Abstract
Urban green space is an important refuge of biodiversity in urban areas. Therefore, it is crucial to understand the relationship between the landscape pattern of green spaces and biodiversity to mitigate the negative effects of urbanization. In this study, we collected insects from 45 green patches in Beijing during July 2012 using suction sampling. The green patches were dominated by managed lawns, mixed with scattered trees and shrubs. We examined the effects of landscape pattern on insect species density using hierarchical partitioning analysis and partial least squares regression. The results of the hierarchical partitioning analysis indicated that five explanatory variables, i.e., patch area (with 19.9% independent effects), connectivity (13.9%), distance to nearest patch (13.8%), diversity for patch types (11.0%), and patch shape (8.3%), significantly contributed to insect species density. With the partial least squares regression model, we found species density was negatively related to patch area, shape, connectivity, diversity for patch types and proportion of impervious surface at the significance level of p < 0.05 and positively related to proportion of vegetated land. Regression tree analysis further showed that the highest species density was found in green patches with an area <500 m2. Our results indicated that improvement in habitat quality, such as patch area and connectivity that are typically thought to be important for conservation, did not actually increase species density. However, increasing compactness (low-edge) of patch shape and landscape composition did have the expected effect. Therefore, it is recommended that the composition of the surrounding landscape should be considered simultaneously with planned improvements in local habitat quality.
Highlights
Rapid urbanization is generally considered to be one of the main drivers of biodiversity loss, resulting in major local extinctions, decreases in native species diversity, changes in species composition and outbreaks of individual species [1, 2]
hierarchical partitioning (HP) for species density revealed that LogArea, SqrtConn_ 5m (13.9%), ENN_MN (13.8%), Shannon’s diversity index (SHDI) (11.0%) and SHAPE_AM (8.3%) made a significant independent contribution to the variance, as explained by the full model (Z-scores ! 1.65) (Fig. 2)
It was an unexpected result that insect species density was negatively correlated with patch area in the partial least squares regression (PLSR) model, i.e., species density decreased as patch area increased
Summary
Rapid urbanization is generally considered to be one of the main drivers of biodiversity loss, resulting in major local extinctions, decreases in native species diversity, changes in species composition and outbreaks of individual species [1, 2]. Effects of Urban Landscape Pattern on Insect Species Density isolation [6] and landscape heterogenization [7] are major factors in decreasing species richness. The relative importance of different landscape factors is the subject of debate. Given that these factors are often interdependent, it is necessary to disentangle the role of different environmental pressures on biodiversity to develop strategies to mitigate the potential detrimental impacts of urbanization
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