Screening exotic firs for the Midwestern United States: Interspecific variation in adaptive traits

Abstract

Conifers represent a sizeable portion of nursery and landscape sales in the upper midwestern U.S. Several conifer species have been overplanted to the point where disease problems and insect pressures have developed. Although more than 40 true fir (Abies Mill.) exist throughout the northern hemisphere, use of firs in the landscape and Christmas tree industry has been limited to relatively few species. This is largely due to perceived intolerance of many site conditions. However, recent research suggests Abies are more tolerant of varying site conditions than originally thought. Successful introduction of new exotic fir species for landscape use will require a systematic approach to identify species that are adapted to environmental stresses. In this article we review the extent and nature of inter-specific variation among Abies species in traits commonly associated with tolerance of stresses found in the upper midwestern U.S. Specifically, we focus on cold hardiness, budbreak, photosynthetic gas exchange and water relations, and response to soil pH. It is important to match plants possessing necessary adaptive characteristics with the existing site conditions. Therefore, multiple screening factors should be met when identifying species or trees from different provenances for future introduction.