Shubhi Sharma1, Robert Andrus2, Mélaine Aubry-Kientz3, Yves Bergeron4, Michal Bogdziewicz5, Don C. Bragg6, Natalie L. Cleavitt7, Susan Cohen8, Elizabeth Crone9, Adrian Das10, Michael C. Dietze11, Timothy J. Fahey12, Istem Fer13, Jerry Franklin14, Catherine Gehring15, Greg Gilbert16, Katie Greenberg17, Qinfeng Guo18, Janneke Hille Ris Lambers19, Ines Ibanez20, Jill Johnstone21, Christopher L. Kilner22, Johannes M. H. Knops23, Walter D. Koenig24, Jalene LaMontagne25, James A. Lutz26, Jordan Luongo27, Diana S. Macias28, Eliot McEntire29, Yassine Messaoud30, Christopher M. Moore31, Emily Moran32, Orrin Myers33, Jonathan A. Myers34, Chase Nunez35, Robert R. Parmenter36, Sam Pease22, Miranda D. Redmond37, Chantal D. Reid38, Kyle Rodman39, C. Lane Scher40, William H. Schlesinger41, Amanda M. Schwantes42, Michael A. Steele43, Nathan L. Stephenson44, Samantha Sutton45, Jennifer J. Swenson46, Margaret Swift47, Thomas T Veblen48, Amy V. Whipple49, T.G. Whitham49, Andreas P. Wion50, Kai Zhu51, Roman I. Zlotin52 and James Clark53, (1)Nicholas School of Environment, Duke University, Durham, NC, (2)Colorado University, (3)school of natural sciences, UC Merced, Merced, CA, (4)Forest Research Institute, University of Quebec in Abitibi-Temiscamingue, Rouyn-Noranda, QC, Canada, (5)Department of Systematic Zoology, Adam Mickiewicz University, Poznan, Poland, (6)USDA Forest Service, Southern Research Station, Monticello, AR, (7)Natural Resources, Cornell University, Ithaca, NY, (8)University of North Carolina, (9)Department of Biology, Tufts University, Medford, MA, (10)USGS Western Ecological Research Center, Three Rivers, CA, (11)Earth and Environment, Boston University, Boston, MA, (12)Department of Natural Resources, Cornell University, Ithaca, NY, (13)Finnish Meteorological Institute, Helsinki, MA, Finland, (14)Forest Resources, University of Washington, WA, (15)Northern Arizona University, Flagstaff, AZ, (16)University California Santa Cruz, (17)Bent Creek Experimental Forest, USDA Forest Service, Asheville, NC, (18)Eastern Forest Environmental Threat Assessment Center, USDA Forest Service - Southern Research Station, Asheville, NC, (19)Department of Biology, University of Washington, Seattle, WA, (20)University of Michigan, (21)Biology, University of Saskatchewan, Saskatoon, SK, Canada, (22)Duke University, Durham, NC, (23)School of Biological Sciences, University of Nebraska, Lincoln, NE, (24)Lab of Ornithology, Cornell University, Ithaca, NY, (25)Department of Biological Sciences, DePaul University, Chicago, IL, (26)Department of Wildland Resources, and the Ecology Center, Utah State University, Logan, UT, (27)Duke University, (28)Department of Biology, University of New Mexico, Albuquerque, NM, (29)Pacific Forestry Centre, (30)University of Quebec, (31)Biology, Case Western Reserve University, Cleveland, OH, (32)School of Natural Sciences, UC Merced, Merced, CA, (33)University of New Mexico, Albuquerque, NM, (34)Department of Biology, Washington University in St. Louis, St. Louis, MO, (35)Universität Leipzig, German Centre for Integrative Biodiversity Research (iDiv), (36)Valles Caldera National Preserve, National Park Service, Jemez Springs, NM, (37)Forest and Rangeland Stewardship, Colorado State University, Fort Collins, CO, (38)Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC, (39)University of Colorado, Boulder, CO, (40)University Program in Ecology, Duke University, Durham, NC, (41)Cary Institute of Ecosystem Studies, Millbrook, NY, (42)Ecology & Evolutionary Biology, University of Toronto, Toronto, ON, Canada, (43)Biology Department, Wilkes University, Wilkes-Barre, PA, (44)Sequoia and Kings Canyon Field Station, United States Geological Survey, Three Rivers, CA, (45)Biological Sciences, Duke University, Durham, NC, (46)Nicholas School of the Environment, Duke University, Durham, NC, (47)Nicholas School for the Environment, Duke University, Durham, NC, (48)Geography, University of Colorado, CO, (49)Biological Sciences, Northern Arizona University, Flagstaff, AZ, (50)Department of Forest and Rangleland Stewardship, Colorado State University, Fort Collins, CO, (51)University of California, Santa Cruz, (52)Geography, Indiana University, Bloomington, IN, (53)Statistical Science, Duke University, Durham, NC
Background/Question/Methods Global forest diebacks are the beginnings of change that will be controlled by tree migration, which combines two uncertain processes, tree fecundity and recruitment. Knowledge of how, and how fast, tree migration can proceed is critical for adaptive management of forest resources and conservation efforts. The initial stage of seed production is erratic and poorly observed, with most studies limited to few trees of few species on few sites. At the next stage, tree recruitment is typically too sporadic to characterize at landscape scales. Neither seed production nor seedling recruitment have been quantified or linked to climate and habitat variables at scales needed to evaluate the changes happening now or to anticipate the diversity and structure of 21st century forests. As part of the masting inference and forecasting (MASTIF) project, we synthesized continental-scale data for tree fecundity gathered over the last half century and combined it with forest inventories to connect adult trees (basal area) to i) fecundity (seeds per basal area) and ii) recruitment (recruits per seed). A dynamic model fitted to > 107 tree years of fecundity data provided estimates tree-by-year fecundity. A predictive distribution for the continent combines the fitted model with > 105 trees from Forest Inventory Analysis (FIA), Canadian National Forest Inventory (CNFI) and the National Ecological Observatory Network (NEON).
Results/Conclusions
Results show continent-wide tree migration as a balance between regional shifts in fecundity that can diverge from conditions that favour establishment, with clear differences in eastern and western North America. In moist eastern states, the geographic centers for fecundity are most commonly displaced south of tree basal area for the same species. This relationship would be expected if optimal conditions for seed production lie to the south of optimal conditions for growth and survival, despite potential benefits of warming poleward. In the dry west and north-central, fecundity is for most species displaced northwest of tree basal area, as would be expected if the high-rainfall NW is predisposed to lead migration as the continent warms. The east-west contrast diminishes at the transition from fecundity to recruits per seed, which tends to be shifted north in both regions. The net continent-wide migration by contrasting east-west controls highlight interactions, with fecundity primed to lead tree migration in the west, and fecundity slowing progress in the east. The possibility of fecundity limitation offers one explanation for migration lag in species expected to track climate warming by expanding poleward.
