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NILS O. L. CARLSSON HELEN BUSTAMANTE DAVID L. STRAYER MICHAEL L. PACE 《Freshwater Biology》2011,56(8):1630-1637
1. Abundant native predators, parasites and pathogens that switch to consuming a hyper‐successful exotic species may be able to control the invasive population. Native predators may, however, need time to adapt to feed effectively on an exotic resource. In this case, mortality on an exotic population from native predators could increase over time even without a numerical increase in the predator population. 2. We measured mortality of zebra mussels (Dreissena polymorpha) in the Hudson River both in controls open to predation and in exclosures that excluded large predators to estimate mortality of zebra mussels from large predators and other causes. 3. We found that predation by the blue crab (Callinectes sapidus), and perhaps other predators, causes high mortality on zebra mussels in the Hudson River estuary. This predation apparently led to increased mortality and altered population structure in the invader over time. 4. Long‐term data from the Hudson River suggest that components of the invaded ecosystem, like rotifers, are recovering through predator‐caused release from zebra mussel grazing. Increased mortality on hyper‐successful exotic populations over time may be a common phenomenon with both ecological and management implications. 相似文献
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Tim M. Blackburn Phillip Cassey Karl L. Evans Kevin J. Gaston Richard P. Duncan 《Journal of Biogeography》2009,36(8):1613-1614
A recent paper by Karels et al ., 'The biogeography of avian extinctions on oceanic islands' ( Journal of Biogeography , 2008, 35 , 1106–1111), uses structural equation modelling to assess the causes of the number of island bird species driven extinct in the historical period. Here, we critically assess the conclusions of the paper and argue that it does not provide the new insights into the causes of extinction in island birds that its authors claim. 相似文献
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As a rule, N-supply of mature Ardenne forest ecosystems is satisfactory. Mineralization rates of soil organic matter are generally high and nitrogen is not a frequent nor an important growth limiting factor. Light N-deficiency is likely to depend on unsatisfactory root absorbing power in very acid soils with dysmoder humus. For other major elements, especially for Mg, Ca and P, near optimal nutrition is rarely observed.During the late sixties, fertilizer experiments have shown that nutrition equilibrium of stands growing on acid soils, poor in exchangeable Mg, is very sensitive to artificial NH4-addition. Mg-deficiency symptoms have been induced. The present continuing atmospheric NH4 input is believed to produce similar but lasting nutritional stress which might be accentuated by additional acidity generated during nitrification of excess NH4. Evolving Mg deficiency leads to trees' death and developing forest decline is likely to enhance N-output under NO3-form.Awaiting adequate air purification, fertilizing should restore nutrition equilibrium in order to save damaged stands, to slow down soil acidification and to incorporate excess atmospheric N-input into improved biomass production. 相似文献
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I pose eight questions central to understanding how biological invasions affect ecosystems, assess progress towards answering those questions and suggest ways in which progress might be made. The questions concern the frequency with which invasions affect ecosystems; the circumstances under which ecosystem change is most likely; the functions that are most often affected by invaders; the relationships between changes to ecosystems, communities, and populations; the long-term responses of ecosystems to invasions; interactions between biological invasions and other anthropogenic activities and the difficulty of managing undesirable impacts of non-native species. Some questions have been answered satisfactorily, others require more data and thought, and others might benefit from being reformulated or abandoned. Actions that might speed progress include careful development of trait-based approaches; strategic collection and publication of new data, including more frequent publication of negative results; replacement of expert opinion with hard data where needed; careful consideration of whether questions really need to be answered, especially in cases where answers are being provided for managers and policy-makers; explicit attention to and testing of the domains of theories; integrating invasions better into an ecosystem context; and remembering that our predictive ability is limited and will remain so for the foreseeable future. 相似文献
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Interactions between dung beetles and vertebrate dung are intimately linked to a suite of ecosystem functions in tropical forests. We show that the trapping method and the type of dung used affect the suite of beetles captured, with the potential to influence the outcome of experiments linking functions to interactions. 相似文献
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In species‐rich ecosystems, such as subtropical and tropical forests, higher trophic level interactions are key mediators of ecosystem functioning. Plant species loss may alter these interactions, but the effects of plant diversity might be modified by intraguild interactions, particularly among predators. We analyzed the relationships between spiders and ants, two dominant predatory arthropod taxa, on tree saplings across a gradient from medium to high woody plant species richness in a subtropical forest in Southeast China. Neither ant nor spider total biomass was significantly related to plant species richness. By contrast, the biomass distribution of web‐building and hunting spiders changed and spider family richness increased in the presence of ants, resulting in more web builder‐dominated assemblages. However, these relationships depended on the plant communities, and were stronger in plots with higher plant species richness. Our results indicate that in addition to potential effects of ants on hunting spiders in particular, ants could indirectly influence intraguild interactions within spider assemblages. The observed shifts in the spider assemblages with increasing ant presence and plant species richness may have functional consequences, as web‐building and hunting spiders have distinct prey spectra. The relationships among ants, spiders, and plant species richness might contribute to explaining the non‐significant relationship between the overall effects of predators and plant diversity previously observed in the same forest plots. Our findings thus give insight into the complexity of biotic interactions in such species‐rich ecosystems. 相似文献
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Rosemary Hohnen Katherine D. Tuft Sarah Legge Ian J. Radford Scott Carver Christopher N. Johnson 《Austral ecology》2015,40(8):941-952
Fire regimes are changing throughout the world. Changed fire patterns across northern Australian savannas have been proposed as a factor contributing to recent declines of small‐ and medium‐sized mammals. Despite this, few studies have examined the mechanisms that underpin how species use habitat in fire‐affected landscapes. We determined the habitats and resources important to the declining golden‐backed tree‐rat (Mesembriomys macrurus) in landscapes partially burnt by recent intense fire. We aimed to (i) compare the relative use of rainforest and savanna habitats; (ii) examine the effect of fire history on use of savanna habitats; and (iii) identify key foraging and denning resources. Habitat selection was examined by comparing the availability of eight habitat types around real (used) and generated (available) location points. Individuals used a range of habitats, but consistently selected long unburnt rainforest in preference to recently burnt savanna (1–12 months post‐fire); however, recently burnt savanna was used in preference to long unburnt savanna. Tree‐rats foraged in Terminalia hadleyana, Planchonia rupestris, Celtis philippensis and Owenia vernicosa, tree species that are found in a variety of habitat types. Individuals used a range of den sites, including cliffs, trees, logs, scree and stags found throughout the study area. Although multiple factors may have led to the decline of Mes. macrurus across its range, these results are consistent with the idea that changes in the savanna structure as a consequence of contemporary fire patterns could also have a role. The continued persistence of Mes. macrurus in the northwest Kimberley may be supported by land management strategies that conserve fruiting and hollow‐bearing trees, and maintain the availability of fire‐sensitive vegetation types. 相似文献
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Large mammals are vulnerable to extinction, and respond directly to ecological gradients within the forest and to the intensity of forest product use by humans. In this study, we evaluated the effects of differences in forest structure and human occupation history on the composition of medium and large‐sized mammal assemblages of the terra‐firme forests of the Anavilhanas National Park, one of the most oligotrophic Amazonian ecosystems. Mammal surveys were conducted along 11 linear transects of 4 km, six of which were located in areas once inhabited by people and managed until the year that the park was created (over 30 years ago), and five in areas that were not inhabited at that time. We detected 469 individuals of 26 species during diurnal and nocturnal sampling, and 11 additional species outside transects. Human occupation history was strongly related to forest structure components. Fruit biomass, canopy cover and tree size were strongly associated with uninhabited areas, and influenced the structure of mammal assemblages. A direct relationship between diet category and species size was observed. Large frugivore‐herbivores and carnivores were more closely associated with areas with more fruit, larger trees and greater canopy cover. In contrast, small arboreal frugivore‐omnivores associated more closely with open canopy and smaller trees. Our study indicated that the effects of human occupation history on forest structure are still evident three decades after the removal of local people from the park. This long‐term effect can be explained by the low resilience of the Anavilhanas environments, demonstrating the fragility of mammal assemblages in face of anthropogenic variation in forest structure in the oligotrophic ecosystems of the Negro River basin. 相似文献
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One of the values of biodiversity is that it may provide 'biological insurance' for services currently rendered by domesticated species or technology. We used crop pollination as a model system, and investigated whether the loss of a domesticated pollinator (the honey bee) could be compensated for by native, wild bee species. We measured pollination provided to watermelon crops at 23 farms in New Jersey and Pennsylvania, USA, and used a simulation model to separate the pollen provided by honey bees and native bees. Simulation results predict that native bees alone provide sufficient pollination at > 90% of the farms studied. Furthermore, empirical total pollen deposition at flowers was strongly, significantly correlated with native bee visitation but not with honey bee visitation. The honey bee is currently undergoing extensive die-offs because of Colony Collapse Disorder. We predict that in our region native bees will buffer potential declines in agricultural production because of honey bee losses. 相似文献
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Bronwyn A. Hradsky John Loschiavo Marney Hradsky Julian Di Stefano 《Austral ecology》2015,40(5):611-624
The expansion (or encroachment) of shrubs in forests and woodlands is generally considered a serious threat to biodiversity. The effects of shrub expansion on forest fauna, however, are poorly understood and likely to depend on the availability of key resources in shrub‐encroached forest. Coranderrk Bushland, like many conservation reserves in south‐eastern Australia, is considered threatened by the spread of an indigenous shrub. We investigated the associations between cover of Yarra burgan (Kunzea leptospermoides (Myrtaceae)), vegetation structure and the occurrence of terrestrial native mammals within the reserve, basing our predictions on prior knowledge of burgan growth habits and fauna habitat preferences. We quantified burgan cover and other potentially important habitat attributes using structure surveys, and used motion‐sensing cameras to detect terrestrial mammals. Dense burgan cover was associated with less grass, a sparser understorey, and more cryptogams, dead trees and coarse woody debris. However, there was no evidence that these changes negatively affected native mammals: burgan cover had little influence on the occurrence of any species except swamp wallabies (Wallabia bicolor), which occurred in all areas of the reserve but shifted from sites with high burgan cover during the day to sites with low cover at night. Our findings contrast with those from grassland shrub‐expansion studies, where fauna generally show strong responses to shrub cover. The effects of shrub expansion on forest fauna may be mitigated by the greater pre‐existing structural diversity in forests or the longer time required for structural changes to be fully realized. The large quantities of dead wood in areas with high shrub cover may also provide compensatory resources for small mammals, while the proximity to un‐encroached areas may enable large herbivores to move between dense shelter and forage. Shrub‐encroached forests clearly provide resources for some native fauna, and management strategies need to consider the potential impacts of shrub removal on these taxa. 相似文献
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利用样方法调查了南京市不同生境下外来杂草的种类、盖度、密度情况,探讨了不同生境中外来杂草对杂草群落的影响,同时分析了10种主要外来杂草和本地伴生种的生态位特点.结果表明,南京市春季外来杂草有36种,在74个样点中外来杂草出现的频率达到98.65%;外来杂草的入侵对生物多样性有不利影响;外来杂草平均优势度在不同生境中大小次序为:水边>菜地>荒地>路旁>景区>田埂>草坪>果茶园>墙缝>农田>宅旁>山坡.生态位的研究结果表明:野塘蒿 Conyzabonariensis L. Cronq. 、野老鹳草 GeraniumcarolinianumL. 和阿拉伯婆婆纳 VeronicapersicaPoir. 是生态位宽度最高的外来杂草,其入侵性最强;具有较高生态位宽度的外来杂草与其它杂草的生态位重叠较大,具有相似形态特征的杂草间的生态位重叠较大. 相似文献
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为明确北京小西山大型真菌多样性现状,为该区森林生态系统经营提供数据支持和依据,本研究采用野外调查和文献查询相结合的方法进行大型真菌多样性研究。共采集小西山大型真菌共2门5纲10目33科65属148种。大型真菌主要优势科有6个,依次为白蘑科(Tricholomataceae)、蘑菇科(Agaricaceae)、多孔菌科(Polyporaceae)、鬼伞科(Psathyrellaceae)、红菇科(Russula)、牛肝菌科(Boletaceae),共包括99个种,约占总种数的36.5%。现有大型真菌生态习性多样,木生、土生和共生类型均有分布,尤以木生和土生真菌为多。区系分布以世界广布属和温带分布属为主,极少其他成分。分布特征与栎类、油松等为代表的典型林分类型及海拔密切相关。研究结果表明真菌生物多样性调查及其保护、利用应与森林经营相结合,以森林生态系统经营的理念为指导,从林分类型、立地条件、人为干扰特征与大型真菌的关联性方面开展定量研究,为森林的可持续经营提供了宝贵的数据基础和研究思路。 相似文献
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基于景观生态学中结构与功能相互依存的理念 ,选定小尺度森林为研究对象 ,根据生态系统内部结构特性 ,确立森林生态功能的空间定位 ,以提高森林生态系统的功能与价值。研究首先基于森林生态系统具有生物生产、环境服务及文化支持等基本功能 ,提出上述功能应通过森林生产、教学实习、科学研究、休闲游憩和生态保护等功能区加以体现。后依据研究区环境特征进行影响因子分析 ,结合景观生态与生态规划相关理论 ,构建森林生态功能分区方案。在案例实践中 ,选择台湾惠荪林场进行研究 ,配合研究区现况 ,期望通过功能区与结构的空间调整 ,达到服务功能的优化。 相似文献
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以北京市森林资源第6次二类调查数据为基础,采用区域水量平衡法和土壤蓄水能力评估了森林水源涵养的功能,并重点分析了不同类型和区位条件下森林涵养水源功能的差异。结果表明：2004年北京市森林生态系统涵养水源1.26×10^9m^3;其中,怀柔区、延庆县、密云县、门头沟区和房山区的森林是水源涵养功能的主要贡献者（累积贡献率63.3%）;从森林类型来看,阔叶林和灌木林是水源涵养的主体（累积贡献率80.8%）;位于不同海拔高度的森林对水源涵养功能的贡献不同,其中位于海拔〈100m、100～500m和500～800m森林的贡献率分别为29%、30.7%和23.3%;而且位于不同坡位的森林涵养水源的贡献也不同,其中平地和全坡的森林最高,贡献率分别为37.12%和40.7%。 相似文献
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1. Hyper-successful exotic species can both displace the native prey that formerly made up a native predator's diet and represent an abundant potential prey resource for native predators. Little is known about how this drastic change affects native predators, or their short- and long term potential to regulate the exotic species.
2. We compared zebra mussel consumption by pumpkinseed sunfish ( Lepomis gibbosus ), redbreast sunfish ( Lepomis auritus ) and rock bass ( Ambloplites rupestris ) from populations that were either previously exposed to zebra mussels or naive to them.
3. Fish from populations with longer exposure to zebra mussels consumed many more zebra mussels than fish from populations with shorter or no previous exposure to zebra mussels.
4. Our experiment does not allow us to identify the mechanisms that underlie the patterns we found, but we discuss several plausible scenarios and their ecological implications.
5. Predator adaptation to exotic prey may be an important but overlooked factor in invasion biology. The initial response to exotic prey by a native predator may be a poor estimate of its ability to present biotic resistance to the invasion over the long term. 相似文献
2. We compared zebra mussel consumption by pumpkinseed sunfish ( Lepomis gibbosus ), redbreast sunfish ( Lepomis auritus ) and rock bass ( Ambloplites rupestris ) from populations that were either previously exposed to zebra mussels or naive to them.
3. Fish from populations with longer exposure to zebra mussels consumed many more zebra mussels than fish from populations with shorter or no previous exposure to zebra mussels.
4. Our experiment does not allow us to identify the mechanisms that underlie the patterns we found, but we discuss several plausible scenarios and their ecological implications.
5. Predator adaptation to exotic prey may be an important but overlooked factor in invasion biology. The initial response to exotic prey by a native predator may be a poor estimate of its ability to present biotic resistance to the invasion over the long term. 相似文献
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MARK C. VANDERWEL JAY R. MALCOLM JOHN P. CASPERSEN MARK A. NEWMAN 《The Journal of wildlife management》2010,74(7):1492-1501
Abstract: To provide habitat for late-successional wildlife species, new ecosystem-based forest management practices aim to retain elements of complex stand structure, including live residual trees, dead wood legacies, and advanced regeneration, within managed stands. Predicting the effectiveness of these strategies is a challenge for species whose habitat relationships may involve multiple factors and can vary among sites. For 2 years, we live-trapped a common, late-successional microtine rodent, the southern red-backed vole (Myodes [formerly Clethrionomys] gapperi), in 40 1.4-ha boreal mixedwood sites in Ontario, Canada. Using a neighborhood-scale modeling approach, we related red-backed vole capture locations to spatially referenced measures of overstory trees, shrubs and saplings, downed woody debris (DWD), and forest floor substrate. We further assessed how associations with these features varied with availability of the features within a site and as a function of stand management history. In spring, red-backed voles were associated with trap stations that had, within a 26-m radius, a dense shrub layer, abundant late-decay DWD, coniferous understory and litter, and possibly, understory vegetation associated with moist conditions. Positive associations with shrub cover, late-decay DWD, and a moisture-associated understory were most apparent in sites in which these elements were scarce (e.g., <1,500 stems/ha of hardwood saplings and short shrubs; <0.8% projected ground cover of late-decay DWD). The importance of late-decay DWD; shade-tolerant, coniferous understory composition; and substrate varied depending on a site's management history, with each feature having a strong positive effect in 47–64-year-old stands that were harvested using horse skidding and weaker effects in both 31–40-year-old stands that were clearcut with mechanical skidding and >80-year-old fire-origin stands. Our models of fine-scale habitat relationships for red-backed voles may be useful in establishing structural retention guidelines suitable for wildlife species dependent on late-successional habitat structure. In this regard, retaining abundant DWD and 10–30% live trees at harvest may be effective management strategies for providing favorable habitat conditions at localized scales. 相似文献
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Urban landscapes often expose wildlife populations to enhanced edge effects where the biotic and abiotic attributes of native ecosystems have been significantly altered. While some species may respond favourably to edges, there are likely to be varying negative consequences for many forest‐dependent species. In particular, marsupial gliders are influenced by changes in forest composition and structure near edges due to highly specific feeding and nesting requirements, and a high reliance on tree cover to traverse a landscape. We addressed this problem using the squirrel glider (Petaurus norfolcensis) in the fragmented urban landscape of southeast Queensland, Australia. Analysis of variance was applied to determine differences in habitat resources and structure in relation to glider presence and trap success rates in forest fragment interiors compared with road (minor & major) and residential edge habitats. We postulate that an increased presence of squirrel gliders in sites adjacent to minor road and residential edges may be due to the availability of additional resources and/or varying dispersal opportunities. Conversely, forest fragment interiors contain a higher abundance of nest hollows and large trees, together with a greater floristic species richness providing more reliable seasonal foraging sources, which may explain the greater trap success rates of squirrel gliders in these sites. We conclude that while forest fragment interiors provide habitat suitable for year‐round use by greater numbers of squirrel gliders, the conservation value of some edge habitats that provide additional resources and dispersal opportunities should not be underestimated for forest‐dependent mammals; however, each edge type must be assessed individually. 相似文献