Litter decomposition in coastal hemlock stands: impact of nitrogen fertilizers on decay rates

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Abstract
Urea, gypsum-coated urea, and calcium nitrate fertilizers differentially affected indigenous rates of litter decomposition on the forest floor for coastal stands of western hemlock (Tsugaheterophylla (Raf.) Sarg.). These differences were most pronounced during the first 6 months after fertilization. Urea and gypsum-coated urea both stimulated the rates of litter decomposition, although the effect of gypsum-coated urea was more gradual. In contrast, calcium nitrate somewhat retarded existing decomposition rates during the first 6 months; after 12 months, it had little or no impact. The significant (P < 0.05) positive correlation of percentage of lignin in litter with time renders it an important qualitative measure of decomposition rates in studies utilizing litter bags.