Sponsored by California State Parks, Colorado Desert District, 2004-2009 (overseen by Kim Marsden, Assoc. Resource Ecologist)
We examined establishment patterns of pines following a large, severe wildfire in the Peninsular Ranges of southern California, USA. The October 2003 Cedar Fire caused 98% pine mortality. In this study, we asked (i) where did seedlings establish and survive in formerly forested areas of the Cuyamaca Mountains 5 years following the high severity fire and (ii) what factors were associated with the spatial pattern of seedling establishment? Factors analyzed were pre-fire vegetation type, fire severity, post-fire vegetation characteristics, topography (slope, aspect, and elevation), and mapped soil type. We used a unique belt-transect survey method following the existing trail network that resulted in a representative sample of post-fire environments. Almost 1300 100 m × 20 m quadrats were searched in 2008–2009, one third of which supported juvenile pines. Regeneration primarily consisted of Coulter pine (Pinus coulteri D. Don), a weakly serotinous pine that was establishing at densities of 5–2320/ha on half of the quadrats where it had occurred pre-fire. Pinus coulteri regenerated in areas burned at high severity where pre-fire pine cover was high and its abundance was positively associated with higher elevation and cover of bare soil. In contrast, minimal regeneration of nonserotinous pines occurred patchily in areas that were not severely burned.
Post-Cedar Fire Mixed Conifer-Hardwood Monitoring (2007) -- Executive Summary – Findings and Recommendations
The 2003 Cedar Fire burned extensive forested areas of the Cuyamaca Mountains in the Peninsula Ranges of San Diego County, CA, USA. This large fire severely affected these forests. The purpose of this study was to examine the effect of the heterogeneity of both the landscape and disturbance on patterns of post-fire vegetation dynamics. An earlier project (Agreement C0443021) reported that conifer mortality in Cuyamaca Rancho State Park (CRSP) was extremely high and positively related to fire severity, and that early post-fire vegetation dynamics during the first two growing seasons were dominated by the establishment of abundant and diverse native herbs (including fire-obligates) as well as shrub seedlings, and resprouting by shrubs and oak trees. This study reports on the analysis of data from 38 vegetation monitoring plots in West and East Mesas resurveyed in May-June 2007, the fourth post-fire growing season. Vegetation changes in the first four years following a large, severe crown fire in Coulter pine and mixed conifer forests are described.
Dense shrub cover, primarily Ceanothus palmeri, has established on about 40% of the area surveyed, especially in stands with higher former forest cover and fire severity. About half of these stands had lower shrub cover, averaging 32%, and half had high cover, averaging 70%. On a landscape scale I recommend no vegetation management of C. palmeri dominated stands. Ceanothus is a nitrogen fixing genus of California shrubs that serves an important ecosystem function, especially following fire on low-nutrient soils in California’s montane forests. These shrub stands will naturally thin over time, resulting in lower, patchier cover, and allowing establishment of conifers.
Site-specific removal of shrubs over small areas may be required for tree planting projects, but the disadvantage of Ceanothus removal, again, is that it may affect the availability of nutrients for successful tree establishment. Ceanothus is also known to be an intermediate host for mycorrhyzal fungi associated with conifer species and necessary for their survival. In the stands examined that fell at lower elevations in the forested zone (1300-1400 m), shrub cover averaged around 60% and chaparral species dominated vegetation recovery, especially Ceanothus leucodermis. Again, Ceanothus plays an important nutrient cycling role post-fire in California ecosystems. These sites appear to be following a normal trajectory of succession for chaparral-dominated sites. There is no indication that vegetation management is required.
By 2007, 4 years after the Cedar Fire, exotic annual brome grasses (Bromus spp.) and a mustard, Sisymbrium altissimum, were the most abundant herbaceous species in the areas surveyed. Forested areas of CRSP are interspersed with dry meadows (grasslands) with a history of grazing, and the most abundant brome species have been established there for at least a
Post-Cedar Fire Mixed Conifer-Hardwood Monitoring (2004-2006) -- Executive Summary – Findings and Recommendations
In late October 2003 the Cedar Fire, the largest wildfire in southern California in over 100 years, burned almost all of Cuyamaca Rancho State Park (CRSP; 10,000 ha) at high severity. CRSP, situated in the Peninsular Ranges, harbors one of southern California’s unique sky islands of montane conifer habitat surrounded y a sea of foothills shrublands (chaparral). The landscape looked like scorched earth to anyone who drove through CRSP after the fire. However, many ecosystems in California are fire adapted – their plants have traits that allow them to survive or regenerate after fire, or even that require fire for regeneration.
The purpose of this study was to measure thee effect of the Cedar Fire on the forested lands of Cuyamaca, and to monitor the early recovery of the plant community. We selected the West Mesa area of the Park (about 1100 ha) for study because a previous forest survey was conducted there 11 years before the Cedar Fire, and because it appeared to be less completely burned than other areas (Middle Peak). This selection was ironic for two reasons. First, the previous survey did not locate all sample plots precisely enough that they could be relocated exactly. Therefore, before and after comparisons of forest structure can only be made at an aggregated level. Secondly, we determined that in fact fire severity for all but five of the 37 plots revisited was very high. While this in itself is useful information, it limited our ability to determine the effect of fire severity on forest recovery.
However, we found the following in the first post-fire year (2004):
The 2003-04 rain year was extremely dry, followed by the extremely wet year of 2004-05. Continued monitoring in 2005 revealed the following:
Finally, to paraphrase Professor Paul Zedler, is may be fruitless to debate the natural fire cycle in this region when climate and human use of fire have varied at the time scale of the fire regime itself – hundreds to 10,000 years. Instead, as Wheeler in his book on fire ecology remarked, resource managers must determine what elements of biodiversity, ecosystem function or resource production they want to manage with fire, and then determine how, when and where to use fire (prescription, suppression, let-burn) to achieve their resource management goals.
Publications (also see Publications)
Franklin, J. and Bergman, E., 2011. Patterns of pine regeneration following a large, severe wildfire in the mountains of southern California. Canadian Journal of Forest Research 41(4):810-821 10.1139/x11-024.
Franklin, J., 2010, Vegetation dynamics and exotic plant invasion following high severity crown fire in a southern California conifer forest, Plant Ecology 207:281-295. DOI 10.1007/s11258-009-9672-6.
Bergman, Erin, 2009. Pine regeneration in Cuyamaca Rancho State Park, San Diego County, five years after a high severity crown fire, Thesis (M.S.)-- San Diego State University (Biology)
Schmalbach, H., J. Franklin and J. F. O’Leary, 2007, Patterns of post-fire regeneration in a southern California mixed chaparral community, Madroño 54(1): 1-12
Franklin, J., Spears-Lebrun, L., D. Deutschman, and K. Marsden, 2006, Impact of a high-intensity fire on mixed evergreen and mixed conifer forests in the Peninsular Ranges of southern California, USA, Forest Ecology and Management 235: 18-29.
Spears, Linnea Anne, 2005, Tree mortality and forest recovery in Cuyamaca Rancho State Park, San Diego County, California following the 2003 Cedar Fire, Thesis (M.S.)-- San Diego State University (Biology), 45 p.8.
Schmalbach, Heather, 2005, Patterns of post-fire regeneration in the chaparral community at Sky Oaks Field Station, Thesis (M.S.)-- San Diego State University (Biology)