Restoration of subtropical grasslands degraded by non-native pine plantations: effects of litter removal and hay transfer

Pinus plantations create strong ecological legacies that persist after their removal. We evaluated the effectiveness of pine litter removal (manually or through controlled burns) and hay application for the restoration of South Brazilian coastal grasslands degraded by pine plantations. We installed the experiment 1 year after cutting trees and sampled the vegetation 3 months, 1 year, and 2 years after initiating the experiment. We used generalized linear mixed model to assess treatment effects on plant cover, richness, and pine reestablishment. We used nonmetric multidimensional scaling and indicator species analysis to evaluate changes in species composition over time and in the association of individual species with treatments and reference area. Species richness and vegetation cover did not differ between manual and burn treatments but were higher than in the control. Hay application enhanced vegetation cover by the end of the experiment in all treatments. Hay application enhanced richness initially, but after 2 years the effect persisted only in the burn treatment. Burned plots showed less pine establishment than plots with manual litter removal. Hay-addition plots contained indicator species present in the reference area. Our results suggest that passive restoration (i.e. only cutting of pine) is not sufficient to restore grasslands altered by afforestation, as residual pine litter constrains the reestablishment of native vegetation. In addition to the benefits of litter removal, our results indicate that hay transfer can overcome seed limitation of grassland species and burning can reduce recolonization by pine.