ABSTRACT
Bottom-up disturbances describe perturbations that are endogenous to ecosystems, such as gap-fall dynamics and pathogen outbreaks, including any response and recovery to that event. In this chapter, we describe bottom-up or endogenous disturbances and highlight their key drivers. As bottom-up disturbances originate within an ecosystem (for example, a naturally occurring fire, the death of a tree creating a canopy gap, or an imbalance in the population of a pathogen driving high mortality in a plant species), the response processes are typically represented by secondary successions. Even in the case of large-extent disturbance, such as wildfires in the Brazilian cerrado, where vast areas of tropical savannah can be burned, soils and seed bank are retained, and the ecosystem recovers rapidly. Bottom-up disturbance processes are changing globally in response to climate change and anthropic dispersal of myriad taxa; as such, interactions are changing and disturbance events increasing in magnitude and intensity. While we identify processes distinct to intrinsic events within ecosystems, separating top-down and bottom-up processes is challenging, as they are subtle and scale-dependent and frequently interact; this renders a dichotomous differentiation between the two categories difficult or unhelpful in many cases.
