Modelling air purification
The
i-Tree Streets Model (i-Tree,
2018) was used to assess air purification benefits in metropolitan
Shenyang. We first used the method proposed by
McPherson (2010) to select the best city
match, i.e. to pick a “best fit” climate zone for this Asian city. The
best match city for Shenyang was Queens, New York, so the “US northeast
climate zone” was chosen for the modelling. To
exam the effects of
population
density, city sprawl (urban-suburban gradient) and district development
plans, i.e. government policy on the distribution of air purification
ecosystem services provided by street tree assemblages , we regrouped
the field data of sub-districts in 3 ways:
(1) by population density
(districts with population density > 10,000
persons/km2 were grouped as P1, districts with
1,000-10,000 persons/km2 were assigned to P2, and
districts with < 1,000 persons/km2 were
placed in group P3), (2) by beltways (sub-districts within the first
beltway were grouped as B1, sub-districts between the first and the
second beltway were assigned to B2, and the sub-districts between the
second and the third beltway were places in B3 (Figs 1B and 1C), (3) by
districts (the districts named HG, HP, S, T, Y, HN and D respectively).
We got 13 groups in total. We then ran the i-Tree Street Model on each
group of field data, individually and got average tree benefit of air
purification (ATB, $/tree) and total benefit of air purification for
each group.