Appendix L. Riparian Ecology and Fire Management

A. Introduction: General Concepts of Disturbance Disturbance has been defined as "any relatively discrete event that disrupts ecosystem, community, or population structure and changes resources, substrate availability, or the physical environment" (P ickett and W hite 1985). The size, intensity, frequency, and timing of a d isturbance all influence ecosystem structure and function. Generally, natural disturbances maintain high diversity of habitat patches in the landscape and thus maintain species diversity. Many plant and animal species depend upon periodic disturbance. Different types of disturbances be they fire , flood, or landslide produce different effects on ecosystems. Plant species have evolved suites of traits that adapt them to the particular types and patterns of disturbance that they routinely experience. “Novel” disturbances, new combinations of disturbances, or changes in the intensity, timing, duration, and/or scale of a disturbance all can alter ecosystem structure and function outside the range of conditions to which the species are adapted (Paine et al. 1998). For many of our Southwestern riparian ecosystems, due largely to land and water management practices, fires have replaced floods as the primary disturbance factor. This change has had adverse consequences for many native species.