Coarse woody debris inputs and spatial arrangement as artifacts of past management practices

Background/Question/Methods

The ecosystem management paradigm embraces the restoration and maintenance of ecological processes across many scales, and coarse woody debris (CWD) is an essential element of forest ecosystems. Standing (SDW) and down dead wood (DDW) are important components whose many ecological roles are well documented, but our knowledge of management impacts on this resource is not well understood. Because CWD in hardwood forests has slow decay rates, it can influence ecological processes at local, stand, and landscape levels for several decades. Forest stands subject to management will experience long-term changes to CWD dynamics, thus, influencing future spatiotemporal inputs of CWD. We examined the quantity, quality, and spatial arrangement of CWD in a relict forest and two managed forests. We used variable radius plots on a 10 m x 10 m grid to sample stands. For DDW we measured large and small end diameters and length, and for SDW we measured diameter and height; decay classes were assigned to each. We evaluated connectivity of DDW in stands 46 years after partial harvests. We hypothesized: 1) the amount of CWD would be lower in managed stands; 2) distribution of DDW and SDW would exhibit higher levels of connectivity in the relict stand.

Results/Conclusions

We observed significantly smaller individual piece sizes of DDW and SDW in managed stands compared to the relict stand. The relict stand had more pieces/ha and 2 times more volume/ha of DDW. Compared to the relict stand, the managed stand harvested twice had almost twice as many pieces SDW/ha, but less than a third of the volume/ha. The relict stand had greater abundance/ha and volume/ha of CWD and SDW in advanced stages of decay and larger diameter classes. Connectivity in the relict stand was 56% across seven patches for large pieces (≥ 60 cm). In the double-harvest stand for the same size threshold, connectivity was only 17% across two patches. After 46 years with no intervention, managed stands had fewer pieces, smaller pieces, and lower volume/ha for CWD and SDW compared to the relict stand. Partial harvests alter stand structure and development patterns, which in turn influence CWD dynamics for several decades after the harvest event. Forest management plans guided by ecosystem management principles should consider and plan for the long-term impacts of harvests on CWD.