Visual openness is a key element in habitat selection for many animals of grasslands and other open habitats, especially birds. Obstructions to visual openness in the form of human infrastructure or inopportune woody vegetation growth can lead to habitat avoidance, and thus pose conservation challenges. Here we introduce a remotely sensed, lidar-based index of visual openness. Like previous indices of visual openness, ours is based on the vertical angle to the horizon; however, its calculation from remotely sensed data allows it to be easily mapped across the landscape. We illustrate its potential usage by calculating the index multiple ways within two large fields in central New Jersey, USA, and evaluating the effects of openness on habitat use by a grassland bird, the Grasshopper Sparrow (Ammodramus savannarum), within an occupancy modeling framework. We used the best performing model and digitally edited openness maps to project population responses under five hypothetical management scenarios of increased habitat openness. Occupancy modeling revealed that a version of the index calculated based on the maximum angle to the horizon best explained Grasshopper Sparrow occupancy patterns. Models also revealed that Grasshopper Sparrows showed a negative response to openness reductions caused by both powerlines and trees. Predictions based on the increased openness scenarios indicated that removal of tree lines and powerlines could increase patch-level occupancy of the sparrows in the affected fields by up to 15% and 9%, respectively. Where adequate data exist, this index has the potential to facilitate the study of openness-habitat use relationships in a variety of open-dwelling fauna and in a variety of habitats, from tundra to marshes to grasslands. Notably, it has promising potential for use in modeling habitat suitability and projecting potential impacts in response to anthropogenic changes in visual openness, such as wind farms, power infrastructure, or vegetation management.

中文翻译：

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一个基于激光雷达的开放指数，以帮助草原野生动物的保护规划

对于草原和其他开放栖息地的许多动物，尤其是鸟类，视觉开放性是栖息地选择的关键因素。人类基础设施或不合时宜的木本植被生长形式的视觉开放障碍可能导致栖息地回避，从而带来保护挑战。在这里，我们介绍了一种基于激光雷达的遥感视觉开放指数。像以前的视觉开放性指标一样，我们的指标是基于与地平线的垂直角度；然而，它根据遥感数据进行的计算使其可以轻松地在整个景观中绘制。我们通过在美国新泽西州中部的两个大田地内以多种方式计算指数来说明其潜在用途，并评估开放性对草原鸟类蚱蜢麻雀 (Ammodramus savannarum) 栖息地利用的影响，在占用建模框架内。我们使用性能最佳的模型和数字编辑的开放性地图来预测在增加栖息地开放性的五种假设管理情景下的人口反应。占用模型显示，根据与地平线的最大角度计算的指数版本最好地解释了蚱蜢麻雀的占用模式。模型还显示，蚱蜢麻雀对电力线和树木造成的开放度降低表现出负面反应。基于增加的开放性情景的预测表明，移除树线和电力线可以将受影响田地中麻雀的斑块级占用率分别增加高达 15% 和 9%。在存在足够数据的情况下，该指数有可能促进对各种开放栖息动物群和各种生境（从苔原到沼泽再到草原）的开放性-生境利用关系的研究。值得注意的是，它具有用于模拟栖息地适宜性和预测潜在影响以响应视觉开放性的人为变化的巨大潜力，例如风电场、电力基础设施或植被管理。