❮ Projects page Pennsylvania Horticultural Society

Spatial Analysis Project:

The Pennsylvania Horticultural Society works closely with partners from TreeVitalize, a state program launched by the Pennsylvania Department of Conservation and Natural Resources, and the Philadelphia Department of Parks and Recreation, to plant trees in urban areas. Through the PHS Tree Tenders® bare root tree planting program, thousands of bare root trees have been planted in Philadelphia by community volunteers in the fall and spring seasons since 2004. Bare root tree stock is used because the same caliper tree weighs less than balled and burlap trees with the same caliper trunk, and have a larger intact root system. Bare root trees are also less costly since they don’t require difficult transport and installation with heavy machinery.

With an intensified planting effort across the city, an important factor to consider is the care of those trees. Trees planted in urban areas face many stresses that impact their longevity. Trees planted by Tree Tenders are thought to have a high survival rate, as dedicated and trained volunteers remain focused on their care, reducing the cost of maintenance. However, urban tree mortality is a topic that requires further research that can help urban foresters to better focus their plantings and maintenance efforts.

This study first seeks to determine the tree mortality of bare root trees, and secondly to determine factors that affect mortality by comparing communities with more active tree stewards to less active groups. Finally, this study seeks to determine projections of canopy cover over time given mortality and planting rates. This information should then inform an opportunity map of priority areas where trees can be planted. Variables to consider for planting restrictions include existing infrastructure, casted shadows, tree planting regulations, and planting potential based on landuse/cover type.

Data available:

Through the PHS Tree Checkers programs, Tree Tenders are requested to survey trees they have planted in their communities in the past two seasons, and provide to homeowners a “tree report card” including a checklist informing them of the current condition of the tree with recommendations for tree care. The report card results are relayed back to PHS. Our assumption is that participating in the Tree Checker program denotes a more engaged and proactive Tree Tender’s group. Not all groups participate; PHS is interested in comparing mortality of trees within active Tree Tender areas to those within areas that have less active groups that do not participate in the Tree Checkers program.

Two sets of Tree Checkers data collected from the summer of 2011 & 2012 is available for review, representing four seasons of plantings. The data includes the planting address, tree condition, trunk caliper, species, and planting season. PHS Plant One Million team is currently conducting Tree Checkers in neighborhoods that had not submitted data themselves. Additional PHS datasets include:

• PHS Tree Tenders group boundary shapefile
• Datasheets on the bareroot tree distribution for each season, including participating groups, the number of volunteer, tree species and the number of trees planted.
• City of Philadelphia datasets of infrastructure, land-use and land cover are available on Pennsylvania Spatial Data Access (PASDA) website, and through the Philadelphia Office of Innovation and Technology.

Maps and Reports that will be created:

A final report that summarizes the results with statistics and maps displaying spatial patterns including:

• Bare root tree mortality rate and distribution of all groups submitting Tree Checkers
• Bare root tree mortality rate and distribution of groups that have planted trees but did not participate in Tree Checkers
• Other identified patterns of mortality/survivability
• Mortality rate factors including tree species and planting locations
• Projections of canopy cover over time based on mortality
• Projected planting rate based on mortality and canopy cover goals
• A planting opportunity map

How the maps and reports will be used:

The findings will be used by urban forestry stake holders in Philadelphia. PHS urban foresters will make more informed planting decisions using these results. In addition, the results will be shared with the Philadelphia Parks and Recreation team who will explore the use of bare root trees for their plantings. The United States Forest Service Philadelphia Field Station will review and incorporate this study into their ongoing research on urban tree mortality. In the future, PHS and its partners can use the priority areas in urban forestry planning, and as supporting material for grant proposals. Finally, compelling maps will be posted on the PHS Plant One Million website at plantonemillion.org.