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101.
Several biodiversity features can be linked to landscape heterogeneity, that, in turn, can be informative for management and conservation purposes. Usually, the more the landscape is complex the more the biodiversity increases. Biodiversity indicators can be a useful tool to assess biodiversity status, in function of landscape heterogeneity. In this study, we developed a biodiversity indicator, based on Shannon diversity index and built from distribution maps of protected species. With such an approach, we seek to evaluate the feasibility of using a combination of target species as a surrogate for assessing the status of the whole bird community. Our approach was spread over multiple spatial scales, to determine which was the most informative. We selected four species protected by European regulation and generated a presence-absence map from species distribution modelling. We, therefore, used the FRAGSTATS biodiversity metric to calculate Shannon index for the overlapped presence-absence maps, at two spatial scales (500 m and 1000 m). Then, the relationships with the whole community was assessed through generalised least square models, at the spatial scale of 4 ha, 9 ha and 25 ha. Results showed that the higher rate of variability of community was explained by the biodiversity indicator at 1000 m scale. Indeed, the more informative spatial scale for the whole bird community was 9 ha. In addition, a pattern emerged about the relationships between biodiversity indicator and community richness, that is worth of further research. Our study demonstrates that the usefulness of surrogate species for biodiversity and community assessment can become clear only at a certain spatial scales. Indeed, they can be highly predictive of the whole community, and highly informative for conservation planning. Moreover, their use can optimize biodiversity monitoring and conservation, focusing on a small number of noteworthy species. 相似文献
102.
Vertical structure of Erica umbellata,a representative species of European Ibero-Atlantic dry heaths
The canopy structure of Erica umbellata was studied in order to (a) quantify biomass allocation among several organ types, (b) analyse the possible changes in vertical structure related to season and plant size, and (c) evaluate the effectiveness of non-destructive measures to estimate biomass for a species that is declining in some areas, due to fire and other human disturbances. The study was conducted in NW Spain, sampling E. umbellata plants belonging to three size groups. Destructive (biomass) and non-destructive (frequency, height, diameter) measures were used to characterise the vertical distribution and abundance of photosynthetic, woody, reproductive and dead organs. Allometric equations were calculated to estimate total mass using non-destructive measurements. As E. umbellata increases in size, those organs with a higher renewal rate (leaves, new stems, flowers) increase in the upper strata. Seasonal differences are recorded for the reproductive organs and new stems. A sharp decrease in the green/total phytomass ratio (from 0.51 to 0.17) is observed as plant size increases. Organ biomass can be accurately predicted from total weight and it is also possible to estimate the total weight from non-destructive measures, which provides an easier way of recording data in the field. 相似文献
103.
Landscape fragmentation is commonly defined as having five distinct phases (perforation, dissection, subdivision, shrinkage, and attrition). Previous studies focus on using landscape pattern metrics to interpret the phase of the landscape. A critical but underinvestigated aspect is that these five phases are also spatially explicit processes. This study proposes a new method to map and measure the different spatially explicit processes of landscape fragmentation. Unlike previous studies that are based on landscape pattern metrics, this current study measures landscape change directly. The new method is applied to Bao’an District in Shenzhen, China, to investigate forest land fragmentation under rapid urbanization. Landsat data were used to map the land use distributions from 1978 to 2009. Results show that different spatial processes occur simultaneously throughout the study area as well as in different study periods of forest fragmentation. Shrinkage was the dominant spatial process in the early period. In the later period, subdivision played a more important role, followed by attrition. Interestingly, urban land was not the leading land use that directly encroached on forest land, as many other studies have shown. Instead, forest land was first converted to orchard land, and orchard land was converted to urban land. The study contributes to Forman's general model of spatially explicit processes of landscape fragmentation and holds implications for urban planning policy and practice. The study concludes that the new method is effective in understanding and assessing forest land fragmentation, especially in the context of rapid urbanization. 相似文献
104.
Sensitivity of landscape metrics to selection of spatial scale (i.e., resolution or areal extent), land-use categories, and different landscapes has led to unreliable conclusions for practitioners of landscape analysis and modeling. Unlike previous studies that mostly considered such metrics and assessed the effect of each factor separately, our study focuses on the sensitivity of the correlation structure of different sets of landscape metrics as a whole under different situations via principal component analysis (PCA). We used the congruence coefficient (rc) to calculate the changes in factor structures under different situations. We used 16 class-level and 15 landscape-level metrics of 900 village-based and 150 town-based samples that were collected from three regions. Five cell sizes, two land-use classes, and two sets of land-use metrics were also considered. We did not control the cell sizes, sample extent, and different landscapes in the sensitivity analysis to study the interactive relationships between different factors. All factors strongly influence the correlation structure of the landscape metrics, with each factor demonstrating a unique influence. Changing cell size significantly affects the correlation structures in the plain region, especially in croplands and built-up lands. Town-based results show a relatively more stable correlation structure than village-based results (except in land-use categories). Different land-use classes show different responses to changing cell size, sample extent, and sets of landscape metrics in different regions. These results show the great interactive influences of these factors, which have often been overlooked in previous studies. The conclusions drawn from fixed factors may be conditional and inapplicable to other situations. The sensitivity of the correlation structure in diverse regions may improve our understanding of landscape metrics as a whole and can provide further insights into the correlation structure of landscape metrics for land-use management and monitoring. 相似文献
105.
The biological control service supplied to croplands is a result of the predator community present within a focal crop, which is likely influenced by surrounding landscape composition and configuration. In this study, using cage experiments in two regions near Santiago, we determined if predator communities supplied a significant biological control service in alfalfa fields, examined how the abundance of exotic and native coccinellids, as well as other key predator groups, influenced biological control of aphids and measured how landscape composition and heterogeneity at three spatial scales influenced this service. We found that predators significantly suppressed aphid populations in both regions, but the relative importance of predators versus landscape variables on biological control differed between regions. In the region where predators were abundant, biological control was higher and related to the abundance of native coccinellids and syrphids, highlighting the importance of native species as providers of crucial ecological services. In the region where predators were not abundant, biological control was lower, and it was related to landscape composition, being positively associated with the abundance of woodlots and urban habitats, and negatively associated with fruit crops in the landscape. Therefore, landscape effects on biological control service may be weaker than local factors, and only become important when local predator abundance is low. 相似文献
106.
In this study, an ecological vulnerability assessment indicator system was constructed using the “exposure–climate sensitivity–adaptive capacity” framework according to the theory of ecological vulnerability. An improved ecosystem service value calculation model was proposed based on empirical parameters. Using Yancheng Nature Reserve in China as an example, we employed remote sensing data to conduct an empirical analysis of the changes in the spatiotemporal pattern, ecological vulnerability, and ecosystem services of typical landscape types over the period from 1987 to 2013. The statistical results derived from landscape pattern indices (LPIs) showed that during the investigation period, three natural wetland landscape types (i.e., Spartina alterniflora, Suaeda glauca, and Phragmites australis) showed gradually increased fragmentation in the study area. The ecological vulnerability scores of the major landscape types (in descending order) were P. australis (0.053), farmland (0.047), S. alterniflora (0.042), S. glauca (0.031), and bare mud flat (0.002). The results derived from the ecosystem service value fluctuation index (ESVFI) showed that from 1987 to 1997, the value of the ecosystem services provided by S. glauca and P. australis wetlands decreased, whereas that of S. alterniflora wetlands increased continuously. From 2002 to 2013, the value of the ecosystem services provided by all three types of natural wetland showed a downward trend. In conclusion, the combined effects of human and natural factors, including the expansion of farmland and the invasion of S. alterniflora, and changes in seawater erosion and deposition led to changes in the landscape patterns, ecological vulnerability, and ecosystem services of the Yancheng Nature Reserve during the investigation period. The results indicate that a “dual adaptive” management system based on natural succession and supplemented by appropriate manual intervention should be implemented, and the management efficiency and flexibility should be improved to meet the common needs of biodiversity conservation and economic development. 相似文献
107.
Bryan D. Watts 《Oecologia》1996,108(3):512-517
Community-level studies with finches have traditionally viewed local resources as the primary constrainst on local diversity. Patches have been considered to be self-contained and embedded in landscapes that were neutral with respect to the ecological processes under investigation. This study uses a factorial design to examine the relative roles of patch content and patch context in determining patterns of species richness. Sparrows were surveyed in small fallow patches that varied in both weed cover and the type of adjacent habitat. Species richness and total sparrow abundance were significantly influenced by both factors. Individual species were also influnced by both factors; however, responses were species-specific. Because occupation of particular plot types was conditional on their association with specific habitat types, the spatial patterning of species assemblages results from the configuration of patch types within the landscape. 相似文献
108.
109.
Agricultural landscapes rich in natural and semi-natural habitats promote biodiversity and important ecosystem services for crops such as pest control. However, semi-natural habitats may fail to deliver these services if agricultural pests are disconnected from the available pool of natural enemies, as may be the case with invasive species. This study aimed to provide insights into the relationship between landscape complexity and the abundance of the recently established invasive pest species Drosophila suzukii and a group of natural enemies (parasitoid wasps), which contain species that parasitize D. suzukii in native and invaded ecosystems. The importance of landscape complexity was examined at two spatial scales. At the field scale, the response to introduction of wildflower strips was analysed, while the relationship with forest cover was assessed at the landscape scale. Half of the surveys were done next to blueberry crops (Vaccinium corymbosum), the other half was done in landscapes without fruit crops to examine effects of D. suzukii host presence. As expected, the number of observed parasitoid wasps increased with amount of forest surrounding the blueberry fields, but the number of D. suzukii individuals likewise increased with forest cover. Establishment of wildflower strips did not significantly affect the abundance of D. suzukii or parasitoid wasps and insect phenology was similar in landscapes with and without blueberry crops. This suggests that D. suzukii is enhanced by landscape complexity and is largely unlinked from the species group that, in its native range, hosts key natural enemies. Although management practices that rely on enhancing natural enemies through habitat manipulations can contribute to the long-term stability of agroecosystems and to control agricultural pests, other control measures may still be necessary in the short term to counteract the benefits obtained by D. suzukii from natural habitats. 相似文献
110.
The Three Rivers Headwaters Region is one of the most import ecological protection regions and Tibetan inhabited regions in China. Located in the Qinghai province of China, the Region is the source of the Yangtze, the Yellow and the Lantsang-Mekong Rivers. This study region was based on remote sensing imagery. An ecological landscape classification of the area is presented, as well as a suite of landscape indices for landscape pattern changes from 1987 to 2015. The influence of human activities on the landscape change of study area is discussed. The results showed landscape structure complexity, fragmentation gradually increased, while the indices of contagion and evenness were decreased. Structure characteristic of landscape change in this region are more obvious, especially, the difference in space distributions of part and the whole. There were trend of uniform distribution of different types and diversity gradually increased in the source of Yangtze River. And an opposite tendency is showing in the Yellow River and Lantsang-Mekong River. Physical-geographical conditions, climate change and government policy at study period were the main reasons of significant landscape pattern change. This study proposes management measures for sustainable development in the Three Rivers Headwaters Region. 相似文献