Effects of Shade, Litter and Root Competition on Old-Field Vegetation in South Carolina

Abstract

MONK, C. D. AND F. C. GABRIELSON (University of Georgia, Athens, GA 30602 and University of Alabama, Tuscaloosa, AL 35405). Effects of shade, litter and root competition on old-field vegetation in South Carolina. Bull. Torrey Bot. Club 112:383-392. 1985.-The effects of shade litter and root competition on old-field herbaceous vegetation were examined by using two different approaches: one involved the addition of shade and/or litter to plots in an old-field, while the other involved eliminating root competition by trenching along the side of singly-growing pine trees. Vegetation was sampled prior to treatment and again after one and two years of treatment. The normal course of succession was a decrease in density and biomass of annuals, while the density and biomass of perennials doubled. Species more characteristic of early old-field successional stages were more apt to be inhibited by treatment than species characteristic of later successional stages. In the experimental treatments, shade reduced biomass and density, except in Cynodon. Litter alone produced a major decrease in the number of individuals and in biomass; perennial grasses were affected the least and some (Andropogon, Aristida, Leptoloma) showed a major increase over controls. Shade + litter drastically reduced (60-70%) density and biomass (stems and leaves) of annuals and increased the density of perennials, especially Cynodon with shade and pine litter and Andropogon on shade and hardwood litter. In the trenching experiment, the annuals showed no real response in trenched, litter-intact quadrats, while the perennials increased fourfold in density. Annuals had higher densities (100% increase) in response to trenched + litter removal treatment; perennials showed no enhancement of density with the trenched, litter-removal treatment. The largest number of species invaded trenched, litter-removal quadrats. Plants on unshaded quadrats produced more root biomass than on shaded quadrats. More root biomass was produced on hardwood litter plots than under pine litter. Less root biomass was produced on shaded or unshaded + litter plots after two years. Annuals were inhibited by dense shade, root competition and litter. Root competition and shade were more important in suppressing perennials than was litter.