Patterns of fine scale deadwood distribution in an Ozark Highlands forest

Background/Question/Methods

               The abundance, structure and distribution of deadwood provide wildlife habitat, tree regeneration sites, and carbon and nutrient storage in forests. Usually evaluated per hectare, deadwood distribution is heterogeneous at much smaller spatial scales. The fine scale location of a tree can have important implications for its decomposition. How long a tree stands dead and the time it resides on the forest floor while decomposing may depend on its exposure to mechanical disturbance (e.g. wind), or factors influencing decay communities (e.g. solar radiation and moisture). In July 2012, we exhaustively mapped and measured deadwood on a long-term forest plot located in the Missouri Ozark highlands that is dominated by Quercus velutina, Quercus alba, and Carya tomentosa. The topography is characterized by rocky, dry ridges with steep slopes down to small drainages. We exhaustively mapped all deadwood on 100 20 m by 20 m quadrats within the plot. We calculated deadwood volume, slope and aspect of each quadrat and classified them by elevational position: ridge-top, mid-slope, or ravine. We expect ravines to have the highest volume of deadwood, while areas with steep slopes will have fewer snags and lower overall deadwood volumes.

Results/Conclusions

               Deadwood volume varied across quadrats by an order of magnitude (lowest deadwood volume = 0.177 m³, highest deadwood volume = 6.384 m³). There were significantly higher volumes of deadwood in plots that were located in ravines, with the lowest average volume of deadwood found on ridge-tops. However, there was no significant difference in the number of deadwood pieces at different elevational positions. The volume of snags also did not significantly vary with elevational position, but there was a trend towards higher snag volumes in ravine quadrats. The patterns observed in this study indicate that there are differences in deadwood levels correlated with topography. However, it remains to be seen whether this variation is due to higher tree mortality, increased decomposition rates, gravity depositing deadwood down slope, or if it is an artifact of ravine sites being more productive and producing larger trees that eventually enter the deadwood pool.