Will changes in phenology track climate change? A study of growth initiation timing in coast Douglas-fir.
Under climate change, the reduction of frost risk, onset of warm temperatures and depletion of soil moisture are all likely to occur earlier in the year in many temperate regions. The resilience of tree species will depend on their ability to track these changes in climate with shifts in phenology that lead to earlier growth initiation in the spring. Exposure to warm temperatures ('forcing') typically triggers growth initiation, but many trees also require exposure to cool temperatures ('chilling') while dormant to readily initiate growth in the spring. If warming increases forcing and decreases chilling, climate change could maintain, advance or delay growth initiation phenology relative to the onset of favorable conditions. We modeled the timing of height- and diameter-growth initiation in coast Douglas-fir (an ecologically and economically vital tree in western North America) to determine whether changes in phenology are likely to track changes in climate using data from field-based and controlled-environment studies, which included conditions warmer than those currently experienced in the tree's range. For high latitude and elevation portions of the tree's range, our models predicted that warming will lead to earlier growth initiation and allow trees to track changes in the onset of the warm but still moist conditions that favor growth, generally without substantially greater exposure to frost. In contrast, toward lower latitude and elevation range limits, the models predicted that warming will lead to delayed growth initiation relative to changes in climate due to reduced chilling, with trees failing to capture favorable conditions in the earlier parts of the spring. This maladaptive response to climate change was more prevalent for diameter-growth initiation than height-growth initiation. The decoupling of growth initiation with the onset of favorable climatic conditions could reduce the resilience of coast Douglas-fir to climate change at the warm edges of its distribution.
USDA Forest Service, Pacific Northwest Research Station, 3625 93rd Ave SW, Olympia, WA, 98512, USA. kford10@gmail.com.
Kevin R
KR
Ford
USDA Forest Service, Pacific Northwest Research Station, 3625 93rd Ave SW, Olympia, WA, 98512, USA.
Constance A
CA
Harrington
USDA Forest Service, Pacific Northwest Research Station, 3625 93rd Ave SW, Olympia, WA, 98512, USA.|US Geological Survey, Northern Prairie Wildlife Research Center, 8711 37th St SE, Jamestown, ND, 58401, USA.
Sheel
S
Bansal
USDA Forest Service, Pacific Northwest Research Station, 3625 93rd Ave SW, Olympia, WA, 98512, USA.|Washington Department of Natural Resources, 1111 Washington St SE, Olympia, WA, 98501, USA.
Peter J
PJ
Gould
USDA Forest Service, Pacific Northwest Research Station, 3200 SW Jefferson Way, Corvallis, OR, 97331, USA.
J Bradley
JB
St Clair
D057231:Climate Change; D009656:North America; D063245:Plant Development; D028224:Pseudotsuga; D012621:Seasons; D014197:Trees
Pseudotsuga menziesii var. menziesii; bud break; budburst; cambial reactivation; climate change; dormancy; flushing; leaf-out; parallel model; phenology