Yosemite Toad Predicted Habitat - CWHR A033 [ds1999]

CWHR Predicted Habitat Models represent areas of predicted suitable habitat for each species within its range. These models are built from the following principal inputs: 1) a statewide, best-available vegetation map (FVEG); 2) GIS data representing a species’ range; 3) the CWHR database of habitat suitability values for over 700 terrestrial vertebrate species. Habitat suitability ranks of Low (non-zero values less than 0.34), Medium (0.34-0.66), and High (greater than 0.66) are based on the maximum suitability value across the 3 species life requisites: reproduction, feeding, and cover. Note that previous versions of these Predicted Habitat Models used an average across the 3 life requisites in order to obtain an overall suitability score for each habitat type and stage class. Habitat suitability scores were developed based on habitat patch sizes greater than 40 acres in size and are best interpreted for habitat patches greater than 200 acres in size. The FVEG landcover dataset is an aggregation of multiple statewide landcover and regional vegetation mapping efforts, conducted at different points in time (approximately 1990 up to time of publishing) and at various resolutions, compiled by the California Department of Forestry and Fire Protection (CALFIRE). FVEG uses the most current and consistent data available for each region of the state. Decision rules were developed that controlled which layers were given priority in areas of overlap. Crosswalks were used to attribute the various data sources according to the CWHR habitat-type classification system. Attributing FVEG with CWHR habitat types allows for the extraction of areas with non-zero suitability values for each species within the bounds of its range, creating a series of maps of predicted suitable habitat which are species-specific. Because FVEG is an amalgam of disparate landcover assessment efforts across the state, the predictive power for determining suitable habitat will vary between species, and possibly even regionally for species which are widely distributed. While these maps represent CDFW’s best estimate of the presence of suitable habitat for any given species in the CWHR system, these maps are also limited by several factors: 1) the accuracy and resolution of vegetation maps in a given region; 2) the dynamic nature of the landscape in which fire and other disturbance events alter conditions at a greater frequency than mapping efforts can track; 3) the currency of expert knowledge, particularly as species adapt to changing land and climate conditions and the shifting of other species’ ranges; 4) the frequency of species-specific surveys across a representative sample of a species’ entire range; 5) metapopulation dynamics, which describes the shifting of populations within their environment as result of numerous types of interactions and responses. CWHR GIS data representing predicted suitable habitat should not be used to indicate the presence or absence of a particular species at any specific site. CWHR predicted habitat models are named according to the 4-character alpha-numeric CWHR ID assigned to each species (5 characters in the case of subspecies or other sub-taxa). There is also a “CWHR Revision Tracking Table” containing a record for each species, its CWHR ID, scientific name, common name, and range and habitat model data revision history. CWHR species range models, predicted habitat models, and GIS data of the statewide distribution of all CWHR habitat types, along with the CWHR revision tracking table, are available for download at https://www.wildlife.ca.gov/Data/CWHR.CWHR预测生境模型（CWHR Predicted Habitat Models）表征各物种种群分布范围内的潜在适宜生境区域。此类模型的构建基于以下三类核心输入：1）全州范围内可获取的最优植被地图（FVEG）；2）表征物种种群分布范围的地理信息系统（GIS）数据；3）涵盖700余种陆生脊椎动物生境适宜性值的CWHR数据库。生境适宜性等级划分为低（非零值小于0.34）、中（0.34至0.66）与高（大于0.66），其划分依据为物种三项生存必需条件——繁殖、觅食与隐蔽——的最大适宜性值。需注意，此前版本的预测生境模型采用三项生存必需条件的平均值，计算每种生境类型与阶段类别的整体适宜性得分。生境适宜性得分基于面积大于40英亩的生境斑块开发，其最适宜用于解读的对象为面积大于200英亩的生境斑块。FVEG土地覆盖数据集由加州林业与消防局（CALFIRE）整合完成，整合了多份全州土地覆盖及区域植被测绘成果，这些测绘工作于不同时段（大致为1990年至本数据集发布时）以不同分辨率开展。FVEG采用加州各区域当前可获取的最一致数据，并制定了决策规则以处理重叠区域的图层优先级问题。同时通过属性交叉映射表，依据CWHR生境类型分类系统为各类数据源赋予对应属性。将CWHR生境类型属性赋予FVEG数据集后，即可在物种的分布范围内提取出具有非零适宜性值的区域，进而生成一系列针对特定物种的预测适宜生境地图。由于FVEG整合了全州范围内不同的土地覆盖评估成果，其确定适宜生境的预测能力会因物种而异，对于分布广泛的物种甚至可能因区域不同而存在差异。尽管此类地图代表了加州鱼类与野生动物部（CDFW）对CWHR系统中任一物种适宜生境分布的最优估算，但仍受以下若干因素限制：1）特定区域植被地图的精度与分辨率；2）景观的动态特性——火灾及其他干扰事件改变生境条件的频率高于测绘工作的更新频率；3）专家知识的时效性，尤其是在物种适应土地与气候条件变化以及其他物种种群分布发生转移的背景下；4）针对物种整个分布范围的代表性样本开展物种专项调查的频率；5）集合种群动态——即各类相互作用与响应导致种群在其生存环境内发生迁移的现象。CWHR预测适宜生境的GIS数据不得用于判定某一特定地点是否存在某一物种。CWHR预测生境模型以分配给每个物种的4位字母数字组合CWHR ID命名，亚种或其他亚分类单元则采用5位ID。此外还有一份"CWHR修订跟踪表"，其中包含每个物种的CWHR ID、学名、俗名、分布范围及生境模型数据的修订历史记录。CWHR物种种群分布模型、预测生境模型以及所有CWHR生境类型全州分布的GIS数据，连同CWHR修订跟踪表，均可从https://www.wildlife.ca.gov/Data/CWHR下载获取。