Flooded forests face unknowns ahead
The stage for 2019 floods was set by heavy snowfall in the upper Midwest, followed by excessive rainfall patterns in the Plains, Midwest and South, resulting in significant flooding all along the Mississippi River.
The spring and early summer of 2019 has been among the wettest on record for many states located along the Mississippi and Ohio rivers.
Mississippi River remains very high, forcing the opening of various spillways to disperse water over a larger area. The effect of the flooding has impacted not only the lives of people living in these areas, but has also begun to impact forests, wildlife and
the Gulf of Mexico. Uncertainty of One of the areas the damage's extent bearing the brunt of is based on several extended flooding variables: rainfall are the 11 Mississippi patterns, floodwater counties found movement, water along the Mississippi temperature, oxygen River. levels, longevity
With no end Rousseau and intensity of in sight to the flooding, the rainfall, and drainage time search has begun to determine and obstructions. Topography the extent of damage to the also defines the possibility variety of hardwood species and extent of tree damage. throughout the affected area. Certainly, damage will range
Unfortunately, there are from very little to significant no simple or definitive answers with possible mortality because this natural among species that are not disaster is not a stable phenomenon tolerant to extended flooding. and continues to Many factors influence change. The impact will increase a tree's ability to survive with time, especially as either seasonal and/or extended the flooding enters into the flooding, such as summer months. siltation, tree age, water temperature, trapped water, species tolerance to flooding, season(s) of flooding and duration of flooding.
Hardwood species vary greatly in their tolerance of flooding. As expected, riparian species such as black willow, eastern cottonwood, bald cypress, swamp tupelo, overcup oak and sycamore are tolerant to flooding. These species are adapted to seasonal flooding during the dormant season and early spring.
Records taken by the U.S. Forest Service at Stoneville in the Mississippi Delta during and after the 1973 flood indicated very high mortality of newly planted seedlings. Sweetgum, sycamore, sweet pecan, water oak, Nuttall oak, Shumard oak and willow oak seedlings that had one or more full growing seasons survived much better except in areas where water became trapped. More flood-sensitive species such as black walnut and yellow poplar were shown to exhibit high mortality rates even in older trees.
This year, the Mississippi River has remained high for a much longer period than seen even in the 1973 flood. Although we were relatively certain that the majority of the damage would have been limited to young, early-planted seedlings, the concern has shifted to older trees that will be stressed as water temperatures increase and the oxygen levels decrease.
Early symptoms of flood stress may include leaf yellowing, small leaf size, epicormic sprouting and crown dieback. The one bright note is the resilience of healthy forests. Even if they exhibit these symptoms, they could recover over the next couple of years, if flooding is not repeated.
Extension Outdoors is a column authored by several different experts in the Mississippi State University Extension Service. Dr. Randy Rousseau is an extension research professor of hardwoods for the MSU Extension Service. The opinions in this column are Rousseau's and do not necessarily reflect the views of The Starkville Daily News or its staff.