Type: report

Article abstract: Monitoring to detect ecological change is an important component of many environmental and conservation programs. The Nature Reserves of Orange County (NROC) hold 38,000 acres enrolled within the Orange County NCCP. NROC is obligated to monitor the condition of conserved lands through time and has identified vegetation communities as targets for long term monitoring. Monitoring this large and heterogeneous area is scientifically and logistically challenging as well as costly. The objective of this project is to evaluate the cost and accuracy of different sampling designs and field protocols for monitoring coastal sage scrub (CSS), chaparral, and grassland vegetation communities. This report covers year two of an ongoing project. The current work emphasizes the importance of spatial coverage across the study area. As a result, we increased the number of sites and plots sampled from the first year of the project. We also eliminated the visual cover protocol and decreased the length of the transects and the number of quadrats at each plot. This year we detected a large increase in plant species richness throughout the county. This was driven largely by the increased diversity of forbs at resampled plots. Shrub cover varied spatially but was similar across years. In addition to richness, the cover of native and non-native forbs and grasses increased dramatically. We used a variance components analysis in order to develop recommendations for optimizing monitoring. We consider three major sources of variation: temporal (interannual), spatial and methodological. Spatial variation includes three nested levels: vegetation community, site and plot. Methodological variation includes two levels: protocol (quadrat vs. point intercept) and team. Several suites of response variables were analyzed including species richness, cover of major functional groups (e.g. native shrubs, non-native forbs), and several example species from each functional group. Semi-arid shrublands in southern California are highly spatial, with different species and functional groups displaying different degrees of affinity for a specific vegetation type or a different degree of patchiness across sites and plots. As a result allocating a significant amount of effort to spatial coverage is appropriate for most response variables. Some species and groups are also dramatically influenced by annual factors such as rainfall, and will require annual monitoring. Team-to-team variability is small