Arboriculture & Urban Forestry 40(5): September 2014 MTLA’s total operating budget was approximately $1.5 million. Grants (75%) and corporate spon- sors (25%) were the major sources of funding. Because Los Angeles is such a large city (3.8 million population; 1,225 km2 287 ), MTLA relies on its internal city departments and non-profit partners to deliver the program to neighborhood residents. The six non- profit partners are: Fuego Tech Rangers, Hollywood/ Los Angeles Beautification Team, Koreatown Youth & Community Center, Los Angeles Conservation Corps (LACC), North East Trees, and TreePeople. MTLA has coordinated street, park, and yard tree planting projects. Street tree planting proj- ects occur along heavily traveled corridors, where environmental benefits and program visibility are maximized by planting large trees. Street and yard tree planting projects occur in residential areas when trees are “adopted” by locals who agree to maintain the trees planted on their prop- erty or along the street. Tree adoption requests are parceled out by MTLA staff to the non-profit responsible for activities in the area. Residents are encouraged to report trees that they plant on private property via the MTLA website, but the numbers are small (1% to 2% of total planted). Also, LACC runs a residential shade-tree pro- gram that delivers trees directly to homes through an application process. Trained staff assists with tree selection and location, coordinates planting events, provides training on planting and tree care, supervises plantings, and conducts follow- up inspections to ensure trees are irrigated. Trees planted under supervision of the partner non- profits are reported monthly by LACC, which purchases and distributes most of the trees. Park tree planting projects are held in city parks managed by the Los Angeles Recreation and Parks Department (RPD). Events are organized by the non-profit TreePeople and supported by RPD. Tree- People trained over 6,660 volunteers who partici- pated in 90 tree planting events from 2006 to 2010. Preliminary MTLA Benefit Assessment In 2006, U.S. Forest Service researchers began to ad- dress questions posed by the fledgling MTLA initia- tive—How many trees already exist in Los Angeles? Is there room for a million more trees? What envi- ronmental and other benefits will one million new trees provide? A satellite-based analysis determined that the canopy created by approximately 11 million trees covered 21% of Los Angeles (McPherson et al. 2011). Their preliminary benefit assessment incorpo- rated several important assumptions regarding tree planting numbers, species mix, and survival rates. Planting number and the annual rate at which trees are planted directly influence the future stream of benefits they provide. The mature sizes and growth rates of the species planted influence their leaf area and biomass. Generally, increased leaf area and biomass are associated with increased benefits, such as air pollutant reduction, rainfall interception, and carbon storage (Nowak et al. 1994, Xiao et al. 2000). McHale et al. (2007) found that mature tree size was the third most important variable influencing cost effectiveness of tree plant- ing projects, because larger-stature trees stored more carbon. Several studies have found that esti- mates of future tree benefits are very sensitive to assumed survival rates (Hildebrandt and Sarkov- ich 1998; Nowak et al. 2002). For example, Morani et al. (2011) reported that doubling the average annual mortality rate from 4% to 8% resulted in a six-fold decrease in projected peak carbon stor- age. Strohbach et al. (2012) found that mortality had a stronger effect on carbon biomass in trees aſter 50 years than growth. Going from maximum to minimum growth rate [i.e., 0.71 and 0.58 cm per year diameter at breast height (DBH)] reduced biomass by 45%, compared to 70% going from low to high mortality (0.5% and 4% per year). Based on discussions with MTLA planners, the preliminary study assumed that one million trees were planted during the first five years of the program at an increasing rate, from 50,000 in 2006 to 290,000 in 2010. Trees were distributed into mature-size classes based on the relative fre- quency of vacant planting sites obtained from remote sensing of unplanted irrigated grass areas. Aſter calibrating remotely-sensed vacant tree sites with ground-truthed data, approximately 2.47 mil- lion planting sites were identified in Los Angeles; 52% were for small trees (4.6 m crown diameter at maturity). Hence, the assessment assumed that 52% of the one million trees planted were small- stature trees, 38% were medium trees (9.1 m crown diameter), and 10% were large trees (15.2 m). The analysis incorporated two scenarios that reflected a range of uncertainty regarding sur- ©2014 International Society of Arboriculture
September 2014
| Title Name |
Pages |
Delete |
Url |
| Empty |
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success. You will be contacted by Washington Gas with follow-up information regarding your request.
This process might take longer please wait
