Germinative capacity and energy of critically endangered Ojców birch (Betula oycoviensis Besser) in the Czech Republic

Ojców birch (Betula oycoviensis Besser) is a rare and critically endangered taxon of the genus Betula. Its distribution is limited to few countries in Europe. In the Czech Republic, this taxon, characterized by typical shrubby habitus, has been found in fewer than 70 tree individuals, prevailingly in the studied locality Volyně, West Bohemia. This study was focused on the germinative capacity and germinative energy of this taxon, as it is an important indicator of possible regeneration of the trees in nature and for conservation. Non-stratified seeds (2 200 pcs) and stratified ones (2 200 pcs) were compared to each other and in relation to dendrometric tree parameters. The results showed no significant (P > 0.1) differences between stratification variants in total germination (higher by 0.8% in stratified), though stratification improved germinative energy. Germination was in 1st week higher by 6.0% in stratified variant, respectively marginally (P < 0.1) higher in 2nd week in non-stratified variant. However, both germinative capacity and germinative energy were significantly (P < 0.01) variable between individual trees. The germinative capacity was significantly (P < 0.05) positively correlated with tree defoliation. Tiny seeds and triploid trees exhibited very low and zero germinative capacity and energy, respectively. Totally, seeds exhibited sufficient germinative capacity and germinative energy of 23.1% (0.0-62.5%). This suggests that the trees can be potentially used for this type of Ojców birch regeneration i.e. generatively from seeds, although rather in controlled artificial conditions.