Potential for moisture stress on vegetation on the Cumberland Plateau of Tennessee

Because precipitation during the months of the growing season generally is lower than for the rest of the year and soils are mostly shallow, moisture stresses that are detrimental to plant growth are frequent.

The objective of this study was to evaluate the potential for moisture stress on vegetation for an area of the Cumberland Plateau near Crossville, Tennessee. Determining the recurrence of specific climatic moisture deficits, soil moisture deficits, and the impact of soil moisture deficits for different groupings of plants were all part of the analytical design.

In order to deal with long-terra as well as short-term moisture conditions two methods were employed. A water budget model was used to analyse moisture deficits on a monthly basis. Short-term moisture conditions were evalated by determinating the probability of the occurrence of dry-day sequences of various lengths.

The study showed that moisture stress on vegetation is relatively frequent in the study area. Plants most affected are those with a limited root system or where soils are shallow, which is widespread. There is a definite trend that soil moisture depletion increases from southwest to northeast as a result of prevailing meteorologic conditions.

Temporal differences of moisture stress are marked as well. Moisture deficits increase steadily from May to October. Moisture conditions are significantly less favorable in the last half of the growing season compared to the early half.

From a perspective of moisture supply, deep rooting crops with critical moisture sensitive stages in the early season are more suited for the study area than crops that have a shallow root system and that have moisture sensitive periods in the late part of the growing season.

Tree species such as Shortleaf pine and Loblolly pine appear best suited here because they do not have a critical late summer stress period. The study has shown that because of thin soils and low total moisture storage in most of the forest soils it is reasonable to expect trees to suffer severe moisture stresses quite frequently. Survival of tree seedlings is threatened, especially on newly replanted plots where there is no protective tree canopy to reduce transpiration rates.