SR 06:242 - Laserfiche WebLink

Preliminary Tree Report, 3459 Foothill Rd., Pleasanton April 2, 2004 HortScience, Inc. Page 4 The Foothill site provides a view into the past. The combination of the oak woodlands along Pleasanton ridge, natural drainages that flow out of them and the grazing land below represent several eras in the history of Pleasanton's development. The distribution of species and the range of their conditions are normal. Although old and decaying trees are unsightly and can be a hazard in use areas, they provide habitat and genetic material for the next generation. Where grazing was evident there were few young trees at the time of our survey. However. the elimination of grazing and dedication of parkland will increase the recruitment of young trees and improve the sustainability of the woodland as a whole. Suitability for Preservation Before evaluating the impacts that will occur during development, it is important to consider the quality of the tree resource itself, and the potential for individual trees to function well over an extended length of time. Trees that are preserved on development sites must be carefUlly selected to make sure that they may survive development impacts, adapt to a new environment and perform well in the landscape. Our goal is to identify trees that have the potential for long-term health, structural stability and longevity. For trees growing in open fields, away from areas where people and property are present, structural defects and/or poor health presents a low risk of damage or injury if they fail. However, we must be concemed about safety in use areas. Therefore, where development encroaches into existing plantings, we must consider their structural stability as well as their potential to grow and thrive in a new environment. Evaluation of suitability for preservation considers several factors: . Tree health Healthy, vigorous trees are better able to tolerate impacts such as root injury, demolition of existing structures, changes in soil grade and moisture, and soil compaction than are non-vigorous trees. . Structural integrity Trees with significant amounts of wood decay and other structural defects that cannot be corrected are likely to fail. Such trees should not be preserved in areas where damage to people or property is likely (see Fig. 3,4). . Species response There is awide variation in the response of individual species to construction impacts and changes in the environment. In our experience, for example, California black walnuts are sensitive to construction impacts, while coast live oaks are tolerant of site disturbance. . Tree age and longevity Old trees, while having significant emotional and aesthetic appeal, have limited physiological capacity to adjust to an altered environment. Young trees are better able to generate new tissue and respond to change. Each tree was rated for suitability for preservation in use areas based upon its age, health, structural condition and ability to safely coexist within a development environment. Suitability ratings are provided for each tree (see Tree Survey, Attachments). A summary is provided in Table 2 (following page).