Evaluation of Habitat Suitability Models for Forest Passerines Using Demographic Data

ABSTRACT Habitat suitability is often used as a surrogate for demographic responses (i.e., abundance, survival, fecundity, or population viability) in the application of habitat suitability index (HSI) models. Whether habitat suitability actually relates to demographics, however, has rarely been evaluated. We validated HSI models of breeding habitat suitability for wood thrush (Hylocichla mustelina) and yellow-breasted chat (Icteria virens) in Missouri, USA. First, we evaluated HSI models as a predictor of 3 demographic responses: within-site territory density, site-level territory density, and nest success. We demonstrated a link between HSI values and all 3 types of demographic responses for the yellow-breasted chat and site-level territory density for the wood thrush. Second, we evaluated support for models containing HSI values, models containing measured habitat features (e.g., tree age, tree species, ecological land type), and models containing management treatments (e.g., even-aged and uneven-aged forest regeneration treatments) for each demographic response using model selection. Models containing HSI values received more support, in general, than models containing only habitat features or management treatments for all 3 types of wildlife response. The assumption that changes in habitat suitability represent wildlife demographic response to vegetation change is supported by our models. However, differences in species ecology may contribute to the degree to which HSI values are related to specific demographic responses. We recommend validation of HSI models with the particular demographic data of interest (i.e., density, productivity) to increase confidence in the model used for conservation planning.     

Habitat suitability and nest survival of white-headed woodpeckers in unburned forests of Oregon

We evaluated habitat suitability and nest survival of breeding white-headed woodpeckers (Picoides albolarvatus) in unburned forests of central Oregon, USA. Daily nest-survival rate was positively related to maximum daily temperature during the nest interval and to density of large-diameter trees surrounding the nest tree. We developed a niche-based habitat suitability model (partitioned Mahalanobis distance) for nesting white-headed woodpeckers using remotely sensed data. Along with low elevation, high density of large trees, and low slope, our habitat suitability model suggested that interspersion–juxtaposition of low- and high-canopy cover ponderosa pine (Pinus ponderosa) patches was important for nest-site suitability. Cross-validation suggested the model performed adequately for management planning at a scale >1 ha. Evaluation of mapped habitat suitability index (HSI) suggested that the maximum predictive gain (HSI = 0.36), where the number of nest locations are maximized in the smallest proportion of the modeled landscape, provided an objective initial threshold for identification of suitable habitat. However, managers can choose the threshold HSI most appropriate for their purposes (e.g., locating regions of low–moderate suitability that have potential for habitat restoration). Consequently, our habitat suitability model may be useful for managing dry coniferous forests for white-headed woodpeckers in central Oregon; however, model validation is necessary before our model could be applied to other locations. © 2011 The Wildlife Society.     

Using Bayesian networks to incorporate uncertainty in habitat suitability index models

Habitat suitability index (HSI) models rarely characterize the uncertainty associated with their estimates of habitat quality despite the fact that uncertainty can have important management implications. The purpose of this paper was to explore the use of Bayesian belief networks (BBNs) for representing and propagating 3 types of uncertainty in HSI models—uncertainty in the suitability index relationships, the parameters of the HSI equation, and measurement of habitat variables (i.e., model inputs). I constructed a BBN–HSI model, based on an existing HSI model, using Netica™ software. I parameterized the BBN's conditional probability tables via Monte Carlo methods, and developed a discretization scheme that met specifications for numerical error. I applied the model to both real and dummy sites in order to demonstrate the utility of the BBN–HSI model for 1) determining whether sites with different habitat types had statistically significant differences in HSI, and 2) making decisions based on rules that reflect different attitudes toward risk—maximum expected value, maximin, and maximax. I also examined effects of uncertainty in the habitat variables on the model's output. Some sites with different habitat types had different values for E[HSI], the expected value of HSI, but habitat suitability was not significantly different based on the overlap of 90% confidence intervals for E[HSI]. The different decision rules resulted in different rankings of sites, and hence, different decisions based on risk. As measurement uncertainty in habitat variables increased, sites with significantly different (α = 0.1) E[HSI] became statistically more similar. Incorporating uncertainty in HSI models enables explicit consideration of risk and more robust habitat management decisions. © 2012 The Wildlife Society.     

老爷岭南部狍冬季移动、卧息生境选择及其适宜性评价

在动物生境研究中,移动生境和卧息生境是生境研究的焦点。开展移动生境和卧息生境选择,并在此基础上进行生境评价,有利于深入了解动物对移动和卧息生境条件的需求,制定科学合理的栖息地保护计划。以东北虎（Panthera tigris altaica）的主要猎物物种之一-狍（Capreolus pygargus）为研究对象,于2017-2019年冬季积雪覆盖期在老爷岭南部通过随机布设28个大样方和84条用于足迹链跟踪的样线收集狍的移动点和卧息点信息,再结合近年来收集的东北虎出现点,利用广义可加模型（GAM）和最大熵模型（MaxEnt）进行狍移动、卧息生境选择及评价研究。移动生境选择研究表明,狍在移动的过程中偏好选择坡度小、距农田距离>500 m、远离道路、居民点和低海拔或较高海拔的区域;移动生境评价分析表明,移动适宜和次适宜生境面积之和为1318.16 km²,占研究区域面积的51.28%,当加入虎活动点影响因子后,狍移动适宜和次适宜生境面积之和为901.52 km²,适宜和次适宜生境面积之和减少了31.61%。狍卧息生境选择研究表明,水源、农田、道路和雪深是影响狍卧息的关键因素,其中雪深对狍卧息生境选择的贡献率达到70.13%;卧息生境评价表明,卧息适宜和次适宜生境面积之和为1243.77 km²,占研究区域面积的48.39%,当加入虎出现点因子后,适宜生境和次适宜生境面积之和减少了61.00%,仅为485.02 km²。研究认为,虎的出现对狍移动和卧息生境选择均产生影响,虎的活动及捕食行为可能会减少狍的活动范围和频次,狍远离虎活动区域卧息休息,压缩了狍适宜卧息的空间。     

白山原麝国家级自然保护区獐春夏生境选择

生境与动物个体密切相关,生境中元素的不同影响着动物个体对不同生境的选择。2018年5-7月和2019年3-4月在吉林省白山原麝国家级自然保护区对獐（Hydropotes inermis）的春夏季生境选择进行了研究,共记录利用样方104个（春季53个,夏季51个）,对照样方85个（春季46个,夏季39个）。利用卡方检验对植被类型、优势植物、坡位、坡向4种非数值型环境因子进行分析,结果表明春季和夏季獐对这4种环境因子的选择均具有显著性差异,偏好选择以青蒿（Artemisia carvifolia）为优势植物,位于中坡位,坡向为阳坡的草地生境活动。利用独立样本T检验和Mann-Whitney U检验对海拔、人为干扰距离、水源距离、草本覆盖度、优势草本高度、隐蔽级、坡度7种数值型环境因子进行分析,结果表明春季和夏季獐均偏好选择隐蔽级较高（春季30.189±14.609,夏季62.745±29.737）、优势草本高度较高（春季87.359±16.190,84.510±29.618）、坡度较缓的生境（春季14.245±3.721,13.333±5.260）活动。此外,资源选择函数模型对獐的春季和夏季的生境选择预测正确率均大于90%,表明该模型可以较好地预测獐的生境选择。白山原麝国家级自然保护区獐种群数量较小,适宜性栖息地面积较少,应加强对其种群及适宜性生境的保护。     

基于最大熵模型的野生马麝夏季生境适宜性研究

野生马麝(Moschus chrysogaster)是珍稀濒危资源动物,分布于我国青藏高原及周边地区。甘肃兴隆山国家级自然保护区是野生马麝最重要的分布区之一,深入了解保护区的生境结构、质量及分布是对区域内野生马麝进行成功保护的前提和基础,但迄今缺乏大尺度的马麝生境适宜性研究。利用实地调查得到的兴隆山保护区的野生马麝夏季分布点数据,采用最大熵(MaxEnt)模型,结合地形、归一化植被指数、距河流距离、距道路距离等环境变量数据,进行野生马麝的夏季生境适宜性分析。结果表明：影响野生马麝夏季生境适宜性的主要生态因子是海拔、坡向、植被和河流,其贡献率分别达40.3%,23.4%,18.6%和10.9%;兴隆山保护区野生马麝的夏季潜在适宜生境分布面积为123.34 km²,占整个保护区的41.11%,占保护区林地的61.92%;野生马麝夏季潜在适宜生境主要集中在保护区的中部和西部,其中高适宜性生境约为保护区的4.47%,各适宜区间及适宜区之内均存在一定程度的不连续分布。为加强对兴隆山保护区野生马麝种群及生境的就地保护,建议通过生境保育措施,提高野生马麝潜在分布区的生境适宜性,...     

大兴安岭南段马鹿生境适宜性分析与生态廊道构建

构建生态廊道在缓解生境破碎化对生物多样性的影响、维持濒危物种的遗传多样性、维护自然生态系统结构完整与功能稳定方面具有重要作用。以内蒙古大兴安岭南段分布的马鹿(Cervus elaphus)种群为研究对象,利用MaxEnt模型对其生境适宜性进行分析,并利用最小累积阻力模型构建潜在生态扩散廊道,探讨大兴安岭南段区域隔离马鹿种群的栖息地连通方案。结果显示,马鹿栖息地呈破碎化状态,种群有明显的隔离分布趋势,现有适宜栖息地具有海拔较低(800—1200 m)、坡度较缓(<15°)、靠近水源、植被类型多为靠近山林的灌丛或草地等特点。所构建12条生态廊道具有经过河流浅水节段、远离村落等特点,便于落实栖息地生态恢复管理措施。研究从区域尺度综合分析了大兴安岭南段马鹿栖息地现状及连通性,有助于优化适宜栖息地格局,促进马鹿扩散和栖息地连通,为该物种隔离种群及其栖息地保护规划提供现实指导和基础资料。     

Landscape Habitat Suitability Index Software

ABSTRACT Habitat suitability index (HSI) models are traditionally used to evaluate habitat quality for wildlife at a local scale. Rarely have such models incorporated spatial relationships of habitat components. We introduce Landscape HSImodels, a new Microsoft Windows® (Microsoft, Redmond, WA)—based program that incorporates local habitat as well as landscape-scale attributes to evaluate habitats for 21 species of wildlife. Models for additional species can be constructed using the generic model option. At a landscape scale, attributes include edge effects, patch area, distance to resources, and habitat composition. A moving window approach is used to evaluate habitat composition and interspersion within areas typical of home ranges and territories or larger. The software and sample data are available free of charge from the United States Forest Service, Northern Research Station at http:www.nrs.fs.fed.ushsi .     

浙江清凉峰国家级自然保护区华南梅花鹿栖息地适宜性评价

理解环境因子对物种空间分布的影响,评价栖息地适宜性现状并预测潜在分布区,对野生动物的管理和保护具有重要意义。华南梅花鹿（Cervus pseudaxis）属国家I级重点保护野生动物,现仅分布于安徽、浙江、江西等狭小片区内。浙江清凉峰自然保护区千顷塘区域是华南梅花鹿的重要分布区,但其面积较小,严重限制了华南梅花鹿的种群发展,亟需对千顷塘及周边区域的栖息地质量进行评价,为华南梅花鹿的保护和野外放归提供科学依据。本研究利用红外相机监测千顷塘区域华南梅花鹿的分布,结合遥感等技术手段获得地形、植被、水源以及人为干扰等8种环境因子,利用MaxEnt构建华南梅花鹿栖息地适宜性模型,对以千顷塘为中心50 km×50 km的范围进行栖息地适宜性评价。研究结果表明,华南梅花鹿倾向于选择海拔1050-1240 m范围内,距道路100-900 m和距人口聚居区3200-3800 m的相对平缓地带。千顷塘区域华南梅花鹿栖息地保护较好,适宜栖息地面积为2224 hm2,占该区域39.1%。千顷塘周边适宜性较高的区域主要为位于其西南部约10 km的山区,该区域为华南梅花鹿提供了3253 hm2的潜在适宜栖息地。建议降低保护区千顷塘区域内的人为干扰,并在其西南部山区尝试开展圈养种群的野外放归工作,以促进其种群发展。     

When perception reflects reality: Non‐native grass invasion alters small mammal risk landscapes and survival

Modification of habitat structure due to invasive plants can alter the risk landscape for wildlife by, for example, changing the quality or availability of refuge habitat. Whether perceived risk corresponds with actual fitness outcomes, however, remains an important open question. We simultaneously measured how habitat changes due to a common invasive grass (cheatgrass, Bromus tectorum) affected the perceived risk, habitat selection, and apparent survival of a small mammal, enabling us to assess how well perceived risk influenced important behaviors and reflected actual risk. We measured perceived risk by nocturnal rodents using a giving‐up density foraging experiment with paired shrub (safe) and open (risky) foraging trays in cheatgrass and native habitats. We also evaluated microhabitat selection across a cheatgrass gradient as an additional assay of perceived risk and behavioral responses for deer mice (Peromyscus maniculatus) at two spatial scales of habitat availability. Finally, we used mark‐recapture analysis to quantify deer mouse apparent survival across a cheatgrass gradient while accounting for detection probability and other habitat features. In the foraging experiment, shrubs were more important as protective cover in cheatgrass‐dominated habitats, suggesting that cheatgrass increased perceived predation risk. Additionally, deer mice avoided cheatgrass and selected shrubs, and marginally avoided native grass, at two spatial scales. Deer mouse apparent survival varied with a cheatgrass–shrub interaction, corresponding with our foraging experiment results, and providing a rare example of a native plant mediating the effects of an invasive plant on wildlife. By synthesizing the results of three individual lines of evidence (foraging behavior, habitat selection, and apparent survival), we provide a rare example of linkage between behavioral responses of animals indicative of perceived predation risk and actual fitness outcomes. Moreover, our results suggest that exotic grass invasions can influence wildlife populations by altering risk landscapes and survival.     

Using Bobcat Habitat Suitability to Prioritize Habitat Preservation on a Suburbanizing Barrier Island

ABSTRACT Many land-trust organizations attempt to preserve habitat that will benefit specific wildlife species or suites of species. With limited resources available, these organizations need tools to prioritize preservation efforts. One such organization, the Kiawah Island Natural Habitat Conservancy (KINHC), is attempting to preserve wildlife habitat in the face of ever-increasing property values and development pressure on Kiawah Island, South Carolina, USA. We modified an existing bobcat (Lynx rufus) habitat suitability index model, which focuses on suitability of habitats for food, by including components for concealment cover and den habitat. We developed a windows-based computer program that calculates modified habitat suitability index (MHSI) values that can easily be imported into a Geographic Information System for display in map form, allowing for frequent reevaluation of site-specific habitat suitability as land-cover patterns change. We used locations collected from radiocollared bobcats to assess validity of the food and cover components of the MHSI. Bobcats used areas identified as highly suitable for food more than expected during nocturnal time periods (G₅₂ = 640.9, P < 0.001) and areas identified as highly suitable for cover more than expected during diurnal time periods (G₃₇ = 1,194.0, P < 0.001). Our approach for evaluating bobcat habitat suitability will allow KINHC to identify parcels that likely provide the greatest ecological benefit to bobcats and their associated wildlife community. Our approach could be altered to consider habitat requirements of other species, or multiple species, at virtually any location for which fine-scale land-cover data are available.     

Integrating GIS and expert judgment in a multi-criteria analysis to map and develop a habitat suitability index: A case study of large mammals on the Malayan Peninsula

Many habitat patches in tropical landscapes have become less suitable for wildlife due to an increase in anthropogenic disturbances. An index of habitat suitability based on the ecological factors that collectively determine the suitability of an organism's habitat is important for conservation planning. However, a widely accepted and comprehensive multi-criteria habitat suitability index for umbrella species is still lacking, particularly in areas where information related to the biology and ecology of the species of interest is not available. Therefore we develop preliminary habitat maps and measure the degree of habitat suitability for large mammals, focusing on four umbrella species in the State of Selangor, Peninsular Malaysia: Panthera tigris jacksoni (Malayan tiger), Tapirus indicus (Malayan tapir), Helarctos malayanus malayanus (Malayan sun bear), and Rusa unicolor cambojensis (sambar deer). The former two are endangered and the latter two are vulnerable according to the IUCN Red List. The suitability of habitat patches for each species was measured across the entire study area as well as in nine wildlife protected areas by integrating GIS data and expert opinion. Expert opinions were used as the source of information regarding the stresses faced by the species because there was insufficient information available from ground surveys.We developed an index and maps of habitat suitability for each species, which were then integrated to represent a combined index (ranging from 0 to 27) and spatially explicit maps of the area's habitat suitability for large mammals. The average large mammal habitat suitability index value of the State of Selangor (9) indicates that many habitat patches have become unsuitable for such species. Of the nine wildlife protected areas, Fraser's Hill (22), Sungai Dusun (22), and Bukit Kutu (21) are very suitable; Klang Gate (20) and Templers Park (17) are suitable; and the remaining four are unsuitable for large mammals. We assume that this preliminary habitat suitability index and mapping are useful for conservation planning of wildlife habitats at both landscape and regional scales, as well as providing an initial foundation for revision by future research with significant new information.     

基于生境适宜性指数模型的俚岛海黍子生境层级分布

为了深入了解海黍子生境,利用模型对山东俚岛海黍子生境进行适宜性分析,分别选取温度、盐度、水深、浊度、底质、无机氮浓度、磷酸盐浓度和距海藻床距离8种环境因子,通过层次分析法赋值因子权重,结合空间分析方法建立了海黍子HSI模型。利用该模型对山东俚岛近岸海域2018年春、秋两季的环境因子调查结果进行了海黍子生境分析。结果表明: 研究区域内的海黍子海藻床区域主要由极佳生境和适宜生境组成,春季和秋季的分布面积分别占14.2%和18.6%。海黍子生境层级分布随季节而变化,且不同季节的生境层级具有一定的空间重合性。温度和磷酸盐浓度的适宜性变化具有明显的季节性差异,是导致俚岛海黍子HSI季节变化的主要原因。海黍子HSI模型不仅可用于检测海黍子海藻床区域的生境层级分布,还能发现海黍子潜在的适宜生境区域。这为今后开展海黍子资源保护和人工增殖工作提供了科学参考。     

基于MAXENT模型的贺兰山西坡啮齿动物生境适宜性评价

贺兰山因其拥有独特的植物垂直分布带而十分适宜啮齿动物生存,但自保护区生态恢复以来并未见有研究评价啮齿动物在贺兰山的生境适宜性,使得其分布现状未知。使用GIS技术和MAXENT模型对内蒙古贺兰山国家级自然保护区6种主要啮齿动物进行生境适宜性状况评价及预测,探究啮齿动物在贺兰山的分布现状。结果表明：影响6种啮齿动物的主要环境因子为海拔、坡度和距矿区距离,海拔越高、坡度越大及距矿区距离越近均使啮齿动物生存适宜性降低;两两鼠种生境适宜面积叠加发现,大林姬鼠和阿拉善黄鼠适宜生境重叠面积最大(261.37 km~2),短尾仓鼠和子午沙鼠的适宜生境重叠面积最小(19.00 km~2);6种主要鼠种均适宜的生境面积交集仅有17.14 km~2,占贺兰山总面积的0.47%,6种主要鼠种均不适宜的生境面积有2985.23 km~2,占贺兰山总面积的81.21%。研究表明,啮齿动物栖息地距矿区距离仍是影响其适宜生境的重要因素之一,建议相关部门加强对废弃矿区采取措施,改善保护区啮齿动物生境质量。     

Suitability indices and habitat suitability index model of Caspian kutum (Rutilus frisii kutum) in the southern Caspian Sea

The relationship between species and habitat is important in ecosystem-based fisheries management. Habitat suitability index (HSI) modeling is a valuable tool in ecology and can be used to describe the relationship between fish abundance and ecological variables in order to estimate the suitability of specific habitats. In the present study, an HSI model was applied to determine suitable habitats for the Caspian kutum (Rutilus frisii kutum), an important commercial species in the southern Caspian Sea. An arithmetic mean model (AMM) was found to be the most appropriate model for describing the relationship between two of the environmental variables investigated (depth and benthos biomass). However, a geometric mean model explained the evident relationship when all four environmental variables were used (depth, benthos biomass, photosynthetically active radiation and sea surface temperature). The areas with an HSI > 0.5 had over 85 % of the total catch indicating the reliability of the prediction of the Caspian kutum habitat using the AMM. The present study showed that depth and substrate structure are the most important environmental variables for the Caspian kutum to select its habitats, and between remotely sensed data, chlorophyll a, photosynthetically active radiation and sea surface temperature are the most critical parameters for near real-time prediction of the Caspian kutum habitat.     

Overpasses intended for human use can be crossed by middle and large-size mammals

Road overpasses cost more than underpasses and can be built for most terrestrial mammals to resolve and/or minimize effects from habitat fragmentation. Many overpasses intended for human activity might also allow wildlife passage. Using digital infrared cameras from 2015 to 2016 in Hokkaido, Japan, we evaluated such use in three overpasses, where two were designed for humans and one for wildlife. Nine mammal species were detected at the three overpasses. Three middle-sized mammals—raccoons (Procyon lotor), red foxes (Vulpes vulpes), and raccoon dogs (Nyctereutes procyonoides)—and a large mammal species, the sika deer (Cervus nippon), frequently used all of the overpasses. Our results showed that the overpass designed for wildlife was richer in species than the two overpasses for humans. However, results also showed that there were no significant differences in use among four animal species in the three overpasses. We propose the construction of small overpasses without plants to conserve habitat reconnection of middle-sized to large mammals. Arboreal species’ habitats need structural change with additional of plants.

     

Evaluation of habitat suitability index models by global sensitivity and uncertainty analyses: a case study for submerged aquatic vegetation

Habitat suitability index (HSI) models are commonly used to predict habitat quality and species distributions and are used to develop biological surveys, assess reserve and management priorities, and anticipate possible change under different management or climate change scenarios. Important management decisions may be based on model results, often without a clear understanding of the level of uncertainty associated with model outputs. We present an integrated methodology to assess the propagation of uncertainty from both inputs and structure of the HSI models on model outputs (uncertainty analysis: UA) and relative importance of uncertain model inputs and their interactions on the model output uncertainty (global sensitivity analysis: GSA). We illustrate the GSA/UA framework using simulated hydrology input data from a hydrodynamic model representing sea level changes and HSI models for two species of submerged aquatic vegetation (SAV) in southwest Everglades National Park: Vallisneria americana (tape grass) and Halodule wrightii (shoal grass). We found considerable spatial variation in uncertainty for both species, but distributions of HSI scores still allowed discrimination of sites with good versus poor conditions. Ranking of input parameter sensitivities also varied spatially for both species, with high habitat quality sites showing higher sensitivity to different parameters than low‐quality sites. HSI models may be especially useful when species distribution data are unavailable, providing means of exploiting widely available environmental datasets to model past, current, and future habitat conditions. The GSA/UA approach provides a general method for better understanding HSI model dynamics, the spatial and temporal variation in uncertainties, and the parameters that contribute most to model uncertainty. Including an uncertainty and sensitivity analysis in modeling efforts as part of the decision‐making framework will result in better‐informed, more robust decisions.     

基于生态位模型的艾比湖国家级自然保护区马鹿生境评价

生境评价和预测是对濒危物种进行有效保护的基础。通过2013年9月和2014年10月对新疆艾比湖国家级自然保护区开展2次秋季野外调查共收集了92处马鹿(Cervuselaphus)出现数据,利用马鹿出现数据作为分布点数据,选取地形、植被类型和气候因子3类23种因子作为生境变量,利用MAXENT生态位模型分析了新疆艾比湖国家级自然保护区马鹿秋季生境适宜性分布特征和主要生境因子对马鹿分布的影响。结果表明:模型预测结果较高,平均AUC(area under the curve,受试工作者曲线下面值)值为0.976;Jackknife检验结果显示:最热月最高温度对马鹿生境分布的影响较大。植被类型和坡度对马鹿生境分布的影响不大。海拔、年降雨量、气温日较差和最热季平均温度是影响马鹿生境分布的主要生境因子。马鹿秋季生境划分为高适宜、次适宜、低适宜和不适宜4个等级,马鹿的高适宜生境区主要分布在研究区域的北部,次适宜及低适宜生境区则分布于高适宜生境区的边缘,而不适宜生境区主要集中在西部和东部地区。研究不仅提供了马鹿在艾比湖的实际分布状况,也为马鹿生境和生境因子的关系方面提供了一个重要的科学依据。     

甘肃兴隆山保护区野生马麝分布、数量特征及影响因素

综合采用样线法、粪堆计数法及重复调查法对甘肃省兴隆山国家级自然保护区的野生马麝（Moschus chrysogaster）进行了种群调查,结合生境分析,确定了其种群分布、数量特征及影响因素。结果表明,兴隆山保护区分布有野生马麝（1159±275）头,平均种群密度为（3.51±0.83）头/km²;各植被类型生境中的野生麝种群数量及密度存在差异,灌丛生境分布有70%的野生马麝种群,达（807±170）头,种群密度为（6.49±1.63）头/km²;针叶林种群密度最大,达（8.85±83.25）头/km²,分布有野生麝（123±45）头;针阔混交林分布最少,仅（41±15）头,种群密度为（5.00±1.84）头/km²;人工林生境无野生马麝分布。保护区各植被类型生境中的野生马麝种群分布差异反映了马麝对适宜生境功能的需求,食物、保温和隐蔽性是制约野生马麝冬季分布和种群数量的关键因素。此外,因生境及人为干扰强度的不同,保护区各区域的野生马麝种群分布存在差异。建议通过减少人为干扰、地表植被管理及人工林管理优化等措施增加生境适宜性,促进兴隆山自然保护区野生马麝种群的快速恢复和增长。     

基于核密度估计的动物生境适宜度制图方法

生境适宜度制图能提供动物适宜生境的空间分布信息,对野生动物种群管理、保护地规划等非常重要。生境适宜度制图的关键是构建生境适宜度模型(habitat suitability model, HSM),只基于动物出现位置数据构建HSM的方法在实践中得到了非常广泛的应用。然而现有的只基于动物出现位置数据构建HSM的方法还不能很好地直接表达动物生境适宜度和环境因子之间具有生态学意义的数量关系,因此也就不能很好地体现环境因子对动物生境利用的生态学作用。 本文提出了一种基于核密度估计构建HSM的方法,在地理信息系统技术支持下,通过运用核密度估计从代表性的动物出现位置数据中估计出动物出现对各个环境因子的概率密度函数来直接表达生境适宜度与各个环境因子之间的数量关系,以体现环境因子对动物生境利用的生态学作用,在此基础上对生境适宜度与各个环境因子之间的数量关系进行综合构建了具有明确生态学意义的HSM用于动物生境适宜度制图。以美国Voyageures国家公园的白尾鹿(Odocoileus virginianus)生境适宜度制图为例,基于365个出现位置点位数据并结合积雪深度、地表覆被类型、森林边界长度和坡度等环境因子数据,开展了该方法的案例研究。通过交叉验证计算连续Boyce指数对制图结果进行评价,结果表明：基于核密度估计方法构建的HSM预测能力强,所得出的生境适宜度图经10次交叉验证,连续Boyce指数平均值为0.75,标准差为0.11,达到了较高精度。此外,由于基于核密度估计的方法能以“生境适宜度和环境因子之间具有生态学意义的数量关系”的形式来直接体现环境因子对动物生境利用的生态学作用,就模型的可解释性而言,该方法要优于现有的其他构建HSM的方法。