Silvopastoral use of Nothofagus antarctica in Southern Patagonian forests, influence over net nitrogen soil mineralization

BAHAMONDE H.; PERI P.L.; ALAVAREZ R.; BARNEIX A.; MORETTO A.; MARTÍNEZ PASTUR G.

AGROFORESTRY SYSTEMS

SPRINGER

Lugar: Berlin; Año: 2013 vol. 87 p. 259 - 271

0167-4366

In most temperate forest, nitrogen (N) is considered a limiting factor. This would be more 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 systems. 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 (NH4+-N + NO3--N) was measured periodically. Similarly, 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 class. 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 significant lower in the minimal crown cover reaching 11 kg N ha-1 yr-1, whilst the average in the others crown cover was 63 kg N ha-1 yr-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, would affect neither N mineralization nor nitrification. Nevertheless, the results suggest that high removal of trees may decrease N mineralization and nitrification in higher quality sites.