Understanding an urban forest’s structure, function, and value can promote management decisions that will improve environmental quality and human health. Using i-Tree Eco software and its sampling and data collection protocol, an assessment of the baseline condition, ecological function, and value of the urban forests in Scotlandville (Louisiana, USA) was conducted during 2014. A stratified (by land use type) random sample plot map of the town was generated. Data from 170 field plots located throughout Scotlandville were collected, including tree species, diameter at breast height, total tree height, height to live top, height to crown base, crown width, crown dieback, crown light exposure, percent impervious surface under the tree, and direction and distance to building. Data were then entered into i-Tree Eco v5.0 and analyzed. Modeling results indicated that there are a total of 31 species and an estimated 239.000 trees in Scotlandville with a tree canopy cover of 23.7 percent; the three most common species are Black willow (
Urban forests are integral components of land use planning because they add both ecological and economic values to local communities by improving air quality, sequestrating and storing carbon, saving energy, preventing runoff, and increasing land values (
i-Tree is a software suite created by the research scientists of the United States Department of Agriculture Forest Service and their partners (
To preserve, manage, and sustain the urban forests in Scotlandville, Louisiana (USA), an assessment of the city’s urban forests is needed to make the policy makers, city managers, and the general public aware of the ecological benefits that their city trees provide. Communicating the benefits only with intangible values would not be convincing unless these values are expressed in monetary terms. The application of i-Tree Eco in Scotlandville can better demonstrate the need for investment in the city’s urban forests.
There is no baseline information available on the structure, ecological function, and value of the urban forests in Scotlandville. Our research objectives were: (1) to assess the urban forest structure in Scotlandville; and (2) to estimate the urban forest ecosystem services and associated values. The results can be used to provide recommendations to Scotlandville’s authorities for better management of its urban forests so as to maximize the ecological benefits they provide. The study area is important because of its association with the Mississippi river, the oil refinery, and the Baton Rouge Metropolitan Airport (
Scotlandville is a community located in East Baton Rouge Parish of the state of Louisiana, USA (latitude 30.5204668 N, longitude 91.1787186 W). Situated in a temperate climate zone, its elevation is 17.70 m a.s.l. Consisting of twenty-one distinct sub-communities as identified by the Scotlandville Comprehensive Community Development Plan, and according to the US Census Bureau data, Scotlandville is divided into six different census tracts, with a combined population of 27.230 on a total of 3060.31 hectares of land.
Utilizing ESRI ArcGIS® software with the spatial analysis extension, a stratified (by land use/cover type) random sample plot map was generated (
The 2006 USGS National Land Cover Database (NLCD) data was employed for these strata. A GIS map layer representing the study area polygon(s) for Scotlandville was obtained from http://www.esri.com/data. A total of 170 circular plots were randomly plotted with 404.69 m2 per plot.
Following the i-Tree Eco data collection protocol (http://www.itreetools.org/) developed by the US Forest Service, Northern Research Station, field data were collected from the 170 plots during the leaf-on season in 2014 to properly assess tree canopies. Data collected included land use, ground and tree cover, tree species, diameter at breast height (dbh), total tree height, height to live top, height to crown base, crown width, crown dieback, crown light exposure, percent impervious surface under the tree, and direction and distance to building. Data were then entered into i-Tree Eco v5.0 for analysis.
Air pollution removal estimates were derived from calculated hourly tree-canopy resistances for ozone, sulfur dioxide, and nitrogen dioxides based on a hybrid of big-leaf and multi-layer canopy deposition models (
The air pollution removal value was calculated based on local incidence of adverse health effects and national median externality costs (
To calculate current carbon storage, biomass for each tree was calculated using equations from the literature and measured tree data (
The amount of oxygen produced was estimated from carbon sequestration based on atomic weights: net O2 release (kg yr-1) = net C sequestration (kg yr-1) × 32/12. To estimate the net carbon sequestration rate, the amount of carbon sequestered as a result of tree growth was reduced by the amount lost resulting from tree mortality. Thus, net carbon sequestration and net annual oxygen production of the urban forest account for decomposition after tree death (
Annual avoided surface runoff was calculated based on rainfall interception by vegetation. Specifically, it is the difference between annual runoff with and without vegetation. Although tree leaves, branches and bark may intercept precipitation and thus mitigate surface runoff, only the precipitation intercepted by leaves was accounted for in this analysis (
Seasonal effects of trees on residential building energy use were calculated based on procedures described in the literature by
The structural value of the trees (
i-Tree Eco estimated that Scotlandville has 239.000 trees and the estimated tree cover is 23.7%. Small trees with diameter < 15 cm constitute 43.5% of the population (
The tree density in Scotlandville is 77 trees per hectare, and the highest tree density occurred in the wetland land cover/use type (295 trees ha-1), followed by forest (190 trees ha-1) and water (185 trees ha-1) land use types (
Among species in Scotlandville, Water oak, Black willow, Sugar maple (
Of all the trees inventoried within the 170 sample plots, 92% showed excelled health conditions as determined by the i-Tree model. Seven percent (7%) were in good condition and 1% was fair. None of the trees were determined to be in poor health condition, 0% were dying, and 0% were dead.
We estimated that each year, trees and shrubs in Scotlandville remove 96 tons of air pollutants (
It was estimated that the urban forests in Scotlandville store 88.700 tons of carbon. The gross carbon sequestration was about 3.880 tons of carbon per year, its associated ecological functional value (avoided cost) was $276.000, and its net carbon sequestration was about 3.650 tons. The ten species mostly contributing to carbon sequestration (in descending order of importance) were: Water oak, Black willow, Sugar maple, Willow oak, Live oak (
Oxygen production is one of the most commonly cited benefits of urban trees. The net annual oxygen production of a tree is directly related to the amount of carbon sequestered by the tree, which is tied to the accumulation of tree biomass. Trees in Scotlandville were estimated to produce 9.720 tons of oxygen per year. Water oak, Black willow, Sugar maple, Willow oak, and Live oak are the top 5 oxygen producers (
The trees of Scotlandville helped to reduce runoff by an estimated 121.200 m3 per year. Their associated ecological functional value (avoided costs) was $269.000. The five species (
Trees in Scotlandville were estimated to reduce energy-related costs from residential buildings by $324.000 annually. Trees also provide an additional $52.595 in value by reducing the amount of carbon released by power plants (a reduction of 739 tons of carbon emissions).
The annual total ecological functional value of urban forests around Scotlandville was estimated at 9 million US$, including values for an estimate carbon sequestration at $276.000, carbon storage at $6.97 million, pollution removal at $1.10 million, reducing runoff at $269.000, and lower energy costs and carbon emission reductions at $376.595. In addition to the ecological functional values, the urban forests have a structural value based on the trees themselves (
The standard i-Tree Eco sampling approach establishes approximately 150 to 200 field plots (i-Tree Manual). Based on the analysis of the results of the 14 cities assessed using i-Tree Eco, a sampling of 150 to 200 plots is statistically representative for the area (
The national average tree canopy cover in US major cities is 27.1% (
Compared to 21 cities that have been assessed using i-Tree Eco (
Trees have the potential to offset an enormous amount of carbon trapped in the atmosphere. According to a study by
Comparison between the gross and net carbon sequestration shows a difference of only 230 tons year-1 in Scotlandville. According to i-Tree Eco, to estimate the net amount of carbon sequestered by the urban trees, carbon emissions due to decomposition of dead trees were calculated based on methods detailed in
While the removal of air pollutants by the existing trees in Scotlandville was estimated in the amount of 96 tons per year, we also estimated by i-Tree Eco that Scotlandville’s trees yearly produce 8.91 tons of monoterpene, 125.53 tons of isoprene, and emit 134.43 tons of volatile organic compounds (VOCs) that may contribute to ozone formation. Integrative studies have revealed, however, that an increase in tree cover leads to reduced ozone formation (
Trees remove PM2.5 when particulate matter is deposited on leaf surfaces. This deposited PM2.5 can be resuspended to the atmosphere or removed during rain events and dissolved or transferred to the soil. This combination of events can lead to interesting results depending on various atmospheric factors. It should be noted that i-Tree Eco removal estimates of particulate matter incorporated a 50 percent resuspension rate of particles back to the atmosphere (
Our results indicate that in Scotlandville, although Live oak was not ranked among the top ten species by tree population size (
Air quality can be maximized by using trees that have a better pollution tolerance and removal capacity (
Among the 31 tree species in Scotlandville, two species are on the state invasive species list, Chinese Tallow (
Urban forests are a significant and increasingly vital component of the urban environment that can impact human lives. Understanding the value of an urban forest can give decision makers a better understanding of urban tree management (
The results of this study represent a baseline for the future development of a short- and long-term management plan for the urban forest in Scotlandville. The plan should be aligned with the Scotlandville Comprehensive Community Development Plan’s core values of community image, environmental stewardship, economic prosperity, infrastructure development, social policies, community awareness, recreation, and entertainment. The plan should contain strategies and implementation actions to support the Scotlandville community in finding a sense of investment in and relatedness to urban trees, and to maintain and enhance conditions necessary for a healthy natural environment.
Field data collection was done by Robert Chambers and assisted by John Marlin, Derric Chambers, and Sally Ross. We thank the USDA NIFA for the graduate assistantships. The undergraduate research stipends were from the NASA and USGS funded projects.
Map of the study area with indication of sample plots (yellow circles).
Tree population by diameter class (DBH): stem diameter at 1.4 m.
Tree density (number of trees per ha) on different land use type.
Top ten ranked tree species by population in Scotlandville. (a): Percent of total tree population in Scotlandville; (b): Percent of total tree leaf area in Scotlandville; (c): Percent of population plus percent of leaf area.
Species | Number of trees | Percent of Population (%)a | Leaf areaper km2 | Percent ofLeaf Area (%)b | ImportanceValuec |
---|---|---|---|---|---|
Water Oak( |
27.860 | 11.6 | 9.63 | 24.0 | 35.7 |
Black Willow( |
40.423 | 16.9 | 4.95 | 12.3 | 29.2 |
American Elm( |
26.592 | 11.1 | 2.85 | 7.1 | 18.2 |
Sugar Maple( |
14.537 | 6.1 | 4.45 | 11.1 | 17.2 |
Willow Oak( |
12.943 | 5.4 | 3.13 | 7.8 | 13.2 |
Sweetgum( |
17.124 | 7.2 | 1.92 | 4.8 | 11.9 |
Southern Red Oak( |
18.783 | 7.9 | 0.65 | 1.6 | 9.5 |
Tallowtree( |
15.219 | 6.4 | 1.19 | 3.0 | 9.3 |
Red Maple( |
10.255 | 4.3 | 1.45 | 3.6 | 7.9 |
9.968 | 4.2 | 0.98 | 2.5 | 6.7 |
Annual pollution removal by trees in Scotlandville and the associated value (avoided costs).
Pollutants | Removal(Ton) | Value(US$ × 1000) |
---|---|---|
CO | 1.76 | 2.00 |
NO2 | 8.65 | 5.38 |
O3 | 39.54 | 138.24 |
PM10 | 38.07 | 561.46 |
PM2.5 | 2.68 | 397.62 |
SO2 | 5.69 | 1.18 |
Total | 96.39 | 1101.88 |
Top ten ranked tree species by ecological functions and values in Scotlandville. (na): species not ranked among top ten for a particular function or value.
Species | Oxygen(tons) | Net CarbonSequestration(tons yr-1) | RunoffReduction(m3 yr-1) | Carbonsequestrationvalue (US$ × 1000) | Runoffreduction value (US$ × 1000) | Structuralvalue(US$ × 1000) |
---|---|---|---|---|---|---|
Water Oak |
2.243.16 | 841.18 | 27.475 | 59.72 | 64.60 | 28.24 |
Black Willow |
1.247.90 | 467.96 | 14.110 | 33.23 | 33.17 | 11.60 |
Sugar Maple |
961.72 | 360.64 | 12.716 | 25.61 | 29.90 | 10.82 |
Willow Oak |
676.08 | 253.53 | 8.932 | 18.00 | 21.00 | 11.69 |
Live Oak |
642.46 | 240.92 | 3.353 | 17.11 | 7.88 | 42.02 |
Pecan |
492.04 | 184.52 | 3.550 | 13.10 | 8.35 | 8.85 |
American Elm |
462.82 | 173.56 | 8.105 | 12.32 | 19.06 | 9.51 |
Red Maple |
400.83 | 150.31 | 4.100 | 10.67 | 9.64 | na |
Sweetgum |
394.51 | 147.94 | 5.434 | 10.50 | 12.78 | 16.97 |
388.45 | 145.67 | na | 10.34 | na | 7.27 | |
Tallowtree |
na | na | 3.404 | na | 8.00 | 5.41 |
Values (per ha) of tree effects on carbon storage, carbon sequestration, and pollution removal in 21 cities. Data for thirteen US and two Canadian cities are from the I-tree Eco analysis results posted on http://www.i-tree.org. (a):
City | Tree Density(trees ha-1) | Carbon Storage(tons ha-1yr-1) | Carbon Sequestration(tons ha-1yr-1) | Pollution Removal(tons ha-1yr-1)e |
---|---|---|---|---|
Calgary, Canada | 165 | 2.5 | 0.120 | 3.6 |
Atlanta, GA | 276 | 15.9 | 0.550 | 39.4 |
Toronto, Canada | 154 | 6.4 | 0.258 | 15.6 |
New York, NY | 65 | 6.8 | 0.214 | 17.0 |
Baltimore, MD | 123 | 11.5 | 0.312 | 16.6 |
Philadelphia, PA | 62 | 6.3 | 0.190 | 13.6 |
Washington, DC | 121 | 13.3 | 0.410 | 21.2 |
Boston, MA | 83 | 9.0 | 0.297 | 16.0 |
Woodbridge, NJ | 164 | 10.8 | 0.375 | 28.4 |
Minneapolis, MN | 65 | 6.7 | 0.238 | 16.4 |
Syracuse, NY | 135 | 10.8 | 0.338 | 13.6 |
Morgantown, WV | 296 | 17.0 | 0.532 | 23.8 |
Moorestown, NJ | 153 | 12.5 | 0.400 | 25.2 |
Jersey City, NJ | 36 | 2.2 | 0.094 | 8.6 |
Freehold, NJ | 95 | 16.0 | 0.437 | 33.6 |
Scotlandville, LA | 77 | 29.0 | 0.452 | 0.1 |
Perth, Australiaa | 83 | 15.0 | 0.300 | 0.2 |
Barcelona, Spainb | 141 | 11.2 | 0.537 | 0.1 |
London, UKc | 53 | 15.0 | 0.490 | 0.1 |
Beijing, Chinad | 79 | 7.4 | 0.378 | 0.3 |
Houston, TX | 337 | 20.0 | 0.815 | 30.0 |
Average | 132 | 10.9 | 0.386 | 16.3 |