Urban influence on changes in linear forest edge structure

Abstract

Urbanization has been a significant cause of deforestation throughout the latter half of the 20th century, and given global demographic trends, the conversion of forested land to urban uses will likely continue. California has had a long history of converting forests, and urbanization has been one of the principle drivers. While many studies have examined how urbanization alters forest landscape structure at landscape or regional scales, little is known about how urban development influences linear forest edge structure at local scales where individual homeowner decisions dominate. We studied how forest edges at two California coastal oak woodlands (Pacheco Valle (PV) and China Camp (CV)) in the San Francisco Bay Area in California changed in the decades following urbanization. Using remote sensing and object-based image analysis, we isolated 20 urban-forest edges per site and quantified each edge's complexity (measured by sinuosity) for three time points at each site. Edges exhibited low sinuosity immediately following development (PV = 1.584, CC = 1.5625), but grew significantly more complex (in 2003 PV = 1.8705, CC 1.906). Linear forest edge structure at both sites, despite different development dates, showed similar and statistically significant increases in sinuosity by 2003. We attribute the initial, more linear structure to mortality and trunk or canopy damage caused by construction, while ascribing the later, more complex structure to tree recruitment, canopy expansion, and homeowner actions that influence natural processes.