TY - JOUR
T1 - Time-series maps reveal widespread change in plant functional type cover across Arctic and boreal Alaska and Yukon
AU - Macander, Matthew J.
AU - Nelson, Peter R.
AU - Nawrocki, Timm W.
AU - Frost, Gerald V.
AU - Orndahl, Kathleen M.
AU - Palm, Eric C.
AU - Wells, Aaron F.
AU - Goetz, Scott J.
N1 - Funding Information:
This study was part of the Arctic-Boreal Vulnerability Experiment (ABoVE). Resources supporting this work were provided by the NASA High-End Computing Program through the NASA Center for Climate Simulation at Goddard Space Flight Center. This work was supported by NASA ABoVE grants NNX17AE44G and 80NSSC19M0112 and Strategic Environmental Research and Development Program (SERDP) award RC18-1183. A National Park Service task agreement (P15AC01022) and additional support from the Northwest Arctic Borough funded early exploration of mapping lichen functional groups by Nelson. In addition to reference data provided by co-authors, we thank Carl Roland, Dave Swanson and Kyle Joly (National Park Service), Sarah Burnett (Bureau of Land Management), Nadele Flynn, Marcus Waterreus, and Caitlin Willier (Yukon Government), Bill Collins (Alaska Department of Fish and Game), Todd Mahon (Environmental Dynamics Inc.), and Emily Holt (University of Northern Colorado) for sharing reference data to use in our mapping. We also thank the numerous field biologists who collected those data and the project managers who supported their efforts (see table S3 for further details). We appreciate the insightful comments of two anonymous reviewers. At ABR, Pam Odom assisted in formatting the manuscript and Alex Prichard provided statistical advice.
Publisher Copyright:
© 2022 The Author(s). Published by IOP Publishing Ltd.
PY - 2022
Y1 - 2022
N2 - Widespread changes in the distribution and abundance of plant functional types (PFTs) are occurring in Arctic and boreal ecosystems due to the intensification of disturbances, such as fire, and climate-driven vegetation dynamics, such as tundra shrub expansion. To understand how these changes affect boreal and tundra ecosystems, we need to first quantify change for multiple PFTs across recent years. While landscape patches are generally composed of a mixture of PFTs, most previous moderate resolution (30 m) remote sensing analyses have mapped vegetation distribution and change within land cover categories that are based on the dominant PFT; or else the continuous distribution of one or a few PFTs, but for a single point in time. Here we map a 35 year time-series (1985-2020) of top cover (TC) for seven PFTs across a 1.77 × 106 km2 study area in northern and central Alaska and northwestern Canada. We improve on previous methods of detecting vegetation change by modeling TC, a continuous measure of plant abundance. The PFTs collectively include all vascular plants within the study area as well as light macrolichens, a nonvascular class of high importance to caribou management. We identified net increases in deciduous shrubs (66 × 103 km2), evergreen shrubs (20 × 103 km2), broadleaf trees (17 × 103 km2), and conifer trees (16 × 103 km2), and net decreases in graminoids (-40 × 103 km2) and light macrolichens (-13 × 103 km2) over the full map area, with similar patterns across Arctic, oroarctic, and boreal bioclimatic zones. Model performance was assessed using spatially blocked, nested five-fold cross-validation with overall root mean square errors ranging from 8.3% to 19.0%. Most net change occurred as succession or plant expansion within areas undisturbed by recent fire, though PFT TC change also clearly resulted from fire disturbance. These maps have important applications for assessment of surface energy budgets, permafrost changes, nutrient cycling, and wildlife management and movement analysis.
AB - Widespread changes in the distribution and abundance of plant functional types (PFTs) are occurring in Arctic and boreal ecosystems due to the intensification of disturbances, such as fire, and climate-driven vegetation dynamics, such as tundra shrub expansion. To understand how these changes affect boreal and tundra ecosystems, we need to first quantify change for multiple PFTs across recent years. While landscape patches are generally composed of a mixture of PFTs, most previous moderate resolution (30 m) remote sensing analyses have mapped vegetation distribution and change within land cover categories that are based on the dominant PFT; or else the continuous distribution of one or a few PFTs, but for a single point in time. Here we map a 35 year time-series (1985-2020) of top cover (TC) for seven PFTs across a 1.77 × 106 km2 study area in northern and central Alaska and northwestern Canada. We improve on previous methods of detecting vegetation change by modeling TC, a continuous measure of plant abundance. The PFTs collectively include all vascular plants within the study area as well as light macrolichens, a nonvascular class of high importance to caribou management. We identified net increases in deciduous shrubs (66 × 103 km2), evergreen shrubs (20 × 103 km2), broadleaf trees (17 × 103 km2), and conifer trees (16 × 103 km2), and net decreases in graminoids (-40 × 103 km2) and light macrolichens (-13 × 103 km2) over the full map area, with similar patterns across Arctic, oroarctic, and boreal bioclimatic zones. Model performance was assessed using spatially blocked, nested five-fold cross-validation with overall root mean square errors ranging from 8.3% to 19.0%. Most net change occurred as succession or plant expansion within areas undisturbed by recent fire, though PFT TC change also clearly resulted from fire disturbance. These maps have important applications for assessment of surface energy budgets, permafrost changes, nutrient cycling, and wildlife management and movement analysis.
KW - Alaska
KW - Canada
KW - Landsat
KW - plant cover
KW - plant functional type
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U2 - 10.1088/1748-9326/ac6965
DO - 10.1088/1748-9326/ac6965
M3 - Article
AN - SCOPUS:85130490057
SN - 1748-9318
VL - 17
JO - Environmental Research Letters
JF - Environmental Research Letters
IS - 5
M1 - 054042
ER -