WATER-EXTRACTABLE ORGANIC-MATTER FROM PLANT LITTER AND SOIL OF ROUGH FESCUE GRASSLAND

Little is known about the chemical composition of throughfall, or the water that falls through, and drips from, the grass canopy of Rough Fescue Grassland during the grazing season. Water-extractable C, N, organic acids, and monosaccharides from litter and from soil in the upper 2 cm of the Ah horizon collected at monthly intervals in 1988 were assessed at Stavely, Alberta. Rough fescue (Festuca campestris Rydb.) grasslands were stocked at either light (1.2 AUM/ha) or very heavy (4.8 AUM/ha) fixed rates for 39 years or were ungrazed in exclosures located within each field for an equal period of time. At the high grazing intensity, the soil and litter N was less water-extractable. The C/N ratios of the water-extractable organic matter from litter and soil averaged 11.2 and 2.3, respectively. Soil monosaccharides were essentially not water-extractable. The quality of the litter as reflected by the water-extractable constituents often differed over the season between fields. Observations at regular time intervals are essential. The effect of the quality of leachates of litter on soil was not predictable. The 3 major long-chain fatty acids identified, palmitic, stearic, and arachidic acids, from soil in grasslands that are in good condition because of the low grazing pressure, could well contribute to the resistance of those grasslands to the encroachment of invading species.