Patterns Of Mass Loss During Decomposition

A graph of mass retained in litterbags during decomposition of leaf litter in a temperate deciduous forest reveals a three-phase curve (Fig. 5.9). Initially, following autumnal leaf drop, there is a rapid decrease in weight, caused by the loss of rapidly metabolizable compounds or simply readily leachable substances. This initial phase is followed by a slow rate of loss during winter months. During late spring, rates again become accelerated as microclimates become more favorable

Pine stand Oak stand

Pine stand Oak stand

FIGURE 5.9. Three-phase mass loss curve. Weights of decaying leaves in litterbags, expressed as a percentage of initial weight of litter, through time. Three leaf species in two stands. Hollow circles are individual measurements; solid circles are averages for 8-week cycles. Lines fitted by eye (from Olson and Crossley, 1963).

FIGURE 5.9. Three-phase mass loss curve. Weights of decaying leaves in litterbags, expressed as a percentage of initial weight of litter, through time. Three leaf species in two stands. Hollow circles are individual measurements; solid circles are averages for 8-week cycles. Lines fitted by eye (from Olson and Crossley, 1963).

for biological activity. During winter some microbial and faunal attack occurs, but the major abundance of fauna and microbes is found in litterbags during spring and summer.

Although rates do vary with season, the model using a single exponential constant (k) provides a good fit to these data (Fig. 5.10). The

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