TY - JOUR
T1 - Spatial patterns of tree cover change at a dry forest margin are driven by initial conditions, water balance and wildfire
AU - Harris, Lucas B.
AU - Taylor, Alan H.
N1 - Funding Information:
We thank Andrew Carleton, Laura Leites and Erica Smithwick for their comments on earlier versions of the manuscript; and Marc Meyer and Duncan Leao for advice and logistical support. This project was funded by a National Science Foundation Doctoral Dissertation Research Improvement Award (No. 1735558) and by a Center for Landscape Dynamics research award and a Ruby S. Miller Graduate Student Fellowship from The Pennsylvania State University.
Publisher Copyright:
© 2021, The Author(s), under exclusive licence to Springer Nature B.V. part of Springer Nature.
PY - 2021/2
Y1 - 2021/2
N2 - Context: Increases in tree cover at dry forest margins are a global phenomenon. Yet, how pre-existing tree cover interacts with terrain and water balance to influence tree cover change is not well-understood, nor whether subsequent disturbances restore prior tree cover patterns or create novel patterns. Objectives: To assess how terrain, water balance and pre-existing patterns of tree cover influenced late twentieth century tree cover change, and how subsequent wildfires altered tree cover patterns. Methods: We analyzed tree canopy cover at four sites at the forest-steppe ecotone on the eastern side of the Sierra Nevada, California, U.S.A., using aerial photographs from 1953/1955, 1999/2002 and 2016. Influences on tree cover change were assessed using statistical modeling, and tree cover in 1953/1955 was compared with post-wildfire tree cover in 2016. Results: From 1953 to 2002, area with > 25% canopy cover increased by 1.5 to 5-fold and treeless area decreased by 17–111%. Mesic areas and areas of sparse tree cover close to existing forest tended to gain more canopy cover. Subsequent wildfires caused a mix of net tree cover loss, little change and gain relative to 1953/1955, but at all sites areas with > 25% cover and < 10% cover in 1953/55 experienced net losses and gains respectively by 2016. Conclusions: Accounting for initial tree cover and its configuration are crucial to assessing water balance and terrain effects on tree cover change. Our work highlights how wildfires can generate novel patterns of tree cover relative to historical baselines, especially following decades of fire exclusion.
AB - Context: Increases in tree cover at dry forest margins are a global phenomenon. Yet, how pre-existing tree cover interacts with terrain and water balance to influence tree cover change is not well-understood, nor whether subsequent disturbances restore prior tree cover patterns or create novel patterns. Objectives: To assess how terrain, water balance and pre-existing patterns of tree cover influenced late twentieth century tree cover change, and how subsequent wildfires altered tree cover patterns. Methods: We analyzed tree canopy cover at four sites at the forest-steppe ecotone on the eastern side of the Sierra Nevada, California, U.S.A., using aerial photographs from 1953/1955, 1999/2002 and 2016. Influences on tree cover change were assessed using statistical modeling, and tree cover in 1953/1955 was compared with post-wildfire tree cover in 2016. Results: From 1953 to 2002, area with > 25% canopy cover increased by 1.5 to 5-fold and treeless area decreased by 17–111%. Mesic areas and areas of sparse tree cover close to existing forest tended to gain more canopy cover. Subsequent wildfires caused a mix of net tree cover loss, little change and gain relative to 1953/1955, but at all sites areas with > 25% cover and < 10% cover in 1953/55 experienced net losses and gains respectively by 2016. Conclusions: Accounting for initial tree cover and its configuration are crucial to assessing water balance and terrain effects on tree cover change. Our work highlights how wildfires can generate novel patterns of tree cover relative to historical baselines, especially following decades of fire exclusion.
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U2 - 10.1007/s10980-020-01178-3
DO - 10.1007/s10980-020-01178-3
M3 - Article
AN - SCOPUS:85099379971
SN - 0921-2973
VL - 36
SP - 353
EP - 371
JO - Landscape Ecology
JF - Landscape Ecology
IS - 2
ER -