Rapid soil development after windthrow disturbance in pristine forests
1995
Bormann, B.T. | Spaltenstein, H. | McClellan, M.H. | Ugolini, F.C. | Cromack, K. | Nay, S.M.
We examined how rapidly soils can change during secondary succession by observing soil development on 350-year chronosequences in three pristine forest ecosystems in south-east Alaska. Soil surfaces, created by different windthrow events of known or estimated age, were examined within each of three forest stands (0.5-2.0 ha plots; i.e. a within-stand chronosequence method). Soil surfaces are more likely to have developed under common climate and vegetation conditions within stands than in the spatially separated ecosystems used in traditional chronosequence studies. We observed rates of change that were higher than those previously reported for secondary succession, and were similar to those described for primary succession. Well-developed spodic and albic (podzol) horizons with characteristic C, Fe, and Al signatures were found in soil surfaces less than 150 years old. Carbon accumulated linearly at 21 g m-2 year-1; mineral P and N became increasingly immobilized in the spodic horizon as time passed. We found no trend toward an equilibrium in C or N accumulation over the 350-year chronosequences in any of the three stands examined. These rapid changes in soil and a shift in rooting from mineral to organic horizons appeared likely to reduce productive capacity of the soil during a single generation of trees. Windthrow or disturbances that mimic windthrow may be required at intervals of about 200-400 years to maintain soil productive capacity in these ecosystems.
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