Abstract
Water limitation during tree seedling cultivation can promote traits that improve drought hardiness. Nurseries apply water limitation mostly during a brief developmental window of seedling growth, which may restrict the range of useful traits achievable through water limitation if phenotypic responses differ across ontogeny. We characterized the diversity of western larch ( Larix occidentalis (Nutt.)) seedling traits produced by four factorial combinations of low- and high-watering regimes spanning the first and second years of growth. Seedlings from all watering treatments were exposed to ten days of water withholding during a drought pulse trial at the end of year two preceding destructive measurements. Seedling stem water potential ( Ψ ) measurements recorded before, during, and after the drought pulse trial suggested that water-limited cultivation in the second year and consecutively across both years resulted in the greatest mid-day Ψ (least moisture stress) during the drought pulse and the greatest integrated water use efficiency. Seedlings cultivated with limited water in the second year and consecutively across both years expressed similar traits and performance during the drought pulse, suggesting that previous exposure to drought did not moderate seedling responses to subsequent water limitation. Water-limited cultivation in year one resulted in a greater number of root branch nodes and mass of egressed roots given ample water in year two, but not when water was limited in year two. Evidence suggests that seedlings express age-dependent phenotypic responses to water limitation that promote belowground growth best when applied during the first year except in dry transplanting environments.