Summary Fosetyl‐Al and metalaxyl, the most commonly used systemic fungicides against Phytophthora, were evaluated for their efficacy to control Phytophthora austrocedri, the pathogen that causes a serious disease at the Austrocedrus chilensis forests in Patagonia. The effect of the chemicals on pathogen development in vitro and in planta was analysed. Both chemicals were shown to protect plants from the pathogen. In vitro assays showed that asexual reproduction was sensitive to both chemicals. However, mycelial growth and sexual reproduction, which were clearly sensitive to metalaxyl, were sensitive only to high concentrations of fosetyl‐Al. Fosetyl‐Al and metalaxyl had almost the same efficacy when applied preventively by soil drench to seedlings. This difference between in vitro and in planta results can be attributed to the dual action of fosetyl‐Al, not only inhibiting the pathogen but also stimulating host defence. In adult trees, preventive and curative treatments were tested, but only the fosetyl‐Al preventive treatment was effective in the assayed conditions. Interestingly, seedlings pretreated with both fungicides were less susceptible to the effectors secreted by the pathogen. Our results indicate that fosetyl‐Al and metalaxyl provide some resistance to the plant besides the fungistatic direct action on the pathogen. Further studies to elucidate a possible resistance‐inducing activity of these chemicals and the mechanisms involved are underway.

In managed forests, biodiversity conservation is crucial for the sustainable use of ecosystem resources. In the Patagonian-Andes forests of Argentina, lenga (Nothofagus pumilio) is the most important native tree because of its ecological functions and economic importance as a timber provider. In this study, we determined how the shelterwood-cut system impacts understory vegetation attributes in three sites representing typical lenga forests of central Andean-Patagonia. In each site, two 250-m 2 treatment plots (managed and unmanaged) were established, and canopy cover, soil temperature, and moisture were determined. Within plots in 10 randomly placed 0.25-m 2 microplots, we determined plant cover, from which we calculated diversity attributes. Canopy cover and soil moisture were higher in unmanaged treatments, whereas the reverse was true for soil temperature. The Shannon-Wiener index showed similar values (ϳ1), whereas species richness was slightly higher in unmanaged (4.8 Ϯ 0.5) than in managed treatments (3.8 Ϯ 0.3). Generally, native plants dominated the understory (ϳ40%), whereas exotic species were rare (ϳ1%). Shrub cover was higher in managed (24.1 Ϯ 4.2) than in unmanaged (9.5 Ϯ 1.7) treatments, whereas herbaceous species dominated unmanaged forests. These results confirm that the shelterwood-cut system may be used for diversity conservation in Patagonian lenga forests.

Fungal diversity, woody debris, and wood decomposition were assessed in Nothofagus pumilio forests with and without forest management. A plot in a managed forest (MF) and a plot in an unmanaged control forest (C) were established in three sites in Chubut, Argentina. On each plot, forest structure, volume of woody debris, temperature, and humidity were recorded. Basidiomata of aphyllophoroid fungi were recorded in the fall and spring for 2 years. A decomposition assay with branches and twigs in two decay classes (DC) was established, and mass loss was measured after 3 and 2 years of field incubation respectively. To evaluate fungal diversity and mass loss within MF and C, generalized linear mixed-effects models (GLMM) were performed. Neither richness nor abundance differed between treatments, and community composition was similar. Only branches in DC2 showed greater mass loss in MF than in C. The volume of CWD was greater in MF and had a positive effect on fungal richness. A few aphyllophoroid species showed significant differences in abundance between treatments. Forest management in the conditions evaluated did not generate evident changes in fungal diversity, nor in wood decomposition. However, the differences observed in mass loss of DC2 could indicate that there were some factors operating in the past, that are no longer seen in the present, which may have accelerated decomposition. This highlights the need for studies evaluating changes in canopy cover, microclimate and fungal community, including potential key species, over a period starting just after the forest management.