Tracking downed dead wood in forests over time: Development of a piece matching algorithm for line intercept sampling

Abstract

Emerging questions from bioenergy policy debates have highlighted knowledge gaps regarding the carbon and biomass dynamics of individual pieces of coarse woody debris (CWD) across the diverse forest ecosystems of the US. Although there is a lack of long-term measurements of CWD across the diverse forest ecosystems of the US, there is an abundance of line intersect sampling (LIS) transects used for monitoring efforts such as fuel loadings. In order to provide an objective method for monitoring the carbon/biomass dynamics of individual CWD pieces for use with LIS, this study developed and tested a CWD piece matching algorithm for inventory plots where LIS was used to sample CWD at two points in time across the eastern US. Results indicated that a CWD piece matching algorithm may be constructed using three steps: (1) matching the location of each piece, (2) matching individual piece metrics (e.g., large-end diameter), and (3) scoring an index of many CWD attributes with adjustment by decay and measurement error (i.e., quality control tolerances). For most forest types in the US, this study’s algorithm matched between 20% and 40% of CWD pieces over time (≈5years). The algorithm performed poorly in forests potentially disturbed by floods and/or with relatively high mean annual temperatures and subsequent fast decay rates. Due to this influence of decay, the algorithm attained low match rates for highly decayed or small-sized CWD pieces. The algorithm should not be used to estimate changes in carbon/biomass within a stock change accounting framework. However, the algorithm may provide a method to aggregate a subset of paired LIS CWD observations over time to inform CWD dynamics research at large-scales.