Introduction

In any one year, approximately 60 volcanoes erupt on the Earth. Even though about 80% of these eruptions occur under the oceans, the terrestrial volcanic events are common enough to have major impacts on nearby vegetation, often over large areas (e.g., Bilderback, 1987). Volcanic activity both destroys or modifies existing vegetation and creates new geological substrates upon which vegetation can re-establish. The types of plants surviving and recovering after volcanic activity largely depend upon the type of activity that takes place, the nutrient content of material ejected or moved by the volcano, the distance from the volcanic activity, and the types of vegetation propagules that survive in place or are transported from adjacent areas. The resulting changes in the vegetation abundance and patterning can have dramatic effects on the social and economic conditions of the humans in the areas surrounding volcanoes.

Impacts of volcanoes on existing flora

Physical impacts

Primary impacts

The primary impacts of volcanic activity on vegetation correlate to the specific type of volcanic activity (Table 8.2). In associating impacts with types of volcanic activity, we refer to the many studies on vegetation survival and reestablishment that have been conducted on volcanoes (Table 8.1). We divide the volcanic activities into six categories: lava formation, pyroclastic flows, debris avalanches, mudflows, tephra and ash depositions, and blowdowns.