PIT AND MOUND TOPOGRAPHY AND ITS INFLUENCE ON STORAGE OF CARBON, NITROGEN, AND ORGANIC-MATTER WITHIN AN OLD-GROWTH FOREST

Pit and mound microtopography created by tree windthrow is a dominant feature in many old-growth forests in the Great Lakes Region. This stu dy investigated whether stand-level quantities, or processes which con trol quantities, of carbon, nitrogen, and organic matter in forest flo or and mineral soil have been altered by changes in microtopography ca used by windthrow. Comparison of flat or relatively undisturbed surfac es with the areas that contained mounds, pits, and flat features combi ned indicated no changes in the amounts of carbon, nitrogen, or organi c matter in the forest floor or mineral soil as a result of pit and mo und microtopography. However, there was an increased mixing of forest floor organic matter within mineral soils of mounds as compared with p its. Decomposition potential after 10 weeks, as indicated by cotton st rip assay method, was 116% greater within the mineral soils of mounds than in pits. The decomposition rates in the mineral soil in the mound s were related to greater amounts of organic matter, temperatures, and moisture contents within this feature. Changes in sink sizes related to organic matter mixing or alteration in decomposition were minimal. Thus long-term stand-level storage of carbon, nitrogen, or organic mat ter in forest floor or mineral soil pools was not found to be signific antly altered by changes in microtopography resulting from windthrow d isturbance levels found within this study area.