Prioritization of communities for monitoring was based on the following criteria: representativeness, extent, fragmentation, endangerment and threats. Aggregated communities that received high priority rankings based on several criteria include CSS and meadows & freshwater wetlands. Communities with high endangerment or threats should also receive high priority and include: Southern foredunes, Southern coastal salt marsh, Southern coastal bluff scrub, Maritime succulent scrub, Diegan coastal sage scrub, Southern maritime chaparral, Valley needlegrass grassland, Cismontane alkali marsh, Southern arroyo willow riparian forest, Southern willow scrub, Engelmann oak woodland, Torrey Pine forest, and Tecate Cypress forest.
This report will: describe the current state of the MSCP Preserve, discuss natural community assemblages and alternative vegetation community classifications for the MSCP, describe the use of landscape stratification based on environmental variables as an alternative to vegetation classification, discuss the grouping of communities for the monitoring program, and prioritize natural communities for monitoring protocol development.
This report covers activities performed during our third year of work with Thorne's hairstreak (TH). Activities are summarized with reference to objectives as outlined in our second annual report, and activities for 2013 are projected (the project will come to an end mid- 2013). During the 2011 field season, we completed our surveys for vegetation and TH abundance. Over the course of both of our primary field seasons for this project (in 2010 and 2011), we surveyed a total of 358 plots for vegetation and 255 plots for TH presence and abundance associated with 40 stands of Tecate cypress. A total of 75 TH adults were observed in approximately half of the stands spread throughout the Otay Mountain study area. We also report here on results from habitat modeling, which suggests that host plant variables (e.g. cypress density and tree diameter) are statistically significant predictors of TH presence (while the density and richness of some potential nectar sources, for example, are not). These models, however, explain relatively little of the variation in TH observations, which we interpret in light of TH presence throughout the study area. In addition to observational studies, we were successful during the 2011 field season in carrying out experiments with TH larvae: 86 larvae were exposed to Tecate cypress foliage collected from trees that were either young, of medium age, or relatively old. Contrary to previous reports involving TH, but consistent with other work in the genus Mitoura, younger foliage was a superior larval resource. Future work would be needed to draw inferences regarding consequences for adult fitness in the wild. In summary, most tasks have been completed, and most objectives have been met for this project, including the experiment with caterpillars, which was previously uncertain given the sporadic availability of females.
In 2003 and 2007, southern California experienced several large fires which
burned thousands of hectares of wildlife habitats and conserved lands. In order to
investigate the effects of the fires on plant communities, we compared the results from
vegetation sampling conducted prior to the fires to results from four consecutive years of
post-fire sampling among 38 burned and 17 unburned plots. The sampling plots were
spread over four vegetation types (chaparral, coastal sage scrub, woodland/riparian, and
grassland) and four open space areas within San Diego County. Our survey results
indicated that burned plots of chaparral and coastal sage scrub lost shrub and tree canopy
cover after the fires and displayed shifts in overall community structure. Post-fire
community structure within burned chaparral and coastal sage scrub plots was more
similar to that found in grasslands. We did not find differences in species richness or
community composition in grasslands or woodland/riparian vegetation where shrub and
tree cover did not significantly change after the fires. Across all plots both before and
after the fires, non-native grass was the most abundant “species”, followed by chamise
(Adenostoma fasciculatum) which was consistently the second most abundant species.
We saw increases in the cover rates for several species, including peak rush-rose
(Helianthemum scoparium) and Ceanothus spp., in burned chaparral and coastal sage
scrub plots. California sagebrush (Artemisia californica) and California buckwheat
(Eriogonum fasciculatum) appear to have declined drastically in our coastal sage scrub
samples with little to no signs of recovering. Chamise, Tecate cypress (Cupressus
forbesii), and pines (Pinus spp.) also declined, but it apprears that there has been some
progress in the post-fire recovery of these species. We discuss these individual species
results as they relate to specific life history traits, such as susceptibility to initial mortality
and post-fire changes in habitat suitability. We foresee that a continued unnatural fire
regime for southern California will result in a simplification of the southern California
vegetation communities, especially in the shrublands.
This report covers activities performed during our second year of work with Thorne's hairstreak (TH). Activities are summarized with reference to objectives as outlined in our first annual report, and activities for 2011 are projected (field activities for these two central years of the project are very similar). Over the course of 130 field days in 2010, vegetation sampling and butterfly monitoring were carried out as planned. Vegetation was characterized in 249 plots associated with 38 Tecate cypress stands. Butterfly surveys were conducted in 136 plots associated with 33 cypress stands, and juvenile (caterpillar) surveys were conducted in 67 plots in 26 cypress stands. Of those plots surveyed, adult butterflies were seen in 26 plots (18 stands), and caterpillars were found in 5 plots (3 stands). In total, 50 adults were observed and 5 caterpillars were found in the field in 2010. We have also conducted a trial run of habitat modeling analyses, to verify the suitability of our data for the goals of the project. In summary, objectives for 2010 were met, with the primary exception of manipulative experiments for which we were limited by the availability of females in the field, which is unpredictable.