北京河流底栖硅藻沿城乡梯度带空间分布及其季节变化

研究了北京市区沿城乡梯度带河流底栖硅藻的空间分布及其季节变化特征。通过在2014年的春季、夏季和秋季在山区对照溪流、城市上游河道和城市下游河道3个样区,共23个样点进行了底栖硅藻样品采集。分析表明,主要优势种的空间差异明显。在对照溪流,主要优势种为极小曲丝藻(Achnanthidium minutissimum);在城市上游河道,主要优势种分别为短文假十字脆杆藻(Pseudostaurosira brevistriata)和连结十字脆杆藻腹面变种(Staurosira construens var.venter);在城市下游河道,主要优势种为谷皮菱形藻(Nitzschia palea)。然而,3个样区内的主要优势种相对丰度季节变化较小(P0.05)。其中,A.minutissimum及P.brevistriata的季节变化特征均为春季秋季夏季,而S.construens var.venter及N.palea的季节变化特征均为春季夏季秋季。结果发现,北京市城乡梯度带的河流硅藻种类组成差异较大,但主要优势属种季节变化相对较小,表明硅藻种类能较好地反映城乡梯度带的河流环境变化状况,可用于北京市河流水质生物监测。     

基于元胞自动机的城市空间动态模拟

城市空间动态的模拟与预测可以为城市可持续发展规划与管理提供重要的参考依据。SLEUTH元胞自动机模型在城市空间模拟中较强的适用性和可移植性,该模型通过对历史数据的蒙特卡洛迭代自动寻找城市增长误差最小的参数组合,解决了传统元胞自动机模型中转换规则不易确定的问题。以武汉市为研究案例,运用SLEUTH模型进行了城市空间动态模拟与情景预测。2007年至2011年的城市空间模拟结果显示,模拟结果与实际历史数据可以获得良好的空间匹配度,Lee-Sallee形状指数均在0.6以上,显示SLEUTH元胞自动机模型经过本地化校正后具有较强的适用性和满意的模拟精度。进而,设置了现状趋势、基本保护、严格保护等3种情景对武汉2025年城市空间动态进行了预测,结果显示,各情景模式下城市居住用地均明显增长,农业用地、林地、水域等均有所减少;现状趋势情景和基本保护情景下农田、林地、水域减少的幅度较大,会加剧区域的生境破碎、耕地功能下降、水资源匮乏、湖滨湿地萎缩等生态问题,说明这两种情景不能有效满足城市生态系统健康和可持续发展的需要。严格保护情景下,城市居住用地扩张的程度得到了明显的控制,水域和林地得到了有效的保护,对于重要的自然生态系统组分保护及其服务能力维持可以起到显著作用。     

The heat is on: Genetic adaptation to urbanization mediated by thermal tolerance and body size

Worldwide, urbanization leads to tremendous anthropogenic environmental alterations, causing strong selection pressures on populations of animals and plants. Although a key feature of urban areas is their higher temperature (“urban heat islands”), adaptive thermal evolution in organisms inhabiting urban areas has rarely been studied. We tested for evolution of a higher heat tolerance (CT_MAX) in urban populations of the water flea Daphnia magna, a keystone grazer in freshwater ecosystems, by carrying out a common garden experiment at two temperatures (20°C and 24°C) with genotypes of 13 natural populations ordered along a well‐defined urbanization gradient. We also assessed body size and haemoglobin concentration to identify underlying physiological drivers of responses in CT_MAX. We found a higher CT_MAX in animals isolated from urban compared to rural habitats and in animals reared at higher temperatures. We also observed substantial genetic variation in thermal tolerance within populations. Overall, smaller animals were more heat tolerant. While urban animals mature at smaller size, the effect of urbanization on thermal tolerance is only in part caused by reductions in body size. Although urban Daphnia contained higher concentrations of haemoglobin, this did not contribute to their higher CT_MAX. Our results provide evidence of adaptive thermal evolution to urbanization in the water flea Daphnia. In addition, our results show both evolutionary potential and adaptive plasticity in rural as well as urban Daphnia populations, facilitating responses to warming. Given the important ecological role of Daphnia in ponds and lakes, these adaptive responses likely impact food web dynamics, top‐down control of algae, water quality, and the socio‐economic value of urban ponds.     

A comparison of the accuracy and precision of several open-water oxygen productivity techniques

Several methods for the estimation of the reaeration coefficient were compared by determining the ability of the methods to recover the correct K value from a computer-simulated stream oxygen record affected by a variety of non-ideal conditions. Noisy data and long observation intervals were not a serious problem for most methods. Saturating photosynthesis, fluctuating light intensity, afternoon depression and temperature variation caused failures by some methods but were well handled by others. Serious impairment of all methods occurred with low productivity or high K. In general, the best-performing methods were the modified hysteresis, nighttime regression, daytime regression, Odum and Hornberger-Kelly daytime methods.     

Using spatially explicit commodity flow and truck activity data to map urban material flows

To analyze and promote resource efficiency in urban areas, it is important to characterize urban metabolism and particularly, material flows. Material flow analysis (MFA) offers a means to capture the dynamism of cities and their activities. Urban‐scale MFAs have been conducted in many cities, usually employing variants of the Eurostat methodology. However, current methodologies generally reduce the study area into a “black box,” masking details of the complex processes within the city's metabolism. Therefore, besides the aggregated stocks and flows of materials, the movement of materials—often embedded in goods or commodities—should also be highlighted. Understanding the movement and dispersion of goods and commodities can allow for more detailed analysis of material flows. We highlight the potential benefits of using high‐resolution urban commodity flows in the context of understanding material resource use and opportunities for conservation. Through the use of geographic information systems and visualizations, we analyze two spatially explicit datasets: (1) commodity flow data in the United States, and (2) Global Positioning System‐based commercial vehicle (truck) driver activity data in Singapore. In the age of “big data,” we bring advancements in freight data collection to the field of urban metabolism, uncovering the secondary sourcing of materials that would otherwise have been masked in typical MFA studies. This brings us closer to a consumption‐based, finer‐resolution approach to MFA, which more effectively captures human activities and its impact on urban environments.     

绿色基础设施的生态及社会功能研究进展

随着城市化进程的加快,城市硬化地表不断挤占透水表面,使得绿色基础设施规模不断下降、破碎化程度逐渐加大,严重影响了绿色基础设施服务功能的有效发挥。绿色基础设施的发展经历了早期萌芽、初步形成和快速发展三个阶段,主要在宏观尺度研究区域生态安全,中观尺度促进城市可持续发展,微观尺度解决社区生态环境问题。目前绿色基础设施的研究内容集中在其生态功能和社会功能两个方面,主要关注调蓄降雨径流、消减非点源污染、调节区域微气候、居民健康与福祉和空间布局公平性。而供需结构的合理配置也是决定绿色基础设施服务水平的关键因素。未来的研究应加强与相关学科的交叉融合,完善绿色基础设施功能的测度与评估方法,将绿色基础设施建设与实际规划相结合,以期为区域可持续发展和国家生态文明建设提供支撑与保障。     

海口市江东新区30年来海岸带城市扩展与生态格局演变

基于GIS和RS技术,在最小累积阻力MCR模型基础上引入不同源地等级的相对阻力因子构建城市扩展生态阻力面UEER模型,并结合水文分析Hydrology模型利用多时相的研究方法对海口市江东新区五个时期(1988年、2001年、2009年、2017年和2019年)的建设用地扩展格局进行动态模拟分析,从生态安全的视角探讨海口市江东新区海岸带城市扩展与生态格局演变趋势。研究结果表明：(1)2018年前研究区重点建设区表现出“摊大饼”式蔓延格局,但在研究时域内重点建设区的面积从49.48 km~2增加到61.57 km~2,建设用地总体上是逐渐集聚的,表现出以重要交通枢纽、现有居民区和商业区为中心向外扩展的趋势。(2)城市扩展是沿着建设用地适宜扩展路径进行的,因受制于生态隔离带并不与相邻建设用地直接相连,由“适宜扩展路径”引导建设用地优化开发,避免建设用地盲目的向外扩展。另外,生态隔离带有逐渐向建设用地渗入,打破了建设用地适宜性区域集中连片的扩展态势。(3)东寨港自然保护区的存在,使得江东新区东海岸以东寨港红树林自然保护区为中心形成的片状区域是生态安全核心区域,虽在相关政策的支持下,研究区的生态...     

北京城区道路沉积物污染特性

为了解城市道路沉积物污染物的浓度水平及可能造成的生态环境危害,在北京城区的生活区、文教区、交通干线和公园绿地这四种功能区的道路沉积物进行了取样监测,并分析了道路沉积物中总氮(TN)、总磷(TP)、重金属铜(Cu)、铬(Cr)、铅(Pb)、锌(Zn)和有机质(TOC)的污染特性.研究结果表明,各类功能区道路沉积物中TN、TP和TOC的含量较高.交通干线、文教区、生活区和公园绿地道路沉积物TN均值分别为0.1009、0.1440、0.1071、0.0974mg/kg,文教区道路沉积物的TN显著高于其他类型道路沉积物;TP均值分别为0.0695、0.0729、0.0665、0.0608mg/kg,以文教区最高,但未达显著水平.交通干线和文教区道路沉积物TOC浓度显著高于生活区和公园绿地,交通干线、文教区和生活区道路沉积物重金属的含量高于公园绿地.主要原因可能是人类活动和车辆交通量的影响.四类功能区氮主要以可溶态赋存,磷主要以颗粒态赋存在沉积物中,并且交通干线道路沉积物中溶解态磷比例最低.溶解态的重金属占总量的比例均较低,只有溶解态Cu达到5％以上,表明重金属主要赋存在颗粒态存在的沉积物中.道路沉积物或者外界带入的固体物质是地表径流污染物的重要来源,研究结果为城市地表污染控制提供重要参考.     

土壤有机质转化及CO2释放的温度效应研究进展

土壤有机质转化对温度变化的响应,是气候变暖与全球碳循环关系中的核心问题.掌握土壤有机质对温度变化的响应规律,对准确评价气候变暖背景下,全球土壤有机质的转化至关重要.综述了国内外大量研究成果,对基质成分、基质损耗、测试方法、微生物、水分含量等因素,对土壤有机质转化与温度关系的影响机理与影响规律以及Q10的变化规律进行了探讨.提出稳定有机质与不稳定有机质温度敏感性异同问题,应作为土壤有机质转化与温度关系中的核心问题进行深入研究.同时通过分析,提出室内短期培养是首选测试方法.分析认为微生物生长温度曲线与微生物呼吸之间不存在必然联系,而在过低和过高之间,水分含量是否会影响土壤呼吸,有待进一步试验验证.提出随着城市热岛效应这一环境问题的加剧,研究及评价更大温度区间内的城市土壤有机质对温度变化的响应规律十分重要.