Design of variable retention harvesting and monitoring program in old growth Nothofagus pumilio forests of South Patagonia, Argentina.

G MARTÍNEZ PASTUR; P PERI; MV LENCINAS; A MORETTO; JM CELLINI; R SOLER ESTEBAN

Hobart, Tasmania (Australia)

Conferencia; Old Forests: New management; 2008

Nothofagus pumilio forests cover 483.700 hectares, and are located in public and private lands. Old-growth forests are harvested to satisfy sawmill industry. Currently, there is a lack in long-term forest policies, but recently sustainable management has been legally declared as an objective. Despite this, private land owners and companies are interested in the long-term sustainability, mainly to accomplish forest certification demands (e.g. FSC). For this, impacts of traditional forestry (shelterwood cuts) were analyzed (overstory, regeneration, plants, birds, insects and mammals). Remnant overstory (30 m2.ha-1) lost 50% basal area during the first years after harvesting due to machine damage. However, regeneration was successfully established after ten years (168.000 plants.ha-1 with 38 cm height). Diversity increased after harvesting, but insects abruptly decreased with one morpho-species lost every 11 years. In a second study, species assemblage at landscape level was analyzed. Unproductive associated environments (N. antarctica forests, edge with grasslands, stream-sides, wetlands) included most of timber forest diversity. However, many insects (e.g. coleopterons, flies) were only found in primary old-growth timber forests. For these, it was necessary to develop a new conservation strategy to assure biodiversity conservation. Variable retention harvesting with aggregated (30% timber forests using 30 m radius circular patches) and dispersed retention (15 m2.ha-1) was proposed. Aggregated retention assured to maintain old-growth forest species assemblage (density or abundance) as well as species richness (up to 80% of insects) during the first years after harvesting. A long term monitoring program based on economic (yield in harvesting and sawmill), forest (overstory, flowering and seeding cycles, regeneration dynamics), abiotic (climate, soil properties, nutrient cycling) and biotic (understory species dynamics, habitat quality indicators) variables were designed to monitor variable retention harvesting design. This system is actually applied at industrial scale in private and public lands combining ecological, social and economical demands.