manipulation of plant species richness and community composition, and precipitation. Three and five years post-establishment, two bulk soil cores (20cm depth) were collected and composited from each plot and were processed for roots to determine belowground biomass as root standing crop. We observed a strong positive relationship between richness and aboveground production and belowground biomass, generating positive combined above and belowground with diversity. Root standing crop increased 1.4-fold from years three to five. Grass communities produced more root biomass (monoculture mean 463.9 ± 410.3g m−2), and the magnitude of the relationship between richness and root standing crop was greatest within those communities. Legume communities produced the fewest roots (monoculture mean 212.2 ± 155.1g m−2), and belowground standing crop was not affected by diversity. Root standing crops in year three were 1.8 times higher under low precipitation conditions, while in year five we observed comparable root standing crops between precipitation treatments. Plant family was a strong mediator of increased belowground biomass observed with diversity, with single family grass and aster families generating 1.7 times greater root standing crops in six compared to single species communities, relationships between diversity and aboveground production were consistently observed in both single-family and multiple family communities. Diverse communities with species from multiple families generated only 1.3 times the root standing crop compared to monoculture average root biomass. We surprisingly observe diverse single family communities can generate increases in root standing crops that exceed those generated by diverse multiple family communities, highlighting the importance of plant richness within plant family for a given community. These patterns have potential implications for understanding the interactions of multiple global change drivers as changes in both precipitation and plant community composition do alter whether plant production aboveground is translated belowground biomass.

Synergistic effects of multiple global change drivers on terrestrial ecosystem carbon sink

Multiple global change drivers typically co-occur in terrestrial ecosystems, usually with complex interactions on ecosystem carbon fluxes. However, how they interactively impact terrestrial carbon sinks remains unknown. Here, we synthesized 82 field experiments that studied the individual and pairwise effects among nitrogen addition (N), increased precipitation (IP), elevated CO2 (eCO2) and warming, with direct measurements of net ecosystem productivity (NEP), gross ecosystem productivity (GEP) and ecosystem respiration (ER). We found that synergistic interactions mostly occurred between pairs of global change drivers on carbon fluxes. Moreover, these interactions varied with treatment magnitude, experimental duration and background precipitation. Specifically, the synergistic effect of N × IP became stronger with experimental precipitation magnitude and background rainfall. With an increasing N addition rate, N and eCO2 had weaker interactive effects on NEP. Warming and IP were more synergic to enhance NEP with higher levels of warming magnitude. However, the interactive effects of N × eCO2 on ER decreased over the experimental duration. Overall, this study provides new insights into the context-dependent occurrence of interactions among multiple global change drivers on ecosystem carbon sinks. These new findings are valuable to validate land C-cycle models with complex global change interactions and advance the next generations of future experimental design.

Different facets of the same niche: Integrating citizen science and scientific survey data to predict biological invasion risk under multiple global change drivers.

Citizen science initiatives have been increasingly used by researchers as a source of occurrence data to model the distribution of alien species. Since citizen science presence-only data suffer from some fundamental issues, efforts have been made to combine these data with those provided by scientifically structured surveys. Surprisingly, only a few studies proposing data integration evaluated the contribution of this process to the effective sampling of species' environmental niches and, consequently, its effect on model predictions on new time intervals. We relied on niche overlap analyses, machine learning classification algorithms and ecological niche models to compare the ability of data from citizen science and scientific surveys, along with their integration, in capturing the realized niche of 13 invasive alien species in Italy. Moreover, we assessed differences in current and future invasion risk predicted by each data set under multiple global change scenarios. We showed that data from citizen science and scientific surveys captured similar species niches though highlighting exclusive portions associated with clearly identifiable environmental conditions. In terrestrial species, citizen science data granted the highest gain in environmental space to the pooled niches, determining an increased future biological invasion risk. A few aquatic species modelled at the regional scale reported a net loss in the pooled niches compared to their scientific survey niches, suggesting that citizen science data may also lead to contraction in pooled niches. For these species, models predicted a lower future biological invasion risk. These findings indicate that citizen science data may represent a valuable contribution to predicting future spread of invasive alien species, especially within national-scale programmes. At the same time, citizen science data collected on species poorly known to citizen scientists, or in strictly local contexts, may strongly affect the niche quantification of these taxa and the prediction of their future biological invasion risk.

Climate warming interacts with other global change drivers to influence plant phenology: A meta-analysis of experimental studies.

Shifts in plant phenology influence ecosystem structures and functions, yet how multiple global change drivers interact to affect phenology remains elusive. We conducted a meta-analysis of 242 published articles to assess interactions between warming (W) and other global change drivers including nitrogen addition (N), increased precipitation (IP), decreased precipitation (DP) and elevated CO2 (eCO2 ) on multiple phenophases in experimental studies. We show that leaf out and first flowering were most strongly affected by warming, while warming and decreased precipitation were the most pronounced drivers for leaf colouring. Moreover, interactions between warming and other global change drivers were common and both synergistic and antagonistic interactions were observed: interactions W + IP and W + eCO2 were frequently synergistic, whereas interactions W + N and W + DP were mostly antagonistic. These findings demonstrate that global change drivers often affect plant phenology interactively. Incorporating the multitude of interactions into models is crucial for accurately predicting plant responses to global changes.

Exposure to extremes in multiple global change drivers: Characterizing pH, dissolved oxygen, and temperature variability in a dynamic, upwelling dominated ecosystem

ABSTRACTIn upwelling systems, fluctuations in seawater pH, dissolved oxygen (DO), and temperature can expose species to extremes that differ greatly from the mean conditions. Understanding the nature of this exposure to extremes, including how exposure to low pH, low DO concentrations, and temperature varies spatiotemporally and in the context of other drivers, is critical for informing global change biology. Here, we use a 4‐yr time series of coupled pH, DO, and temperature observations at six nearshore kelp forest sites spanning the coast of California to characterize the variability and covariance among these drivers. We further compare observed properties to those derived from a high‐resolution coupled physical‐biogeochemical simulation for the central California current system. We find the intensity, duration, and severity of exposure to extreme conditions beyond heuristic, biologically relevant pHT (< 7.7), and DO (< 4.6 mg L−1) values were greatest at sites with strong upwelling. In contrast, sites with relatively weaker upwelling had little exposure to pH or DO conditions below these heuristic values but had higher and more variable temperature. The covariance between pH, DO, and temperature was highest in sites with strong upwelling and weakest in sites with limited upwelling. These relationships among pH, DO, and temperature at the observation locations were mirrored in the model, and model output highlighted geographic differences in exposure regimes across the California marine protected area network. Together, these results provide important insight into the conditions marine ecosystems are exposed to relevant to studies of global change biology.

Disturbance alters transience but nutrients determine equilibria during grassland succession with multiple global change drivers.

Disturbance and environmental change may cause communities to converge on a steady state, diverge towards multiple alternative states or remain in long-term transience. Yet, empirical investigations of successional trajectories are rare, especially in systems experiencing multiple concurrent anthropogenic drivers of change. We examined succession in old field grassland communities subjected to disturbance and nitrogen fertilization using data from a long-term (22-year) experiment. Regardless of initial disturbance, after a decade communities converged on steady states largely determined by resource availability, where species turnover declined as communities approached dynamic equilibria. Species favoured by the disturbance were those that eventually came to dominate the highly fertilized plots. Furthermore, disturbance made successional pathways more direct revealing an important interaction effect between nutrients and disturbance as drivers of community change. Our results underscore the dynamical nature of grassland and old field succession, demonstrating how community properties such as diversity change through transient and equilibrium states.

Fuel connectivity, burn severity, and seed bank survivorship drive ecosystem transformation in a semiarid shrubland.

A key challenge in ecology is understanding how multiple drivers interact to precipitate persistent vegetation state changes. These state changes may be both precipitated and maintained by disturbances, but predicting whether the state change will be fleeting or persistent requires an understanding of the mechanisms by which disturbance affects the alternative communities. In the sagebrush shrublands of the western United States, widespread annual grass invasion has increased fuel connectivity, which increases the size and spatial contiguity of fires, leading to postfire monocultures of introduced annual grasses (IAG). The novel grassland state can be persistent and is more likely to promote large fires than the shrubland it replaced. But the mechanisms by which prefire invasion and fire occurrence are linked to higher postfire flammability are not fully understood. A natural experiment to explore these interactions presented itself when we arrived in northern Nevada immediately after a 50,000 ha wildfire was extinguished. We hypothesized that the novel grassland state is maintained via a reinforcing feedback where higher fuel connectivity increases burn severity, which subsequently increases postfire IAG dispersal, seed survivorship, and fuel connectivity. We used a Bayesian joint species distribution model and structural equation model framework to assess the strength of the support for each element in this feedback pathway. We found that prefire fuel connectivity increased burn severity and that higher burn severity had mostly positive effects on the occurrence of IAG and another nonnative species and mostly negative or neutral relationships with all other species. Finally, we found that the abundance of IAG seeds in the seed bank immediately after a fire had a positive effect on the fuel connectivity 3 years after the fire, completing a positive feedback promoting IAG. These results demonstrate that the strength of the positive feedback is controlled by measurable characteristics of ecosystem structure, composition, and disturbance. Further, each node in the loop is affected independently by multiple global change drivers. It is possible that these characteristics can be modeled to predict threshold behavior and inform management actions to mitigate or slow the establishment of the grass-fire cycle, perhaps via targeted restoration applications or prefire fuel treatments.

Predicting effects of multiple interacting global change drivers across trophic levels.

Global change encompasses many co-occurring anthropogenic drivers, which can act synergistically or antagonistically on ecological systems. Predicting how different global change drivers simultaneously contribute to observed biodiversity change is a key challenge for ecology and conservation. However, we lack the mechanistic understanding of how multiple global change drivers influence the vital rates of multiple interacting species. We propose that reaction norms, the relationships between a driver and vital rates like growth, mortality, and consumption, provide insights to the underlying mechanisms of community responses to multiple drivers. Understanding how multiple drivers interact to affect demographic rates using a reaction-norm perspective can improve our ability to make predictions of interactions at higher levels of organization-that is, community and food web. Building on the framework of consumer-resource interactions and widely studied thermal performance curves, we illustrate how joint driver impacts can be scaled up from the population to the community level. A simple proof-of-concept model demonstrates how reaction norms of vital rates predict the prevalence of driver interactions at the community level. A literature search suggests that our proposed approach is not yet used in multiple driver research. We outline how realistic response surfaces (i.e., multidimensional reaction norms) can be inferred by parametric and nonparametric approaches. Response surfaces have the potential to strengthen our understanding of how multiple drivers affect communities as well as improve our ability to predict when interactive effects emerge, two of the major challenges of ecology today.

Multiple global change drivers show independent, not interactive effects: a long-term case study in tallgrass prairie.

Ecosystems are faced with an onslaught of co-occurring global change drivers. While frequently studied independently, the effects of multiple global change drivers have the potential to be additive, antagonistic, or synergistic. Global warming, for example, may intensify the effects of more variable precipitation regimes with warmer temperatures increasing evapotranspiration and thereby amplifying the effect of already dry soils. Here, we present the long-term effects (11 years) of altered precipitation patterns (increased intra-annual variability in the growing season) and warming (1°Cyear-round) on plant community composition and aboveground net primary productivity (ANPP), a key measure of ecosystem functioning in mesic tallgrass prairie. Based on past results, we expected that increased precipitation variability and warming would have additive effects on both community composition and ANPP. Increased precipitation variability altered plant community composition and increased richness, with no effect on ANPP. In contrast, warming decreased ANPP via reduction in grass stems and biomass but had no effect on the plant community. Contrary to expectations, across all measured variables, precipitation and warming treatments had no interactive effects. While treatment interactions did not occur, each treatment did individually impact a different component of the ecosystem (i.e., community vs. function). Thus, different aspects of the ecosystem may be sensitive to different global change drivers in mesic grassland ecosystems.

Influence of multiple global change drivers on plant invasion: Additive effects are uncommon.

Invasive plants threaten biodiversity and cause huge economic losses. It is thought that global change factors (GCFs) associated with climate change (including shifts in temperature, precipitation, nitrogen, and atmospheric CO2) will amplify their impacts. However, only few studies assessed mixed factors on plant invasion. We collated the literature on plant responses to GCFs to explore independent, combined, and interactive effects on performance and competitiveness of native and invasive plants. From 176 plant species, our results showed that: (1) when native and invasive plants are affected by both independent and multiple GCFs, there is an overall positive effect on plant performance, but a negative effect on plant competitiveness; (2) under increased precipitation or in combination with temperature, most invasive plants gain advantages over natives; and (3) interactions between GCFs on plant performance and competitiveness were mostly synergistic or antagonistic. Our results indicate that native and invasive plants may be affected by independent or combined GCFs, and invasive plants likely gain advantages over native plants. The interactive effects of factors on plants were non-additive, but the advantages of invasive plants may not increase indefinitely. Our findings show that inferring the impacts of climate change on plant invasion from factors individually could be misleading. More mixed factor studies are needed to predict plant invasions under global change.

Net effect of environmental fluctuations in multiple global-change drivers across the tree of life

Jensen's inequality predicts that the response of any given system to average constant conditions is different from its average response to varying ones. Environmental fluctuations in abiotic conditions are pervasive on Earth; yet until recently, most ecological research has addressed the effects of multiple environmental drivers by assuming constant conditions. One could thus expect to find significant deviations in the magnitude of their effects on ecosystems when environmental fluctuations are considered. Drawing on experimental studies published during the last 30 years reporting more than 950 response ratios (n = 5,700), we present a comprehensive analysis of the role that environmental fluctuations play across the tree of life. In contrast to the predominance of interactive effects of global-change drivers reported in the literature, our results show that their cumulative effects were additive (58%), synergistic (26%), and antagonistic (16%) when environmental fluctuations were present. However, the dominant type of interaction varied by trophic level (autotrophs: interactive; heterotrophs: additive) and phylogenetic group (additive in Animalia; additive and positive antagonism in Chromista; negative antagonism and synergism in Plantae). In addition, we identify the need to tackle how complex communities respond to fluctuating environments, widening the phylogenetic and biogeographic ranges considered, and to consider other drivers beyond warming and acidification as well as longer timescales. Environmental fluctuations must be taken into account in experimental and modeling studies as well as conservation plans to better predict the nature, magnitude, and direction of the impacts of global change on organisms and ecosystems.

Predicting the effects of multiple global change drivers on microbial communities remains challenging.

Microbial communities in many ecosystems are facing a broad range of global change drivers, such as nutrient enrichment, chemical pollution, and temperature change. These drivers can cause changes in the abundance of taxa, the composition of communities, and the properties of ecosystems. While the influence of single drivers is already described in numerous studies, the effect and predictability of multiple drivers changing simultaneously is still poorly understood. In this study, we used 240 highly replicable oxic/anoxic aquatic lab microcosms and four drivers (fertilizer, glyphosate, metal pollution, antibiotics) in all possible combinations at three different temperatures (20, 24, and 28°C) to shed light into consequences of multiple drivers on different levels of organization, ranging from species abundance to community and ecosystem parameters. We found (i) that at all levels of ecological organization, combinations of drivers can change the biological consequence and direction of effect compared to single drivers, (ii) that effects of combinations are further modified by temperature, (iii) that a larger number of drivers occurring simultaneously is often quite closely related to their effect size, and (iv) that there is little evidence that any of these effects are associated with the level of ecological organization of the state variable. These findings suggest that, at least in this experimental ecosystem approximating a stratified aquatic ecosystem, there may be relatively little scope for predicting the effects of combinations of drivers from the effects of individual drivers, or by accounting for the level of ecological organization in question, though there may be some scope for prediction based on the number of drivers that are occurring simultaneous. A priority, though also a considerable challenge, is to extend such research to consider continuous variation in the magnitude of multiple drivers acting together.

Global soil organic carbon–climate interactions: Why scales matter

AbstractSoil organic carbon (SOC) holds the largest terrestrial carbon stock because of soil conditions and processes that favor soil carbon persistence. Vulnerable to climate change, SOC may cross a tipping point toward liberating carbon‐based greenhouse gases, implying massive self‐amplifying SOC‐ climate interactions. Estimates of SOC persistence are challenging as we still lack broad mechanistic insights. Upscaling mechanistic details from small to larger scales is challenging because the driving factors are not available at the needed resolution. Downscaling is problematic as many modeling studies point to the highest uncertainties deriving from the SOC response to climate change, while models themselves have difficulties in replicating contemporary soil properties and dynamics. To bridge the problems of scaling, strict process orientation seems adequate. Holdridge Life Zones (HLZ) classification, as one example, is a climate classification framework at a mesoscale that provides a descriptive approach to facilitate the identification of potential hotspots and coldspots of SOC‐climate interaction. Establishing coordinated experiments across all HLZ, but also including multiple global change drivers, has the potential to advance our understanding of general principles regulating SOC‐climate interaction and SOC persistence. Therefore, regionally tailored solutions for both experiments and modeling are urgently needed and can lead to better management of soil and the ecosystem services provided. Improving “translations” from the scales relevant for process understanding to the scales of decision‐making is key to good management and to predict the fate of our largest terrestrial carbon stock.This article is categorized under: Integrated Assessment of Climate Change > Integrated Scenario Development

Climatic conditions and functional traits affect spider diets in agricultural and non‐agricultural habitats worldwide

Spiders are dominant predators in terrestrial ecosystems and feed on prey from the herbivore and detritivore subsystem (dual subsystem omnivory) as well as on other predators (intraguild predation). Little is known about how global change potentially affects the importance of different prey groups in predator diets. In this meta‐analysis we identify the impact of climatic conditions, land‐use types and functional traits of spider species on the relative importance of Hemiptera, Araneae and Collembola prey in spider diets. We use a dataset including 78 publications with 149 observational records of the diet composition of 96 spider species in agricultural and non‐agricultural habitats in 24 countries worldwide. The importance of Hemiptera prey was not affected by climatic conditions and was particularily high in smaller spider species in agricultural habitats. Araneae prey was most important for actively hunting, larger spider species in non‐agricultural habitats. Collembola prey was most important for small, actively hunting spider species in regions with higher temperature seasonality. Spider species with a higher importance of Araneae prey for their diet also had higher importances of Collembola and lower importances of Hemiptera prey. Future increases of temperature seasonality predicted for several regions worldwide may go along with an increasing importance of Collembola prey which also related to a higher importance of intraguild prey here. Two global change drivers predicted for many regions of the world (increasing climatic seasonality and ongoing conversion of non‐agricultural to agricultural land) both hold the potential to increase the importance of Collembola prey in spider diets. The importance of Hemiptera and Araneae prey may however show contrasting responses to these two drivers. These complex potential effects of global change components and their impact on functional traits in spider communities highlight the importance to simultaneously consider multiple drivers of global change to better understand future predator–prey interactions.

Drivers of Ecological and Evolutionary Disruptions in the Seed Dispersal Process: Research Trends and Biases

As the sole opportunity for most plants to move, seed dispersal influences the biodiversity and functioning of plant communities. Global change drivers have the potential to disrupt seed dispersal processes, affecting plant communities and ecosystem functions. Even though much information is available on the effects of seed dispersal disruption (SDD), we still lack a comprehensive understanding of its main causes at a global scale, as well as the potential knowledge gaps derived from research biases. Here we present a systematic review of biotic and abiotic SDDs to ascertain the global change drivers addressed, dispersal modes impacted, plant processes affected, and spatial focus of existing research on this topic up-to-date. Although there are many modes of dispersal and global change drivers in temperate and tropical ecosystems worldwide, research efforts have predominantly addressed the effect of alien species for biotic seed dispersal in temperate systems and oceanic islands as well as how defaunation of bird or mammal dispersers has affected seed removal in the Neotropics. SDD studies were also biased toward forest ecosystems, with few in shrublands or grasslands. Finally, the effects of climate change, ecological consequences at the whole community level, and evolutionary changes were largely unrepresented in SDD studies. These trends are likely due to a combination of true geographic and ecological patterns in seed dispersal and global change and bias in research focus. We conclude that increased research investment in the less-studied systems and a better understanding of potential synergies and feedback between multiple global change drivers will be important to forecast the threats to plant biodiversity and those ecosystem functions derived from seed dispersal in the Anthropocene.

Future climate and land-use intensification modify arthropod community structure

Climate change and land-use intensification pose increasing threats to biodiversity, with climate change expected to eventually surpass other global environmental change drivers and become the greatest threat to biodiversity in the future. Understanding the combined ecological impacts of multiple global change drivers is crucial to predict future scenarios of biodiversity change. However, experimental evidence for the impacts of land-use intensification under current and future climate scenarios is lacking, even though this is imperative for understanding future trajectories of biodiversity in agricultural landscapes. We experimentally tested for the simultaneous effects of land-use intensification and climate change on arthropod biodiversity in a field-scale grassland experiment known as the Global Change Experimental Facility (GCEF). Specifically, we tested whether future scenarios of climate change are likely to exacerbate impacts of land-use intensification on arthropod diversity and abundance across different trophic levels by sampling aboveground arthropod communities in low and high land-use intensity grasslands under current and future climatic conditions. We found that climate change reduced total abundances of arthropods and increased evenness of the whole community, while only having trophic level-specific effects on detritivore abundance and evenness. Land-use intensification reduced abundance of the whole community, predators and detritivores, but only eroded species richness of the whole community and herbivores, with the magnitude of declines in predator and detritivore abundance depending on the climate scenario. Additionally, both land-use intensification and climate altered species composition of the whole community and within the predator, herbivore, and detritivore trophic levels. We show that climate change and land use intensification cause simultaneous shifts in arthropod abundance, species richness, and species composition across trophic levels. Changes in arthropod communities as a result of climate change and land-use intensification will likely have profound consequences for ecosystem functioning under future environmental conditions.

Precipitation changes, warming, and N input differentially affect microbial predators in an alpine meadow: Evidence from soil phagotrophic protists

Soil phagotrophic protists are highly abundant and play a vital role in nutrient cycling through feeding on microbes. Global change factors, individually or in combination, often affect soil bacteria and fungi, but whether and how the resulting changes may cascade to affect phagotrophic protists remain largely unknown. Combining direct microscopic counting and high-throughput sequencing of 18s rRNA gene, we examined effects of precipitation changes, warming and nitrogen (N) input on soil phagotrophic protists in a 3-yr manipulation experiment with a Tibetan alpine meadow. Precipitation addition (+30%) enhanced but precipitation reduction (−30%) and warming decreased the alpha diversity of phagotrophic protists, primarily through altering soil moisture. However, N input (12 g N m−2 y−1) increased protist abundance, and in particular, offset the negative effect of precipitation reduction on the relative abundance of phagotrophic protists through increasing the microbial biomass, implying a bottom-up trophic control. Together, these findings indicate that interactions of multiple global change drivers may affect soil protist communities directly by modifying the soil physiochemical environment and indirectly through trophic cascading, which have implications for the potential changes in their ecosystem functions in alpine meadow under future global change scenarios.

A framework linking biogeography and species traits to plant species vulnerability under global change in Mediterranean-type ecosystems

We review the roles that plant species traits and biogeography play in species’ exposure and vulnerability to decline or extinction under global change, focusing on separate and combined impacts of multiple threats – climate change, land-use change, and altered disturbance regimes. We establish a conceptual framework and research agenda for identifying the spatial characteristics of species ranges, as well as the life history and functional traits, that are associated with extinction risk for plant species with functional attributes emblematic of fire-prone, winter-precipitation Mediterranean-type ecosystems (MTEs). MTEs worldwide are characterized by their high plant diversity and unique floras, historical and contemporary high rates of land use change, and strong interactions between climate, fire, and land use. We focus on the California Floristic Province (CFP), an MTE that is a global plant diversity hotspot, and show how our framework can be used to understand the relationships between vulnerability to multiple global change drivers, species traits, and biogeography. Vulnerability can be assessed across species using linked distribution and population models that forecast plant responses to global change scenarios. Our overarching hypothesis is that species-specific vulnerability to global change in MTEs is a function of interactions between species and spatial traits: the nature of this interaction will depend on the type of global change process.

The iDiv Ecotron-A flexible research platform for multitrophic biodiversity research.

Across the globe, ecological communities are confronted with multiple global environmental change drivers, and they are responding in complex ways ranging from behavioral, physiological, and morphological changes within populations to changes in community composition and food web structure with consequences for ecosystem functioning. A better understanding of global change‐induced alterations of multitrophic biodiversity and the ecosystem‐level responses in terrestrial ecosystems requires holistic and integrative experimental approaches to manipulate and study complex communities and processes above and below the ground. We argue that mesocosm experiments fill a critical gap in this context, especially when based on ecological theory and coupled with microcosm experiments, field experiments, and observational studies of macroecological patterns. We describe the design and specifications of a novel terrestrial mesocosm facility, the iDiv Ecotron. It was developed to allow the setup and maintenance of complex communities and the manipulation of several abiotic factors in a near‐natural way, while simultaneously measuring multiple ecosystem functions. To demonstrate the capabilities of the facility, we provide a case study. This study shows that changes in aboveground multitrophic interactions caused by decreased predator densities can have cascading effects on the composition of belowground communities. The iDiv Ecotrons technical features, which allow for the assembly of an endless spectrum of ecosystem components, create the opportunity for collaboration among researchers with an equally broad spectrum of expertise. In the last part, we outline some of such components that will be implemented in future ecological experiments to be realized in the iDiv Ecotron.

Risk Assessment for Key Socio-Economic and Ecological Species in a Sub-Arctic Marine Ecosystem Under Combined Ocean Acidification and Warming

The Arctic may be particularly vulnerable to the consequences of both ocean acidification (OA) and global warming, given the faster pace of these processes in comparison with global average speeds. Here, we use the Atlantis ecosystem model to assess how the trophic network of marine fishes and invertebrates in the Icelandic waters is responding to the combined pressures of OA and warming. We develop an approach where we first identify species by their economic (catch value), social (number of participants in fisheries), or ecological (keystone species) importance. We then use literature-determined ranges of sensitivity to OA and warming for different species and functional groups in the Icelandic waters to parametrize model runs for different scenarios of warming and OA. We found divergent species responses to warming and acidification levels; (mainly) planktonic groups and forage fish benefited while (mainly) benthic groups and predatory fish decreased under warming and acidification scenarios. Assuming conservative harvest rates for the largest catch-value species, Atlantic cod, we see that the population is projected to remain stable under even the harshest acidification and warming scenario. Further, for the scenarios where the model projects reductions in biomass of Atlantic cod, other species in the ecosystem increase, likely due to a reduction in competition and predation. These results highlight the interdependencies of multiple global change drivers and their cascading effects on trophic organization, and the continued high abundance of an important species from a socio-economic perspective in the Icelandic fisheries.