Forest management systems are manifold even though they do not fully reflect the enormous biodiversity within and among forest ecosystems (Günter et al., 2011). Different societal demands and different public pressures are important drivers creating a variety of silvicultural approaches to manage

forests (Kimmins, 2008). The most important and universal aspects related to the regeneration, stand development and harvesting of managed find more forests which impact genetic diversity are described in this section. Regeneration is the basic process that maintains forest ecosystem dynamics and, as such, is a key aspect of any sustainable forest management system (Ackzell, 1993). The fundamental distinction between natural regeneration based on seed and seedlings or vegetative propagules and artificial regeneration by planting or, less frequently by direct seeding, is particularly important for forest genetic resources (FGR). Artificial regeneration disrupts the continuous evolution of tree populations at a given site, but opens opportunities for increasing genetic SRT1720 datasheet diversity

and enhancing productivity through the selection of superior provenances (White et al., 2005). Natural regeneration allows the transmission of genetic information to the next generation, but does not preclude adaptive and non-adaptive changes of genetic structures during the regeneration phase (Rajora and Pluhar, 2003). Silvicultural treatments such as enrichment planting, that mainly aim to enhance the value of secondary tropical forests (Schulze et al., 2008) by planting seedlings in patches where natural regeneration failed, exemplify options that combine artificial and natural regeneration in flexible silvicultural systems. The issue requires careful study since Schwartz et al. (2013) indicate positive effects when post-harvest silvicultural treatments are applied to increase the number of valuable trees. Another example

that combines natural and artificial regeneration is the conversion of pure stands these into mixed forests. The admixed species is frequently introduced by planting seedlings or by direct seeding, whereas the species to be converted contributes to the next generation by natural regeneration (Ammer et al., 2008). Thinning operations are the main silvicultural techniques used for increasing the commercial value of forest stands during their development (Rötzer et al., 2010 and Zeide, 2001). The growth of the most valuable trees within the stand is promoted and their spatial distribution optimized by removing trees of inferior quality. Since selective thinning is based on a phenotypic assessment of the trees in a stand, changes at a genetic level are expected when quantitative (e.g., height or diameter growth) and qualitative (e.g., stem form) traits used for selecting trees are at least partially under genetic control (Finkeldey and Ziehe, 2004). Harvesting operations start after trees attain their target dimensions.