DOI: 10.5061/dryad.6t1g1jwz9
title: Data from: Ecological genetics of Juglans nigra: differences in early growth patterns of natural populations

description: Many boreal and temperate forest tree species distributed across large
 geographic ranges are composed of populations adapted to the climate they
 inhabit. Forestry provenance studies and common gardens provide evidence
 of local adaptation to climate when associations between fitness traits
 and the populations’ home climates are observed. Most studies that
 evaluate tree height as a fitness trait do so at a specific point in time.
 In this study, we elucidate differences in early growth patterns in black
 walnut (Juglans nigra L.) populations by modeling height growth from seed
 up to age 11. The data comprise tree height measurements between ages 2 to
 11 for 52 natural populations of black walnut collected through its
 geographic range and planted in one or more of 3 common gardens. We use
 the Chapman-Richards growth model in a mixed-effects framework and test
 whether populations differ in growth patterns by incorporating
 populations’ home climate into the model. In addition, we evaluate
 differences in populations’ absolute growth and relative growth based on
 the fitted model. Models indicated that populations from warmer climates
 had the highest cumulative growth through time, with differences in
 average tree height between populations from home climates with a mean
 annual temperature (MAT) of 13 °C and of 7 °C estimated to be as high as
 80% at age 3. Populations from warmer climates were also estimated to have
 higher and earlier maximum absolute growth rate than populations from
 colder climates. In addition, populations from warm climates were
 predicted to have higher relative growth rates at any given tree size.
 Results indicate that natural selection may shape early growth patterns of
 populations within a tree species, suggesting that fast early growth rates
 are likely selected for in relatively mild environments where competition
 rather than tolerance to environmental stressors becomes the dominant
 selection pressure.
description: We make available here published and unpublished data from two
 provenance tests series, one established in 1967 (Bey, 1973; Bey and
 Williams, 1974) and another established in 1980 (Waite et al.,
 1988). General description of experimental
 sites: the experimental series comprised three test sites
 located in Indiana, Pennsylvania, and Vermont, USA, and evaluated a total
 of 92 natural populations from the black walnut range. Each test site
 followed a randomized complete block design (6 blocks in Indiana and
 Vermont, and 5 in Pennsylvania), with four-tree row plots. Each population
 was, then, represented by 4 trees per block for a total of 20 to 24 trees
 depending on the number of blocks in the study. Seedlings were 1 year old
 at planting and were planted 3.7 m apart in Indiana, 3 m apart in
 Pennsylvania, and 2.5 m apart in Vermont. At each site, total tree height
 was recorded at several ages between 2 to 11 years from seed for all
 populations. Survival was 90% in Pennsylvania after 6 growing seasons, and
 91% in Vermont after 7 growing seasons. In Indiana, survival after 7
 growing seasons was 61% due to partial flooding and root rot issues in the
 earlier years; however, survival was not correlated with population origin
 (Bey and Williams, 1974). In the Indiana test, <i>Alnus
 glutinosa</i> was planted around each test tree at the beginning of
 the third growing season. Data used in the
 study: we used the average tree height of each population at
 each age and test site. Therefore, block and tree level data are not
 included in this dataset (they were not available for all sites). Age here
 is recorded from seed. We used only the observations where populations
 were transferred to a test site within +/-2 °C of the population home
 climate to minimize the effect of transfer distance in the expression of
 innate growth potential for each population. This reduced the number of
 populations used, and available here, to 52 natural populations, and to a
 total of 342 observations. We also include climate normals for mean annual
 temperature for the period of 1961–1990 for all populations and test
 sites. These were obtained from Rehfeldt’s climate surfaces for North
 America at 1 km resolution (Rehfeldt, 2006; data available at http://charcoal.cnre.vt.edu/climate); this time period represents the climate prior to seed collection, and thus is a good representation of the population’s home climate as well as the climate during the test period. Citations Bey, C.F., 1973. Growth of black walnut trees in eight midwestern states- a provenance test. U.S.D.A Forest Service Research Paper: NC-91. Bey, C.F., Williams, R.D., 1974. Black walnut trees of southern origin growing well in Indiana. Proceedings of the Indiana Academy of Science 84:1. Rehfeldt, G.E., 2006. A spline model of climate for the Western United States (No. RMRS-GTR-165). U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Ft. Collins, CO. https://doi.org/10.2737/RMRS-GTR-165. Waite, C.E., DeHayes, D.H., Turner, T.L., Brynn, D.J., Baron, W.A., 1988. Black Walnut Seed Sources for Planting in Vermont. North. J. Appl. For. 5: 40–45. https://doi.org/10.1093/njaf/5.1.40.