Title

An Examination of the Urban Forest, Roseville, CA

Author

Keith Torsen American River College Geography 350: Data Acquisition in GIS, Fall 2023

Abstract

The City of Roseville has invested heavily in time, money, and staffing to ensure the survival and health of their urban forest. A rule of thumb that has caught on in recent years is the “30/20/10 rule”, where you cap off inclusion levels at the respective maximums. As a general rule, an urban forest should not have more than 10% of any species, 20% of any genus, or 30% of any family, as a percentage of overall population, for a variety of reasons. How well does the City of Roseville urban forest hold up to this guideline? This project sought to find out.

Introduction

Analyzing the urban forest takes time, effort, and a lot of boots on the ground. Luckily, the City of Roseville has done this, and some information is ready to go in their Urban Forest Master Plan. Using this document as a guide and a reference for what the Roseville’s street trees looked like in 2013, along with data from 2018 and 2023, we will explore the urban forest through an analytical and a mildly historic lens. All data from 2023 will be limited, but will also be firsthand. How well does the City of Roseville follow the guidelines laid out in the “30/20/10 rule”? 2013 shows a strong start throughout the city. The Davey Resource Group shows in this chart the overall tree canopy cover for the City of Roseville.

And here is a breakdown of tree species that they found in their initial survey:

Background

I currently work for a private contractor providing tree care services to the City of Roseville. I am the foreman for the tree technician crew. We are the ones getting our hands dirty and performing the prescribed work to the trees. Those prescriptions are based in large part on sections of the Master Plan we are starting with. Part of my job is to help manage Roseville’s tree inventory. Through daily inspections of trees that we work on to one-off tree inventory projects, my employer is directly involved in maintaining and managing information for the City of Roseville’s urban forest. Information collected from myself, and along every rung of the corporate ladder, is used as a guiding tool in decision-making for the City. This project would hit a lot closer to home if I lived in Roseville, but spending 10 hours a day with trees that they own is similar to that. And Citrus Heights is a nearby town, so it’s close enough. The data collected in 2023 will be from my own paperwork. No sensitive information will be given out, and any charts or other information lifted from the Roseville Master Plan is public information, and accredited properly to the City of Roseville and Davey Resource Group.

Methods

The City of Roseville’s “Urban Forest Master Plan” has some documentation on the methods of Davey Resource Group, who initially gathered the data for the City in 2013. More recently, “EarthDefine” completed an urban canopy assessment based on NAIP data in 2018, which we can use for comparison. I downloaded a shapefile of the Neighborhood Association names, brought that into ArcGIS Pro, and manipulated the symbology and labeling to provide Reference Figure 1. This is a stylized map of the neighborhoods in Roseville.

Through my daily job duties, I help update Roseville’s tree inventory as my crew completes prescribed work around the city. To gather basic data from 2023 for comparison to 2013, I have sampled my own work documents. Samples are taken from August 2023 to December 2023, and for simplicity and brevity, I will only be using the common name of tree species. Any differences from Davey’s initial findings in the 2013 report will be noted. To prepare the comparison data, I took my work documents, uploaded and processed them via tools provided by CamScanner, then used tools in Excel such as “Filter” to filter out the common names of each sample date. From there, having individual species names for every tree on every single sample date allowed me to use the “Analyze Data” tool in Excel to provide the breakdowns and figures for the Results. The documents sampled ranges from August 31st, 2023 through December 18th, 2023. The documents are also limited to working days that I completed the daily inventory parallel to work performed. Between the dates mentioned, there must be a minimum of 10 working days that I was not responsible for inventory management and paperwork. Three weaknesses arise here: The sample size for the documents is incomplete and some dates will inevitably be missing My only goal with the sampling was to pick out an average of one document per week. This, in theory, should give a fair spread of tree species and locations worked throughout the City of Roseville. My work these past few months is not a proper representation of the districts of Roseville. Considerations made for my work days included funding, urgency, weather, internal and external personnel conflicts, City schedules, and other factors, known and unknown. Thus, these results are limited in time, scope, and depth. This is intended to be an ongoing personal project. If we take a look at the following map, we can see that the north west side of Roseville is lacking in tree canopy cover. This image is taken from NAIP 2018 data, credited to the United States Forest Service. Current planting projects are still under way for this section. Data from my own data pool is severely limited for that section of the city.

If we take a look at the following map, we can see that the northwest side of Roseville is lacking in tree canopy cover. This image is taken from NAIP 2018 data, credited to the United States Forest Service. Current planting projects are still underway for this section. Data from my own data pool is severely limited for that section of the city.

Results

What results can we draw from the heavily filtered and selected sample? For one thing, it’s pretty clear that the City of Roseville is keeping within its goal of the “30/20/10 rule”. The bar chart on the left is directly lifted from the Roseville Urban Forest Master Plan data from 2013. The donut chart on the right is my data from August through December 2023. I could not get a bar chart, so I apologize for the apples-to-oranges charts comparison. Davey Resource Group also had orders of magnitude more data points than I currently have, despite working with over 1,000 individual data points for this project alone.

Let’s break it down a little bit: The top five species, by common name, are Ornamental pear (8.36%), Crepe myrtle (7.79%), London planetree (7.6%), Red maple (6.74%), and Sour gum (6.36%) in 2023. Contrast this with 2013 full data, and we already see a reduction in London planetree, but an increase in other species. Zooming out to the top ten, “Vacant Site” came in at 4.84%. This percentage of my sampled data is a site the City deems suitable for a tree to be planted. It is “vacant,” and could use a tree. This had to be filtered out of the top results as “Vacant Site” is not a tree species. Overall, another ~50% or so of the sampled trees were “Other Species,” not already listed. Small, but worth noting is 1.71% and 0.54% respectively of my full data pool were “Unsuitable Site” and “Stump”. And “unsuitable site” would otherwise be a planting site, but is limited in some way in reality. Anecdotally, this is most commonly due to conflicts with utilities. “Stump” code refers to a tree of any species that has been removed, but the stump remains. These are not significant numbers, but have been removed from the estimated percentage making up “Other,” trees of another species. Stumps have their own policies and programs surrounding them. What about a full breakdown, though? What else can we see? Below is a full table of the tree species. At this level, another error is “typos” from the pdf-to-Excel workbook extraction process. This will be accounted for in the future, but is noted here for now. ‘Common’ denotes tree species based on common name.

This table is also prone to typos, thus resulting in slightly tainted results. Cleaning up the data initially would have gone a long way towards accuracy. Processing and analysis of the data also provided some opportunity for editing, but the sheer number of values worked with made it impractical. The data also shows that there is room for improvement. What would happen to the data if I added all of my inventory, not just random sampling? How would that affect the distribution? This project is worthy of continuation and polishing up.

Conclusion:

The City of Roseville is on it’s way to adhering to the “30/20/10 rule,” the goal it established 10 years ago. It’s a strange coincidence that I’m coming in at the tail end of the 10 year mark, but from the small sample size that I used for this project, it seems very likely that Roseville can achieve its goal within a few more years. I am proud to be a part of data inventory collection and management at such an intimate level. Bringing more data into the model, correcting for typos, errors, and stray symbols would go far to help this become a professional project that may serve as the foundation of an updated document for Roseville, simply as a documentation tool. Over 1,000 data points were loaded into Microsoft Excel, so adding the missing points from the other days that were not sampled would also increase range, species diversity, and geographic locations of the trees in relation to the City of Roseville. They have done a decent job at maintaining progress in reaching the goals they outlined over a decade ago.

References

Documents and Websites ROSEVILLE URBAN FOREST MASTER PLAN https://cdnsm5-hosted.civiclive.com/UserFiles/Servers/Server_7964838/File/Government/Departments/Parks%20&%20Recreation/About%20Us/Reports%20and%20Plans/UFMP%20Final%209-15-2014_web.pdf Frank S. Santamour, Jr https://agroforestry.org/the-overstory/144-overstory-126-trees-for-urban-planting-diversity-uniformity-and-common-sense Dave Kendal, Cynnamon Dobbs, Virginia I. Lohr https://www.sciencedirect.com/science/article/abs/pii/S1618866714000387#:~:text=A%20commonly%20used%20rule%20of,evidence%20to%20support%20these%20numbers. Web layers used for screen captures: Percent canopy cover 2018 https://www.arcgis.com/home/item.html?id=1b564fdece4c4108a70f039ff661f2c7 Urban canopy 2018 https://www.arcgis.com/home/item.html?id=cbd42220c46340259858e8f34f7aae03 City of Roseville Neighborhood Associations https://data-roseville.opendata.arcgis.com/datasets/c056077a6f714f688ee7b635389c0822_23/explore?location=38.751300%2C-121.330856%2C12.64 Tree inventory August 2023 through December 2023 credited to West Coast Arborists, Inc. and the City of Roseville. Data through these dates were collected while performing regular job duties related to the position of “Foreman” at West Coast Arborists, Inc. This is first-hand data, and has been reduced to tree species' common name for simplicity and brevity.