生态记忆及其在生态学中的潜在应用

生态记忆指群落过去的状态或经验影响其目前或未来生态响应的能力.作为研究生态系统结构和功能的一个新视角,生态记忆在群落演替、生态恢复、生物入侵和自然资源管理等多个领域中受到重视.本文在综述生态记忆的概念、组成、类别的基础上,进一步探讨了生态记忆的可能机制和影响因素,并指出了其潜在应用,以期为理解演替机理和指导生态恢复提供参考.     

Integrating Soil Ecological Knowledge into Restoration Management

The variability in the type of ecosystem degradation and the specificity of restoration goals can challenge restorationists’ ability to generalize about approaches that lead to restoration success. The discipline of soil ecology, which emphasizes both soil organisms and ecosystem processes, has generated a body of knowledge that can be generally useful in improving the outcomes of restoration despite this variability. Here, we propose that the usefulness of this soil ecological knowledge (SEK) for restoration is best considered in the context of the severity of the original perturbation, the goals of the project, and the resilience of the ecosystem to disturbance. A straightforward manipulation of single physical, chemical, or biological components of the soil system can be useful in the restoration of a site, especially when the restoration goal is loosely defined in terms of the species and processes that management seeks to achieve. These single‐factor manipulations may in fact produce cascading effects on several ecosystem attributes and can result in unintended recovery trajectories. When complex outcomes are desired, intentional and holistic integration of all aspects of the soil knowledge is necessary. We provide a short roster of examples to illustrate that SEK benefits management and restoration of ecosystems and suggest areas for future research.     

Increase in nonnative understorey vegetation cover after nonnative conifer removal and passive restoration

Nonnative conifers are widespread in the southern hemisphere, where their use as plantation species has led to adverse ecosystem impacts sometimes intensified by invasion. Mechanical removal is a common strategy used to reduce or eliminate the negative impacts of nonnative conifers, and encourage native regeneration. However, a variety of factors may preclude active ecological restoration following removal. As a result, passive restoration – unassisted natural vegetation regeneration – is common following conifer removal. We asked, ‘what is the response of understorey cover to removal of nonnative conifer stands followed by passive restoration?' We sampled understorey cover in three site types: two‐ to ten‐year‐old clearcuts, native forest and current plantations. We then grouped understorey species by origin (native/nonnative) and growth form, and compared proportion and per cent cover of these groups as well as of bare ground and litter between the three site types. For clearcuts, we also analysed the effect of time since clearcut on the studied variables. We found that clearcuts had a significantly higher average proportion of nonnative understorey vegetation cover than native forest sites, where nonnative vegetation was nearly absent. The understorey of clearcut sites also averaged more overall vegetation cover and more nonnative vegetation cover (in particular nonnative shrubs and herbaceous species) than either plantation or native forest sites. Notably, 99% of nonnative shrub cover in clearcuts was the invasive nonnative species Scotch broom (Cytisus scoparius). After ten years of passive recovery since clearcutting, the proportion of understorey vegetation cover that is native has not increased and remains far below the proportion observed in native forest sites. Reduced natural regeneration capacity of the native ecosystem, presence of invasive species in the surrounding landscape and land‐use legacies from plantation forestry may inhibit native vegetation recovery and benefit opportunistic invasives, limiting the effectiveness of passive restoration in this context. Abstract in Spanish is available with online material.     

Invasive plant feedbacks promote alternative states in California vernal pools

Invasive species have the potential to create positive feedbacks and push an ecosystem into an alternative state through a variety of mechanisms. Unless the drivers behind these feedbacks are understood, restoring a system to a more desirable state may not be possible. We used a long‐term vernal pool restoration project based out of Travis Airforce Base, Fairfield, CA, U.S.A. to examine natural pools dominated by either invasive or native plant communities, and restored pools predominately composed of invasive plants. We determined that plant community structure is drastically altered towards invasive grasses with the addition of a single centimeter of litter. In the absence of this litter layer, community structure was driven by a non‐native forb rather than native species. We also found that native plant‐dominated vernal pools have a longer inundation duration and are deeper compared to invasive‐dominated pools, regardless of construction status. These results suggest that once invasive grasses establish through lower inundation depths, their litter deposition can initiate a positive feedback to maintain an invasive alternative state. However, even after litter removal, non‐native forbs can replace the grasses causing a second alternative state still separate from the most desirable native dominated state. This study directly demonstrates that invasive species, and their positive feedbacks, may limit the success of ecological restoration. To effectively restore a system all constraints must be identified and removed before successful restoration can occur.     

People as Ecological Participants in Ecological Restoration

In 1987, Bradshaw proposed that ecological restoration is the ultimate “acid test” of our understanding the functioning of ecosystems ( Bradshaw 1987 ). Although this concept is widely supported academically, how it can be applied by restoration practitioners is still unclear. This is an issue not limited to Bradshaw’s acid test, but moreover, reflects a general difficulty associated with the polarization between conceptual restoration (restoration ecology) and practical restoration (ecological restoration), where each has functioned to certain degree in isolation of the other. Outside of the more obvious pragmatic reasons for the relative independence between ecological restoration and restoration ecology, we propose that a more contentious explanation is that the approach taken toward understanding ecosystem development in restoration ecology is tangential to what actually takes place in ecological restoration. Current paradigms assume that the process of ecosystem development in restoration should follow the developmental trajectories suggested by classical ecological succession models. However, unlike these models, ecosystem development in restoration is, at least initially, largely manipulated by people, rather than by abiotic and biotic forces alone. There has been little research undertaken to explore how restoration activities impact upon or add to the extant ecological processes operating within a restoration site. Consequently, ecological restoration may not be so much an acid test of our understanding the functioning of ecosystems, but rather, an acid test of our understanding mutually beneficial interactions between humans and ecosystems.     

植物克隆整合生态效应及潜在应用

克隆植物因特殊的克隆整合和空间拓展特性,在异质生境下展示出较高的生态适应性及适合度,这是其广泛存在于各类生态系统的一个重要原因。目前对克隆整合在个体或种群水平的生态学效应已有较深认识,而对群落及生态系统的影响及作用机制则明显关注不足。前期研究表明,克隆整合对土壤理化性质、根际微生物及个体竞争力均有显著影响,从而有利于克隆植物的成功入侵、生境修复及植被重建等。对群落及生态系统水平的克隆整合生态学效应的研究进行归纳和总结,分析了克隆整合对植物群落结构和生产力、根际微生物和土壤动物、生态系统碳固持、养分循环等的影响;阐释了克隆整合及空间拓展特性对退化生态系统的修复及作用机制,并指出今后克隆整合的研究应同时考虑微观(根际过程)和宏观(群落及生态系统)层次的效应以及短期与长期的效应。可将克隆整合与植物-土壤反馈等其他生态过程相联系,综合探究克隆整合的生态学意义。     

Ecological impacts of human‐induced animal behaviour change

A growing body of literature has documented myriad effects of human activities on animal behaviour, yet the ultimate ecological consequences of these behavioural shifts remain largely uninvestigated. While it is understood that, in the absence of humans, variation in animal behaviour can have cascading effects on species interactions, community structure and ecosystem function, we know little about whether the type or magnitude of human‐induced behavioural shifts translate into detectable ecological change. Here we synthesise empirical literature and theory to create a novel framework for examining the range of behaviourally mediated pathways through which human activities may affect different ecosystem functions. We highlight the few empirical studies that show the potential realisation of some of these pathways, but also identify numerous factors that can dampen or prevent ultimate ecosystem consequences. Without a deeper understanding of these pathways, we risk wasting valuable resources on mitigating behavioural effects with little ecological relevance, or conversely mismanaging situations in which behavioural effects do drive ecosystem change. The framework presented here can be used to anticipate the nature and likelihood of ecological outcomes and prioritise management among widespread human‐induced behavioural shifts, while also suggesting key priorities for future research linking humans, animal behaviour and ecology.     

Resident plant diversity and introduced earthworms have contrasting effects on the success of invasive plants

Theoretical predictions and empirical studies suggest that resident species diversity is an important driver of community invasibility. Through trait-based processes, plants in communities with high resident species diversity occupy a wider range of ecological niches and are more productive than low diversity communities, potentially reducing the opportunities for invasion through niche preemption. In terrestrial plant communities, biotic ecosystem engineers such as earthworms can also affect invasibility by reducing leaf litter stocks and influencing soil conditions. In a greenhouse experiment, we simultaneously manipulated resident species diversity and earthworm presence to investigate independent and interactive effects of these two variables on the success of several invasive plants. Higher diversity of resident species was associated with lower biomass of invasives, with the effect mediated through resident species biomass. The presence of earthworms had a strong positive effect on the biomass of invasive species across all levels of resident species diversity and a weaker indirect negative effect via decreased soil moisture. Earthworms also weakened the positive correlation between resident species diversity and productivity. We did not observe any interactive effects of resident species biomass and earthworms on invasive species success. Partitioning the net biodiversity effect indicated that selection effects increased with resident species diversity whereas complementarity effects did not. Results suggest that managing for diverse forest communities may decrease the susceptibility of these communities to invasions. However, the presence of introduced earthworms in previously earthworm-free sites may undermine these efforts. Furthermore, future studies of plant community invasibility should account for the effects of introduced earthworms.     

Evaluating Ecological Restoration Success: A Review of the Literature

Assessing the success of ecological restoration projects is critical to justify the use of restoration in natural resource management and to improve best practice. Although there are extensive discussions surrounding the characteristics that define and measure successful restoration, monitoring or evaluation of projects in practice is widely thought to have lagged behind. We conducted a literature review to determine trends in evaluations of restoration projects and identify key knowledge gaps that need to be addressed. We searched the Web of Knowledge plus two additional restoration journals not found in the database for empirical papers that assessed restoration projects post‐implementation. We quantified the extent that key attributes of success, including ecological (vegetation structure, species diversity and abundance, and ecosystem functioning) and socioeconomic, were addressed by these papers along with trends in publication and restoration characteristics. Encouragingly, we found the number of empirical evaluations has grown substantially in recent years. The increased age of restoration projects and number of papers that assessed ecological functions since previous reviews of the literature is also a positive development. Research is still heavily skewed toward United States and Australia, however, and identifying an appropriate reference site needs further investigation. Of particular concern is the dearth of papers identified in the literature search that included any measure of socioeconomic attributes. Focusing future empirical research on quantifying ecosystem services and other socioeconomic outcomes is essential for understanding the full benefits and costs of ecological restoration and to support its use in natural resource management .     

A conceptual framework for urban ecological restoration and rehabilitation

Urban greenspace has gained considerable attention during the last decades because of its relevance to wildlife conservation, human welfare, and climate change adaptation. Biodiversity loss and ecosystem degradation worldwide require the formation of new concepts of ecological restoration and rehabilitation aimed at improving ecosystem functions, services, and biodiversity conservation in cities. Although relict sites of natural and semi-natural ecosystems can be found in urban areas, environmental conditions and species composition of most urban ecosystems are highly modified, inducing the development of novel and hybrid ecosystems. A consequence of this ecological novelty is the lack of (semi-) natural reference systems available for defining restoration targets and assessing restoration success in urban areas. This hampers the implementation of ecological restoration in cities. In consideration of these challenges, we present a new conceptual framework that provides guidance and support for urban ecological restoration and rehabilitation by formulating restoration targets for different levels of ecological novelty (i.e., historic, hybrid, and novel ecosystems). To facilitate the restoration and rehabilitation of novel urban ecosystems, we recommend using established species-rich and well-functioning urban ecosystems as reference. Such urban reference systems are likely to be present in many cities. Highlighting their value in comparison to degraded ecosystems can stimulate and guide restoration initiatives. As urban restoration approaches must consider local history and site conditions, as well as citizens’ needs, it may also be advisable to focus the restoration of strongly altered urban ecosystems on selected ecosystem functions, services and/or biodiversity values. Ecosystem restoration and rehabilitation in cities can be either relatively inexpensive or costly, but even expensive measures can pay off when they effectively improve ecosystem services such as climate change mitigation or recreation. Successful re‐shaping and re-thinking of urban greenspace by involving citizens and other stakeholders will help to make our cities more sustainable in the future.     

Ecological Theory and Community Restoration Ecology

Community ecological theory may play an important role in the development of a science of restoration ecology. Not only will the practice of restoration benefit from an increased focus on theory, but basic research in community ecology will also benefit. We pose several major thematic questions that are relevant to restoration from the perspective of community ecological theory and, for each, identify specific areas that are in critical need of further research to advance the science of restoration ecology. We ask, what are appropriate restoration endpoints from a community ecology perspective? The problem of measuring restoration at the community level, particularly given the high amount of variability inherent in most natural communities, is not easy, and may require a focus on restoration of community function (e.g., trophic structure) rather than a focus on the restoration of particular species. We ask, what are the benefits and limitations of using species composition or biodiversity measures as endpoints in restoration ecology? Since reestablishing all native species may rarely be possible, research is needed on the relationship between species richness and community stability of restored sites and on functional redundancy among species in regional colonist “pools.” Efforts targeted at restoring system function must take into account the role of individual species, particularly if some species play a disproportionate role in processing material or are strong interactors. We ask, is restoration of habitat a sufficient approach to reestablish species and function? Many untested assumptions concerning the relationship between physical habitat structure and restoration ecology are being made in practical restoration efforts. We need rigorous testing of these assumptions, particularly to determine how generally they apply to different taxa and habitats. We ask, to what extent can empirical and theoretical work on community succession and dispersal contribute to restoration ecology? We distinguish systems in which succession theory may be broadly applicable from those in which it is probably not. If community development is highly predictable, it may be feasible to manipulate natural succession processes to accelerate restoration. We close by stressing that the science of restoration ecology is so intertwined with basic ecological theory that practical restoration efforts should rely heavily on what is known from theoretical and empirical research on how communities develop and are structured over time.     

Linking ecological function to species composition in ecological restoration: Seed removal by ants in recreated woodland

Evaluations of ecological restoration typically focus on associating measures of structural properties of ecosystems (e.g. species diversity) with time since restoration efforts commenced. Such studies often conclude a failure to achieve restoration goals without examining functional performance of the organism assemblages in question. We compared diversity and composition of ant assemblages and the rates of seed removal by ants in pastures, 4‐ to 10‐year old revegetated areas and remnants of Cumberland Plain Woodland, and an endangered ecological community in Sydney, Australia. Ant assemblages of forest remnant sites had significantly higher species richness, significantly different species composition and a more complex functional group structure in comparison with ant assemblages of pasture and revegetated sites, which did not differ significantly. However, the rates of seed removal by ants in revegetated sites were similar to those in forest remnants, with the rates in pasture sites being significantly lower. Approximately, one‐third of all ant species were observed to remove seeds. Forest remnant sites had significantly different assemblages of seed removing ant species from those in pasture and revegetated sites. These results demonstrate that similar ant assemblages of unrestored and restored areas can function differently, depending on habitat context. Evaluation of restoration success by quantifying ecosystem structure and function offers more insights into ecosystem recovery than reliance on structural data alone.     

Trait-Based Filtering of the Regional Species Pool to Guide Understory Plant Reintroductions in Midwestern Oak Savannas, U.S.A.

A common first step during ecological restoration is reestablishing the local species pool through active reintroduction of individual plant species. Unfortunately, the regional species pool is often far too large to be of practical use during restoration. Methods are needed to produce manageable lists of key species for directed reintroduction. We used life history traits to target species from the regional species pool ( n = 900) for reintroduction to degraded Midwestern oak savanna remnants ( n = 8) in central Iowa, U.S.A. Beginning with the full regional species pool, we first used a priori filters to remove exotic species, species that live in permanently wet habitats, and species already present at the degraded remnant savannas. Next, we created a set of filters to target species with high priority for reintroduction, based on comparisons between the degraded and regional species pools. By this process, we identified perennial forbs and grasses that may be dispersal limited (ant, passive, or heavy wind-dispersed seeds) and are conservative in habitat requirement or have affinities for high-light environments. By applying these filters, we were able to winnow down the regional species pool to a manageable number of species ( n = 111) that we recommend for initial reintroduction efforts to the degraded savanna remnants. Furthermore, we specifically targeted members of the regional species pool that could fill under-represented ecological niches at the degraded savanna remnants and discuss potential benefits of adding these species for restoring ecosystem function.     

Senescent Reservoirs and Ecological Restoration: An Overdue Reality Check

The recent publication of Restoration of Aquatic Ecosystems: Science, Technology, and Public Policy has generated much scientific, public, and political discussion. Although the book emphasizes the restoration of entire aquatic ecosystems, discussion of senescent dams and human-made reservoirs is absent. The important societal and ecological roles of reservoirs warrant a closer examination of the potential ecological restoration of aging reservoirs. Problems with long-term reservoir management include lack of long-term management strategies, sedimentation, hazardous waste accumulation, impacts of recreational use, and the creation of new aquatic and riparian habitats. Policy conflicts may arise when habitats created in the reservoir are destroyed to restore the downstream habitats or when created habitats upstream undergo successional changes that impact the commercial or recreational value of the reservoir. Rare or endangered species may also create similar conflicts. The establishment of an ecological restoration bonding program that includes environmental education and conservation prior to new dam construction may aid in resolving potential conflicts in the future.     

Competitive ability,not tolerance,may explain success of invasive plants over natives

When entering a new community, introduced species leave behind members of their native community while simultaneously forming novel biotic interactions. Escape from enemies during the process of introduction has long been hypothesized to drive the increased performance of invasive species. However, recent studies and quantitative syntheses find that invaders often receive similar, or even more, damage from enemies than do native species. Therefore, invasives may be those more tolerant to enemy damage, or those able to maintain competitive ability in light of enemy damage. Here, we investigate whether tolerance and competitive ability could contribute to invasive plant success. We determined whether invasive plants were more competitive than native or noninvasive exotic species in both the presence and absence of simulated herbivory. We found competition and herbivory additively reduced individual performance, and affected the performance of native, invasive, and noninvasive exotic species’ to the same degree. However, invasives exerted stronger competitive effects on an abundant native species (Elymus canadensis) in both the presence and absence of herbivory. Therefore, while invasive species responded similarly to competition and simulated herbivory, their competitive effects on natives may contribute to their success in their introduced range.     

The importance of ecological memory for trophic rewilding as an ecosystem restoration approach

Increasing human pressure on strongly defaunated ecosystems is characteristic of the Anthropocene and calls for proactive restoration approaches that promote self‐sustaining, functioning ecosystems. However, the suitability of novel restoration concepts such as trophic rewilding is still under discussion given fragmentary empirical data and limited theory development. Here, we develop a theoretical framework that integrates the concept of ‘ecological memory’ into trophic rewilding. The ecological memory of an ecosystem is defined as an ecosystem's accumulated abiotic and biotic material and information legacies from past dynamics. By summarising existing knowledge about the ecological effects of megafauna extinction and rewilding across a large range of spatial and temporal scales, we identify two key drivers of ecosystem responses to trophic rewilding: (i) impact potential of (re)introduced megafauna, and (ii) ecological memory characterising the focal ecosystem. The impact potential of (re)introduced megafauna species can be estimated from species properties such as lifetime per capita engineering capacity, population density, home range size and niche overlap with resident species. The importance of ecological memory characterising the focal ecosystem depends on (i) the absolute time since megafauna loss, (ii) the speed of abiotic and biotic turnover, (iii) the strength of species interactions characterising the focal ecosystem, and (iv) the compensatory capacity of surrounding source ecosystems. These properties related to the focal and surrounding ecosystems mediate material and information legacies (its ecological memory) and modulate the net ecosystem impact of (re)introduced megafauna species. We provide practical advice about how to quantify all these properties while highlighting the strong link between ecological memory and historically contingent ecosystem trajectories. With this newly established ecological memory–rewilding framework, we hope to guide future empirical studies that investigate the ecological effects of trophic rewilding and other ecosystem‐restoration approaches. The proposed integrated conceptual framework should also assist managers and decision makers to anticipate the possible trajectories of ecosystem dynamics after restoration actions and to weigh plausible alternatives. This will help practitioners to develop adaptive management strategies for trophic rewilding that could facilitate sustainable management of functioning ecosystems in an increasingly human‐dominated world.     

Exotic Plant Species as Problems and Solutions in Ecological Restoration: A Synthesis

Exotic species have become increasingly significant management problems in parks and reserves and frequently complicate restoration projects. At the same time there may be circumstances in which their removal may have unforeseen negative consequences or their use in restoration is desirable. We review the types of effects exotic species may have that are important during restoration and suggest research that could increase our ability to set realistic management goals. Their control and use may be controversial; therefore we advocate consideration of exotic species in the greater context of community structure and succession and emphasize areas where ecological research could bring insight to management dilemmas surrounding exotic species and restoration. For example, an understanding of the potential transience of exotics in a site and the role particular exotics might play in changing processes that influence the course of succession is essential to setting removal priorities and realistic management goals. Likewise, a greater understanding of the ecological role of introduced species might help to reduce controversy surrounding their purposeful use in restoration. Here we link generalizations emerging from the invasion ecology literature with practical restoration concerns, including circumstances when it is practical to use exotic species in restoration.     

Shifts in an invasive rodent community favoring Black rats (Rattus rattus) following restoration of native forest

One potential, unintended ecological consequence accompanying forest restoration is a shift in invasive animal populations, potentially impacting conservation targets. Eighteen years after initial restoration (ungulate exclusion, invasive plant control, and out planting native species) at a 4 ha site on Maui, Hawai'i, we compared invasive rodent communities in a restored native dry forest and adjacent non‐native grassland. Quarterly for 1 year, we trapped rodents on three replicate transects (107 rodent traps) in each habitat type for three consecutive nights. While repeated trapping may have reduced the rat (Black rat, Rattus rattus) population in the forest, it did not appear to reduce the mouse (House mouse, Mus musculus) population in the grassland. In unrestored grassland, mouse captures outnumbered rat captures 220:1, with mice averaging 54.9 indiv./night versus rats averaging 0.25 indiv./night. In contrast, in restored native forest, rat captures outnumbered mouse captures by nearly 5:1, averaging 9.0 indiv./night versus 1.9 indiv./night for mice. Therefore, relatively recent native forest restoration increased Black rat abundance and also increased their total biomass in the restored ecosystem 36‐fold while reducing House mouse biomass 35‐fold. Such a community shift is worrisome because Black rats pose a much greater threat than do mice to native birds and plants, perhaps especially to large‐seeded tree species. Land managers should be aware that forest restoration (i.e. converting grassland to native forest) can invoke shifts in invasive rodent populations, potentially favoring Black rats. Without intervention, this shift may pose risks for intended conservation targets and modify future forest restoration trajectories.     

Restoration through reassembly: plant traits and invasion resistance

One of the greatest challenges for ecological restoration is to create or reassemble plant communities that are resistant to invasion by exotic species. We examine how concepts pertaining to the assembly of plant communities can be used to strengthen resistance to invasion in restored communities. Community ecology theory predicts that an invasive species will be unlikely to establish if there is a species with similar traits present in the resident community or if available niches are filled. Therefore, successful restoration efforts should select native species with traits similar to likely invaders and include a diversity of functional traits. The success of trait-based approaches to restoration will depend largely on the diversity of invaders, on the strength of environmental factors and on dispersal dynamics of invasive and native species.     

Ecological effects of invasive alien insects

A literature survey identified 403 primary research publications that investigated the ecological effects of invasive alien insects and/or the mechanisms underlying these effects. The majority of these studies were published in the last 8 years and nearly two-thirds were carried out in North America. These publications concerned 72 invasive insect species, of which two ant species, Solenopsis invicta and Linepithema humile, accounted for 18% and 14% of the studies, respectively. Most publications investigated effects on native biodiversity at population or community level. Genetic effects and, to a lesser extent, effects on ecosystem services and processes were rarely explored. We review the effects caused by different insect invaders according to: their ecosystem roles, i.e. herbivores, predators, parasites, parasitoids and pollinators; the level of biological organisation at which they occur; and the direct and indirect mechanisms underlying these effects. The best documented effects occur in invasive ants, Eurasian forest herbivores invasive in North America, and honeybees. Impacts may occur through simple trophic interactions such as herbivory, predation or parasitism. Alien species may also affect native species and communities through more complex mechanisms such as competition for resources, disease transmission, apparent competition, or pollination disruption, among others. Finally, some invasive insects, particularly forest herbivores and ants, are known to affect ecosystem processes through cascading effects. We identify biases and gaps in our knowledge of ecological effects of invasive insects and suggest further opportunities for research. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.