Integration of Conservation Strategies of Plant Genetic ... - Genres

Diverse environment throughout the range leads to genetically variable species. Patterns of
inherent variation follow environmental variation. Species with a continuous range thus show
clinal variation, species with discontinuous ranges more ecotypic specialization. But both
patterns can occur in the saime species side by side depending on the characters under
consideration.
Variation within subpopulations can be quite different due to historical differences in size of
founder population and selection pressure. Generally within population variation exceeds
between population variation, which may be due to the heterogeneous environment in time
and space.
Exploration of forest gene resources should follow major environmental gradients (elevation,
temperature, day-length). Marginal populations may be of special importance.
Trees themselves conserve genetic information over centuries. This is a basis difference
compared to all other organisms and an obvious advantage for conservation work, as it is a
disadvantage for breeding and selection. Between germination of the seed and flowering
usually some decades pass, which restricts immediate utilization of plants after establishment.
After germination and during the early stand development intensive natural selection is going
on, under natural conditions reducing the numbers from some hundred thousands to few
hundreds. This process is accompanied by an increase of heterozygosity of the surviving part
of the population.
In situ conservation therefore has a high priority. The genetic system is maintained in a
dynamic way under the pressure of natural selection where evolutionary processes are
continuously going on. This method does not guarantee the conservation of all material
however. Rare tree species often do not form breeding populations but only exist as single
individuals or small groups. They must be concentrated in seed orchards. Catastrophes like
fire, storm, ice rain or snow break often endanger whole populations. The immissions
influence the selection processes already before seed formation by differential influence on
pollen survival and they can endanger survival of whole forest areas in exposed locations.
Therefore ex situ conservation is necessary as well as a main activity in rare species, as a
supplement in more common species. A main obstacle for efficient conservation work are the
poor inventory data for rare species and the lack of knowledge of genetic variation between
and within populations.
The following conservation methods are used in forestry:
In situ:
- protected areas and specific conservation stands
- plantations
- single trees