Needle litter decomposition
Needles of Pacific silver fir and western hemlock were selected in this study because they are the dominant species and occur in both the upper and lower watershed (Edmonds et al. 1993). Green needles were collected from wind-blown limbs on May 26, 1986 and allowed to air dry at room temperature for approximately 1 month at room temperature. Green needles are an important component of litterfall during storms in the Hoh River Valley. Polyester litterbags with 1 mm mesh and measuring 14 x 14 cm were used. Subsamples were taken to determine moisture and initial chemical constituents. Fifteen g of air-dried litter were placed in each bag. Bags containing either western hemlock and Pacific silver fir needles were placed randomly in 0.1 ha circular plots in the upper (at 725 m elevation) and lower watershed (at 275 m elevation) on July 23, 1986. Collection dates were November 15, 1986 (4 months), July 31, 1987 (12 months), August 22, 1989 (37 months) and August 29, 1991 (61 months). Seven replicate bags were sampled at each time. Litterbags were transported to the laboratory and needles were dried as soon as possible at 75° C to a constant weight. Ash free dry weights were determined using samples ignited in a muffle furnace at 550° C. Decomposition constants (k values) were calculated using the negative exponential model of Olson (1963).
Microclimate
Daily maximum, minimum and average forest floor temperatures were obtained from July 1986 to October 1988 using thermistors and a battery operated NEC data logger located in the upper (at 730 m elevation) and lower watershed (at 260 m elevation). Chemical analyses Initial litter samples and litter in three randomly selected litterbags collected at 12, 37 and 61 months were used for chemical analyses. Litter was ground to pass through a No. 20 stainless steel screen. Ground liter was digested using the wet oxidation procedure of Parkinson and Allen (1975). Nitrogen and P concentrations were determined using a Technicon autoanalyzer II. Concentrations of K, Ca, Mg, Mn and Na were determined using a Jarrel Ash ICP (Model 61e). Carbon was determined using a Leco carbon analyzer. Lignin concentrations were determined using a modification of the 72% sulfuric acid extraction method of Van Soest (1963). Sintered glass funnels were used without the asbestos mat.