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Atmospheric nitrogen (N) pollution is a major and ongoing cause of biodiversity loss across the UK, but in some locations N pollution pressures have been declining. In response to these dynamics, JNCC requested a workshop to help to scope Phase 2 of the Air Pollution Recovery Indicators (APRI) project. The damaging effects of excess N load and of gaseous ammonia on many ecosystems are clear. However, the processes and timescales of ecosystem recovery following a decrease in pollution pressure are less well understood. The APRI project aims to take practical steps to fill this knowledge gap by delivering new scientific research focused on indicators of ecosystem and species recovery from N pollution. In Phase 1, predominantly below-ground responses are being studied at a dry heathland site where experimental additions of N were made between 1998 and 2011, revealing lingering effects on soil chemistry, the soil fungi community and vegetation structure (Kowal et al. 2024). The effect on mycorrhizal fungi, and using these fungi as recovery indicators, is being examined in more detail with recently established assessment methods (Arrigoni et al. 2023). Phase 2 of APRI will consider recovery from N impacts more broadly, e.g. by studying other habitats or species. Further empirical research may be commissioned to better understand recovery pathways from air pollution. A workshop was held on 7–8 November 2023 to help develop an action plan for the remainder of the APRI project. This report summarises the workshop discussion and ensuing work. We note that the focus of the APRI project is on assessing recovery. It is therefore essential to contrast responses of ecosystems subject to decreased pollution pressure with indicators from ecosystems experiencing ongoing pollution. Properties that have been used previously to assess impacts can be used to understand recovery, and novel indicators of ecosystem change are also likely to be useful for assessing recovery. Whatever indica

Purpose of Review International ambitions for massive afforestation and restoration are high. To make these investments sustainable and resilient under future climate change, science is calling for a shift from planting monocultures to mixed forests. But what is the scientific basis for promoting diverse plantations, and what is the feasibility of their establishment and management? As the largest global network of tree diversity experiments, TreeDivNet is uniquely positioned to answer these pressing questions. Building on 428 peer-reviewed TreeDivNet studies, combined with the results of a questionnaire completed by managers of 32 TreeDivNet sites, we aimed to answer the following questions: (i) How and where have TreeDivNet experiments enabled the relationship between tree diversity and tree performance (including productivity, survival, and pathogen damage) to be studied, and what has been learned? (ii) What are the remaining key knowledge gaps in our understanding of the relationship between tree diversity and tree performance? and (iii) What practical insights can be gained from the TreeDivNet experiments for operational, real-world forest plantations? Recent Findings We developed a conceptual framework that identifies the variety of pathways through which target tree performance is related to local neighbourhood diversity and mapped the research efforts for each of those pathways. Experimental research on forest mixtures has focused primarily on direct tree diversity effects on productivity, with generally positive effects of species and functional diversity on productivity. Fewer studies focused on indirect effects mediated via biotic growing conditions (e.g. soil microbes and herbivores) and resource availability and uptake. Most studies examining light uptake found positive effects of species diversity. For pests and diseases, the evidence points mostly towards lower levels of infection for target trees when growing in mixed plantations. Tree diversity effe

Enhancing tree diversity may be important to fostering resilience to drought-related climate extremes. So far, little attention has been given to whether tree diversity can increase the survival of trees and reduce its variability in young forest plantations.We conducted an analysis of seedling and sapling survival from 34 globally distributed tree diversity experiments (363,167 trees, 168 species, 3744 plots, 7 biomes) to answer two questions: (1) Do drought and tree diversity alter the mean and variability in plot-level tree survival, with higher and less variable survival as diversity increases? and (2) Do species that survive poorly in monocultures survive better in mixtures and do specific functional traits explain monoculture survival?Tree species richness reduced variability in plot-level survival, while functional diversity (Rao's Q entropy) increased survival and also reduced its variability. Importantly, the reduction in survival variability became stronger as drought severity increased. We found that species with low survival in monocultures survived comparatively better in mixtures when under drought. Species survival in monoculture was positively associated with drought resistance (indicated by hydraulic traits such as turgor loss point), plant height and conservative resource-acquisition traits (e.g. low leaf nitrogen concentration and small leaf size).Synthesis. The findings highlight: (1) The effectiveness of tree diversity for decreasing the variability in seedling and sapling survival under drought; and (2) the importance of drought resistance and associated traits to explain altered tree species survival in response to tree diversity and drought. From an ecological perspective, we recommend mixing be considered to stabilize tree survival, particularly when functionally diverse forests with drought-resistant species also promote high survival of drought-sensitive species.

The global movement for ecosystem restoration has gained momentum in response to the Bonn Challenge (2010) and the UN Decade on Ecosystem Restoration (UNDER, 2021–2030). While several science-based guidelines exist to aid in achieving successful restoration outcomes, significant variation remains in the outcomes of restoration projects. Some of this disparity can be attributed to unexpected responses of ecosystem components to planned interventions. Given the complex nature of ecosystems, we propose that concepts from Complex Systems Science (CSS) that are linked to non-linearity, such as regime shifts, ecological resilience and ecological feedbacks, should be employed to help explain this variation in restoration outcomes from an ecological perspective. Our framework, Explore Before You Restore, illustrates how these concepts impact restoration outcomes by influencing degradation and recovery trajectories. Additionally, we propose incorporating CSS concepts into the typical restoration project cycle through a CSS assessment phase and suggest that the need for such assessment is explicitly included in the guidelines to improve restoration outcomes. To facilitate this inclusion and make it workable by practitioners, we describe indicators and methods available for restoration teams to answer key questions that should make up such CSS assessment. In doing so, we identify key outstanding science and policy tasks that are needed to further operationalize CSS assessment in restoration. Synthesis and applications. By illustrating how key Complex Systems Science (CSS) concepts linked to non-linear threshold behaviour can impact restoration outcomes through influencing recovery trajectories, our framework Explore Before You Restore demonstrates the need to incorporate Complex Systems thinking in ecosystem restoration. We argue that inclusion of CSS assessment into restoration project cycles, and more broadly, into international restoration guidelines, may significantly impr

Ecological restoration increasingly aims at improving ecosystem multifunctionality and making landscapes resilient to future threats, especially in biodiversity hotspots such as Mediterranean-type ecosystems. Plants and their traits play a major role in the functioning of an ecosystem. Therefore, successful restoration towards long-term multifunctionality requires a fundamental mechanistic understanding of this link under changing climate. An integrated approach of empirical research and simulation modelling with a focus on plant traits can allow this understanding. Based on empirical data from a large-scale restoration project in a Mediterranean-type ecosystem in Western Australia, we developed and validated the spatially explicit simulation model Modelling Ecosystem Functions and Services based on Traits (ModEST), which calculates coupled dynamics of nutrients, water and individual plants characterised by functional traits. We then simulated all possible combinations of eight plant species with different levels of diversity to assess the role of plant diversity and traits on multifunctionality, the provision of six ecosystem functions that can be linked to ecosystem services, as well as trade-offs and synergies among the functions under current and future climatic conditions. Our results show that multifunctionality cannot fully be achieved because of trade-offs among functions that are attributable to sets of traits that affect functions differently. Our measure of multifunctionality was increased by higher levels of planted species richness under current, but not future climatic conditions. In contrast, single functions were differently impacted by increased plant diversity and thus the choice and weighting of these functions affected multifunctionality. In addition, we found that trade-offs and synergies among functions shifted with climate change due to different direct and indirect (mediated via community trait changes) effects of climate change on functions.

As of 2020, the world has an estimated 290 million ha of planted forests and this number is continuously increasing. Of these, 131 million ha are monospecific planted forests under intensive management. Although monospecific planted forests are important in providing timber, they harbor less biodiversity and are potentially more susceptible to disturbances than natural or diverse planted forests. Here, we point out the increasing scientific evidence for increased resilience and ecosystem service provision of functionally and species diverse planted forests (hereafter referred to as diverse planted forests) compared to monospecific ones. Furthermore, we propose five concrete steps to foster the adoption of diverse planted forests: (1) improve awareness of benefits and practical options of diverse planted forests among land-owners, managers, and investors; (2) incentivize tree species diversity in public funding of afforestation and programs to diversify current maladapted planted forests of low diversity; (3) develop new wood-based products that can be derived from many different tree species not yet in use; (4) invest in research to assess landscape benefits of diverse planted forests for functional connectivity and resilience to global-change threats; and (5) improve the evidence base on diverse planted forests, in particular in currently under-represented regions, where new options could be tested.   &nbsp

Klimaatverandering en stikstofdepositie leiden tot veranderingen in gematigde bossen overheen Europa met een mogelijk verlies aan biodiversiteit als gevolg. Gematigde bossen komen voor in milde klimaatcondities en zijn herkenbaar aan het hoge aandeel loofbomen. Deze bossen komen voor in de meest dichtbevolkte regio’s van Europa en zijn bijgevolg onderhevig aan een hoge omgevingsdruk. Beleidsmakers willen weten hoe bossen precies zullen wijzigen en hoe toekomstig bosbeheer ermee kan omgaan. Wij onderzochten of besluitnemers in bosbeheer de kruidlaag mee in rekening nemen bij toekomstige besluitvorming en of ze hier voorspellende modellen voor gebruikten. Dit onderzoek gebeurde in twee luiken door een bevraging van besluitnemers in bosbeheer aan te vullen met een uitgebreide literatuurstudie naar bestaande beslissingsondersteunende modellen. Met de aanbevelingen uit deze studie ontwikkelden we een prototype van een systeem dat trends in de biodiversiteit van de kruidlaag tracht te voorspellen. Dit artikel is een kennismaking met het beslissingsondersteunend model, genaamd UnderSCORE.

Professor Richard Hobbs has had a profound influence on the development of the discipline of restoration ecology. With more than 300 publications spanning a broad scope of applied ecological sciences, he has collaborated with hundreds of researchers. His sometimes‐provocative insights, balanced by extensive empirical research, will have a lasting impact by encouraging people to think more broadly about the science and practice of ecological restoration. Here, on the eve of his retirement, some of his staff and students, past and present, take a retrospective look at his contributions to restoration ecology both as a scientist and as a mentor.

TreeDivNet is the largest network of biodiversity experiments worldwide, but needs to expand. We encourage colleagues to establish new experiments on the relation between tree species diversity and forest ecosystem functioning, and to make use of the platform for collaborative research.

Simultaneous environmental changes challenge biodiversity persistence and human wellbeing. The science and practice of restoration ecology, in collaboration with other disciplines, can contribute to overcoming these challenges. This endeavor requires a solid conceptual foundation based in empirical research which confronts, tests and influences theoretical developments. We review conceptual developments in restoration ecology over the last 30 years. We frame our review in the context of changing restoration goals which reflect increased societal awareness of the scale of environmental degradation and the recognition that inter-disciplinary approaches are needed to tackle environmental problems. Restoration ecology now encompasses facilitative interactions and network dynamics, trophic cascades, and above- and below ground linkages. It operates in a non-equilibrium, alternative states framework, at the landscape scale, and in response to changing environmental, economic and social conditions. Progress has been marked by conceptual advances in the fields of trait-environment relationships, community assembly, and understanding the links between biodiversity and ecosystem functioning. Conceptual and practical advances have been enhanced by applying evolving technologies, including treatments to increase seed germination and overcome recruitment bottlenecks, high throughput DNA sequencing to elucidate soil community structure and function, and advances in satellite technology and GPS tracking to monitor habitat use. The synthesis of these technologies with systematic reviews of context dependencies in restoration success, model based analyses and consideration of complex socio-ecological systems will allow generalizations to inform evidence based interventions. Ongoing challenges include setting realistic, socially acceptable goals for restoration under changing environmental conditions, and prioritizing actions in an increasingly space-competitive world. Ethical questi

Woody plantings are increasing across the globe to satisfy ecosystem service markets for carbon and ecological restoration. Assessments of these complex woody systems typically use coarse-scale parameters, based on the climate and soil type of a region, and/or remotely assessed vegetation cover, to estimate carbon in their above- and belowground biomass. However it remains poorly known what factors influence their biomass at finer scales. Here, we investigated biomass variability after five years across a 250ha environmental planting on a former agricultural property in south-western Australia. We aimed to understand which factors may influence observed biomass variability. The dominant canopy tree, Eucalyptus occidentalis, was planted as seedlings, and other woody species were direct sown in vegetation associations, according to soil type and landscape position, to reflect historic native assemblages. Results from 42 survey plots stratified across these associations showed variable seedling establishment from the seed mix, and that the amount of above- and belowground biomass varied widely (Coefficient of variation=60%). A site mean and standard error were inadequate to capture biomass distribution. Instead, two modes were evident within the distribution at approximately 5Mgha-1 and 15Mgha-1 with variation primarily associated with differential seedling establishment and growth across the vegetation associations. Additionally, multiple regression analysis showed that stem density explained a significant amount of biomass variation whilst greater species richness was associated with increased biomass once stem density had been accounted for - models combining soil-vegetation association, number of individuals, and species richness explained between 60% and 80% of biomass variation depending on the response variable (total or live biomass) and choice of allometric equations to predict biomass. There was some evidence for a role of nitrogen-fixing species in determini

Aims Understanding the relationships among disturbance, invasion and species change is essential for effective management of many systems. We investigated relationships among fire history, invasion by a native tree species, Allocasuarina huegeliana, and diversity change to understand the potential drivers of plant community alteration in a complex and biodiverse system. Methods We used plant species surveys from 1983 and 2011 to quantify species loss/gain and thence compositional changes. Additionally, we surveyed population densities of the invasive species and collated long-term fire history data for each site. General linear models and non-parametric models were used to assess the strength of relationships between the three variables of interest. Important Findings Within the last 30 years, ~11% of the plant species richness was lost from the reserve. At an individual site level, we found only a 4% average decrease in overall plant species richness, but large species losses and gains that imply considerable compositional shifts. Though such shifts might be expected over 30 years, many of the gained species were common, potentially opportunistic species, while those lost were often locally rare woody perennials. In addition, gained species tended to be expanding their recorded range westward suggesting that they may be responding to the regional drying climate. The relationship between invasion density and species loss was strong over all spatial scales. We identified a potential state change to dominance by the native invasive particularly as high densities prevented species gain at the site scale. In these extreme cases of high invasive density and high biodiversity loss, we argue that there may be a need to directly address the expanding native population.

Feedbacks between plants and soil communities may be elusive, yet they have far-reaching consequences for plant physiology, competition and community structure. Plant–soil feedbacks (PSFs) are plant-mediated changes to soil properties that ultimately influence the performance of the same or other plants (Van der Putten et al., 2013). These PSFs may be mediated by root-associated organisms (hereafter, root-mediated feedbacks) or saprotrophic organisms and associated litter characteristics (hereafter, litter-mediated feedbacks). However, we know little about the potential mechanistic linkages and relative strengths between these distinct, but connected, processes as root- and litter-mediated feedbacks have generally been studied independently from each other. This is despite the fact that root-associated organisms and saprotrophs can interact through various mechanisms, either directly or as mediated by the plant (e.g. Wardle, 2006). By using a trait-based approach,Ke et al. (in this issue of New Phytologist, pp. 329–341) make an important contribution by integrating root- and litter-mediated PSFs in a nitrogen (N)-based, stage-structured plant population and microbial community model. Their approach allows us to start peeking into the ‘black box’ thereby promoting a better understanding of how PSFs operate interactively. Ke et al. considered various plant traits (e.g. decomposability), but also incorporated trait variation in the physiology, demography and composition of the soil microbial community, and tested their separate and interactive effects on PSF strength in a comprehensive simulation framework. Finally, they used empirical evidence from the literature to support their model predictions.

The reality confronting ecosystem managers today is one of heterogeneous, rapidly transforming landscapes, particularly in the areas more affected by urban and agricultural development. A landscape management framework that incorporates all systems, across the spectrum of degrees of alteration, provides a fuller set of options for how and when to intervene, uses limited resources more effectively, and increases the chances of achieving management goals. That many ecosystems have departed so substantially from their historical trajectory that they defy conventional restoration is not in dispute. Acknowledging novel ecosystems need not constitute a threat to existing policy and management approaches. Rather, the development of an integrated approach to management interventions can provide options that are in tune with the current reality of rapid ecosystem change.

Novelty pervades the biosphere. In some cases, potentially irreversible abiotic and/or biotic changes have led to the crossing of thresholds and thus the formation of “novel ecosystems.” Their widespread emergence (particularly on land) and the presence of continued environmental change challenge a traditional restoration goal of restoring an historical ecosystem. Instead, we argue that restoration could broaden its frame of reference to consider how novel ecosystems might be used to maintain global biodiversity and provide ecosystem services and, in doing so, save potentially wasted efforts in attempting to fulfil traditional goals. Here we explore this contention in more depth by addressing: Are novel ecosystems innovative planning or lowering the bar? We show that novel ecosystems were not innovative planning in their original conception. On the contrary, they were recognized as ecosystems that were recalcitrant to traditional restoration approaches, coupled with an awareness that they had arisen inadvertently through deliberate human activity, either on- or off-site. Their recalcitrance to traditional restoration suggests that alternative goals may exist for these ecosystems using sometimes innovative intervention. This management may include biodiversity conservation or restoration for ecological function. We elucidate the latter aspect with reference to an experiment in the wheatbelt of Western Australia—The Ridgefield Multiple Ecosystem Services Experiment—the design of which has been informed by ecological theory and the acceptance of novelty as an ecosystem component. Although novel ecosystems do provide opportunities to broaden restoration planning and practice, and ultimately maintain and conserve global biodiversity in this era of environmental change, they necessarily “lower the bar” in restoration if the bar is considered to be the historical ecosystem. However, in these times of flux, such a bar is increasingly untenable. Instead, careful and appropri

Increasingly governments and the private sector are using planted forests to offset carbon emissions. Few studies, however, examine how tree diversity — defined here as species richness and/or stand composition — affects carbon storage in these plantings. Using aboveground tree biomass as a proxy for carbon storage, we used meta-analysis to compare carbon storage in tree mixtures with monoculture plantings. Tree mixes stored at least as much carbon as monocultures consisting of the mixture's most productive species and at times outperformed monoculture plantings. In mixed-species stands, individual species, and in particular nitrogen-fixing trees, increased stand biomass. Further motivations for incorporating tree richness into planted forests include the contribution of diversity to total forest carbon-pool development, carbon-pool stability and the provision of extra ecosystem services. Our findings suggest a two-pronged strategy for designing carbon plantings including: (1) increased tree species richness; and (2) the addition of species that contribute to carbon storage and other target functions.

Shifts in disturbance regime have often been linked to invasion in systems by native and nonnative species. This process can have negative effects on biodiversity and ecosystem function. Degradation may be ameliorated by the reinstatement of the disturbance regimes, such as the reintroduction of fire in pyrogenic systems. Modeling is one method through which potential outcomes of different regimes can be investigated. We created a population model to examine the control of a native invasive that is expanding and increasing in abundance due to suppressed fire. Our model, parameterized with field data from a case study of the tree Allocasuarina huegeliana in Australian sandplain heath, simulated different fire return intervals with and without the additional management effort of mechanical removal of the native invader. Population behavior under the different management options was assessed, and general estimates of potential biodiversity impacts were compared. We found that changes in fire return intervals made no significant difference in the increase and spread of the population. However, decreased fire return intervals did lower densities reached in the simulated heath patch as well as the estimated maximum biodiversity impacts. When simulating both mechanical removal and fire, we found that the effects of removal depended on the return intervals and the strategy used. Increase rates were not significantly affected by any removal strategy. However, we found that removal, particularly over the whole patch rather than focusing on satellite populations, could decrease average and maximum densities reached and thus decrease the predicted biodiversity impacts. Our simulation model shows that disturbance-based management has the potential to control native invasion in cases where shifted disturbance is the likely driver of the invasion. The increased knowledge gained through the modeling methods outlined can inform management decisions in fire regime planning that takes

Restoration is a young and swiftly developing field. It has been almost a decade since the inception of one of the field's foundational documents-the Society for Ecological Restoration International Primer on Ecological Restoration (Primer). Through a series of organized discussions, we assessed the Primer for its currency and relevance in the modern field of ecological restoration. We focused our assessment on the section entitled "The Nine Attributes of a Restored Ecosystem" and grouped each of the attributes into one of four categories: species composition, ecosystem function, ecosystem stability, and landscape context. We found that in the decade since the document's inception, the concepts, methods, goals, and thinking of ecological restoration have shifted significantly. We discuss each of the four categories in this light with the aim of offering comments and suggestions on options for updating the Primer. We also include a fifth category that we believe is increasingly acknowledged in ecological restoration: the human element. The Primer is an important document guiding the practice of restoration. We hope that this critical assessment contributes to its ongoing development and relevance and more generally to the development of restoration ecology, particularly in our current era of rapid environmental change.

This chapter addresses the facets of novelty that pervade the urban environment before reviewing the ecosystem services that different components of the urban environment provide. It describes the known and potential contribution of novel elements to these services, with a particular focus on vegetation. The services reviewed include biodiversity maintenance, carbon storage, flood regulation, recreation, spiritual fulfilment and education. The chapter discusses how ecosystem service provision could be boosted by novel components but adds that experiments are required to test our assertions. Research is also needed to investigate trade‐offs among the delivery of ecosystem services in urban areas and to investigate whether they can be successfully implemented in urban areas across the globe and in different socio‐cultural, economic and ecological contexts.

The ability of restoration approaches to provide valued ecosystem services needs to be assessed. The emerging carbon market provides an incentive to afforest agricultural landscapes and could potentially achieve multiple outcomes. However, planting monocultures for carbon sequestration may preclude effective delivery of other ecosystem services. Here, we describe the rationale behind the Ridgefield Multiple Ecosystem Services Experiment, a long-term investigation into trade-offs that might prevent the simultaneous provision of high levels of multiple services in the agricultural landscape of south-western Australia. We compare a monoculture treatment of a fast growing native species (Eucalyptus loxophleba) with mixtures of 2, 4 or 8 native plant species. We selected species based on different traits that we predict will relate to the provision of different levels of multiple ecosystem services. We ask: Can restoration of multiple ecosystem services be achieved along with carbon sequestration? Nested treatments of nitrogen deposition and weed removal test whether ecosystem service outcomes respond to environmental changes. We show that historical land-use at the site has the potential to affect service delivery via different soil characteristics and survival of planted species. Ridgefield tests the possibility of restoring and managing agricultural landscapes for multiple ecosystem services, providing a much needed experimental investigation of trade-offs among ecosystem functions.