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

We make available here published and unpublished data from two provenance tests series, one established in 1967 (Bey, 1973; Bey and Williams, 1974) and another established in 1980 (Waite et al., 1988).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

本数据集公开了两套种源试验（provenance test）的已发表与未发表数据：一套始建于1967年（Bey, 1973; Bey and Williams, 1974），另一套始建于1980年（Waite et al., 1988）。
试验地概况：本试验系列共设3处试验点，分别位于美国印第安纳州、宾夕法尼亚州与佛蒙特州，共评估了黑核桃（black walnut）分布区内的92个天然种群。
各试验点均采用随机完全区组设计（randomized complete block design）：印第安纳州与佛蒙特州试验点设6个区组，宾夕法尼亚州试验点设5个区组，小区为4株树的行状种植区。每个种群在每个区组内以4株树为代表，因此每个种群的总植株数为20~24株，具体取决于试验的区组数量。
定植时苗木均为1年生，印第安纳州试验点的株距为3.7米，宾夕法尼亚州为3米，佛蒙特州为2.5米。
各试验点均记录了所有种群在播种后2~11年多个龄期的总树高。经过6个生长季，宾夕法尼亚州试验点的苗木存活率为90%；佛蒙特州试验点经过7个生长季后存活率达91%。印第安纳州试验点在7个生长季后的存活率仅为61%，原因为早年发生了局部淹水与根腐病（root rot）问题；但存活率与种群起源并无关联（Bey and Williams, 1974）。在印第安纳州试验中，于第三个生长季初期在每株试验树周围种植了黏桤木（Alnus glutinosa）。
本研究所用数据：我们提取了每个种群在各龄期、各试验点的平均树高。因此，区组与单株水平的数据未纳入本数据集（并非所有试验点都留存了此类数据）。此处的龄期以播种时间为基准计算。
为尽可能消除引种距离对各种群固有生长潜力表达的影响，我们仅保留了“试验点气候与种群原生地气候温差在±2℃以内”的观测数据。经此筛选，本数据集纳入的天然种群数量降至52个，总观测数为342条。
本数据集还包含了所有种群与试验点1961—1990年的年平均温度气候正常值（climate normals）。该数据源自Rehfeldt发布的1公里分辨率北美气候表面数据集（Rehfeldt, 2006；数据可从http://charcoal.cnre.vt.edu/climate获取）；1961—1990年为种子采集前的气候时段，因此可准确反映种群原生地气候与试验开展期间的气候状况。
参考文献：
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.