Life History and Disturbance Response of Fraxinus pennsylvanica (green ash)
Family: Oleaceae
Guild: opportunistic, fast-growing understory tolerant
Functional Lifeform: medium-size deciduous tree
Ecological Role: grows best on fertile, moist well-drained soils along streams and in bottomlands; succeeds shade-intolerant pioneers and withstands understory conditions for many years
Lifespan, yrs (typical/max): 125/150
Shade Tolerance: tolerant, but varies throughout its range
Height, m: 14-17
Canopy Tree: yes
Pollination Agent: wind
Seeding, yrs (begins/optimal/declines): 20/40/125
Mast Frequency, yrs: 3-5
New Cohorts Source: seeds or sprouts
Flowering Dates: late spring
Flowers/Cones Damaged by Frost: yes
Seedfall Begins: early fall
Seed Banking: 1 yr +
Cold Stratification Required: yes
Seed Type/Dispersal Distance/Agent: winged/ to 200 m/ wind, water
Season of Germination: spring
Seedling Rooting System: variable
Sprouting: seedling and stump sprouts (from small stems) common
Establishment Seedbed Preferences:
Substrate: variable
Light: overstory shade
Moisture: moist required
Temperature: neutral
Disturbance response:
Fire: Green ash is well-adapted to occasional fire. It is tolerant of dormant-season low-intensity fires. Green ash communities have shown an increase in biomass, density, and cover when burned. It is thin-barked and readily topkilled by low- to moderate-intensity surface fires, and it sprouts prolifically from adventitious buds in the root crown or from root suckers. Seedling establishment probably occurs within two years after the fire from seeds of surviving trees onsite or from offsite seeds carried by wind. Prescribed burning has been used to stimulate regrowth in older stands, but is not recommended in bottomland stands where it is grown for timber, and where decay from fire-caused wounds might reduce wood value.
Weather: Green ash is extremely tolerant of flooding.
Air pollution: Green ash has had variable ratings (tolerant to sensitive) to sulphur dioxide. It is sensitive to ozone and intermediate in sensitivity to hydrogen fluoride. Variable foliar symptoms to high ambient ozone have been noted (none to some). Seedlings exhibited reduced height growth and biomass accumulation under controlled fumigation with ozone.