Top-dieback trees disproportionately located near roads in Humboldt Redwood State Park.

Authors: Cody Dangerfield*, Utah State University, Larissa Yocom, Utah State University
Topics: Biogeography, Environment
Keywords: Disturbance, Remote Sensing, Forest
Session Type: Paper
Day: 4/8/2020
Start / End Time: 11:10 AM / 12:25 PM
Room: Silver, Sheraton, IM Pei Tower, Majestic Level
Presentation File: No File Uploaded


The California Department of Transportation, CalTrans, is currently considering several proposals to widen or reroute portions of Highway 101 in northern California. These projects are intended to increase access for commercial driving and minimize recurring construction costs due to roadbed instability, however these projects would also require removing portions of old growth coast redwood forest, an ecosystem that has already seen a >90% reduction due to previous logging activity. In addition to the direct influence of tree cutting, there may be indirect impacts of road construction on trees in forested areas adjacent to the road. To understand how road building has impacted coast redwoods in the past, we investigated whether a previous Highway 101 expansion in the 1950s led to decreases in crown health in nearby old growth redwood stands. We used National Agriculture Imagery Program (NAIP) imagery from 2018 and 2016 to identify coast redwood trees with top-dieback crowns. We analyzed the spatial distribution of top-dieback trees in relation to different types of forest edges (agricultural, secondary forest, road) and undisturbed areas. Our results showed that top-dieback was more prevalent in the northern portion of the park, and especially in areas adjacent to Highway 101. In conjunction with results from a related tree-ring study, this suggests that the 1950s highway expansion had impacts on trees located well beyond the immediate road edge. If the CalTrans proposals are approved, care should be taken to mitigate the long-lasting effects of road construction.

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