The Influence of Volcanic Tephra (Ash) on Ecosystems

Volcanic eruptions affect a large proportion of Earth's ecosystems, ranging from subtle dust inputs to thick deposits near the volcanoes. In this chapter, multiple influences of tephra deposition on land are investigated, using examples of recent volcanic eruptions. "Tephra" is the collective term for airborne volcanic materials, while ash is restricted to materials <2 mm in grain size. Impacts of tephra is depended on the nature of the tephra, including crystallinity, chemical composition, and grain size. The interaction between vegetation height and the deposition depth has a major influence on impacts, while surface roughness and other factors are also important. Low growing Arctic, alpine, and desert ecosystems are much more sensitive than higher vegetation and forests. Recovery time ranges from few to >1000 years. Alien species can severely interfere with ecosystem recovery. Erosion processes contribute to volcanic impacts by redistributing tephra, thus reducing tephra thicknesses in some places, but can also cause erosion rates exceeding 100,000 t km(-2) year(-1). Wind erosion of tephra affects ecosystems, agriculture, and health but can provide beneficial dust inputs afar. Thick tephra deposits have pronounced impacts on agriculture, and F toxicity is common in volcanic areas. Soils that form in parent materials dominated by volcanic ash are mostly Andisols with the colloidal fraction dominated by short range order minerals and metal humus complexes. Andisols. are often fertile soils with a high capacity to accumulate carbon. There is a need for multidisciplinary long-term research on impacts and responses to volcanic eruptions.