|Lane, Diana - UNIV OF IL AT CHICAGO|
|Lauenroth, William - COLORADO STATE UNIVERSITY|
Submitted to: Journal of Vegetation Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 15, 1999
Publication Date: June 1, 2000
Citation: LANE, D.R., PETERS, D.C., LAUENROTH, W.K. CHANGES IN GRASSLAND CANOPY STRUCTURE ACROSS A PRECIPITATION GRADIENT. JOURNAL OF VEGETATION SCIENCE. 2000. V. 11. P. 359-368. Interpretive Summary: The aboveground, or canopy, structure is important to the ability of plants to capture sunlight and is a component of rangeland productivity and forage availability. There is very little quantitative information about how canopy structure varies between different types of rangelands and how this variation influences ecosystem processes. We measured canopy structure and dlight transmission for seven sites in three rangeland types (shortgrass steppe, northern mixedgrass prairie, tallgrass prairie) in the Cental Grassland region of the U.S. to examine how these properties are related to productivity. We found that canopy height, biomass, and leaf area increased and light availability at the soil surface decreased as productivity increased across the region. We also found that regional changes in plant species composition had important effects on canopy structure. Our results are important because they indicate aboveground processes become increasingly important to rangeland structure and dynamic as precipitation and productivity increase. We expect these changes in canopy structure also affect other ecosystem processes, such as nutrient cycling and succession.
Technical Abstract: The canopy structure of a grassland community affects ecological processes by influencing the amount and quality of light available to individual plants growing within the community. Canopy structure may also affect water and nitrogen availability by determining the interception of precipitation and dry deposition. Across a gradient of increasing productivity, there is typically an increase in canopy height, aboveground biomass, and leaf area. These patterns suggest that the relative importance of canopy structure in controlling key ecological processes is likely to increase with increasing productivity. We quantified vertical profiles of light transmission, biomass, and leaf area for three natural grassland types in the Central Grassland region of the United States to examine how these properties varied with increased productivity. Overall, increased productivity was correlated with increased canopy height, decreased light availability at the soil surface, increased seasonal changes in light transmission, increased biomass and leaf area at higher canopy layers, and increased leaf area index. We also found that changes in the proportion of species of different stature collectively resulted in changes in community canopy structure. The changes in canopy structure we documented support the prediction that aboveground processes related to capturing light increase in relative importance with increasing precipitation and productivity. These changes in canopy structure are likely to affect resource availability and successional dynamics across a productivity gradient.