„Hochlagenfichten“ in Mitteleuropa – ein zusammenfassender Beitrag zur phänotypischen und (epi)genetischen Differenzierung innerhalb Picea abies (L.) H.KARST
Ziel der vorliegenden Studie ist die Zusammenfassung und Diskussion des aktuellen Forschungsstandes zur phänotypischen und (epi)genetischen Differenzierung von Hoch- und Tieflagenfichten(beständen). Es soll die Frage geklärt werden, ob bereits beobachtete phänotypische Merkmalsunterschiede zwischen beiden Morphotypen nur aus einer umweltabhängigen Antwort entstehen (phänotypische Plastizität) oder (teilweise) einer genetischen und/oder epigenetischen Steuerung unterliegen. Für die Forstpraxis sollen einfach handhabbare Merkmalsunterschiede zusammengestellt werden, die von Waldpflegern und -pflegerinnen angewendet werden können und die Förderung bzw. Benachteiligung einzelner Phänotypen unterstützen. Schließlich werden Schlussfolgerungen für den Schutz der Hochlagenfichten und den Waldumbau gezogen. Anpassung; Autochthonie; epigenetische Differenzierung; genetische Differenzierung; Hochlagenfichte; phänotypische Differenzierung; phänotypische Plastizität; Picea abies; Selektion; Tieflagenfichte Adaptation; autochthony; epigenetic differentiation; genetic differentiation; high-altitude spruce; low-altitude spruce; phenotypic differentiation; phenotypic plasticity; Picea abies; selection Tree individuals in the high-altitudes need to cope with shorter vegetation periods, lower temperatures, and higher snow loads compared with their conspecifics in the lowlands. Adaptation through natural selection can lead to both heritable genetic and epigenetic changes, with accompanying phenotypic consequences. Norway spruce (Picea abies (L.) H.KARST ) is a prominent example that shows an altitude-dependent phenotypic variation. Rare relics of ‘high-altitude spruces’ are found in the mountain areas of Central Europe. The unique phenotype of high-altitude spruces is characterized by narrow, cylindrical crowns with brush-plate branches. In many cases, these relics are surrounded by allochthonous ‘low-altitude spruces’. In previous studies, high-altitude types were considered as adaptations to climatic conditions of the middle and high mountain areas. Spruce stands in these regions are highly vulnerable because of an immense risk of crown fracture. Due to a lack of comprehensive studies summarizing easily accessible, adaptive traits (phenology and growth, crown architecture, and needles and cones), a reliable approach and subsequent fostering versus removal of both spruce types in the juvenile and adult stages is hardly possible. Moreover, there is still a concern about genetic and epigenetic differences between both types. We summarized and discussed phenotypic and (epi)genetic studies concerning high-altitude spruces from Germany and neighboring areas. We also provided suggestions on future adaptive potential and forest conversion. In young spruce stocks, same-aged high-altitude types are differentiated from low-altitude ones by earlier and faster sprouting, fewer August shoots, earlier shoot endings, shorter shoot lengths, lower height growth and plant height, and stronger fork formation whereas in the adult stock the brush-plate branching, cylindrical, narrow-crown, shorter side branches (first-order), lower crown diameter, gray-green to gray, shorter, denser needles, and lighter cones and seeds delimit the high-altitude types (genetically and/or epigenetically controlled). In the high mountain areas, crone trait differences probably lead to a lower crown breakage risk of high-altitude types. We classified the lower needle index and stomata density, and cone scales of Obovata-type of high-altitude spruces as presumably adaptive. In general, genetic studies examined so far found only small genetic differences between high- and low-altitude spruce stands. A few, base-precise DNA differences (SNPs) per adaptation-relevant gene, in combination with differential epigenetic regulations, might generate observed phenotypic differences. Most studies suggested that high-altitude genotypes have repeatedly emerged locally or regionally in the mountain areas of Central Europe or have been selected from the spruce gene pool.
