Does a Native Grass (Imperata BrasiliensisTrin.) Limit Tropical Forest Restoration Like an Alien Grass (Melinis MinutifloraP. Beauv.)?

Abstract

Abandoned pastures are increasingly targeted for forest restoration in the neotropics. However, the dominance of such areas by fodder grasses imposes a challenge for efficient and low cost control. Therefore, we questioned whether alien and native grasses equally affect: (1) natural regeneration; (2) natural regeneration under artificial perches; and (3) planted seedling development. Our study was carried out in an abandoned pasture in southeastern Brazil, in the Atlantic Forest biome. For (1) we installed plots in grass patches of Melinis minutiflora (molasse grass, an alien grass) and Imperata brasiliensis (satintail, a native grass that occurs in degraded areas); for (2) we installed plots under perches in alien and native grass patches; and for (3) we compared overall planted seedling mortality and development of four tree species in alien and native grass patches. Density and diversity of woody species in natural regeneration and under perches were similar for invasive and native grass patches. However, species composition differed between alien and native grass patches (Ellenberg similarity of 28% for perches and 35% for natural regeneration in different grass patches). Seedling mortality was similar for both alien and native grasses. Except for two tree species, development was similar for both native and alien grass patches. Our results indicate that the biological barriers imposed by a given grass species for forest succession and restoration must not be estimated based only on the species' origin.