Improving the Urban Stream Restoration Effort: Identifying Critical Form and Processes Relationships

Stream restoration projects are often based on morphological form or stream type and, as a result, there needs to be a clear tie established between form and function of the stream. An examination of the literature identifies numerous relationships in naturally forming streams that link morphologic form and stream processes. Urban stream restoration designs often work around infrastructure and incorporate bank stabilization and grade control structures. Because of these imposed constraints and highly altered hydrologic and sediment discharge regimens, the design of urban channel projects is rather unclear. In this paper, we examine the state of the art in relationships between form and processes, the strengths and weaknesses of these existing relationships, and the current lack of understanding in applying these relationships in the urban environment. In particular, we identify relationships that are critical to urban stream restoration projects and provide recommendations for future research into how this information can be used to improve urban stream restoration design. It is also suggested that improving the success of urban restoration projects requires further investigation into incorporating process-based methodologies, which can potentially reduce ambiguity in the design and the necessity of using an abundant amount of in-stream structures.     

Hot Spots of Perforated Forest in the Eastern United States

National assessments of forest fragmentation satisfy international biodiversity conventions, but they do not identify specific places where ecological impacts are likely. In this article, we identify geographic concentrations (hot spots) of forest located near holes in otherwise intact forest canopies (perforated forest) in the eastern United States, and we describe the proximate causes in terms of the nonforest land-cover types contained in those hot spots. Perforated forest, defined as a 0.09-ha unit of forest that is located at the center of a 7.29-ha neighborhood containing 60–99% forest with relatively low connectivity, was mapped over the eastern United States by using land-cover maps with roads superimposed. Statistically significant (P < 0.001) hot spots of high perforation rate (perforated area per unit area of forest) were then located by using a spatial scan statistic. Hot spots were widely distributed and covered 20.4% of the total area of the 10 ecological provinces examined, but 50.1% of the total hot-spot area was concentrated in only two provinces. In the central part of the study area, more than 90% of the forest edge in hot spots was attributed to anthropogenic land-cover types, whereas in the northern and southern parts it was more often associated with seminatural land cover such as herbaceous wetlands.     

Systematic Temporal Patterns in the Relationship Between Housing Development and Forest Bird Biodiversity

As people encroach increasingly on natural areas, one question is how this affects avian biodiversity. The answer to this is partly scale‐dependent. At broad scales, human populations and biodiversity concentrate in the same areas and are positively associated, but at local scales people and biodiversity are negatively associated with biodiversity. We investigated whether there is also a systematic temporal trend in the relationship between bird biodiversity and housing development. We used linear regression to examine associations between forest bird species richness and housing growth in the conterminous United States over 30 years. Our data sources were the North American Breeding Bird Survey and the 2000 decennial U.S. Census. In the 9 largest forested ecoregions, housing density increased continually over time. Across the conterminous United States, the association between bird species richness and housing density was positive for virtually all guilds except ground nesting birds. We found a systematic trajectory of declining bird species richness as housing increased through time. In more recently developed ecoregions, where housing density was still low, the association with bird species richness was neutral or positive. In ecoregions that were developed earlier and where housing density was highest, the association of housing density with bird species richness for most guilds was negative and grew stronger with advancing decades. We propose that in general the relationship between human settlement and biodiversity over time unfolds as a 2‐phase process. The first phase is apparently innocuous; associations are positive due to coincidence of low‐density housing with high biodiversity. The second phase is highly detrimental to biodiversity, and increases in housing density are associated with biodiversity losses. The long‐term effect on biodiversity depends on the final housing density. This general pattern can help unify our understanding of the relationship of human encroachment and biodiversity response. Patrones Sistemáticos Temporales en la Relación entre Desarrollos Urbanos y la Biodiversidad de Aves de Bosque     

Climate change,risk perception,and protection motivation among high-altitude residents of the Mt. Everest region in Nepal

Mountain ecosystems are considered vulnerable to early impacts of climate change. Whether and how local residents of these areas perceive these changes, however, remain under-studied questions. By conducting a household survey in the Khumbu region of Nepal, this study assessed local residents’ experience-based perception of changes in climate trends and patterns, perceived risk, and attitudes towards climate issues. Multivariate cluster analysis based on residents’ climate change beliefs revealed three segments: “Cautious,” “Disengaged,” and “Alarmed.” A comparison of these segments along key psychosocial constructs of Protection Motivation Theory (PMT) revealed significant inter-segment differences in residents’ perception of severity, vulnerability, response efficacy, self-efficacy, and response cost associated with engaging in mitigating behavior. Results shed light on how residents of high elevation areas that are considered to be exposed to early impacts of climate change perceive the risk and intend to respond. These findings could also assist stakeholders working in other similar mountain ecosystems in understanding vulnerability and in working towards climate readiness.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01369-x) contains supplementary material, which is available to authorized users.     

流态对生物添加强化硝化效果的影响

在15℃、相同氮负荷和添加强度条件下运行SBR和CSTR以对比分析两种典型流态(推流式和完全混合式)对硝化菌添加强化硝化效果的影响.结果表明,添加期间,SBR中氨氧化速率(AUR)和亚硝酸盐氧化速率(NUR)分别为添加前的2.34和2.39倍,停止添加后又分别降为添加前的2.01和1.78倍;添加期间CSTR中AUR和NUR分别为添加前的2.63和2.44倍,停止添加后又分别降为添加前的1.48和1.31倍.荧光原位杂交结果显示,添加期间,SBR中氨氧化菌(AOB)和亚硝酸盐氧化菌(NOB)的个数百分比分别为添加前的2.67和2.71倍,添加停止后,又分别降至原来的2.14和1.95倍;CSTR中AOB和NOB分别为添加前的2.91和1.77倍,但在添加停止后CSTR中AOB和NOB分别降至添加前的1.25和1.50倍.因此,硝化菌添加期间,两种流态的添加效果接近,但是在添加停止后,由于流态对硝化菌中K-决策者(Nitrosospira、Nitrospira)和r-决策者(Nitrosomonas europaea、Nitrobacter)的选择作用,添加的硝化菌在完全混合式条件下比推流式条件下更容易被系统淘汰.     

福建省地级市人为源活性氮排放及其特征分析

在人口增长和快速城市化的背景下,活性氮排放对生态环境的影响日益加剧.为研究省级尺度活性氮排放规律,采用排放因子法建立2000、2005及2010年福建省人为源活性氮排放清单,分析各地市3个年份活性氮排放量及排放强度特征.结果表明,3个年份福建省活性氮排放总量分别为538.4、587.0和619.97 Gg,呈整体增加趋势.在9个地级市中,增速最快的为莆田市,而漳州市排放量有所下降.排放量最大的为漳州和泉州,排放量最小的为宁德与厦门.从排放来源看,90%以上的排放来自农田生态系统和畜禽养殖系统.能源活动贡献较小,但其排放增长最为显著.2010年,各地市单位面积活性氮排放强度呈"东南沿海高西北内陆低"的格局,最高为厦门市,最低为三明市;GDP和人口排放强度则呈"东南沿海低西北内陆高"的格局,最高为南平市,最低为厦门市.在分析各地市活性氮排放源特征的基础上,探讨了不同地区活性氮减排重点,研究结果可为福建省及下辖各地市活性氮减排提供科学依据.     

电晕放电辐射信号的特征提取和模式识别方法研究

目的研究电晕放电辐射信号的特征提取和模式识别方法。方法在分析信号特征提取方法的基础上,对实测的电晕放电辐射信号特征提取,利用概率神经网络开展电晕放电辐射信号目标识别,检验特征提取的有效性。结果以奇异值作为输入特征量的PNN在整体上效果更优,稳定性好,对两类不同放电辐射信号的正确识别率均可达到80%以上,并且当输入特征量个数达到10个时,对实测样本的正确识别率均达到了最高值。电晕放电的正确识别率为96.7%,火花放电的正确识别率为93.3%。结论该方法能基本满足实际放电信号的识别应用。     

城市建筑周边绿地景观格局优化方法研究

现有绿地景观格局优化方法,存在梯度变化不规律、边缘斑块密度不均等缺陷.针对该问题,提出基于窗口移动法的新型城市建筑周边绿地景观格局优化方法,通过确定研究区域与数据来源,以边缘斑块密度、梯度、绿地景观格局化指数为绿地景观格局化指数,确立研究方法.模拟研究环境设计实验结果表明,采用改进格局优化方法可改善城市建筑周边绿地景观格局梯度变化不规律问题;在特定空间分布状态下,还可避免边缘斑块密度不均的现象发生.     

省级生态保护红线划定实践研究 ——以青岛市为例

在省级及以上禁止开发区、重点生态功能保护区等进行调查分析的基础上,以青岛市为实践区域,与多类规划衔接,划定青岛市省级生态保护红线.青岛市最终划定59处省级生态保护红线区,面积合计1120.65 km2,占国土面积的9.9%.划定的生态保护红线符合确立"三生"空间和落实"多规合一"的要求,有利于改善生态系统服务功能,保障人居环境安全,增强经济社会可持续发展能力,对于青岛市市级生态保护红线的划定和生态安全格局的构建具有非常重要的意义.     

黄土丘陵区坡面水蚀对降雨和下垫面微观格局的响应

黄土高原严重的土壤侵蚀是降雨和复杂脆弱的下垫面共同作用的结果.以微型小区尺度上(1.2 m×1.2 m;2 m×1.2m)模拟降雨技术为基本研究手段,定量刻画了降雨量和降雨强度等基本降雨特征值对定西安家沟自然坡面上荒草、沙棘中位、沙棘下位、沙棘上位、结皮裸地和裸地等不同植株微观格局及其处理下的水蚀过程的影响.主要取得以下结果:①雨强和雨量对水蚀的发生均能产生显著影响,但以雨强的影响力更大;②前期土壤含水量与产流时间显著负相关,而与径流量和侵蚀量显著正相关.前期含水量相同时,不同植株微景观格局对产流时间发挥了关键作用;③不同植株及其微观格局遏制地表径流的能力迥异.在50～60 mm.h-1的大雨强作用下,有沙棘覆盖的小区径流系数仅为5%～8%,荒草地为25%,结皮裸地为45%,而裸地则高达63%;④有沙棘覆盖的小区中,沙棘在小区中所处的具体位置对于水土流失效应又极为重要,以沙棘下位的水土保持效果最好.