Identifying the spatial pattern of wood distribution in northeastern North American streams

Abstract

The spatial distribution of instream wood influences important ecological processes but has proven challenging to describe quantitatively. We present a modified version of a previously described metric used to quantify the spatial extent and pattern of instream wood distribution, then apply this approach in evaluating the distribution of wood habitat in forested northeastern North American streams. This revised metric, a ‘binned neighbor-K analysis’, provides greater resolution in evaluating the presence of aggregated, periodic, or segregated wood distributions in stream ecosystems. We employed this metric in evaluating the distribution of wood within 17 streams in two regions of northeastern North America. Our results indicate that the binned neighbor-K approach more accurately represents the spatial extent at which wood accumulates in streams by identifying recurring intervals in streams within which instream wood is not present and by more accurately quantifying the spatial extent of wood aggregations and periodically repeating occurrences of accumulated wood. We also used this metric to quantify the overall extent of wood ‘organization’ in streams, which revealed similarities and differences in instream wood distribution patterns in the two regions evaluated. Wood distribution patterns in both study regions were generally consistent with our expectations of increased organization at an intermediate stream size (up to 10 m bankfull width), then in larger streams (> 10 m) wood was less organized. These observed patterns result from landscape and ecosystem influences upon wood accumulation and movement in streams.