Document: JUS-3-29-3

Light distribution in mesic grasslands: Spatial patterns and temporal dynamics.

WU, X.B.* ¹ and J.D.DERNER ²

Texas A&M University, College Station, TX 77843-2126 USA ¹
USDA-ARS, Temple, TX 76502-9601 USA ²

Abstract:
An experiment was conducted on three mesic grasslands (AH: annually hayed; U: unmanaged since 1985; and C: formerly cultivated (prior to 1939) field that was abandoned to address the spatial patterns and temporal dynamics of light distribution. Frequency distributions of relative light intensity (RLI)were similar for C and U grasslands at all sample dates, but quite different for the AH grassland. A majority (60-70%) of sample points within C and U grasslands were in the lowest (0-20%) RLI class. In contrast, 28% was the maximum value in this class for AH grassland. Management history had a consistent effect on spatial heterogeneity of light distribution across all sampling dates, with spatial heterogeneity 3-4 fold greater in the AH grassland than the U and C grasslands in the early growing season. The degree of temporal variation in the normalized lacunarity curves for the three grasslands (U>AH>C) provide a measure of the temporal stability in the spatial configuration of the canopy structure. Consistent spatial heterogeneity of light distribution within the C and AH grasslands across sample dates, and the negative relationship of degree of spatial heterogeneity with standing crop (i.e., high spatial heterogeneity with low standing crop) emerged as general patterns. Integrating lacunarity analysis and traditional structural measurements may be a way to assess functional consequences of structural changes (e.g., growth form changes) caused by different management in grassland ecosystems.

Keywords: lacunarity, light distribution, mesic grasslands

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