Biological legacies promote succession and soil development on tephra from the Puyehue-Cordon Caulle eruption (2011)

Abstract

Volcanic deposits have frequently been studied from a successional point of view, but the main focus has been on vegetation dynamics, and less frequently on the development of invertebrate and microbial communities and soil properties. Biological legacies, understood as living organisms, seeds, organic debris and biologically derived patterns in soils and understories, are important in succession, and may also influence soil development on young volcanic deposits. The volcanic eruption of the Chilean Puyehue–Cordón Caulle complex (Northern Patagonia) in June 2011 deposited tephra in southern Argentina. Sandy tephra up to 30 cm deep was deposited in the De los Siete Lagos road in Nahuel Huapi and Lanín National Parks, where a road under construction had exposed sub-soil lacking vegetation, while adjacent forest supported a canopy of Nothofagus dombeyi with Chusquea culeou in the understory. This situation provided a unique opportunity to study soil development and succession on nearby young volcanic deposits with different biological legacies, considering several biological communities. Our hypothesis is that 29 months after the eruption the tephra in the forest would have higher organic C, total N, available P and biological activity than the tephra deposited on the roadside. Plant cover and species richness, invertebrate abundance and richness, as well as substrate respiration, N mineralization and enzymatic activities were highest in the forest. In addition, organic carbon and nutrient incorporation rates in the forest were twice those in the roadside substrate. Nevertheless, two and a half years after the eruption, most variables remained an order of magnitude lower than values expected for temperate forest soils. Surviving canopy and understory play a key role in ecosystem recovery after tephra deposition, providing seeds and organic matter and establishing conditions appropriate for plants, invertebrates, and microorganisms that would in turn accelerate soil development.