Snags and Down Wood in Missouri Old-Growth and Mature Second-Growth Forests

Abstract

Abstract As forest managers in the Midwest focus more attention toward understanding and maintaining ecosystem processes, greater emphasis is being placed on the role of snags and down wood in providing wildlife habitat, cycling nutrients, and maintaining continuity in forest structure following harvest. We measured five remnant old-growth hardwood tracts and six mature, second-growth, hardwood tracts in Missouri and compared findings concerning (1) the volume of down wood and (2) the number and size distribution of snags (i.e., standing dead trees). Volume of down wood ≥ 10 cm in diameter averaged 36 m³/ha on the old-growth tracts, double the 18 m³/ha mean volume for the second-growth sites. This difference in volume was concentrated in pieces of down wood with diameters larger than 20 cm; below diameters of 20 cm the number of pieces of down wood by diameter class was similar for the old-growth and second-growth sites. On the old-growth sites, the mean basal area of snags ≥ 10 cm dbh was 1.9 m²/ha. This was approximately 1.5 times greater than the mean basal area of snags on the second-growth sites. The number of snags ≥ 10 cm dbh on the old growth sites was approximately 9% pf the number of live trees on those sites. The corresponding value for second-growth sites was 8%. On both the old-growth and second-growth sites, the number of snags and the number of live trees by dbh class followed a negative exponential (reverse-J) form. Frequency distributions for the number of snags by dbh class closely followed those for live trees on the same sites. These results provide managers with general guidelines for the quantity of down wood likely to be found in mature second-growth forests and old-growth forests. We also provide some provisional rules of thumb for estimating the density and size distribution of snags from values observed for live trees in the same stand. North. J. Appl. For. 14(4):165-172.