Ionic balance and organic acids in western redcedar, western hemlock, and Douglas-fir seedlings grown in low- and high-N soils
1999
Graff, J.E. Jr | Hermann, R.K. | Zaerr, J.B.
Seedlings western redcedar (Thuja plicata Donn ex. D. Don), western hemlock (Tsuga heterophylla (Raf.) Sarg.), and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) were transplanted into soils with low and high levels of available NO(3)- (and total N). Current-year foliage was sampled after 10 weeks to determine the effect of N availability on foliar cation-anion balance (C-A) and the concentrations of low molecular weight organic acids of the three species. Carboxylate concentrations were estimated by using the difference between sums of cations and anions (C-A): 750 mequiv.(.)kg(-1) for western redcedar, 351 mequiv.(.)kg(-1) for western hemlock, and 266 mequiv.(.)kg(-1) for Douglas-fir. Quinic acid was a primary constituent, accounting for 40% of the total for western redcedar and 75% for western hemlock and Douglas-fir. Oxalic acid was present in greatest concentration in the foliage of western redcedar (65 mequiv.(.)kg(-1) but was a minor constituent in western hemlock and Douglas-fir. The quantified acids accounted for only 15% of the C-A of western redcedar but >80% of the C-A of western hemlock and Douglas-fir. A considerable portion of the C-A balance not accounted for in redcedar may be associated with the accumulation of CaCO(3). Litterfall deposition of CaCO(3) may lead to the consumption of H(+) ions and enrichment of exchangeable soil Ca in the rooting zone of long-lived western redcedar trees. No statistically significant differences among the soils were detected with regard to C-A of the concentration of organic acids.
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