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Data from: Ecological genetics of Juglans nigra: differences in early growth patterns of natural populations


Leites, Laura; Onofrio, Lauren; Hawley, Gary (2022), Data from: Ecological genetics of Juglans nigra: differences in early growth patterns of natural populations, Dryad, Dataset,


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.


We make available here published and unpublished data from two provenance tests series, one established in 1967 (Bey, 1973; Bey and Williams, 1974) and another established in 1980 (Waite et al., 1988).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, Alnus glutinosa 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; 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.


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.

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.


U.S. Forest Service, Award: Joint Venture Agreement 03-JV11242328-001

U.S. Department of Agriculture, Award: Project #PEN04700 and Accession #1019151