Management of land/inland water ecotones: needs for regional approaches to achieve sustainable ecological systems

Evidence suggests that the boundaries between rivers, floodplain wetlands, and adjacent upland communities are among the most important components of landscapes. In a landscape context, floodplain wetlands and their ecotones are important transition zones between uplands and aquatic ecosystems. Management of wetland patches and ecotones to achieve sustainable ecosystems requires action on a broad scale, giving consideration to all factors affecting wetlands and the drainage basins of which they are a part. In northeastern United States, a struggle to identify new sources of water has focussed attention on the sustainability of aquatic ecosystems.     

The Role of Ecotones in Emerging Infectious Diseases

Recognition of the significance of the boundary between ecological systems, often referred to as the ecotone, has a long history in the ecological sciences and in zoonotic disease research. More recent research in landscape ecology has produced an expanded view of ecotones and elaboration of their characteristics and functions in ecosystems. Parallel research on emerging infectious diseases (EIDs) and the causes of increased rates of pathogen transmission, spread, and adaptation suggests a correspondence between ecotonal processes and the ecological and evolutionary processes responsible for zoonotic and vector-borne emerging infections. A review of the literature suggests that ecotones play a role in a number of the most important EIDs. Yet these are the only diseases for which specific landscape ecological information exists in the literature or disease reports. However, the similar disease ecologies of these with about half of the approximately 130 zoonotic EIDs suggests ecotones, particularly their anthropogenic origination or modification, may be generally associated with ecotones and the global trend of increasing EIDs.     

Linking microbial co‐occurrences to soil ecological processes across a woodland‐grassland ecotone

Ecotones between distinct ecosystems have been the focus of many studies as they offer valuable insights into key drivers of community structure and ecological processes that underpin function. While previous studies have examined a wide range of above‐ground parameters in ecotones, soil microbial communities have received little attention. Here we investigated spatial patterns, composition, and co‐occurrences of archaea, bacteria, and fungi, and their relationships with soil ecological processes across a woodland‐grassland ecotone. Geostatistical kriging and network analysis revealed that the community structure and spatial patterns of soil microbiota varied considerably between three habitat components across the ecotone. Woodland samples had significantly higher diversity of archaea while the grassland samples had significantly higher diversity of bacteria. Microbial co‐occurrences reflected differences in soil properties and ecological processes. While microbial networks were dominated by bacterial nodes, different ecological processes were linked to specific microbial guilds. For example, soil phosphorus and phosphatase activity formed the largest clusters in their respective networks, and two lignolytic enzymes formed joined clusters. Bacterial ammonia oxidizers were dominant over archaeal oxidizers and showed a significant association (p < 0.001) with potential nitrification (PNR), with the PNR subnetwork being dominated by Betaproteobacteria. The top ten keystone taxa comprised six bacterial and four fungal OTUs, with Random Forest Analysis revealing soil carbon and nitrogen as the determinants of the abundance of keystone taxa. Our results highlight the importance of assessing interkingdom associations in soil microbial networks. Overall, this study shows how ecotones can be used as a model to delineate microbial structural patterns and ecological processes across adjoining land‐uses within a landscape.     

内陆水—陆地交错带的生态功能及其保护与开发前

内陆水／陆地交错带是陆地和水生态系统的界面区。由于它在系统间的特殊地位,近年来受到国际上生态和环境学界的格外重视。水陆交错带的生态功能有保持生物物种的多样性、拦截和过滤经过此交错带的物质流、有利于鱼类的繁育、稳定毗邻的生态系统、净化水体、减少洪水危害、保持水土等。水陆交错带的保护和科学开发都有待提高,使之在人类和自然的协调发展中发挥更大的作用。     

Energy control of matter fluxes through land-water ecotones in an agricultural landscape

Ecotones play and important role in control of matter input into water bodies. The impacts of shelterbelt and meadow ecotones on ground water passage from cultivated fields to pond were studied. The reduction of water flux due to evapotranspiration by shelterbelts and meadows on slopes of different steepness were estimated. The horizontal passage of heat energy between cultivated fields and ecotones, which enhances evaporation in shelterbelts and meadows was demonstrated. The reduction of ground water flux by a ten meter wide shelterbelt or meadow surrounding a pond can reach as much as 100 per cent when the slope is about 1 degree, during a sunny day. Shelterbelts are a more effective measure for control of cycling matter than meadows. The greater the slope of the water table and the more intensive the radiation and advective processes, the more distinct the differences between shelterbelt and meadow impacts on groundwater flow are.     

Vital Landscape Attributes: Missing Tools for Restoration Ecology

Twenty-three “vital ecosystem attributes” (VEAs) were previously proposed to aid in quantitative evaluation of whole ecosystem structure, composition, and functional complexity over time. We here introduce a series of 16 quantifiable attributes for use at a higher spatial scale and ecological organizational level, the landscape. “Vital landscape attributes” (VLAs) should be useful in evaluating the results of ecological restoration or rehabilitation undertaken with a landscape perspective, provided that clear definitions and boundaries are agreed upon for the different spatial and ecological entities involved. Like VEAs, VLAs should be sensitive to changes wrought by human as well as to nonhuman factors leading to ruptures in flow processes or vegetation “switches.” They should be applicable over a wide range of landscape types and therefore aid in conducting rigorous interlandscape comparisons. We present three groups of VLAs: (1) landscape structure and biotic composition, (2) functional interactions among ecosystems within the landscape, and (3) degree, type, and causes of landscape fragmentation and degradation. Ecotones between ecosystems are touched upon by several different VLAs. Because conflicting terminology abounds in this area, we append a glossary defining the problematic terms used.     

Biotic fluxes of matter and energy between aquatic and terrestrial ecosystems

This paper is an introduction to a special issue of the journal. A brief historical delineation of the question of studying interfaces between adjacent ecosystems (ecotones) is presented. High biodiversity of ecotones and their vulnerability to natural and anthropogenic impacts, including invasions of alien species, are noted. It is supposed that there is no contradiction between the ecotone and river continuum concepts. The important ecological role of amphibiotic animals and plants in interactions and functioning of the adjacent ecosystems is emphasized. The issue of studying the quantitative parameters of fluxes of matter and energy between ecosystems in conjunction with their qualitative parameters (chemical elemental and biochemical compositions) is considered in the present paper.     

Riverine landscapes: taking landscape ecology into the water

1. Landscape ecology deals with the influence of spatial pattern on ecological processes. It considers the ecological consequences of where things are located in space, where they are relative to other things, and how these relationships and their consequences are contingent on the characteristics of the surrounding landscape mosaic at multiple scales in time and space. Traditionally, landscape ecologists have focused their attention on terrestrial ecosystems, and rivers and streams have been considered either as elements of landscape mosaics or as units that are linked to the terrestrial landscape by flows across boundaries or ecotones. Less often, the heterogeneity that exists within a river or stream has been viewed as a `riverscape' in its own right.
2. Landscape ecology can be unified about six central themes: (1) patches differ in quality (2) patch boundaries affect flows, (3) patch context matters, (4) connectivity is critical, (5) organisms are important, and (6) the importance of scale. Although riverine systems differ from terrestrial systems by virtue of the strong physical force of hydrology and the inherent connectivity provided by water flow, all of these themes apply equally to aquatic and terrestrial ecosystems, and to the linkages between the two.
3. Landscape ecology therefore has important insights to offer to the study of riverine ecosystems, but these systems may also provide excellent opportunities for developing and testing landscape ecological theory. The principles and approaches of landscape ecology should be extended to include freshwater systems; it is time to take the `land' out of landscape ecology.     

Estimating the ecotone width in patchy ecotones using a sigmoid wave approach

Ecotones are zones of transition between two adjacent ecological systems and are characterized by a high rate of change compared to these adjacent areas. They are dynamic entities with both a spatial and temporal property, reflected in an ecotone width and location, which vary across time during succession or environmental change on both a local or global scale. Various techniques have been proposed to characterize ecotones, one of them being a sigmoid wave curve fit on the transects across the ecotone. In this paper, we test the robustness of a sigmoid wave model approach on simulated ecotone data with a varying degree of steepness, patchiness and transect length. An analysis of variance (ANOVA) provided us details on the sensitivity of the estimated ecotone width for the steepness, the transect length as well as for the patchiness of the ecotone. The statistics also allowed us to investigate the interaction between the different parameters on the resulting ecotone width. We conclude that the sigmoid wave curve-fitting algorithm provides a robust way to describe ecotones with various degrees of steepness and patchiness. Depending on the transect window size used, a sigmoid wave curve-fitting algorithm will pick up variations in ecotone steepness or in ecotone steepness and patchiness.     

Rapid Turnover and Edge Effects in Dung Beetle Assemblages (Scarabaeidae) at a Bolivian Neotropical Forest-Savanna Ecotone1

Habitat fragmentation and the widespread creation of habitat edges have recently stimulated interest in assessing the effects of ecotones on biodiversity. Ecotones, natural or anthropogenic, can greatly affect faunal movement, population dynamics, species interactions, and community structure. Few data exist, however, on insect community response to forest–savanna ecotones, a natural analog to anthropogenically cleared areas adjacent to forest. In this study, the abundance, total biomass, average individual biomass, and distribution of scarabaeine dung beetles were examined at a sharp tropical evergreen forest–savanna ecotone in Santa Cruz, Bolivia. The abundance, total biomass, and average individual biomass of dung beetles varied significantly across the forest, edge, and savanna habitats. Species richness (S_obs) also varied significantly across the three habitats, but statistical estimations of true species richness (S_est) did not. Habitat specificity of the dung beetles in this study was extremely high. Of the 50 most common species collected during the study, only 2 species were collected in both the forest and savanna habitats, signaling nearly complete community turnover in just a few meters. Strong edge effects were evidenced by the decline in abundance, total biomass, and species richness at the forest‐savanna boundary.     

Litter decomposition promotes differential feedbacks in an oligotrophic southern Everglades wetland

The differential accumulation or loss of carbon and nutrients during decomposition can promote differentiation of wetland ecosystems, and contribute to landscape-scale heterogeneity. Tree islands are important ecosystems because they increase ecological heterogeneity in the Everglades landscape and in many tropical landscapes. Only slight differences in elevation due to peat accumulation allow the differentiation of these systems from the adjacent marsh. Hydrologic restoration of the Everglades landscape is currently underway, and increased nutrient supply that could occur with reintroduction of freshwater flow may alter these differentiation processes. In this study, we established a landscape-scale, ecosystem-level experiment to examine litter decomposition responses to increased freshwater flow in nine tree islands and adjacent marsh sites in the southern Everglades. We utilized a standard litterbag technique to quantify changes in mass loss, decay rates, and phosphorus (P), nitrogen (N) and carbon (C) dynamics of a common litter type, cocoplum (Chrysobalanus icaco L.) leaf litter over 64 weeks. Average C. icaco leaf degradation rates in tree islands were among the lowest reported for wetland ecosystems (0.23 ± 0.03 yr⁻¹). We found lower mass loss and decay rates but higher absolute mass C, N, and P in tree islands as compared to marsh ecosystems after 64 weeks. With increased freshwater flow, we found generally greater mass loss and significantly higher P concentrations in decomposing leaf litter of tree island and marsh sites. Overall, litter accumulated N and P when decomposing in tree islands, and released P when decomposing in the marsh. However, under conditions of increased freshwater flow, tree islands accumulated more P while the marsh accumulated P rather than mineralizing P. In tree islands, water level explained significant variation in P concentration and N:P molar ratio in leaf tissue. Absolute P mass increased strongly with total P load in tree islands (r ² = 0.81). In the marsh, we found strong, positive relationships with flow rate. Simultaneous C and P accumulation in tree island and mineralization in adjacent marsh ecosystems via leaf litter decomposition promotes landscape differentiation in this oligotrophic Everglades wetland. However, results of this study suggest that variation in flow rates, water levels and TP loads can shift differential P accumulation and loss leading to unidirectional processes among heterogeneous wetland ecosystems. Under sustained high P loading that could occur with increased freshwater flow, tree islands may shift to litter mineralization, further degrading landscape heterogeneity in this system, and signaling an altered ecosystem state.     

Nitrogen Enrichment Accelerates Mangrove Range Expansion in the Temperate–Tropical Ecotone

Ecosystems - Climate change and nutrient enrichment are two phenomena impacting coastal ecosystems. In coastal wetlands, mangroves in temperate–tropical ecotones are encroaching on adjacent...     

Evidence on ecotone concepts from switch,environmental and anthropogenic ecotones

Abstract. Four contrasting ecotones were sampled to address three questions: (1) Are there ‘ecotonal’ species, (2) Do ecotones possess higher (or lower) species richness than the adjacent communities? and (3) Are exotic species more likely to occur in ecotones? One ecotone was edaphic, one was apparently caused by a positive‐feedback switch, one was environmental/anthropogenic and one was entirely anthropogenic. The exact position of each ecotone was established from the spatial change in ordination scores. Ecotonal species, in the sense of species mainly restricted to the ecotone at the site, were present in all four ecotones. All but one of the ecotonal species were native. The switch ecotone and the purely anthropogenic ecotone also contained native species that were significantly more frequent in the ecotone than in either adjacent community. Species richness was intermediate between that of the two adjacent communities in three of the ecotones. In the environmental/anthropogenic ecotone, species richness was higher than in adjacent communities, but not significantly so. There were appreciable numbers of exotic species in the two ecotones with anthropogenic influence, one of which had a proportion of exotic species intermediate between the two adjacent communities. Contrary to theory, the proportion of exotic species in the second ecotone was significantly lower than in either adjacent community. We conclude that all three features we examined depend on the particular ecological conditions and the ecology of the species present; they are not intrinsic properties of ecotones.     

Effects of forest-dune ecotone management on the endangered heath grasshopper, Chorthippus vagans (Orthoptera: Acrididae)

Dry, oligotrophic ecosystems are highly threatened in Europe due to massive changes in land use and eutrophication. The conservation of these xeric habitats has received much attention, whereas the ecotones between xeric habitats and other habitat types are often disregarded. One species which mainly inhabits the transition zone between pine forests and adjacent xeric habitats is the heath grasshopper, Chorthippus vagans. This species is endangered in large parts of Europe. One of the largest populations in northern Germany is found on a degraded inland dune near Hanover. This population is threatened by dense growth of deciduous trees and litter accumulation. We analyzed changes in the distribution of this population after the implementation of conservation measures (thinning out the forest and removal of leaf litter). Moreover, we examined dispersal distances of the species in order to assess its colonization potential. We also studied the microhabitat preferences of C. vagans to assess key factors influencing its local distribution. Our data show a substantial growth in population size, which might be a consequence of the conservation measures. New patches on the dune were colonized, promoting dispersal between the subpopulations. We propose that restoration of forest-dune ecotones should be considered more often in landscape planning and conservation management.     

The value of terrestrial ecotones as refuges for winter damselflies (Odonata: Lestidae)

Habitat requirements of many species may vary significantly throughout the lifecycle. Species are often forced to exchange their habitats to meet requirements of different life stages. Due to the effect of human activities, however, there is a loss of habitat complexity and a consequent disappearance of species associated with multiple habitat types. This also applies to freshwater invertebrates occurring in temporary habitats. However, it appears that many species are able to meet their habitat requirements even in a human-altered landscape. The aim of this study was to analyze the habitat preferences of the damselfly Sympecma fusca in an area significantly influenced by human interventions. According to the results of a capture-mark-recapture study and generalized additive models, I found that, during a pre-reproductive period (in the autumn), imagoes utilize predominantly insolated ecotones, which constitute only a small fraction of the available terrestrial habitat. During the reproductive period (in spring), however, imagoes completely change their priorities in favor of reproductive success. At this time, males use ecotones only in adverse weather conditions. Ecotones allow the species to survive a long pre-reproductive period. However, suitable habitat conditions may be lost because of inappropriate interventions (e.g., mowing). These small-scale interventions often resemble natural disturbances and may not necessarily lead to the extinction of an entire population. Imagoes are able to move on to different habitat patches, but only if they have alternative habitats. This outcome indicates that maintaining a high heterogeneity of keystone structures is crucial for maintaining high levels of biodiversity.     

Towards a theory of ecotone resilience: coastal vegetation on a salinity gradient

Ecotones represent locations where vegetation change is likely to occur as a result of climate and other environmental changes. Using a model of an ecotone vulnerable to such future changes, we estimated the resilience of the ecotone to disturbances. The specific ecotone is that between two different vegetation types, salinity-tolerant and salinity-intolerant, along a gradient in groundwater salinity. In the case studied, each vegetation type, through soil feedback loops, promoted local soil salinity levels that favor itself in competition with the other type. Bifurcation analysis was used to study the system of equations for the two vegetation types and soil salinity. Alternative stable equilibria, one for salinity-tolerant and one for salinity intolerant vegetation, were shown to exist over a region of the groundwater salinity gradient, bounded by two bifurcation points. This region was shown to depend sensitively on parameters such as the rate of upward infiltration of salinity from groundwater into the soil due to evaporation. We showed also that increasing diffusion rates of vegetation can lead to shrinkage of the range between the two bifurcation points. Sharp ecotones are typical of salt-tolerant vegetation (mangroves) near the coastline and salt-intolerant vegetation inland, even though the underlying elevation and groundwater salinity change very gradually. A disturbance such as an input of salinity to the soil from a storm surge could upset this stable boundary, leading to a regime shift of salinity-tolerant vegetation inland. We showed, however, that, for our model as least, a simple pulse disturbance would not be sufficient; the salinity would have to be held at a high level, as a ‘press’, for some time. The approach used here should be generalizable to study the resilience of a variety of ecotones to disturbances.     

Correspondence of vegetation boundaries to redox barriers in a Northern European moraine plain

Little attention has been devoted to the investigation of the formation and functioning of ecotones at the interfaces between the upland and riparian zones. The margins of riparian mires act as redox geochemical barriers. Such biogeochemical hot spots retain elements that have leached from upland soils, favouring the growth of mesomorphic plants in hydromorphic soils. This paper aims to clarify the correspondence of vegetation borders to horizontal redox barriers of a Northern European moraine plain in Estonia.24 random transects were surveyed on the moraine plain, sampled across sharp soil moisture boundaries as proxies of redox barriers. The shifts in vegetation perpendicular to the boundaries were investigated. Curves of Euclidean distance were computed by moving a 20 m split-window along transects. The curves showed peaks of high dissimilarity a few metres below the redox barriers in the sites of natural soil moisture. In artificially drained sites, the relict redox barriers poorly corresponded to the vegetation borders. We conclude that in the studied moraine plain, the vegetation boundaries between riparian mires and uplands correspond to the redox barriers. The same can be set as a hypothesis for Northern European moraine plains. Related ecotones can be observed on the footslopes, revealing redox barrier in the landscape and related hot spots in cultural landscapes. In field margins, the redox barriers and corresponding ecotones occur below cultivation terraces. The ecotones may represent functional boundaries for delineating wetlands. Man-made drainage removes soil redox barriers and corresponding vegetation boundaries, making the landscape uniform and therefore vulnerable to disturbances. As a management implication, footslope ecotones should be preserved in their natural condition.     

The confusion between scale-defined levels and conventional levels of organization in ecology

Abstract. Conventional levels of organization in ecology can be hierarchically ordered, but there is not necessarily a time or space scale-dependent difference between the classes: cell, organism, population, community, ecosystem, landscape, biome and biosphere. The physical processes that ecological systems must obey are strictly scaled in time and space, but communities or ecosystems may be either large or small. Conventional levels of organization are not scale-dependent, but are criteria for telling foreground from background, or the object from its context. We erect a scheme that separates scale-ordered levels from the conventional levels of organization. By comparing landscapes, communities and ecosystems all at the same scale, we find that communities and ecosystems do not map onto places on the landscape. Rather, communities and ecosystems are wave interference patterns between processes and organisms interfering with and accomodating to each other, even though they occur at different scales on the landscape, and so have different periodicities in their waved behavior. Population members are usually commensurately scaled and so do not generally interact to give interference patterns. Populations are therefore tangible, oratleastcan be assigned a location at an instant in time.     

Association of ecotones with relative elevation and fire in an upland Florida landscape

Question: What are the importance of elevation and fire in maintaining ecotones of Florida scrub assemblages along a gradual topographic gradient? Location: Archbold Biological Station (ABS), 12 km south of Lake Placid, Florida, USA. Methods: Vegetation cover of upland Florida shrublands was quantified using the line‐intercept method along 20 transects traversing similar elevation gradients, stratified by time since fire (TSF). We objectively identified shrubland ecotones using a split moving windows boundary analysis (SMW) with three different window widths. Non‐metric multidimensional scaling ordination was used to determine relationships among plant assemblages defined by SMW. Results: We located up to four ecotones per transect, the majority of which were wide, highly heterogeneous zones. Relative elevation controlled the distribution of plant assemblages in upland Florida shrublands. Ecotones in shrublands > 30 years TSF had relatively low dissimilarity values in SMW, indicating that previously discrete plant assemblages with longer TSF were becoming more similar with time. Conclusions Split Moving Windows (SMW) analysis identified ecotones relatively well although patches generated by oak clonal growth were sometimes identified as ecotones. Fire suppression caused ecotones to become more diffuse, suggesting that without fire at least every 30 years, discrete plant assemblages within upland Florida shrublands will be more continuous.