Vegetation manipulation strategies for playa lakes
Haukos, David A.
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The Playa Lakes Region of the Southern Great Plains is an important wintering area for waterfowl. The goal of this study was to develop and test management options for vegetation important to waterfowl wintering in playa lakes. Seed-bank composition was examined under 2 environmental conditions, drawdown and submerged. Seed banks of playa lakes are dominated by annuals. Seed-bank density and composition differed among 8 lakes. Plant community composition had a higher degree of similarity among lakes in the submerged treatment. Many species showed temporal emergence patterns throughout the growing season. Ability to predict playa vegetation from seed-bank composition decreased as the growing season progressed. Vegetation management in playa lakes (moist-soil management) involved the dewatering or irrigation of playas to create saturated, exposed soil. This promoted germination, growth, and seed production of moist-soil plants. The plant species targeted for management were Echinochloa crusgalli, Persicaria iapathjfolJa,- P. pensyivanica, Rum^x crispus^ and Eleocharis spp. Management created moist-soil conditions during early April, mid- to late June, and early August with maintenance of water in lakes over winter. Compared to unmanaged lakes, moist-soil managed lakes had greater above-ground standing crop and seed production and vertical structural cover. Moist-soil management of playa lakes favored Echinochloa crusgalli, Persicaria japathifolia. and £. pensylvanica: had no effect on Rumex crispus; and disfavored Eleocharis spp. Soil variables of conductivity, moisture, strength, nitrogen, and phosphorus were not affected by management of playa lakes. Wintering waterfowl were found more frequently on managed lakes. Chemical constituents of ash, soluble carbohydrates, crude protein, crude fat, hemicellulose, cellulose, lignin, and cutin-suberin were estimated in seeds from the 5 plant species listed above. Although chemical constituents differed among species, only seed of Eleocharis spp. Was undesirable because of high cutin-suberin levels and low protein and soluble carbohydrate values. Moist-soil management of playas is compatible with farming irrigation schedules and does not interrupt farming practices. Landowners are able to manage their lakes for lease hunting of waterfowl as an additional source of income Winter flooding of playa lakes without moist-soil management during the growing season is an inefficient use of valuable water.