Masters Thesis

Comparison of residual structure, recovery, and diversity in clearcut and "new forestry" silvicultural treatments at the Yurok Experimental Forest, a coast redwood type

There is much debate over the sustainability of monoculture plantation forest management. "New Forestry" or "Ecosystem Management" has maintenance of total biodiversity across the landscape as a primary objective. Ecosystem management techniques require leaving significant amounts of biological and structural legacies after disturbance by logging in order to encourage the rapid recovery of ecosystem biodiversity. This descriptive research, completed in the Yurok Experimental Forest (YEF) in Klamath, California, compared the composition of residual vegetation and revegetation of the tree and shrub layers of coastal redwood forest following select and clearcutting at 14 and 29 years after harvest, respectively. Measurements of managed stands were contrasted with measurements in unmanaged, old-growth stands. Terrestrial coarse woody debris (both residual and recruited since logging) was measured in oldgrowth, selection cut and clearcut stands as one representative offorest structure. Cluster analysis and divisive classification grouped most selection cut and all clearcut plots together and created a separate group for old-growth plots when comparing combined tree and shrub data. Out of 12 plots sampled for each treatment, cluster analysis and divisive classification grouped three (25%) and zero selection cut plot(s) with the old-growth group, respectively. Utilizing Shannon's and Simpson's diversity indices to analyze tree and shrub data, clearcut plots were the least diverse and selection cut plots were the least even. Samples in old-growth were the most even and more diverse than selection cut and clearcut plots using Simpson's index and more diverse than clearcut plots using Shannon's index. Selection cut plots were more diverse than clearcut plots using both indices. Sample plots were stratified by vertical layers and broken into the shrub, tree, pole, sapling and seedling layers in order to compare composition and structure between treatment types. Sampled old-growth plots had significantly lower overall cover in the tree and pole layers and the highest overall cover in the shrub layer. Selection cut plots were similar to old-growth plots in overall shrub cover. Clear-cut plots resembled oldgrowth plots in the sapling layer. For coarse woody debris (CWD), there were substantial reductions in volume ofredwood CWD in select and clearcuts and the size of pieces were smaller than in oldgrowth. Some of the CWD in selection cuts resulted from residual old-growth trees left during the last logging entry and this type of CWD more closely resembled CWD in oldgrowth areas. Most of the redwood CWD in select and clearcut plots seemed to derive from slash and cull logs. Over time and given additional logging entries, this source of CWD will diminish, especially as cull is reduced when timber rotations are reduced to 60-80 years. Selection cut sample plots resembled old-growth plots more than clearcut sample plots at the YEF. There were also many dissimilarities between old-growth plots and selection cut plots and similarities between selection cut and clearcut plots. Additional research is needed before it is known whether ecosystem management techniques applied in New Forestry selection cutting will meet the objective of maintaining total biodiversity across the redwood ecosystem landscape.

Items in ScholarWorks are protected by copyright, with all rights reserved, unless otherwise indicated.