Foliar chemical concentrations, growth, and site productivity relations in western red cedar

Abstract

Important site and tree characteristics of western red cedar (Thujaplicata Donn ex D. Don) were examined in 19 natural stands in the coastal and interior zones of western Washington and Oregon, U.S.A., and in western Vancouver Island, British Columbia, Canada. The stands occurred at various elevations and on different soil types and differed in age, soil pH, and associated plant species. Current-year foliage was collected during the winter and concentrations of N, P, K, S, Ca, Mg, Fe, Mn, B, Zn, Cu, Mo, Al, and the chlorophylls were determined. Mean terminal growth during the previous 3 years and site index at 50-year breast-height age were calculated for each stand. Site index ranged from 18 to 26 m. Terminal growth and foliar concentrations of the macronutrients, micronutrients, Al, and the chlorophylls varied among the 19 sites and between the two zones. Compared with known values for the most common associated conifers, foliar concentrations of red cedar were especially low in Mn and Al and high in Ca and Mo. Site index was correlated positively with N, the chlorophylls, S, Cu, and B, and negatively with Fe and Al. Also, N was positively correlated with the chlorophylls and with some of the other nutrients; there were many correlations among the nutrients and between some nutrients and soil pH or stand age. The data obtained provide base-line information for future analytical work with red cedar foliage. In addition, results suggest that (i) nutrient management strategies in western red cedar stands may differ from those for other conifers and different strategies may be necessary for the coastal and interior zones, (ii) productivity of red cedar may be improved by cultural treatments, including fertilization, which would enhance levels of chlorophyll as well as some essential elements (N, S, P, B, and Mo) in the foliage, (iii) levels of some chemicals in the foliage, such as N, chlorophyll, S, and B, may be useful as indicators to assess site quality for red cedar production, and (iv) chlorophyll may be used as a simple means to estimate N status of red cedar.