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5 10 15 20 25 30 35 40 Lignin concentration (%)

FIGURE 5.3. Simple correlation-regression between initial lignin concentration (%) and annual decomposition rate (k) for five locations ranging in climate from subpolar to warm temperate. AET, actual evapotranspiration (from Meentemeyer, 1978, with permission).

was the overriding variable. Similarly, in a hardwood forested ecosystem at Coweeta Hydrologic Laboratory, in North Carolina, decomposition did not vary predictably along an elevation gradient (Hoover and Crossley, 1995). Decomposition was slowest at a low-elevation, very mesic, cove hardwood site and was most rapid at intermediate elevation sites. Microclimate—temperature and moisture around decomposing substrates— regulates activity rates of the biota. Disturbed ecosystems and successional ones also may have litter breakdown rates that are slower than predicted from broad regional temperature-moisture conditions. Alteration of microclimates may reduce faunal activities, and substrate quality of foliage may change during plant succession. Furthermore, edaphic factors, particularly soil texture (i.e., relative proportions of sand, silt, and clay), greatly influence local microclimatic conditions by regulating the availability of surface water films for soil microbes and microfauna, and water holding capacity of the bulk soil for meso- and macrofauna. Thus soil-water relations exert indirect control on litter decomposition through their influence on soil biological activity.

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