CONICET | Buscador de Institutos y Recursos Humanos

Extensive knowledge of the ecological and genetic consequences ofimplementing management practices (i.e. logging) in natural ecosystems is of fundamentalimportance to conservation action. Accordingly, characterization of forestgenetic resources in managed vs non-managedstands may inform management decisions to ensure the long-term persistence ofgenetic diversity. The main objective of this study was to evaluate the impactof management practices on the genetic diversity and spatial genetic structureof contrasting forests, through an age-class sampling design and the use of microsatellitemarkers. We evaluated the impact of logging in three populations of Nothofagus pumilio, a dominant treespecies in Patagonian temperate forests, by comparing managed and non-managedstands in each population. Selective extraction of best-featured individuals,i.e. those with forestry aptitude, such as higher trees with straight trunks and good sanitary conditions, was performed between 1990 and2004. One of the studied sites was located in a state-protected area while the otherswere on private land affected by grazing. At each managed stand over-mature trees (MF-O), adultremnant trees (MF-A) and seedlings representing forest regeneration (MF-R)after silvicultural management were sampled. In non-managed stands age classeswere restricted to adults (CF-A) and seedlings (CF-R). A minimum of 30individuals per age class were collected, totalling 454 samples which were genotypedat six microsatellite loci.Non-significant differences in genetic diversity were found betweenmanaged and natural woods in all populations. A trend towards decreasingfrequencies or even allele loss among remnant adults of logged stands can howeverbe interpreted as a sign of impact, probably a consequence of genetic drift. Eachsite showed particular, different outcomes with respect to genetic structure.While in Pop 1 (Huemules, 42°S) significant genetic differentiation was found betweenmanagement treatments, admixture of genetic clusters (Bayesian clustering andDAPC analysis) occurred in Pop 2 (Guacho Lake, 43°S) and no genetic structure wasfound in Pop 3 (Engaño Lake, 43°S). Post-harvest genetic contact betweencontrasting stands is likely. A Landscape Interpolation Analysis showed clustersof individuals (shared genotypes) spatially restricted for managed stands (significantin Pop 3), whereas a random spatial distribution characterized control forests.Therefore, it is possible that management affected and disrupted the geneticstructure. The different genetic patterns revealed for eachpopulation call for site-by-site interpretation. Differential intensity and frequencyof management practices, presence/absence of livestock in the forest, andevolutionary history may all have had combined effect on current geneticdiversity.

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