In most temperate forest, nitrogen (N) is considered a limiting factor. This becomes important in extreme environments, as Nothofagus antarctica forests, where the antecedents are scarce. Thinning practices in N. antarctica forests for silvopastoral uses may modify the soil N dynamics. Therefore, the objective of this work was to evaluate the temporal variation of soil N in these ecosystems. The mineral extractable soil N, net nitrification and net N mineralization were evaluated under different crown cover and two site quality stands. The mineral N extractable (NH 4 ? -N ? NO 3 --N) was measured periodically. Net nitrification and net N mineralization were estimated through the technique of incubation of intact samples with tubes. The total mineral extractable N concentration varied between crown cover and dates, with no differences among site classes. The lowest and highest values were found in the minimal and intermediate crown cover, respectively. In the higher site quality stand, the annual net N mineralization was lower in the minimal crown cover reaching 11 kg N ha -1 year -1 , and higher in the maximal crown cover (54 kg N ha -1 year -1 ). In the lower site quality stand there was no differences among crown cover. The same pattern was found for net nitrification. Thinning practices for silvopastoral use of these forests, keeping intermediate crown cover values, did not affect both N mineralization and nitrification. However, the results suggest that total trees removal from the ecosystem may decrease N mineralization and nitrification.

To examine whether the critical leaf N/P ratios (of 14, 16) are valid to test nutrient limitation in the context of semi‐arid sandy grasslands, an experiment was conducted on a Keerqin sandy grassland in North‐east China to investigate the responses of plant biomass and nutrient concentrations to fertilization. Plant biomass production and leaf nutrient concentrations were measured after five consecutive years of fertilization with N (20 g N m−2 year−1) and/or P (10 g P2O5 m−2 year−1). Nitrogen fertilization increased the shoot biomass by twofold and consequently the shoot/root ratio, whereas P fertilization had little effect on either shoot biomass or shoot/root ratio. Leaf N/P ratio varied among species with an average of 5·6 in the control, while the mean leaf N/P ratio (7·5) under the N fertilization treatment remained below the threshold of 14. Our results suggest that the critical N/P ratio (14, 16) is not applicable as a test for nutrient limitations in the context of semi‐arid, sandy grassland.