Influence of Climate on the Growth of Hybrid Poplar in Michigan

This study examined the influence of climate on cumulative and interannual growth patterns of 18 full-sib families of hybrid poplars (Populus × smithii Boivin) derived from different geographical locations (state counties) of natural stands of aspen parents (trembling aspen (Populus tremuloides Michx.) and bigtooth aspen (Populus grandidentata Michx.)). The hybrids were subsequently planted in 1982 in southern midMichigan at Michigan State University (MSU) Sandhill Research Area. Cumulative measures of hybrid poplar productivity (diameter, height, basal area, and stem volume) in 2009 (28 years since plantation establishment) were related via correlation analysis to geographical distances and climatic variables (temperature and precipitation) between parental county locations and between parental locations and the plantation site. Tree-ring analysis methods (dendrochronology) were also used to quantify the influence of climate (i.e., mean temperature and total precipitation at monthly and 3-month seasonal scales) on interannual basal area growth rates of hybrid poplars. Analyses of cumulative measures of growth indicated a maternal effect: full-sib families had higher productivity if they had a maternal parent originating from a state county that was close to or had higher temperature (annual and summer) and summer precipitation than corresponding parameters of the planting site. Principal component analysis indicated that 17 of the 18 full-sib families shared a large amount of common growth variation. Dendrochronological analyses of interannual growth-climate relationships indicated that growth was mainly affected by the degree of late summer to fall moisture stress in both the current and previous growth season, and the degree of winter harshness.