Effects of Divalent Metal Chlorides on Respiration and Extractable Enzymatic Activities of Douglas-Fir Needle Litter

摘要

The rates of CO2 evolution from Douglas-fir (Pseudotsuga menziesii Franco) needle litter, following application of divalent metal (Hg, Cd, Pb, Ni, Zn, and Cu) chlorides at rates of 10, 100, and 1,000 microgram/g and Ca chloride at 7, 68, and 683 microgram/g were monitored at 2- to 3-day intervals for 4 weeks; extractable enzymatic activities, were also measured on additional samples 1 day, 2, and 4 weeks following treatment. All metals except Pb inhibited respiration when applied at the highest level. Cellulase activity was depressed by treatment of 1,000 microgram/g of either Hg or Cd after 4 weeks but was not affected initially (1 day after). After 4 weeks, xylanese activity was also depressed by the 1,000-microgram/g Hg treatment. Apparently these enzymatic activities declined due to decrease enzyme synthesis associated with inhibited microbial growth rather than by direct enzymatic inhibition.