Study design and criteria
This study compared three different forest management practices in and near the riparian zone of headwater streams. A total of nine (n = 9) headwater streams were chosen as field sites; three sites were not recently logged (~ 90 year-old stands), representing relatively undisturbed reference conditions (“reference”); three sites had a riparian buffer (reserve) zone of trees left standing along each side of the stream (“buffer”); and three sites were clear-cut to the stream margin without a riparian buffer zone (“no buffer”).
Field site selection criteria were chosen a priori to identify comparable streams and riparian zones (Table 1). Using geographic information system data provided by MKRF, we identified clear-cut cut-blocks that were harvested no more than five years earlier, in Arcmap 10.6.1 (ESRI, Redlands, CA, USA). The selected buffer and no buffer sites were logged three to five years earlier. At the buffer sites, the average width of the buffer zone was 13.0 ± 2.8 m, and ranged from 11.0 to 16.2 m. The study sites met Richardson and Danehy’s (2007) criteria for a headwater stream of a mean width <3 m and catchment area <100 ha. The riparian zones at the study reaches had a gentle slope gradient below 30°, with an average bank slope of 13.2° ± 8.4 (Table 1). This ensured comparability of groundwater table dynamics between sites, since stream water levels have more control on riparian water table levels when the stream bank slope has a lower gradient (Burt and others 2002).
Table 1. Characteristics of riparian study sites alongside headwater streams under differing forestry management conditions in Malcolm Knapp Research Forest, British Columbia, Canada. Values represent mean ± SD of three sites for each treatment. See Table A1 in Appendix A for the values for each site.
Reference No buffer Buffer
Stream bankfull width (m) 2.3 ± 1.7 1.4 ± 0.7 1.5 ± 0.3
Catchment area (ha) 27.3 ± 19.0 6.63 ± 6.3 11.0 ± 10.8
Elevation (m) 305.5 ± 36.5 329 ± 37.4 369.0 ± 30.6
Reach length (m) 64.0 ± 9.2 46.3 ± 11.2 56.7 ± 41.4
Bank slope (°) 37.7 ± 22.8 18.8 ± 6.6 15.5 ± 8.5
Stream slope (°) 8.7 ± 5.2 7.9 ± 3.7 6.1 ± 4.3