Integration of Conservation Strategies of Plant Genetic ... - Genres
Integration of Conservation Strategies of Plant Genetic ... - Genres 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
Ex situ: - plantations - seed orchards - clonal collections - seed storage - pollen storage - tissue storage - propagation methods. 3. Efficiency for conservation and utilization 3.1 In situ methods The efficiency of in situ conservation methods depends very much on the tree species and the speed of environmental changes; in natural reserves in addition from between species competition and legal restrictions. Minor, especially rare species (or relict provenances of major tree species) often can be found only with one or few individuals in specific locations. Here in situ conservation can only guarantee the survival of the respective trees until they reach their natural end. For the conservation of the natural diversity of the species and especially for utilization it is necessary to concentrate the scattered individuals in grafted seed orchards to reconstruct breeding populations. By this ex situ method the survival and the utilization of the whole existing gene-pool of the species is possible even if the relict trees in situ died: This ex situ method has the additional advantage, that hybridization with other species or nonadapted provenances can be prevented. For major tree species, still existing in extended populations, in situ conservation stands will be the main conservation method with about 2 % of the actual area. The single populations are selected due to their structure, the heterogeneity of the site and the main ecological gradients. However fast environmental change or catastrophes like fires, storms, ice- and snow break, insects or fungus diseases can endanger in situ populations too. Therefore an additional ex situ conservation - usually as seed in storage - is necessary. However the tree species with recalcitrant seed cannot be stored for long time. Therefore ex situ plantations or storage of embryos in liquid nitrogen are alternatives. The utilization of the in situ stands is possible by seed collection directly, therefore a combination with seed stands seems to be a practical advantage quite often. The conservation stands are naturally regenerated or planted with seedlings grown from seed of the same stand. Degradation of the soil due to immission can be partly counterbalanced by fertilization. Natural reserves do not necessarily guarantee the survival of a specific species. Since no human influence is allowed, a species of interest can be extinct by competition. Usually no seed harvest is possible in these areas, therefore utilization is very restricted. However especially in climax species they can be an interesting addition to in situ conservation stands.
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Ex situ:<br />
- plantations<br />
- seed orchards<br />
- clonal collections<br />
- seed storage<br />
- pollen storage<br />
- tissue storage<br />
- propagation methods.<br />
3. Efficiency for conservation and utilization<br />
3.1 In situ methods<br />
The efficiency <strong>of</strong> in situ conservation methods depends very much on the tree species and the<br />
speed <strong>of</strong> environmental changes; in natural reserves in addition from between species<br />
competition and legal restrictions. Minor, especially rare species (or relict provenances <strong>of</strong><br />
major tree species) <strong>of</strong>ten can be found only with one or few individuals in specific locations.<br />
Here in situ conservation can only guarantee the survival <strong>of</strong> the respective trees until they<br />
reach their natural end. For the conservation <strong>of</strong> the natural diversity <strong>of</strong> the species and<br />
especially for utilization it is necessary to concentrate the scattered individuals in grafted seed<br />
orchards to reconstruct breeding populations. By this ex situ method the survival and the<br />
utilization <strong>of</strong> the whole existing gene-pool <strong>of</strong> the species is possible even if the relict trees in<br />
situ died: This ex situ method has the additional advantage, that hybridization with other<br />
species or nonadapted provenances can be prevented. For major tree species, still existing in<br />
extended populations, in situ conservation stands will be the main conservation method with<br />
about 2 % <strong>of</strong> the actual area. The single populations are selected due to their structure, the<br />
heterogeneity <strong>of</strong> the site and the main ecological gradients. However fast environmental<br />
change or catastrophes like fires, storms, ice- and snow break, insects or fungus diseases can<br />
endanger in situ populations too. Therefore an additional ex situ conservation - usually as<br />
seed in storage - is necessary. However the tree species with recalcitrant seed cannot be<br />
stored for long time. Therefore ex situ plantations or storage <strong>of</strong> embryos in liquid nitrogen<br />
are alternatives.<br />
The utilization <strong>of</strong> the in situ stands is possible by seed collection directly, therefore a<br />
combination with seed stands seems to be a practical advantage quite <strong>of</strong>ten.<br />
The conservation stands are naturally regenerated or planted with seedlings grown from seed<br />
<strong>of</strong> the same stand. Degradation <strong>of</strong> the soil due to immission can be partly counterbalanced by<br />
fertilization.<br />
Natural reserves do not necessarily guarantee the survival <strong>of</strong> a specific species. Since no<br />
human influence is allowed, a species <strong>of</strong> interest can be extinct by competition. Usually no<br />
seed harvest is possible in these areas, therefore utilization is very restricted. However<br />
especially in climax species they can be an interesting addition to in situ conservation stands.
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