Areas Of Semi-natural Habitats Research Articles

Identification and characteristic analysis of semi-natural habitats in China's economically developed areas: New insights to inform cultivated land system ecological conservation

Identifying and characterizing semi-natural habitats (SNHs) are important to the ecological conservation of cultivated land systems and implementing China's ecological civilization strategy. This study revealed the concept and characteristics of SNHs in Chinese cultivated land systems regarding human activities, resource types, and spatial landscape patterns. The resource quantity, landscape quality, and spatial distribution of SNHs in Southern Jiangsu's cultivated land system were analyzed by constructing the identification model of “land use/land cover type-cultivated land use intensity-spatial landscape pattern”. The results showed that the area of SNHs in Southern Jiangsu's cultivated land system was 25.35%, significantly influenced by cultivated land intensification and expansion. The higher the cultivated land use intensity, the lower the quantity of SNHs, and the proportion of SNHs in the intensive-use pattern was only 2.97%. 68.18% of the SNHs in Southern Jiangsu were water, and habitats for important species, such as woodland, grassland, wetlands, and bare land, were scarce. A small patch area, high landscape fragmentation, poor landscape richness and diversity, and low connectivity accompanied increased cultivated land use intensity. From the extensive to intensive utilization, the spatial spread of SNHs from low-value aggregation to high-value scatter areas, with hotspot areas of cultivated land use intensity and SNHs existing only in a small part of Nanjing and Changzhou. This study provides a scientific reference for the rehabilitation and restoration of SNHs in the context of the ecological transformation of land use. It promotes the sustainable intensification of cultivated land systems. It also provides new ideas for linking ecological and urban spaces to form a stable and systematic national ecological safety network.

Incorporating Landscape Character in Cork Oak Forest Expansion in Sardinia: Constraint or Opportunity?

Cork oak (Quercus suber) is a declining woodland species across the island of Sardinia, despite its former economic importance for wine production and its significance for biodiversity. In particular, cork oak forests (COFs) on the island have seen a 29% decrease in the past 45 years. A spatial GIS model was developed to determine suitability for the expansion of cork oak forests on the island. The model uses a set of simple spatial decision rules based on principles of landscape ecology and expert opinion to assign a suitability score for pure cork oak forests to every land use parcel in Sardinia. These rules include the type of existing land parcel, its size, distance to existing cork oak forest, and the area of seminatural habitats in its neighborhood. This was coupled with a map of landscape types to assist with the development of policy for the protection of cork oak forests across Sardinia. The results show that there is an area of 116,785 ha potentially suitable for cork oak forest expansion in Sardinia, with the largest area of potential habitat on granitic mountains. There is a substantial overall agreement (Cohen’s kappa = 0.61) between the suitability map produced and the historical reference map. The model is flexible and can be rerun to reflect changes in policy relating to agri-environmental targets for habitats and species.

Influences of oilseed rape area and aggregation on pollinator abundance and reproductive success of a co-flowering wild plant

Mass-flowering crops such as oilseed rape (Brassica napus) are attractive for some pollinators. Consequently, flowering oilseed rape fields may compete for pollinators with co-flowering wild plants occurring in adjacent non-crop habitats. We evaluated the influence of flowering oilseed rape through both its area and its configuration in the landscape on pollinator abundance and on the reproductive success of a co-flowering wild plant functionally close to oilseed rape in surrounding grasslands. We monitored the production of seeds of a pollinator-generalist plant, Cardamine pratensis, and sampled pollinator communities in 22 permanent grasslands. To understand the landscape effect of oilseed rape, we quantified its area and aggregation in the landscape at 1 000 m around each grassland. We measured the flower abundance in the grasslands and C. pratensis conspecific plant abundance to consider local influences. At the landscape scale, C. pratensis seed set was unaffected by the aggregation of oilseed rape patches but it was reduced by increasing oilseed rape area in the landscape. At the local scale, the conspecific plant abundance enhanced seed set (i.e. facilitation effect), whereas flower abundance in the grassland reduced it (i.e. competition effect). Analyses revealed a significant positive correlation between seed set and honeybee abundance, but no correlation was found between seed set and solitary bee abundance. Oilseed rape aggregation and the area of semi-natural habitats in the landscape had a weak negative effect on honeybee abundance. Oilseed rape area had either a positive or a negative effect on solitary bee abundance depending on oilseed rape aggregation in the landscape. Flowering oilseed rape can either enhance or reduce the pollinator abundance and the reproductive success of wild plants depending on its quantity and spatial arrangement. Guidance for plant and pollinator conservation should therefore consider both landscape aspects.

Dominance of cropland reduces the pollen deposition from bumble bees

Intensive agricultural landscapes can be hostile for bees due to a lack of floral and nesting resources, and due to management-related stress such as pesticide use and soil tillage. This threatens the pollination services that bees deliver to insect-pollinated crops. We studied the effects of farming intensity (organic vs. conventional, number of insecticide applications) and availability of semi-natural habitats at the field and landscape scale on pollinator visits and pollen delivery to pumpkin in Germany. We found that wild bumble bees were the key pollinators of pumpkin in terms of pollen delivery, despite fivefold higher visitation frequency of honey bees. Critically, we observed that the area of cropland had stronger effects on bees’ pollen deposition than the area of seminatural habitats. Specifically, a 10% increase of the proportion of cropland reduced pollen delivery by 7%. Pumpkin provides a striking example for a key role of wild pollinators in crop pollination even at high numerical dominance of honey bees. In addition, our findings suggest that habitat conversion to agricultural land is a driver of deteriorating pollination. This underlines the importance to maintain sufficient areas of non-crop habitats in agricultural landscapes.

Current and previous spatial distributions of oilseed rape fields influence the abundance and the body size of a solitary wild bee, Andrena cineraria, in permanent grasslands.

Wild bees are essential pollinators whose survival partly depends on the capacity of their environment to offer a sufficient amount of nectar and pollen. Semi-natural habitats and mass-flowering crops such as oilseed rape provide abundant floristic resources for bees. The aim of this study was to evaluate the influences of the spatial distribution of semi-natural habitats and oilseed rape fields on the abundance and the mean body size of a solitary bee in grasslands. We focused on a generalist mining bee, Andrena cineraria, that forages and reproduces during oilseed rape flowering. In 21 permanent grasslands of Eastern France, we captured 1 287 individuals (1 205 males and 82 females) and measured the body size of male individuals. The flower density in grasslands was quantified during bee captures (2016) and the landscape surrounding grasslands was characterized during two consecutive years (2015 and 2016). The influence of oilseed rape was tested through its distribution in the landscape during both the current year of bee sampling and the previous year. Bee abundance was positively influenced by the flower density in grasslands and by the area covered by oilseed rape around grasslands in the previous year. The mean body size of A. cineraria was explained by the interaction between flower density in the grassland and the distance to the nearest oilseed rape field in the current year: the flower density positively influenced the mean body size only in grasslands distant from oilseed rape. A. cineraria abundance and body size distribution were not affected by the area of semi-natural habitats in the landscape. The spatial distribution of oilseed rape fields (during both the current and the previous year) as well as the local density of grassland flowers drive both bee abundance and the mean value of an intraspecific trait (body size) in permanent grasslands. Space-time variations of bee abundance and mean body size in grasslands may have important ecological implications on plant pollination and on interspecific interactions between pollinators. Specifically, a competition between bee species for nesting sites might occur in oilseed rape rich landscapes, thus raising important conservation issues for bee species that do not benefit from oilseed rape resources.

Impacts of Urban Areas and Their Characteristics on Avian Functional Diversity

Urban development is rapidly expanding across the globe and is a major driver of environmental change. Despite considerable improvements in our understanding of how species richness responds to urbanisation, there is still insufficient knowledge of how other measures of assemblage composition and structure respond to urban development. Functional diversity metrics provide a useful approach for quantifying ecological function. We compare avian functional diversity in 25 urban areas, located across the globe, with paired non-urban assemblages using a database of 27 functional traits that capture variation in resource use (amount and type of resources and how they are acquired) across the 529 species occurring across these assemblages. Using three standard functional diversity metrics (FD, MNTD and convex hull) we quantify observed functional diversity and, using standardized effect sizes, how this diverges from that expected under random community assembly null models. We use regression trees to investigate whether human population density, amount of vegetation and city size (spatial extent of urban land), bio-region and use of semi-natural or agricultural assemblages as a baseline modulate the effect of urbanisation on functional diversity. Our analyses suggest that observed functional diversity of urban avian assemblages is not consistently different from that of non-urban assemblages. After accounting for species richness avian functional diversity is higher in cities than areas of semi-natural habitat. This creates a paradox as species responses to urban development are determined by their ecological traits, which should generate assemblages clustered within a narrow range of trait space. Greater habitat diversity within cities compared to semi-natural areas dominated by a single habitat may enhance functional diversity in cities and explain this paradox. Regression trees further suggest that smaller urban areas, lower human population densities and increased vegetation all enhance the functional diversity of urban areas. A city’s attributes can thus influence the functional diversity of its biological assemblages, and their associated ecological functions. This has important implications for the debate regarding how we should grow the world’s cities whilst maintaining their ecological function.

Landscape composition affects parasitoid spillover

The intensification of agriculture has led to a severe simplification of agricultural landscapes, resulting in a marked reduction in the diversity of insect natural enemies. However, how this simplification shapes the movement of insect parasitoids between crop and non-crop habitats (i.e., spillover) is still unclear. We examined the potential spillover of tachinid parasitoids from semi-natural habitats into apple orchards across different landscapes. We sampled commercial apple orchards localized in three landscape types (forest-, grassland- or apple-dominated landscapes) to first evaluate if landscape composition affects the local species richness in apple orchards. Second, we tested whether the contribution of forest and grassland habitats to the local tachinid community composition of apple orchards changes according to landscape composition. We found that landscape composition did not affect local tachinid species richness in apple orchards, while it affected the species spillover. Independently of the landscape, we found highly nested communities of tachinids between apple orchards and forest habitats suggesting a strong spillover of tachinids between these habitats. In contrast, tachinids in apple orchards were nested with grassland habitats only in landscapes dominated by apple orchards. Our results have important implications for the conservation of insect parasitoids in agricultural landscapes, as the spillover of species in the crop can be affected by the type and the area of semi-natural habitats in the surrounding landscape.

Effects of fertilizer application on summer usage of cereal fields by farmland birds in central Hungary

Capsule Despite negative effects of inorganic fertilizer on weeds and invertebrates in cereal fields, impacts on bird usage were weak and non-linear. Aim To assess the effects of inorganic fertilizer application to winter cereals on breeding-season usage by farmland birds. Methods We measured bird usage of winter-sown cereal fields across a gradient of inorganic fertilizer inputs and tested for influences of management intensity and availability of semi-natural habitat on species richness and abundance of farmland birds. Results Avian species richness and bird abundance were unrelated to fertilizer inputs, and declined at higher levels of total vegetation cover. Sky Lark abundance increased, while Yellow Wagtail counts declined with the extent of semi-natural habitat. Sky Lark abundance increased with vegetation cover and peaked at an intermediate level of weed species richness. Yellow Wagtail counts peaked at intermediate levels of fertilizer inputs. Conclusions Compared with much of western Europe, cereal production in central Hungary is characterized by modest fertilizer inputs and large areas of semi-natural habitat. There was little evidence that increased applications of fertilizer are likely to have negative impacts on farmland birds, although increased application might reduce habitat suitability for Yellow Wagtails. Loss of semi-natural habitat is likely to have negative impacts on Sky Larks.

Interacting effects of landscape context and habitat quality on flower visiting insects in agricultural landscapes

Summary Landscape context and habitat quality may have pronounced effects on the diversity of flower visiting insects. We investigated whether the effects of landscape context and habitat quality on flower visiting insects interact in agricultural landscapes in the Netherlands. Landscape context was expressed as the area of semi-natural habitats or the density of linear landscape features, and was quantified at spatial scales ranging from 250 to 2000 m. Habitat quality was determined as flower abundance. Species richness and abundance of hoverflies and bees were determined along 16 stream banks experiencing similar environmental conditions but situated in areas with contrasting landscape context. Only flower abundance and the area of semi-natural habitats within 500–1000 m were significantly related to species richness of hoverflies and bees and these factors had interacting effects on both species groups. Our results suggest that the regional area of semi-natural habitats had a positive effect on hoverfly species richness when flower abundance was relatively high, but not when flower abundance was low. Moreover, flower abundance had positive effects on hoverfly species richness only in areas with relatively many semi-natural habitats. Contrastingly, flower abundance had a more positive effect on bee species richness in landscapes with few semi-natural habitats compared to landscapes with more semi-natural habitats. Our results suggest that the importance of landscape context for the species richness of flower visiting insects depends upon the quality of the habitat patches.

TheArrhenatheretumon set-aside at Aldroughty, Elgin

Summary The Arrhenatheretum on set-aside in two fields at Aldroughty Farm, Elgin, is described. This vegetation is noteworthy because some of the attractive grassland and wetland species in it are very rare on Scottish set-aside. The species involved (e.g. Carex flacca, Dactylorhiza purpurella, Rhinanthus minor) are generally entirely absent from lowland farmed landscapes, but populations do occur in areas of semi-natural habitat at Aldroughty. It is concluded that, as far as most long-term set-aside is concerned, vegetation of greater conservation value does not develop thereon owing to non-availability of the necessary seeds.