Testing the effects of diversity on ecosystem multifunctionality using a multivariate model

Most ecosystems provide multiple services, thus the impact of biodiversity losses on ecosystem functions may be considerably underestimated by studies that only address single functions. We propose a multivariate modelling framework for quantifying the relationship between biodiversity and multiple ecosystem functions (multifunctionality). Our framework consolidates the strengths of previous approaches to analysing ecosystem multifunctionality and contributes several advances. It simultaneously assesses the drivers of multifunctionality, such as species relative abundances, richness, evenness and other manipulated treatments. It also tests the relative importance of these drivers across functions, incorporates correlations among functions and identifies conditions where all functions perform well and where trade‐offs occur among functions. We illustrate our framework using data from three ecosystem functions (sown biomass, weed suppression and nitrogen yield) in a four‐species grassland experiment. We found high variability in performance across the functions in monocultures, but as community diversity increased, performance increased and variability across functions decreased.     

Low multifunctional redundancy of soil fungal diversity at multiple scales

Theory suggests that biodiversity might help sustain multiple ecosystem functions. To evaluate possible biodiversity–multifunctionality relationships in a natural setting, we considered different spatial scales of diversity metrics for soil fungi in the northern forests of Japan. We found that multifunctionality increased with increasing local species richness, suggesting a limited degree of multifunctional redundancy. This diversity–multifunctionality relationship was independent of the compositional uniqueness of each community. However, we still found the importance of community composition, because there was a positive correlation between community dissimilarity and multifunctional dissimilarity across the landscape. This result suggests that functional redundancy can further decrease when spatial variations in identities of both species and functions are simultaneously considered at larger spatial scales. We speculate that different scales of diversity could provide multiple levels of insurance against the loss of functioning if high‐levels of local species diversity and compositional variation across locations are both maintained. Alternatively, making species assemblages depauperate may result in the loss of multifunctionality.     

Undertaking large‐scale forest restoration to generate ecosystem services

The global community is seeking to substantially restore the world's forest cover to improve the supply of ecosystem services. However, it is not clear what type of reforestation must be used and there is a risk that the techniques used in industrial timber plantations will become the default methodology. This is unlikely to be sufficient because of the well‐known relationship between biodiversity and ecological functioning. Restoration may be achieved through natural regeneration but this may not always occur at critical locations. Ecological restoration involving species‐rich plantings might also be used but can be difficult to implement at landscape scales. I review here the consequence of planting more limited numbers of species and the effects of this on the delivery of ecosystem services. Evidence suggests many commonly sought ecosystem services—though not all—may be generated by the modest levels of species richness provided these species have appropriate traits. The literature also shows that the alpha diversity of restored forests is not the only driver of functionality and that the location and extent of any reforestation are significant as well; beta and gamma diversity may also affect functionality but these relationships remain unclear. Encouraging the adoption of even moderately diverse plantings at landscape scales and at key locations will require policies and institutions to balance the type, location, and scale of restoration and make the necessary trade‐offs between national and local aspirations. New approaches and metrics will have to be developed to monitor and assess restoration success at these larger scales.     

Trade‐offs between savanna woody plant diversity and carbon storage in the Brazilian Cerrado

Incentivizing carbon storage can be a win‐win pathway to conserving biodiversity and mitigating climate change. In savannas, however, the situation is more complex. Promoting carbon storage through woody encroachment may reduce plant diversity of savanna endemics, even as the diversity of encroaching forest species increases. This trade‐off has important implications for the management of biodiversity and carbon in savanna habitats, but has rarely been evaluated empirically. We quantified the nature of carbon‐diversity relationships in the Brazilian Cerrado by analyzing how woody plant species richness changed with carbon storage in 206 sites across the 2.2 million km² region at two spatial scales. We show that total woody plant species diversity increases with carbon storage, as expected, but that the richness of endemic savanna woody plant species declines with carbon storage both at the local scale, as woody biomass accumulates within plots, and at the landscape scale, as forest replaces savanna. The sharpest trade‐offs between carbon storage and savanna diversity occurred at the early stages of carbon accumulation at the local scale but the final stages of forest encroachment at the landscape scale. Furthermore, the loss of savanna species quickens in the final stages of forest encroachment, and beyond a point, savanna species losses outpace forest species gains with increasing carbon accumulation. Our results suggest that although woody encroachment in savanna ecosystems may provide substantial carbon benefits, it comes at the rapidly accruing cost of woody plant species adapted to the open savanna environment. Moreover, the dependence of carbon‐diversity trade‐offs on the amount of savanna area remaining requires land managers to carefully consider local conditions. Widespread woody encroachment in both Australian and African savannas and grasslands may present similar threats to biodiversity.     

Quantifying ecosystem service trade‐offs for plantation forest management to benefit provisioning and regulating services

There is increasing interest worldwide regarding managing plantation forests in a manner that maintains or improves timber production, enhances ecosystem services, and promotes long‐term sustainability of forest resources. We selected the Gan River Basin, the largest catchment of Poyang Lake and a region with a typical plantation distribution in South China, as the study region. We evaluated and mapped four important forest ecosystem services, including wood volume, carbon storage, water yield, and soil retention at a 30 × 30 m resolution, then quantified their trade‐offs and synergies at the county and subwatershed scales. We found that the wood volume and carbon storage services, as well as the soil retention and water yield, exhibited synergistic relationships. However, the carbon storage displayed a trade‐off relationship with the water yield. Additionally, we compared the beneficial spatial characteristics among dominant species in the study region. The results showed that the Chinese fir forest and the pine forest exhibited lower overall benefits than natural forests including the broad‐leaved forest and the bamboo forest. To propose a suitable management strategy for the study region, method of spatial cluster analysis was used based on the four eco‐services at the subwatershed scale. The basin was divided into four management groups instead of treating the region as a homogenous management region. Finally, we proposed more specific and diverse management strategies to optimize forest benefits throughout the entire region.     

Toward a methodical framework for comprehensively assessing forest multifunctionality

Biodiversity–ecosystem functioning (BEF) research has extended its scope from communities that are short‐lived or reshape their structure annually to structurally complex forest ecosystems. The establishment of tree diversity experiments poses specific methodological challenges for assessing the multiple functions provided by forest ecosystems. In particular, methodological inconsistencies and nonstandardized protocols impede the analysis of multifunctionality within, and comparability across the increasing number of tree diversity experiments. By providing an overview on key methods currently applied in one of the largest forest biodiversity experiments, we show how methods differing in scale and simplicity can be combined to retrieve consistent data allowing novel insights into forest ecosystem functioning. Furthermore, we discuss and develop recommendations for the integration and transferability of diverse methodical approaches to present and future forest biodiversity experiments. We identified four principles that should guide basic decisions concerning method selection for tree diversity experiments and forest BEF research: (1) method selection should be directed toward maximizing data density to increase the number of measured variables in each plot. (2) Methods should cover all relevant scales of the experiment to consider scale dependencies of biodiversity effects. (3) The same variable should be evaluated with the same method across space and time for adequate larger‐scale and longer‐time data analysis and to reduce errors due to changing measurement protocols. (4) Standardized, practical and rapid methods for assessing biodiversity and ecosystem functions should be promoted to increase comparability among forest BEF experiments. We demonstrate that currently available methods provide us with a sophisticated toolbox to improve a synergistic understanding of forest multifunctionality. However, these methods require further adjustment to the specific requirements of structurally complex and long‐lived forest ecosystems. By applying methods connecting relevant scales, trophic levels, and above‐ and belowground ecosystem compartments, knowledge gain from large tree diversity experiments can be optimized.     

Differential sensitivity of total and active soil microbial communities to drought and forest management

Climate change will affect semiarid ecosystems through severe droughts that increase the competition for resources in plant and microbial communities. In these habitats, adaptations to climate change may consist of thinning—that reduces competition for resources through a decrease in tree density and the promotion of plant survival. We deciphered the functional and phylogenetic responses of the microbial community to 60 years of drought induced by rainfall exclusion and how forest management affects its resistance to drought, in a semiarid forest ecosystem dominated by Pinus halepensis Mill. A multiOMIC approach was applied to reveal novel, community‐based strategies in the face of climate change. The diversity and the composition of the total and active soil microbiome were evaluated by 16S rRNA gene (bacteria) and ITS (fungal) sequencing, and by metaproteomics. The microbial biomass was analyzed by phospholipid fatty acids (PLFAs), and the microbially mediated ecosystem multifunctionality was studied by the integration of soil enzyme activities related to the cycles of C, N, and P. The microbial biomass and ecosystem multifunctionality decreased in drought‐plots, as a consequence of the lower soil moisture and poorer plant development, but this decrease was more notable in unthinned plots. The structure and diversity of the total bacterial community was unaffected by drought at phylum and order level, but did so at genus level, and was influenced by seasonality. However, the total fungal community and the active microbial community were more sensitive to drought and were related to ecosystem multifunctionality. Thinning in plots without drought increased the active diversity while the total diversity was not affected. Thinning promoted the resistance of ecosystem multifunctionality to drought through changes in the active microbial community. The integration of total and active microbiome analyses avoids misinterpretations of the links between the soil microbial community and climate change.     

Variation in above‐ground forest biomass across broad climatic gradients

Aim An understanding of the relationship between forest biomass and climate is needed to predict the impacts of climate change on carbon stores. Biomass patterns have been characterized at geographically or climatically restricted scales, making it unclear if biomass is limited by climate in any general way at continental to global scales. Using a dataset spanning multiple climatic regions we evaluate the generality of published biomass–climate correlations. We also combine metabolic theory and hydraulic limits to plant growth to first derive and then test predictions for how forest biomass should vary with maximum individual tree biomass and the ecosystem water deficit. Location Temperate forests and dry, moist and wet tropical forests across North, Central and South America. Methods A forest biomass model was derived from allometric functions and power‐law size distributions. Biomass and climate were correlated using extensive forest plot (276 0.1‐ha plots), wood density and climate datasets. Climate variables included mean annual temperature, annual precipitation, their ratio, precipitation of the driest quarter, potential and actual evapotranspiration, and the ecosystem water deficit. The water deficit uniquely summarizes water balance by integrating water inputs from precipitation with water losses due to solar energy. Results Climate generally explained little variation in forest biomass, and mixed support was found for published biomass–climate relationships. Our theory indicated that maximum individual biomass governs forest biomass and is constrained by water deficit. Indeed, forest biomass was tightly coupled to maximum individual biomass and the upper bound of maximum individual biomass declined steeply with water deficit. Water deficit similarly constrained the upper bound of forest biomass, with most forests below the constraint. Main conclusions The results suggest that: (1) biomass–climate models developed at restricted geographic/climatic scales may not hold at broader scales; (2) maximum individual biomass is strongly related to forest biomass, suggesting that process‐based models should focus on maximum individual biomass; (3) the ecosystem water deficit constrains biomass, but realized biomass often falls below the constraint; such that (4) biomass is not strongly limited by climate in most forests so that forest biomass may not predictably respond to changes in mean climate.     

Trade‐offs between carbon stocks and biodiversity in European temperate forests

Policies to mitigate climate change and biodiversity loss often assume that protecting carbon‐rich forests provides co‐benefits in terms of biodiversity, due to the spatial congruence of carbon stocks and biodiversity at biogeographic scales. However, it remains unclear whether this holds at the scales relevant for management, and particularly large knowledge gaps exist for temperate forests and for taxa other than trees. We built a comprehensive dataset of Central European temperate forest structure and multi‐taxonomic diversity (beetles, birds, bryophytes, fungi, lichens, and plants) across 352 plots. We used Boosted Regression Trees (BRTs) to assess the relationship between above‐ground live carbon stocks and (a) taxon‐specific richness, (b) a unified multidiversity index. We used Threshold Indicator Taxa ANalysis to explore individual species’ responses to changing above‐ground carbon stocks and to detect change‐points in species composition along the carbon‐stock gradient. Our results reveal an overall weak and highly variable relationship between richness and carbon stock at the stand scale, both for individual taxonomic groups and for multidiversity. Similarly, the proportion of win‐win and trade‐off species (i.e., species favored or disadvantaged by increasing carbon stock, respectively) varied substantially across taxa. Win‐win species gradually replaced trade‐off species with increasing carbon, without clear thresholds along the above‐ground carbon gradient, suggesting that community‐level surrogates (e.g., richness) might fail to detect critical changes in biodiversity. Collectively, our analyses highlight that leveraging co‐benefits between carbon and biodiversity in temperate forest may require stand‐scale management that prioritizes either biodiversity or carbon in order to maximize co‐benefits at broader scales. Importantly, this contrasts with tropical forests, where climate and biodiversity objectives can be integrated at the stand scale, thus highlighting the need for context‐specificity when managing for multiple objectives. Accounting for critical change‐points of target taxa can help to deal with this specificity, by defining a safe operating space to manipulate carbon while avoiding biodiversity losses.     

Multiple successional pathways in human‐modified tropical landscapes: new insights from forest succession,forest fragmentation and landscape ecology research

Old‐growth tropical forests are being extensively deforested and fragmented worldwide. Yet forest recovery through succession has led to an expansion of secondary forests in human‐modified tropical landscapes (HMTLs). Secondary forests thus emerge as a potential repository for tropical biodiversity, and also as a source of essential ecosystem functions and services in HMTLs. Such critical roles are controversial, however, as they depend on successional, landscape and socio‐economic dynamics, which can vary widely within and across landscapes and regions. Understanding the main drivers of successional pathways of disturbed tropical forests is critically needed for improving management, conservation, and restoration strategies. Here, we combine emerging knowledge from tropical forest succession, forest fragmentation and landscape ecology research to identify the main driving forces shaping successional pathways at different spatial scales. We also explore causal connections between land‐use dynamics and the level of predictability of successional pathways, and examine potential implications of such connections to determine the importance of secondary forests for biodiversity conservation in HMTLs. We show that secondary succession (SS) in tropical landscapes is a multifactorial phenomenon affected by a myriad of forces operating at multiple spatio‐temporal scales. SS is relatively fast and more predictable in recently modified landscapes and where well‐preserved biodiversity‐rich native forests are still present in the landscape. Yet the increasing variation in landscape spatial configuration and matrix heterogeneity in landscapes with intermediate levels of disturbance increases the uncertainty of successional pathways. In landscapes that have suffered extensive and intensive human disturbances, however, succession can be slow or arrested, with impoverished assemblages and reduced potential to deliver ecosystem functions and services. We conclude that: (i) succession must be examined using more comprehensive explanatory models, providing information about the forces affecting not only the presence but also the persistence of species and ecological groups, particularly of those taxa expected to be extirpated from HMTLs; (ii) SS research should integrate new aspects from forest fragmentation and landscape ecology research to address accurately the potential of secondary forests to serve as biodiversity repositories; and (iii) secondary forest stands, as a dynamic component of HMTLs, must be incorporated as key elements of conservation planning; i.e. secondary forest stands must be actively managed (e.g. using assisted forest restoration) according to conservation goals at broad spatial scales.     

Evaluating the effectiveness of retention forestry to enhance biodiversity in production forests of Central Europe using an interdisciplinary,multi‐scale approach

Retention forestry, which retains a portion of the original stand at the time of harvesting to maintain continuity of structural and compositional diversity, has been originally developed to mitigate the impacts of clear‐cutting. Retention of habitat trees and deadwood has since become common practice also in continuous‐cover forests of Central Europe. While the use of retention in these forests is plausible, the evidence base for its application is lacking, trade‐offs have not been quantified, it is not clear what support it receives from forest owners and other stakeholders and how it is best integrated into forest management practices. The Research Training Group ConFoBi (Conservation of Forest Biodiversity in Multiple‐use Landscapes of Central Europe) focusses on the effectiveness of retention forestry, combining ecological studies on forest biodiversity with social and economic studies of biodiversity conservation across multiple spatial scales. The aim of ConFoBi is to assess whether and how structural retention measures are appropriate for the conservation of forest biodiversity in uneven‐aged and selectively harvested continuous‐cover forests of temperate Europe. The study design is based on a pool of 135 plots (1 ha) distributed along gradients of forest connectivity and structure. The main objectives are (a) to investigate the effects of structural elements and landscape context on multiple taxa, including different trophic and functional groups, to evaluate the effectiveness of retention practices for biodiversity conservation; (b) to analyze how forest biodiversity conservation is perceived and practiced, and what costs and benefits it creates; and (c) to identify how biodiversity conservation can be effectively integrated in multi‐functional forest management. ConFoBi will quantify retention levels required across the landscape, as well as the socio‐economic prerequisites for their implementation by forest owners and managers. ConFoBi's research results will provide an evidence base for integrating biodiversity conservation into forest management in temperate forests.     

面向生态系统服务的森林生态系统经营:现状、挑战与展望

森林生态系统是地球陆地生态系统的主体,它具有很高的生物生产力和生物量以及丰富的生物多样性,对全球生态系统和人类经济社会发展起着至关重要和无可替代的作用。伴随着人口的不断增长和经济社会的迅猛发展,对森林资源和森林生态系统服务的需求不断高涨,而且人类对森林资源价值的认识也发生了很大程度的改变。推进森林资源可持续经营,增加森林总量、提高森林质量、增强生态功能,已成为中国林业可持续发展乃至推进中国生态文明建设和建设美丽中国的战略任务。本文全面综述了森林生态系统经营发展历程,分析了森林生态系统经营的现状和存在问题,在此基础上,提出整合基于生态系统管理与满足现代人类福祉对森林多重需求的新的森林生态系统经营理念,面向生态系统服务的森林生态系统经营理念是未来的发展趋势。森林经营发展战略表现为:1)从单纯的森林面积数量扩张,转变到提高单位面积的森林生产力和森林质量;2)从单一追求木材生产逐步转变为多目标经营,将森林林产品单一的经营目标转变为广泛的生态、经济和社会等多目标经营;3)森林经营重点从林分水平转变为森林景观的经营,强调森林景观的时空异质性和动态变化,权衡和协同多种生态系统的服务功能,倡导森林景观的多样性和连通性,提高森林与其它土地利用模式镶嵌构成的复合景观的可持续性和稳定性,增强森林生态系统对气候变化影响的适应能力;4)森林生态系统经营将从依赖传统经验的主观决策转变为信息化、数字化和智能化的决策,发展森林生态系统经营决策支持系统和森林景观恢复与空间经营规划系统。     

Ecosystem functions in natural and anthropogenic ecosystems across the East African coastal forest landscape

Habitat identity and landscape configuration significantly shape species communities and affect ecosystem functions. The conservation of natural ecosystems is of particular relevance in regions where landscapes have already been largely transformed into farmland and where habitats suffer under resource exploitation. The spillover of ecosystem functions from natural ecosystems into farmland may positively influence agricultural productivity and human livelihood quality. We measured three proxies of ecosystem functioning: Pollinator diversity (using pan traps), seed dispersal (with a seed removal experiment), and predation (using dummy caterpillars). We assessed these ecosystem functions in three forest types of the East African dry coastal forest (Brachystegia forest, Cynometra forest, and mixed forest), as well as in adjoining farmland and in plantations of exotic trees (Eucalyptus mainly). We measured ecosystem functions at 20 plots for each habitat type, and along gradients ranging from the forest into farmland. We also recorded various environmental parameters for each study plot. We did not find significant differences of ecosystem functions when combining all proxies assessed, neither among the three natural forest types, nor between natural forest and plantations. However, we found trends for single ecosystem functions. We identified highest pollinator diversity along the forest margin and in farmlands. Vegetation cover and blossom density affected the level of predation positively. Based on our findings, we suggest that flowering gardens around housings and woodlots across farmland areas support ecosystem functioning and thus improve human livelihood quality. We conclude that levels of overall ecosystem functions are affected by entire landscapes, and high landscape heterogeneity, as found in our case, might blur potential negative effects and trends arising from habitat destruction and degradation.     

Multifunctionality is affected by interactions between green roof plant species,substrate depth,and substrate type

Green roofs provide ecosystem services through evapotranspiration and nutrient cycling that depend, among others, on plant species, substrate type, and substrate depth. However, no study has assessed thoroughly how interactions between these factors alter ecosystem functions and multifunctionality of green roofs. We simulated some green roof conditions in a pot experiment. We planted 20 plant species from 10 genera and five families (Asteraceae, Caryophyllaceae, Crassulaceae, Fabaceae, and Poaceae) on two substrate types (natural vs. artificial) and two substrate depths (10 cm vs. 30 cm). As indicators of major ecosystem functions, we measured aboveground and belowground biomasses, foliar nitrogen and carbon content, foliar transpiration, substrate water retention, and dissolved organic carbon and nitrates in leachates. Interactions between substrate type and depth strongly affected ecosystem functions. Biomass production was increased in the artificial substrate and deeper substrates, as was water retention in most cases. In contrast, dissolved organic carbon leaching was higher in the artificial substrates. Except for the Fabaceae species, nitrate leaching was reduced in deep, natural soils. The highest transpiration rates were associated with natural soils. All functions were modulated by plant families or species. Plant effects differed according to the observed function and the type and depth of the substrate. Fabaceae species grown on natural soils had the most noticeable patterns, allowing high biomass production and high water retention but also high nitrate leaching from deep pots. No single combination of factors enhanced simultaneously all studied ecosystem functions, highlighting that soil–plant interactions induce trade‐offs between ecosystem functions. Substrate type and depth interactions are major drivers for green roof multifunctionality.     

Multifunctionality of biocrusts is positively predicted by network topologies consistent with interspecies facilitation

The potential of biodiversity loss to impair the delivery of ecosystem services has motived ecologists to better understand the relationship between biodiversity and ecosystem functioning. Although increasing evidence underlines the collective contribution of different biodiversity components on the simultaneous performance of multiple functions (multifunctionality), we know little about the trade‐offs between individual diversity effects and the extent to which they determine multifunctionality differentially. Here, at a subcontinental scale of 62 dryland sites, we show in phototrophic microbiota of biological soil crusts (biocrusts) that, whereas richness alone is unable to guarantee the maxima of multifunctional performance, interspecies facilitation and compositional identity are particularly stronger but often neglected predictors. The inconsistent effects of different biodiversity components imply that soil multifunctionality can be lost despite certain species remaining present. Moreover, we reveal a significant empirical association between species functional importance and its topological feature in co‐occurrence networks, indicating a functional signal of species interaction. Nevertheless, abundant species tend to isolate and merely interact within small topological structures, but rare species were tightly connected in complicated network modules. Our findings suggest that abundant and rare species of soil phototrophs exhibit distinct functional relevance. These results give a comprehensive view of how soil constructive species drive multifunctionality in biocrusts and ultimately promote a deeper understanding of the consequences of biodiversity loss in real‐world ecosystems.     

Enhancing the structural diversity between forest patches—A concept and real-world experiment to study biodiversity,multifunctionality and forest resilience across spatial scales

Intensification of land use by humans has led to a homogenization of landscapes and decreasing resilience of ecosystems globally due to a loss of biodiversity, including the majority of forests. Biodiversity–ecosystem functioning (BEF) research has provided compelling evidence for a positive effect of biodiversity on ecosystem functions and services at the local (α-diversity) scale, but we largely lack empirical evidence on how the loss of between-patch β-diversity affects biodiversity and multifunctionality at the landscape scale (γ-diversity). Here, we present a novel concept and experimental framework for elucidating BEF patterns at α-, β-, and γ-scales in real landscapes at a forest management-relevant scale. We examine this framework using 22 temperate broadleaf production forests, dominated by Fagus sylvatica. In 11 of these forests, we manipulated the structure between forest patches by increasing variation in canopy cover and deadwood. We hypothesized that an increase in landscape heterogeneity would enhance the β-diversity of different trophic levels, as well as the β-functionality of various ecosystem functions. We will develop a new statistical framework for BEF studies extending across scales and incorporating biodiversity measures from taxonomic to functional to phylogenetic diversity using Hill numbers. We will further expand the Hill number concept to multifunctionality allowing the decomposition of γ-multifunctionality into α- and β-components. Combining this analytic framework with our experimental data will allow us to test how an increase in between patch heterogeneity affects biodiversity and multifunctionality across spatial scales and trophic levels to help inform and improve forest resilience under climate change. Such an integrative concept for biodiversity and functionality, including spatial scales and multiple aspects of diversity and multifunctionality as well as physical and environmental structure in forests, will go far beyond the current widely applied approach in forestry to increase resilience of future forests through the manipulation of tree species composition.     

Seagrass ecosystem multifunctionality under the rise of a flagship marine megaherbivore

Large grazers (megaherbivores) have a profound impact on ecosystem functioning. However, how ecosystem multifunctionality is affected by changes in megaherbivore populations remains poorly understood. Understanding the total impact on ecosystem multifunctionality requires an integrative ecosystem approach, which is especially challenging to obtain in marine systems. We assessed the effects of experimentally simulated grazing intensity scenarios on ecosystem functions and multifunctionality in a tropical Caribbean seagrass ecosystem. As a model, we selected a key marine megaherbivore, the green turtle, whose ecological role is rapidly unfolding in numerous foraging areas where populations are recovering through conservation after centuries of decline, with an increase in recorded overgrazing episodes. To quantify the effects, we employed a novel integrated index of seagrass ecosystem multifunctionality based upon multiple, well-recognized measures of seagrass ecosystem functions that reflect ecosystem services. Experiments revealed that intermediate turtle grazing resulted in the highest rates of nutrient cycling and carbon storage, while sediment stabilization, decomposition rates, epifauna richness, and fish biomass are highest in the absence of turtle grazing. In contrast, intense grazing resulted in disproportionally large effects on ecosystem functions and a collapse of multifunctionality. These results imply that (i) the return of a megaherbivore can exert strong effects on coastal ecosystem functions and multifunctionality, (ii) conservation efforts that are skewed toward megaherbivores, but ignore their key drivers like predators or habitat, will likely result in overgrazing-induced loss of multifunctionality, and (iii) the multifunctionality index shows great potential as a quantitative tool to assess ecosystem performance. Considerable and rapid alterations in megaherbivore abundance (both through extinction and conservation) cause an imbalance in ecosystem functioning and substantially alter or even compromise ecosystem services that help to negate global change effects. An integrative ecosystem approach in environmental management is urgently required to protect and enhance ecosystem multifunctionality.     

Linking remotely sensed ecosystem resilience with forest mortality across the continental United States

Episodes of forest mortality have been observed worldwide associated with climate change, impacting species composition and ecosystem services such as water resources and carbon sequestration. Yet our ability to predict forest mortality remains limited, especially across large scales. Time series of satellite imagery has been used to document ecosystem resilience globally, but it is not clear how well remotely sensed resilience can inform the prediction of forest mortality across continental, multi-biome scales. Here, we leverage forest inventories across the continental United States to systematically assess the potential of ecosystem resilience derived using different data sets and methods to predict forest mortality. We found high resilience was associated with low mortality in eastern forests but was associated with high mortality in western regions. The unexpected resilience–mortality relation in western United States may be due to several factors including plant trait acclimation, insect population dynamics, or resource competition. Overall, our results not only supported the opportunity to use remotely sensed ecosystem resilience to predict forest mortality but also highlighted that ecological factors may have crucial influences because they can reverse the sign of the resilience–mortality relationships.     

Growing the urban forest: tree performance in response to biotic and abiotic land management

Forests are vital components of the urban landscape because they provide ecosystem services such as carbon sequestration, storm‐water mitigation, and air‐quality improvement. To enhance these services, cities are investing in programs to create urban forests. A major unknown, however, is whether planted trees will grow into the mature, closed‐canopied forest on which ecosystem service provision depends. We assessed the influence of biotic and abiotic land management on planted tree performance as part of urban forest restoration in New York City, U.S.A. Biotic treatments were designed to improve tree growth, with the expectation that higher tree species composition (six vs. two) and greater stand complexity (with shrubs vs. without) would facilitate tree performance. Similarly, the abiotic treatment (compost amendment vs. without) was expected to increase tree performance by improving soil conditions. Growth and survival was measured for approximately 1,300 native saplings across three growing seasons. The biotic and abiotic treatments significantly improved tree performance, where shrub presence increased tree height for five of the six tree species, and compost increased basal area and stem volume of all species. Species‐specific responses, however, highlighted the difficulty of achieving rapid growth with limited mortality. Pioneer species had the highest growth in stem volume over 3 years (up to 3,500%), but also the highest mortality (up to 40%). Mid‐successional species had lower mortality (<16%), but also the slowest growth in volume (approximately 500% in volume). Our results suggest that there will be trade‐offs between optimizing tree growth versus survival when implementing urban tree planting initiatives.     

The way forward in biochar research: targeting trade‐offs between the potential wins

Biochar application to soil is currently widely advocated for a variety of reasons related to sustainability. Typically, soil amelioration with biochar is presented as a multiple‐‘win’ strategy, although it is also associated with potential risks such as environmental contamination. The most often claimed benefits of biochar (i.e. the ‘wins’) include (i) carbon sequestration; (ii) soil fertility enhancement; (iii) biofuel/bioenergy production; (iv) pollutant immobilization; and (v) waste disposal. However, the vast majority of studies ignore possible trade‐offs between them. For example, there is an obvious trade‐off between maximizing biofuel production and maximizing biochar production. Also, relatively little attention has been paid to mechanisms, as opposed to systems impacts, behind observed biochar effects, often leaving open the question as to whether they reflect truly unique properties of biochar as opposed to being simply the short‐term consequences of a fertilization or liming effect. Here, we provide an outline for the future of soil biochar research. We first identify possible trade‐offs between the potential benefits. Second, to be able to better understand and quantify these trade‐offs, we propose guidelines for robust experimental design and selection of appropriate controls that allow both mechanistic and systems assessment of biochar effects and trade‐offs between the wins. Third, we offer a conceptual framework to guide future experiments and suggest guidelines for the standardized reporting of biochar experiments to allow effective between‐site comparisons to quantify trade‐offs. Such a mechanistic and systems framework is required to allow effective comparisons between experiments, across scales and locations, to guide policy and recommendations concerning biochar application to soil.