Soil invertebrate and microbial activity rehabilitation by compost application after road construction and volcanic disturbance

Abstract

Topsoil and plants had been removed for the construction of the “De los Siete Lagos” road when the June 2011 Puyehue–Cordón Caulle Complex volcanic eruption deposited 30 cm of tephra. Our objective was to study the active rehabilitation of substrate on roadsides simultaneously affected by road construction and volcanic eruption by compost addition. We studied two biological communities frequently forgotten by rehabilitation measures: invertebrates (density, richness) and microorganisms (enzymatic activities); both in the surface organic matter created by compost addition and the tephra substrate. In December 2012, we installed control, biosolids compost (BC) and municipal waste compost (MC) plots on roadside exclosures. Forest reference sites were also studied. Samplings were performed in spring 2013 and summer 2014. No surface organic matter was found in control plots, and no invertebrates were detected in the tephra layer of control plots in both samplings. BC and MC promoted the formation of a surface organic matter layer that harbored invertebrate and enzymatic activity in both sampling seasons. There were no significant differences in invertebrate density among BC, MC, and forest both in the surface organic matter and the tephra substrate. However, BC and MC invertebrate communities, dominated by springtails, did not resemble the forest community, where oribatids were the most common taxa. Statistically significant differences in total (surface organic matter + tephra substrate) microbial activities indicated a treatment order of forest > BC ≥ MC > control for enzymes related with the mineralization of nitrogen (leucine-aminopeptidase) and phosphorus (acid phosphomonoesterase).