Submitted to: American Water Resources Association Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/27/1998
Publication Date: N/A
Interpretive Summary: Prescribed burning of rangelands is being used as a management tool to control undesirable vegetation and promote desirable vegetation. With the burn removing vegetation, there is a potential for increased surface water runoff, erosion, and loss of plant nutrients to the ecosystem. Prescribed burns were found to significantly increase surface runoff, erosion, and nutrient loss with time after the burn when compared to unburned areas. The soil was found to interact with the vegetation to be the most important factor controlling the surface runoff, erosion, and nutrient loss. Other factors such as different seasons and years were found to influence the runoff, erosion, and nutrient loss irrespective of a burn. The amount of plant nutrient lost in the increased runoff and erosion was determined to be very small when measured against the total amount contained in the soil. Therefore, many years of increased nutrient loss from burns could occur before there would be a significant loss to the ecosystem. These findings greatly increase our understanding of how burns influence a rangeland ecosystems and provide land managers important information to use in their management decisions.
Technical Abstract: Prescribed burning may substantially increase the potential for surface runoff, erosion, and nutrient loss resulting in a change in the ecosystem. Burning effects on surface runoff, sediment yield, and nutrient dynamics were evaluated with a rainfall simulator following fall and spring burns at two different soil and vegetation type locations. Soil, aboveground biomass, and surface runoff samples were analyzed for nitrogen, phosphorus and potassium to determine the nutrient pool sizes. Rainfall simulations were conducted after prescribed burns and one year later following a repeated burn and compared with paired unburned areas. The complete study was replicated in a second year. After one year and the repeated burn surface runoff, sediment yield, and nutrient loss became significantly greater than the unburned treatment. Surface runoff, sediment yield, and nutrient loss were controlled primarily by the soils and the soils interacting with the vegetation. Significant season and year effects were found for runoff, sediment yield, and nutrient loss irrespective of the burn treatment. The nutrient dynamics showed the magnitude of the nutrient pools to be soil biomass surface runoff losses, implying there could be many burns before a significant amount of nutrient would be depleted from the soil, potentially changing the ecosystem. These results are important for understanding fire as a management tool and how fire impacts rangeland water resources.