基于水文连通性的流域输沙量评估——以堵河流域为例

水文连通性是指泥沙、营养盐等各种物质以水为载体,在空间异质景观或斑块间进行迁移、传输或扩散的便利程度,对流域产沙具有重要影响。为评估基于水文连通性模拟流域输沙量的可行性,以堵河流域为研究对象,分析了1990—2010年流域土壤侵蚀、水文连通性的时空变化特征,并以此估算了流域输沙量。结果表明:1990—2000年流域土壤侵蚀模数与连通程度不断增加,连通性等级主要由低和中低连通性转变为中高和高连通性。2000—2010年流域连通程度和土壤侵蚀模数均呈现不断减小的趋势。此外,输沙量估算值与实测值具有显著的线性关系(R²=0.92),但由于未考虑水库、湖泊等对泥沙输移的拦截效应,输沙量估算值要高于实测值,后续研究需将其纳入模型以更准确地评估流域输沙量。研究结果对于提高模型的适用性以及理解流域泥沙输移过程具有重要意义。     

城市扩张背景下景观破碎化动态演变及空间自相关分析——以南昌市为例

为探究城市扩张与景观破碎化演变过程及其关联机制,以江西省南昌市为例,基于2000—2015年的土地利用数据,运用城市破碎指数(UFI)刻画建设用地的景观破碎化水平; 然后结合形态学空间格局分析(MSPA)和景观连接度分析量化了自然景观和耕地的景观动态演变过程; 最后采用格网分析探究了三者之间的空间自相关动态特征。结果表明:2000—2015年间南昌市共有273.26 km²的耕地及45.61 km²的自然景观转为建设用地,整体城市破碎度指数在研究期内由2.27上升至4.94; 耕地核心区数量在15 a时间内持续衰减,自然生境在前期变化平稳,随着城市化进程的加快,核心及桥接区不断减少,岛状斑块开始增加; 空间自相关分析显示,景观破碎度与自然生境、耕地平均连通概率三者呈负相关,景观破碎度与耕地、自然生境平均连通概率之间的高低聚集区域集中分布在城市扩张的主要区域。2000—2015年城市快速扩张导致的破碎化致使耕地及自然生境景观结构发生改变,景观连通性逐渐丧失。     

Influence of a shrub corridor on movements of passerine birds to a lake littoral zone

A pine forest was separated from a lake littoral zone by a meadow on one area (discontinuous) while these habitats were separated by a shrub strip in another area (continuous). This shrub strip acted as an ecological corridor enhancing the movements of birds between the forest and the littoral reed zone. The number of individuals of non-littoral species that visited the reed zone was higher (p < .001) on the area with the connecting shrub strip in autumn but the number of species visiting the littoral zone was not significantly higher. Significantly more (p < .001) autumn movements by birds in the continuous area were oriented along paths between the forest and the littoral zone whereas movements in the discontinuous area paralleled the littoral and forest zones (p < .001). Movements of birds were concentrated along the edge of the shrub strip. The spatial configuration of the landscape facilitated access by some forest birds to the littoral habitat.     

Predicting land cover changes and their impact on the sediment influx in the Lake Balaton catchment

The land cover pattern in the Lake Balaton catchment (Hungary) has been changing since decollectivization in the 1990s. These land cover changes significantly impact the landscape connectivity, controlling the influx of sediments into the lake. A comparison of high resolution land cover maps from 1981, 2000 and 2005 showed a significant extensification of the agriculture with land cover conversions from arable land and vineyards to grassland and forest. For each land unit transition probabilities were assessed using logistic regression techniques to evaluate to which extent land cover changes are controlled by physical or socio-economic parameters. A stochastic land cover allocation algorithm was applied to generate future land cover patterns. The landscape connectivity for each of the simulated land cover patterns was assessed by means of a distributed routing algorithm. The simulations suggest that further land abandonment in the upslope parts of the catchment will cause a non-linear reduction of average soil erosion rates. The changes, however, have a relatively low impact on the sediment volume entering the lake because of the land unit’s poor connectivity with permanent river channels. The major contributors to the lakes sediment load are the vineyards near the lakeshore. They are likely to be maintained because of their touristic value. A significant reduction of the total sediment input in the lake can be expected only if soil conservation measures in the vineyards near the shorelines are undertaken.     

Animal behavioral adaptation to changing landscapes: spring-staging geese habituate to wind farms

Wind farms are positioned in open landscapes and may cause loss of wildlife habitat due to disturbance, fragmentation, and infrastructure development. Especially flocking geese, swans, ducks and waders are regarded as vulnerable to wind farm development. We compared past and current displacement effects of two onshore wind farms and a line of land-based turbines on spring-staging pink-footed geese (Anser brachyrhynchus) to see if there was evidence of habituation. In one wind farm area, geese previously (1998) (Larsen and Madsen 2000) kept a distance of c. 200 m (the distance at which 50% of peak densities is reached) and they did not go between the turbines; today (2008) they keep a distance of c. 100 m, but do still not enter the wind farm area. In another wind farm, where foraging geese previously (2000) kept a distance of more than 100 m and did not enter the wind farm, they now (2008) forage between the wind turbines and keep a distance of c. 40 m to turbines. In 1998, geese kept a distance of 125 m to a line of turbines, compared to 50 m now. We conclude that geese have behaviorally adapted to changing landscapes created by wind farms. The difference in avoidance between the sites may be due to the sizes of the turbines which in this study were small in both rotor-swept area and in height compared to more recent “industry standard” of 2.5 and 3.0 MW turbines. The study points to the need for longer term studies to properly assess the impact of wind farms on wildlife, including consequent increased risks from inclement weather events of feeding, rafting, and migrating waterfowl.     

The effects of landscape composition and physiognomy on metapopulation size: the role of corridors

We develop and analyze a model that examines the effects of corridor quality, quantity, and arrangement on metapopulation sizes. These ideas were formerly investigated by Lefkovitch and Fahrig (1985) and Henein and Merriam (1990). Our simulations provide results similar to the Henein and Merriam model, indicating that the quality of corridors in a landscape and their arrangement will influence the size of a metapopulation. We then go one step further, describing how corridor arrangement alters the metapopulation, and provide a method for predicting which corridor arrangements should support larger metapopulations. In contrast to the Henein and Merriam model, we find that the number of corridor connections has no influence on the size of a metapopulation in a landscape unless there is an accompanying change in the uniformity of the distribution of corridor connections among patches.     

Taxonomic and functional macroinvertebrate diversity of high-altitude ponds in the Macun Cirque,Switzerland

1. Global environmental change is threatening freshwater biodiversity with ecological impacts predicted to be particularly severe in high-altitude regions. Despite this, an ecological understanding of high-altitude pond networks remains patchy, with only limited knowledge of the environmental and spatial predictors of taxonomic and functional diversity. Moreover, previous studies of pond ecosystems have focused primarily on taxonomic richness and largely overlooked functional diversity.
2. This study examined the influence of local environmental and spatial factors on taxonomic and functional α and β diversity (including the turnover and nestedness-resultant components) of 17 high-altitude (~2,500 m above sea level) pond macroinvertebrate communities, in the Macun Cirque, Switzerland.
3. Spatial processes (pond connectivity) were important drivers for taxonomic α diversity, while local environmental variables (pond permanence and surface area) were important determinants of functional α diversity. Species turnover was the most important component of β diversity for taxonomic composition, and functional composition demonstrated a nested spatial pattern.
4. Variation in taxonomic and functional composition (and the turnover and nestedness components of β diversity) were determined by local environmental variables despite the limited environmental gradients within the pond network. No significant effects of spatial variables on community composition were recorded for either facet of diversity, indicating that compositional variation was determined at a local scale. Water temperature, depth and pond permanence were consistently the most important measured drivers of diversity.
5. Given the importance of both spatial and environmental variables in structuring taxonomic and functional diversity, landscape-scale conservation and management activities that aim to improve or protect high-altitude freshwater biodiversity should focus on maintaining connectivity among ponds and environmental heterogeneity, particularly pond surface area, water depth, and hydroperiod. Understanding the mechanisms driving taxonomic and functional diversity will be critically important for the management and conservation of macroinvertebrate communities in high-altitude pond networks in the face of climatic warming.

     

Genetic differentiation among Atlantic island populations of the brown spiny lobster Panulirus echinatus (Decapoda: Palinuridae)

1. Declines in Panulirus echinatus Smith, 1869 populations along their wide distribution in the Atlantic Ocean have spurred efforts to improve their fisheries management and conservation. In this study, the genetic structure of these populations is reported for the first time.
2. In a survey of 18 species‐specific polymorphic microsatellite markers, 152 individuals were genotyped from five Atlantic oceanic islands, covering most of the insular distribution range of the species. The analyses revealed that P. echinatus is genetically partitioned into two stocks in the Atlantic Ocean. A highly significant genetic structure was observed between north‐east and south‐west Atlantic populations based on fixation index, discriminant analysis of principal components, and structure and barrier analysis.
3. We suggest that the Equatorial Circulation System represents a biophysical barrier that effectively limits migration among Atlantic subtropical gyre systems, as has been described for other species. Other physical and ecological barriers, such as the Mid‐Atlantic Ridge itself, the distance between the eastern and western sides of the Atlantic (Mid‐Atlantic Barrier) and water mass differences, as well as other biological aspects, may also influence larval dispersal and modulate the insular distribution of this species.
4. The results show the existence of two distinct genetic stocks of P. echinatus and have implications for fisheries management in the Atlantic Ocean, including their independent management according to their individual status. The Cabo Verde and the Canarian populations (north‐east Atlantic) showed the lowest level of genetic variability in comparison with the south‐western populations. A combination of factors that have occurred or are occurring in the Canary Islands, such as overfishing and volcanic eruptions, is likely to explain the reduced abundance of this lobster species in the area.

     

Soil erosion and runoff: The need to rethink mitigation strategies for sustainable agricultural landscapes in western Europe

Agricultural landscapes that are intensively farmed, as in western Europe, face the challenge of a transition to more sustainable systems. Although erosion rates are relatively low in western Europe, the agricultural landscape is confronted by the need to mitigate the off-site impacts of erosion. An important challenge is that of disrupting connectivity between runoff and sediment sources, often farmers' fields, and freshwater systems or local communities. Mitigation strategies should include monitoring of erosion rates and off-site impacts and a mix of engineered and alternative measures such as buffer strips and retention ponds. Also needed are supportive government policies and actions including awareness of institutional memory problems and the promotion of farmer education. For the future, the risk of climate change must be appreciated and built into the planning of comprehensive mitigation strategies. Our perspective is that the overall aim should be a ‘sustainable agricultural landscape’ and not simply a reduction of erosion and runoff on farmers' fields.