免耕稻-鸭复合系统减少甲烷排放及其机理研究

以免耕不养鸭和翻耕不养鸭稻田为参照,研究了免耕稻-鸭复合系统中甲烷排放的日变化和季节变化以及稻-鸭复合系统中土壤氧化还原特性对甲烷排放的影响。结果表明:稻田甲烷排放通量日变化与日气温变化基本趋于一致。在水稻分蘖盛期和孕穗期,免耕养鸭稻田甲烷排放通量明显低于免耕不养鸭和翻耕不养鸭稻田, 3者之间甲烷排放通量大小差异白天明显,夜间较小。在水稻分蘖盛期、孕穗期和齐穗期,免耕养鸭稻田水中溶解氧含量比免耕不养鸭和翻耕不养鸭稻田提高38. 4% ~44. 7%。由于鸭子的活动,免耕养鸭稻田的氧化还原电位分别比免耕不养鸭和翻耕不养鸭稻田高11和18mV。而翻耕不养鸭稻田的还原物质总量分别是免耕养鸭稻田和免耕不养鸭稻田的4. 17~12. 34倍和3. 26~7. 02倍,其亚铁离子含量也明显高于后2者,表明翻耕使土壤还原程度增强,进而促进了稻田甲烷的排放。相关分析表明,免耕养鸭稻田氧化还原电位与还原物质总量、活性还原物质总量和亚铁离子含量呈极显著负相关,也与稻田甲烷排放通量呈负相关,但未达显著水平。     

免耕稻-鸭复合系统减少甲烷排放及其机理研究

以免耕不养鸭和翻耕不养鸭稻田为参照，研究了免耕稻-鸭复合系统中甲烷排放的日变化和季节变化以及稻-鸭复合系统中土壤氧化还原特性对甲烷排放的影响。结果表明：稻田甲烷排放通量日变化与日气温变化基本趋于一致。在水稻分蘖盛期和孕穗期，免耕养鸭稻田甲烷排放通量明显低于免耕不养鸭和翻耕不养鸭稻田，3者之间甲烷排放通量大小差异白天明显，夜间较小。在水稻分蘖盛期、孕穗期和齐穗期，免耕养鸭稻田水中溶解氧含量比免耕不养鸭和翻耕不养鸭稻田提高38．4％～44．7％。由于鸭子的活动，免耕养鸭稻田的氧化还原电位分别比免耕不养鸭和翻耕不养鸭稻田高11和18mV。而翻耕不养鸭稻田的还原物质总量分别是免耕养鸭稻田和免耕不养鸭稻田的4．17～12．34倍和3．26～7．02倍，其亚铁离子含量也明显高于后2者，表明翻耕使土壤还原程度增强，进而促进了稻田甲烷的排放。相关分析表明，免耕养鸭稻田氧化还原电位与还原物质总量、活性还原物质总量和亚铁离子含量呈极显著负相关，也与稻田甲烷排放通量呈负相关，但未达显著水平。     

湿地稻-鸭复合生态系统综合效益研究

2000年3月至2001年10月在湖南长沙进行了湿地稻-鸭复合生态系统综合效益的小区试验。结果表明,实行稻-鸭生态种养显著降低稻田甲烷排放量,与常规稻田相比,甲烷排放总量在早稻田与晚稻田分别降低44.2%和40.7%。各处理晚稻田甲烷排放总量高于早稻田甲烷排放总量。养鸭稻田与常规稻田相比,土壤肥力都有所增加,土壤容重降低,>0.25mm团聚体增加2.65～3.12百分点,土壤结构系数增加2.56～6.63百分点。同时,稻田土壤氧化还原状况也得到明显改善。湿地稻-鸭复合生态系统直接的经济效益也远高于常规稻田。     

浅论稻田甲烷的产生和排放

目前的研究结果表明,我国稻田甲烷排放通量大约在7.8—60mg/m~2·h。稻田甲烷的排放包含着甲烷在水田土壤中的生成和从土壤向大气释放这样两个过程。前者是通过土壤中微生物活动分解复杂的有机物质,在渍水还原条件(氧化还原电位低于-200mv)下,由产甲烷菌最后转化形成甲烷;后者主要是通过水稻植株向大气释放,只有少量通过气泡或分子扩散从水田土壤通过田面水层向大气排放。显然,稻田甲烷的生成、排放是一个以生物学过程为中心,并与土壤环境、土表水层和大气环境的一些物理、化学条件密切相关的过程。土壤温度、pH值、水稻品种的生物学特性及稻田的水浆管理、施肥措施等等都会影响稻田甲烷的排放。只有研究并掌握稻田甲烷排放的机理及其影响因素,才能真正做到在争取水稻优质、高产的同时,抑制或减少甲烷的排放。     

青海湖高寒藏嵩草湿草甸湿地生态系统CO_2通量变化特征

基于涡度相关系统对青海湖藏嵩草湿草甸湿地生态系统CO_2通量变化特征及其影响因子进行研究。结果表明,青海湖藏嵩草湿草甸湿地生态系统CO_2通量具有明显的日变化和月变化特征。生长季表现为CO_2的净吸收,其吸收峰值出现在12:30—15:00之间,最大值为0.42 mg·m~(-2)·s~(-1),排放峰值出现在20:00—22:30之间,最大值为0.24 mg·m~(-2)·s~(-1)。非生长季日变化较小,总体表现为CO_2的净排放,除了11月,其他月份白天CO_2排放通量都明显大于夜间。2015年青海湖高寒藏嵩草湿草甸湿地生态系统全年净生态系统CO_2交换量为54.55 g·m~(-2),表现为碳源。路径分析表明,土壤温度、光合有效辐射和饱和水汽压差是影响CO_2通量日交换大小的主要控制因子。     

互花米草入侵盐沼湿地CH_4和N_2O排放日变化特征研究

甲烷(CH4)和氧化亚氮(N2O)是导致全球气候变暖的2种重要温室气体,探索其源汇及地域排放特征一直是全球变化研究领域的核心内容。CH4和N2O通量的日变化研究是正确估算大时间尺度下CH4和N2O排放量的基础。利用静态箱法原位观测了江苏沿海芦苇(Phragmites australis)、盐蒿(Suada salsa)、光滩、水面以及互花米草(Spartina alterniflora)入侵湿地CH4和N2O排放的日变化特征。结果表明,1)互花米草湿地地上部生物量为1.70 kg·m-2,土壤有机碳质量分数为13.55 g·kg-1;分别是芦苇和盐蒿湿地的2.50~3.43和2.15~4.15倍。2)互花米草和芦苇湿地土壤10 cm处氧化还原电位(Eh)有明显日变化,最低值出现在3:00,最高值出现在12:00;光滩和盐蒿湿地没有明显的日变化。3)互花米草湿地CH4日平均排放通量为0.52 mg·m-2·h-1,是其他湿地的2.12~6.40倍;N2O日平均通量为-3.24μg·m-2·h-1,显著低于盐蒿湿地、光滩和水面(P0.05)。互花米草和芦苇湿地CH4排放通量最高值(0.73 mg·m-2·h-1和0.30 mg·m-2·h-1)出现在15:00,最低值(0.37mg·m-2·h-1和0.17 mg·m-2·h-1)出现在3:00,均与土壤孔隙水中CH4浓度呈显著负相关(P0.05)。互花米草湿地CH4排放通量与10 cm土温、Eh和生态系统CO2净交换量(NEE)显著正相关(P0.05)。互花米草和芦苇湿地N2O通量9:00-18:00为负值,21:00—6:00为正值,均与NEE呈显著负相关(P0.05)。盐蒿湿地、光滩和水面CH4和N2O排放通量没有明显日变化特征。互花米草入侵提高了沿海湿地CH4排放,但降低了N2O排放,植物对CH4传输作用以及向根际传输O2和易分解有机物是导致互花米草和芦苇湿地CH4和N2O排放表现出日变化特征的原因。     

互花米草入侵盐沼湿地CH4和N2O排放日变化特征研究

甲烷（CH4）和氧化亚氮（N2O）是导致全球气候变暖的2种重要温室气体，探索其源汇及地域排放特征一直是全球变化研究领域的核心内容。CH4和N2O通量的日变化研究是正确估算大时间尺度下CH4和N2O排放量的基础。利用静态箱法原位观测了江苏沿海芦苇（Phragmites australis）、盐蒿（Suada salsa）、光滩、水面以及互花米草（Spartina alterniflora）入侵湿地CH4和N2O排放的日变化特征。结果表明，1）互花米草湿地地上部生物量为1.70 kg·m^-2，土壤有机碳质量分数为13.55 g·kg^-1；分别是芦苇和盐蒿湿地的2.50-3.43和2.15-4.15倍。2）互花米草和芦苇湿地土壤10 cm处氧化还原电位（Eh）有明显日变化，最低值出现在3：00，最高值出现在12：00；光滩和盐蒿湿地没有明显的日变化。3）互花米草湿地 CH4日平均排放通量为0.52 mg·m^-2·h^-1，是其他湿地的2.12-6.40倍；N2O日平均通量为-3.24μg·m^-2·h^-1，显著低于盐蒿湿地、光滩和水面（P＜0.05）。互花米草和芦苇湿地CH4排放通量最高值（0.73 mg·m^-2·h^-1和0.30 mg·m^-2·h^-1）出现在15：00，最低值（0.37 mg·m^-2·h^-1和0.17 mg·m^-2·h^-1）出现在3：00，均与土壤孔隙水中CH4浓度呈显著负相关（P＜0.05）。互花米草湿地CH4排放通量与10 cm土温、Eh和生态系统CO2净交换量（NEE）显著正相关（P＜0.05）。互花米草和芦苇湿地N2O通量9：00-18：00为负值，21：00—6：00为正值，均与NEE呈显著负相关（P＜0.05）。盐蒿湿地、光滩和水面CH4和N2O排放通量没有明显日变化特征。互花米草入侵提高了沿海湿地CH4排放，但降低了N2O排放，植物对CH4传输作用以及向根际传输O2和易分解有机物是导致互花米草和芦苇湿地CH4和N2O排放表现出日变化特征的原因。     

种稻盆钵土壤甲烷排放通量变化的研究

通过温室盆栽试验，研究了不同冬作处理时后茬水稻生长期甲烷排放通量及土壤温度、土壤Ｅｈ的日变化规律。结果表明：连续晴天甲烷排放通量和土壤温度存在明显的昼夜变化，最大值出现在下午４时左右，最小值出现在凌晨４时左右，符合余弦函数变化规律；连续阴雨天甲烷排放通量有逐日降低的趋势，但其昼夜变化缺乏规律性。种稻盆钵土壤甲烷排放通量昼夜变化主要受０～１０ｃｍ深土壤温度的影响，而与土壤氧化还原电位无关。     

稻田甲烷排放通量与农业管理措施的关系

1990至1992年对北京地区的麦后稻区及单季稻区进行了三年的稻田甲烷排放通量的测定,麦后稻区的甲烷排放通量约17.5mg/m~2·h;单季稻小区约在8.5-10mg/m~2·h。有机底肥的用量是影响甲烷排放通量的首要因素,旱直播及仅使用化肥可降低甲烷排放通量。在一定量有机底肥的条件下,采用间歇灌溉的方法既可保持或提高水稻的产量,又可抑制或降低甲烷的排放通量,但也观测到干干湿湿的状态下温室气体N_2O的排放通量有所增加。     

不同耕作制度对南方稻田甲烷排放的影响

以南方稻田温室气体甲烷排放为研究对象,选取冬季休闲和种植绿肥作物紫云英(AstragalussinicusL.)两种主要模式,在早稻(OryzasativaL.)移栽之前进行旋耕和翻耕两种处理,以全年休闲为空白对照,利用静态箱法测定甲烷排放通量。结果表明,甲烷排放在水稻抽穗期达到极大值,至收获甲烷排放呈减少趋势,以无稻全年休闲区甲烷排放通量最低,在抽穗至收获阶段平均排放速率为3.43mg·m-2·h-1,冬闲及冬季种植紫云英处理分别比无稻休闲区排放通量高114.3%和420.3%;甲烷浓度具有强烈的空间异质性,地表以上50cm空间内,早稻抽穗至成熟阶段甲烷浓度是大气甲烷浓度的35.2倍;稻田甲烷高浓度低排放速率以及低浓度高排放速率现象表明,甲烷排放速率与其浓度之间具有非一致性。     

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.     

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     

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.     

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.