Multiple structural modifications to dendritic ecological networks produce simple responses

Structural modifications to landscapes affect the ability of organisms to access different habitat patches. There exist, however, very few general methods by which to relate modifications to expectations of effects, and even fewer that enable understanding of how multiple modifications may interact. In the absence of any guiding principles, ecologists have assumed that interactions will result in complex landscape-scale effects. One way of understanding such effects is through rendering a landscape as a graph or network, among the simplest of which are dendritic networks typified by stream systems. Yet even for stream networks, there are no known general principles concerning the nature of interactions between multiple modifications. We developed a model to describe the ability of fish to access and use different habitat patches within dendritic networks. We used mathematical and numerical analyses of the model to investigate how the habitat value of a network is affected by changes in connectivity and habitat quality, and then to examine interactions between multiple modifications. Rather than showing complex interactions, our analytic and simulation-based results show that the combined effect of multiple modifications approximately equals the sum of individually predicted effects. Dendritic networks thus appear to respond far more simply to multiple modifications than has previously been assumed. These results have implications for stream management planning, and offer a firm foundation from which to better understand population processes within dendritic networks.     

Evaluating Rapid Participatory Rural Appraisal as an Assessment of Ethnoecological Knowledge and Local Biodiversity Patterns

Abstract:  There is a pressing need to find both locally and globally relevant tools to measure and compare biodiversity patterns. Traditional ecological knowledge (TEK) is important to biodiversity monitoring, but has a contested role in preliminary biodiversity assessments. We examined rapid participatory rural appraisal (rPRA) (a tool commonly used for local needs assessments) as an alternative to surveys of vascular plants conducted by people with local knowledge. We used rPRA to determine the local-knowledge consensus on the average richness, diversity, and height of local grasses and trees in three habitats surrounding Boumba, Niger, bordering Park-W. We then conducted our own vascular plant surveys to collect information on plant richness, abundance, and structure. Using a qualitative ranking, we compared TEK-based assessments of diversity patterns with our survey-based assessments. The TEK-based assessments matched survey-based assessments on measures of height and density for grasses and trees and tree richness. The two assessments correlated poorly on herb richness and Simpson's D value for both trees and grasses. Plant life form and gender of the participant affected the way diversity patterns were described, which highlights the usefulness of TEK in explaining local realities and indicates limitations of using TEK as a large-scale assessment tool. Our results demonstrate that rPRA can serve to combine local-knowledge inquiry with scientific study at a cost lower than vascular plant surveys and demonstrates a useful blunt tool for preliminary biodiversity assessment.     

Bayesian Networks and Adaptive Management of Wildlife Habitat

Abstract: Adaptive management is an iterative process of gathering new knowledge regarding a system's behavior and monitoring the ecological consequences of management actions to improve management decisions. Although the concept originated in the 1970s, it is rarely actively incorporated into ecological restoration. Bayesian networks (BNs) are emerging as efficient ecological decision‐support tools well suited to adaptive management, but examples of their application in this capacity are few. We developed a BN within an adaptive‐management framework that focuses on managing the effects of feral grazing and prescribed burning regimes on avian diversity within woodlands of subtropical eastern Australia. We constructed the BN with baseline data to predict bird abundance as a function of habitat structure, grazing pressure, and prescribed burning. Results of sensitivity analyses suggested that grazing pressure increased the abundance of aggressive honeyeaters, which in turn had a strong negative effect on small passerines. Management interventions to reduce pressure of feral grazing and prescribed burning were then conducted, after which we collected a second set of field data to test the response of small passerines to these measures. We used these data, which incorporated ecological changes that may have resulted from the management interventions, to validate and update the BN. The network predictions of small passerine abundance under the new habitat and management conditions were very accurate. The updated BN concluded the first iteration of adaptive management and will be used in planning the next round of management interventions. The unique belief‐updating feature of BNs provides land managers with the flexibility to predict outcomes and evaluate the effectiveness of management interventions.     

西安市生态文明建设评价及预测

根据生态文明的涵义和生态市建设的总体思路,提出了生态文明建设3（系统层、子系统层、单项指标层）×3（经济发展,社会进步,环境保护）评价体系,其中包括25个单项指标。对西安市1998-2007年生态文明建设进行了定量评价研究,结果表明西安市生态文明建设处于整体上升的趋势;在此基础上,应用自回归预测模型对西安市经济、社会、环境和生态文明建设发展进行了预测,为西安市全面协调发展提供参考借鉴。     

浅谈城市绿化建设

城市绿化是改善城市生态环境,提升城市形象,提高城市居民生活质量的有效途径之一.笔者提出了城市绿化的概念和内涵,提出了城市绿化必须坚持的三个原则:生态原则、坚持景观效应、坚持经济原则,分析了当前我国城市绿化存在的主要问题,并提出了改进的思路和措施.参10.     

间伐对生态公益林冠层结构及土壤养分的影响

为定量分析上海城郊生态公益林间伐后林分冠层结构变化及对林下环境的影响,2009年7月采用TRAC植物冠层分析仪研究了香樟（Cinnamomum camphora）、杜英（Elaeocarpus sylvestris）和栾树（Koelreuteria paniculata）3种生态公益林间伐2年后林分冠层结构参数,设置临时样方调查各林分林下植物分布及生物量,测定了土壤N、P、K和有机质的变化。结果表明：间伐后3种林分的LAI、丛生指数和平均接触次数均降低,而间隙分数增大。间伐增加了林分间隙和LAI的空间异质性,间伐后3个树种LAI变异系数增加了19%～45%。轻度间伐后香樟、杜英和栾树林下PPFD（Photosynthetic Photon Flux Density）分别是未间伐林分的1.6、7和2.1倍,重度间伐香樟林内PPFD增大了8.9倍。间伐后林下植物种类、总盖度和干生物量随林下PPFD增加呈增大趋势。除全P和全K含量没有变化外,林地土壤全N、速效K、速效P和有机质含量均比未间伐林地有不同程度降低,但轻度间伐杜英林地速效养分消耗显著高于香樟和栾树林分。因此,研究区生态公益林结构调控需根据树种特性和林下环境变化,确定适宜的发展模式,提高公益林的综合效益。     

基于水土流失的景观格局分析方法

景观格局和生态过程是景观生态学研究的重要内容,但是很多研究只重视景观格局的研究,而忽略了生态过程的研究。文章针对水土流失这一重要生态过程,提出了基于水土流失过程的景观坡度指数和景观空间负荷对比指数,并对黄土高原泾河流域15个子流域的景观格局进行了分析,认为泾河流北部各子流域主要以水土流失的＂源＂景观为主,景观坡度指数大,空间负荷指数小,水土流失风险大;流域南部各子流域上游以＂汇＂景观为主,坡度指数大,中下游以＂源＂景观为主,景观空间分布不均衡,存在一定的水土流失风险;流域东部局部子流域主要以水土流失的＂汇＂景观为主,＂源＂景观相对较小,＂源＂-＂汇＂景观空间分布均衡,水土流失风险小。     

论全球生态经济系统的不可持续性——基于农业生态系统承载力视角

运用3种方法预测的作物产量潜力分别为：（1）利用作物历年单产回归拟合后进行趋势外推,得出多数作物的未来产量潜力极限大约将是现在单产的2～3倍;（2）运用＂国际应用系统研究所＂（IIASA）与＂联合国粮农组织＂（FAO）共同开发的＂农业生态区划＂（AEZ）模型计算我国主要粮油作物的区域单产最高潜力,得出水稻、小麦、玉米、马铃薯、油菜和大豆的单产潜力分别是它们2005年全国平均单产的1.2、2.2、2.2、2.9、2.0、1.9倍;（3）运用自然界中植物的最大光能利用率计算世界主要粮油作物单产的光合潜力,得出水稻、小麦、玉米、马铃薯、油菜、大豆产量的最大光合生产潜力大约分别是目前高产地区单产的1.4、2.5、1.2、1.8、1.9、2.2倍。据此：从作物产量潜力极限出发,阐述了农业生态系统的承载力;再从＂封闭＂系统特性出发,论述了全球生态经济系统的不可持续性。人类所能做的是尽力延缓＂终点＂的出现：行动越早,效果越好。     

西藏生态整体性水平测度

为了探讨资源-环境双重约束下地处我国生态环境脆弱区的西藏的生态整体性特征,利用生态环境质量指数和生态现代化指数（EMI）对地处我国西南边陲的西藏地区的生态现代化水平进行了分析。结果表明：全球生态现代化水平在区域之间存在比较明显的空间分异。2004年西藏生态现代化指数为50,在全国排名为3位,较2000年的排名16位有了明显的提高。生态进步指数、经济生态化指数好于其他4个少数民族地区,但社会生态化指数落后于其他4个少数民族地区,人均SO2排放与新疆、广西相同,但高于内蒙古和宁夏;1980—2007年西藏现代化程度虽然有所提升,但远低于世界平均水平和中等发达国家以及我国平均水平和其他4个少数民族地区;1996—2007年西藏区域环境水平呈＂W＂型变动态势。资源转化率和水污染指数呈＂N＂型不稳定变动,生态保护指数和环境治理指数呈剧烈变动,生态脆弱性和环境支持系统的不稳定性没有明显改观。因此,西藏应立足地缘和资源优势,充分考虑西藏生态地域、生态系统服务功能、生态资产、生态敏感性以及人类活动对生态环境胁迫等要素的综合影响,依据青藏高原高寒生态大区和高寒草甸生态区、青藏高原高山草原、高寒草甸生态地区生态区划,发展人工设计生态方案的生态重建途径。建立严格的生态补偿制度,逐步提升生态现代化水平。     

外来红树植物无瓣海桑的入侵生态特征

无瓣海桑因其具有速生性的特点而被广泛的用于滩涂海岸造林和控制外来杂草互花米草。但是同样作为外来种,无瓣海桑其自身的入侵性及生态风险已经成为近年来研究的一大热点。依据外来种风险评估的侧重点,分别从定居特性、传播特性及其影响等方面总结了国内外无瓣海桑的入侵生态特征的相关研究,表明无瓣海桑具有速生、高生产力、对低温和土壤具有一定的适应性、已在澳门等地出现扩散入侵现象等利于入侵的特点;但是同时它生态位宽度中等,繁殖率较低,并且它的种植会改善红树林生态系统土壤养分,有利于乡土红树植物的生长。现有对无瓣海桑入侵生态特征的定性研究并不能完全确定其入侵性和生态风险。因此今后需采用风险评估模型等手段对无瓣海桑入侵性进行更为深入地评估。