Document: JUS-3-29-4

Concurrence of light availability and root interference in mesic grasslands.

DERNER, J.D.*, H.W.POLLEY, H.B.JOHNSON and C.R.TISCHLER

USDA-ARS, Grasland, Soil & Water Research Laboratory, Temple, TX 76502-9601 ¹

Abstract:
An experiment was conducted on three mesic grasslands (AH: annually hayed, grass/forb mix; U: unmanaged since 1985, forb-dominated; and C: formerly cultivated field that was abandoned, bunchgrass-dominated) to address the concurrence of light availability and root interference. Photosynthetic active radiation (PAR) was quantified for 32, 3.1X5 cm areas within each of 7, 1X1 m plots in each grassland on 30 April, 29 May and 26 June. These same areas were destructively harvested (depth = 5 cm) on 2 July. Roots were digitally scanned to determine root length, surface area and volume. In the C grassland, Spearman correlation coefficients between light availability from all sample dates and each root variable were negative (P<0.10). Correlations between light and roots were negative in the AH grassland, but the only correlations that were significant were those for between light and root biomass on all sample dates, and between light and the other root variables for the May sample date. There were no significant correlations in the U grassland for any sample date. Differences in the concurrence of light availability and root interference between grasslands are likely the result of previous management which modified the dominant growth form. These data indicate that the C, and to a lesser extent, the AH grassland have an increased probability of invasion by unwanted species given the concurrence of high light availability and low levels of root interference.

Keywords: light availability, root interference, mesic grasslands

This abstract is being presented at: 10:30 AM in session:
Poster Session #1: Light Relations.