Composts promote short‐term rehabilitation in a Patagonian roadside affected by tephra deposition

Composts are effective to promote rehabilitation after drastic disturbance. The eruption of Puyehue–Cordón Caulle complex in 2011 deposited 25–30 cm of tephra in the Argentinean area known as “De los Siete Lagos,” where soil and vegetation had been removed from many sites for the construction of National Route 40 between 2005 and 2015. Roadside revegetation is limited by the drastic disturbance, but also by depth and low nutrient content of the tephra. Our objective was to study substrate and plant rehabilitation after the application of different composts (biosolids compost, BC, and municipal waste compost, MC) and seeding (Trifolium repens and Poa domingensis). Eighteen months after the eruption the following treatments were installed: control, BC and MC, nonseeded and seeded (n = 3). Composts were applied at 60 Mg/ha and seeds were sowed at 2 g/m². Physicochemical substrate properties (moisture, pH, electrical conductivity [EC]), nutrient content (organic C, available P, total N), and microbial activity (respiration, N mineralization, enzymatic activities) were assessed 15 months after the start of the experiment. Plant cover and biomass were estimated three times during summer–early autumn. Seeding had no effect on roadside revegetation. Composts significantly promoted substrate rehabilitation, as BC had a positive effect on moisture, nutrient content (total N, available P, N mineralization), and microbial activity (leucine‐aminopeptidase and acid phosphomonoesterase activities), while MC significantly increased EC and pH. Finally, composts significantly increased plant cover and biomass, but the community was dominated by exotics favored by harsh environmental conditions and absence of a native seed bank.