Landscape and microenvironmental conditions influence over regeneration dynamics in old-growth Nothofagus betuloides Southern Patagonian forests

Abstract

Old-growth forests present a mosaic of different conditions resulting from the natural forest structure of the stands. Nothofagus betuloides forests have high spatial variability in regeneration without a clear correlation with overstory, and could be related to location of the stands in the landscape. The objective was to evaluate the influence of macro- and micro-variables over regeneration dynamics in old-growth N. betuloides forests, considering the effect of landscape (altitude and influence of the sea) and microenvironment conditions in the forest floor (closeness to trees, pits, understory cover type and bare soil). A total of four sites and 24 stands were sampled including forest structure, regeneration, understory cover and microclimate variables. Macro- (landscape) and micro- (microenvironment conditions in the forest floor) variables influenced over regeneration dynamics. Natural regeneration values (0.17 million ha -1 in the drier site vs. >4.52 million ha -1 in the other sites) not greatly depended on forest structure variables, but they were related to soil moisture (14% vs. 29-36% volumetric soil water content). Microenvironment conditions in the forest floor determined the recruitment as well as regeneration density, age and distribution of seedlings, whereas different soil moisture were related to each microenvironment type, generating positive (bare soil, ferns and mosses growing in turfs) or negative (mosses growing in mats, pits and proximity of the overstory trees) effects over regeneration, according to the soil moisture levels. These findings can be used to understand the functional integrity of the old-growth forest ecosystems and to propose silvicultural prescriptions to ensure regeneration recruitment and maximize growth potential in N. betuloides forests.