Economic loss versus ecological gain: the outbreaks of invaded pinewood nematode in China

Pinewood nematode is native to North America and has been a deadly exotic pest infecting pine forests in Japan since the 1900s. It was first recorded in 1982 in subtropical China and has since aggressively spread to 113 counties and 14 provinces. As of 2007 the disease has infected over one million hectares of pine forests and 44 million pine trees in China 1982–2007. Besides inspection and quarantine, the main policy to control this disease is to eradicate the infected pines, which is costly and only partially effective. We investigated the community structure of four Pinus massoniana plantations with similar age and site conditions that were infested by pinewood nematode at different times (0, 4, 8, and 12 years), with the community structure in a zonal evergreen broad-leaved forest nearby. Our results demonstrate that the pinewood nematode infection accelerated the succession from the native pine plantations with higher economical values to the zonal evergreen broad-leaved forests which provide more ecological services. The conversion of pine plantations to natural forests is an urgent challenge facing China today. Thus, the infestation of pinewood nematode provides a unique opportunity for the conversion of the pine-dominated plantations and forests into broad-leaved forests and we therefore suggest that the government should invest its limited resources based on an appropriate trade-off between economic loss and ecological gain.     

Allelopathic adaptation can cause competitive coexistence

The maintenance of plant diversity is often explained by the ecological and evolutionary consequences of resource competition. Recently, the importance of allelopathy for competitive interactions has been recognized. In spite of such interest in allelopathy, we have few theories for understanding how the allelopathy influences the ecological and evolutionary dynamics of competing species. Here, I study the coevolutionary dynamics of two competing species with allelopathy in an interspecific competition system, and show that adaptive trait dynamics can cause cyclic coexistence. In addition, very fast adaptation such as phenotypic plasticity is likely to stabilize the population cycles. The results suggest that adaptive changes in allelopathy can lead to cyclic coexistence of plant species even when their ecological characters are very similar and interspecific competition is stronger than intraspecific competition, which should destroy competitive coexistence in the absence of adaptation.     

Plant allelochemical interference or soil chemical ecology?

While allelopathy has been defined as plant-plant chemical interference, there has been much confusion about what the concept encompasses and how important it is in nature. We distinguish between (1) direct plant-plant interference mediated by allelochemicals, and (2) the effects of secondary compounds released by plants on abiotic and biotic soil processes that affect other plants.It very difficult to demonstrate direct effects of chemicals released by a plant on nearby plants. Although soil ecology-mediated effects of secondary plant compounds do not fit the classical concept of allelopathy, we find support in the literature for the hypothesis that the most important effects of compounds released into the soil environment by plants on other plants occur through such indirect effects. The emphasis on, and skepticism of, direct plant-plant allelopathic interference has led some researchers to demand unreasonably high standards of evidence for establishing even the existence of allelopathic interactions, standards that are not demanded for other plant-plant interactions such as resource competition. While the complete elucidation of the mechanisms by which allelochemicals function in the field is many years away, such elucidation is not necessary to establish the existence of allelopathic interactions.We propose that most of the phenomena broadly referred to as allelopathic interference are better conceptualized and investigated in terms of soil chemical ecology. Even when direct plant-plant allelochemical interference occur, the levels of allelochemicals in the environment and their effects on plants are heavily influenced by abiotic and biotic components of the soil ecosystem. Putting allelopathy in the context of soil ecology can further research and reduce some of the less fruitful controversy surrounding the phenomenon.     

Developing an ecological context for allelopathy

There has been a renewed interest in allelopathy as a plant–plant interaction as more plant ecologists have become involved in studying biological invasions. This resurgence highlights a major deficiency in our understanding of allelopathy—the lack of a well-developed ecological context for the interaction. In contrast to allelopathy, the plant–plant interaction of competition has a strong theoretical foundation as well as a large body of supporting empirical studies. We suggest that the plant-herbivore defense literature provides a mature and well-developed framework from which a broader ecological context for allelopathy can be developed. Here, we discuss three broad classes of questions, drawn from the herbivore defense literature, which may help to develop an appropriate ecological context for allelopathy. These questions focus on (1) variation in allelopathic expression within species, (2) community level variation in allelopathy across species, and (3) variation in the impacts of allelopathy on associated species. Addressing such broad population and community level themes in a variety of systems will be necessary to fully develop an ecological context for allelopathy and provide a theoretical basis for understanding its role in plant communities.     

Rice allelopathy and the possibility for weed management

In attempts to control weeds in rice, much effort has been focused on rice allelopathy research for more than 30 years. Among screening methods that have been developed, some estimate the allelopathic potential of various rice cultivars in a limited time and space, which is less costly and can be conducted year round. Rice allelopathy activity is variety dependent and origin dependent, where Japonica rice shows greater allelopathic activity than Indica and Japonica–Indica hybrids. Allelopathic characteristics in rice are quantitatively inherited and several allelopathy‐involved traits have been identified. Numerous phytotoxins such as cytokinins, diterpenoids, fatty acids, flavones, glucopyranosides, indoles, momilactones (A and B), oryzalexins, phenols, phenolic acids, resorcinols and stigmastanols have been identified and determined as growth inhibitors in rice. However, the fate and actual modes of action of these compounds as well as other potent rice phytotoxins in nature are not well understood. The question of which compounds play a major role in rice allelopathy has remained obscure; however, rice allelopathy might be attributable to the interaction of all present allelochemicals. Despite locating genes determining or involving allelopathy in rice having attracted much effort, the introduction of these genes into target rice cultivars has not yet been achieved. Success in breeding new rice cultivars having good weed‐suppressing ability would benefit farmers in rice‐cultivating countries and play an important role in sustainable agricultural production.     

Geomorphology of Australian estuaries: Review and prospect

Over the past 30 years there has been a wealth of research examining the geomorphology of Australian estuaries. This paper reviews the major regional controls on estuarine geomorphic development and discusses the focus of research efforts to understand estuarine evolution, configuration and processes controlling geomorphic development and change. The presence and position of estuaries along the Australian coastline is controlled by large-scale climate-led changes in sea-level, the antecedent structure of the coast and tectonic activity. The configuration of Australia’s estuaries is controlled by a number of environmental factors identified by 34 including climate, oceanographic regime, sediment availability, structure and mineralogy, and tectonics. Interaction of these factors produce a range of estuarine configurations around the Australian continent from wave-dominated, microtidal, bar-built estuaries in the south to low energy macrotidal estuaries in the north which have produced extensive low-lying coastal plains. The principle focus of geomorphologists during the past 30 years has been understanding the medium to long-term development of estuaries in response to fluctuating sea-level over the past 125 000 years. Classifications and models of estuarine development and associated biological community response to estuary development have been identified based on lateral and vertical sedimentary sequences. Results have provided essential information on the physical resources and characteristics of estuarine systems including the distribution of sediment facies that host a variety of different ecological communities. There has been a paucity of research examining contemporary processes controlling geomorphic change in Australia’s estuaries. A morphodynamic approach to the study of estuaries is advocated that evaluates morphology-process responses as estuaries evolve. This approach requires increased research efforts to identify regional differences in estuarine geomorphic development, hydrodynamic processes and sedimentation. It is also advocated that studies examine how the morphodynamic behaviour of estuaries over thousands of years has influenced estuary ecology. Such studies will provide a more complete understanding of the factors influencing the morphology and ecology of contemporary estuaries.     

Developing an ecological context for allelopathy

There has been a renewed interest in allelopathy as a plant?Cplant interaction as more plant ecologists have become involved in studying biological invasions. This resurgence highlights a major deficiency in our understanding of allelopathy??the lack of a well-developed ecological context for the interaction. In contrast to allelopathy, the plant?Cplant interaction of competition has a strong theoretical foundation as well as a large body of supporting empirical studies. We suggest that the plant-herbivore defense literature provides a mature and well-developed framework from which a broader ecological context for allelopathy can be developed. Here, we discuss three broad classes of questions, drawn from the herbivore defense literature, which may help to develop an appropriate ecological context for allelopathy. These questions focus on (1) variation in allelopathic expression within species, (2) community level variation in allelopathy across species, and (3) variation in the impacts of allelopathy on associated species. Addressing such broad population and community level themes in a variety of systems will be necessary to fully develop an ecological context for allelopathy and provide a theoretical basis for understanding its role in plant communities.     

Algal allelopathy

The comprehensive review on allelopathy (Rice, 1979, 1984) has been largely responsible for the evolution of allelopathy as an independent branch of chemical/ physiological ecology. The allelopathic research during the last four decades drew attention to different facets of the interactions among the constituents of habitat, calling for an understanding of the role of allelopathy under different habitat conditions. In view of this, we have reviewed the existing information on allelopathic interactions in aquatic habitats with special reference to algal allelopathy. This review has been mainly confined, therefore, to different aspects of algal allelopathy such as allelopathic interactions in algae, algal toxins, bioassays, and implications of algal allelopathy. In spite of the large number of reviews on allelopathy (see section III), no independent review appears on algal allelopathy. Although there were reports of toxins from cyanobacteria and other algae, no appreciable attempt was made to implicate algal toxins in allelopathy under field conditions. Knowledge of chemistry and biology of allelochemical can help in their potential use in controlling plant diseases and weeds. Therefore, it is urgent to study algal toxins for their involvement in ecological phenomena such as succession, for their uses as herbicides, weedicides, and pesticides, for their uses in solving some of the problems of algal ecology, and for their involvement in applied aspects.     

The Holocene biogeography of Pinus sabiniana Douglas ex D. Don (gray pine) in California

Pinus sabiniana Douglas ex D. Don (gray pine) is one of the dominant species in the ubiquitous Gray Pine-Blue Oak Woodland that rings the Great Central Valley of California. The species is absent, however, in a nearly 100 km section of the Sierra Nevada foothills between the Kings and Kaweah rivers. We test several previous explanations for this biogeographic gap, including prehistoric and historic anthropogenic burning, Early Holocene pluvial lakes as a migration barrier, and unique topography as a limiting factor. Through the examination of archaeobotanical and radiocarbon evidence, we find that gray pine distribution has been stable for the past 4,000 years and likely longer. Importantly, gray pine is absent in 44 of 45 individual samples from the Wahtoke Creek Site, the only archaeological site with archaeobotanical data within the modern distribution gap. This suggests that gray pine has been largely absent from the gap for over 6,000 years and refutes several previous explanations for the biogeographical gap. Instead, data support a topographical or ecological peculiarity of the gap rather than historic or prehistoric anthropogenic burning, or an Early Holocene migration of the species that was blocked by bodies of water in the Central Valley.     

蕨类植物的化感作用及其对生物多样性的影响

植物化感作用是植物通过向环境中释放化学物质从而对同种植株和繁殖体或与其他植物之间产生的直接或间接、有益或有害的作用,它影响植物分布、群落形成与演化、作物间作等,与生物多样性保护以及农林和园艺生产实践关系密切,在国际上受到越来越多的关注。但国内这方面的研究起步相对较晚,研究范围有限,对蕨类植物化感作用的报道更少。本文系统介绍了蕨类植物化感作用的研究进展,包括蕨类植物种内的化感作用(即自毒效应)、常见的蕨类植物种间的化感作用(即孢子体对配子体的化感作用和配子体对配子体的化感作用)及蕨类植物对种子植物的化感作用(蕨类植物可通过化感作用与种子植物争夺更多的资源和生长空间)。还介绍了种子植物对蕨类植物的化感作用(主要表现为抑制作用)以及蕨类植物化感作用与动物侵食、微生物侵染的关系,研究发现昆虫侵食能增强或减弱蕨类植物的化感作用,微生物的活动可能增强某些蕨类植物的化感作用。本文从上述不同角度说明蕨类植物化感作用对生物多样性的影响,希望有助于促进我国学者对该领域的深入研究。     

Experimental designs for the study of allelopathy

The primary aim of this paper is to discuss the methodological approaches that may best develop studies of allelopathy in the future. Laboratory studies on the functions of isolated chemicals, no matter how mechanistically detailed, cannot demonstrate the significance of allelopathy in communities. Evidence for allelopathy in natural plant communities should include information of concentrations and release rates such as demonstrated in field soils for (±)-catechin and Centaurea maculosaLam. Community-relevant evidence for allelopathy should include some manipulation of exudates such as performed in many experiments with activated carbon and gel filtration columns. Realistic evidence for allelopathy should include separation of resource effects from chemical effects; such as demonstrated by experiments with activated carbon additions, density-dependent responses to additions of competitors and chemicals, and resource addition treatments. Community-relevant evidence should link laboratory effects to field patterns and experiments; such as the links between the inhibitory effects of roots of Larrea tridentataCov., the highly spatially segregated root systems and regular above-ground spacing of this species, strong spatial disassociation of L. tridentata with other species, and removal experiments indicating that segregation of L. tridentata root systems via allelopathy may feed back to sequestering of resource use. Studies of allelopathy should consider chemically initiated shifts in microbial populations, and the effects of organic and inorganic soil components on the function of exudates; which has been done in a number of studies. Finally, studies of allelopathy should include large-scale manipulation of chemical effects; such as performed in field experiments in boreal forests in Sweden with Empetrum hermaphroditumHagerup and Scots pine (Pinus sylvestrisL.). Demonstrating the occurrence and importance of chemically mediated interactions among plants is not trivial. If even a small portion of the thousands of chemicals produced by different plant species have effects on their neighbours, then species-specific interactions, natural selection, community integration, and community coevolution may be quite different than predicted by conceptual models based solely on resource competition. Appropriate methodology is crucial for integrating chemically mediated interactions into ecological theory.     

Terrestrial and aquatic responses to climate change and human impact on the southeastern Tibetan Plateau during the past two centuries

Rapid population growth and economic development have led to increased anthropogenic pressures on the Tibetan Plateau, causing significant land cover changes with potentially severe ecological consequences. To assess whether or not these pressures are also affecting the remote montane‐boreal lakes on the SE Tibetan Plateau, fossil pollen and diatom data from two lakes were synthesized. The interplay of aquatic and terrestrial ecosystem response was explored in respect to climate variability and human activity over the past 200 years. Nonmetric multidimensional scaling and Procrustes rotation analysis were undertaken to determine whether pollen and diatom responses in each lake were similar and synchronous. Detrended canonical correspondence analysis was used to develop quantitative estimates of compositional species turnover. Despite instrumental evidence of significant climatic warming on the southeastern Plateau, the pollen and diatom records indicate very stable species composition throughout their profiles and show only very subtle responses to environmental changes over the past 200 years. The compositional species turnover (0.36–0.94 SD) is relatively low in comparison to the species reorganizations known from the periods during the mid‐ and early‐Holocene (0.64–1.61 SD) on the SE Plateau, and also in comparison to turnover rates of sediment records from climate‐sensitive regions in the circum arctic. Our results indicate that climatically induced ecological thresholds are not yet crossed, but that human activity has an increasing influence, particularly on the terrestrial ecosystem in our study area. Synergistic processes of post‐Little Ice Age warming, 20th century climate warming and extensive reforestations since the 19th century have initiated a change from natural oak‐pine forests to seminatural, likely less resilient pine‐oak forests. Further warming and anthropogenic disturbances would possibly exceed the ecological threshold of these ecosystems and lead to severe ecological consequences.     

Positive interactions among plants

Experimental evidence for positive interactions, or facilitation, among plants has increased markedly during the last 10 years. Experiments documenting facilitation have been conducted in many diverse ecological systems, which suggests that positive interactions may be fundamental processes in plant communities. Here, I review the evidence for facilitation, the mechanisms by which facilitation operates, and the effects facilitation has on community structure. Facilitative mechanisms may act simultaneously with resource competition or allelopathy, and the overall effect of one species on another may be the product of multiple, complex interactions. Positive interactions may also determine community spatial patterns, permit coexistence, enhance diversity and productivity, and drive community dynamics. Once viewed as anecdotal and idiosyncratic, facilitation is now contributing to a more complete understanding of community structure and dynamics.     

生态恢复中生态系统服务的演变:趋势、过程与评估

经过10余年的发展,生态系统服务已经成为生态恢复研究关注的前沿和热点。生态恢复改变了生态系统格局与过程,对生态系统服务的产生和提供具有重要影响。但是目前对于生态系统服务在生态恢复过程中的演化仍缺少系统性研究。对国内外相关研究的最新成果进行综述,总结了生态系统服务评估中框架的构建和方法的选择(参数转移法、系统模型法和定量指标法),介绍了生态恢复对生态系统服务的促进作用、生态系统服务的演变过程以及不同生态系统服务间的协同与权衡关系,分析了社会经济因素对生态恢复和生态系统服务维持的影响。最后结合我国生态恢复实践,提出未来生态恢复和生态系统服务研究可以从深化作用机制研究、推动服务评估创新、增强研究成果应用3方面深化和拓展。     

Marine sponges and their microbial symbionts: love and other relationships

Many marine sponges harbour dense and diverse microbial communities of considerable ecological and biotechnological importance. While the past decade has seen tremendous advances in our understanding of the phylogenetic diversity of sponge-associated microorganisms (more than 25 bacterial phyla have now been reported from sponges), it is only in the past 3-4 years that the in situ activity and function of these microbes has become a major research focus. Already the rewards of this new emphasis are evident, with genomics and experimental approaches yielding novel insights into symbiont function. Key steps in the nitrogen cycle [denitrification, anaerobic ammonium oxidation (Anammox)] have recently been demonstrated in sponges for the first time, with diverse bacteria - including the sponge-associated candidate phylum 'Poribacteria'- being implicated in these processes. In this minireview we examine recent major developments in the microbiology of sponges, and identify several research areas (e.g. biology of viruses in sponges, effects of environmental stress) that we believe are deserving of increased attention.     

Delayed seed dispersal in Pinus torreyana (Torrey pine)

Summary Torrey pine exhibits a pattern of seed release intermediate between an open and closed-cone species. It was found that the cones open at maturity, but that seed fall from some cones continues for up to 13 years. Approximately 77% of the total seed crop was present in age classes one or more years past the time of seed maturity.Serotiny is thought to evolve in response to fire, and partial serotiny at the population level has been attributed to circumstances in which the strong selective pressure of fire is relaxed. We hypothesize that delayed seed dispersal in Torrey pine is a stable trait which is the result of a pattern of large relatively rare crown fires separated by intervals longer than one generation. The reduced serotiny observed in other conifers on headlands and islands in California seems consistent with our hypothesis.     

Integrating methods that investigate how complementarity influences ecosystem functioning

Separating the mechanisms that influence ecosystem functioning has been a goal of recent high profile experiments. Integrating the various experimental and analytical methods that attempt this goal across terrestrial and aquatic ecosystems, as well as careful definition of 'complementarity', produces novel insights and valuable lessons about new directions for research. (1) Experimental designs differ in temporal scale and whether standing stock or another ecosystem process was the response variable. (2) Mathematically identical variables in different designs have contrasting ecological interpretations. For example, different sets of ecological processes can contribute to different variables in different experimental designs. (3) The frequency of transgressive overyielding of standing stock (e.g. total above ground biomass) in polycultures implies little about the prevalence of transgressive overyielding in other ecosystem processes. (4) Measuring the contribution to ecosystem functioning of individual species, rather than just total ecosystem functioning of a polyculture, is not essential for estimating effects of complementarity. (5) Further research will profit from distinguishing standing stock from all other ecosystem functions. (6) None of the analytic methods can distinguish the effects of individual processes or mechanisms such as resource use differentiation, facilitation, or allelopathy, for which additional experimental treatments are required.     

植物化感作用研究中应注意的问题

近年植物化感作用的研究十分活跃,但研究中也存在着一些问题和误区．本文就化感作用的基本定义和研究内容;化感物质的释放途径和研究方法;化感作用与植物竞争和环境胁迫;化感作用的应用潜力等几个主要方面存在的一些易混淆的问题进行讨论,并提出一些看法．     

A longing for the natural past: unexplored benefits and impacts of a nostalgic approach toward restoration in ecology

Nostalgia has endured a negative societal perception since its inception, which influences how it is deployed in ecological restoration. However, the emotion has undergone a paradigmatic shift over the past 15 years with new quantitative psychological research providing insight into complex and oftentimes positive effects. In particular, personal nostalgia can increase social connectedness, optimism, self‐esteem, inspiration, openness, creativity, and charitable giving. Here, we view ecological nostalgia, which we define as a desire to return a degraded ecosystem to a past state that complements bittersweet memories of a better ecological period, as an accompanying motivator for applied ecological restoration. However, some restoration ecology circles presently reject the connection with nostalgia, which excludes potential benefits for restoration practices. We provide a survey of recent psychological nostalgia research to critique and reevaluate the stigma surrounding nostalgia in restoration. By doing so, we are optimistic that more informed views of nostalgia will be adopted by the restoration community to cautiously embrace a connection that can help motivate ecological restoration activities.     

植物化感物质及化感潜力与土壤养分的相互影响

植物化感作用与许多生态因子有关.土壤养分缺乏,影响着许多植物化感物质的产生,从而影响植物的化感潜力;反过来,植物化感物质也通过络合、吸附、酸溶解、竞争、抑制等方式影响土壤的养分形态和水平.本文总结了植物化感物质及化感潜力与土壤养分的相互影响,并提出了今后该领域值得进一步研究的问题.包括以下几方面：加强植物化感研究与土壤 植物营养学研究的结合,以更深入地阐明植物化感物质、化感作用与土壤养分变化的关系;加强植物化感研究与生态系统养分循环研究的结合,以类似自然（nature-like）的方式模拟自然界植物所受的养分干,使养分干扰的化感研究结果更加逼真、可靠;加强对养分过量及受污染时植物化感作用的研究,为揭示农业和林业生产中植物的相互作用机制和生物量变化机制提供新的思路,为生态保护提供科学依据.