CASE STUDY:
SAN FRANCISCO BOTANICAL GARDEN
The San Francisco Botanical Garden is a living museum within Golden Gate Park. This 55-acre horticultural refuge showcases over 8,000 different kinds of plants from around the world under an impressive canopy of pine, cypress, and gum trees.
While on a walk through the garden, a patron recognized the potential risks the maturing trees posed to visitors. Many of these giants contained large dead limbs or other structural defects, which predisposed the trees to branch, stem, or root failure. Bartlett Tree Experts was called in to help remediate the probability of personal injury due to failing trees and make recommendations for maintaining the safety, health, and structure of the mature tree canopy
During our initial exploration, our San Francisco-based Arborist Representatives discovered that hundreds of person-hours of work would be needed to complete all the required tree pruning, support system installation, and removals. To properly plan, organize, and prioritize the work, we began the process of conducting our GIS-based tree maintenance inventory.
We partnered with garden personnel to define the goals and objectives of an arboretum inventory. Our focus was on all trees 18 inches and larger in diameter at 4.5 feet above ground level, or any tree that showed visual evidence of potential failure. Using ArborVue, arboriculturally-focused GIS software built with ArcPad and ArcGIS Engine, not only would tree attribute information be recorded, e.g., tree species, diameter, health, but so too would recommendations for improving tree stand health and structure, e.g., pruning, structural support system installation, or tree removal.
Additionally, recommendations for further tree evaluation were made for instances where it was difficult to tell from the ground whether a defect in a branch or stem warranted abatement treatment.
GIS support specialists/International Society of Arboriculture (ISA)-certified Arborists from Bartlett's laboratories teamed up with the local Bartlett representative to form the two inventory teams that would complete the job. Using ArcView, the GIS specialists overlaid a CAD drawing of the garden on digital content obtained from GlobeExplorer Inc., an Esri Business Partner. Using the newly created map, the garden area was equally divided among the teams, each of which carried a Trimble Geo 2005 series GPS data recorder with a Trimble GeoBeacon to capture all the tree attributes and maintenance recommendations.
After a week of exploring the garden's large trees, data collection was completed. In total, the teams captured attributes for 710 trees in the inventory. Although the majority of the trees were Monterey pine (Pinus radiata), Monterey cypress (Cupressus macrocarpa), and blue gum (Eucalyptus globulus), the teams recorded a total of 132 different tree species. It was determined that 140 trees (19 percent) needed to be removed because they posed potential hazards or were in advanced stages of decline. Additionally, 513 trees (73 percent) needed to be pruned for safety, health, structure, or appearance. Another 47 trees (6 percent) needed tree support systems installed or inspected to reduce branch and crown failure potential. To assess sound wood strength, 33 trees (4 percent) required further quantitative tree structure evaluation. Tree diseases, like pine pitch canker; pests, like stem-boring beetles; and soil conditions were also recorded during data collection to help manage the trees in the garden.
With field data collection completed, a management plan was developed with work type recommendations grouped together and prioritized. The GIS specialists generated maps to illustrate where trees were located, along with the associated recommendations. Further queries were developed and illustrated on maps to show daily work and progress. As with most large facilities, there were numerous other projects going on at the same time as the tree work. Using the GIS developed for the garden, tree work could be re-prioritized around other projects taking place in the garden. Additionally, garden staff made all tree inventory information and maps available to the general public, and 30-day removal notices were posted to diffuse any public concern.
To date, most of the high-priority trees and areas of the San Francisco Botanical Garden have had the recommended work completed. Thirty trees, from 15-foot stumps to 200-foot trees, have been removed, and 150 trees have been pruned or had structural support systems installed.
It is worth mentioning that not long after high-priority tree pruning and removals were completed, a severe storm hit the city. Many trees in the region were felled or badly damaged. Throughout the 55-acre San Francisco Botanical Garden, only five trees were lost or damaged, and these trees were in low-priority areas of the garden. Garden officials credit the work prescribed and carried out through Bartlett's GIS model of the management plan as the reason there was so little damage to the garden compared to the rest of Golden Gate Park.