ANATOMICAL, CHEMICAL, AND ECOLOGICAL FACTORS AFFECTING TREE SPECIES CHOICE IN DENDROCHEMISTRY STUDIES

Recently, element concentrations in tree rings have been used to monitor metal contamination, fertilization, and the effects of acid precipitation on soils. This has stimulated interest in which tree species may be suitable for use in studies of long-term trends in environmental chemistry. Potential radial translocation of elements across ring boundaries can be a confounding factor in assessing environmental change. Thus, the selection of species which minimizes radial translocation of elements can be critical to the success of dendrochemical research. Criteria for the selection of species with characteristics favorable for dendrochemical analysis are categorized into (i) habitat-based factors, (ii) xylem-based factors, and (iii) element-based factors. Species with a wide geographic range and ecological amplitude provide an advantage in calibration and better controls on the effects of soil chemistry on element concentrations. The most important xylem-based criteria are heartwood moisture content, permeability, and the nature of the sapwood-heartwood transition. The element of experimental interest is important in determining which tree species will be suitable because all elements are not equally mobile or detectable in the xylem. Ideally, the tree species selected for dendrochemical study will be long-lived, grow on a wide range of sites over a large geographic distribution, have a distinct heartwood with a low number of rings in the sapwood, a low heartwood moisture content, and have low radial permeability. Recommended temperate zone North American species include white oak (Quercus alba L.), post oak (Q. stellata Wangenh.), eastern redcedar (Juniperus virginiana L.), old-growth Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] and big sagebrush (Artemisia tridentata Nutt.). In addition, species such as bristlecone pine (Pinus aristata Engelm. syn. longaeva), old-growth redwood [Sequoia sempervirens (D. Don) Endl.], and giant sequoia [S. gigantea (Lindl.) Deene] may be suitable for local purposes.