Removal of native bamboo promotes natural regeneration in degraded temperate rainforests in North-Patagonia, Chile

Abstract

Forest degradation often permits the proliferation of dense understories that inhibit the development of natural regeneration over long periods. In South American temperate rainforests, native Chusquea bamboo species become unusually competitive after logging and invade forest understories, creating dense and continuous thickets under remnant canopy tree species. In this study, we aim to evaluate how natural regeneration of native species develops after removal of the Chusquea bamboo understory and to define which microsite conditions can facilitate species' early development. To achieve this, we removed the Chusquea understory in 45 experimental units, systematically established in a 4 ha experiment located in degraded temperate forests on Chiloé Island, North-Patagonia, Chile. We evaluated microsite conditions and monitored the natural regeneration response during 5 years. After 5 years, greater than 81% of the remnant canopy tree species were regenerating, mostly from seed, and there was a 55.5% increase in total natural regeneration (p < 0.05; increase >1 individuals/m2 yr−1), with species like Amomyrtus spp. increasing abundance by greater than 121%. Total natural regeneration presented positive significant correlations (p < 0.01) with the depth of the water table (rs: 0.40), soil carbon (rs: 0.44), nitrogen (rs. 0.41), and organic matter (rs: 0.44). We conclude that removing the Chusquea understory assists the natural recovery of degraded temperate rainforests by facilitating additional recruitment of early, mid, and late successional tree species. In this process, early and mid-successional tree species are more specific in their microsite preferences than successionally late ones.