Polivka Carlos M, Malone Margaret A, Carran Spencer A, Dwyer Greg
Pacific Northwest Research Station, USDA Forest Service, Wenatchee, Washington, USA.
Cascadia Conservation District, Wenatchee, Washington, USA.
Ecol Appl. 2024 Dec;34(8):e3033. doi: 10.1002/eap.3033. Epub 2024 Oct 2.
Habitat selection theory enables inferences about species habitat choice across a range of observed population densities. However, it is relatively uncommon to use habitat selection theory in studies of habitat restoration efficacy to understand the effect of restoration on habitat competition. We combined observational density data and resource selection functions to analyze habitat correlations with both habitat selection theory and a mark-recapture experiment to show how habitat restoration can mitigate competition between species with similar habitat preferences. To restore degraded and channelized riverine habitat for juvenile Chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (Oncorhynchus mykiss) engineered log jams (ELJs) have been installed to create pools to enhance growth and rearing. Application of habitat selection theory first showed that both species share a preference for ELJ-treated habitat over unrestored habitat. Linear models showed that steelhead are generalists with respect to depth in unrestored habitat, whereas both species' abundance varies along a depth gradient in ELJ-treated habitat. Selective versus opportunistic use of deep and shallow ELJ pools was density-dependent. We found a range of densities at which a "ghost of competition" exists, where Chinook are selective on deep ELJ-treated pools and steelhead are selective on shallow pools. A mark-recapture experiment confirmed that steelhead limit Chinook movement into unrestored habitat, but this competitive effect vanished in ELJ-treated habitat where selection occurred with respect to pool depth. The experiment, combined with theory, enabled (1) the identification of a mechanism allowing for shared preference of restored habitat and (2) the description of how restoration can mitigate competition.
栖息地选择理论有助于推断在一系列观察到的种群密度下物种的栖息地选择情况。然而，在栖息地恢复效果研究中运用栖息地选择理论来理解恢复对栖息地竞争的影响相对较少见。我们结合观测密度数据和资源选择函数，运用栖息地选择理论并通过标记重捕实验来分析栖息地相关性，以展示栖息地恢复如何减轻具有相似栖息地偏好的物种之间的竞争。为了恢复退化和渠道化的河流栖息地，为奇努克鲑（Oncorhynchus tshawytscha）幼鱼和虹鳟（Oncorhynchus mykiss）建造了工程原木堵塞物（ELJs）以形成水塘，促进其生长和栖息。栖息地选择理论的应用首先表明，这两个物种都更偏好经过ELJ处理的栖息地而非未恢复的栖息地。线性模型显示，在未恢复的栖息地中，虹鳟对深度的适应性较强，而在经过ELJ处理的栖息地中，两个物种的丰度均沿深度梯度变化。对深浅不同的ELJ水塘的选择性与机会性利用取决于密度。我们发现存在一系列密度，此时存在“竞争幽灵”，即奇努克鲑对经过ELJ处理的深水塘具有选择性，而虹鳟对浅水塘具有选择性。标记重捕实验证实，虹鳟限制了奇努克鲑进入未恢复的栖息地，但这种竞争效应在经过ELJ处理的栖息地中消失了，在该栖息地中，选择是基于水塘深度进行的。该实验与理论相结合，（1）确定了一种机制，使得对恢复栖息地存在共同偏好；（2）描述了恢复如何减轻竞争。
