排序方式: 共有39条查询结果,搜索用时 15 毫秒
1.
Abstract: State wildlife agencies often use input obtained through public meetings to develop management policies. Because public meetings can be dominated by single stakeholder groups, these policies may not reflect the attitudes of new wildlife stakeholders. In 2000 the Utah Wildlife Board, after a series of public meetings, adopted a statewide policy for winter-feeding mule deer (Odocoileus hemionus). The policy was implemented by the Utah Division of Wildlife Resources from 2001 to 2007 in Cache County of northern Utah, USA. In 2007, we surveyed Utah households representing metropolitan, nonmetropolitan, and Cache County residents (n = 1,800) to evaluate whether the winter-feeding policy reflected the attitudes of all wildlife stakeholders. Survey respondents, regardless of residence strata, believed winterfeeding programs were essential for managing mule deer in Utah (χ26 = 7.02, P = 0.32). However, most respondents were reluctant to support feeding programs at the expense of habitat restoration projects (χ26 = 11.64, P = 0.07). Our results suggest that the winter-feeding policy represented the attitudes of the Utah residents surveyed, though few had participated in its development. Respondents' strong utilitarian attitudes toward wildlife (e.g., strong support for hunting and feeding) influenced those respondents' perceptions of the policy. Given the effects of increased urbanization on utilitarian attitudes toward wildlife in many parts of the United States, coupled with decreasing numbers of traditional wildlife stakeholders, state wildlife agencies should continually reevaluate their public involvement processes to ensure new wildlife stakeholders' attitudes and concerns are represented. 相似文献
2.
Abstract: During severe winters, mule deer (Odocoileus hemionus) concentrated on ranges in poor condition can experience high mortality. Winter-feeding programs have been implemented to mitigate this mortality. We studied effects on body condition, mortality, fawn production, and migration of mule deer following winter-feeding in the Cache-Wasatch Mountains of northern Utah, USA. Fed deer exhibited 12% higher live body-condition indices both years (main effect feed: F1,7.32 = 5.39, P = 0.052), lower mortality (33% vs. 55%: χ21= 4.58, P < 0.05), and produced more fawns (19 fawns:18 fed F vs. 11 fawns:12 nonfed F; t27.2 = 2.20, P < 0.036) than nonfed deer. Fed deer migrated later in spring 2004 (x̄ = 13 Apr) than nonfed deer (x̄ = 24 Mar; t34= 3.25, P = 0.003). Fed deer spent more time on winter range in 2003-2004 (x̄ = 157 d) than nonfed deer (x̄ = 121 d; t20 = 3.63, P = 0.002), and more time on winter range for both winters combined (fed deer x̄ = 321 d, nonfed deer x̄ = 257 d; t27 = 3.29, P = 0.003). Concomitantly, wildlife managers need to recognize that any possible benefits accrued to mule deer populations in terms of increased nutritional status as a result of winter-feeding programs may be mitigated by altered timing of migration and increased duration of use of seasonal ranges by fed deer. 相似文献
3.
Phytoplankton equilibrium phases during thermal stratification in a deep subtropical reservoir 总被引:3,自引:0,他引:3
VANESSA BECKER VERA LÚCIA M. HUSZAR LUIGI NASELLI-FLORES JUDIT PADISÁK 《Freshwater Biology》2008,53(5):952-963
1. Equilibrium and non-equilibrium hypotheses have often been used to explain observations in community ecology. Published case studies have demonstrated that steady state phytoplankton assemblages are more likely to occur in deep lakes than in shallow mixed ones.
2. Phytoplankton seasonal succession was studied by weekly sampling in Faxinal Reservoir (S Brazil), a subtropical deep, clear, warm monomictic and slightly eutrophic reservoir. This study demonstrated an alternation of steady and non-steady state phases of phytoplankton assemblages with different dominant species during the steady states.
3. During the studied period, three steady states were identified with different dominant algal species: Anabaena crassa (Cyanobacteria), Nephrocytium sp. (green algae) and Asterionella (diatoms).
4. Each steady state in Faxinal Reservoir developed under stratified conditions of the water column according to the predictions of the disturbance concepts. Apparently, the major forces driving the development and persistence of these steady-state phases were closely related to thermal stratification and its consequences.
5. This study is the first report on development of more than one steady state within a year in a stratified water body. The development of three steady states might be the result of the relatively long stratification period in the Faxinal Reservoir and to its unique geochemical features. 相似文献
2. Phytoplankton seasonal succession was studied by weekly sampling in Faxinal Reservoir (S Brazil), a subtropical deep, clear, warm monomictic and slightly eutrophic reservoir. This study demonstrated an alternation of steady and non-steady state phases of phytoplankton assemblages with different dominant species during the steady states.
3. During the studied period, three steady states were identified with different dominant algal species: Anabaena crassa (Cyanobacteria), Nephrocytium sp. (green algae) and Asterionella (diatoms).
4. Each steady state in Faxinal Reservoir developed under stratified conditions of the water column according to the predictions of the disturbance concepts. Apparently, the major forces driving the development and persistence of these steady-state phases were closely related to thermal stratification and its consequences.
5. This study is the first report on development of more than one steady state within a year in a stratified water body. The development of three steady states might be the result of the relatively long stratification period in the Faxinal Reservoir and to its unique geochemical features. 相似文献
4.
ESTEBAN FERNÁNDEZ‐JURICIC MEGAN D. GALL TRACY DOLAN VANESSA TISDALE GRAHAM R. MARTIN 《Ibis》2008,150(4):779-787
In birds, differences in the extent and position of the binocular visual field reflect adaptations to varying foraging strategies, and the extent of the lateral portion of the field may reflect anti‐predator strategies. The goal of this study was to describe and compare the visual fields of two ground‐foraging passerines, House Finch Carpodacus mexicanus and House Sparrow Passer domesticus. We found that both species have a binocular field type that is associated with the accurate control of bill position when pecking. Both species have eye movements of relatively large amplitude, which can produce substantial variations in the configuration of the binocular fields. We propose that in these ground foragers, their relatively wide binocular fields could function to increase foraging efficiency by locating multiple rather than single food items prior to pecking events. The lateral fields of both species are wide enough to facilitate the detection of predators or conspecifics while head‐down foraging. This suggests that foraging and scanning are not mutually exclusive activities in these species, as previously assumed. Furthermore, we found some slight, but significant, differences between species: House Sparrow binocular fields are both wider and vertically taller, and the blind area is wider than in House Finches. These differences may be related to variations in the degree of eye movements and position of the orbits in the skull. 相似文献
5.
CHRISTOPHER B. ANDERSON† GUILLERMO MARTÍNEZ PASTUR‡ MARÍA VANESSA LENCINAS‡ PETRA K. WALLEM§ MICHELLE C. MOORMAN†¶ AMY D. ROSEMOND 《Mammal Review》2009,39(1):33-52
- 1 Twenty‐five pairs of North American beavers Castor canadensis Kuhl were introduced to Tierra del Fuego Island in 1946. The population has expanded across the archipelago, arriving at the Chilean mainland by the mid‐1990s. Densities range principally between 0.5–2.05 colonies/km. They have an impact on between 30–50% of stream length and occupy 2–15% of landscape area with impoundments and meadows. Beaver impacts constitute the largest landscape‐level alteration in subantarctic forests since the last ice age.
- 2 The colonization pattern, colony densities and impacted area indicate that habitat in the austral archipelago is optimal for beaver invasion, due to low predator pressure and suitable food resources. Nothofagus pumilio forests are particularly appropriate habitat, but a more recent invasion is occurring in adjacent steppe ecosystems. Nonetheless, Nothofagus reproductive strategies are not well adapted to sustain high beaver population levels.
- 3 Our assessment shows that at the patch‐scale in stream and riparian ecosystems, the direction and magnitude of exotic beaver impacts are predictable from expectations derived from North American studies, relating ecosystem engineering with underlying ecological mechanisms such as the relationships of habitat heterogeneity and productivity on species richness and ecosystem function.
- 4 Based on data from the species' native and exotic range, our ability to predict the effects of beavers is based on: (i) understanding the ecological relationships of its engineering effects on habitat, trophic dynamics and disturbance regimes, and (ii) having an adequate comprehension of the landscape context and natural history of the ecosystem being engineered.
- 5 We conclude that beaver eradication strategies and subsequent ecosystem restoration efforts, currently being considered in southern Chile and Argentina, should focus on the ecology of native ecosystems rather than the biology of this invasive species per se. Furthermore, given the nature of the subantarctic landscape, streams will probably respond to restoration efforts more quickly than riparian ecosystems.
6.
A method was required for determining the effect of management on extensive populations of trees and shrubs in central Australian rangelands. One useful indicator of change in these populations is the density of individuals, and there are several methods available based on distance measurement for density estimation. This study compared those procedures. Samples were drawn by computer from ground maps of actual plant distributions for Acacia aneura, Cassia nemophila and Atalaya hemiglauca and from a map generated at random. These samples were drawn to examine the properties of the nearest neighbour, point centred quarter, conditioned distance and compound T-square estimates of density. Samples were drawn by two methods: simple random sampling and semisystematic sampling. In general, there was a tendency for all estimators of density to underestimate the true density of naturally occurring populations with the compound T-square method (Byth 1982) being most robust. The compound T-square method was least biased but its variance increased for more aggregated spatial distributions. Estimates of density were not altered by the use of semisystematic sampling, when compared to simple random sampling. The spatial distributions examined in this study have not previously been studied as theoretical models. Acacia aneura and Cassia nemophila showed some aggregation of clusters, while the Atalaya hemiglauca showed a more extreme form of clustering due to its root suckering propagation. 相似文献
7.
In the majority of agricultural growing regions, crop production is highly dependent on the supply of exogenous nitrogen (N) fertilizers. Traditionally, this dependency and the use of N-fertilizers to restore N depleted soils has been rewarded with increased plant health and yields. In recent years, increased competition for non-renewable fossil fuel reserves has directly elevated prices of N-fertilizers and the cost of agricultural production worldwide. Furthermore, N-fertilizer based pollution is becoming a serious issue for many regions where agriculture is highly concentrated. To help minimize the N footprint associated with agricultural production there is significant interest at the plant level to develop technologies which can allow economically viable production while using less applied N. To complement recent reviews examining N utilization efficiency in agricultural plants, this review will explore those strategies operating specifically at the root level, which may directly contribute to improved N use efficiencies in agricultural crops such as cereals, where the majority of N-fertilizers are used and lost to the environment. Root specific phenotypes that will be addressed in the context of improvements to N acquisition and assimilation efficiencies include: root morphology; root to shoot ratios; root vigour, root length density; and root N transport and metabolism. 相似文献
8.
MARINA CORRÊA CÔRTES ELIANA CAZETTA VANESSA GRAZIELE STAGGEMEIER MAURO GALETTI 《Austral ecology》2009,34(3):249-258
Seed dispersal by animals is a complex process involving several distinct stages: fruit removal by frugivores, seed delivery in different microhabitats, seed germination, seedling establishment, and adult recruitment. Nevertheless, studies conducted until now have provided scarce information concerning the sequence of stages in a plant's life cycle in its entirety. The main objective of this study was to evaluate the immediate consequences of frugivore activity for Eugenia umbelliflora (Myrtaceae) early recruitment by measuring the relative importance of each fruit‐eating bird species on the establishment of new seedlings in scrub and low restinga vegetation in the Atlantic rainforest, Brazil. We conducted focal tree observations on E. umbelliflora trees recording birds' feeding behaviour and post‐feeding movements. We also recorded the fate of dispersed seeds in scrub and low restinga vegetation. We recorded 17 bird species interacting with fruits in 55 h of observation. Only 30% of the handled fruits were successfully removed. From 108 post flight movements of exit from the fruiting trees, 30.6% were to scrub and 69.4% to low restinga forest. Proportion of seed germination was higher in low restinga than in the scrub vegetation. Incorporating the probabilities of seeds' removal, deposition, and germination in both sites, we found that the relative importance of each frugivorous bird as seed dispersers varies largely among species. Turdus amaurochalinus and Turdus rufiventris were the best dispersers, together representing almost 12% probability of seed germination following removal. Our results show the importance of assessing the overall consequence of seed dispersal within the framework of disperser effectiveness, providing a more comprehensive and realistic evaluation of the relative importance of different seed dispersers on plant population dynamics. 相似文献
9.
VANESSA R. LANE KARL V. MILLER STEVEN B. CASTLEBERRY DARREN A. MILLER T. BENTLY WIGLEY 《The Journal of wildlife management》2010,74(3):595-599
ABSTRACT Avian bycatch, a common and undesired occurrence in small mammal studies, should be minimized by researchers. We examined effects of trap covering, treadle color (copper or yellow plastic), trap size (mouse or rat), and trap weathering (traps <1 yr or ≥ 1 yr old) on avian bycatch during 3 years. We found that covered traps caught 81% fewer birds and 70% fewer small mammals than did uncovered traps, that mouse traps caught 30% more birds and 38% more small mammals than did rat traps, and no capture differences for treadle color or trap weathering. Covered traps effectively reduced avian bycatch and should be used when reduced small-mammal capture rates are acceptable. 相似文献
10.
VANESSA MILLER‐SIMS MARTHA DELANEY JELLE ATEMA MICHAEL J. KINGSFORD GABRIELE GERLACH 《Molecular ecology resources》2005,5(2):424-426
To determine the degree of genetic exchange between populations of the neon damselfish, Pomacentrus coelestis, among different reefs of the Great Barrier Reef, Australia, we characterized seven polymorphic microsatellite loci. 相似文献