Tree-fall gaps and patterns of tree recruitment and growth in Andean old-growth forests in south-central Chile

Abstract

Canopy gaps have been recognized as an important process in the regeneration dynamics of Andean old-growth forests (ca. 40° S). The objectives of the study were to determine main tree-fall gap attributes and to assess tree recruitment and growth patterns in tree-fall gaps of two mid-elevation Andean old-growth forests. We measured the canopy and expanded area of each gap, and for the gap-maker species we measured its diameter at breast height (dbh), felling direction and type of treefall. In each gap, tree seedlings, saplings and bamboo culms were counted in subplots. Increment cores of potential successors were obtained to examine growth patterns. There was a larger area in canopy gaps in NF than in STF (25.8 vs. 11.9 %). Expanded gaps were on average larger in NF than in STF (547 vs. 440 m²). Most gaps were originated by wind-snap and upturned root-plates of all the major tree species (Laureliopsis philippiana, Saxegothaea conspicua and Dasyphyllum diacanthoides, and Nothofagus dombeyi in NF). The understory species Chusquea culeou was an important competitor in gaps, especially in STF where the bamboo was more effective inhibiting the recruitment of tree seedlings. The successful recruitment of shade-tolerant tree species beneath endogenous tree-fall gaps indicates that these species follow a gap-phase regeneration mode through which -after several growth releases- they can reach the main canopy. These studies could offer valuable insights for the urgently required restoration and management of Andean old-growth forests.