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Photosynthetic photon Xux density (PPFD) during the growing season and regeneration growth (height and base stem diameter) were investigated in two natural stands in the Patagonian region of Chile, one without silvicultural management and another with a regenerative felling under a shelterwood system. PPFD was measured by means of Wfteen sensors (quantum Li-190SA) installed in each stand and distributed within three canopy openness grades. Four regeneration plots (1 m 2 ) were established around each sensor. In each of the plots, the height and base diameter of ten labelled plants within the upper regeneration layer were measured in the growing seasons 2001-2002 and 2002-2003. In the stand with regeneration felling total PPFD in the growing season was 2.5-2.9 times higher than in the stand without intervention. In both stands, total PPFD in the growing season increased by about 420 mmol/m 2 when the relative canopy, which was in the range between 30 and 70%, was reduced by 10%. An identical behaviour was observed for the height and base stem diameter increases reXecting a clear eVect of intervention and canopy coverage on the magnitude of PPFD received by the regeneration and its development.

Chemical properties of 42 Chilean forest soil profiles, corresponding to 207 samples between 33° and 53° South latitude, are discussed. Water pH and pH-KCl in surface mineral horizons varied from 3.1 to 6.6 and from 3.2 to 5.9 respectively. The most acidic soils were located in the southern latitudes. Humus was accumulated on soil surface and decreased markedly with depth. C/N relationships indicated an increase of humus evolution with profile depth. Fulvic acid/humic acid relationships increased with depth. CEC, exchangeable cations, and fertility were strongly dominated by organic colloids. Al and Fe forms indicated a descending movement or Al-and Fe-organic complexes in some soils.

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