The amount of oxygen produced is estimated from carbon sequestration based on atomic weights : net O2 release ( kg / yr ) = net C sequestration ( kg / yr ) × 32 / 12 . To estimate the net carbon sequestration rate , the amount of carbon sequestered as a result of tree growth is 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 ( Nowak et al 2007 ). For complete inventory projects , oxygen production is estimated from gross carbon sequestration and does not account for decomposition .
Avoided Runoff :
Annual avoided surface runoff is calculated based on rainfall interception by vegetation , specifically 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 is accounted for in this analysis .
The value of avoided runoff is based on estimated or user-defined local values . For international reports that do not have local values , the national average value for the United States is utilized and converted to local currency with user-defined exchange rates . The U . S . value of avoided runoff is based on the U . S . Forest Service ' s Community Tree Guide Series ( McPherson et al 1999 ; 2000 ; 2001 ; 2002 ; 2003 ; 2004 ; 2006a ; 2006b ; 2006c ; 2007 ; 2010 ; Peper et al 2009 ; 2010 ; Vargas et al 2007a ; 2007b ; 2008 ).
For this analysis , avoided runoff value is calculated based on the price of $ 0.07 per ft ³. Building Energy Use :
If appropriate field data were collected , seasonal effects of trees on residential building energy use were calculated based on procedures described in the literature ( McPherson and Simpson 1999 ) using distance and direction of trees from residential structures , tree height and tree condition data . To calculate the monetary value of energy savings , local or custom prices per MWH or MBTU are utilized .
For this analysis , energy saving value is calculated based on the prices of $ 211.10 per MWH and $ 13.80 per MBTU . Structural Values :
Structural value is the value of a tree based on the physical resource itself ( e . g ., the cost of having to replace a tree with a similar tree ). Structural values were based on valuation procedures of the Council of Tree and Landscape Appraisers , which uses tree species , diameter , condition , and location information ( Nowak et al 2002a ; 2002b ). Structural value may not be included for international projects if there is insufficient local data to complete the valuation procedures .
Potential Pest Impacts :
The complete potential pest risk analysis is not available for studies outside of the United States . The number of trees at risk to the pests analyzed is reported , though the list of pests is based on known insects and disease in the United States .
I-Tree Report of Ecosystem Analysis at Mount Auburn Cemetery Insert to the Climate Action and Sustainability Plan
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