Barbara A. Holzman, PhD

Isolation of Natural Areas in San Francisco due to Urban Development: Effects on Native Species.
Barbara A. Holzman, Department of Geography, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132.  E-mail: bholzman@sfsu.edu.

San Francisco’s Significant Natural areas are small, fragmented remnants of what once was a diverse community of native plants and animals that dominated the landscape.  These areas are all that is left of the diverse biogeography of San Francisco.  The scattered presence of these Natural Areas provides an opportunity to investigate the consequences of fragmentation and urban encroachment on native plant and animal populations. The first step in this investigation is to piece together the land use and development histories of these areas. This paper discusses how and when urbanization has isolated these precious and unique landscapes through a series of maps, historical art,  photos and text.  From Native Californians to Spanish Missionaries to Gold Miners, Post WWII immigrant and the more recent high tech invasion, each has left their imprint on the land.  The once continuous native landscape became divided, subdivided, scraped, bulldozed and vegetated with exotic species, leaving only a few native fragments we call Natural Areas remaining.  These areas are effectively isolated from other nearby natural remnants, creating urban islands of native landscape in a sea of residential development.  A preliminary analysis of species numbers in association with area, length of isolation, amount of edge and other biogeographic variables is discussed. 

Pinus muricata Regeneration Study Point Reyes National Seashore: 
Barbara A. Holzman, Ph.D., Karen Folger, graduate researcher.

            The Bishop Pine Forest Community at Point Reyes was examined to assess the impact of the 1995 Mt. Vision Fire on the  regeneration of the  plant community with particular emphasis on Bishop Pine.  The study sites were surveyed in the summer of 1996 and 1997.   Thirty two transects were surveyed along Inverness Ridge and Bay View Trail. Along with the environmental variables, such as slope, aspect and location; vegetation species composition, frequency and seedling counts were recorded for each transect.   The most significant result so far was the abundance of Bishop pine seedlings found throughout the transects.  On average, 26 seedlings per square meter were recorded within the burned Bishop Pine Community.    June 1997 surveying found that the seedlings on most sites appeared to be healthy and growing, with some as tall as 1.2 meters.   There were few new (this year) seedlings noted.    There was some seedling mortality under large shrubs of ceanothus (Ceanothus thyrsiflorus) and lupine (Lupinus arboreus) and fireweed (Erechtites minima) .  Although very little fireweed was observed in the study area during the first year’s sampling, this year’s sampling  noted the presence of fireweed on at least 50% of the sites.  There appeared to be little predation of seedlings as was originally feared.
            Twenty months have passed since the Point Reyes fire of October 1995 and the Bishop pines have reproduced at an amazing rate.   Associated scrub vegetation typically occurring in association with Bishop pines have also been successful at resprouting and reestablishing. The lupine in some areas is over 5 feet tall.  Huckleberries (Vaccinium ovatum),   ceonothus and coffeeberry (Rhamnus californica) have resprouted vigorously.  Their dominance as understory cover may lead to a further loss of seedlings in the understory.  The  occurrence of exotic invasives (such as fireweed) although minimal on the study site the first year, is beginning to play a significant role this year.  Long term monitoring will yield abundant information on Bishop pine seedling survival, competition among associated species, as well as the role of fireweed and it’s importance in this most fascinating plant community.