Pollen movement under alternative silvicultural practices in native populations of Scots pine (Pinus sylvestris L.) in central Spain Juan J. Robledo-Arnuncio a,b , Peter E. Smouse c , Luis Gil a , Ricardo Alı ´a b,* a Unidad de Anatomı ´a, Fisiologı ´a y Gene ´tica, ETSIM, Ciudad Universitaria s/n, 28040 Madrid, Spain b Centro de Investigacio ´n Forestal, CIFOR-INIA, P.O. 8111, 28080 Madrid, Spain c Ecology, Evolution & Natural Resources, Rutgers University, New Brunswick, NJ 08901-8551, USA Abstract As conservation genetics is integrated into multipurpose forest management, questions regarding the genetic effects of silviculture arise. Careful harvesting regimes, using natural regeneration, could preserve genetic resources within commercially important species, both in reserves and in logged areas. We investigated the effects of two natural regeneration methods, shelterwood and group selection cutting, on subsequent pollen movement and mating system in four native stands of monospecific Scots pine (Pinus sylvestris L.) in the Guadarrama Chain of central Spain. Using TwoGener analysis, we estimated an average pollination distance of 17–22 m and a relatively large effective number of pollen donors (N ep > 70). We found a non-significant trend toward increasing pollination distance and larger effective number of pollen donors, subsequent to cutting. Considering the high conspecific density of the stands we studied (80–315 trees/ha), pollen dispersal estimates seem consistent with values from other studies, using other methods. Mating system analysis, using the MLTR mixed-mating model, showed high outcrossing rates for all four stands (t m ¼ 0:93–0.99), but failed to show significant effects of stand thinning, although slight increases of the outcrossing rate and the apparent rate of consanguineous mating (t m –t s ) occurred, subsequent to cutting. Results suggest that the pollination system of Scots pine is resilient enough to preclude a negative impact of natural regeneration cutting. From the pollination point of view, normal Scots pine silvicultural systems seem compatible with genetic conservation purposes in central Spain. # 2004 Elsevier B.V. All rights reserved. Keywords: Pinus sylvestris; Pollen dispersal; Mating system; Natural regeneration; nSSR; Gene conservation 1. Introduction Conservation of naturally reproducing forest tree populations permits the continued operation of normal evolutionary processes, which is central to the con- servation of genetic resources (Eriksson et al., 1993). It is generally advisable to set some populations aside, as reserves subjected to minimal human influence, but it has been suggested that careful silvicultural man- agement in harvested areas could also be an effective strategy for genetic conservation (Stahl and Koski, 2000). Moreover, to cease exploitation of valuable species will be problematic in areas where tree har- vesting represents an important economic or tradi- tional activity. If we are to continue resource utilization, an understanding of the impact of silvi- cultural practices on genetic processes of harvested species remains an essential component of silvicul- tural practice and genetic conservation policy. Forest Ecology and Management 197 (2004) 245–255 * Corresponding author. Tel.: þ34 91 3476857; fax: þ34 91 3572293. E-mail address: alia@inia.es (R. Alı ´a). 0378-1127/$ – see front matter # 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.foreco.2004.05.016