Herbicide treatments in viticulture can generate highly contrasting mosaics of vegetated and bare vineyards, of which vegetated fields often provide better conditions for biodiversity. In southern Switzerland, where herbicides are applied at large scales, vegetated vineyards are limited in extent and isolated from one another, potentially limiting the distribution and dispersal ability of organisms.
Objectives
We tested the separate and interactive effects of habitat amount and fragmentation on invertebrate abundance using a multi-scale framework, along with additional environmental factors. We identified which variables at which scales were most important in predicting patterns of invertebrate abundance.
Methods
We used a factorial design to sample across a gradient of habitat amount (area of vegetated vineyards, measured as percentage of landscape PLAND) and fragmentation (number of vegetated patches, measured as patch density PD). Using 10 different spatial scales, we identified the factors and scales that most strongly predicted invertebrate abundance and tested potential interactions between habitat amount and fragmentation.
Results
Habitat amount (PLAND index) was most important in predicting invertebrate numbers at a field scale (50 m radius). In contrast, we found a negative effect of fragmentation (PD) at a broad scale of 450 m radius, but no interactive effect between the two.
Conclusions
The spatial scales at which habitat amount and fragmentation affect invertebrates differ, underpinning the importance of spatially explicit study designs in disentangling the effects between habitat amount and configuration. We showed that the amount of vegetated vineyards has more influence on invertebrate abundance, but that fragmentation also contributed substantially. This suggests that efforts for augmenting the area of vegetated vineyards is more beneficial for invertebrate numbers than attempts to connect them.
Urban areas are a particular landscape matrix characterized by a fine-grained spatial arrangement of very diverse habitats
(urban mosaic). We investigated arthropods to analyse biodiversity-habitat associations along five environmental gradients
(age, impervious area, management, configuration, composition) in three Swiss cities (96 study sites). We considered total
species richness and species richness within different functional groups (zoophagous, phytophagous, pollinator, low mobility,
and high mobility species). Information theoretical model selection procedures were applied and predictions were calculated
based on weighted models. Urban areas yielded on average 284 arthropod species (range: 169–361), with species richness correlating
mostly with heterogeneity indices (configuration and composition). Species richness also increased with age of urban settlement,
while enlarged proportions of impervious area and intensified habitat management was negatively correlated. Functional groups
showed contrasted, specific responses to environmental variables. Overall, we found surprisingly little variation in species
richness along the gradients, which is possibly due to the fine-grained spatial interlinkage of good (heterogeneous) and bad
(sealed) habitats. The highly fragmented nature of urban areas may not represent a major obstacle for the arthropods currently
existing in cities because they have probably been selected for tolerance to fragmentation and for high colonisation potential.
Given that built areas are becoming denser, increasing spatial heterogeneity of the urban green offers potential for counteracting
the detrimental effects of densification upon urban biodiversity. By quantifying the expected effects along environmental
gradients, this study provides guidance for managers to set priorities when enhancing urban arthropod species richness. 相似文献
Female sea turtles typically lay several clutches during each nesting season and rest in the time between laying clutches (the internesting period) in the waters off the nesting beach. Adequate protection of turtles in the internesting area requires knowledge on their spatial behaviour and was so far hampered by methodological limitations. Satellite telemetry data of exceptionally high quality allowed us to scrutinize internesting area use of four loggerhead sea turtles nesting in the Bay of Laganas (Zakynthos, Greece). We assessed the efficacy of two zones of a marine reserve with distinct levels of protection (boats are excluded from one zone). Most of the obtained locations of three of the four turtles were within the bay, a result consistent with a strategy to minimize energy expenditure. Turtles showed no obvious preference for the highly protected area of the bay. The availability of warmer water in the less protected area may be more crucial than avoidance of boat disturbance. 相似文献
The decline of insectivorous farmland passerines has been attributed mostly to global decrease in arthropod availability, as a result of intensification of agricultural practices. The diminution of the Alpine Whinchat, once a widespread insectivorous passerine, has been ascribed to nest losses due to earlier and more frequent mowings. However, potential conjugated effects of deteriorated arthropod food availability had yet to be investigated. We compared food supply and nestling diet in intensively vs. traditionally managed grassland. Abundance and diversity of arthropods were much lower in intensive areas, where small-sized invertebrates, which do not enter nestling diet, were also predominant. Parents breeding in intensive habitats fed less biomass to nestlings than adults from traditional habitats. Nestling diet was less diverse and dominated by less profitable prey items in intensive than in traditional habitats. Feeding rate did not differ between the two habitats, but foraging distances from nest tended to be greater in intensive farmland. There were no significant differences in clutch sizes and hatching success with respect to management intensity, but fledging success was higher in traditional habitats. The recent intensification of farming practices has led to a decrease in the availability of grassland invertebrates, and of important Whinchat nestling food in particular, affecting parents’ foraging efficiency and reproductive success. Conservation actions must not only reduce nest losses by postponing mowing, but should also promote grassland farming that is less detrimental to invertebrates. Dominant at the study site, organic grassland farming does seemingly not provide sufficient conditions for Alpine Whinchats. 相似文献
Many river revitalization projects are currently under development, but we still lack proper assessments of their effects on biodiversity, especially regarding non-aquatic vertebrates. We analysed the progressive changes in habitat mosaics, and the demographic response of two rare species of wading birds along a Swiss section of the Rhone river over a period of three decades. During the period preceding revitalization, the diversity of the habitat mosaic had been steadily declining. This impoverishment could however be reverted after 1994, when the revitalization was initiated: in 2006, the re-established habitat matrix was more diverse than at any time during the previous 27 years. The formerly channelized stream underwent radical transformation as it mutated into a heterogeneous braided river boosting pioneer riverine habitats. This has led the two wading bird species to establish significantly more territories than before the revitalization operations. Population size of Actitis hypoleucos and Charadrius dubius increased by 83% and 20%, respectively, between 1995 and 2007. During the same period, A. hypoleucos declined dramatically in Switzerland as a whole, whilst C. dubius showed no distinct population trend. The response of the two waders may have resulted from an increase in the number of lateral arms of the river, where the availability of productive temporary ponds provides excellent foraging opportunities. A significant proportion of these habitats was created by a targeted extraction of sediments with the objective to promote biodiversity while maintaining economic activity and improving security against floods. This suggests that gravel exploitation is not incompatible with efficient river restoration. 相似文献
