Consideration of Geography and Wetland Geomorphic Type in the Development of Great Lakes Coastal Wetland Bird Indicators

We examined how geographic distribution of birds and their affinities to three geomorphic wetland types would affect the scale at which we developed indicators based on breeding bird communities for Great Lakes coastal wetlands. We completed 385 breeding bird surveys on 222 wetlands in the US portion of the basin in 2002 and 2003. Analyses showed that wetlands within two ecoprovinces (Laurentian Mixed Forest and Eastern Broadleaf Forest) had different bird communities. Bird communities were also significantly different among five lakes (Superior, Michigan, Huron, Erie, and Ontario) and among three wetland types (lacustrine, riverine, barrier-protected). Indicator values illustrated bird species with high affinities for each group (ecoprovince, lake, wetland type). Species with restricted geographic ranges, such as Alder and Willow Flycatchers (Empidonax alnorum and E. traillii), had significant affinities for ecoprovince. Ten bird species had significant affinities for lacustrine wetlands. Analyses on avian guild metrics showed that Lake Ontario wetlands had fewer long-distant migrants and warblers than other lakes. Numbers of short-distant migrants and total individuals in wetlands were higher in the Eastern Broadleaf Forest ecoprovince. Number of flycatchers and wetland obligate birds were not different among provinces, lakes, or wetland type. One potential indicator for wetland condition in Great Lakes wetlands, proportion of obligate wetland birds, responded negatively to proportion of developed land within 1 km of the wetland. We conclude that, although a guild approach to indicator development ameliorates species-specific geographic differences in distribution, individual species responses to disturbance scale will need to be considered in future indicator development with this approach.     

Identifying the ecological causes of long-term declines of wetland-dependent birds in an urbanizing landscape

Many wetland-dependent birds are thought to be experiencing significant population declines, although population trend data for this suite of birds are rare and the causes of declines poorly understood. We used a 26-year dataset (1980–2005) of wetland bird abundance and distribution among 196 wetlands in northeastern Illinois (i.e., Chicago and its suburbs) to evaluate population trends and identify underlying ecological causes. We used aerial photography and GIS to quantify wetland habitat structure (i.e., the extent of emergent vegetation) and changes in surrounding land use. We then evaluated how changes in land use affected the structure of wetlands and ultimately wetland bird populations. Of the 12 species analyzed, seven experienced significant declines, three showed non-significant declines, and two experienced significant increases. Population declines could not be attributed to wetland loss because none of our wetlands were destroyed. Concurrent research at these wetlands also suggests that neither low adult survival nor poor reproductive success were responsible for the declines. Increased development within 2 km of wetlands, however, was associated with extreme changes in the structure of wetlands. Wetlands tended either to lose much of their vegetation and become open ponds, or become rank stands of dense vegetation. Both changes made wetlands less suitable for many wetland birds. While “no net loss” legislation may protect wetlands from being filled or drained, development near wetlands appears to be altering hydrology, resulting in habitat degradation and population declines of several wetland-dependent bird species.     

Large extents of intensive land use limit community reorganization during climate warming

Climate change is increasingly altering the composition of ecological communities, in combination with other environmental pressures such as high‐intensity land use. Pressures are expected to interact in their effects, but the extent to which intensive human land use constrains community responses to climate change is currently unclear. A generic indicator of climate change impact, the community temperature index (CTI), has previously been used to suggest that both bird and butterflies are successfully ‘tracking’ climate change. Here, we assessed community changes at over 600 English bird or butterfly monitoring sites over three decades and tested how the surrounding land has influenced these changes. We partitioned community changes into warm‐ and cold‐associated assemblages and found that English bird communities have not reorganized successfully in response to climate change. CTI increases for birds are primarily attributable to the loss of cold‐associated species, whilst for butterflies, warm‐associated species have tended to increase. Importantly, the area of intensively managed land use around monitoring sites appears to influence these community changes, with large extents of intensively managed land limiting ‘adaptive’ community reorganization in response to climate change. Specifically, high‐intensity land use appears to exacerbate declines in cold‐adapted bird and butterfly species, and prevent increases in warm‐associated birds. This has broad implications for managing landscapes to promote climate change adaptation.     

Avian Use of Wetlands in Reclaimed Minelands in Southwestern Indiana

We studied the use of mineland wetlands by birds and the relationship between avian communities and wetland characteristics. Data were collected from 20 wetlands in Pike County, Indiana, and included wetland size, depth, water conductivity and salinity, aquatic macroinvertebrate abundance, vegetation, and bird use. Principal component analysis showed that physical variables could be explained by two principal component scores and that wetlands could be grouped on the basis of size and conductivity. Principal component analysis could not reduce vegetation variables to fewer principal component scores, meaning that wetland vegetation characteristics were independent of one another and did not show any trend. Most wetlands had low invertebrate density, and wetlands with higher invertebrate density had low invertebrate diversity. Wetlands with similar habitat characteristics (physical, vegetative, and invertebrate) did not necessarily show similarities in bird assemblages. Bird similarity index values ranged from 0 to 59%, implying that each wetland has its own bird community. Stepwise multiple regression analysis (α= 0.05) relating bird use and habitat characteristics showed that bird species richness increased with the species richness of submergent vegetation and was correlated negatively with the species richness of emergent vegetation. There was no significant relationship between bird species richness or bird species diversity and wetland size. The number of species within different avian guilds correlated with different habitat characteristics. The species richness of submergent plants was a factor that correlated positively with the number of species of several guilds (dabblers, wading birds, and plunge divers). Wetland age was not a factor that determined bird use.     

合肥市小微湿地鸟类多样性的时空格局及其影响因素

小微湿地是城市生态系统的重要组成部分, 也是生物多样性的重要庇护场所。鸟类作为城市小微湿地生态系统的指示类群, 其多样性时空格局受多种环境因子影响。本研究于2020年8月至2021年7月采用样点法对合肥市45个小微湿地鸟类的种类、数量分布和生境因子进行了调查, 并获取湿地面积、湿地形状、建筑面积比例、植被面积比例、环境噪声、人为干扰和城市化指数等生境变量。通过α多样性和β多样性分析, 研究城市小微湿地鸟类多样性的时空特征及其决定因素。采用信息论模型选择和模型平均法以及基于距离矩阵的多重回归模型进行计算, 确定影响鸟类群落α多样性和β多样性及其组分的主要环境因子。结果显示, 研究区域共有鸟类13目39科102种, 其中水鸟31种, 国家二级重点保护鸟类2种, 安徽省重点保护鸟类17种, IUCN濒危物种红色名录中的易危(VU)物种1种。湿地面积和城市化指数对小微湿地陆地鸟类和水鸟的α多样性、β多样性及其组分均具有显著影响, 其中陆地鸟类物种丰富度在中度和低度城市化之间的小微湿地中达到最高值, 面积超过4 ha的小微湿地能维持较多的水鸟物种。植被面积比例对陆地鸟类多样性具有重要的影响, 而建筑面积比例对水鸟多样性具有显著影响。此外, 总体β多样性及其组分计算结果显示物种周转组分占明显优势, 表明城市小微湿地群作为城市复合生态系统的重要组成部分, 加强整体保护更为必要。研究结果对于加强城市鸟类保护和提高城市生态环境质量具有指导意义。     

Development issues in extending plant-based IBIs to forested wetlands in the Midwestern United States

Most plant-based indices of biotic integrity (IBIs) developed for wetlands have focused on emergent wetlands. A Vegetation Index of Biotic Integrity (VIBI-Forest) was developed for forested wetlands in the four large ecoregions of the Ohio. Assessing the effect of human disturbance on the ecological condition of wetland forests is complicated by several factors. First, forest canopies can remain largely intact even after significant degradation of the herb and shrub stratum. Second, increases in total diversity may not be good. In forested wetlands, a major artifact of disturbance is the addition of non-wetland or wetland native or adventive plant species adapted to full sun conditions to their floras. Initial versions of the VIBI-Forest metrics were very sensitive to disturbance-induced increases in diversity. Correcting this problem required modifying or replacing metrics so that only forest dependent species were included in metric calculations. The final VIBI-Forest included metrics which evaluated each forest stratum including the ground layer (% bryophyte), herb layer (shade or seed-less vascular plant species), shrub layer (subcanopy importance value (IV), relative density of young trees), canopy (canopy IV), and composite metrics for all vertical strata (Floristic Quality Assessment Index score, % hydrophytes, % sensitive, % tolerant). Assessing wetland forest condition is further complicated by the fact that some successional communities after canopy death or destruction (shrub swamp, marsh, wet meadow) may have intrinsic value as wetland community types. The solution is not to attempt to derive a one-size-fits-all assessment method but to derive separate protocols for other successional phases that are of value or interest.     

Development of an Indicator to Monitor Mediterranean Wetlands

Wetlands are sensitive ecosystems that are increasingly subjected to threats from anthropogenic factors. In the last decades, coastal Mediterranean wetlands have been suffering considerable pressures from land use change, intensification of urban growth, increasing tourism infrastructure and intensification of agricultural practices. Remote sensing (RS) and Geographic Information Systems (GIS) techniques are efficient tools that can support monitoring Mediterranean coastal wetlands on large scales and over long periods of time. The study aims at developing a wetland indicator to support monitoring Mediterranean coastal wetlands using these techniques. The indicator makes use of multi-temporal Landsat images, land use reference layers, a 50m numerical model of the territory (NMT) and Corine Land Cover (CLC) for the identification and mapping of wetlands. The approach combines supervised image classification techniques making use of vegetation indices and decision tree analysis to identify the surface covered by wetlands at a given date. A validation process is put in place to compare outcomes with existing local wetland inventories to check the results reliability. The indicator´s results demonstrate an improvement in the level of precision of change detection methods achieved by traditional tools providing reliability up to 95% in main wetland areas. The results confirm that the use of RS techniques improves the precision of wetland detection compared to the use of CLC for wetland monitoring and stress the strong relation between the level of wetland detection and the nature of the wetland areas and the monitoring scale considered.     

Contrasting changes in the abundance and diversity of North American bird assemblages from 1971 to 2010

Although it is generally recognized that global biodiversity is declining, few studies have examined long‐term changes in multiple biodiversity dimensions simultaneously. In this study, we quantified and compared temporal changes in the abundance, taxonomic diversity, functional diversity, and phylogenetic diversity of bird assemblages, using roadside monitoring data of the North American Breeding Bird Survey from 1971 to 2010. We calculated 12 abundance and diversity metrics based on 5‐year average abundances of 519 species for each of 768 monitoring routes. We did this for all bird species together as well as for four subgroups based on breeding habitat affinity (grassland, woodland, wetland, and shrubland breeders). The majority of the biodiversity metrics increased or remained constant over the study period, whereas the overall abundance of birds showed a pronounced decrease, primarily driven by declines of the most abundant species. These results highlight how stable or even increasing metrics of taxonomic, functional, or phylogenetic diversity may occur in parallel with substantial losses of individuals. We further found that patterns of change differed among the species subgroups, with both abundance and diversity increasing for woodland birds and decreasing for grassland breeders. The contrasting changes between abundance and diversity and among the breeding habitat groups underscore the relevance of a multifaceted approach to measuring biodiversity change. Our findings further stress the importance of monitoring the overall abundance of individuals in addition to metrics of taxonomic, functional, or phylogenetic diversity, thus confirming the importance of population abundance as an essential biodiversity variable.     

Large-scale changes in community composition: determining land use and climate change signals

Human land use and climate change are regarded as the main driving forces of present-day and future species extinction. They may potentially lead to a profound reorganisation of the composition and structure of natural communities throughout the world. However, studies that explicitly investigate both forms of impact--land use and climate change--are uncommon. Here, we quantify community change of Dutch breeding bird communities over the past 25 years using time lag analysis. We evaluate the chronological sequence of the community temperature index (CTI) which reflects community response to temperature increase (increasing CTI indicates an increase in relative abundance of more southerly species), and the temporal trend of the community specialisation index (CSI) which reflects community response to land use change (declining CSI indicates an increase of generalist species). We show that the breeding bird fauna underwent distinct directional change accompanied by significant changes both in CTI and CSI which suggests a causal connection between climate and land use change and bird community change. The assemblages of particular breeding habitats neither changed at the same speed and nor were they equally affected by climate versus land use changes. In the rapidly changing farmland community, CTI and CSI both declined slightly. In contrast, CTI increased in the more slowly changing forest and heath communities, while CSI remained stable. Coastal assemblages experienced both an increase in CTI and a decline in CSI. Wetland birds experienced the fastest community change of all breeding habitat assemblages but neither CTI nor CSI showed a significant trend. Overall, our results suggest that the interaction between climate and land use changes differs between habitats, and that comparing trends in CSI and CTI may be useful in tracking the impact of each determinant.     

Bats are Not Birds – Different Responses to Human Land‐use on a Tropical Mountain

Land‐use intensification has consequences for biodiversity and ecosystem functioning, with various taxonomic groups differing widely in their sensitivity. As land‐use intensification alters habitat structure and resource availability, both factors may contribute to explaining differences in animal species diversity. Within the local animal assemblages the flying vertebrates, bats and birds, provide important and partly complementary ecosystem functions. We tested how bats and birds respond to land‐use intensification and compared abundance, species richness, and community composition across a land‐use gradient including forest, traditional agroforests (home garden), coffee plantations and grasslands on Mount Kilimanjaro, Tanzania. Furthermore, we asked how sensitive different habitat and feeding guilds of bats and birds react to land‐use intensification and the associated alterations in vegetation structure and food resource availability. In contrast to our expectations, land‐use intensification had no negative effect on species richness and abundance of all birds and bats. However, some habitat and feeding guilds, in particular forest specialist and frugivorous birds, were highly sensitive to land‐use intensification. Although the habitat guilds of both, birds and bats, depended on a certain degree of vegetation structure, total bat and bird abundance was mediated primarily by the availability of the respective food resources. Even though the highly structured southern slopes of Mount Kilimanjaro are able to maintain diverse bat and bird assemblages, the sensitivity of avian forest specialists against land‐use intensification and the dependence of the bat and bird habitat guilds on a certain vegetation structure demonstrate that conservation plans should place special emphasis on these guilds.     

Incomplete recovery of plant diversity in restored prairie wetlands on agricultural landscapes

Restoration efforts are being implemented globally to mitigate the degradation and loss of wetland habitat; however, the rate and success of wetland vegetation recovery post‐restoration is highly variable across wetland classes and geographies. Here, we measured the recovery of plant diversity along a chronosequence of restored temporary and seasonal prairie wetlands ranging from 0 to 23 years since restoration, including drained and natural wetlands embedded in agricultural and natural reserve landscapes in central Alberta, Canada. We assessed plant diversity using the following structural indicators: percent cover of hydrophytes, native and non‐native species, species richness, and community composition. Our findings indicate that plant diversity recovered to resemble reference wetlands in agricultural landscapes within 3–5 years of restoration; however, restored wetlands maintained significantly lower species richness and a distinct community composition compared to reference wetlands located within natural reserves. Early establishment of non‐native species during recovery, dispersal limitation, and depauperated native seed bank were probable barriers to complete recovery. Determining the success of vegetation recovery provides important knowledge that can be used to improve restoration strategies, especially considering projected future changes in land use and climate.     

Evaluation of geographic,geomorphic and human influences on Great Lakes wetland indicators: A multi-assemblage approach

Developing effective indicators of ecological condition requires calibration to determine the geographic range and ecosystem type appropriate for each indicator. Here, we demonstrate an approach for evaluating the relative influence of geography, geomorphology and human disturbance on patterns of variation in biotic indicators derived from multiple assemblages for ecosystems that span broad spatial scales. To accomplish this, we collected abundance information on six biotic assemblages (birds, fish, amphibians, aquatic macroinvertebrates, wetland vegetation, and diatoms) from over 450 locations along U.S. shorelines throughout each of the Great Lakes during 2002–2004. Sixty-six candidate taxon- and function-based indicators analyzed using hierarchical variance partitioning revealed that geographic (lake) rather than geomorphic factors (wetland type) had the greatest influence on the proportion of variance explained across all indicators, and that a significant portion of the variance was also related to response to human disturbance. Wetland vegetation, fish and bird indicators were the most, and macroinvertebrates the least, responsive to human disturbance. Proportion of rock bass, Carex lasiocarpa, and stephanodiscoid diatoms, as well as the presence of spring peepers and the number of insectivorous birds were among the indicators that responded most strongly to a human disturbance index, suggesting they have good potential as indicators of Great Lakes coastal wetland condition. Ecoprovince, wetland type, and indicator type (taxa vs function based) explained relatively little variance. Variance patterns for macroinvertebrates and birds were least concordant with those of other assemblages, while diatoms and amphibians, and fish and wetland vegetation were the most concordant assemblage pairs. Our results strongly suggest it will not be possible to develop effective indicators of Great Lakes coastal wetland condition without accounting for differences among lakes and their important interactions. This is one of the first attempts to show how ecological indicators of human disturbance vary over a broad spatial scale in wetlands.     

Characteristic community structure of Florida’s subtropical wetlands: the Florida wetland condition index for depressional marshes, depressional forested, and flowing water forested wetlands

Land use and land cover change has a marked affect on wetland condition, and different wetland types are affected differentially depending on many abiotic and biotic variables. To assess wetland condition, we have developed a Florida wetland condition index (FWCI) composed of indicators of community structure in the diatom, macrophyte, and macroinvertebrate assemblages for 216 wetlands (n = 74 depressional marsh, n = 118 depressional forested, n = 24 flowing water forested wetlands). Depressional wetlands located along a human disturbance gradient throughout Florida were sampled for each assemblage. Forested flowing water wetlands were sampled for macrophytes only. The landscape development intensity index (LDI) was used to quantify the human disturbance gradient. In general, human disturbance in adjacent areas had the greatest impact on depressional herbaceous wetlands, followed by depressional forested wetlands. Forested flowing water wetlands (i.e., forested strands and floodplain wetlands) were less affected by local conditions, with most of their changes in wetland condition correlated with alterations at the larger watershed scale. Strong correlations between the FWCIs and LDI index scores suggest that changes in community structure can be detected along a gradient of human land use activities adjacent to wetland ecosystems.     

Wetland degradation leads to homogenization of the biota at local and landscape scales

1. We examined whether the anthropogenic degradation of wetlands leads to homogenization of the biota at local and/or landscape scales and, if so, what specific factors account for such an effect. We compared 16 isolated wetlands (Michigan, U.S.A.) that varied in surrounding land use: half had developed, and half undeveloped, riparian zones. Samples of macrophytes, epiphytic diatoms, zooplankton, macroinvertebrates and water chemistry were collected along three transects in each wetland. 2. Developed wetlands were more nutrient‐rich with higher Cl concentrations. The plant community at developed sites was dominated by Lemnaceae (duckweed), while undeveloped wetlands were dominated by rooted, floating‐leaved vegetation and sensitive plant species. Undeveloped wetlands contained heterogeneous and species‐rich plant communities, greater species richness of zooplankton and diatoms, and heterogeneous zooplankton distributions as compared to developed sites. 3. A comparison among wetlands showed that diatom and zooplankton assemblages in developed wetlands were nested subsets of richer biota found in less developed wetlands. Conversely, plant communities were more heterogeneously distributed among developed wetlands at the landscape level. This may be attributable to patchy invasions by exotic species, which were a feature of the degraded wetlands within developed landscapes. 4. Our results indicate that several taxonomic groups showed similar, probably inter‐dependent, responses to wetland degradation and habitat homogenization at both the local and landscape scales. This change in community structure from a species‐rich and heterogeneous community dominated by floating‐leaved plants in undeveloped wetlands, to nutrient‐rich wetlands dominated by duckweed may represent a shift to an alternate stable state.     

Aquatic invertebrate assemblages as potential indicators of restoration conditions in wetlands of Northeastern China

Wetland restoration has been implemented widely but evaluation of the effectiveness of wetland restoration has been limited. In this study, we aimed to investigate the utility of aquatic invertebrate assemblages as potential indicators of restoration condition in wetlands of the Sanjiang Plain, Northeastern China. Results from non‐metric multidimensional scaling analysis of invertebrate assemblages showed that study wetlands (n = 16) divided into two groups: natural wetlands and wetlands that have been restored for 4 years were classified as a group, and impaired wetlands and wetlands restored for only 1 year were classified into another group. After 4 years of recovery, 47.9% of invertebrate taxa found at the natural wetlands could also be found at the restored wetlands, primarily insects with aerial dispersal capabilities for rapid colonization. Indicator species analysis identified differences in community composition among wetland types, and Amphiagrion sp. and Bezzia sp. were indicators of the restored wetlands. In Northeastern China, aquatic invertebrate assemblages and certain indicator species may provide robust measures of wetland restoration. It is urgent for further exploration to monitor restored wetlands in the long‐time series and fully assess the efficiency of the restoration.     

近20年白洋淀湿地水文连通性及空间形态演变

水文连通性是表征湿地格局和功能稳定性的重要指标,连通性的降低通常意味着湿地生态功能的退化,内部能量流动和养分循环的扰乱。选取京津冀最具典型性的白洋淀湿地为案例,将形态学空间格局分析模型(MSPA,Morphological Spatial Pattern Analysis)与连通性指数(IIC,Integral Index of Connectivity;PC,Probability of Connectivity)相结合,从时空两方面分析了白洋淀湿地水文连通性的变化,总结出水文连通性变化的空间形态演变规律。结果表明,1990—2015年间,白洋淀湿地整体连通性较差,以2005年为节点呈现先降低后逐步恢复的趋势;根据MSPA功能类型的变化,将白洋淀湿地空间形态演变分为消退期与恢复期两个阶段。消退期主要表现为核心斑块逐步分裂为分支、环岛、桥接、孤岛等细碎斑块,然后逐渐消退的过程;恢复期各类型主要表现为核心湿地面积逐渐增加,分支向桥接转变的过程。其中核心湿地的面积由1990年的8974.90 hm2,最低下降到2005年2092.97 hm2,到2015年又恢复到4122.14 hm2。整体而言,核心湿地的变化对白洋淀湿地水文连通性变化起主导作用。白洋淀湿地水文连通性降低的影响因素主要有上游补给水量的多少,土地利用变化以及气候变化等因素。研究将MSPA模型与连通性指数相结合的方法,能较好揭示湿地水文连通性变化过程中水文形态组织和运行变化的规律,可为其他地区湿地相关研究提供方法上的借鉴。     

Midsummer zooplankton assemblages in four types of wetlands in the Upper Midwest,USA

The objective of this study was to characterize the zooplankton and phytoplankton assemblages of four different types of wetlands and to evaluate their use as environmental indicators. Total abundances, community composition, and species diversity were evaluated for zooplankton and phytoplankton assemblages from 24 wetlands and related to water quality variables. During August 1995, six representative sites were sampled from four types of wetlands designated as constructed, impacted, non-impacted, or temporary. The plankton assemblages of all wetlands were dominated by cosmopolitan crustacean, rotifer, and phytoplankton taxa typical of lake plankton communities. Species diversity, richness, and evenness of zooplankton and phytoplankton assemblages did not differ significantly among the wetland types. Total zooplankton abundance was significantly (p < 0.01) related to chlorophyll a and total phosphorus concentrations over the range of trophic conditions. Mean zooplankton densities and phytoplankton biovolumes were similar among the wetlands, however, the relative abundances of major zooplankton groups differed among the wetland types. Cyanophytes, primarily Oscillatoria spp., were a major component of the phytoplankton across all four wetland types, and were significantly more abundant within the constructed and temporary sites. On average, rotifers accounted for 79% of total zooplankton abundance within the constructed wetlands and were much less dominant in the non-impacted and temporary wetlands. Cladoceran, copepodite, and adult copepod concentrations were low in the constructed and impacted wetlands and increased in the non-impacted and temporary wetlands in conjunction with increased chlorophytes and cryptophytes. Our preliminary survey suggests that abiotic factors which are known to directly affect phytoplankton may indirectly affect zooplankton composition in such a way as to use zooplankton assemblages as indicators of water quality. However, further study incorporating seasonal dynamics and the influence of predators on zooplankton assemblages is needed to fully assess the use of zooplankton community composition as an environmental indicator for wetland systems. This revised version was published online in July 2006 with corrections to the Cover Date.     

Terrestrial birds as indicators of agricultural-induced changes and associated loss in conservation value of Mediterranean wetlands

During the last decades, agricultural intensification has modified the hydrology of Mediterranean wetlands, as has occurred in the Mar Menor coastal lagoon (SE Spain). Salt-steppe dominated wetlands, characteristic of transitional areas surrounding this lagoon and rich in biodiversity values, are threatened by changes in their water regime originated by land-use changes in the watershed. Traditional dryland cultures have also been replaced by irrigated ones. We assess the direct and indirect changes induced by agriculture on a terrestrial vertebrate community (steppe birds) especially sensitive to these ecosystem changes. This is made on the basis of several surveys of terrestrial birds (excluding aerial feeders and raptors) carried out between 1984 and 2008 in a representative wetland of the lagoon's continental margin (Marina del Carmolí). The changes in this bird assemblage reflect the hydrological modifications induced by agriculture at the watershed scale, which have significant effects on the relative representation of wetland habitats. Bird metrics and indices (species abundance, taxonomic composition, conservation value) describe these community changes as the combination of early declines in some species and families, and transient or late increases in other. In the long term, the family Alaudidae (and particularly species like Melanocorypha calandra) have lost importance to the benefit of Turdidae and Fringillidae. The area of salt-steppe explains a large part of the variation in the abundance of Alaudidae, while most variation of Turdidae and Fringillidae respond to the area of saltmarsh. Some Alaudidae seem to take advantage of the intermediate stages of saltmarsh expansion (Calandrella rufescens), or from the marginal irrigated crops fringing the wetland (Calandrella brachydactyla) that could compensate the loss of original agricultural habitats. Habitat changes in the wetland have occurred in three differentiated stages, and modify the steppe bird community towards a more heterogeneous assemblage including scrubland and palustrine species. Among three indices of ornithological value, only that based on the EU Bird's Directive Annex I species was negatively affected, but since the wetland has been designated a Specially Protected Area under this regulation, this represents a management failure. There exists some chance, however, to manage peripheral cropland in favour of biodiversity. The importance of monitoring in conservation evaluation and management is also stressed, since the terrestrial bird community of this wetland has not been regularly surveyed. In fact, its evaluation against the Bird's Directive criteria was made in a period of quick departure from the original, good ecological state of the wetland.     

The ecological condition of geographically isolated wetlands in the southeastern United States: The relationship between landscape level assessments and macrophyte assemblages

Geographically isolated wetlands (GIWs) are common features of the Dougherty Plain physiographic region in southwestern Georgia. Due to lack of protection at the state and federal levels, these wetlands are threatened by intensive agricultural and silvicultural land uses common in the region. Recently, the ecological condition of such GIWs was assessed for the southeastern United States using the Landscape Development Intensity Index (LDI), a practical assessment tool that relies on remotely sensed land use and land cover (LULC) data surrounding isolated wetlands to rapidly predict wetland condition. However, no assessments have been attempted for GIWs in the Dougherty Plain specifically. Our goal was to develop a framework to guide and refine remote assessment of wetland condition within this agriculturally intense region of the southeastern USA. In this study, we characterized human disturbances associated with isolated wetlands in the Dougherty Plain, and paired the rapid assessment of GIWs using LDI with an intensive assessment of wetland plant communities. Specifically, we: (1) examined how macrophyte assemblages and vegetation metrics vary across a human disturbance gradient in the Dougherty Plain; (2) compared multiple condition assessment outcomes using variations of the LDI method that differed in spatial extent and resolution of LULC categories; and (3) determined the predicted condition of GIWs in the Dougherty Plain as indexed by LDI and compared with region-wide assessments of GIWs of the southeastern USA. Generally, the relationship between wetland plant communities and surrounding land use supported the assumptions of the LDI index in that wetlands surrounded by agricultural land use classes featured distinct plant communities relative to those surrounded by forested land use classes. Our results indicated that finer spatial resolution of LULC data improved the predictive ability of LDI. However, based on incongruence between wetland vegetation composition and LDI scores in some forested landscapes, this study identified limitations of the LDI assessment method, particularly when applied in regions in which prescribed fire is an important ecological driver of vegetation and habitat. Thus, we conclude that LDI may be biased toward an overestimation of reference condition GIWs, even though the habitat may be functionally degraded by the absence of natural processes such as fire. Regardless, relative to the assessment of the entire southeastern US, a greater proportion of total GIWs of the Dougherty Plain were identified as impaired due to the intensity of irrigated agricultural land use.     

若尔盖高原土地利用变化对生态系统服务价值的影响

运用GIS和遥感技术分析了若尔盖高原1990年、2000年和2005年的土地利用/覆盖特征, 在此基础上, 使用生态价值系数(C)计算出该区生态系统服务价值, 并使用敏感性指数(CS)对所选的C值进行验证. 结果表明, 该区域1990-2005年间生态系统服务价值从603.10?108元减少到586.07?108元, 共损失17.03?108元, 且损失量和损失幅度呈加速增加趋势; 该区域生态系统服务价值中, 废物处理价值最高, 水源涵养价值次之, 食物生产价值最低, 且各服务类型的价值均呈持续减小趋势; 若尔盖高原1990和2005年人均生态系统服务价值分别为38.93万元和27.03万元, 表明若尔盖高原由于人口增长和土地退化, 环境压力呈明显增大趋势. 湿地和草地退化是导致该区域生态系统服务价值减少的主要原因, 尤其是湿地退化. CS检验说明本文所选C值较为合理.