Acumulación de biomasa en juveniles de arbustos nativos expuestos a distintos niveles de luz asociados a esquemas de manejo forestal de coníferas exóticas

Abstract

Pinus ponderosa plantations established in the Patagonian steppe put ecosystem functions at risk if they are not properly managed. The response of shrubs to light variations caused by forest plantations and forestry interventions may influence their ecological role. In this work we evaluated the total biomass accumulation dynamics of calafate (Berberis microphylla) and mamuel choique (Adesmia volckmannii) at 20, 60 and 100% irradiance, and their response to the light increase that would occur after interventions such as thinning and harvesting. For each species we evaluated 1) the relationship between biomass and diameter at the base of the stem, 2) the biomass dynamics during two growing seasons in the three irradiance conditions, and 3) the early response to light increase in plants subjected to irradiances of 20 and 60%. In addition, 4) we compared the levels of irradiance that the proposed forest management schemes for the region would suppose with those evaluated here. For both species, biomass and diameter were linearly related and biomass accumulation was lower at 20% irradiances. Calafate showed a tendency to accumulate more biomass at 100%, and mamuel choique, at 60%, although no species showed differences between these irradiances. Whereas calafate from 20% irradiance only increased its biomass by increasing irradiance to 100%, mamuel choique did so by increasing it to 60%. These results suggest that the two species, at least in the juvenile phase, may acclimate to shade, and that mamuel choique would respond better to partial increases in light, as in the case of thinning. The response of calafate suggests that the proposed management, which irradiance levels would be lower than those evaluated here, would not be optimal for its development.