Patterns of riparian and in-stream large woody debris across contrasting stand ages in a southern Appalachian forest

Abstract

Large woody debris (LWD) has been credited as an important structural and functional component of riparian and in-stream ecosystems. LWD that recruits from riparian zones into stream bankfull margins is crucial in understanding the connectivity between the two ecosystems. The amount of riparian zone and in-stream LWD is closely linked to the time since last disturbance and successional patterns following that disturbance or disturbance events. However, this relationship is poorly understood in southern Appalachian landscapes. I analyzed the amount and volume of LWD in stands of contrasting establishment ages in the Sipsey Wilderness of the Bankhead National Forest, Alabama and the large woody debris loading in streams that were contained within three establishment classes. The establishment classes span 60 years (pre-1900s to 1950s) and incorporate three stages of forest development: stem exclusion, understory reinitiation, and understory reinitiation that is transitioning into complex. The most often cited pattern of LWD loading across forest ages is a parabola shape. However the abundance and volume of LWD across the establishment classes in the study area followed a bell shape pattern with the highest amount and volume of riparian zone LWD in the 1930s age class. In this establishment class mean volume of LWD per plot was 5.62 m3 ± 1.17 SE compared to 4.26 m3 ± 0.60 SE in the pre-1900s establishment class and 5.09 m3 ± 0.59 SE in the 1950s establishment class. Mean density and mean volume of riparian zone LWD per plot did not significantly differ across the chronosequence. The mean volume of in-stream LWD followed the same bell shape pattern with the highest mean volume of in-stream LWD per plot also occurring in the 1930s establishment class (2.50 m3 ± 0.72 SE). However, there was no significant difference in the density or volume of in-stream LWD across the chronosequence. Not only does this study provide specific LWD abundance and volume for specific stand ages but it also can provide baseline data for mature Quercus stands. In addition, my research begins to explore how stand dynamics influences LWD in a southern Appalachian system. (Published By University of Alabama Libraries