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.     

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.     

景观生态学与退化生态系统恢复

退化生态系统的恢复是一项艰巨任务,它需要考虑到所要恢复的退化生态系统的结构,多样性和其动态的整体性和长期性。现在对于退化生态系统恢复研究已经要使生态学家们关注受损生态系统的理论和实际问题。退化生态系统恢复所面临的挑战是理解和利用生态演替理论来完成并加速恢复进程。恢复的主要目标是建立一个自维持的,由不同的群落或生态系统组成的能够满足不同需要如生物保护和粮食生产需要的景观。景观生态学关注于大的空间尺度的生态学问题。景观生态学研究方法可以为退化生态系统恢复实践提供指导。在解决退化生态系统的恢复问题时,景观生态学的方法在理论和实践上是有效的。景观生态学中的核心概念和其一般原理斑块形状、生态系统间相互作用、镶嵌系列等都同退化生态系统的恢复有着密切的关系。如恢复地点的选择和适当的恢复要素的空间配置。在评价退化生态系统的恢复是否取得成功,利用景观生态学也具有重要的意义。景观生态学理论如景观格局与景观异质性理论,干扰理论和尺度理论都能够指导退化生态系统的恢复实践。同样地,退化生态系统的恢复可以为景观生态学的研究提供非常恰当的实验场。寓景观生态学思想于退化生态系统恢复过程是一种新的有效途径。     

Science, Art, or Application—the "Karma" of Restoration Ecology

The present state of restoration ecology is far away from Bradshaw’s “acid test for ecology.” The conclusions drawn from the series of papers in this issue and from the Jena workshop suggest some directions in which the field may progress. More attention must be paid to the degraded state, which should be evaluated by its specific features and carefully analyzed before any restoration plan is laid down. Restoration goals have to be realistic, which includes the appreciation of globally changing conditions, resulting in a paradigm‐shift toward “forward‐restoration.” Basically, the transition from the degraded state conditions to the target state is a kind of succession that is manipulated by the application of goal‐orientated and system‐specific disturbances. Whenever possible, restorationists should step back and make use of naturally occurring succession, which requires a sophisticated restoration strategy, involving flexible management responses, multiple alternative target states, robust measurements for the restoration progress, and careful long‐term monitoring. The unique feature of restoration ecology is the involvement of socioeconomic decisions, and conceptual frameworks for ecological restoration have to implement the specific links to natural succession. To bridge the gap between ecological theory and on the ground restoration, it is essential that restoration practice is translated into the vocabulary and thinking of basic ecology. If all these aspects are integrated, ecological restoration as an application—and restoration ecology as an applied science—may develop into an acid test for our understanding of interactions between people and their environment, rather than for pure ecology.     

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.     

Applying trait‐based models to achieve functional targets for theory‐driven ecological restoration

Manipulating community assemblages to achieve functional targets is a key component of restoring degraded ecosystems. The response‐and‐effect trait framework provides a conceptual foundation for translating restoration goals into functional trait targets, but a quantitative framework has been lacking for translating trait targets into assemblages of species that practitioners can actually manipulate. This study describes new trait‐based models that can be used to generate ranges of species abundances to test theories about which traits, which trait values and which species assemblages are most effective for achieving functional outcomes. These models are generalisable, flexible tools that can be widely applied across many terrestrial ecosystems. Examples illustrate how the framework generates assemblages of indigenous species to (1) achieve desired community responses by applying the theories of environmental filtering, limiting similarity and competitive hierarchies, or (2) achieve desired effects on ecosystem functions by applying the theories of mass ratios and niche complementarity. Experimental applications of this framework will advance our understanding of how to set functional trait targets to achieve the desired restoration goals. A trait‐based framework provides restoration ecology with a robust scaffold on which to apply fundamental ecological theory to maintain resilient and functioning ecosystems in a rapidly changing world.     

The Challenge to Restore Processes in Face of Nonlinear Dynamics—On the Crucial Role of Disturbance Regimes

Increasingly, restoration ecologists and managers are challenged to restore ecological processes that lead to self‐sustaining ecosystem dynamics. Due to changing environmental conditions, however, restoration goals need to include novel regimes beyond prior reference conditions or reference dynamics. In face of these fundamental challenges in process‐based restoration ecology, disturbance ecology can offer useful insights. Here, I discuss the contribution of disturbance ecology to understanding assembly rules, ecosystem dynamics, regime shifts, and nonlinear dynamics. Using the patch and multipatch concept, all insights are organized according to two spatial and two temporal categories: “patch–event,”“patch–multievent,”“multipatch–event,” and “multipatch–multievent.” This concept implies the consideration of both spatial patterns and temporal rhythms inside and outside of a restoration site. Emerging issues, such as uncoupling of internal and external dynamics, are considered.     

恢复生态学研究的一些基本问题探讨

对恢复生态学的研究概况、基本概念、内涵与研究内容以及生态恢复的目标、原则、程序与技术进行了分析与探讨。指出恢复生态学应加强基础理论研究(包括生态系统的演替理论及干扰条件下生态系统的受损过程与响应机制研究等)和应用技术研究(包括土壤、水体、大气和植被恢复技术、生物多样性保护技术以及生态系统的组装与集成技术等).生态恢复与重建是指根据生态学原理,通过一定的生物、生态以及工程的技术,人为地切断生态系统退化的主导因子和过程,调整和优化系统内部及其与外界的物质、能量和信息的流动过程及其时空秩序,使生态系统的结构、功能和生态学潜力尽快地成功地恢复到原有的乃至更高的水平。     

A comparative review of recovery processes in rivers, lakes, estuarine and coastal waters

The European Water Framework Directive aims to improve ecological status within river basins. This requires knowledge of responses of aquatic assemblages to recovery processes that occur after measures have been taken to reduce major stressors. A systematic literature review comparatively assesses recovery measures across the four major water categories. The main drivers of degradation stem primarily from human population growth and increases in land use and water use changes. These drivers and pressures are the same in all four water categories: rivers, lakes, transitional and coastal waters. Few studies provide evidence of how ecological knowledge might enhance restoration success. Other major bottlenecks are the lack of data, effects mostly occur only in short-term and at local scale, the organism group(s) selected to assess recovery does not always provide the most appropriate response, the time lags of recovery are highly variable, and most restoration projects incorporate restoration of abiotic conditions and do not include abiotic extremes and biological processes. Restoration ecology is just emerging as a field in aquatic ecology and is a site, time and organism group-specific activity. It is therefore difficult to generalise. Despite the many studies only few provide evidence of how ecological knowledge might enhance restoration success.     

生态环境用水研究现状、问题分析与基本构架探索

生态学与水文学交叉研究是目前国际上前沿研究领域之一,生态环境用水研究则是连接生态过程与水文过程、刻画生态演化与水资源相互关系的核心问题。对生态、环境用水产生与发展的基本过程进行了回顾,并根据对已有成果的综合分析提出了目前研究中存在的5方面主要问题。首先,生态用水尚需理论上的进一步升华,这一点突出体现在生态用水的概念与内涵表述上;其次,在生态用水研究中,缺乏合理的生态保护目标的建立,因而影响到了研究成果的实际应用价值;第三,目前的研究均是针对较大尺度所作的,不能在生态机理与物理机制上揭示生态用水规律,因此,不适于具体问题的深入分析,个别实验在由“点“尺度向生态用水计算的“面“尺度转换时缺乏基础,从而严重影响了研究成果的精度;第四,生态用水机理是生态用水研究中至为关键的工作,以往研究主要依据野外宏观观测资料来探讨,缺乏直接的实验依据;第五,没有涉及生态用水对生态系统稳定性、生态用水满足程度及其波动性对生态系统影响等方面,从而也使得研究成果的科学性受到影响。同时作者认为,中国工程院“中国可持续发展水资源研究报告“中的生态环境用水概念对我国地大物博,地质地貌与气候类型多样的特点给给予了更多的关注,故可以确定为全国性的生态环境用水概念。最后文章认为应当将生态用水与环境用水分别予以考虑,并给出了其新的概念构架。     

Current and Potential Roles of Soil Macroinvertebrates (Earthworms,Millipedes, and Isopods) in Ecological Restoration

Soil macroinvertebrates have a considerable impact on soil functions important to the restoration process, such as decomposition; yet, soil organisms have received relatively little attention in restoration ecology in terms of their applicability as agents of restoration. Here, we review how large obligate detritivores (earthworms, millipedes, and isopods) have been used to accomplish restoration goals, assess restoration progress, and function as bioindicators. Patterns of detritivore community succession and how these communities are themselves restored during restoration of perturbed ecosystems are also discussed. We conclude with a discussion of increased utilization of these taxa in future and ongoing restoration projects as well as the outreach activities that should be associated with use of these organisms.     

The Scale of Successional Models and Restoration Objectives

Successional models are used to predict how restoration projects will achieve their goals. These models have been developed on different spatial and temporal scales and consequently emphasize different types of dynamics. This paper focuses on the restoration goal of self-sustainability, but only in the context of a long-term goal. Because of the temporal scale of this goal, we must consider the impact of processes arising outside of the restoration site as of greater importance than restoration itself. Because ecological systems are open, restoration sites will be subjected to many external influential processes. Depending on the landscape context, the impact of these processes may not be noticeable, or, at the other extreme, they may prevent the achievement of restoration objectives. A second issue is to emphasize the nature of processes in the long term, that they are a complex of characteristics such as magnitude, frequency, and extent. Ecological systems are only adapted to a range of values in each of these characteristics. Restoration often combines goals that are of different scales. Models appropriate to these goals need consideration.     

Response of medium‐ and large‐sized terrestrial fauna to corridor restoration along the middle Sacramento River

A fundamental challenge in restoration ecology is to understand when species are expected to colonize newly created habitat. Determining this is important for assessing progress toward restoration goals and, more generally, for gaining insight into ecosystem functioning and dynamics. We studied this question as it relates to mid‐ to large‐sized terrestrial fauna in restored riparian habitats at the Sacramento River National Wildlife Refuge, in northern California. We used camera traps to document use of 16 riparian corridor sites of varying restoration age. Comparisons of species richness (diversity) and visitation frequency (activity) were made across different‐aged sites. We found that predator diversity and activity levels tended to be higher in restored forests than in remnant forests, and that they tended to be highest in young restored forests. This trend persisted when data from variable sampling periods were pooled, although significant differences occurred more often in wet and cold sampling periods. The trend did not always hold for the animal community at large (consisting of both predator and non‐predator species). We conclude that restoration age affects predator diversity and activity levels in restored and remnant floodplain forests, and that predator communities can establish soon after restoration. Our results suggest that restoring natural river processes that promote habitat regeneration may benefit mid‐ to large‐sized terrestrial predators that appear to mostly use early successional habitat.     

Establishing Baseline Indices for the Quality of the Biodiversity of Restored Habitats Using a Standardized Sampling Process

The need for standardized biodiversity assessment methods to enable biodiversity quality to be measured is outlined. A general approach to sampling is suggested. The results of the use of this sampling process are given for two case studies of different taxonomic groups. The data assessment is made easier by the use of a bespoke computer program. Examples of the program output are presented. The advantage of this standardized measurement of biodiversity compared to species lists and the use of indicator species are outlined in the case studies macrofungi and butterflies. It was shown that the biodiversity quality of sites can be compared by the use of a range of measured biodiversity indices in a way that allows sites to be compared through time or between sites/treatments. In one case (butterflies), data that have been collected systematically in a recording scheme have been analyzed retrospectively and yielded valuable information on changes in biodiversity quality. The uses of this method in establishing baselines in restoration ecology are discussed. The importance of restoration ecology in the conservation of biodiversity could be underlined by the use of the methods presented in this article.     

Restoration Ecology: Repairing the Earth's Ecosystems in the New Millennium

The extent of human‐induced change and damage to Earth's ecosystems renders ecosystem repair an essential part of our future survival strategy, and this demands that restoration ecology provide effective conceptual and practical tools for this task. We argue that restoration ecology has to be an integral component of land management in today's world, and to be broadly applicable, has to have a clearly articulated conceptual basis. This needs to recognize that most ecosystems are dynamic and hence restoration goals cannot be based on static attributes. Setting clear and achievable goals is essential, and these should focus on the desired characteristics for the system in the future, rather than in relation to what these were in the past. Goal setting requires that there is a clear understanding of the restoration options available (and the relative costs of different options). The concept of restoration thresholds suggests that options are determined by the current state of the system in relation to biotic and abiotic thresholds. A further important task is the development of effective and easily measured success criteria. Many parameters could be considered for inclusion in restoration success criteria, but these are often ambiguous or hard to measure. Success criteria need to relate clearly back to specific restoration goals. If restoration ecology is to be successfully practiced as part of humanity's response to continued ecosystem change and degradation, restoration ecologists need to rise to the challenges of meshing science, practice and policy. Restoration ecology is likely to be one of the most important fields of the coming century.     

Plants for nitrogen management in riparian zones: A proposed trait‐based framework to select effective species

Restoring plants to the riparian zone is regarded as management best practice in river restoration and has the potential to reduce the impact of nitrogen (N) pollution on aquatic organisms and improve water quality for human use. Plant characteristics and the interplay of hydrology and biogeochemistry control N retention in the riparian zone. The balance between processes such as denitrification and plant assimilation determines riparian N retention. Plant traits are likely to mediate these N removal processes through variations in root form, growth character, foliage production (quantity, quality and rate of return to the soil) and by altering conditions in the rhizosphere soil. Vegetation can slow N transfer via direct plant uptake of N (during periods of rapid vegetation growth) and changes induced to soil hydrology, nutrient cycling and microbial activity, principally denitrification. Few studies have focused on species‐dependent effects on N movement through soil and across boundaries. We propose a new framework, based on a literature review of plant traits with respect to N cycling, which can be used to select plant species with traits likely to maximise N removal during transport through the riparian zone. In the proposed framework, inter‐specific differences in traits known to influence N mobility: root form, growth rate, foliar characteristics and rhizosphere processes, are used to describe species’ potential impact on N removal. Plant trait data may be drawn from studies outside the riparian zone; for example forest ecology, horticulture or forestry research, and candidate species are scored to predict N removal efficiency. We apply the framework to New Zealand's native riparian plant assemblages to demonstrate the trait‐based approach. This framework can guide restoration management decisions and investment in riparian revegetation in a manner that is not restricted to geographically specific or well‐studied species.     

Defining the Limits of Restoration: The Need for Realistic Goals

The search for a universal statement of goals for ecological restoration continues to generate discussion and controversy. I discuss the diverse roots of restoration ecology, and show how the complex lineages within the field have led to diverse, and divergent, sets of goals. I then review the three major themes that currently are used to develop statements of goals: restoration of species, restoration of whole ecosystems or landscapes, and the restoration of ecosystem services, and point out both the advantages and the limitations and problems associated with each category. Finally, I suggest that restoration ecology would be better served by recognizing that the diversity of conditions requiring restoration demands much flexibility in goal setting, and that restorationists should seek to develop guidelines for defining the sets of conditions under which different kinds of goals are appropriate. I further suggest that goals would be more easily and more appropriately set if restorationists would set forth at the outset the true scope and limitations of what is possible in a given project. Key words: goal‐setting, wetlands, conservation biology, ecosystem management, ecosystem services, landscape management.     

火对森林主要生态系统过程的影响

火及火生态学是当代生态系统生态学研究最为深入的领域之一.理解火生态效应及其基本原理,对降低野火灾害并适当利用火作为一种有效管理手段起着关键的作用.本文介绍了目前火对若干具倾火性的生态系统（尤其是位于北美的寒温带及温带森林生态系统）影响的研究进展,并着重论述了火作为一种主导性的力量在植被动态、养分循环、土壤及水分关系的紧密关联过程中所起的作用.火通过以下主要过程影响生态系统的组成、结构和功能,即选择性地保留和去除物种,释放贮于生物量中的养分且增进其循环,藉改变土壤微生物活动及水分关系等影响土壤性能,并形成异质的时空环境镶嵌格局,而这些变化反过来又进一步影响火行为及其生态效应.火作为一种毁灭性的力量能迅速消耗大量生物量,并导致继后的土壤侵蚀、水土流失和空气污染等负面影响;但火作为一种建设性力量,对维持一些对火有依赖性的生态系统的健康及持续具有极重要的作用.考虑到火在生态系统过程中的独特调节作用,火应被视为生态系统及其管理中有机组分之一.火对生态系统的影响取决于火情势（包括火发生的季节、规模大小、频率及强度等）、植被类型、气候条件、物理环境及评价所用的时空尺度.未来有必要加强有关火对一些特定生态系统的作用研究,尤其是基于长期试验性的监测和模型来研究火对生态系统时空变化的影响.     

Restoration Ecology to the Future: A Call for New Paradigm

The discipline of restoration ecology has grown remarkably in the past decades, providing new ideas and opportunities for conserving biological diversity, managing ecosystems, and testing ecological theories. On the other side, its past‐oriented, static, and idealistic approach has been criticized for subjectivity in determining restoration goals, inapplicability to dynamic ecosystems, and inability for restoring certain irreversible losses. Moreover, unpredictable sustainability of the restored ecosystems, which were modeled after its historical fidelity, adds our skepticism under the changing environment. This paper calls for a new paradigm of ecological restoration to the future. A future‐oriented restoration should (1) establish the ecosystems that are able to sustain in the future, not the past, environment; (2) have multiple alternative goals and trajectories for unpredictable endpoints; (3) focus on rehabilitation of ecosystem functions rather than recomposition of species or cosmetics of landscape surface; and (4) acknowledge its identity as a “value‐laden” applied science within economically and socially acceptable framework. Applicability of ecological theories to restoration practice is also discussed in this paper.     

Rewilding with invertebrates and microbes to restore ecosystems: Present trends and future directions

1. Restoration ecology has historically focused on reconstructing communities of highly visible taxa while less visible taxa, such as invertebrates and microbes, are ignored. This is problematic as invertebrates and microbes make up the vast bulk of biodiversity and drive many key ecosystem processes, yet they are rarely actively reintroduced following restoration, potentially limiting ecosystem function and biodiversity in these areas.
2. In this review, we discuss the current (limited) incorporation of invertebrates and microbes in restoration and rewilding projects. We argue that these groups should be actively rewilded during restoration to improve biodiversity, ecosystem function outcomes, and highlight how they can be used to greater effect in the future. For example, invertebrates and microbes are easily manipulated, meaning whole communities can potentially be rewilded through habitat transplants in a practice that we refer to as “whole‐of‐community” rewilding.
3. We provide a framework for whole‐of‐community rewilding and describe empirical case studies as practical applications of this under‐researched restoration tool that land managers can use to improve restoration outcomes.
4. We hope this new perspective on whole‐of‐community restoration will promote applied research into restoration that incorporates all biota, irrespective of size, while also enabling a better understanding of fundamental ecological theory, such as colonization and competition trade‐offs. This may be a necessary consideration as invertebrates that are important in providing ecosystem services are declining globally; targeting invertebrate communities during restoration may be crucial in stemming this decline.