Predicting ecosystem dynamics at regional scales: an evaluation of a terrestrial biosphere model for the forests of northeastern North America

Terrestrial biosphere models are important tools for diagnosing both the current state of the terrestrial carbon cycle and forecasting terrestrial ecosystem responses to global change. While there are a number of ongoing assessments of the short-term predictive capabilities of terrestrial biosphere models using flux-tower measurements, to date there have been relatively few assessments of their ability to predict longer term, decadal-scale biomass dynamics. Here, we present the results of a regional-scale evaluation of the Ecosystem Demography version 2 (ED2)-structured terrestrial biosphere model, evaluating the model's predictions against forest inventory measurements for the northeast USA and Quebec from 1985 to 1995. Simulations were conducted using a default parametrization, which used parameter values from the literature, and a constrained model parametrization, which had been developed by constraining the model's predictions against 2 years of measurements from a single site, Harvard Forest (42.5° N, 72.1° W). The analysis shows that the constrained model parametrization offered marked improvements over the default model formulation, capturing large-scale variation in patterns of biomass dynamics despite marked differences in climate forcing, land-use history and species-composition across the region. These results imply that data-constrained parametrizations of structured biosphere models such as ED2 can be successfully used for regional-scale ecosystem prediction and forecasting. We also assess the model's ability to capture sub-grid scale heterogeneity in the dynamics of biomass growth and mortality of different sizes and types of trees, and then discuss the implications of these analyses for further reducing the remaining biases in the model's predictions.     

Testing the effects of diversity on ecosystem multifunctionality using a multivariate model

Most ecosystems provide multiple services, thus the impact of biodiversity losses on ecosystem functions may be considerably underestimated by studies that only address single functions. We propose a multivariate modelling framework for quantifying the relationship between biodiversity and multiple ecosystem functions (multifunctionality). Our framework consolidates the strengths of previous approaches to analysing ecosystem multifunctionality and contributes several advances. It simultaneously assesses the drivers of multifunctionality, such as species relative abundances, richness, evenness and other manipulated treatments. It also tests the relative importance of these drivers across functions, incorporates correlations among functions and identifies conditions where all functions perform well and where trade‐offs occur among functions. We illustrate our framework using data from three ecosystem functions (sown biomass, weed suppression and nitrogen yield) in a four‐species grassland experiment. We found high variability in performance across the functions in monocultures, but as community diversity increased, performance increased and variability across functions decreased.     

Interaction strengths in balanced carbon cycles and the absence of a relation between ecosystem complexity and stability

The strength of interactions is crucial to the stability of ecological networks. However, the patterns of interaction strengths in mathematical models of ecosystems have not yet been based upon independent observations of balanced material fluxes. Here we analyse two Antarctic ecosystems for which the interaction strengths are obtained: (1) directly, from independently measured material fluxes, (2) for the complete ecosystem and (3) with a close match between species and ‘trophic groups’. We analyse the role of recycling, predation and competition and find that ecosystem stability can be estimated by the strengths of the shortest positive and negative predator‐prey feedbacks in the network. We show the generality of our explanation with another 21 observed food webs, comparing random‐type parameterisations of interaction strengths with empirical ones. Our results show how functional relationships dominate over average‐network topology. They make clear that the classic complexity‐instability paradox is essentially an artificial interaction‐strength result.     

区域生态系统健康动态评价——以毛集生态实验区为例

区域生态系统健康状况对区域可持续发展具有重要意义。基于"系统和谐"理念,构建区域生态系统健康评价体系,对毛集生态试验区生态系统及其4个子系统健康水平和演进趋势进行量化分析。结果表明:5年尺度上社会系统得分受人口健康水平及民众幸福感知强度制约而增幅不大;经济系统得分提高迅速,增幅达到149.5%,但负外部效应明显;自然系统健康水平先降低再增加,主要受湖泊生物多样性下降影响;风险系统得分先降低再增加,自然-经济-社会耦合系统发展失衡是导致风险水平激增的主要原因。区域生态系统健康各年评价结果均为亚健康隶属,正向隶属先增大后减小,环境负荷增大是造成区域生态系统弹性减弱,敏感性增强,发展活力降低的主要原因。     

Predicting the outcomes of a tri‐trophic interaction between an indigenous parasitoid and an exotic herbivorous pest and its host plants

Understanding the novel ecological interactions that result from biological invasions is a critical issue in modern ecology and evolution as well as pest management. Introduced herbivorous insects may interact with native plants and indigenous natural enemies, creating novel tri‐trophic interactions. To help predict the potential outcomes of novel interactions, we investigated the behavioural and physiological responses of an indigenous generalist parasitoid (Habrobracon gelechiae) to an introduced generalist herbivore (the light brown apple moth, Epiphyas postvittana) and its new host plants in California. We first examined the parasitoid's host location and acceptance on a range of nine common host plants of the moth representing distinctly different geographic origins and morphologies (to examine the effect of a known toxic plant on the parasitoid's performance, an additional toxic plant species was also tested that the moth consumes in the laboratory but does not naturally attack). The parasitoid was able to locate the host larvae on all plants equally well, although clutch size was affected by host plant. We then determined fitness of the moth and the parasitoid on four representative plants. The moth larvae suffered higher mortality and a slower developmental rate on the known toxic plant than on the other three plants, but the parasitoid's fitness correlates did not differ between the host food plants. These results show a high level of plasticity in the indigenous generalist parasitoid in its ability to exploit the exotic host on a wide range of host plants, generating an invasion‐driven novel tri‐trophic interaction.     

Trophic modelling of a New Zealand rocky reef ecosystem using simultaneous adjustment of diet, biomass and energetic parameters

We present a balanced model of organic carbon flows through a temperate coastal ecosystem in New Zealand. The Te Tapuwae o Rongokako Marine Reserve is a 2452 ha no-take area including both rocky reef platforms and soft sediment, and covering the intertidal and subtidal communities to depths of approximately 50 m. The model includes 22 trophic groups, including birds, predatory and grazing invertebrates, detritivores, five groups of fish, microphytes, macroalgae, zooplankton, phytoplankton, bacteria and detritus. Initial parameterisations of the model were developed from video, diver and quadrat surveys in the study area, augmented by parameters derived from simple population models and scientific literature. A novel two stage balancing methodology is presented which adjusts biomasses, diet fractions, and energetic parameters of all trophic groups simultaneously, taking into account estimated parameter uncertainties and the highly variable magnitudes of flows through different groups (6 orders of magnitude). Most adjustments to the initial parameters necessary to balance the trophic model were < 20%, but large adjustments were needed for poorly observed groups such as bacteria, sponge, and phytoplankton. The balanced model is recognised as being one solution amongst many. In the model, 94% of the primary production remained ungrazed and formed particulate and dissolved organic detritus. The balanced model indicated that the reserve is relatively impoverished in terms of grazers and predators relative to New Zealand rocky reefs to the north. The model suggests that lobsters, which have increased in numbers since the reserve was established, are responsible for substantial predation on invertebrate groups which make up their prey (grazing, predatory, phytal/infaunal invertebrates). The level of predation on invertebrates by lobster in the model depends significantly on the extent to which lobsters in TTMR are consuming macroalgae.     

A prospective model for the phenology of Microctonus hyperodae (Hymenoptera: Braconidae), a potential biological control agent of argentine stem weevil in New Zealand

A predictive phenological model is described for the parasitoid Microctonus hyperodae, introduced to New Zealand as a potential biological control agent against Argentine stem weevil Listronotus bonariensis. The model is based on development/temperature relationships obtained from experiments on the parasitoid in quarantine prior to its release, allowing early predictions of its phenology in different parts of the target pest's New Zealand range. In particular the model was used to predict the number of parasitoid generations each year, the degree of temporal synchrony between parasitoid adults and the susceptible adult pest stage, the order of parasitism and reproduction in the pest's life cycle as a possible basis for a simplified, discrete host/parasitoid population model, and the likely significance of ecotypic differences in development and diapause characteristics of the parasitoid. These applications demonstrate the potential for simple models to help in climate matching of classical biological control agents and estimation of their interaction with pest dynamics, using data obtainable prior to their introduction and release. In addition the model proved useful as a decision aid during the release programme, by indicating the likely effects of unusual weather and the need or otherwise for further parasitoid releases.     

The re-emergence of the bed bug as a nuisance pest: implications of resistance to the pyrethroid insecticides

A global resurgence of bed bugs (Hemiptera: Cimicidae) has led to renewed scientific interest in these insects. The current bed bug upsurge appears to have started almost synchronously in the late 1990 s in Europe, the U.S.A. and Australia. Several factors have led to this situation, with resistance to applied insecticides making a significant contribution. With a growing number of insecticides (DDT, carbamates, organophosphates etc.) being no longer available as a result of regulatory restrictions, the mainstay chemistry used for bed bug control over the past few decades has been the pyrethroid insecticides. With reports of increasing tolerance to pyrethroids leading to control failures on the rise, containing and eradicating bed bugs is proving to be a difficult task. Consequently, several recent studies have focused on determining the mode of action of pyrethroid resistance in bed bug populations sourced from different locations. Correct identification of the factor(s) responsible for the increasing resistance is critical to the development of effective management strategies, which need to be based, wherever possible, on firm scientific evidence. Here we review the literature on this topic, highlighting the mechanisms thought to be involved and the problems currently faced by pest control professionals in dealing with a developing pandemic.     

Salt to conserve: a review on the ecology and preservation of hypersaline ecosystems

When it comes to the investigation of key ecosystems in the world, we often omit salt from the ecological recipe. In fact, despite occupying almost half of the volume of inland waters and providing crucial services to humanity and nature, inland saline ecosystems are often overlooked in discussions regarding the preservation of global aquatic resources of our planet. As a result, our knowledge of the biological and geochemical dynamics shaping these environments remains incomplete and we are hesitant in framing effective protective strategies against the increasing natural and anthropogenic threats faced by such habitats. Hypersaline lakes, water bodies where the concentration of salt exceeds 35 g/l, occur mainly in arid and semiarid areas resulting from hydrological imbalances triggering the accumulation of salts over time. Often considered the ‘exotic siblings’ within the family of inland waters, these ecosystems host some of the most extremophile communities worldwide and provide essential habitats for waterbirds and many other organisms in already water-stressed regions. These systems are often highlighted as natural laboratories, ideal for addressing central ecological questions due to their relatively low complexity and simple food web structures. However, recent studies on the biogeochemical mechanisms framing hypersaline communities have challenged this archetype, arguing that newly discovered highly diverse communities are characterised by specific trophic interactions shaped by high levels of specialisation. The main goal of this review is to explore our current understanding of the ecological dynamics of hypersaline ecosystems by addressing four main research questions: (i) why are hypersaline lakes unique from a biological and geochemical perspective; (ii) which biota inhabit these ecosystems and how have they adapted to the high salt conditions; (iii) how do we protect biodiversity from increasing natural and anthropogenic threats; and (iv) which scientific tools will help us preserve hypersaline ecosystems in the future? First, we focus on the ecological characterisation of hypersaline ecosystems, illustrate hydrogeochemical dynamics regulating such environments, and outline key ecoregions supporting hypersaline systems across the globe. Second, we depict the diversity and functional aspects of key taxa found in hypersaline lakes, from microorganisms to plants, invertebrates, waterbirds and upper trophic levels. Next, we describe ecosystem services and discuss possible conservation guidelines. Finally, we outline how cutting-edge technologies can provide new insights into the study of hypersaline ecology. Overall, this review sheds further light onto these understudied ecosystems, largely unrecognised as important sources of unique biological and functional diversity. We provide perspectives for key future research avenues, and advocate that the conservation of hypersaline lakes should not be taken with ‘a grain of salt’.     

基于生态系统管理理论的海域集约利用评价——以河北沿海地级市为例

基于生态系统管理理论,从海洋投入强度、海洋利用强度、海洋经济效益及海洋生态环境质量层面,构建海域集约利用评价的指标体系,运用模糊决策分析理论计算各指标权重,得到河北省沿海地级市2005—2014年的海域集约利用综合指数,并利用聚类分析法及协调度指数对河北省海域集约利用的区域差异特征进行了分析。研究结果表明:2005—2014年河北省海域集约利用综合水平不断提高,除海洋生态环境质量准则层指数呈下降趋势外,海洋投入强度、海洋利用强度、海洋经济效益3个层面指数均呈上升趋势,其中持续增加趋势最明显的是海洋经济效益准则层;河北省沿海三市海域集约利用综合指数及各准则层指数的时序变化特征基本一致,但各区域之间仍体现着不同的变化特点,沧州市海域集约利用程度较高,唐山市海域集约利用经历了由低到高的过程,秦皇岛市海域集约利用的状况整体处于一般水平;河北省及沿海三市海域集约利用总体保持了较高的协调度,但各地区不同时段的变化特征有所不同。     

A spatial model of the development of pest resistance to a transgenic insecticidal crop: European corn borer on Bt maize

A mathematical model was constructed to describe the evolution of resistance to the Bacillus thuringiensis toxin (Bt) in an insect pest (European corn borer) population on a transgenic crop (Bt corn). The model comprises a set of partial differential equations of the reaction-diffusion type; local interactions of three competing pest genotypes formed by alleles of Bt resistance and susceptibility are described as in the Kostitzin model, and the spread of insects is modeled as diffusion. The model was used to evaluate the influence of pest characteristics on the efficacy of the high-dose/refuge strategy aiming to prevent or delay the spread of Bt resistance in pest populations. It was shown, by contrast, that a model based on Fisher-Haldane-Wright equations and formally incorporating a diffusion term cannot adequately describe the evolution of Bt resistance in a spatially inhomogeneous pest population. Further development of the proposed demo-genetic model is discussed.     

Using a climatic niche model to predict the direct and indirect impacts of climate change on the distribution of Douglas‐fir in New Zealand

Climate change is likely to have major impacts on the distribution of planted and natural forests. Herein, we demonstrate how a process‐based niche model (CLIMEX) can be extended to globally project the potential habitat suitable for Douglas‐fir. Within this distribution, we use CLIMEX to predict abundance of the pathogen P haeocryptopus gaeumannii and severity of its associated foliage disease, Swiss needle cast. The distribution and severity of the disease, which can strongly reduce growth rate of Douglas‐fir, is closely correlated with seasonal temperatures and precipitation. This model is used to project how climate change during the 2080s may alter the area suitable for Douglas‐fir plantations within New Zealand. The climate change scenarios used indicate that the land area suitable for Douglas‐fir production in the North Island will be reduced markedly from near 100% under current climate to 36–64% of the total land area by 2080s. Within areas shown to be suitable for the host in the North Island, four of the six climate change scenarios predict substantial increases in disease severity that will make these regions at best marginal for Douglas‐fir by the 2080s. In contrast, most regions in the South Island are projected to sustain relatively low levels of disease, and remain suitable for Douglas‐fir under climate change over the course of this century.     

Indicators quantifying small pelagic fish interactions: application using a trophic model of the southern Benguela ecosystem

Three indicators quantifying interactions between species are developed for an upwelling system to provide useful measures for the comparison of marine ecosystem structure and function. Small pelagic fish are dominant in upwelling systems, and by definition, they are pivotal in a wasp-waist upwelling system. The indicator of interaction strength (IS) quantifies the effect that a change in biomass of one group has on abundance of other groups. The functional impact (FI) indicator quantifies the trophic impacts of species on their own and other functional groups or feeding guilds. The trophic replacement (TR) indicator quantifies the trophic similarity between a species that is removed from an ecosystem and other species in that ecosystem, i.e. it quantifies the ability of one group to trophically replace another. A trophic model of the southern Benguela ecosystem is used as an example for the application of the indicators. The strong similarities in trophic functioning of the southern Benguela ecosystem in the anchovy-dominated system of the 1980s, and the 1990s when there was a shift towards greater sardine abundance, are explained by the mutual trophic replacement abilities of anchovy and sardine. Differences between the proposed indicators and mixed trophic impact assessment are highlighted, mainly resulting from the static versus dynamic nature of the models upon which they are based. Trophic indicators such as those presented here, together with other kinds of ecosystem indicators, may assist in defining operational frameworks for ecosystem-based fisheries management.     

The importance of climate and soils for estimates of net primary production: a sensitivity analysis with the terrestrial ecosystem model

We used the Terrestrial Ecosystem Model (TEM) to investigate how alternative input data sets of climate (temperature/precipitation), solar radiation, and soil texture affect estimates of net primary productivity (NPP) for the conterminous United States. At the continental resolution, the climates of Cramer and Leemans (C&L) and of the Vegetation/ Ecosystem Modelling and Analysis Project (VEMAP) represent cooler and drier conditions for the United States in comparison to the Legates and Willmott (L&W) climate, and cause 5.2% and 2.3% lower estimates of NPP. Solar radiation derived from C&L and given in VEMAP is 32% and 60% higher than the solar radiation data derived from Hahn cloudiness. These differences cause ～ 8% and 10% lower NPP because of radiation-induced water stress. In comparison to the FAO/CSRC soil texture, which represents most biomes with loam soils, the soil textures are finer (more silt and clay) in the Zobler and VEMAP data sets. The use of VEMAP soil textures instead of FAO/CSRC soil textures causes ～ 3% higher NPP because enhanced volumetric soil moisture causes higher rates of nitrogen cycling, but use of the Zobler soil textures has little effect. In general, NPP estimates of TEM are more sensitive to alternative data sets at the biome and grid cell resolutions than at the continental resolution. At all spatial resolutions, the sensitivity of NPP estimates represents the impact of uncertainty among the alternative data sets we used in this study. The reduction of uncertainty in input data sets is required to improve the spatial resolution of NPP estimates by process-based ecosystem models, and is especially important for improving assessments of the regional impacts of global change.     

A macro-scale perspective on within-farm management: how climate and topography alter the effect of farming practices

Organic farming has the potential to reverse biodiversity loss in farmland and benefit agriculture by enhancing ecosystem services. Although the mixed success of organic farming in enhancing biodiversity has been attributed to differences in taxa and landscape context, no studies have focused on the effect of macro-scale factors such as climate and topography. This study provides the first assessment of the impact of macro-scale factors on the effectiveness of within-farm management on biodiversity, using spiders in Japan as an example. A multilevel modelling approach revealed that reducing pesticide applications increases spider abundance, particularly in areas with high precipitation, which were also associated with high potential spider abundance. Using the model we identified areas throughout Japan that can potentially benefit from organic farming. The alteration of local habitat-abundance relations by macro-scale factors could explain the reported low spatial generality in the effects of organic farming and patterns of habitat association.     

不同视角下基于InVEST模型的流域生态补偿标准核算——以渭河甘肃段为例

补偿标准是生态补偿项目研究的核心内容。为提高补偿标准的可操作性,以渭河干流甘肃段为研究区,基于流域生态补偿标准范围界定,在考虑耕地向多种林地转化情况下采用In VEST模型和加权法核算流域新增生态服务量,并以新增生态服务价值为补偿上限,农户机会成本为补偿下限,先从国家新一轮退耕还林政策导向视角,探讨15°—25°和25°以上坡耕地退耕还林的差异化补偿标准。再从利益公平分配视角,耦合机会成本投入与生态系统服务产出,探讨生态补偿净收益不同地区的差异化补偿标准。结果表明:(1)渭河干流甘肃段退耕还林,生态补偿标准范围为146.39—481.98万元km~(-2)a~(-1)。(2)重要水源地一级保护区和保留区迎水面15°—25°坡耕地全部退耕还林需补偿金额13.95—33.55亿元。25°以上坡耕地全部退耕还林需要补偿金额12.96—28.35亿元。(3)各县/区比较,退耕还林净收益麦积区最大,陇西县最小。其生态补偿范围分别为202.23—727.92、96.99—136.53万元km~(-2)a~(-1)。