Plant-herbivore interaction is one of the most common and important interspecific relationships in nature, which is the core and foundation of the food web theory. In this paper, we review the effects of herbivores on the characteristics of plant individuals, populations and communities, as well as the defense strategies and mechanisms of plants against herbivores at the levels of individuals, populations and communities. Herbivory can significantly change the growth, reproduction and survival rates of plant individuals and populations, which can in turn affect the composition and diversity of plant communities. In order to defend against herbivory, plants have evolved a series of defense mechanisms at the individual, population and community levels. At the individual and population levels, plants avoid herbivory mainly by chemical and physical defense. At the community level, however, plant defenses are achieved mainly by their influences on the behaviors of herbivores. This paper then introduces and compares important hypotheses and theories in related fields. Finally, we point out major existing research issues and identify possible future research directions. Given that natural systems are experiencing strong disturbances from human activities and climate changes, exploring how these disturbances affect plant-animal interactions, and how these changes in plant-animal interactions feedback on the structure, function and stability of the ecosystems, will not only have important theoretical significance, but also help us to formulate successful ecosystem management policy in the future.

Varied species interactions form complex species interaction networks in diverse ecological communities. Understanding how the network structure affects ecosystem functions and community stability is one major issue for community ecology. Species interactions can directly affect the flow and circulation of matter and energy among different components of ecosystems. As a result, the network structure is closely related to the structure, stability, and functioning of ecological communities. Prior studies on interaction networks have shed light on community assembly, biodiversity maintenance, ecosystem stability, coevolution and trait diversification. Currently, biodiversity and ecosystem functions have been largely affected by global environmental changes. The interaction networks and their relationship with biodiversity loss in a changing world have become important research topics. Exploring the structure and assembly of species interaction networks, stability, and ecosystem functions is significant for understanding the maintenance mechanism and biodiversity conservation. Here, we reviewed the research advances in the structure of ecological networks and their determinants, network stability, the relationship between network and ecosystem functions, and the mechanisms underlying these relationships. We also suggest future research directions on how to apply machine learning and multilayer network to disentangle the effects of environmental change on network structure and ecosystem functions by integrated theoretical and empirical studies.

The food web sustains its structure mainly by bottom-up and top-down regulations of the species interactions among different trophic levels. However, global changes can alter interspecific relationships and threaten the maintenance of biodiversity. It is still unclear how global change alters the structure of the food webs. In recent years, based on numerous studies on food webs composed of multi-trophic levels at large spatiotemporal scales, researchers have found that global changes alter food web structure mainly through three mechanisms: phenological mismatching, loss of key species and biological invasion. Here we focused on these three mechanisms and reviewed how these mechanisms regulate food web structure change, with further discussions on the driving factors in ecology and evolution. All these three mechanisms can alter the interspecific interactions, resulting in distortion of the regulation of food webs. The major difference among these three mechanisms is how interspecific interactions are changed. Phenological mismatching occurs due to the asynchronous responses in the phenology of different species to global changes, while the loss of key species can change or even entirely destroy some critical feeding/predation relationships, and invasive species often simplify the food web structure by causing strong interspecific competition to exclude species at the same trophic level. Finally, we pointed out that the changes in food web structure actually depend on the adaptation of species to the ongoing global changes and we further provided some insights into future research directions. With aggravated global change impacts, it is necessary to further study the mechanisms underlying how global changes influence food web structure, to reinforce the extant theoretical basis for formulating biodiversity conservation and ecological restoration measures.

Under intensifying human activities and climate change, spatiotemporal changes in ecosystem composition and structure are becoming increasingly drastic and intricate, and there are trends of degradation in many ecosystems. An improved understanding of ecosystem dynamics and their underlying mechanisms in the context of global change can not only help resolve fundamental theoretical questions in ecology, but can also inform applied issues in ecosystem restoration and conservation. Here, we review different models of ecosystem dynamics (gradual continuum, threshold/regime shift, and stochastic) and conceptualize the mechanisms by which biotic interactions can potentially modulate ecosystem dynamics. We then synthesize the state of understanding how biotic interactions regulate secondary succession, regime shift, and species range shift—ecosystem dynamics subject to intense recent investigation. We further discuss results from studies that applied theories on biotic interactions in ecosystem restoration and conservation. We show that there is a growing body of research revealing 1) that multiple types of biotic interactions, such as competition, facilitation (including mutualism), and trophic interactions, can drive or substantially alter the patterns, directions, and rates of ecosystem change at various spatiotemporal scales, and 2) that managing biotic interactions is likely to greatly enhance the performance of ecosystem restoration and conservation. To move forward, we highlight that further research is needed to better understand how the impacts of biotic interactions on ecosystem dynamics vary spatially and temporally, how biotic interactions modulate ecosystem dynamics under multiple anthropogenic disturbances, and how best to manage biotic interactions to optimize ecosystem conservation and restoration.

Over the recent decade, biodiversity and ecosystem multifunctionality (BEMF) has aroused as an emerging reserach hotspot in the filed of biodiversity and ecosystem functioning. Ecosystem multifunctionality is defined as the capacity of an ecosystem to provide multiple ecosystem functions simulateneously, it has received broad consideration by community and ecosystem ecologists. In this study, we first conducted a literature review of the research history in biodiversity and ecosystem multifunctionality. Next, we summarized the major trends in biodiversity and ecosystem multifunctionality research including the impacts of biodiversity dimensions, global change drivers and spatial-temporal scales on ecosystem multifunctionality. We reviewed the new research methods and research directions emerged in the field. We also defined a new concept, i.e., ecosystem multiserviceability (EMS) based on the distinction between ecosystem functions and ecosystem services. Finally, we briefly summarized the limitations in current research of biodiversity and ecosystem multifunctionality/multiserviceability (BEMF/BEMS) and presented the outlook for future study.

Global change has exerted profound impacts on ecosystem function, such as variations in plant productivity and imbalances in nutrient cycling. Previous studies mostly focused on the impacts of global change on individual functions. However, ecosystems have multiple functions, known as ecosystem multifunctionality (EMF), such that the evaluation based on a single functionality is inappropriate to reflect the overall performance of ecosystems due to the occurrence of trade-offs or synergies among the differential functions. This imposes limitation to our understanding of the effects of global change on ecosystems. Since the initial quantitative study of EMF by Hector and Bagchi in 2007, this field of research has undergone rapid development and the environmental impacts on EMF have received wide attention with intensification of global change. In order to gain systematic understanding of the progress in EMF studies, we conducted a bibliometric analysis for the period 2007-2020 based on CNKI and ISI Web of Science databases. This paper provides a brief description of the development in EMF research and summary of studies concerning the impacts of land use change, warming, changes in precipitation, and nitrogen deposition on EMF. We raised six issues of further attention in future studies of EMF in the context of global change, including (1) requirement of consensus in EMF indices and evaluation method; (2) consideration on the interactive effects among different factors on EMF; (3) elucidation of EMF responses to global change across various temporal scales; (4) understanding of the relationships between multi-dimensional, multi-scale biodiversity and EMF; (5) understanding of the relationships between multiple trophic diversity and EMF; and (6) understanding of the relationships between root functional traits and EMF.

The stability of ecosystems determines whether they can sustainably provide key functions and services in the background of global changes. Ecosystem stability, particularly its relation with biodiversity, is one of the central issues in ecology. Whether biodiversity enhances or impairs ecosystem stability has historically aroused much debate. Based on early reviews and studies on different aspects of stability, here we summarized recent advances from three aspects. Firstly, several recent theoretical studies offered novel insights in understanding the multi- dimensionality of stability and the intrinsic link between different stability measures, and we provided an overview on these new insights. Secondly, we reviewed recent empirical and theoretical studies on biodiversity- stability relationships, including those in the context of multidimensional stability. Thirdly, we introduced the recently developed multi-scale stability framework, which provides new opportunity to understand the scaling of stability and extend diversity-stability relations to a multi-scale context. We ended with a discussion on future research questions and directions.

Comprehensively understanding the mechanisms underlying the formation of ecosystem services is a prerequisite for maintaining the sustainable supply of ecosystem services. Plant functional traits directly participate in a variety of ecosystem processes, which in turn affect the supply of ecosystem services. Revealing the relationship between plant functional traits and ecosystem services is an important way to understand the formation mechanism of ecosystem services. Based on a systematic literature review, 86 papers on plant functional properties and ecosystem services were retrieved in the Web of Science database, and data for 466 pairs of plant functional traits and ecosystem services and 83 plant functional traits were collected. The current status of research on the relationship between plant functional traits and ecosystem services was revealed. Moreover, the main plant functional traits that affect different ecosystem services and their mechanisms underlying their impacts were also demonstrated. The results show that the research on the relationship between plant functional traits and ecosystem services mostly focuses on natural ecosystems such as grasslands and forests. Most of these studies focus on ecosystem products providing and supporting services, including biomass, net primary productivity, and soil fertility. Based on the impacts of plant functional traits on different ecosystem services, the plant functional traits can be clustered into five categories: soil-conservation-related traits, water-cycle-related traits, ecosystem- multifunction- related traits, product-providing-related traits, and pollination-biocontrol-related traits. The impacts of climate change, human activities, and variations in spatial and temporal scales on the relationship between plant functional traits and ecosystem services need to be further explored.

Leaf is one of the important organs of plants that facilitates the exchange of water and air with the surrounding environment. The morphological variation of leaves directly affect the physiological and biochemical processes of plants, which also reflects the adaptive strategies of plants to obtain resources. By focusing on several leaf morphological traits, including leaf size, leaf shape, leaf margin (with or without teeth) and leaf type (i.e. single vs. compound leaf), here, we reviewed the relevant research progresses in this field. We summarized the ecological functions of leaf morphological traits, identified their geographical distribution patterns, and explored the underlying environmental drivers, potential ecological interactions, and their effects on ecosystem functioning. We found that the current studies exploring the distribution and determinants of leaf size and leaf margin states mainly focused on single or specific taxon in local regions. Studies have also explored the genetic mechanisms of leaf morphology development. Leaf traits trade off with other functional traits, and their spatial variation is driven by both temperature and water availability. Leaf morphological traits, especially leaf size, influence water and nutrient cycling, reflect the response of communities to climate change, and can be scaled up to predict ecosystem primary productivity. Further studies should pay attention to combine new approaches to obtain unbiased data with high coverage, to explore the long-term adaptive evolution of leaf morphology, and to generalize the scaling in leaf morphology and its effect on ecosystem functioning. Leaf provides an important perspective to understand how plants respond and adapt to environmental changes. Studying leaf morphological traits provides insight into species fitness, community dynamics and ecosystem functioning, and also improves our understanding of the research progresses made in related fields, including plant community ecology and functional biogeography.