Santa Ana Mountains Tecate Cypress (Cupressus Forbesii) Management Plan
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Final Santa Ana Mountains Tecate Cypress (Cupressus forbesii) Management Plan Prepared by: Susana Rodriguez-Buritica & Katharine Suding University of California, Berkeley Department of Environmental Sciences, Policy, and Management Berkeley, CA 94720 & Kristine Preston Nature Reserve of Orange County 15600 Sand Canyon Avenue Irvine, CA 92618 Prepared for: California Department of Fish and Game 4949 Viewridge Avenue San Diego, CA 92123 Contract # P0750005 01 & Nature Reserve of Orange County May 17, 2010 Santa Ana Mountains Tecate Cypress Management Plan EXECUTIVE SUMMARY Orange County’s Central and Coastal Natural Community Conservation Plan/Habitat Conservation Plan (NCCP/HCP) was established in 1996 to conserve sensitive plant and animal species on approximately 37,000 acres. Tecate cypress (Cupressus forbesii) is a rare endemic species restricted to several locations in southern California and northern Baja California. The northern most population of Tecate cypress occurs in the Santa Ana Mountains within the NCCP/HCP Central Reserve and receives regulatory coverage under the Plan. This population is threatened by too frequent wildfire. The Nature Reserve of Orange County (NROC) oversees monitoring and management of species within the NCCP/HCP and formed the Tecate Cypress Management Committee (TCMC) to develop a management plan for this species. The committee is composed of land owners, land managers and regulatory agencies with an interest in conserving Tecate cypress in the NCCP/HCP. This management plan was developed by NROC based upon the work of researchers from UC Berkeley and input from the TCMC. The objectives of this management plan included determining the current distribution and demographic structure of the Santa Ana Mountains Tecate cypress population and using this data in ecological models to assess threats to persistence and to identify restoration sites for enhancing the population. The management plan includes a thorough review of Tecate cypresss and related species with information relevant to management. The plan documents changes in the historic extent of this species in the Santa Ana Mountains relative to fire history. Field studies conducted in spring 2009 delineated the current distribution, abundance and demographic structure of the population. Demographic models were then constructed to characterize population dynamics and to identify minimum conditions for persistence. The demographic models were linked to a model identifying spatial variation in fire risk and sensitivity analyses were conducted to predict population trajectories with different fire frequencies. Habitat modeling was employed to assess environmental relationships and identify candidate sites for restoration to enhance the current population. Knowledge gaps were identified and research priorities developed. Based upon the the current population status and ecological modeling results, montoring and management actions were formulated. Finally, a cooperative interagency management agreement was drafted to facilitate future monitoring and management activities. Tecate cypress is adapted to a fire regime with fire return intervals of 30-40 years, a period sufficient for individuals within a stand to develop cones to ensure replacement. There have been six large fires affecting the population over the last 95 years. Based on 2009 surveys, it is estimated that the current poplation is distributed over 200 ha and consists of approximately 3,800 adult and 200 juvenile trees and thousands of seedlings. There is substantial variation in population structure, with fragmented and isolated refugia supporting reproductive adults in ravines and slopes and patchy areas of high seedling density interspersed with patches exhibiting little or no post-fire recovery. Many refugia with cone-bearing trees are located at the lower edge of the distribution where the probability of upslope recruitment is low. Over the last 20 years wildfires have significantly reduced the effective population size but have not significantly contracted the extent of the distribution. The structure of the current population is shaped by fire history, post-fire drought, site-specific habitat characteristics, and pre-fire stand age structure and density. The majority of the current population is composed of seedlings that will not reach maximum seed production for many years, putting the population at risk if there is a large wildfire in the stands during the next 20 to 30 years. 1 Santa Ana Mountains Tecate Cypress Management Plan An assessment of fire risk indicates that areas where Tecate cypress currently occurs have similarly high burn susceptibilities. Field surveys identified isolated refugia associated with steep slopes and ravines. A size-based environmentally stochastic model identified key features of the Tecate cypress population affecting persistence. Current levels of cone and seed production would be adequate for self replacement (i.e., one seedling per reproductive adult every two years) if the population were connected and if recruitment occurred independently of fire events. However, the population is fragmented and there is little known about year-to-year recruitment in the absence of fire. When fire stochasticity is included in the model, Tecate cypress population growth declines under fire regimes with fire return intervals of less than 35 years. This indicates fire should be kept out of the stands for at least the next 30 years allowing individuals to achieve reproductive maturity and supply sufficient seed for replacement following the next fire event. MaxEnt models were constructed to predict suitable habitat for adult and seedling Tecate cypress in the Santa Ana Mountains. The models predicted low habitat suitability for most of the study area outside the current range of Tecate cypress. Potential areas for establishment of Tecate cypress seedlings include north slopes at intermediate elevations with mild average annual temperatures (<13.5ºC), moderate precipitation (92-133 mm during the growing season), shallow soils (restrictive layers < 14 cm), a high percentage of sand (>50%), and low vegetation cover (<40%). Because the different variables incorporated within the models vary in resolution, it is recommended that predictions from single variable models also be assessed in selecting potential restoration sites. The habitat models are based upon an aggregated distribution of locations representing the current distribution of Tecate cypress in the Santa Ana Mountains and which are similar in environmental characteristics. If models were constructed with a broader sample of Tecate cypress locations representing the entire species range and greater variability in environmental conditions, it is likely that suitable habitat predictions would be less restrictive. It is unknown whether the current restricted distribution is due to environmental filters at the seedling establishment phase reflecting a true restriction to a particular area or is a result of low dispersal. Potential factors affecting seedling establishment and survival include soil characteristics, precipitation and soil moisture, and competition with shrubs. It is recommended that habitat modeling based upon the entire extent of the species distribution and experimental planting trials be implemented to further understand limiting environmental conditions for seedling establishment and survival. Priority areas for restoration were identified based upon seedling habitat suitability predictions combined with an analysis of fire risk during Santa Ana wind conditions. The major threat to the Tecate cypress population in the Santa Ana Mountains is frequent, large wildfires. Other potential threats include drought, changing climate, air pollution, invasive plants, and human disturbance. The single most important thing that land managers can do to ensure the continued persistence of Tecate cypress is to reduce fire frequency. A number of strategic and tactical management recommendations were formulated to prevent and control fires. These include having the TCMC work with transportation agencies to implement fire-hardening measures (e.g., k- rails, concrete walls and hardscaping) along Highway 91, the 241 Toll Road and other major roadways adjacent to NCCP/HCP lands in the northern Central Reserve. The committee should also work with utility companies to reduce the risk of powerline ignited fires near the Tecate cypress population. The TCMC should coordinate with the Orange County Fire Authority to ensure fire roads are maintained to standards that allow access to the population during fire events. To coordinate management activities, the TCMC should meet annually with fire agencies to assess fire risk and preparedness and make recommendations for annual management activities. The committee should work with the owners of the proposed housing development at the base of Gypsum Canyon 2 Santa Ana Mountains Tecate Cypress Management Plan and the Anaheim Fire Department to develop fire prevention strategies. The TCMC should also coordinate with Orange County Fire Authority and Fire Watch patrols to prepare for red flag events and develop a public outreach program to educate people on fire prevention in the northern Santa Ana Mountains. There are a number of actions that land managers can take to reduce fires in the the northern Santa Ana Mountains. These include prohibiting prescribed fires within the Tecate cypress population, controlling invasive weeds near roads and ignition hot spots, restoring