WATER-STRESS IN LONGLEAF PINE INDUCED BY LITTER REMOVAL

Forest litter layer acts as a nutrient pool to support future growth of trees and as a blanket which intercepts and absorbs rainfall and insulates soil from evaporative water loss. Litter disturbance can modify either of these functions. Soil moisture content and xylem pressure potential were determined in a longleaf pine plantation for 7 weeks following litter removal. Two weeks following treatment, xylem pressure potential of trees in control, red straw removal and total litter removal plots diverged. Trees in the total litter removal plot had the lowest xylem pressure potential (i.e. most stressed), control trees had the highest xylem pressure potential, and trees in the red straw removal plot were intermediate. Differences in xylem pressure potential among treatments were consistent throughout the season, regardless of precipitation or drought. Soil moisture content also showed different patterns based on the particular litter removal treatment. Differeces in soil water content and xylem pressure potential could explain observed growth reductions of trees in plantations where litter had been removed. Therefore consideration of the potential modification of both the hydrologic and nutrient cycles should be made prior to litter removal. © 1979.