Spatial-typological differentiation of ecosystems of the west siberian plain. Communication IV: Terrestrial vertebrates

Differentiation of the vertebrate communities almost coincides with the differentiation of ecosystems in vegetation at the type level, as judged by formalized classifications of various blocks of ecosystems of West Siberia by geobotanical map units, and it differs significantly from that in the underground component due to the greater effect of waterlogging on the latter. In invertebrate communities, significant differences are observed in the boreal-subboreal part, where waterlogging is more significant and greater similarity is found among middle and southern-taiga communities than among subtaiga-steppe ones. Over the groups of map units, the heterogeneity of the vertebrate communities differs from that in all the examined blocks of ecosystems in greater differentiation in the tundra zone. In the pretundra northern taiga subzones and from the middle taiga to the steppe zone, the heterogeneity of vertebrate communities is somewhat lower than that of vegetation, and especially in the underground block of ecosystems. However, these differences relate only to the hierarchy of the division, and often occur at the level of taxa of the rank of subtype or class. All these data indicate the relative independence of changes in the distinguished blocks of ecosystems, which gives rise to noncoincidence of the boundaries and sizes of taxa within them, as well as the continuality of the ecosystems as a whole. A significant difference is observed between the traditional geobotanical and typological-chorological zones of terrestrial vertebrate communities.     

The stability of ecosystems

Stability criteria and phase boundaries for complex ecosystems are obtained and contrasted with previously studied scenarios. The stability of such systems is determined by the behaviour of the largest eigenvalue of matrices governing the response of the system to small perturbations. As a result we show that ecosystems with unstructured cooperative interactions between arbitary species can be less stable than had been previously determined. We also examine hierarchical ecologies, and demonstrate their increased stability under certain conditions.     

Cyanobacteria in mangrove ecosystems

Mangroves are subject to the effects of tides and fluctuations in environmental conditions, which may reach extreme conditions. These ecosystems are severely threatened by human activities despite their ecological importance. Although mangroves are characterized by a highly specialized but low plant diversity in comparison to most other tropical ecosystems, they support a diverse microbial community. Adapted microorganisms in soil, water, and on plant surfaces perform fundamental roles in nutrient cycling, especially nitrogen and phosphorus. Cyanobacteria contribute to carbon and nitrogen fixation and their cells act as phosphorus storages in ecosystems with extreme or oligotrophic environmental conditions such as those found in mangroves. As the high plant productivity in mangroves is only possible due to interactions with microorganisms, cyanobacteria may contribute to these ecosystems by providing fixed nitrogen, carbon, and herbivory-defense molecules, xenobiotic biosorption and bioremediation, and secreting plant growth-promoting substances. In addition to water, cyanobacterial colonies have been detected on sediments, rocks, decaying wood, underground and aerial roots, trunks, and leaves. Some mangrove cyanobacteria were also found in association to algae or seagrasses. Few studies on mangrove cyanobacteria are available, but together they have reported a substantial number of species in these ecosystems. However, the cyanobacterial diversity in this biome has been traditionally underestimated. Though mangrove communities generally host cyanobacterial taxa commonly found in marine environments, unique microhabitats found in mangroves potentially harbor several undescribed cyanobacterial taxa. The relevance of cyanobacteria for mangrove conservation is highlighted in their use for the recovery of degraded mangroves as biostimulants or in bioremediation.     

Resource subsidies between stream and terrestrial ecosystems under global change

Streams and adjacent terrestrial ecosystems are characterized by permeable boundaries that are crossed by resource subsidies. Although the importance of these subsidies for riverine ecosystems is increasingly recognized, little is known about how they may be influenced by global environmental change. Drawing from available evidence, in this review we propose a conceptual framework to evaluate the effects of global change on the quality and spatiotemporal dynamics of stream–terrestrial subsidies. We illustrate how changes to hydrological and temperature regimes, atmospheric CO₂ concentration, land use and the distribution of nonindigenous species can influence subsidy fluxes by affecting the biology and ecology of donor and recipient systems and the physical characteristics of stream–riparian boundaries. Climate‐driven changes in the physiology and phenology of organisms with complex life cycles will influence their development time, body size and emergence patterns, with consequences for adjacent terrestrial consumers. Also, novel species interactions can modify subsidy dynamics via complex bottom‐up and top‐down effects. Given the seasonality and pulsed nature of subsidies, alterations of the temporal and spatial synchrony of resource availability to consumers across ecosystems are likely to result in ecological mismatches that can scale up from individual responses, to communities, to ecosystems. Similarly, altered hydrology, temperature, CO₂ concentration and land use will modify the recruitment and quality of riparian vegetation, the timing of leaf abscission and the establishment of invasive riparian species. Along with morphological changes to stream–terrestrial boundaries, these will alter the use and fluxes of allochthonous subsidies associated with stream ecosystems. Future research should aim to understand how subsidy dynamics will be affected by key drivers of global change, including agricultural intensification, increasing water use and biotic homogenization. Our conceptual framework based on the match–mismatch between donor and recipient organisms may facilitate understanding of the multiple effects of global change and aid in the development of future research questions.     

Spatial-typological differentiation of the ecosystems of the West Siberian Plain. Communication II: Underground phytomass,dead organic matter,and soil humus

Similarity was quantified for the ecosystems of the West Siberian Plain based on the masses of plant cover, dead organic matter, and underground organic matter (including soil humus) and the resultant matrix was subjected to cluster analysis. The results showed that the differentiation in the vegetation was nearly equally attributable to zonal gradients of thermal and moisture conditions (waterlogging), while the differentiation in the underground part of the ecosystems was predominantly under control of waterlogging. Intratypical differences in the underground part were due to zonal-subzonal heterogeneity in the gradients of thermal and moisture conditions, composition of vegetation, and flooding during snow-melt period. Such division did not entirely agree with subzonal division. The ecosystems were rather aggregated on the basis of the three abovementioned characteristics, with flooding and forest-forming species being the same.     

The mutual relationship between the monitoring and modelling of estuarine ecosystems

A general simulation model developed for the Ems estuary (a part of the Wadden Sea), to describe the main carbon flow through the foodweb, was applied for monitoring purposes. In this model, the estuary is divided into five compartments, in each of which a pelagic, an epibenthic and a benthic submodel operates. A transport model regulates the distribution of dissolved and particulate substances over the area. Two parameters that partly regulate the carbon flow are the concentrations of phosphate and of the particles (turbidity) in the water. From the sensitivity analyses for phosphate and turbidity it can be concluded that the relative effects of changes in turbidity and changes in the influx of phosphate from the rivers are large in the upper reaches and small in the lowest reaches of the estuary. This is due to the increasing influence of the coastal waters in the lower reaches. These results indicate that the reaches, which represent the beginning and the end of a gradient in the estuary, are also very suitable for monitoring the quality status of this estuary in terms of production and standing stock of groups of organisms. The need to use monitored data from the boundaries (sea and rivers) of those ecosystems as input in simulation models is discussed. Moreover, the possibilities of using simulation models to generate new ideas on the functioning of estuarine ecosystems under changing environmental conditions and to help administrators to decide on specific future management strategies are also discussed. Presented at the VI International Wadden Sea Symposium (Biologische Anstalt Helgoland, Wattenmeerstation Sylt, D-2282 List, FRG, 1–4 November 1988).     

Geophysiological modeling: new ideas on modeling the evolution of ecosystems.

Living organisms evolve within ecological associations (from ecosystems to the biosphere) that are constituted by a biological component and a physico-chemical component. It is generally supposed that interactions such as competition and predation between the biological components of ecosystems are the main cause for the observed organization of ecosystems. We believe that in the search for a more comprehensive theory of evolution a much greater attention should be paid to the ways in which living organisms interact with the physico-chemical environment. To test our ideas, we develop a mathematical model to study the evolution of ecosystems, and we apply it to the study of hydrothermal vents. The model proposed is still a qualitative model. It tries to study, in a first approximation, the behaviours of the biological and chemical components. In the following we hope to develop and to improve it so to give a more realistic model.     

Distribution of Plesiomonas shigelloides in various components of pond ecosystems in Dhaka, Bangladesh.

Plesiomonas shigelloides is considered to be a waterborne agent of human gastroenteritis. An ecological study was carried out in five ponds in Dhaka city over a period of one year to elucidate the distribution and seasonality of this organism in various components of pond ecosystems. Samples were collected from hydrophytes, water, phytoplankton and sediment every 15 days over 12 months and cultured for P. shigelloides. P. shigelloides was isolated from a total of 120 samples including 25 (20.8%), 16 (13.3%), 22 (18.3%) and 35 (29.2%) of hydrophytes, water, phytoplankton and sediment samples, respectively. Distinct seasonal patterns of isolation of P. shigelloides were observed in the four components with two distinct peaks. The highest peaks were observed in hydrophytes and water samples in May and in phytoplankton and sediment in November. P. shigelloides was isolated from all components from all ponds during the study period. These results suggest that P. shigelloides is an autochthonous member in the freshwater pond ecosystems in Dhaka, Bangladesh.     

Biomass and nutrient distribution in two eucalypt forest ecosystems

The distribution of biomass and nutrients (N, P, K, Na, Mg, and Ca) among components of a Eucalyptus regnans forest and a mixed Eucalyptus obliqua-Eucalyptus dives forest near Melbourne in southern Victoria have been determined and are discussed. Both forests were found to have relatively low root biomass. Trees and soil accounted for more than 80% of each nutrient present in both ecosystems. The results of nutrient distribution studies in Australian eucalypt forests and in temperate forests elsewhere in the world are compared. These comparisons suggest that the above-ground living biomass in eucalypt forests contains no abnormally high or low quantities of macronutrients in relation to coniferous or deciduous hardwood forests. Detailed comparison among ecosystems is rendered difficult by the variable treatment given to roots and soils.     

退化森林生态系统评价指标体系研究进展

森林是陆地生态系统的主要组成部分,而森林退化是全球面临的主要环境问题之一,准确评价退化森林生态系统是进行森林生态系统恢复与重建的重要前提,建立合理的评价指标体系目前已成为生态学研究的热点问题。在研究国内外提出的关于退化森林生态系统评价理论的基础上,综述了森林退化的定义、特征和一般过程,梳理了退化森林生态系统评价指标筛选的一般原则和指标体系构建的主要方法,分析比较了不同学者所提出的主要评价指标。并在此基础上,重新筛选、构建了一套退化森林生态系统评价指标体系,即从生态系统的组成结构、功能和生境这3个方面选取了32个能够较全面反映退化生态系统主要特征的评价指标,以期为构建我国区域尺度上的退化森林生态系统评价指标体系提供参考,为退化森林生态系统的恢复和重建提供科学依据。总结分析了退化森林生态系统评价指标体系在构建过程中产生的一些问题和不足,提出了今后开展研究和探索应该深入的方向,以提高评价指标体系的科学性、准确性和合理性。     

Spatial patterns and dynamic responses of arctic food webs corroborate the exploitation ecosystems hypothesis (EEH)

According to the exploitation ecosystems hypothesis (EEH), productive terrestrial ecosystems are characterized by community-level trophic cascades, whereas unproductive ecosystems harbor food-limited grazers, which regulate community-level plant biomass. We tested this hypothesis along arctic-alpine productivity gradients at the Joatka field base, Finnmark, Norway. In unproductive habitats, mammalian predators were absent and plant biomass was constant, whereas herbivore biomass varied, reflecting the productivity of the habitat. In productive habitats, predatory mammals were persistently present and plant biomass varied in space, but herbivore biomass did not. Plant biomass of productive tundra scrublands declined by 40% when vegetation blocks were transferred to predation-free islands. Corresponding transfer to herbivore-free islands triggered an increase in plant biomass. Fertilization of an unproductive tundra heath resulted in a fourfold increase in rodent density and a corresponding increase in winter grazing activity, whereas the total aboveground plant biomass remained unchanged. These results corroborate the predictions of the EEH, implying that the endotherm community and the vegetation of the North European tundra behaves dynamically as if each trophic level consisted of a single population, in spite of local co-occurrence of >20 plant species representing different major taxonomic groups, growth forms, and defensive strategies.     

火干扰对森林生态系统土壤呼吸组分的影响研究进展

土壤呼吸是陆地生态系统与大气碳交换的主要方式,主要分为自养呼吸和异养呼吸。土壤呼吸不仅是森林生态系统碳循环过程的关键环节,也是森林生态系统能量流动和物质循环的重要生态过程。火作为森林生态系统中一个重要的生态因子,可以在短时间内对土壤呼吸组分造成巨大的影响。火干扰对土壤呼吸组分的影响与火烧强度、火烧频率、火烧持续时间以及火后恢复等因子有关,通过影响植被的根系与组成、微生物群落数量与结构,凋落物的数量以及生态系统的环境和小气候等,进而对土壤呼吸产生影响。火干扰对土壤呼吸影响整体表现为火烧后土壤呼吸速率下降,在几个月至几年内恢复到火烧前水平,之后火继续对土壤呼吸产生影响长达数年至数十年。通过描述火烧强度、火烧频率以及火后恢复时间,阐述火干扰对土壤呼吸组分的直接影响,以及通过火后环境对土壤呼吸组分产生的间接影响,来揭示火干扰对森林生态系统土壤呼吸组分的影响。同时针对火干扰对土壤呼吸组分的影响进行以下3个方面的研究展望：（1）火后产生的黑碳对土壤呼吸组分的影响;（2）火后植被恢复对土壤呼吸组分产生的影响;（3）火后土壤呼吸组分的长期变化规律。     

Novel and designed ecosystems

Growing attention to novel and designed ecosystems, and the confusion that follows from the overlap of these distinct ecosystem approaches, risks a loss of focus on ecological values at the core of restoration ecology. Novel ecosystems originate in ecosystems that are transformed beyond which the practical efforts of conventional restoration are feasible. They are also self‐sustaining in the sense that they take time to form, and do not typically receive regular management. In this respect, they arise differently than designed ecosystems, which are assembled with specific goals in mind and are often heavily managed. Designed (or engineered) ecosystems comprise a variety of ecological approaches including reclamation (return a degraded ecosystem to productive capacity), green infrastructure, and agroecological systems. There are three elements that distinguish novel and designed ecosystems. Designed ecosystems typically require intensive intervention to create them, and ongoing management to sustain them; novel ecosystems do not. Second, the human intentions behind designed and novel ecosystems are usually different. Designed ecosystems exist in the service of human interests, including specific services (e.g. filtration, cooling, nature appreciation), aesthetics, and shifting value commitments toward green infrastructure; novel ecosystems arise typically through inadvertent human activity. Third, designed and novel ecosystems have different developmental pathways. Historical ecosystems are the starting point for restored, hybrid, and novel ecosystems; designed ecosystems are intentionally created. Designed ecosystems stand apart as providing a new origin for ecosystems of the future, including those that become novel ecosystems.     

Biological equilibrium in ecosystems 2. Parameters of ecosystems

In this paper the Theory of Biological Equilibrium (TBE), as the theoretical basis of the Canonical Hypothesis, is used to compute a set of theoretical parameters of natural ecosystems. These parameters are the individuals: species (I/S); the commonness: rarity (C/U) ration as well as the expected density (d _e) and total area (TA) of ecosystems. Results of sampling with nested quadrates are checked against theoretical values. Deviations from expected values of 5 to 10% occur in samples with Natural Biological Equilibrium (NBE); in disturbed and transitional sites a compensation mechanism is found which results in simulated NBE.     

Invertebrates and the complexity of tropical ecosystems

It has been estimated that there are seven million terrestrial arthropod species on Earth consisting of 6.1 million species of insects, 1.5 million of which are beetles. Tropical forests hold a majority of these species, yet few such places have been adequately sampled for alpha diversity, and there remains even more uncertainty about beta diversity. From an ecological point of view, it is the functional role of organisms within ecosystems that is the particular focus. It has been customary to classify invertebrates within ecosystems in terms of their trophic roles, but it is also useful to consider their roles in networks. In broad terms, we can classify these networks on the grounds of their basal resources. Those based directly on the photosynthetic products of plants are so-called “green” food webs, and those based on dead and dying plant material are “brown” food webs. Here, we principally discuss the diversity and functional roles of the invertebrates in tropical terrestrial ecosystems. New sampling and analytical techniques, an expanded set of focal taxa, and an enhanced concern with interactions and processes hold the promise of a productive future for invertebrate studies in the tropics. These will not only add to general understanding of the dynamics of tropical ecosystems but will also provide powerful tools for monitoring and responding to environmental change.     

Spatial flows and the regulation of ecosystems

Spatial flows of materials and organisms across ecosystem boundaries are ubiquitous. Understanding the consequences of these flows should be a basic goal of ecosystem science, and yet it has received scant theoretical treatment to date. Here, using a simple, open, nutrient-limited ecosystem model with trophic interactions, we explore theoretically how spatial flows affect the functioning of local ecosystems, how physical mass-balance constraints interact with biological demographic constraints in the regulation of this functioning, and how failure to consider these constraints explicitly can lead to models that are ecologically inconsistent. In particular, we show that standard prey-dependent models for trophic interactions may lead to implausible outcomes when embedded in an ecosystem context with appropriate mass flows and mass-balance constraints. Our analysis emphasizes the need for integration of population, community, and ecosystem perspectives in ecology and the critical consequences of assuming closed versus open systems.     

基于红外增温的草地生态系统响应全球变暖的研究进展

为了更好地了解全球变暖对草地生态系统的影响机制, 该文介绍了红外加热技术的原理、增温效应及其优缺点, 重点从植物物候、光合生理、生长发育、群落结构和功能、土壤特性, 特别是植物群落地下过程方面, 系统综述了基于红外加热技术模拟气候变暖对草地生态系统影响的最新研究进展, 在此基础上探讨了未来草地生态系统响应全球变暖研究拟重视的研究领域。     

Large‐scale degradation of Amazonian freshwater ecosystems

Hydrological connectivity regulates the structure and function of Amazonian freshwater ecosystems and the provisioning of services that sustain local populations. This connectivity is increasingly being disrupted by the construction of dams, mining, land‐cover changes, and global climate change. This review analyzes these drivers of degradation, evaluates their impacts on hydrological connectivity, and identifies policy deficiencies that hinder freshwater ecosystem protection. There are 154 large hydroelectric dams in operation today, and 21 dams under construction. The current trajectory of dam construction will leave only three free‐flowing tributaries in the next few decades if all 277 planned dams are completed. Land‐cover changes driven by mining, dam and road construction, agriculture and cattle ranching have already affected ~20% of the Basin and up to ~50% of riparian forests in some regions. Global climate change will likely exacerbate these impacts by creating warmer and dryer conditions, with less predictable rainfall and more extreme events (e.g., droughts and floods). The resulting hydrological alterations are rapidly degrading freshwater ecosystems, both independently and via complex feedbacks and synergistic interactions. The ecosystem impacts include biodiversity loss, warmer stream temperatures, stronger and more frequent floodplain fires, and changes to biogeochemical cycles, transport of organic and inorganic materials, and freshwater community structure and function. The impacts also include reductions in water quality, fish yields, and availability of water for navigation, power generation, and human use. This degradation of Amazonian freshwater ecosystems cannot be curbed presently because existing policies are inconsistent across the Basin, ignore cumulative effects, and overlook the hydrological connectivity of freshwater ecosystems. Maintaining the integrity of these freshwater ecosystems requires a basinwide research and policy framework to understand and manage hydrological connectivity across multiple spatial scales and jurisdictional boundaries.