To maximize the ecological services of urban forests, a better understanding of the effects of urbanization on urban forest characteristics, landscape metrics, and their associations is needed for landscape-related regulations in space-limited green infrastructure of metropolitan regions. In this study, Harbin, a typical fast-growing provincial-capital city in Northeast China, is used as a case study. Based on remote sensing images, field surveys, and correlation and variation partitioning analyses, we conclude that landscape characteristics and forest attributes have large variations among different urbanization intensity (UI) regions. Forest patch density (PD), landscape shape index, woody plants species richness, and the Shannon–Wiener index (H′) increased linearly, while stem section area and tree height decreased linearly with the increasing of UIs. UI had a greater influence on tree size and forest community attributes than the forest landscape pattern. Accordingly, any landscape regulation on forest attributes should be implemented according to UIs. In addition, Euclidean nearest neighbor distance(ENN-MN), mean perimeter-area ratio (PARA-MN), fractal dimension index(FRAC-MN), and PD could probably indicate forest attributes the most, e.g., the increase of PARA-MN may be accompanied with taller trees in low and heavy UI regions, but lower woody plants species evenness in low and medium UI regions. More diversified woody plants species, and afforested areas should be advocated in a low UI region, while in a heavy UI region, the conservation of large trees should be implemented. Our results highlight that the implementation of urban forest management should vary according to different urbanization regions to maximize ecological services.
This paper examines a game‐theoretic model of attack and defense of multiple networks of targets in which there exist intranetwork strategic complementarities among targets. The defender's objective is to successfully defend all the networks and the attacker's objective is to successfully attack at least one network of targets. Although there are multiple equilibria, we characterize correlation structures in the allocations of forces across targets that arise in all equilibria. For example, in all equilibria the attacker utilizes a stochastic “guerrilla warfare” strategy in which a single random network is attacked. (JEL C72, D74) 相似文献
Impacts of urbanization on biodiversity are commonly studied using urbanization gradients which provide a space-for-time substitution in estimating consequences of urban expansion. Rates of urbanization and human population growth are high in tropical countries of the developing world, which also hold most of the world’s biodiversity hot-spots, yet few studies have considered biodiversity trends along urban gradients in these regions. Bird communities across a gradient of nine sites in Uganda, from the city centre of Kampala to outlying rural locations, were studied over a six year period. These sites were ordered along an urbanization gradient using Principle Components Analysis based on habitat variables estimated at each site. Bird species richness showed a decrease from rural to urban sites, a trend especially evident in forest birds. There was no clear pattern in total abundance, total biomass or biomass per individual along the gradient. However, this latter result was heavily influenced by a colony of Marabou Storks at one site. When this species was omitted, there was evidence of a positive trend with urbanization, showing that as species richness decreased, the bird community was increasingly dominated by larger species with increasing urbanization, which were mainly scavengers able to exploit human refuse. These results provide further support for the negative impacts of urbanization on species richness, but also demonstrate trends in abundance and biomass are variable across different regions. In particular, the increasing dominance of larger species in urban areas may be relevant to certain geographic and/or socioeconomic contexts. 相似文献
We examine inferences about old-age mortality that arise when researchers use survey data matched to death records. We show that even small rates of failure to match respondents can lead to substantial bias in the measurement of mortality rates at older ages. This type of measurement error is consequential for three strands in the demographic literature: (1) the deceleration in mortality rates at old ages; (2) the black-white mortality crossover; and (3) the relatively low rate of old-age mortality among Hispanics, often called the “Hispanic paradox.” Using the National Longitudinal Survey of Older Men matched to death records in both the U.S. Vital Statistics system and the Social Security Death Index, we demonstrate that even small rates of missing mortality matching plausibly lead to an appearance of mortality deceleration when none exists and can generate a spurious black-white mortality crossover. We confirm these findings using data from the National Health Interview Survey matched to the U.S. Vital Statistics system, a data set known as the “gold standard” (Cowper et al. 2002) for estimating age-specific mortality. Moreover, with these data, we show that the Hispanic paradox is also plausibly explained by a similar undercount. 相似文献
Rates of medical interventions in childbirth have greatly increased in the Western world.
Background
Women’s attitudes affect their birth choices.
Aim
To assess women’s attitudes towards the medicalization of childbirth and their associations with women’s background as well as their fear of birth and planned and unplanned modes of birth.
Methods
This longitudinal observational study included 836 parous woman recruited at women’s health centres and natural birth communities in Israel. All women filled in questionnaires about attitudes towards the medicalization of childbirth, fear of birth, and planned birth choices. Women at <28 weeks gestation when filling in the questionnaire were asked to fill in a second one at ~34 weeks. Phone follow-up was conducted ~6 weeks postpartum to assess actual mode of birth.
Findings
Attitudes towards medicalization were more positive among younger and less educated women, those who emigrated from the former Soviet Union, and those with a more complicated obstetric background. Baseline attitudes did not differ by parity yet became less positive throughout pregnancy only for primiparae. More positive attitudes were related to greater fear of birth. The attitudes were significantly associated with planned birth choices and predicted emergency caesareans and instrumental births.
Discussion
Women form attitudes towards the medicalization of childbirth which may still be open to change during the first pregnancy. More favourable attitudes are related to more medical modes of birth, planned and unplanned.
Conclusion
Understanding women’s views of childbirth medicalization may be key to understanding their choices and how they affect labour and birth. 相似文献