OUTDOOR CORNER: BOTTOMLAND FORESTS RARE, BUT EXIST

A hunt for the largest of Missouri's champion trees will take you to New Madrid County. There, in the remnants of our state's once-great bottomland forests, stands a 118-foot-tall cherrybark oak measuring 26 feet around, with a crown that is 110 feet wide. Not far away is the state's champion baldcypress, with its crown rising 128 feet above the murky backwaters.

The dredging and ditching operations that began after the turn of the century have markedly reduced the expanse of the Bootheel's wet-bottomland forests. Today, less than 5 percent of New Madrid County's 421,300 acres are forested. Fields of soybeans, rice, cotton and corn have replaced most of the oak-gum-cypress forest that once grew in the swamplands and backwaters of the Mississippi River.

Wet-bottomland forests once occupied nearly all of the flood plains along the margins of Missouri's great rivers, or more than 2.5 million acres. Those remaining, less than 1 percent of the state's forested lands, contain a variety of tree species that grow on alluvial soils and can tolerate frequent flooding and periodic ponding.

These forests consist primarily of hardwood species, with the exception of baldcypress, a conifer that loses its leaves in autumn and produces "cypress knees" when permanently flooded.

Baldcypress grows in association with water hickory, pumpkin ash, sweetgum, water locust, and overcup and pin oaks, in what remains of those wet-bottomland forests.

The rich bottomland soils along Missouri's major rivers drew settlers looking for new land to farm. They quickly cleared the trees to plant their first crops. Steamboats moving goods and people along major rivers and their tributaries relied on wood cut from the bottomland forests to fuel their boilers.

In these forests, pecans, the largest species of our native hickories, reached heights of over 100 feet and diameters in excess of 4 feet. Huge elms, sycamores and cottonwoods - in sizes and numbers no longer found - once lined the banks of the state's great rivers.

Agriculture has become the primary use of these fertile lands, with less than 30 percent of the Missouri river-border areas in forest. Elms, ash, sugar and silver maple, cottonwood, river birch, bitternut hickory, butternut, black walnut and a mixture of upland oaks are among the species commonly found today in these moist (mesic) bottomland forests.

These bottomland hardwood forests are distributed throughout the state. The tree canopies are dense, ranging in height from 90 to 140 feet. They have well-developed understories of spicebush, buckeye, pawpaw and vines. The ground flora is rich and diverse, composed of a mixture of herbaceous plants including bluebells, white trout lily, fragile fern and pale violet. In the spring, they are a prime showcase for native, ephemeral flora.

Flooding, high winds and land-use conversion are the significant factors influencing change.

Once disturbed, these sites often develop nearly pure groves of elm, boxelder and cottonwood.

In the Ozarks, there are a number of streams with narrow, sloping channels and well-drained soils. The soils are coarse and rocky with large boulders and significant amounts of gravel.

These high-gradient streams are subject to flash flooding. The tree canopy, which may be 60 to 90 feet in height, is more open due to frequent flood damage.

Undermining currents uproot individual trees along rock banks, and abrasion by boulders and other debris results in stream-side trees with damaged trunks.

These dry-mesic bottomland forests include white and northern red oaks, sycamore, black walnut, flowering dogwood and Ohio buckeye. The understory is often poorly developed, with shrubs and small trees ranging from 15 to 25 feet in height, and vines having root systems that can withstand the violent floods. The ground cover in these narrow bottomland and upland waterways is sparse, made up of sedges, St. John's wort, bellflower and false wild garlic.

A number of bottomland species have become popular lawn trees. Sweetgum, a major timber species in the South, is native to the lowlands of the Missouri Bootheel. With its pyramidal crown and star-shaped leaves that turn from waxy green to brilliant yellow, then red, in autumn, it is recognized as an excellent ornamental. Pin oak is another bottomland forest species that does well in lawn and landscape plantings.

Popular because of its quick early growth and development, silver maple is often planted around new homes. Unfortunately, the branches of this stream-side native are easily broken in winter ice storms and high winds. It is not a recommended landscape tree.

Shallow-rooted and used to readily available moisture, species of bottomland forests do not survive well during extended periods of drought or when planted on sandy, well-drained soils.

Selecting the proper location and providing after-planting care is important to ensuring the health of bottomland species used as ornamentals.

Although bottomland species experience numerous seasonal and flash floods in a normal lifetime, the great floods of 1993 and 1995 produced extreme circumstances for trees along the Mississippi and Missouri rivers. Flood depths ranged from 2 to 20 feet and remained for a few days to more than 3 months. Overall mortality rates varied with flood duration, with tree losses at 20 to 30 percent along the major rivers in the western part of the state and as high as 95 percent in some portions of the upper Mississippi.

Species that were found to be most sensitive to flooding include nearly all conifers, dogwood, hard maple, hackberry, walnut, black locust, and all upland hickories and oaks. Most willows, cottonwoods, honeylocust and baldcypress survived the flood, independent of flood duration.

Flood waters undermine the root systems of trees growing along streambanks. Floating debris inflict wounds on trunks and exposed roots, opening avenues for disease-causing organisms.

Extended periods of flooding place trees under stress. Extensive spring rains when leaves are expanding lead to rapid development of foliar diseases.

Sycamore anthracnose, caused by a common fungus, can be identified by brown to black blotches on leaves that progress along the petiole to the tip. New leaves may wither before opening and twigs blacken. Only when defoliation exceeds 50 to 60 percent, however, do trees become stressed.

Yellowing foliage and branch dieback, along with the development of "witches' brooms" along the trunk, are symptoms as ash yellows, an organism affecting white ash. Groups of white ash trees may exhibit varying degrees of decline, while green ash, a more common bottomland species, is somewhat tolerant of this disease.

A more recently discovered disease-causing organism that affects bottomland trees is butternut canker. It has been working its way south from the Lake states, where it was discovered in the 1960s. It is a major threat to our native butternut, the littler "white" walnut that is found growing along many Missouri streams.

In a recent Missouri survey, only 10 percent of the butternuts were found to be canker-free, 25 percent were already dead and 50 to 60 percent were canker-infected and in declining health.

Finding and propagating resistant individuals is a part of the long-term plan for recover of this species within its native range.

Joe Garvey is a district forester with the Missouri Department of Conservation.