Identification of Old-Growth Forest Reference Ecosystems Using Historic Land Surveys, Redwood National Park, California

摘要

Old-growth forests in the American West typically represent fragments of former, more extensive forests that were subjected to nineteenth and twentieth century land-clearing activities, such as logging. These present-day forest fragments are thought to be representative of the former landscape, and thus are capable of serving as living references for guiding restoration of logged forests. Yet how do we determine the extent to which existing old-growth stands represent the former forest, especially when little of the surrounding original vegetation remains? Historic land surveys conducted prior to significant logging can reconstruct the former forest at the stand level, thereby allowing an analysis of old-growth patches within the larger historic landscape. This study utilized original Public Land Surveys to assess the applicability of old-growth stands in Redwood National Park as reference ecosystems. A geographic information system (GIS) and statistical analysis of the nineteenth century forest found that vegetation communities, woody species composition, and ratios of dominant canopy species in unlogged patches were highly representative of the forests that were logged. Significance testing (H_0: μ1 = μ2) revealed p-values greater than 0.10000 in all measures of community and species composition, except for the higher abundance of oak in present-day old-growth (p-value = 0.0395). The results of this study suggest that the national park should increase efforts to protect old-growth reference ecosystems from further human impacts, and minimize ongoing degradation from edge effects by prioritizing restoration of adjoining second-growth forest.