Dynamic conservation of forest genetic resources in 33 European countries.

Dynamic conservation of forest genetic resources (FGR) means maintaining the genetic diversity of trees within an evolutionary process and allowing generation turnover in the forest. We assessed the network of forests areas managed for the dynamic conservation of FGR (conservation units) across Europe (33 countries). On the basis of information available in the European Information System on FGR (EUFGIS Portal), species distribution maps, and environmental stratification of the continent, we developed ecogeographic indicators, a marginality index, and demographic indicators to assess and monitor forest conservation efforts. The pan-European network has 1967 conservation units, 2737 populations of target trees, and 86 species of target trees. We detected a poor coincidence between FGR conservation and other biodiversity conservation objectives within this network. We identified 2 complementary strategies: a species-oriented strategy in which national conservation networks are specifically designed for key target species and a site-oriented strategy in which multiple-target units include so-called secondary species conserved within a few sites. The network is highly unbalanced in terms of species representation, and 7 key target species are conserved in 60% of the conservation units. We performed specific gap analyses for 11 tree species, including assessment of ecogeographic, demographic, and genetic criteria. For each species, we identified gaps, particularly in the marginal parts of their distribution range, and found multiple redundant conservation units in other areas. The Mediterranean forests and to a lesser extent the boreal forests are underrepresented. Monitoring the conservation efficiency of each unit remains challenging; however, <2% of the conserved populations seem to be at risk of extinction. On the basis of our results, we recommend combining species-oriented and site-oriented strategies.

Flowering on long and short shoots of Larix laricina in response to differential timing of GA(4/7) applications.

In Larix, reproductive buds most often occur terminally on short shoots, but they can also differentiate in lateral positions on long shoots. The phenology of long and short shoots differs considerably, with short shoots breaking bud and expanding about 5 weeks before the start of long shoot extension. Foliar sprays of GA(4/7) were applied to 160 branches on 10 greenhouse-grown Larix laricina (Du Roi) K. Koch grafts either before (early) of after (late) the start of long shoot extension, or during both periods, to test whether the timing of GA(4/7) application affects flowering on short and long shoots. All three treatments induced flowering on both long and short shoots. The early GA(4/7) treatment led to slightly, but not significantly, more flowering on short shoots than on long shoots, whereas the late GA(4/7) treatment resulted in increased flowering on both types of shoots, but primarily on long shoots. Application of GA(4/7) during both periods did not result in increased flowering over the early or late treatment alone. Based on the fact that gibberellins are metabolized rapidly in conifers and our finding that GA(4/7) applied before shoot elongation, when the bud primordia were at a very early stage of development (detectable bud differentiation only occurred several weeks later), induced flowering on long shoots, we conclude that the early GA(4/7) treatment did not affect differentiation as it was occurring, but somehow predisposed the bud primordia to differentiate reproductively.