A multi-sensor, multi-scale approach to mapping tree mortality in woodland ecosystems

REMOTE SENSING OF ENVIRONMENT

卷:245

Article

Campbell, Michael J.¹  Dennison, Philip E.²  Tune, Jesse W.³  Kannenberg, Steven A.⁴  Kerr, Kelly L.⁴  Codding, Brian F.⁵  Anderegg, William R. L.⁴ 

[1] Ft Lewis Coll, Dept Geosci, 1000 Rim Dr, Durango, CO 81301 USA

[2] Univ Utah, Dept Geog, 260 Cent Campus Dr, Salt Lake City, UT 84112 USA

[3] Ft Lewis Coll, Dept Anthropol, 1000 Rim Dr, Durango, CO 81301 USA

[4] Univ Utah, Sch Biol Sci, 257 South 1400 East, Salt Lake City, UT 84112 USA

[5] Univ Utah, Dept Anthropol, 260 Cent Campus Dr, Salt Lake City, UT 84112 USA

关键词: Woodland;    Pinyon;    Pinon;    Juniper;    Land cover change;    Tree mortality;    Drone;    UAV;    UAS;    Lidar;    Landsat;   

DOI  :  10.1016/j.rse.2020.111853

来源: Elsevier

【 摘 要 】

Woodland ecosystems, dominant on nearly 4% of all terrestrial land globally, are faced with a variety of threats, including increasingly prolonged and severe droughts, invasive insect outbreaks, and the rapid spread of pathogens. While many remote sensing methods have been developed for the detection and quantification of mortality in forested environments, woodland ecosystems present unique challenges to accurately mapping tree die-off due to relatively lower canopy covers, smaller and irregularly-shaped tree crowns, and greater influence of understory vegetation and soil cover on reflectance. To address these challenges, we developed a multi-sensor, multi-scale approach combining the analytical strengths of centimeter-resolution unmanned aerial system imagery for interpreting individual tree-level mortality, airborne lidar for crown mapping and quantifying percent canopy mortality, and Landsat imagery for upscaling mortality estimates to a regional scale. This approach utilizes a new algorithm for delineating the shapes of small, irregular woodland tree crowns using lidar. To demonstrate the application of this method, we map the extent and severity of a recent tree mortality event in pinon-juniper (PJ) woodlands of southeastern Utah. Our results suggest that 39% of PJ in this region has experienced some level of mortality, with patches exceeding 50% mortality. An analysis of potential mortality drivers revealed that canopy cover, terrain, and recent winter precipitation conditions are most directly linked with mortality, although the explanatory power of the mortality driver model was low. Our approach demonstrates a methodology that could be used for tree mortality mapping and scaling in a variety woodland ecosystems, and can provide a strong basis for further ecophysiological, ecological, and carbon cycle studies involving woodland tree mortality.

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