PARENT SESSION
Oral Session #60: Agroecology- Sustainable Agriculture.
Presiding: R. Bohanan
Wednesday, August 7. 8:00 AM to 11:30 AM. Mesquite Room, Radisson.
Wetland/cropland rotational management: a strategy to sustain diverse wetlands and agriculture?
Shennan, Carol*,1, Los Huertos, Marc1, 1 University of California, Santa Cruz, Santa Cruz, CA
ABSTRACT- Wetland/cropland rotational management is proposed to improve wetland diversity while sustaining agriculture in the Tulelake basin (CA). The Tule Lake National Wildlife Refuge currently encompasses wetlands, open water and irrigated croplands, but faces declining bird populations, limited wetland diversity due to water level stabilization, poor water quality, and declining soil quality and increased pest pressure in cropped areas. Wetland/cropland rotational management is based upon two assumptions: crop production could function as a disturbance to enable diverse wetlands to be established upon re-flooding, and rotation out of crop production would break pest cycles and improve soil quality for subsequent crop production. A mosaic landscape would result with diverse wetland units interspersed with crop production areas. In a pilot study we examined water quality, soil fertility and vegetation following conversion of cropland into wetlands, and crop production following conversion of wetlands back into cropland. Vegetation shifted from agricultural weeds to "moist soil plants" within 2-3 years after conversion, and exchangeable soil P increased. Surface water nutrient concentrations varied over time and space. Peaks in ammonia, nitrate and ortho-P occurred and localized interactions among water depth, temperature, algal growth decomposition may dominate nutrient fluctuations. Drainage from seasonal wetlands during summer draw down had low dissolved oxygen and temperature, and elevated ortho-P and ammonia. High canal flows during the draw down could minimize adverse water quality impacts from seasonal marshes. The feasibility and desirability of wetland/cropland rotational management will be examined.
KEY WORDS: wetlands, agriculture, water quality, landscape ecology