Carbon Sequestration and Land Use History of Redwood Forests in the Santa Cruz Mountains

Abstract

Identification of a consequential increase in atmospheric carbon resulting from human activities has motivated research into the carbon storage potential of forests (Harmon et al. 1990, Hudiberg et al. 2009). The forests of S. sempervirens are the tallest in the world, a quality that has increased their utility in providing timber, sites for recreation, and potential to sequester large amounts of atmospheric carbon (Noss 2000, Koch et al. 2004, Keith et al. 2009). Old-growth redwood forests are extremely massive, but young-growth redwood forests are more productive (Lindquist and Palley 1963, Busing and Fujimori 2005, Sillett et al. 2010). The objective of this thesis is to compare the current carbon stock and change in carbon stock over 77 years of old-growth and second-growth redwood stands located within state and local parks of the Santa Cruz Mountains, by resurveying a historical tree demography dataset collected in 1935 (Kelly 2005, Francis 2012). The second objective of this thesis is to compare the estimates yielded by a national scale carbon prediction equation with those from a carbon prediction equation specific to redwoods (Wensel and Krumland 1986, Jenkins 2003). Carbon content of redwood plots that were harvested before 1935 significantly increased between 1935 and 2012, in contrast to the old-growth plots that showed an insignificant decrease in carbon. Coupled with the significantly lower tree density old-growth redwood forests, the greater tendency for second-growth plots to increase in carbon signifies density dependent limits on carbon accumulation (Keith et al. 2010). The national-scale biomass equation yielded significantly higher carbon estimates for young-growth redwoods, suggesting that it could be improved by formulating biomass equations for species groups that are more specific to their empirically measured wood density values.