Structure and Composition of Old-Growth and Unmanaged Second-Growth Riparian Forests at Redwood National Park, USA

Abstract

Abstract:Restoration of second-growth riparian stands has become an important issue for managers of redwood (Sequoia sempervirens [D. Don] Endl.) forest reserves. Identifying differences between old-growth and second-growth forest vegetation is a necessary step in evaluating restoration needs and targets. The objective of this study was to characterize and contrast vegetation structure and composition in old-growth and unmanaged second-growth riparian forests in adjacent, geomorphologically similar watersheds at Redwood National Park. In the old-growth, redwood was the dominant overstory species in terms of stem density, basal area, and importance values. Second-growth was dominated by red alder (Alnus rubra Bong.), Douglas-fir (Pseudotsuga menziesii [Mirbel] Franco), and redwood. Understory species were similar in both forests, with several key differences: Oxalis oregana Nutt. and Trillium ovatum Pursh had greater importance values in the old-growth, and Vaccinium parvifolium Sm., Dryopteris spp. and sedges Carex spp. had greater importance values in the second-growth. Notable differences in structure and composition suggest that restoration practices such as thinning could expedite the acquisition of old-growth characteristics in second-growth riparian forests.

Assessing the Effects of Periodic Flooding on the Population Structure and Recruitment Rates of Riparian Tree Forests

“…Tree age-class structure and distribution are also the most commonly used parameters for describing forest stands and assessing changes in individuals from the same tree species [12][13][14]. These measurements may sometimes be carried over or extrapolated to smaller-scale wooded areas in order to obtain an overview of changes in the forest cover.…”

“…Furthermore, the establishment of the age bracket grouping individuals from the same community or wooded area helps decipher the overall stand structure. This allows changes to the stand to be tracked using different observation scales [14][15][16]. In the natural environment, however, it is known that environmental conditions and various disturbances (allogenic or autogenic) can induce marked differences between the stands, in particular with respect to the composition, structure, tree diameter and age of the individuals [15][16][17].…”

“…In previous studies [4,7,12,14], the sampling sites of the selected stands were often located in controlled experimental sites, natural or protected forest areas, or sites with few environmental constraints. However, studies on riparian vegetation subjected to periodic flooding are rarer [13,18], especially for areas affected by successive flooding, which causes alluvial plain aggradation [5,19].…”

Herbaceous Understory Indicators of Post-Harvest Recovery in Coast Redwood (<i>Sequoia sempervirens</i>) Forests

“…While metrics based on total understory cover and richness are often reported in the literature, these measures are fairly consistent between old-growth and second-growth stands; and thus are not as effective as individual understory species metrics which vary significantly based on individual physiological tolerances (Loya & Jules, 2008;Russell & Michels, 2010;Keyes & Teraoka, 2014). Coast redwood associated understory species such as Asarum coudatum (wild ginger), Lysimachia latifolia (pacific star flower), Oxalis oregana (redwood sorrel), Polystichum munitum (western sword fern), Prosartes hookeri (hooker's fairybells), Trillium ovatum (pacific trillium), and Viola sempervirens (redwood violet) are known to be sensitive to timber harvest, and their abundance has been correlated to forest metrics such as tree density, canopy cover, and tree size (Meier et al, 1995;Gilliam, 2007;Loya & Jules, 2008;Russell, 2009;Russell & Michels, 2010;Russell et al, 2014).…”

“…Trillium ovatum, a rhizomaceuous perennial herb (Case & Case, 1997), is of particular interest as an indicator species as it is long lived and sensitive to timber management in coast redwood as well as other forest types (Kirschbaum & Anacker, 2005;Keyes & Teraoka, 2014). T. ovatum has been shown to grow preferentially in old-growth, as compared to managed, Douglas-fir forests in Oregon (Jules & Rathcke, 1999;Kahmen & Jules, 2005), and other members of (Jenkins & Webster, 2009).…”