Marine reserves,fisheries ban,and 20 years of positive change in a coral reef ecosystem

By 2004, Belize was exhibiting classic fishing down of the food web. Groupers (Serranidae) and snappers (Lutjanidae) were scarce and fisheries turned to parrotfishes (Scarinae), leading to a 41% decline in their biomass. Several policies were enacted in 2009–2010, including a moratorium on fishing parrotfish and a new marine park with no-take areas. Using a 20-year time series on reef fish and benthos, we evaluated the impact of these policies approximately 10 years after their implementation. Establishment of the Southwater Caye Marine Reserve led to a recovery of snapper at 2 out of 3 sites, but there was no evidence of recovery outside the reserve. Snapper populations in an older reserve continued to increase, implying that at least 9 years is required for their recovery. Despite concerns over the feasibility of banning parrotfish harvest once it has become a dominant fin fishery, parrotfishes returned and exceeded biomass levels prior to the fishery. The majority of these changes involved an increase in parrotfish density; species composition and adult body size generally exhibited little change. Recovery occurred equally well in reserves and areas open to other forms of fishing, implying strong compliance. Temporal trends in parrotfish grazing intensity were strongly negatively associated with the cover of macroalgae, which by 2018 had fallen to the lowest levels observed since measurements began in 1998. Coral populations remained resilient and continued to exhibit periods of net recovery after disturbance. We found that a moratorium on parrotfish harvesting is feasible and appears to help constrain macroalgae, which can otherwise impede coral resilience.     

Effects of anthropogenic disturbance on primate density at the landscape scale

Accurate estimations of the abundance of threatened animal populations are required for assessment of species’ status and vulnerability and conservation planning. However, density estimation is usually difficult and resource demanding, so researchers often collect data at local scales. However, anthropogenic pressures most often have landscape-level effects, for example, through habitat loss and fragmentation. We applied hierarchical distance sampling (HDS) to transect count data to determine the effect of habitat and anthropogenic factors on the density of 3 arboreal primate species inhabiting 5 distinct tropical forests across a landscape of 19,000 km² in the Udzungwa Mountains of Tanzania. We developed a novel, multiregion extension of HDS that allowed us to model density and detectability jointly across forests without losing site-specific information. For all species, the effect of anthropogenic disturbance on density was overwhelmingly negative among metapopulations: −0.63 Angolan colobus (Colobus angolensis palliatus) (95% Bayesian CI −1.03 to −0.27), −0.54 Udzungwa red colobus (Procolobus gordonorum) (−0.89 to −0.22), and −0.33 Sykes' monkey (Cercopithecus mitis monoides) (−0.63 to −0.07). Some responses to habitat factors were shared, notably the negative effect of elevation and the positive effect of climber coverage. These results are important for conservation science and practice because: the among-populations negative responses to anthropogenic disturbance provides a foundation for development of conservation plans that hold at the landscape scale, which is a comprehensive and cost-efficient approach; the among-species consistency in responses suggests conservation measures may be generalized at the guild level, which is especially relevant given the functional importance of primates in tropical rainforests; and the greater primate densities in areas at low elevation, which are closer to human settlements, point to specific management recommendations, such as the creation of buffer zones and prioritization of areas for protection.     

Nonadditive effects among threats on rare plant species

The current loss of biodiversity has put 50,000 plant species at an elevated risk of extinction worldwide. Conserving at-risk species is often complicated by covariance or nonadditivity among threats, which makes it difficult to determine optimal management strategies. We sought to demographically quantify covariance and nonadditive effects of more threats on more rare plant species than ever attempted in a single analysis. We used 1082 population reports from 186 populations across 3 U.S. states of 27 rare, herbaceous plant species collected over 15 years by citizen scientists. We used a linear mixed-effects model with 4 threats and their interactions as fixed predictors, species as a random predictor, and annual growth rates as the response. We found a significant 3-way interaction on annual growth rates; rare plant population sizes were reduced by 46% during the time immediately after disturbance when populations were also browsed by deer (Odocoileus virginianus) and had high levels of encroachment by woody species. This nonadditive effect should be considered a major threat to the persistence of rare plant species. Our results highlight the need for comprehensive, multithreat assessments to determine optimal conservation actions.     

Critical factors for the recovery of marine mammals

{en} Over the past decades, much research has focused on understanding the critical factors for marine extinctions with the aim of preventing further species losses in the oceans. Although conservation and management strategies are enabling several species and populations to recover, others remain at low abundance levels or continue to decline. To understand these discrepancies, we used a published database on abundance trends of 137 populations of marine mammals worldwide and compiled data on 28 potentially critical factors for recovery. We then applied random forests and additive mixed models to determine which intrinsic and extrinsic factors are critical for the recovery of marine mammals. A mix of life‐history characteristics, ecological traits, phylogenetic relatedness, population size, geographic range, human impacts, and management efforts explained why populations recovered or not. Consistently, species with lower age at maturity and intermediate habitat area were more likely to recover, which is consistent with life‐history and ecological theory. Body size, trophic level, social interactions, dominant habitat, ocean basin, and habitat disturbance also explained some differences in recovery patterns. Overall, a variety of intrinsic and extrinsic factors were important for species’ recovery, pointing to cumulative effects. Our results provide insight for improving conservation and management strategies to enhance recoveries in the future.     

高速公路动荷载对塌陷区的扰动分析

随着煤矿塌陷区的不断增多和高速公路的高速建设,高速公路不可避免的穿越塌陷区。通过分析高速公路与塌陷区的空间形态,提出将塌陷区上新增的路基材料作为静荷载,将行驶的车辆视为沿正弦曲线运动的动荷载作用在塌陷区上。根据荷载大小分析荷载对采空区上方岩体的扰动深度,通过实例分别计算得出考虑车辆附加动荷载和只考虑车辆自重的高速公路对岩体的扰动深度,两者有一定的差异。在实际工程应用中,应考虑车辆的附加动荷载,以及高速公路对采空区的扰动深度是否影响到上覆岩层冒落裂缝带等因素,对保证高速公路的后期稳定性具有重要意义。     

Effects of Controlled Fire and Livestock Grazing on Bird Communities in East African Savannas

Abstract: In East Africa fire and grazing by wild and domestic ungulates maintain savannas, and pastoralists historically set fires and herded livestock through the use of temporary corrals called bomas. In recent decades traditional pastoral practices have declined, and this may be affecting biodiversity. We investigated the effects of prescribed fires and bomas on savanna bird communities in East Africa during the first and second dry seasons of the year (respectively before and after the rains that mark the onset of breeding for most birds). We compared abundance, richness, and community composition on 9‐ha burned plots, recently abandoned bomas, and control plots in the undisturbed matrix habitat over a 3‐year period. Generally, recently burned areas and abandoned bomas attracted greater densities of birds and had different community assemblages than the surrounding matrix. The effects of disturbances were influenced by interactions between primary productivity, represented by the normalized difference vegetation index, and time. Bird densities were highest and a greater proportion of species was observed on burned plots in the months following the fires. Drought conditions equalized bird densities across treatments within 1 year, and individuals from a greater proportion of species were more commonly observed on abandoned bomas. Yearly fluctuations in abundance were less pronounced on bomas than on burns, which indicate that although fire may benefit birds in the short term, bomas may have a more‐lasting positive effect and provide resources during droughts. Several Palearctic migrants were attracted to burned plots regardless of rainfall, which indicates continued fire suppression may threaten their already‐declining populations. Most notably, the paucity of birds observed on the controls suggests that the current structure of the matrix developed as a result of fire suppression. Traditional pastoralism appears critical to the maintenance of avian diversity in these savannas.     

电源适配器输出端口骚扰电压测量方法

电源适配器的直流输出端口骚扰电压过高会造成笔记本计算机电信端口传导骚扰电压测试不合格,但是标准中缺乏直流输出端口骚扰电压的测量方法。设计了一种电源适配器直流输出端口传导骚扰电压测量方法,在不需要配置笔记本计算机的环境下使用电源适配器单体模拟电信端口测试,其测量结果可以用于预测电源适配器在笔记本电脑电信端口产生的共模传导骚扰电压。经实际实验结果,用此方法测得的直流输出端口骚扰电压谱线与搭配笔记本计算机后的电信端口骚扰谱线有很好的对应性。     

高速动车组车内低频电磁场测试及分布特性分析

近年来我国高速铁路建设飞速发展,在给交通运输带来了方便快捷的同时,也引入了电磁干扰问题。本文以高速动车组车内低频电磁环境为对象,分析了高速铁路电磁骚扰源及列车产生电磁骚扰的机理,通过对大量实测数据的统计和总结,分析了高速动车组车内低频电磁场的分布和规律,并对我国高速动车组车内低频电磁环境的优化提出一些看法和建议。     

CDN辐射骚扰测试影响因素的探究

研究影响CISPR15中辐射骚扰测试项目所用的电波暗室测试法的替代方法（CDN法）的测试因素。通过在不同的测试环境、不同的布置下对比测试,得到了不同的测试结果,从而加深了对标准布置的理解,也为实验室间比对测试提供了参考。     

玉龙雪山牦牛坪高山草甸的干扰格局分析

近几年玉龙雪山生态旅游热升温,对该区域生态环境和植被资源的影响日趋显著,研究该区域高山草甸所受干扰对制定该区域的生态保护、可持续发展对策具有重要意义。为明晰人类活动对玉龙雪山高山草甸的影响,选取该区域典型高山草甸分布区域作为研究区,分析其草甸退化格局,通过干扰强度模型量化研究区的干扰格局,并利用方差分解确定不同干扰对高山草甸退化的贡献率。结果表明：（1）放牧干扰主要集中在牲畜饮水点附近,旅游干扰更多作用于景区观景台和寺庙附近,干扰活动分布与路径体系相吻合,游径布设和游客行为扩散模式决定了旅游干扰的格局;（2）草甸退化程度随干扰程度的增加而升高,干扰强度最大的区域与草甸的重度退化区域重合;（3）总体上旅游较放牧对草甸退化的贡献作用更大,但存在空间差异。在玉龙雪山牦牛坪景区,旅游干扰已逐渐取代放牧干扰成为主要干扰因素,且路径体系与旅游干扰格局具有较高的吻合度,对草甸退化格局的影响在逐渐增加。综上,建议选取使用率高的非正式路径修建为正式路径,保护和恢复分布在使用率低的非正式路径旁的植被和土壤,以降低旅游干扰对高山草甸的影响。