Untangling interactions: do temperature and habitat fragmentation gradients simultaneously impact biotic relationships?

Gaining insight into the impact of anthropogenic change on ecosystems requires investigation into interdependencies between multiple drivers of ecological change and multiple biotic responses. Global environmental change drivers can act simultaneously to impact the abundance and diversity of biota, but few studies have also measured the impact across trophic levels. We firstly investigated whether climate (using temperature differences across a latitudinal gradient as a surrogate) interacts with habitat fragmentation (measured according to fragment area and distance to habitat edges) to impact a New Zealand tri-trophic food chain (plant, herbivore and natural enemy). Secondly, we examined how these interactions might differentially impact both the density and biotic processes of species at each of the three trophic levels. We found evidence to suggest that these drivers act non-additively across trophic levels. The nature of these interactions however varied: location synergistically interacted with fragmentation measures to exacerbate the detrimental effects on consumer density; and antagonistically interacted to ameliorate the impact on plant density and on the interactions between trophic levels (herbivory and parasitoid attack rate). Our findings indicate that the ecological consequences of multiple global change drivers are strongly interactive and vary according to the trophic level studied and whether density or ecological processes are investigated.     

城市景观格局演变的生态环境效应研究进展

快速城市化过程剧烈影响着下垫面变化,直接带来了交通拥挤、资源短缺、环境污染、生态恶化等诸多问题,所有这些问题的出现均与景观格局演变密切相关,研究城市景观格局演变及其生态环境效应正在成为全社会关注的热点.系统总结了城市化过程对景观格局演变的影响,分析了城市景观格局演变的热环境效应、水环境效应、生态服务效应,以及城市生态用地与生态安全格局设计等方面的研究进展.指出了目前城市景观演变与生态环境效应研究中存在的问题与不足:(1)现有研究侧重于景观格局演变的量化分析和景观格局指数的计算,较少关注景观格局演变对生态环境及其区域生态安全的影响;(2)城市景观格局演变与热岛效应研究多局限于两者数理统计关系的分析,对于城市热环境形成的机理缺乏深入研究;(3)城市景观格局演变与大气环境效应方面更多研究关注绿地及其空间布局在吸收和降解大气污染物、固体颗粒物方面的作用,对城市景观格局演变的大气环境综合效应以及大气灰霾效应影响机理重视不够;(4)如何通过合理设置生态用地,有效提高城市生态服务功能和保障城市生态安全,目前仍缺乏深入而又系统的研究.下一步的研究中,需要综合多尺度的景观信息来揭示城市景观的演变机理和环境效应,构建基于城市空间扩展和生态服务效应评价的城市生态空间优化决策模型,探讨城市生态空间优化模式与安全格局.     

Effects of landscape structure and land-use intensity on similarity of plant and animal communities

Aim Species richness in itself is not always sufficient to evaluate land management strategies for nature conservation. The exchange of species between local communities may be affected by landscape structure and land‐use intensity. Thus, species turnover, and its inverse, community similarity, may be useful measures of landscape integrity from a diversity perspective. Location A European transect from France to Estonia. Methods We measured the similarity of plant, bird, wild bee, true bug, carabid beetle, hoverfly and spider communities sampled along gradients in landscape composition (e.g. total availability of semi‐natural habitat), landscape configuration (e.g. fragmentation) and land‐use intensity (e.g. pesticide loads). Results Total availability of semi‐natural habitats had little effect on community similarity, except for bird communities, which were more homogeneous in more natural landscapes. Bee communities, in contrast, were less similar in landscapes with higher percentages of semi‐natural habitats. Increased landscape fragmentation decreased similarity of true bug communities, while plant communities showed a nonlinear, U‐shaped response. More intense land use, specifically increased pesticide burden, led to a homogenization of bee, bug and spider communities within sites. In these cases, habitat fragmentation interacted with pesticide load. Hoverfly and carabid beetle community similarity was differentially affected by higher pesticide levels: for carabid beetles similarity decreased, while for hoverflies we observed a U‐shaped relationship. Main conclusions Our study demonstrates the effects of landscape composition, configuration and land‐use intensity on the similarity of communities. It indicates reduced exchange of species between communities in landscapes dominated by agricultural activities. Taxonomic groups differed in their responses to environmental drivers and using but one group as an indicator for ‘biodiversity’ as such would thus not be advisable.     

A multidisciplinary study of the lake Bjäresjösjön (S Sweden): land-use history,soil erosion,lake trophy and lake-level fluctuations during the last 3000 years

The lake Bjäresjösjön, Southern Scania, Southern Sweden, was studied in the context of the project The cultural landscape of the past 6000 years in Southern Sweden. Pollen, plant macrofossils, diatoms, physical and chemical analysis, magnetic measurements and radiometric methods (²¹⁰Pb, ¹⁴C) have been used to study palaeoecological changes, i.e. climate, land use, lake trophy and soil erosion during the past 3000 years. This multidisciplinary study shows striking responses of diatom communities, physical and chemical characteristics, sediment yields and magnetic parameters to land-use changes and lake-level fluctuations. Moreover, the latter are closely related to the settlement history at the site, inferred from archaeological records and historical sources.Before 650 AD, the limnological development was affected mainly by lake-level fluctuations, but partly also by human impact (extensive forest clearings and dominant pastoral farming). With the expansion of arable farming (around 650 AD), human impact on the landscape was the major factor influencing soil erosion processes in the catchment and limnological changes in the lake.     

New approaches to prehistoric land-use reconstruction in south-western Germany

Botanical on-site and off-site data relating to Late Neolithic and Bronze Age settlement phases in south-western Germany are compared with a view to reconstructing economic and environmental change. The large differences between the Neolithic and Bronze Age as regards forest composition, crops and crop weeds, and charcoal input are explained in terms of different types of agronomic systems and hence cultural landscape. In the Late Neolithic, shifting cultivation, involving slash and burn, was practised with the result that the landscape was largely dominated by tall shrubs. In the Bronze Age there were more or less permanent arable fields with only short fallow phases. The agronomic system and the resulting cultural landscape was already similar to that of the medieval period and, especially, early medieval time.     

The regional effects of CO2 and landscape change using a coupled plant and meteorological model

A meteorological model, the Regional Atmospheric Modelling System (RAMS), and a plant model, the General Energy and Mass Transfer Model (GEMTM), are coupled in this study. The integrated modelling system was used to investigate regional weather conditions in the central grasslands of the USA for three experimental scenarios: ? land cover is changed from current to potential vegetation; ? radiative forcing is changed from 1 × CO₂ to 2 × CO₂; and ? biological CO₂ partial pressures are doubled. Results indicate that the biological effect of enriched CO₂, and of land‐use change exhibit dominant effects on regional meteorological and biological fields, which were observed for daily to seasonal time scales and grid to regional spatial scales. Simulated radiation impacts of 2 × CO₂ were minimal, with interactive effects between the three experimental scenarios as large as the radiational impact alone. Model results highlight the importance of including 2 × CO₂ biological effects when simulating possible future changes in regional weather.     

GLOBIO3: A Framework to Investigate Options for Reducing Global Terrestrial Biodiversity Loss

The GLOBIO3 model has been developed to assess human-induced changes in biodiversity, in the past, present, and future at regional and global scales. The model is built on simple cause–effect relationships between environmental drivers and biodiversity impacts, based on state-of-the-art knowledge. The mean abundance of original species relative to their abundance in undisturbed ecosystems (MSA) is used as the indicator for biodiversity. Changes in drivers are derived from the IMAGE 2.4 model. Drivers considered are land-cover change, land-use intensity, fragmentation, climate change, atmospheric nitrogen deposition, and infrastructure development. GLOBIO3 addresses (i) the impacts of environmental drivers on MSA and their relative importance; (ii) expected trends under various future scenarios; and (iii) the likely effects of various policy response options. GLOBIO3 has been used successfully in several integrated regional and global assessments. Three different global-scale policy options have been evaluated on their potential to reduce MSA loss. These options are: climate-change mitigation through expanded use of bio-energy, an increase in plantation forestry, and an increase in protected areas. We conclude that MSA loss is likely to continue during the coming decades. Plantation forestry may help to reduce the rate of loss, whereas climate-change mitigation through the extensive use of bioenergy crops will, in fact, increase this rate of loss. The protection of 20% of all large ecosystems leads to a small reduction in the rate of loss, provided that protection is effective and that currently degraded protected areas are restored. Author Contributions  RA—Writing, study design, data analyses; MvO—Writing, research; LM— Writing, data analyses; CN—Contribution to method; MB—Research, data analyses; BtB—Contribution to method.     

Balancing food production and nature conservation in the Neotropical dry forests of northern Argentina

The growing human population and the increase in per capita food consumption are driving agriculture expansion and affecting natural ecosystems around the world. To balance increasing agriculture production and nature conservation, we must assess the efficiency of land‐use strategies. Soybean production, mainly exported to China and Europe, has become the major driver of deforestation in dry forest/savanna ecosystems of South America. In this article we compared land cover patterns (based on satellite imagery) and land‐use and human population trends (based on government statistics) in regions with two contrasting development pathways in the Chaco dry forests of northern Argentina, since the early 1970s. The area (ca. 13 million hectares) includes one of the largest continuous patches of tropical dry forests and has experienced rapid land‐use change. In the region where land use has been driven by government‐sponsored colonization programs, the expansion of extensive grazing has led to a growing rural population, low food production, and widespread environmental degradation. In contrast, in the region dominated by market‐driven soybean expansion, the rural population has decreased, food production is between 300% and 800% greater, and low‐density extensive cattle production has declined over extensive remaining forested areas, resulting in a land‐use trend that appears to better balance food production and nature conservation.     

Rotational fallows as overwintering habitat for grassland arthropods: the case of spiders in fen meadows

Regular mowing of grassland is often necessary for plant conservation, but uncut vegetation is needed by many arthropods for overwintering. This may lead to conflicting management strategies for plant and arthropod conservation. Rotational fallows are a possible solution. They provide a spatio-temporal mosaic of mown and unmown areas that may combine benefits to both plants and arthropods. We tested if rotational fallows enhance spider overwintering in fen meadows. Rotational fallows consisted of three adjoining strips 10 m wide and 35–50 m long. Each year, one of these strips was left unmown (fallow) in an alternating manner so that each strip was mown two out of three years. Spiders were sampled during spring with emergence traps in nine pairs of currently unmown fallow strips and completely mown reference plots. Fallows significantly enhanced orb-weavers (Araneidae), sac spiders (Clubionidae) and ground spiders (Gnaphosidae). However, only 4.7% of the total variation in community composition was attributable to fallows. Community variation was larger between landscapes (34.5%) and sites (38.2%). Also β diversity was much higher between landscapes (45 species) and sites (22 species) than between fallows and mown reference plots (10 species). We conclude that the first priority for spider conservation is to preserve as many fen meadows in different landscapes as possible. Locally, rotational fallows enhance overwintering of the above-mentioned spider families, which are sensitive to mowing in other grassland types as well. Thus, rotational fallows would probably foster spider conservation in a wide range of situations. However, stronger effects can be expected from larger and/or older fallow areas.     

Habitat preferences of red-listed fungi and bryophytes in woodland key habitats in southern Sweden – analyses of data from a national survey

The aim of this study was to identify habitat preferences of red-listedepiphytic and epixylic bryophyte, lichenized and non-lichenized fungi speciesinwoodland key habitats (WKHS) (areas less than 10 ha, where foreststructures indicate occurrence of red-listed species) in southern Sweden. Therelative importance of different groups of environmental factors was assessedwith partial canonical correspondence analysis techniques and across-validationapproach using data from 7196 selected WKHs. Different woody substrates (oldtrees, logs and snags) made up the most important variable group for occurrenceof red-listed species (30% unique explainable variation). Species associatedwith Fagus sylvatica and Picea abieshabitats, but also species associated with Quercus spp.andPopulus tremula habitats showed distinct habitatpreferences. The second most important variable group (16% unique explainablevariation) was geographical location. A west–east gradient was identified, andspecies concentrated to Baltic islands in the east were separated from otherspecies. This gradient, and an identified south–north gradient, probablyreflect differences in temperatures and rainfall between different regions.Among the remaining variable groups, historical land-use, ground conditions andforest stand composition were of similar importance (5–7% uniqueexplainable variation). Traditional management regimes resulting in semi-openforest habitats (leaf harvesting, forest grazing and selective cutting) wereassociated with the occurrence of many species, probably due to differences inmicroclimate between sites of different openness. Furthermore, a groundmoisturegradient extending from species associated with dry sites (mainly lichenizedfungi) to species associated with wet sites (mainly bryophytes), and a nutrientgradient from species associated with nutrient-poor sites to species occurringat nutrient-rich sites, were identified. Thus, conservation measures are neededin a broad spectrum of habitats with different substrates. Also sites withsimilar substrates, but situated in different regions (and climates), or withdifferent ground moisture and nutrient conditions are needed to cover the fullspectrum of habitat conditions suitable for different red-listed bryophytes andfungi.