Coleopteron species assemblage in south Patagonia: sustainable landscape management using a variable retention harvesting

LENCINAS, MV; MARTÍNEZ PASTUR, G; CELLINI, JM; CÓRDOBA, JA

Campos do Jordao, Brazil

Conferencia; Latin American IALE Conference; 2009

IALE

Introduction: South Patagonian forests present an endemic entomofauna, which was not sufficiently studied. Insect communities showed a particular species assemblage in the timber forests and their associate unproductive environments. Order Coleopterae is the most important one in Tierra del Fuego, for their richness, abundance and knowledge about its taxonomy, being feasible their use as indicator of habitat qualities. Harvesting produces a negative impact over insect diversity. For this, new harvesting proposals included different degrees and retention types in order to minimize the impacts and to improve the conservation status of the managed stands. The objective was to evaluate the epigean coleopteron species (richness and relative abundance) in primary Nothofagus pumilio forests, managed stands with a variable retention method, and associated unproductive environments, to establish similarity relationships among them.Methods: 5000 ha were selected for the sampling (54°20´ S, 67°52´ W), where six environment types were defined: primary N. pumilio unmanaged forest-PF, harvested forests through a variable retention system (aggregated-AR and dispersed retention-DR) and three associated unproductive environments (N. antarctica forests-NA, grasslands-G and peatlands-P). Variable retention included one AR of 30 m diameter per hectare of primary forests, and a DR of 10-15 m2 ha-1 basal area. 45 set composed by five pit-fall traps each was established during one week, along two consecutive years in the middle summer. Coleopterons were counted and identified (family, genera and/or species). Classification and ordination analyses were defined to establish similarity relationships among the coleopteron assemblage and the sampled environment types.Results: 985 individuals of 43 taxonomic coleopteron entities were defined, where 20 of them were identified at species level. Richness varied between 10 and 21, being lesser in P and higher in G and DR. Relative abundance varied between 99 and 226 individuals week-1, being lesser in G and higher in DR. Only one species was founded in all the environments (Trechisibus antarcticus), which was more abundant in NA and PF. Ordination analysis showed great differences between G and P, and the forest communities, which were very similar and homogeneous among them. AR was more similar with PF than the others environment types, while DR occupied an intermediate position between PF and the open environments (G and P). Classification analysis highlighted the similarity between AR and PF, as well as NA and G, while P was the most dissimilar.Discussion: Coleopteron species assemblage in south Patagonia differed among the studied environments, being the grasslands, peatlands and N. antarctica forests more similar among them than the primary N. pumilio forests. Harvesting using a variable retention system allows to improve the sustainability at landscape level. Most of the habitat quality indicators survive inside the aggregated retention, while dispersed retention sustain several adventitious species of the associated unproductive environments.