Towards a multidimensional view of biodiversity and ecosystem functioning in a changing world

Ecosystem coupling: A unifying framework to understand the functioning and recovery of ecosystems

Concern about human modification of Earth's ecosystems has recently motivated ecologists to address how global change drivers will impact the simultaneous provisioning of multiple functions, termed ecosystem multifunctionality (EMF). However, metrics of EMF have often been applied in global change studies with little consideration of the information they provide beyond single functions, or how and why EMF may respond to global change drivers. Here, we critically review the current state of this rapidly expanding field and provide a conceptual framework to guide the effective incorporation of EMF in global change research. In particular, we emphasize the need for a priori identification and explicit testing of the biotic and abiotic mechanisms through which global change drivers impact EMF, as well as assessing correlations among multiple single functions because these patterns underlie shifts in EMF. While the role of biodiversity in mediating global change effects on EMF has justifiably received much attention, empirical support for effects via other biotic and physicochemical mechanisms are also needed. Studies also frequently stated the importance of measuring EMF responses to global change drivers to understand the potential consequences for multiple ecosystem services, but explicit links between measured functions and ecosystem services were missing from many such studies. While there is clear potential for EMF to provide novel insights to global change research, predictive understanding will be greatly improved by insuring future research is strongly hypothesis-driven, is designed to explicitly test multiple abiotic and biotic mechanisms, and assesses how single functions and their covariation drive emergent EMF responses to global change drivers.

Straw and wood chips have been widely used as mulch materials to control post-fire erosion in burned forests. However, their effects on ecosystem multifunctionality (EMF) have been little explored. This information is essential to give forest managers insight about the effectiveness of these strategies for restoration of severely-burned forests. To fill this gap, this study has evaluated the short-term (one year after wildfire) changes in ecosystem properties (associated to soil characteristics), structure (linked to plant diversity), individual ecosystem functions, and EMF in a Mediterranean forest. This delicate ecosystem was burned by a wildfire and then mulched with straw or wood chips, and EMF in these conditions was compared to burned and untreated, and unburned sites. The results have shown that: (i) neither wildfire nor mulching significantly changed soil properties with the exception of pH; (ii) in contrast, ecosystem structure significantly declined in mulched plots due to wildfire, and mulching did not limit the alteration in species richness; (iii) among the analysed ecosystem functions, waste decomposition and nutrient cycling, which were significantly higher in unburned soils compared to burned sites, showed intermediate and similar values in mulched plots, while water cycle and wood production (the latter with the exception of unburned plots) were similar among all soil conditions, and climate regulation was significantly higher only in soils mulched with wood chips compared to burned sites; (iv) EMF increased from burned and untreated soils to unburned sites; (v) mulching was effective at limiting the reduction in EMF due to wildfire, but only partially dampened the impact of the fire. Moreover, the combined analysis of ecosystem properties, structure and functions, and EMF revealed that: (i) all functions, except water cycle, were associated to one or more soil or vegetation parameters; (ii) species community composition noticeably influenced several ecosystem functions, and, therefore, EMF; (iii) species richness is a key driver of wood production; (iv) pH, which was found as the most influential soil property on ecosystem functions and EMF, may be considered as an important ecological predictor of forest functions in basic soils of Mediterranean forests. This study may be of practical importance for policymakers and land managers about the most effective actions to preserve the ecosystem EMF in fragile ecosystems, such as the Mediterranean wildfire-affected forest.

Global change is transforming Earth’s ecological communities with severe consequences for the functions and services they provide. In temperate grasslands, home to a mesmerising diversity of invertebrates controlling multiple ecosystem processes and services, land-use intensification and climate change are two of the most important global-change drivers. While we know a lot about their independent effects on grassland biodiversity and ecosystem functioning, little is known about how these stressors interact. Moreover, most research on biodiversity change focuses on decreasing biomass or species richness, while a major aspect is commonly ignored – altered ecological interactions. This is problematic because these interactions represent and control many important ecosystem processes, such as predation, herbivory or decomposition. Networks of trophic interactions, so-called food webs, link the structure and functioning of ecological communities and unravel mechanistic relationships between environmental change, ecological communities and ecosystem multifunctionality – the ability of a system to simultaneously support multiple processes. Consequently, we need to study how ecological interactions and the food webs they comprise respond to environmental change and to multiple interacting global-change drivers. Fortunately, novel tools offer unprecedented opportunities in studying trophic interactions and their impact on ecosystem processes. In addition, we know far more about how global change impacts the aboveground world than its belowground counterpart. However, belowground communities are just as important for the overall functioning of terrestrial ecosystems. Thus, to comprehensively understand global-change impacts on temperate grasslands, we need to study above- and belowground multitrophic interactions and ecosystem processes together, also accounting for their interdependencies. Here, we propose to use the Global Change Experimental Facility (GCEF, Bad Lauchstädt, Germany) to study joint impacts of land-use intensity and climate change on above-belowground multitrophic interactions and ecosystem multifunctionality in a temperate grassland global-change experiment. We will combine novel approaches to assessing trophic interactions and basal-resource dependency with an innovative method to quantify energy flux through ecological interaction networks. We will disentangle separate and interactive effects of land use and climate change and unravel how global-change driven modifications in multitrophic interactions mechanistically translate into altered ecosystem processes and multifunctionality – above and below the ground. Combining a field-experimental approach with novel molecular and quantitative techniques will allow for a leap forward in our understanding of global-change impacts on temperate grasslands, which will be crucial to manage and conserve these important ecosystems.

<p>Drivers of global change have direct impacts on the structure of communities and functioning of ecosystems, and interactions between drivers may buffer or exacerbate these direct effects. Interactions among drivers can lead to complex non-linear outcomes for ecosystems, communities and species, but are infrequently quantified. Through a combination of experimental, observational and modelling approaches, I address critical gaps in our understanding of the interactive effects of climate change and plant invasion, using Tongariro National Park (TNP; New Zealand) as a model. TNP is an alpine ecosystem of cultural significance which hosts a unique flora with high rates of endemism. TNP is invaded by the perennial shrub Calluna vulgaris (L.) Hull. My objectives were to: 1) determine whether species-specific phenological shifts have the potential to alter the reproductive capacity of native plants in landscapes affected by invasion; 2) determine whether the effect of invasion intensity on the Species Area Relationship (SAR) of native alpine plant species is influenced by environmental stress; 3) develop a novel modelling framework that would account for density-dependent competitive interactions between native species and C. vulgaris and implement it to determine the combined risk of climate change and plant invasion on the distribution of native plant species; and 4) explore the possible mechanisms leading to a discrepancy in C. vulgaris invasion success on the North and South Islands of New Zealand. I show that species-specific phenological responses to climate warming increase the flowering overlap between a native and an invasive plant. I then show that competition for pollination with the invader decreases the sexual reproduction of the native in some landscapes. I therefore illustrate a previously undescribed interaction between climate warming and plant invasion where the effects of competition for pollination with an invader on the sexual reproduction of the native may be exacerbated by climate warming. Furthermore, I describe a previously unknown pattern of changing invasive plant impact on SAR along an environmental stress gradient. Namely, I demonstrate that interactions between an invasive plant and local native plant species richness become increasingly facilitative along elevational gradients and that the strength of plant interactions is dependent on invader biomass. I then show that the consequences of changing plant interactions at a local scale for the slope of SAR is dependent on the pervasion of the invader. Next, I demonstrate that the inclusion of invasive species density data in distribution models for a native plant leads to greater reductions in predicted native plant distribution and density under future climate change scenarios relative to models based on climate suitability alone. Finally, I find no evidence for large-scale climatic, edaphic, and vegetative limitations to invasion by C. vulgaris on either the North and South Islands of New Zealand. Instead, my results suggest that discrepancies in invasive spread between islands may be driven by human activity: C. vulgaris is associated with the same levels of human disturbance on both islands despite differences in the presence of these conditions between then islands. Altogether, these results show that interactive effects between drivers on biodiversity and ecosystem dynamics are frequently not additive or linear. Therefore, accurate predictions of global change impacts on community structure and ecosystems function require experiments and models which include of interactions among drivers such as climate change and species invasion. These results are pertinent to effective conservation management as most landscapes are concurrently affected by multiple drivers of global environmental change.</p>

<p>Drivers of global change have direct impacts on the structure of communities and functioning of ecosystems, and interactions between drivers may buffer or exacerbate these direct effects. Interactions among drivers can lead to complex non-linear outcomes for ecosystems, communities and species, but are infrequently quantified. Through a combination of experimental, observational and modelling approaches, I address critical gaps in our understanding of the interactive effects of climate change and plant invasion, using Tongariro National Park (TNP; New Zealand) as a model. TNP is an alpine ecosystem of cultural significance which hosts a unique flora with high rates of endemism. TNP is invaded by the perennial shrub Calluna vulgaris (L.) Hull. My objectives were to: 1) determine whether species-specific phenological shifts have the potential to alter the reproductive capacity of native plants in landscapes affected by invasion; 2) determine whether the effect of invasion intensity on the Species Area Relationship (SAR) of native alpine plant species is influenced by environmental stress; 3) develop a novel modelling framework that would account for density-dependent competitive interactions between native species and C. vulgaris and implement it to determine the combined risk of climate change and plant invasion on the distribution of native plant species; and 4) explore the possible mechanisms leading to a discrepancy in C. vulgaris invasion success on the North and South Islands of New Zealand. I show that species-specific phenological responses to climate warming increase the flowering overlap between a native and an invasive plant. I then show that competition for pollination with the invader decreases the sexual reproduction of the native in some landscapes. I therefore illustrate a previously undescribed interaction between climate warming and plant invasion where the effects of competition for pollination with an invader on the sexual reproduction of the native may be exacerbated by climate warming. Furthermore, I describe a previously unknown pattern of changing invasive plant impact on SAR along an environmental stress gradient. Namely, I demonstrate that interactions between an invasive plant and local native plant species richness become increasingly facilitative along elevational gradients and that the strength of plant interactions is dependent on invader biomass. I then show that the consequences of changing plant interactions at a local scale for the slope of SAR is dependent on the pervasion of the invader. Next, I demonstrate that the inclusion of invasive species density data in distribution models for a native plant leads to greater reductions in predicted native plant distribution and density under future climate change scenarios relative to models based on climate suitability alone. Finally, I find no evidence for large-scale climatic, edaphic, and vegetative limitations to invasion by C. vulgaris on either the North and South Islands of New Zealand. Instead, my results suggest that discrepancies in invasive spread between islands may be driven by human activity: C. vulgaris is associated with the same levels of human disturbance on both islands despite differences in the presence of these conditions between then islands. Altogether, these results show that interactive effects between drivers on biodiversity and ecosystem dynamics are frequently not additive or linear. Therefore, accurate predictions of global change impacts on community structure and ecosystems function require experiments and models which include of interactions among drivers such as climate change and species invasion. These results are pertinent to effective conservation management as most landscapes are concurrently affected by multiple drivers of global environmental change.</p>

Three decades of research have demonstrated that biodiversity can promote the functioning of ecosystems. Yet, it is unclear whether the positive effects of biodiversity on ecosystem functioning will persist under various types of global environmental change drivers. We conducted a meta‐analysis of 46 factorial experiments manipulating both species richness and the environment to test how global change drivers (i.e. warming, drought, nutrient addition or CO2 enrichment) modulated the effect of biodiversity on multiple ecosystem functions across three taxonomic groups (microbes, phytoplankton and plants). We found that biodiversity increased ecosystem functioning in both ambient and manipulated environments, but often not to the same degree. In particular, biodiversity effects on ecosystem functioning were larger in stressful environments induced by global change drivers, indicating that high‐diversity communities were more resistant to environmental change. Using a subset of studies, we also found that the positive effects of biodiversity were mainly driven by interspecific complementarity and that these effects increased over time in both ambient and manipulated environments. Our findings support biodiversity conservation as a key strategy for sustainable ecosystem management in the face of global environmental change.

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.

Soil microbial diversity and network complexity sustain ecosystem multifunctionality following afforestation in a dry-hot valley savanna

Chinese fir (Cunninghamia lanceolata) is the main plantation species in the subtropical region of China. However, the shift in ecosystem multifunctionality with stand development remains largely unexplored for these plantations. This study used a chronosequence to investigate the variations of ecosystem multifunctionality by employing individual functions and identified its driving factors in Chinese fir plantations. The findings provide strong evidence that the individual functions of carbon stocks, water regulation and wood production increased with stand ages, but the tradeoff of individual functions did not significantly increase ecosystem multifunctionality. Soil microbial parameters (the abundances of bacteria, fungi and actinomycete), soil properties (soil moisture, total carbon and total nitrogen), and plant parameters (the shrub layer cover and total understory cover) exhibited positive correlations with ecosystem multifunctionality. The structural equation model revealed that plants, soil properties and microbes pathways explained 83% of the total variance in ecosystem multifunctionality. Results showed that plants, soil microbes and properties directly and significantly affected ecosystem multifunctionality with path coefficients of 0.404, 0.487 and 0.334, respectively. Soil microbes were identified as the top direct predictor for ecosystem multifunctionality, while plant and soil properties had strong direct and positive effects on ecosystem multifunctionality. These results verified that soil microbes, plants and soil properties directly and positively regulated ecosystem multifunctionality. Our findings demonstrate that ecosystem multifunctionality should be considered as a comprehensive ecological indicator for ecosystem services and functions, and sustainable plantation management. This study highlights the importance of conserving soil microbes for maintaining multifunctionality in Chinese fir plantations.

As the newest addition to the Senior Editors of Insect Conservation and Diversity (ICD), it is a great pleasure for R.K.D. to be able to lead off this first issue of the journal for 2010. Throughout the second year of operation, our new journal has been growing and developing beyond all expectations, with continued high quality submissions by authors, and effective and timely handling of manuscripts by an exceptional team of Associate Editors. This success has been attributable, in no small measure, to the hard work and commitment of Brad Hawkins as aS enior Editor over the last 2 years, and it is with great reluctance that we bid farewell to Brad from the journal and wish him every success in his future role as Editor-in-Chief of the Journal of Biogeography. With Brad’s support, we saw a substantial increase in the number of submissions of high quality manuscripts to the journal in 2009, and a dramatic increase in the dissemination and uptake of ICD articles by the wider scientific community. Online access to articles increased 70% over 2008 values, with an impressive annual average of over 200 abstract views and almost 150 downloads per article in 2009 (as estimated from data for January–September 2009, at the time of writing this editorial). Citation rates of article so n Thompson Reuters ISI Web of Science also increased dramatically in 2009, and although it is perhaps too early to judge how these will equate to future citation metrics for the journal, it is highly encouraging that current rates are approximately 65% higher than those achieved for articles in comparable journals, such as the Journal of Insect Conservation, at the same point in their citation history. This strongly suggests to us that the wider fields of insect conservation and diversity are burgeoning areas of scientific research, and that ICD is meeting the need for a high quality platform for authors to highlight their findings, and express their views. Although the journal is only in its infancy, it should be possible (at least to some extent) to determine the main research areas driving this dramatic increase in 2009 metrics based on the most downloaded and most cited articles of 2008. In this regard, we have been interested to note the emerging strengths that readers are drawing from ICD. The top four papers contributing directly to the ‘foetal’ h-index (Hirsch, 2005) of our emerging journal, and collectively amounting to 50% of the total journal citations

Plant diseases are strongly influenced by host biodiversity, spatial structure, and abiotic conditions. All of these are undergoing rapid change, as the climate is warming, habitats are being lost, and nitrogen deposition is changing nutrient dynamics of ecosystems with ensuing consequences for biodiversity. Here, I review examples of plant-pathogen associations to demonstrate how our ability to understand, model and predict disease dynamics is becoming increasingly difficult, as both plant and pathogen populations and communities are undergoing extensive change. The extent of this change is influenced via both direct and combined effects of global change drivers, and especially the latter are still poorly understood. Change at one trophic level is expected to drive change also at the other, and hence feedback loops between plants and their pathogens are expected to drive changes in disease risk both through ecological as well as evolutionary mechanisms. Many of the examples discussed here demonstrate an increase in disease risk as a result of ongoing change, suggesting that unless we successfully mitigate global environmental change, plant disease is going to become an increasingly heavy burden on our societies with far-reaching consequences for food security and functioning of ecosystems.

Mountain ecosystems play an important role globally as centers of biodiversity and in providing ecosystem services to lowland populations, but are influenced by multiple global change drivers such as climate change, nitrogen deposition, or altered disturbance regimes. As global change is accelerating and the consequences for humans and nature are intensifying, there is an increasing demand for understanding and predicting the impacts and implications of global change on mountain ecosystems. Manipulation experiments are one of the major tools for testing the causal impacts of global change and establishing a mechanistic understanding of how these changes may transform the global biota from single organisms to entire ecosystems. Over the past three decades, hundreds of such experiments have been conducted in mountainous regions worldwide. To strengthen the experimental evidence for the possible ecological consequences of global change, we systematically reviewed the literature on global change experiments in mountains. We first investigated the spread of manipulation experiments to test the effects of different global change drivers on key biological and ecological processes from the organism to the ecosystem level. We then examined and discussed the balance of evidence regarding the impact of these global change drivers on biological and ecological processes, and outlined the possible consequences for mountain ecosystems. Finally, we identified research gaps and proposed future directions for global change research in mountain environments. Among the major drivers, temperature was manipulated most frequently, generally showing consistent strong impacts between biological and ecosystem processes, functional groups, and habitat types. There is also strong evidence suggesting that changes in water and nutrient availability have a direct impact on the life history and functioning of mountain organisms. Despite these important findings, there are several gaps that require urgent attention. These include experiments testing adult trees in tropical and boreal regions, assessing animal responses and biotic interactions, and investigating aquatic environments and soil systems more extensively. A broader approach that integrates experimental data with field observations and relies on international collaboration through coordinated experiments could help address these gaps and provide a more consistent and robust picture of the impacts of global change on mountain ecosystems.

Direct quantification of terrestrial biosphere responses to global change is crucial for projections of future climate change in Earth system models. Here, we synthesized ecosystem carbon-cycling data from 1,119 experiments performed over the past four decades concerning changes in temperature, precipitation, CO2 and nitrogen across major terrestrial vegetation types of the world. Most experiments manipulated single rather than multiple global change drivers in temperate ecosystems of the USA, Europe and China. The magnitudes of warming and elevated CO2 treatments were consistent with the ranges of future projections, whereas those of precipitation changes and nitrogen inputs often exceeded the projected ranges. Increases in global change drivers consistently accelerated, but decreased precipitation slowed down carbon-cycle processes. Nonlinear (including synergistic and antagonistic) effects among global change drivers were rare. Belowground carbon allocation responded negatively to increased precipitation and nitrogen addition and positively to decreased precipitation and elevated CO2. The sensitivities of carbon variables to multiple global change drivers depended on the background climate and ecosystem condition, suggesting that Earth system models should be evaluated using site-specific conditions for best uses of this large dataset. Together, this synthesis underscores an urgent need to explore the interactions among multiple global change drivers in underrepresented regions such as semi-arid ecosystems, forests in the tropics and subtropics, and Arctic tundra when forecasting future terrestrial carbon-climate feedback.

Global environmental change is altering temperature, precipitation patterns, resource availability, and disturbance regimes. Theory predicts that ecological presses will interact with pulse events to alter ecosystem structure and function. In 2006, we established a long-term, multifactor global change experiment to determine the interactive effects of nighttime warming, increased atmospheric nitrogen (N) deposition, and increased winter precipitation on plant community structure and aboveground net primary production (ANPP) in a northern Chihuahuan Desert grassland. In 2009, a lightning-caused wildfire burned through the experiment. Here, we report on the interactive effects of these global change drivers on pre- and postfire grassland community structure and ANPP. Our nighttime warming treatment increased winter nighttime air temperatures by an average of 1.1°C and summer nighttime air temperature by 1.5°C. Soil N availability was 2.5 times higher in fertilized compared with control plots. Average soil volumetric water content (VWC) in winter was slightly but significantly higher (13.0% vs. 11.0%) in plots receiving added winter rain relative to controls, and VWC was slightly higher in warmed (14.5%) compared with control (13.5%) plots during the growing season even though surface soil temperatures were significantly higher in warmed plots. Despite these significant treatment effects, ANPP and plant community structure were highly resistant to these global change drivers prior to the fire. Burning reduced the cover of the dominant grasses by more than 75%. Following the fire, forb species richness and biomass increased significantly, particularly in warmed, fertilized plots that received additional winter precipitation. Thus, although unburned grassland showed little initial response to multiple ecological presses, our results demonstrate how a single pulse disturbance can interact with chronic alterations in resource availability to increase ecosystem sensitivity to multiple drivers of global environmental change.