Life History & Disturbance Response of Ulmus americana American elm

Family: Ulmaceae
Guild: pioneer, spring-dispersed, moist-site tolerant
Functional Lifeform: large deciduous tree
Ecological Role: grows best on rich, well-drained soils on stream terraces and moist uplands; colonizes wet areas on open, disturbed sites; also common under pioneer species; rarely becomes dominant because of its susceptibility to the wilt fungus Ceratocystis ulmi (Dutch elm disease)
Lifespan, yrs (typical/max): 175/300
Shade Tolerance: intermediate
Height, m: 30-38
Canopy Tree: yes
Pollination Agent: wind
Seeding, yrs (begins/optimal/declines): 15/40/125
Mast Frequency, yrs: 1
New Cohorts Source: seeds or sprouts
Flowering Dates: early spring
Flowers/Cones Damaged by Frost: yes
Seedfall Begins: late spring
Seed Banking: up to 1 yr
Cold Stratification Required: no
Seed Type/Dispersal Distance/Agent: winged/ to 200 m/ wind, birds, water
Season of Germination: spring
Seedling Rooting System: variable
Sprouting: stump sprouts and root suckers common
Establishment Seedbed Preferences
Substrate: mineral soil
Light: overstory shade
Moisture: moist required
Temperature: neutral
Disturbance response:
Fire: Fire rarely occurs in the moist areas where American elm typically grows. When fire does occur and conditions are dry, American elm greatly decreases following fire. Alternatively, American elm invades where fire is suppressed. Fire occurs at long intervals in the northern parts of its range, but more often in southern bottomlands, where autumn and early spring fires cause much damage. Low- and moderate-intensity fires topkill seedlings and saplings, and often damage larger trees. Wounded trees are susceptible to heart rot fungi. Small topkilled trees sprout from the root crown or from root suckers. Wind- and water-dispersed seed are important in the establishment of American elm following fire.
Weather: American elm tolerates dormant-season flooding but not growing season flooding. Small trees are susceptible to sunscald. Open-grown trees are susceptible to ice and snow damage. It is windfirm and moderately drought resistant.
Air pollution: American elm is intermediate to sensitive to sulphur dioxide, and is sensitive to ozone. It is tolerant to hydrogen fluoride. No symptoms of foliar injury were noted in areas of high ambient ozone.
Exotics: The dominance of all North American elm species has been significantly decreased by Dutch elm disease (Ceratocystis ulmi), an exotic wilt fungus which was introduced from Europe in 1930. It is spread by two species of elm bark beetles, one European (Scolytus multistriatus) and the other native (Hylurgopinus rufipes). American elms are the most susceptible of all the elms. Juvenile trees have some resistance to the disease, and elms produce wind-borne seeds before they die. Elms will likely persist in the forest as an understory species.