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APPENDIX I - BIOLOGICAL RESOURCES A high probability exists that many trees on the project site whose root zone (as denoted by the crown circumference)is located adjacent to grading activities would experience surface soil compaction during the construction process. In the areas that have been prematurely cleared for fairway construction,this impact may have already taken place. Soil compaction greatly decreases the oxygen availability in the root zone area which can lead to the weakening and eventual death of a tree. Although the applicant's Management Plan states that there will be a tree protection zone one and one- half times the diameter of the tree canopy,the plan does not describe how this will be enforced to prevent soil compaction and other disturbances Another latent cause of tree death would result from the positioning of lawn and garden watering systems upslope and adjacent to native oak species. Wet summer root soil promotes oak root fungus(Armillaria mellea), the main cause of death of oak trees in California. Additionally, unwarranted or incorrect pruning of heritage trees would reduce their vigor and visual value. Mitigation Measures 4.7-3(a) Incorporate protective measures for mature native trees into grading and development plans. These should include those outlined in the Buckeye Ranch Management Plan (August, 1991). Additionally, measures should include the enclosure of each native tree within and adjacent to the construction zone with a temporary fence situated four feet outside the edge of the leaf canopy to prevent root zone soil compaction and limb/trunk damagefrom grading vehicles. The Management Plan should also describe enforcement measures to ensure grading activities do not disturb root zones or compact soils. Lots and streets situated upslope from heritage trees should be designed with gutter systems which would shunt summer surface runoff water away from the root zones of native oaks. Sprinkler systems should be installed so that water is not directly applied to the root zone area of these trees. 4.7-3(b) Prohibit the cutting of all or part of any native tree unless a weakened limb or an entire tree presents a safety hazard to residents. This mitigation measure is in response to the Buckeye Ranch Management Plan recommendation that an arborist direct the pruning and culling of native oaks in the residential, golf, equestrian and service areas along the lines that might be employed in a city park. In a natural area a dead or dying tree is often as valuable to wildlife as a live one. When these do not directly pose a threat to the well being of the residents, the dead or dying tree should be allowed to complete its natural cycle. If trees must be removed,the Management Plan provision callingfor the planting of 20 seedlings for every tree must be enforced. 25