Synergies and trade-offs of variable retention harvesting in Nothofagus pumilio Patagonian forests: Overview after 18 years of implementation

G MARTÍNEZ PASTUR; MD BARRERA; JM CELLINI; MV LENCINAS; PL PERI

Bucarest

Conferencia; International Scientific Conference Forest Science for a Sustainable Forestry and Human Wellbeing in a Changing World; 2018

National Institute for Research and Development in Forestry

Forests provide several ecosystem services, but traditional its management focus only in provision disregarding other services and conservation. Variable retention harvesting (VR) was proposed to maintain some characteristics of primary forests and diversity in the managed areas (Martínez Pastur et al., 2009). VR applied in Nothofagus pumilio forests in Southern Patagonia (Argentina) combines two types of retention: aggregates of original forest (AR) (60 m diameter, one per hectare) and dispersed single trees (DR) in the harvested areas (10-15 m²/ha basal area). The proposal starting with a permanent plot (50 ha) in San Justo ranch, and continued to date in more than 3000 ha. Different studies were conducted with this management umbrella including: (i) yield, (ii) economics, (iii) microclimate, (iv) natural cycles, (v) forest stability, (vi) forest dynamics, and (v) biodiversity conservation (e.g. birds, plants, invertebrates, fungi, mammals). This study assesses the assumption that VR maintains mature forest conditions after harvesting in the aggregates, and reduces the negative effects or harvesting with an economic sustainability. We synthesizing 18 years of research in different harvested with VR and without management (control areas) trough univariate and multivariate methods, as well as meta-analyses. We found that aggregates had no effect on microenvironmental variables and forest structure, but increased the values of forest reproduction. Dispersed retention did not affect microclimate and forest reproduction, but negatively affected forest structure. Species richness and abundance of native plants were significantly increased in the aggregates and in dispersed retention richness of native plants increased while their abundance slightly decreased. Alien plants significantly increased in both treatments, with particularly strong effects in the dispersed retention. Insect richness and abundance were hardly affected by the treatments, whereas birds were significantly increased in harvested areas. Species of primary forests were maintained in the aggregates, whereas species of neighbouring environments were positively affected by harvesting. We conclude that the ecological conditions of N. pumilio forests were influenced by VR, but direction and magnitude of the effect depend on the treatment and the kind of variable. Inside aggregates several primary forest components and conditions were maintained (Soler et al., 2015; 2016). Beside the positive synergies and the detected trade-offs with conservation, we analysed the economic feasibility of their implementation in large-scale forestry operations. The economic and yield indicators showed that there are no significant differences with traditional harvesting (e.g. shelterwood cuts), and several advantages were added to the operations (e.g. logging and yield), decreasing their implementation costs.