Plant community assembly on volcanic debris avalanche deposits around the world

Volcanic debris avalanches are among the largest and most severe disturbances known. Therefore, studying processes of ecosystem formation on the deposits emplaced by these landslides provides insights into the patterns of community assembly after the most severe disruptions. In this review we synthesize findings of 60 vegetation studies from 15 volcanic debris avalanche deposits. One of the most impactful drivers of the speed with which communities reestablish is the climatic region in which the debris avalanche occurs. The fastest recovery occurs in the tropics and the slowest in the boreal latitudes. The existence of biotic legacies, or remnant soils or biota from the previous communities accelerates community establishment, and these legacies are found more frequently on smaller debris avalanche deposits. Where these legacies exist, recovery proceeds many times more rapidly than in primary successional areas of the deposits. Similar patterns across mountains are observed in the species guilds that arrive and become established on the deposits with nitrogen fixers and early seral species doing particularly well. Complete recovery, meaning that communities match those of surrounding undisturbed areas, from this extreme class of disturbance takes a very long time, decades in the tropics and centuries to millennia at higher latitudes. Secondary disturbances are frequent and often reshape the direction of community development. Understanding of community development on debris avalanches would be greatly expanded if continuous time series over decadal to millennial scales were available on more disturbances. This could be achieved through repeat monitoring of permanent plots, remote sensing, or use of pollen core analysis. Such studies may enable inference about whether long-lasting community differences from surrounding areas are due to alternative stable states or simply the slow turnover of long-lived species on volcanic debris avalanches. Further study of these topics will foster better management of human disturbed landscapes, such as those from large-scale mining.