Agriculture & Biology
ozone
99%
conservation areas
90%
signs and symptoms (plants)
75%
vegetation
70%
Viburnum cassinoides
67%
Corylus cornuta
59%
Prunus pensylvanica
55%
Prunus serotina
45%
Apocynum androsaemifolium
31%
National Ambient Air Quality Standards
31%
U.S. Fish and Wildlife Service
24%
Viburnum
23%
wilderness
23%
Fraxinus
20%
United States Environmental Protection Agency
20%
air quality
19%
ash (inorganic matter)
16%
Populus
15%
national parks
14%
deterioration
12%
incidence
11%
monitoring
10%
Earth & Environmental Sciences
refuge
100%
wildlife
81%
ozone
73%
vegetation
56%
wilderness area
21%
air quality management
20%
ambient air quality
18%
bioindicator
16%
quality standard
16%
field survey
15%
national park
14%
ash
12%
decision
9%
services
9%
fish
9%
monitoring
8%