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 Fe scue Grassland during the grazing season. Water-extractable C, N, orga nic acids, and monosaccharides from litter and from soil in the upper 2 cm of the Ah horizon collected at monthly intervals in 1988 were ass essed at Stavely, Alberta. Rough fescue (Festuca campestris Rydb.) gra sslands were stocked at either light (1.2 AUM/ha) or very heavy (4.8 A UM/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 in tensity, the soil and litter N was less water-extractable. The C/N rat ios of the water-extractable organic matter from litter and soil avera ged 11.2 and 2.3, respectively. Soil monosaccharides were essentially not water-extractable. The quality of the litter as reflected by the w ater-extractable constituents often differed over the season between f ields. Observations at regular time intervals are essential. The effec t of the quality of leachates of litter on soil was not predictable. T he 3 major long-chain fatty acids identified, palmitic, stearic, and a rachidic acids, from soil in grasslands that are in good condition bec ause of the low grazing pressure, could well contribute to the resista nce of those grasslands to the encroachment of invading species.