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United States Department of Agriculture

Agricultural Research Service

Title: Changes in Mass and Chemistry of Plant Roots During Long-Term Decomposition on a Chihuahuan Desert Watershed

Authors
item Mun, H - KONGJU NAT'L UNIV, KOREA
item Whitford, Walter

Submitted to: Biology and Fertility of Soils
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 1, 1997
Publication Date: N/A

Interpretive Summary: We studied the patterns of root decomposition of the sub-shrub snakeweed, the annual desert marigold and the grasses black grama, fluff grass and vine mesquite. We used several locations on nitrogen fertilized and unfertilized transects on a Chihuahuan Desert watershed. Soil fertility had little effect on root decomposition. Early in the decomposition process the mass of roots declined rapidly but this was followed by a long period of slow root mass reduction. Decomposition was highest for roots of desert marigold and overall rates were slowest in the dry lake bed. Root chemical components that dissolve in water and those that do not dissolve in water both reduced over time, but the concentration of lignin increased.

Technical Abstract: We studied the spatial and temporal patterns of decomposition of roots of a desert sub-shrub, a herbaceous annual and four species of perennial grasses at several locations on nitrogen fertilized and unfertilized transects on a Chihuahuan Desert watershed for 3.5 years. There were few significant differences between the decomposition rates of roots on the NH4NO3 fertilized and unfertilized transects. Decomposition of all roots followe a two-phase pattern: early rapid mass loss followed by a long period of low mass loss. Rates of decomposition were negatively correlated with the initial lignin content of the roots (r=0.90). Mass loss rates of the roots of the herbaceous annual Baileya multiradiata were significantly higher than those of the grasses and the shrub, probably as a result of subterranean termites feeding on B. multiradiata root material. The only location where mass loss rates were significantly different was the dry lake bed, where mass loss rates were lower than those recorded on the uppe watershed. The spatial differences in mass loss rates in the dry lake were attributable to the high clay content of the soils, which reduced water availability and to the absence of termites. Non-polar substances in decomposing roots decreased rapidly during the first year, then decreased at a low but fairly constant rate. Water-soluble compounds decreased rapidly (50-60% of initial concentration) during the first 3-6 months. Lignin concentrations of roots of perennial grasses were higher than those of herbaceous annual plants and woody shrubs. Lignin concentrations increased in all species during decomposition. The chemical changes in decomposing roots followed the patterns described for decomposing litter in mesic environments.

Last Modified: 11/27/2014
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