Dam effects on bedload transport on the upper Santa Ana River,California, and implications for native fish habitat

Dams disrupt the flow of water and sediment and thus have the potential to affect the downstream geomorphic characteristics of a river. Though there are some well‐known and common geomorphic responses to dams, such as bed armouring, the response downstream from any particular dam is dependent on local conditions. Herein, we investigate the response of the upper Santa Ana River in southern California, USA, to the construction of a large dam at the transition from mountains to valley, using calculations of bedload transport capacity on the mainstem below the dam and for major tributaries. Approximate sediment budgets were constructed for downstream reaches to estimate deposition and erosion rates for sand, gravel, and cobble particle sizes. Our results indicate that the classical response of bed armouring and erosion is likely limited to a short reach immediately below the dam. Farther downstream, though transport capacity is reduced by flow regulation by the dam, the channel reaches are likely to remain depositional but with reduced deposition rates. Persistent deposition, as opposed to erosion, is the result of the replenishment of flow and sediment supply by large downstream tributaries. In addition, the calculations indicate that the composition of the bed is unlikely to change substantially in downstream reaches. A Monte Carlo approach was employed to estimate the uncertainty in the sediment budget predictions. The impacts of the dam on the geomorphic character of the river downstream could have implications for native fish that rely on coarse substrate that supports their food base.     

新时代长江鱼类多样性保护的思考

长江是我国第一大河流,是世界生物多样性的热点区域,也是我国鱼类多样性最高的河流之一。在介绍长江鱼类主要生态习性生境条件的基础上,分析了导致鱼类多样性下降的主要因素——生境丧失和过度捕捞,并简要总结了目前已采取的保护措施及存在的问题,提出了关于新时期长江鱼类多样性保护的思考与建议:①建立以流域管理机构牵头,相关部门和地方共同组建流域生态保护机制;②有计划开展支流及通江湖泊的生态恢复,使支流的小水电逐步退出,使原本的通江湖泊恢复自然江湖关系;③提高民众环保意识,积极建立全流域禁捕机制和休闲垂钓机制,并让垂钓者成为渔政的管理者和监督者。     

The impacts of cattle access points on deposited sediment levels in headwater streams in Ireland

Cattle access to streams has been linked globally with degradation of stream water quality, driven largely by bank erosion and resultant instream, fine sediment deposition. The majority of evidence on such effects is however based in arid and semiarid regions of the United States and Australia, with few studies relating to cool temperate climates such as Northwest Europe. In this study, “Quorer” resuspendable sediment samples were taken from riffle geomorphic units upstream (control) and at two points downstream (pressure and recovery) of cattle access points in headwater streams in agricultural catchments in Ireland to assess levels of deposited stream sediment. Samples were taken in April/May (2016) prior to the grazing season and in October (2016) at the end of the grazing season. Sites in good‐high ecological status catchments and less than good ecological status catchments were included in the study. Higher levels of sediment were found downstream of cattle access points in both good‐high status and less than good status catchments; however, the impacts of access points were spatially confined to, in most cases, the area immediately downstream of the point of access. There was a strong correlation between deposited sediment mass and organic matter (OM) mass, with levels of OM increasing linearly with deposited sediment mass. Levels of measured sediment were negatively correlated with riparian habitat health (measured using a qualitative habitat assessment). The results of this study highlight the need for measures to prevent cattle access to headwater streams where access points can be many in order to manage local habitat quality and downstream water quality issues.     

Genetic Variation of the Endangered Gentiana lutea L. var. aurantiaca (Gentianaceae) in Populations from the Northwest Iberian Peninsula

Gentiana lutea L. (G. lutea L.) is an endangered plant, patchily distributed along the mountains of Central and Southern Europe. In this study, inter-simple sequence repeat (ISSR) markers were used to investigate the genetic variation in this species within and among populations of G. lutea L. var. aurantiaca of the Cantabrian Mountains (Northwest Iberian Peninsula). Samples of G. lutea L. collected at different locations of the Pyrenees and samples of G. lutea L. subsp. vardjanii of the Dolomites Alps were also analyzed for comparison. Using nine ISSR primers, 106 bands were generated, and 89.6% of those were polymorphic. The populations from the Northwest Iberian Peninsula were clustered in three different groups, with a significant correlation between genetic and geographic distances. Gentiana lutea L. var. aurantiaca showed 19.8% private loci and demonstrated a remarkable level of genetic variation, both among populations and within populations; those populations with the highest level of isolation show the lowest genetic variation within populations. The low number of individuals, as well as the observed genetic structure of the analyzed populations makes it necessary to protect them to ensure their survival before they are too small to persist naturally.     

广东省自然保护地暗夜公园建设选址 适宜性评价

快速城市化引起的光污染使得黑暗的夜空逐渐稀 缺。暗夜公园作为暗夜保护的主要类型之一，在国内外受到越 来越多的关注。具有优越本底环境的自然保护地是暗夜公园建 设选址的重要备选对象。根据国际暗夜协会对暗夜公园的认证 要求，初步筛选出广东省具有暗夜公园建设潜力的备选保护 地，将NPP-VIIRS夜间灯光数据作为暗夜资源识别的依据， 从观星质量制约条件、游客吸引程度和政府投资可行性三方面 出发，构建暗夜公园建设选址适宜性综合评价指标体系；应用 GIS空间分析法和层次分析法，探讨广东省建立暗夜公园最适 宜的自然保护地。结果表明：广东省适合建设暗夜公园的自然 保护地数量占比仅约为3%，其中2/3集中在经济发展落后于珠 三角地区的粤西、粤东和粤北地区，1/3分布于珠三角地区的 惠州市和江门市。暗夜公园建设最优选址为梅州五华天堂山市级 自然保护区，该自然保护地具有晴天率高、与城镇距离适中、周 边旅游景点多等优势，且具有丰富的山区生态资源与深厚的客家 文化底蕴，有利于打造具有地方特色的暗夜公园。通过制定一套 自然保护地暗夜公园选址适宜性评价的方法和流程，为广东省自 然保护地暗夜公园建设提供了重要的选址参考。     

保护地旗舰物种栖息地与社区生计空间 关系识别的适宜性评价方法

科学识别保护物种栖息地与社区生计的空间关系及 格局特征，是制定国家公园和自然保护地规划，减少野生动物 与人冲突的基础，是实现人与自然和谐共生的重要支撑。以高 原湿地旗舰物种黑颈鹤(Grus nigricollis )及保护地社区系 统为研究对象，选择黑颈鹤重要的越冬地——云南大山包黑颈 鹤国家级自然保护区为案例区，采用适宜性评价方法，结合 MaxEnt模型和多种空间分析技术，辨识和评价了黑颈鹤栖息 与当地社区生计空间的适宜性，基于二者的适宜性评价结果运 用空间自相关和椭圆标准差法，分析黑颈鹤栖息地保护空间与 社区生计空间的热点区域和分布方向特征。研究发现，黑颈鹤 保护与社区生计存在冲突、共生与共存的多种空间作用关系， 并具有动态变化特征；不同功能空间适宜性热点区虽然存在部 分重叠，但具备错位发展潜力。研究结果为科学制定国家公园 和自然保护地规划及管控对策，实现保护物种与社区协调发展 提供了科学支撑。     

西安浐灞国家湿地公园植物群落景观营造研究

湿地公园植物群落构景营造具有特殊性,本文以西安浐灞国家湿地公园为研究对象,依托景观生态学理论。从湿地公园的功能角度考虑,根据湿地环境的不同特点,从陆生、湿生、水生、岛屿四种环境特点总结出浐灞湿地公园植物群落组合的营造模式。     

重庆主城区山地公园林缘边缘效应的研究

以重庆主城区山地公园林缘的光照、湿度、温度和植物多样性为研究对象,采用样带研究法,分析和探讨其林缘生境的光照、湿度、温度和植物梯度变化规律.发现山地公园光照从缘外到缘内呈现出骤减-缓慢下降-基本不变的梯度变化规律;空气湿度从缘外到缘内逐渐增高,白天温度与光照变化规律成正相关;植物多样性从缘外到缘内表现出先增加后减少的特性;初步得出重庆主城区山地公园林缘边缘效应宽度基本在6～14m之间波动,且边界木缘外3m到缘内2m是边缘效应强度值最大的区域.提出山地公园林缘植物配置应遵循从缘外到缘内依次配置阳性、半阴性、耐阴和阴生植物这一规律.     

为下一代作准备:林后四林平地森林园区规划

林后四林平地森林园区是一处集平地造林、在地文化、栖地营造、资源利用与环境教育为一体的学习园区.在其不断的发展下,现成为大武山低海拔自然森林园区,作为生态栖地修复、区域文化体验及休闲游憩的场域.从环境修复的角度保有农垦地和草生地生态环境,并营造大武山低海拔森林的栖地环境,提供猛禽、鸟类及两栖类动物栖息繁衍之地.重视生态保育意义的同时,发挥环境教育和生态旅游的价值.因气候环境变迁,以分散排水、贮流、自然人渗及自然过滤方式为主,同时进行土壤地利改良,达到环境保全修复的功效.以现地环境保育及生态演变历史延续对自然环境的关怀,营造合宜的生态栖地、掌握水资源的保存与再利用,为下一代的自然生态环境作准备.