首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 28 毫秒
1.
For over a century there have been continual efforts to incorporate nature into urban planning. These efforts (i.e., urban reconciliation) aim to manage and create habitats that support biodiversity within cities. Given that species select habitat at different spatial scales, understanding the scale at which urban species respond to their environment is critical to the success of urban reconciliation efforts. We assessed species–habitat relationships for common bat species at 50‐m, 500‐m, and 1 km spatial scales in the Chicago (U.S.A.) metropolitan area and predicted bat activity across the greater Chicago region. Habitat characteristics across all measured scales were important predictors of silver‐haired bat (Lasionycteris noctivagans) and eastern red bat (Lasiurus borealis) activity, and big brown bat (Eptesicus fuscus) activity was significantly lower at urban sites relative to rural sites. Open vegetation had a negative effect on silver‐haired bat activity at the 50‐m scale but a positive effect at the 500‐m scale, indicating potential shifts in the relative importance of some habitat characteristics at different scales. These results demonstrate that localized effects may be constrained by broader spatial patterns. Our findings highlight the importance of considering scale in urban reconciliation efforts and our landscape predictions provide information that can help prioritize urban conservation work.  相似文献   

2.
Reprinted with permission from Issues in Science and Technology (1990) 6(2):31–34  相似文献   

3.
Abstract: The search for generalities in ecology has often been thwarted by contingency and ecological complexity that limit the development of predictive rules. We present a set of concepts that we believe succinctly expresses some of the fundamental ideas in conservation biology. (1) Successful conservation management requires explicit goals and objectives. (2) The overall goal of biodiversity management will usually be to maintain or restore biodiversity, not to maximize species richness. (3) A holistic approach is needed to solve conservation problems. (4) Diverse approaches to management can provide diverse environmental conditions and mitigate risk. (5) Using nature's template is important for guiding conservation management, but it is not a panacea. (6) Focusing on causes not symptoms enhances efficacy and efficiency of conservation actions. (7) Every species and ecosystem is unique, to some degree. (8) Threshold responses are important but not ubiquitous. (9) Multiple stressors often exert critical effects on species and ecosystems. (10) Human values are variable and dynamic and significantly shape conservation efforts. We believe most conservation biologists will broadly agree these concepts are important. That said, an important part of the maturation of conservation biology as a discipline is constructive debate about additional or alternative concepts to those we have proposed here. Therefore, we have established a web‐based, online process for further discussion of the concepts outlined in this paper and developing additional ones.  相似文献   

4.
本论文采用污泥和土壤外源铜的活性差异系数法研究了农用污泥中铜的生态安全阈值。首先通过比较确定不同土壤条件下污泥中铜和水溶性铜的活性差异的系数,然后利用系数法得到相应土壤条件下污泥铜HC5值(即能够保护95%物种的浓度),并建立了土壤理化性质参数与污泥铜HC5值的量化关系和预测模型。最后与我国现行污泥农用标准值进行了比较,提出了修改建议。结果表明,土壤中来源污泥的铜活性均值约为来源水溶性盐的40%左右。土壤阳离子交换量(CEC)是影响土壤中污泥源铜的毒性的主控因子,可影响污泥铜HC5值变异的84.6%,而土壤pH值和有机碳含量(OC)分别可影响污泥铜HC5值变异的8.4%和1.8%。基于土壤pH、OC和CEC的三因子模型进行预测优于基于土壤pH和CEC的两因子模型,其相关性达到94.8%。与模型预测值相比,我国现行污泥农用标准GB4284-84与CJ/T309-2009中对铜限值的规定均存在着不同程度的保护不足或保护过度问题。  相似文献   

5.
A range of ELISAs in indirect and direct formats for the determination of bisphenol A (BPA) was developed. Bisphenol A carboxymethyl ether (BPA-CME), (BPA-CPE) and 4,4-bis(4-hydroxyphenyl)valeric acid were coupled with bovine serum albumin (BSA) (immunogens for the production of polyclonal antibodies), ovalbumin (OVA) and horseradish peroxidase. In general, the indirect assay was more sensitive and specific than the direct one. Using heterologous combinations of immunoreagents in the indirect assay allowed to increase assay sensitivity and specificity. The highest sensitivity was obtained for the antibodies produced against a conjugate of BPA-CPE with BSA and a conjugate of 4,4-bis(4-hydroxyphenyl)valeric acid with OVA. The detection limit of BPA in phosphate buffer was 0.03?ng?mL?1. The assay developed was also the most specific towards BPA. Maximum cross-reactivity values did not exceed 11% for 4-cumylphenol, 5% for bisphenol E and 2% for bisphenol S. Finally, the developed assay was used to analyze surface water samples spiked with known amount of BPA. The assay showed good recovery values (85–109%) for surface water with mineralization level lower than 500?mg?L?1.  相似文献   

6.
Vinylbenzyl chloride/divinylbenzene gel copolymer beads have been modified using piperidine, hexamethyleneimine, piperazine, 1-(2-aminoethyl)piperazine, and N-cyclohexyl-1,3-propanediamine. These resins were then tested for the sorption of noble metal ions, namely, Re(VII), Pd(II), Pt(IV), and Au(III), from a 0.1 M HCl solution. The effect of these resins on the sorption of other coexisting ions, such as Cu, Ni and Fe, was also studied. Of the resins tested, resin 4 [1-(2-aminoethyl)piperazine groups] showed the highest sorption capacity for Pt(IV) and Re(VII) from single and multicomponent solutions, with the sorption of Pt(IV) from the multicomponent solution (Re, Au, Pd, Pt, Cu, Ni Fe) in 0.1 M HCl reaching 68 mg Pt/g.  相似文献   

7.
Widespread human action and behavior change is needed to achieve many conservation goals. Doing so at the requisite scale and pace will require the efficient delivery of outreach campaigns. Conservation gains will be greatest when efforts are directed toward places of high conservation value (or need) and tailored to critical actors. Recent strategic conservation planning has relied primarily on spatial assessments of biophysical attributes, largely ignoring the human dimensions. Elsewhere, marketers, political campaigns, and others use microtargeting—predictive analytics of big data—to identify people most likely to respond positively to particular messages or interventions. Conservationists have not yet widely capitalized on these techniques. To investigate the effectiveness of microtargeting to improve conservation, we developed a propensity model to predict restoration behavior among 203,645 private landowners in a 5,200,000 ha study area in the Chesapeake Bay Watershed (U.S.A.). To isolate the additional value microtargeting may offer beyond geospatial prioritization, we analyzed a new high-resolution land-cover data set and cadastral data to identify private owners of riparian areas needing restoration. Subsequently, we developed and evaluated a restoration propensity model based on a database of landowners who had conducted restoration in the past and those who had not (n = 4978). Model validation in a parallel database (n = 4989) showed owners with the highest scorers for propensity to conduct restoration (i.e., top decile) were over twice as likely as average landowners to have conducted restoration (135%). These results demonstrate that microtargeting techniques can dramatically increase the efficiency and efficacy of conservation programs, above and beyond the advances offered by biophysical prioritizations alone, as well as facilitate more robust research of many social–ecological systems.  相似文献   

8.
A highly specific recognition system, capable of distinguishing between allogeneic (non-clonemates) and syngeneic (clonemates) conspecifics, exists in Anemonia sulcata (Coelenterata: Anthozoa). During a competitive interaction between allogeneic individuals, specialized structures (acrorhagi) are exposed and used to sting opponents. This complex behavior is called the acrorhagial response. In order to quantify this behavior we measured the acrorhagial response time (period from first contact with opponent to full expansion of acrorhagi). More than 320 reciprocal histoincompatibility responses were recorded. These histoincompatibility (H) markers are free components of the sea anemone mucus: they were characterized as glyco-proteins of a molecular weight <18 KD (Kilo-Dalton) containing terminal -d-glucose and/or -d-mannose. In alloimmune memory testing experiments, the memory trace in A. sulcata was found to persist for 5 d.  相似文献   

9.
染色体步行PCR技术   总被引:3,自引:0,他引:3  
染色体步行是一种常用的克隆已知基因旁侧序列的技术.本文综述了现有的染色体步行PCR技术,如反向PCR、锅柄PCR、连接介导PCR、热不对称PCR、SON PCR等,并在此基础上提出了一种新的染色体步行PCR技术的构思.它运用特异引物与随机引物的搭配,在普通PCR程序下扩增目的序列.实验中设置相应随机引物的RAPD对照,识别非目的扩增产物.文中介绍了新方法的原理,分析了这种方法的优缺点.这种方法可能是一种新的有效进行染色体步行的PCR技术,国内外尚未见相关报道.图2参26  相似文献   

10.
《Ecological modelling》2006,190(1-2):190-204
The objective of this study was to develop a forest production model for determining optimal density management regimes for upland black spruce (Picea mariana (Mill.) B.S.P.) stands based on the maximization of net production. This objective was attained via the development of an allometrically extended stand density management diagram (SDMD), which was used to describe the mass dynamics of biotic and abiotic tree components by initial density regime, site quality and fine root turnover rate. Specifically, periderm, stem, branch, foliage and abiotic crown masses were estimated employing multivariate allometric regression functions based on data derived from 125 destructively sampled trees. Below-ground mass estimates were obtained using generalized allometric relationships derived from the literature. Abiotic masses included three basic components: (1) allometrically estimated retained woody debris consisting of abiotic crown structures that remained attached to the main stem; (2) fine woody debris arising from needle loss, root turnover, and abscission of modular components; (3) coarse woody debris arising from trees which incurred mortality through self-thinning. The algorithmic version of the model (1) simultaneously calculates periodic annual net production estimates (Mg/ha/year) by 10-year intervals over 100-year rotation lengths for eight initial density conditions, (2) given (1), determines the occupancy level for which net production is maximized for each stage of development (decade interval), and (3) given (2), determines the optimal size–density trajectory within the context of a SDMD. Additionally, results derived from multiple model simulations employing a range of initial densities (1500, 1650,…, 16,350 stems/ha), site indices (9, 10,…, 15 m) and fine root turnover rates (0.2, 0.3,…,0.8 proportion/year), indicated that black spruce productivity was maximized when site occupancies were maintained slightly below the zone of imminent competition mortality. Instructions for acquiring an executable version of the model through the Internet are also included.  相似文献   

11.
Random forests for classification in ecology   总被引:27,自引:0,他引:27  
Cutler DR  Edwards TC  Beard KH  Cutler A  Hess KT  Gibson J  Lawler JJ 《Ecology》2007,88(11):2783-2792
Classification procedures are some of the most widely used statistical methods in ecology. Random forests (RF) is a new and powerful statistical classifier that is well established in other disciplines but is relatively unknown in ecology. Advantages of RF compared to other statistical classifiers include (1) very high classification accuracy; (2) a novel method of determining variable importance; (3) ability to model complex interactions among predictor variables; (4) flexibility to perform several types of statistical data analysis, including regression, classification, survival analysis, and unsupervised learning; and (5) an algorithm for imputing missing values. We compared the accuracies of RF and four other commonly used statistical classifiers using data on invasive plant species presence in Lava Beds National Monument, California, USA, rare lichen species presence in the Pacific Northwest, USA, and nest sites for cavity nesting birds in the Uinta Mountains, Utah, USA. We observed high classification accuracy in all applications as measured by cross-validation and, in the case of the lichen data, by independent test data, when comparing RF to other common classification methods. We also observed that the variables that RF identified as most important for classifying invasive plant species coincided with expectations based on the literature.  相似文献   

12.
我国的城市化水平落后于工业化水平,已成为制约我国经济与社会发展的重要因素。提升我国城市化水平,从经济上讲,具有如下重要意义:(1)有利于化解有效需求不足矛盾。(2)有利于带动相关产业增长和主人口增加。(3)有利于促进我国产业结构优化,提高经济运行质量。(4)有利于资源的综合利用和耕地保护。(5)有利于缩小城乡差距。提升我国城市化水平是我国新世纪的战略任务,必须进行相关的政策调整与选择。  相似文献   

13.
Pathogens are a significant driver of biodiversity loss. We examine two wildlife disease management strategies that have seen growing use, sometimes in combination: (i) trapping-and-culling infectious animals (disease control), and (ii) trapping-and-translocating healthy animals to a reserve, with possible future reintroduction. A reserve can improve conservation when there is no disease. But, when infection exists, we show investing in the reserve may counteract disease control. We find jointly pursuing both strategies is sub-optimal when the reserve is costly to maintain. Numerically, we examine management of Devil Facial Tumor Disease, which has generated extinction risks for Tasmanian Devils. Disease control (though not eradication) is generally part of an optimal strategy, although a reserve is also optimal if it can be maintained costlessly. This implies preserving the original population by addressing in situ conservation risks, rather than translocating animals to a reserve and giving up on the original population, is generally the first-best.  相似文献   

14.
Pathogens are a significant driver of biodiversity loss. We examine two wildlife disease management strategies that have seen growing use, sometimes in combination: (i) trapping-and-culling infectious animals (disease control), and (ii) trapping-and-translocating healthy animals to a reserve, with possible future reintroduction. A reserve can improve conservation when there is no disease. But, when infection exists, we show investing in the reserve may counteract disease control. We find jointly pursuing both strategies is sub-optimal when the reserve is costly to maintain. Numerically, we examine management of Devil Facial Tumor Disease, which has generated extinction risks for Tasmanian Devils. Disease control (though not eradication) is generally part of an optimal strategy, although a reserve is also optimal if it can be maintained costlessly. This implies preserving the original population by addressing in situ conservation risks, rather than translocating animals to a reserve and giving up on the original population, is generally the first-best.  相似文献   

15.
We propose a new approach for modeling extreme values that are measured in time and space. First we assume that the observations follow a Generalized Extreme Value (GEV) distribution for which the location, scale or shape parameters define the space–time structure. The temporal component is defined through a Dynamic Linear Model (DLM) or state space representation that allows to estimate the trend or seasonality of the data in time. The spatial element is imposed through the evolution matrix of the DLM where we adopt a process convolution form. We show how to produce temporal and spatial estimates of our model via customized Markov Chain Monte Carlo (MCMC) simulation. We illustrate our methodology with extreme values of ozone levels produced daily in the metropolitan area of Mexico City and with rainfall extremes measured at the Caribbean coast of Venezuela.  相似文献   

16.
Experimental Tests of Captive Breeding for Endangered Species   总被引:3,自引:0,他引:3  
Abstract: Several captive breeding regimes were compared for their ability to maintain fitness ( larval viability) and genetic variation in small populations of the housefly ( Musca domestica L.). Populations were either maintained at constant sizes of 40, 200, or 2000 individuals or initiated with two pairs of flies and allowed to grow to 40 individuals ( low-founder-number populations). Low-founder-number populations without migration exhibited low larval viability (22%) after 24 generations, compared to larger populations maintained at either 200 (49%) or 2000 (69%) individuals, and suffered high extinction, with only 44% of the lines surviving 24 generations. Low-founder-number populations subjected to two additional founder ( bottleneck) episodes, reducing them to two pairs of flies, suffered little additional loss in fitness or extinction compared to the single-founder treatments. Migration as low as one individual per generation (2.5% migration) significantly offset both reduced fitness and rate of extinction. Conversely, fitness was not significantly increased for low-founder-number populations when founders were selected from the top performing 20% of pairs under full-sib mating. Populations maintained at 40 individuals were not sustainable, exhibiting low larval viability (35%) and a high extinction rate (40%) over 24 generations, similar to the extinction rates for populations initiated with only four founders. Although none of the populations maintained at 200 individuals went extinct, their fitness was reduced by 20% compared to a large control population maintained at 2000 individuals. Electrophoretic variation was significantly correlated with fitness across treatments, but the correlation of fitness to narrow-sense heritability of two morphometric traits was not significant.  相似文献   

17.
The geographic distribution of the animals of Venezuela was analyzed as a basis for a series of guidelines to help develop strategies for their conservation. A total of 313 animal taxa is distributed among 24 geographic units, corresponding to the political divisions of the country. Three different criteria were considered in analyzing these data: (1) the number and density of threatened taxa were used to define a ranking system for geographic units; (2) "hotspots" were identified using the distribution of threatened endemics, and (3) a "critical faunas analysis" was used to determine the minimum number of geographic units needed to maximize the number of sampled taxa. The first two criteria emphasize the importance of protecting habitat in the northern portion of the country, where most human intervention has already taken place. But the southern portion of the country is where most of the undisturbed habitat remains. We suggest that the conservation of the animals of Venezuela must follow a mixed strategy, based on two principles: one, aimed mainly at threatened endemics, should focus on the protection of critical habitat north of the Orinoco river, the second, aimed at all threatened animals— particularly high-risk taxa—should focus on assuring the long-term persistence of the pristine habitat in the south.  相似文献   

18.
Feeding factors for the sea anemone Anthopleura midorii   总被引:1,自引:1,他引:0  
The carnivorous feeding behavior of the sea anemone Anthopleura midorii was found to be a sequence of successive feeding motions, which consisted of several separate actions: (1) tentaculation on any solid matter; (2) retention of prey by tentacles; (3) mouth opening; (4) ingestion of food; (5) digestion of food; (6) extrusion of indigestible waste material. Hot water extract of a natural prey induced the entire feeding sequence when extract was given in the form of an artificial food by mixing with -potato starch and water. The fractionated extract induced only a limited feeding action. Several amino acids induced feeding. Alanine, glycine or histidine stimulated the retention of artificial food by tentacles, and proline evoked mouth opening. Cysteine or reduced glutathione (GSH) induced food ingestion. Unnatural food stuff such as -potato starch was ingestible, if an appropriate amount of a chemical substance was added.  相似文献   

19.
Researchers employing resource selection functions (RSFs) and other related methods aim to detect correlates of space-use and mitigate against detrimental environmental change. However, an empirical model fit to data from one place or time is unlikely to capture species responses under different conditions because organisms respond nonlinearly to changes in habitat availability. This phenomenon, known as a functional response in resource selection, has been debated extensively in the RSF literature but continues to be ignored by practitioners for lack of a practical treatment. We therefore extend the RSF approach to enable it to estimate generalized functional responses (GFRs) from spatial data. GFRs employ data from several sampling instances characterized by diverse profiles of habitat availability. By modeling the regression coefficients of the underlying RSF as functions of availability, GFRs can account for environmental change and thus predict population distributions in new environments. We formulate the approach as a mixed-effects model so that it is estimable by readily available statistical software. We illustrate its application using (1) simulation and (2) wolf home-range telemetry. Our results indicate that GFRs can offer considerable improvements in estimation speed and predictive ability over existing mixed-effects approaches.  相似文献   

20.
We observed kelp gametophytes endophytic in the cell walls of 17 species of red algae from the San Juan Islands, Washington, USA. Host algae were collected primarily from three sites dominated by different kelp assemblages, including (1) a subtidal site dominated by Agarum fimbriatum Harvey, (2) a second subtidal site dominated by Nereocystis luetkeana (Mertens) Postels et Ruprecht, and (3) a floating dock on which the dominant kelp species were Alaria marginata Postels et Ruprecht, Laminaria groenlandica Rosenvinge, and Costaria costata (C. Agardh) Saunders. Most hosts were filamentous [e.g. Pleonosporium vancouverianum (J. Agardh) J. Agardh, Callithamnion acutum Kylin], or polysiphonous [e.g. Polysiphonia paniculata Montagne, Pterosiphonia dendroidea (Montagne) Falkenberg]; however, similar endophytes were also observed in membranous or bladed red algae [e.g. Membranoptera platyphylla (Setchell et Gardner) Kylin, Polyneura latissima (Harvey) Kylin]. Dozens to hundreds of separate kelp gametophytes were associated with single host thalli. In many cases, the gametophytes developed conspicuous oogonia raised above the thallus surface on characteristic stalks. Presumed zygotes developed through typical embryonic stages into juvenile sporophytes. We argue that the endophytic habit plays an important role in the biology of kelp gametophytes. Received: 5 May 1998 / Accepted: 6 May 1999  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号