The TreePlotter Tree Management Insights provide urban foresters and planners with a high-level overview of vital information reflecting the composition and diversity of an urban forest. These metrics help make qualified, data-driven decisions to inform future planning, planting, and maintenance strategies.
Topics Covered in this Technical Guide:
- Quick Stats on your Urban Forest
- Tree Size Diversity
- Tree Species Diversity
- Benefits of a Diverse Urban Forest
- Using Tree Management Insights
Urban Forest Quick Stats
The Quick Stats section displays four helpful metrics: species richness, average DBH, tallest tree, and largest DBH.
Tree Management Insights Quick Stats
While tree diversity and species richness are correlated, they are not interchangeable terms. Species richness encompasses the total number of unique tree species, while tree diversity is more complex and focuses on the variety and abundance of tree species.
Studying and understanding the relationship between tree diversity and species richness can aid in assessing the ecological value, conservation status, and overall biodiversity of forested areas.
Tree Size Diversity in Urban Forests
This chart displays the most recently recorded diameter (diameter at breast height or DBH, measured 4.5-feet above natural grade) values along with DBH goals (as defined by Richards et al. in 1983 and 1993). This information is often used to identify a tree population’s structure, distribution of tree canopy cover and associated benefits, current maintenance needs, projecting potential surges in maintenance and removal needs, among other considerations in sustainably managing trees in communities. A distribution of tree size classes as indicated by the “Goal” uniformly distributes tree benefits and maintenance needs. Smaller, younger trees, compared to large diameter trees, aim to compensate for the loss of tree canopy cover and associated benefits that occur when large trees reach their full potential, mature, and begin to decline, requiring eventual removal (in most cases).
The size and structure of trees within an urban forest are important indicators of the age and health of the canopy. Good diversity in both the size and age of trees help to promote a healthy canopy and understanding this composition can be a valuable resource to help inform future planting and maintenance resources.
Richards, N. A. 1983. “Diversity and Stability in a Street Tree Population.” Urban Ecology 7(2):159–171.
The image above is an example of an urban forest project that shows actual tree size and age distribution compared to an ideal distribution. The ideal distribution is based on a study conducted on street trees to determine the appropriate proportions of tree sizes to ensure tree benefits are maximized while keeping maintenance and management costs at a manageable level.
As the example above shows, 58% of the public tree population (44,811 trees) is composed of trees with a DBH ranging from 1 to 11 inches. This indicates that the majority of trees are young or small-statured.
Tree Species Diversity in Urban Forests
The Tree Species Diversity charts show the top five most common tree species, genus, and family within the inventory or subset of your inventory based on data or map filters. The red horizontal lines demonstrate the 10-20-30 rule, which suggests an urban tree population should include no more than 10% of any one species, 20% of any one genus, or 30% of any family.
Tree managers, researchers, and practitioners use these parameters, first recommended by Santamour in 1990, as an industry standard to measure a tree population’s resiliency to harmful tree pests and diseases and other factors. Consider establishing these thresholds on a community-wide scale and/or at smaller-scales such as by neighborhood, street corridor, block, or project.
Tree Species Diversity Charts
10-20-30 Rule for Tree Diversity
The rule suggests an urban population should include no more than 10% of any one species, 20% of any one genus, or 30% of any family.
Benefits of a Diverse Urban Forest
Improve Wildlife Habitat
Planting a variety of tree species can help support a variety of wildlife. There are many examples that support how planting different trees can attract a wider range of wildlife species year-round. This is important since wildlife tends to have more difficulty sourcing food, water and shelter in an urban setting than they would in a natural forest.
Improve Urban Forest Resiliency
Urban trees are often faced with many stresses such as air pollutants, invasive pests, road salts, high winds and drought-like conditions. Some trees are more equipped to handle these urban stresses than others. For example, when the invasive emerald ash borer (EAB) beetle was introduced to Ontario in 2002, many ash trees were lost. In years prior, a lot of ash trees were planted as street trees, so cities faced major tree/canopy cover loss in those areas. This can be avoided in the future by diversifying the types of trees that are planted.
Support Ecosystem Services
Ecosystem services refer to the benefits that nature can provide to humans (and other living organisms). A healthy, diverse, urban ecosystem can help absorb air pollutants, promote physical and mental well-being, generate more environmental interest, improve water quality and improve soil quality. Monocultures (the planting of only one species) might be able to achieve some of these in the short-term but are not sustainable long-term. Not only does planting a wide range of species help the environment, but it can make cities more beautiful! A variety of trees means a variety of leaf shapes, canopy shapes, flowering/blooming times and fall color. 1
Using Tree Management Insights
The Tree Management Insights Metrics provides urban foresters with important information regarding the diversity of species and size of the trees within their urban forest which is essential for making decisions based upon empirical data.
Planning and Establishing Goals
In order to maximize the benefits of a Tree Inventory program, it is essential that data be collected consistently and accurately in order to establish a baseline that can be used as the foundation for creating achievable goals and developing an executable planting and maintenance strategy.
The Tree Management Insight Metrics can be an effective planning tool for Urban Foresters by helping to establish a base-line of critical data and for developing practices to achieve specific goals to improve the health of their urban forests.
As new policies and strategies are implemented, it is critical that the tree inventory data be well-maintained and monitored in order to track progress towards identified goals. As new urban forest data becomes available, urban foresters can analyze and assess progress and adapt strategies based on quantifiable information.
The Tree Management Insight Metrics are an invaluable resource for tracking metrics and goals and can be particularly effective for tracking data as plans and work cycles like planting and maintenance are implemented.
The Tree Management Insight Metrics can be an important tool for helping to disseminate information to key parties like city council members and city planners. The UFMP Dashboard can be downloaded and printed to be included in annual or quarterly reports for programs like Tree City USA as well as Budget Planning efforts.
TreePlotter Tools Involved:
- Tutorial: Advanced Filter
- Using the Advanced Filter, you can filter for Trees in a given area or with specific attributes to only include those in your Tree Management Insights analysis.
- Tutorial: Tree Management Insights
- Learn how to use this tool by clicking on the link above.