Patterns of Decomposition and Nutrient Cycling Across a Volcanic Disturbance Gradient: A Case Study Using Rodent Carcasses

Abstract

The processes of decomposition and nutrient cycling of organic substances (plant leaf litter, woody stems, roots, and animal carcasses) are critical to the functioning of ecosystems (Swift et al. 1979; Cadisch and Giller 1997). The breakdown of dead plants and animals by scavenging animals, fungi, and bacteria is the first step in the recycling of important nutrients and is necessary for maintaining the productivity potential of soil (Lal et al. 1998; Stevenson and Cole 1999). In the case of the extremely disturbed forest ecosystem of Mount St. Helens, decomposition processes, acting on the plants and animals killed in the eruption, contributed to the early stages of soil building in landscapes covered in tephra. As plant and animal populations became reestablished after the eruption, individuals of these surviving and colonizing populations eventually died and decomposed, thereby contributing additional organic and nutrient resources to the soils. The development of soil organic fractions through decomposition in an otherwise mineral substrate (pumice and tephra) has undoubtedly facilitated the continued successional development of floral and faunal communities in the disturbed zones of the volcano and will certainly continue to do so in the future.