Transect Survey - 2016 - Terrestrial Species Stressor Monitoring [ds2833]

<DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>Visual Encounter Transect Surveys of reptiles, birds, and other vertebrate wildlife taxa were conducted at study sites in the Great Valley and Mojave Desert in 2016. A total of 1,856 transect surveys (GV: 517, MD: 1339) at 321 study sites (GV: 91, MD: 230) were conducted between March and July 2016. For each survey, observers walked two 200-meter transects and recorded counts of and distances to all wildlife observed. The two transects are laid out as a cross intersecting at a right angle, with this intersection occurring at survey site center. The exact orientation of the cross and the sinuosity of transects was left to the discretion of the surveyor(s) to optimize sampling of the site-designated lifeform and to facilitate ease of travel (e.g., barriers or steep slopes). In the case of a riparian lifeform site, one transect was aligned along or near the stream course, and the second along the gradient extending to either side of the stream course. In the case of a guzzler or wetland, transects were aligned along approximately perpendicular sides. A laser rangefinder was used to accurately measure the perpendicular distance from the transect to the location of each wildlife group at the instance of its initial observation. The crew also noted </SPAN><SPAN>all wildlife signs (tracks, scat, burrows, nests) observed; in particular, every scat group within a 1-m swath on either side of the transect was</SPAN><SPAN /><SPAN>noted and identified by species whenever possible. All scats and tracks were removed from the swath so that return visits encountered fresh sign.</SPAN><SPAN>Individual surveys focused on either reptiles and amphibians, or on birds and scat, but observations from all surveys were combined into this dataset. These data were used for distance sampling methods to estimate abundance. </SPAN></P></DIV></DIV></DIV>

2016年，在大谷（Great Valley）与莫哈韦沙漠（Mojave Desert）的研究样地中，针对爬行动物、鸟类及其他脊椎动物类群开展了目视相遇样线调查（Visual Encounter Transect Surveys）。本次调查共完成1856条样线（transect）调查，其中大谷区域517条、莫哈韦沙漠区域1339条，覆盖321个研究样地（大谷：91个，莫哈韦沙漠：230个），调查时段为2016年3月至7月。每一次调查中，调查员需步行完成两条200米长的样线，记录观测到的所有野生动物的个体数量及其与调查员的距离。两条样线以直角相交，交点设于调查样地的中心位置。样线交叉的具体朝向以及样线的弯曲程度由调查员自主决定，以优化样地预设调查类群的采样效率并便于通行（例如避开障碍物或陡坡）。若为河岸类群样地，一条样线沿河道或紧邻河道布设，另一条沿河道两侧的梯度方向延伸；若为野生动物饮水池（guzzler）或湿地样地，则样线沿近似垂直的两侧布设。调查时使用激光测距仪，精准测量从样线到野生动物群体初始观测位置的垂直距离。调查团队同时记录观测到的所有野生动物痕迹，包括足迹、粪便、洞穴与巢穴；尤其需记录样线两侧1米宽样带（swath）内的每一处粪便群，并尽可能鉴定至物种水平。所有被记录的粪便与足迹均会从样带中移除，以确保后续回访时仅能采集到新鲜痕迹。单个调查会专注于爬行动物与两栖动物，或鸟类与粪便痕迹，但所有调查的观测数据均被整合至本数据集。这些数据被用于距离抽样（distance sampling）方法以估算种群丰度（abundance）。