As ecosystem engineers, North American beavers (Castor canadensis) change many environmental conditions in watersheds, felling trees, damming streams, and flooding riparian zones. In Tierra del Fuego, where beavers were introduced in 1946, these alterations have produced meadows that appear to be long-term alternate stable states, lacking signs of resilience and natural forest regeneration. The aim of this work was to determine the abiotic and biotic factors that affect native tree seedling success in abandoned beaver meadows in Nothofagus pumilio forests. Environmental conditions including light, soil moisture, herbaceous plant community composition, and reinvasion potential were measured in areas impacted by beavers and in unimpacted old-growth forests. Additionally, we monitored the survival and success of N. pumilio seedlings transplanted in plots where meadow vegetation was cleared. Tree seedlings showed little growth, and survival varied by type of beaver impact. While survival was high and similar to unimpacted sites in zones cut but not flooded by beavers, it was significantly lower in meadow zones that were previously flooded and cut, compared to old-growth forests. We found that the reinvasion of herbaceous plants into transplantation study plots was negatively related to tree seedling survival, and herbaceous (monocot) plant cover itself was related to beaver-created gradients in soil moisture and light availability. Overall, these abiotic changes modified the meadow's plant community and enhanced herbaceous vegetation cover, particularly monocots and exotics, thus hindering transplanted seedling survival.

Bioindicators could act as early warning indicators of environmental changes, ecosystem stress or taxonomic diversity. Pseudoscorpions have rarely been used as bioindicators, due to lack of information about their ecology, habitat selection, niche preferences and requirements, especially in southern Nothofagus forests. We studied the distribution and abundance of a pseudoscorpion species, Neochelanops michaelseni (Simon 1902), in different vegetation types (Nothofagus antarctica and N. pumilio forests, grasslands and peatlands) and examined how this species responded to different forest uses (harvesting and silvopastoral management), to explore its utility as a bioindicator. The study was conducted on longterm plots located at two ranches in Tierra del Fuego, using pit-fall traps during one summer. Neochelanops michaelseni abundance was higher in Nothofagus forests than in open ecosystems, which could be attributed to their affinity for litter and coarse woody debris. In N. pumilio forests, the pseudoscorpions were sensitive to harvesting, with similar abundances in harvested forests (aggregated and dispersed retentions) and grasslands. In N. antarctica forests, differences were not detected among unmanaged and silvopastoral managed forests, probably due to higher understory plant growth, and lesser diminishing of litter and debris by thinning than by harvesting. We conclude that the pseudoscorpion, N. michaelseni, can be a good bioindicator for ecosystem conservation and for evaluating recovery rate in the ecological conditions of impacted Nothofagus forests, and that management practice intensities should be regulated to create more suitable habitats for pseudoscorpion diversity conservation.

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 microvariables 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 71 in the drier site vs. 44.52 million ha 71 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.