废塑料资源化产品对土壤中过氧化氢酶和脲酶活性的影响(Effect of Waste Plastics Recycling Products on Activities of Soil Catalase and Urease)

为探讨废塑料资源化产品对土壤酶活性的影响,通过室内培养试验研究了废塑料资源化产品暴露后土壤中过氧化氢酶和脲酶活性的变化.结果表明:废塑料资源化产品对土壤酶活性具有显著影响.250mg·kg-1、1250mg·kg-1、7250mg·kg-1废塑料资源化产品浓度处理对土壤中过氧化氢酶和脲酶影响明显不同.在土壤培养l～5d内,添加废塑料资源化产品的3个浓度处理土壤中过氧化氢酶活性显著低于对照(p<0.05),表现出明显的抑制作用,且浓度越高抑制作用越强.而后(5～35d),低浓度(250mg·kg-1)废塑料资源化产品对土壤过氧化氢酶一直表现为激活作用,但是,高浓度(1250mg·kg-1和7250mg·kg-1)处理对土壤过氧化氢酶活性则表现为激活-抑制-激活作用,且抑制、激活程度与处理浓度成呈相关.3个废塑料资源化产品浓度处理对脲酶活性影响在培养1～28d内主要是激活作用,且激活作用随着处理浓度的增大而增强,而后(28～35d)对脲酶活性表现为抑制作用.     

多氯联苯对我国土壤微生物的生态毒理效应

作为持久性有机污染物(POPs),多氯联苯(PCBs)一旦进入土壤将长期存留并对土栖生物产生潜在危害。土壤微生物是土壤生态系统重要组成部分,研究外源PCBs对土壤微生物的生态毒理效应,筛选出指示PCBs污染的敏感指标并获取可靠的生态毒理数据十分重要。研究以江西红壤和天津潮土为供试土壤,在室内25℃连续培养28 d的条件下进行了生态毒理实验,选择了微生物量碳、呼吸强度、代谢熵、硝化作用、脱氢酶活性、脲酶活性和微生物群落功能多样性为微生物指标。结果显示:1)在28 d培养时间内,多氯联苯(PCBs)的毒性作用随培养时间的延长而增强,且在红壤中的毒性作用强于在潮土中,表明PCBs对土壤微生物的毒性作用存在时间效应并受土壤性质的影响。2)各微生物指标的敏感性不同,微生物量碳、脲酶活性和微生物功能多样性对PCBs污染反应不够敏感,而土壤呼吸强度、代谢熵、硝化作用和脱氢酶活性对PCBs污染反应敏感。3)14 d时,红壤中PCBs对脱氢酶活性、呼吸强度和代谢熵的EC10值分别为1.20、3.18和1.09 mg·kg-1,而在潮土中分别为6.31、4.73和50 mg·kg-1;28 d时,红壤中PCBs对硝化作用、脱氢酶活性、呼吸强度和代谢熵的EC10值分别为2.32、0.77、0.51和0.71mg·kg-1,而在潮土中分别为5.91、1.65、3.00和50 mg·kg-1。综合考虑经济和实际需要等因素,建议将呼吸强度、硝化作用和脱氢酶活性作为PCBs污染土壤生态毒理评价中的首选敏感指标,并建议培养时间设置为28 d。     

河流湿地土壤芘的降解和生物有效性模型与酶活性动态变化(Model of Pyrene Degradation and Bioavailability and Dynamic Changes of Enzymatic Activities in the Riverine Wetland Soil)

在淹水和非淹水条件下,在河流湿地土壤中加入高浓度(10mg·kg-1)和极高浓度(200mg·kg-1)芘,研究了芘降解过程、芘生物有效性和土壤酶活性的长期动态变化.结果表明,培养91d后,高浓度芘处理的土壤中芘的残留率在淹水和非淹水条件下分别为79.0%和51.4%,而极高浓度处理的芘残留率在淹水和非淹水条件下分别为61.1%和33.9%.利用Tenax-ta树脂提取快速解吸态生物有效芘,结果发现,有效芘浓度在高浓度芘处理的两种土壤中的值比较接近,分别为1.01mg·kg-1和1.23mg·kg-1;而有效芘浓度在极高浓度处理的两种土壤的相应值差别较大,分别为20.31mg·kg-1和9.44mg·kg-1.采用四参数Logistic模型能够精确地拟合芘降解过程和生物有效性变化过程(p<0.0001).土壤蔗糖酶、脲酶和多酚氧化酶对芘污染敏感,而过氧化氢酶对芘污染不敏感.实验结果揭示了河流湿地土壤芘在淹水条件下降解活跃阶段持续时间短和芘生物有效性高的特征以及土壤蔗糖酶、脲酶和多酚氧化酶活性可以作为评估芘污染影响的候选指标.     

镉胁迫对吊兰生长与土壤酶活性的影响

选用观赏植物吊兰进行盆栽试验,研究了吊兰对Cd的耐性、高浓度Cd胁迫对土壤酶活性以及土壤有效态Cd含量的影响.结果表明,随着Cd浓度的不断提高,脲酶活性显著下降.过氧化氢酶和蔗糖酶活性在Cd浓度为10 mg.kg-1的时候均达到了顶峰,而土壤磷酸酶活性则在Cd浓度为50 mg.kg-1的时候最大.4种土壤酶对重金属的敏感顺序为:脲酶>磷酸酶>蔗糖酶>过氧化氢酶.吊兰对Cd具有很强的耐性,在1500 mg.kg-1Cd胁迫浓度范围内,吊兰对Cd的耐性指数均大于50%.土壤有效态Cd与土壤Cd添加量和土壤酶活性呈显著相关性,可将土壤有效态Cd含量和土壤酶活性这两类指标作为镉污染土壤的评价指标.     

甲磺隆结合残留对土壤酶活性的影响

为了研究甲磺隆结合残留对土壤酶活性的影响,将黄粉土(水稻土)经甲磺隆结合残留处理98天,检测土壤脲酶、酸性磷酸酶、过氧化氢酶和蔗糖酶活性.结果表明,甲磺隆结合残留对土壤酶活性的影响不仅与甲磺隆结合残留处理浓度和培养时间有关,同时还与土壤酶种类有关.培养前期(第14天前),甲磺隆结合残留对土壤酸性磷酸酶和过氧化氢酶具有抑制作用,而对土壤脲酶和蔗糖酶的影响则表现为低浓度时激活,高浓度时抑制;培养后期(第14天后),甲磺隆结合残留对土壤脲酶、酸性磷酸酶和过氧化氢酶具有激活作用,在一定浓度范围内(0.050~0.281mg·kg-1)对土壤蔗糖酶也具有一定激活作用;就土壤酶而言,在污染早期,土壤过氧化氢酶对甲磺隆结合残留较敏感,可以作为表征甲磺隆结合残留土壤污染的生物活性指标.     

除草剂莠去津对长期定位施肥土壤中酶活性的影响

研究了除草剂莠去津对4种长期定位施肥处理土壤中脲酶、磷酸酶、脱氢酶、蔗糖酶活性的影响．不同肥力处理的不施肥对照土壤、NPK肥土壤、NPK+秸秆和NPK+有机肥土壤中,4种酶受莠去津影响有明显差别．在莠去津处理初期,土壤中的脲酶活性受到不同程度地刺激作用,中期和后期土壤中的脲酶活性均受到抑制．其中NPK+有机肥土壤中的脲酶活性受到的抑制程度随着处理时间的延长而增加．在整个处理过程中NPK+秸秆土壤中的磷酸酶活性几乎不受莠去津抑制．其它3种土壤中的磷酸酶活性都不同程度地受到抑制,而且对照土壤受到的抑制程度最深．NPK土壤中的脱氢酶活性在处理初期受到刺激作用,中期和后期都受到抑制．其它3种土壤在处理初期和中期都受到抑制作用,但是后期抑制作用消失．NPK土壤和NPK+有机肥土壤中的蔗糖酶活性始终受到不同程度的激活,而且在处理后期激活作用加强．对照土壤中蔗糖酶受莠去津的影响较小,NPK+秸秆土壤中的蔗糖酶活性始终受到抑制作用．土壤中添加莠去津为5mg·kg-1时,处理16d的4种酶平均酶活性与不添加莠去津的土壤中平均酶活性没有显著差异．     

大气CO2浓度升高对添加麦秸条件下稻田土壤酶活性的影响

利用中国扬州开放式大气CO2浓度升高(FACE)系统稻麦轮作试验平台,研究大气CO2浓度升高对稻田小麦秸秆降解过程中土壤酶活性的影响.试验平台设置FACE[(580±60)μmol·mol-1]和对照[(380±40)μmol·mol-1]2个CO2浓度,在低氮(150 kg·hm-2)和高氮(250 kg·hm-2)2种氮水平下添加小麦秸秆,分别在不同生长时期采样并分析土壤脱氢酶、脲酶、磷酸酶和蔗糖酶活性.结果表明:同一氮水平下,大气CO2浓度升高显著增强土壤脱氢酶、脲酶和蔗糖酶活性,但显著降低土壤磷酸酶活性;无论是大气CO2浓度升高条件下还是对照条件下,低氮处理土壤脱氢酶与脲酶活性均高于高氮处理,而高氮处理土壤磷酸酶活性均高于低氮处理,氮水平对蔗糖酶活性并无显著影响.     

重金属和多环芳烃复合污染对土壤酶活性的影响及定量表征

以土壤脲酶和脱氢酶为探针物质，室内培养条件下较为系统地研究了重金属（Cd、Zn、Pb）和多环芳烃（菲、荧蒽、苯并a芘）复合污染对土壤酶活性的影响及其定量表征、结果表明，复合投加上述污染物能使土壤酶活性受到不同程度的抑制，其中，脱氢酶最为敏感，其活性是表征重金属和多环芳烃复合污染的一项重要的参考指标．对复合污染模型的建立与分析表明，土壤环境中，重金属和多环芳烃复合污染的类型和强度与污染物的浓度和复合污染时间密切相关．影响土壤脲酶活性的主要因子依次为：Cd〉Zn与苯并a芘的交互作用〉Zn〉Pb〉Zn和菲的交互作用，影响土壤脱氢酶活性的主要因子依次为：Cd和Zn的交互作用〉Cd〉Zn〉苯并a芘〉Cd和菲的交互作用，其中，Zn和苯并a芘相互作用对脲酶活性以及Cd和Zn交互作用对脱氢酶活性的影响均表现为拮抗作用，Zn和菲，Cd和菲之间的交互作用，无论是对脲酶还是脱氢酶均表现为协同作用，图1表3参18     

镉污染对红壤和潮土微生物的生态毒理效应

以土壤微生物生物量碳(Cmic)、土壤酶活性及微生物多样性为微生物学指标,以0.01mol·L-1CaCl2作为Cd有效态提取剂,以江西红壤和天津潮土为供试土壤,在室内25℃连续培养28d的条件下探讨了外源Cd对土壤微生物的生态毒理效应。结果表明:1)不同培养时间潮土CaCl2提取态Cd含量均显著低于红壤,潮土微生物受到Cd的抑制作用也明显小于红壤。2)各微生物指标的敏感性不同,并受土壤类型和培养时间的影响,其中,脱氢酶的敏感性强于脲酶,微生物功能多样性指标中BiologEco板上每孔的平均吸光值(AWCD)的敏感性强于Shannon指数;Cmic、脲酶、脱氢酶、AWCD和Shannon指数均在红壤中更为敏感。选取的5个微生物指标对Cd污染都有良好的响应,均可作为Cd污染土壤微生物生态毒理实验中的测试指标。在土壤酶指标中,可优先选取脱氢酶作为测试指标。3)Cd对Cmic、土壤酶、微生物功能多样性的抑制作用存在时间效应。14dCd对Cmic的抑制作用大于28d,而对脲酶和脱氢酶的抑制作用小于28d。建议Cd污染土壤微生物生态毒理实验中将培养时间设置为28d或适当延长。4)28d时,红壤中Cd对Cmic、脱氢酶、脲酶、AWCD、Shannon指数的EC10分别为1.31、0.26、0.93、0.08、22.71mg·kg-1,而在潮土中分别为1.97、0.69、13.12、0.09、>200mg·kg-1。     

菲和镉复合污染对土壤微生物的生态毒理效应

以土壤酶活性和微生物数量作为生态毒理指标,通过模拟试验,比较分析多环芳烃菲和重金属镉单一与复合污染对土壤微生物的生态毒理效应.结果表明,菲和镉复合污染对土壤蔗糖酶、脲酶和脱氢酶均具有协同抑制作用;而对磷酸酶和微生物的数量具有拮抗抑制作用.菲和镉复合污染及菲单一污染对土壤微生物的活性抑制率从大到小依次为：放线菌＞真菌＞细菌;镉单一污染则为：真菌＞细菌＞放线菌.     

Achieving Open Access to Conservation Science

Conservation science is a crisis discipline in which the results of scientific enquiry must be made available quickly to those implementing management. We assessed the extent to which scientific research published since the year 2000 in 20 conservation science journals is publicly available. Of the 19,207 papers published, 1,667 (8.68%) are freely downloadable from an official repository. Moreover, only 938 papers (4.88%) meet the standard definition of open access in which material can be freely reused providing attribution to the authors is given. This compares poorly with a comparable set of 20 evolutionary biology journals, where 31.93% of papers are freely downloadable and 7.49% are open access. Seventeen of the 20 conservation journals offer an open access option, but fewer than 5% of the papers are available through open access. The cost of accessing the full body of conservation science runs into tens of thousands of dollars per year for institutional subscribers, and many conservation practitioners cannot access pay‐per‐view science through their workplace. However, important initiatives such as Research4Life are making science available to organizations in developing countries. We urge authors of conservation science to pay for open access on a per‐article basis or to choose publication in open access journals, taking care to ensure the license allows reuse for any purpose providing attribution is given. Currently, it would cost $51 million to make all conservation science published since 2000 freely available by paying the open access fees currently levied to authors. Publishers of conservation journals might consider more cost effective models for open access and conservation‐oriented organizations running journals could consider a broader range of options for open access to nonmembers such as sponsorship of open access via membership fees. Obtención de Acceso Abierto a la Ciencia de la Conservación     

Some polyphagous Homoptera gain protection from their natural enemies by feeding on the toxic plantsSpartium junceum andErythrina corallodendrum (Leguminosae)

Summary Interactions were studied among alkaloid-containing legumes (Erythrina corallodendrum andSpartium junceum) and non-toxic plants (Citrus sinensis, Cucurbita moschata andEuphorbia tirucalli), several polyphagous homopterans,Aphis craccivora (Aphididae),Icerya purchasi, I. aegyptiaca (Margarodidae),Lepidosaphes ulmi (Diaspididae) andPlanococcus citri (Pseudococcidae), and some major natural enemies of these homopterans. Significant reductions in survival due to negative effects of alkaloid containing as compared with non-alkaloidal plants were recorded for the predatorsRodolia cardinalis andChilocorus bipustulatus, but not forCryptolaemus montrouzieri (Coleoptera: Coccinellidae),Chrysoperla carnea (Neuroptera: Chrysopidae) andSympherobius sanctus (Neuroptera: Sympherobiidae). The development time of the larvae or pupae ofR. cardinalis, C. carnea andS. sanctus was longer on the toxic plants than on the non-toxic ones. The percentage of parasitism ofA. craccivora collected from the non-alkaloidal plantsVicia palaestina andMelilotus albus was much higher than that onS. junceum. The parasitoid complexes ofA. craccivora differed between both plant groups. The nutritive value of honeydew ofI. purchasi andA. craccivora, as expressed by the life span ofEncyrtus infelix (Hymenoptera: Encyrtidae) adults, was also investigated. Life spans were significantly longer when the wasps fed on honeydew produced on non-alkaloidal plants (C. sinensis andPittosporum tobira) than on alkaloid containing plants whenI. purchasi — but notA. craccivora — was the producer. It is suggested that the chemical defense ofE. corallodendrum andS. junceum is exploited by polyphagous phytophages to reduce predation. In nature, population growth and density of four of the investigated homopterans are conspicuously high when they developed on the alkaloid containing plant species, and very low on non-alkaloid plants. The efficiency of their natural enemies may be reduced by sequestration of alkaloids (or other toxic plant compounds) or their transfer into excreted honeydew. Therefore it is assumed that a generalist phytophagous homopteran may be protected from its natural enemies, although at different rates of efficiency, if it can safely sequester the host allelochemical when it develops on toxic species within its host range.     

Sequestration of cucurbitacin analogs by New and Old World chrysomelid leaf beetles in the tribe Luperini

Summary Two South American polyphagous leaf beetles,Diabrotica speciosa andCerotoma arcuata, selectively accumulated the bitter tasting compound 23,24-dihydrocucurbitacin D in their body after ingesting root tissues of cucurbit plants. Similarly, three Asian Cucurbitaceae-feeding specialists in the genusAulacophora were found to sequester the same compound. Cucurbitacin analogs were shown to deter feeding by a bird predator, indicating an allomonal role for these compounds in cucurbitacin-associated chrysomelid leaf beetles both of New and Old Worlds. The strong affinity to cucurbitacins, selective sequestration of the analogs and consequent protection from predators suggested an ecological adaptation mechanism developed in common among these two geographically isolated subtribes in the Luperini.     

Effects of Controlled Fire and Livestock Grazing on Bird Communities in East African Savannas

Abstract: In East Africa fire and grazing by wild and domestic ungulates maintain savannas, and pastoralists historically set fires and herded livestock through the use of temporary corrals called bomas. In recent decades traditional pastoral practices have declined, and this may be affecting biodiversity. We investigated the effects of prescribed fires and bomas on savanna bird communities in East Africa during the first and second dry seasons of the year (respectively before and after the rains that mark the onset of breeding for most birds). We compared abundance, richness, and community composition on 9‐ha burned plots, recently abandoned bomas, and control plots in the undisturbed matrix habitat over a 3‐year period. Generally, recently burned areas and abandoned bomas attracted greater densities of birds and had different community assemblages than the surrounding matrix. The effects of disturbances were influenced by interactions between primary productivity, represented by the normalized difference vegetation index, and time. Bird densities were highest and a greater proportion of species was observed on burned plots in the months following the fires. Drought conditions equalized bird densities across treatments within 1 year, and individuals from a greater proportion of species were more commonly observed on abandoned bomas. Yearly fluctuations in abundance were less pronounced on bomas than on burns, which indicate that although fire may benefit birds in the short term, bomas may have a more‐lasting positive effect and provide resources during droughts. Several Palearctic migrants were attracted to burned plots regardless of rainfall, which indicates continued fire suppression may threaten their already‐declining populations. Most notably, the paucity of birds observed on the controls suggests that the current structure of the matrix developed as a result of fire suppression. Traditional pastoralism appears critical to the maintenance of avian diversity in these savannas.     

What Every Conservation Biologist Should Know about Economic Theory

Abstract: The last century has seen the ascendance of a core economic model, which we will refer to as Walrasian economics. This model is driven by the psychological assumptions that humans act only in a self‐referential and narrowly rational way and that production can be described as a self‐contained circular flow between firms and households. These assumptions have critical implications for the way economics is used to inform conservation biology. Yet the Walrasian model is inconsistent with a large body of empirical evidence about actual human behavior, and it violates a number of basic physical laws. Research in behavioral science and neuroscience shows that humans are uniquely social animals and not self‐centered rational economic beings. Economic production is subject to physical laws including the laws of thermodynamics and mass balance. In addition, some contemporary economic theory, spurred by exciting new research in human behavior and a wealth of data about the negative global impact of the human economy on natural systems, is moving toward a world view that places consumption and production squarely in its behavioral and biophysical context. We argue that abandoning the straightjacket of the Walrasian core is essential to further progress in understanding the complex, coupled interactions between the human economy and the natural world. We call for a new framework for economic theory and policy that is consistent with observed human behavior, recognizes the complex and frequently irreversible interaction between human and natural systems, and directly confronts the cumulative negative effects of the human economy on the Earth's life support systems. Biophysical economics and ecological economics are two emerging economic frameworks in this movement.     

Effects of Coffee Management on Deforestation Rates and Forest Integrity

Knowledge about how forest margins are utilized can be crucial for a general understanding of changes in forest cover, forest structure, and biodiversity across landscapes. We studied forest‐agriculture transitions in southwestern Ethiopia and hypothesized that the presence of coffee (Coffea arabica)decreases deforestation rates because of coffee's importance to local economies and its widespread occurrence in forests and forest margins. Using satellite images and elevation data, we compared changes in forest cover over 37 years (1973–2010) across elevations in 2 forest‐agriculture mosaic landscapes (1100 km² around Bonga and 3000 km² in Goma‐Gera). In the field in the Bonga area, we determined coffee cover and forest structure in 40 forest margins that differed in time since deforestation. Both the absolute and relative deforestation rates were lower at coffee‐growing elevations compared with at higher elevations (?10/20% vs. ?40/50% comparing relative rates at 1800 m asl and 2300–2500 m asl, respectively). Within the coffee‐growing elevation, the proportion of sites with high coffee cover (>20%) was significantly higher in stable margins (42% of sites that had been in the same location for the entire period) than in recently changed margins (0% of sites where expansion of annual crops had changed the margin). Disturbance level and forest structure did not differ between sites with 30% or 3% coffee. However, a growing body of literature on gradients of coffee management in Ethiopia reports coffee's negative effects on abundances of forest‐specialist species. Even if the presence of coffee slows down the conversion of forest to annual‐crop agriculture, there is a risk that an intensification of coffee management will still threaten forest biodiversity, including the genetic diversity of wild coffee. Conservation policy for Ethiopian forests thus needs to develop strategies that acknowledge that forests without coffee production may have higher deforestation risks than forests with coffee production and that forests with coffee production often have lower biodiversity value. Efectos de la Administración Cafetalera sobre las Tasas de Deforestación y la Integridad de los Bosques     

Globalization of the Cashmere Market and the Decline of Large Mammals in Central Asia

As drivers of terrestrial ecosystems, humans have replaced large carnivores in most areas, and human influence not only exerts striking ecological pressures on biodiversity at local scales but also has indirect effects in distant corners of the world. We suggest that the multibillion dollar cashmere industry creates economic motivations that link western fashion preferences for cashmere to land use in Central Asia. This penchant for stylish clothing, in turn, encourages herders to increase livestock production which affects persistence of over 6 endangered large mammals in these remote, arid ecosystems. We hypothesized that global trade in cashmere has strong negative effects on native large mammals of deserts and grassland where cashmere‐producing goats are raised. We used time series data, ecological snapshots of the biomass of native and domestic ungulates, and ecologically and behaviorally based fieldwork to test our hypothesis. In Mongolia increases in domestic goat production were associated with a 3‐fold increase in local profits for herders coexisting with endangered saiga (Saiga tatarica).That increasing domestic grazing pressure carries fitness consequences was inferred on the basis of an approximately 4‐fold difference in juvenile recruitment among blue sheep (Pseudois nayaur)in trans‐Himalayan India. Across 7 study areas in Mongolia, India, and China's Tibetan Plateau, native ungulate biomass is now <5% that of domestic species. Such trends suggest ecosystem degradation and decreased capacity for the persistence of native species, including at least 8 Asian endemic species: saiga, chiru (Pantholops hodgsoni), Bactrian camel (Camelus bactrianus), snow leopard(Panthera uncia), khulan(Equus hemionus), kiang (E. kiang), takhi (E. przewalski), and wild yak (Bos mutus). Our results suggest striking yet indirect and unintended actions that link trophic‐level effects to markets induced by the trade for cashmere. Globalización del Mercado de Cachemira y la Declinación de Mamíferos Mayores en Asia Central     

The lichen-rich coastal heath vegetation on the isle of Anholt, Denmark — conservation and management

The high conservational value of the lichen-rich vegetation and landscape of the marine foreland Ørkenen on the isle of Anholt is treated from a Danish as well as a European perspective. The sensitivity of the lichen-rich vegetation to physical disturbance is emphasized. The impact of invasive species such asPinus mugo as well as the effect of atmospheric deposition of nutrients on the heaths at Anholt is described. Considerations related to the development of a management plan for Ørkenen are presented.     

Behavior and ecology of Old World Luperini beetles of the genusAulacophora (Coleoptera: Chrysomelidae)

Summary The attraction of Old World leaf beetles in the genusAulacophora to kairomones and parakairomones which are effective lures for New WorldDiabrotica andAcalymma were investigated. Beetles captured on sticky traps baited with single and multicomponent lures were no different from the control traps for two species ofAulacophora. Yellow colored traps and squash blossoms are attractive toAulacophora beetles which detect sub-microgram quantities of cucurbitacins on silica gel. Leaf feeding behavior and flight activity data are correlated with varietal preference of threeAulacophora species. The common response byDiabrotica andAulacophora to cucurbitacins reinforces the two groups' coevolutionary association with the Cucurbitaceae. The apparent lack of a common response toCucurbita blossom volatiles suggests recent evolutionary pathways are substantially different for these two groups of beetles.     

Use of stochastic patch occupancy models in the California red-legged frog for Bayesian inference regarding past events and future persistence

Assessing causes of population decline is critically important to management of threatened species. Stochastic patch occupancy models (SPOMs) are popular tools for examining spatial and temporal dynamics of populations when presence–absence data in multiple habitat patches are available. We developed a Bayesian Markov chain method that extends existing SPOMs by focusing on past environmental changes that may have altered occupancy patterns prior to the beginning of data collection. Using occupancy data from 3 creeks, we applied the method to assess 2 hypothesized causes of population decline—in situ die-off and residual impact of past source population loss—in the California red-legged frog. Despite having no data for the 20–30 years between the hypothetical event leading to population decline and the first data collected, we were able to discriminate among hypotheses, finding evidence that in situ die-off increased in 2 of the creeks. Although the creeks had comparable numbers of occupied segments, owing to different extinction–colonization dynamics, our model predicted an 8-fold difference in persistence probabilities of their populations to 2030. Adding a source population led to a greater predicted persistence probability than did decreasing the in situ die-off, emphasizing that reversing the deleterious impacts of a disturbance may not be the most efficient management strategy. We expect our method will be useful for studying dynamics and evaluating management strategies of many species.