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21.
Susanna Lehvävirta D. Johan Kotze Jari Niemelä Meri Mäntysaari Bob O'Hara 《Urban Ecosystems》2006,9(1):13-26
We studied the effects of fragmentation (edge effects and patch size) and trampling (path cover) on carabid beetle assemblages
in urban woodland patches in Helsinki, Finland. We expected that (1) open habitat and generalist species would benefit and
forest species would suffer from increased woodland fragmentation, and (2) most carabid species would respond negatively to
increased levels of trampling. A total of 2088 carabid individuals representing 37 species were collected. A cluster analysis
distinguished sites in the interior of large woodland patches, with low or moderate path cover, from the other sites. The
other sites did not cluster meaningfully, suggesting increased variation in the carabid fauna with increasing human impact.
All species and ecological species-groups decreased with increasing distance from the edge toward the woodland interior and
with increasing patch size. This pattern is in accordance with our expectation for open habitat and generalist species but
opposite to what we expected for forest species. The reason for these surprising results may be that (1) the species we collected
are not true forest interior species, (2) urban woodland edges are optimal habitats for many forest carabids, or (3) edges
are actually sub-optimal, and high catches simply reflect increased activity of beetles moving away from the edge. Trampling
did not have an overall negative effect on carabids as hypothesized. Species associated with moist forest habitat responded
as predicted: they decreased in abundance with increasing path cover. Furthermore, open habitat species decreased with increasing
path cover but more straightforward than we had predicted. Model elaboration, by dropping the highly trampled sites from the
analyses, suggested that our data of high trampling may be too scarce: the results without these sites were more in accordance
with our predictions than with the full dataset. 相似文献
22.
Wenxin Zhang Liang Chen Fengjie Yu Shuqiong Wang Jari‐Erik Nurmi 《Journal of research on adolescence》2015,25(4):622-629
This study examined the contents of adolescents' hopes and fears for the future in a sample of 1,975 urban and rural 8th, 10th, and 12th graders in China. Chinese adolescents' hopes and fears were most often related to future education, occupation, parental well‐being, marriage and family, academics, leisure activities, wealth, interpersonal relationships, collective issues, and self‐related issues. Urban adolescents compared to rural ones reported more hopes for education and leisure activities and held fewer hopes and fears for parental well‐being and interpersonal relationships. Males reported more hopes and fears for marriage, whereas females reported more hopes and fears for parental well‐being. These results suggest the important role of the social and cultural context in adolescents' future thinking. 相似文献
23.
Time‐to‐event data have been extensively studied in many areas. Although multiple time scales are often observed, commonly used methods are based on a single time scale. Analysing time‐to‐event data on two time scales can offer a more extensive insight into the phenomenon. We introduce a non‐parametric Bayesian intensity model to analyse two‐dimensional point process on Lexis diagrams. After a simple discretization of the two‐dimensional process, we model the intensity by a one‐dimensional piecewise constant hazard functions parametrized by the change points and corresponding hazard levels. Our prior distribution incorporates a built‐in smoothing feature in two dimensions. We implement posterior simulation using the reversible jump Metropolis–Hastings algorithm and demonstrate the applicability of the method using both simulated and empirical survival data. Our approach outperforms commonly applied models by borrowing strength in two dimensions. 相似文献