Abstract
Clonal propagations of shoot or root fragments play pivotal roles in adaptation of clonal trees to environmental heterogeneity, i.e. soil nutrient heterogeneity and burials after disturbance. However, little is known about whether burial orientation and nutrient supply can alter the effects of fragment traits in Populus. Shoot and root fragments of Populus deltoides × P. simonii were subjected to burials in two different fragment diameters (0.5 and 2.0 cm), two fragment lengths (5 and 15 cm) and three burial orientations (horizontal, upward and downward). For the shoot fragments, survival and growth were significantly higher in the larger pieces (either in length or diameter) and the horizontal/upward burial position. On the contrary, the effect of burial position was reversed for the root fragments. Shoot/root fragments of 15 cm in length in horizontal burial position were then subjected to two different fragment diameters (0.5 and 2.0 cm) and four types of nutrient supplies (without nutrient, low frequency, high frequency and patchy). Growth of shoot fragments of 2.0 cm in diameter significantly increased in high frequency and patchy nutrient supplies than that of without nutrient treatment. These results suggest that burial orientation and nutrient supply could be employed in clonal propagations of cuttings, afforestation or regeneration in Populus.
Highlights
Clonal propagations of shoot or root fragments play pivotal roles in adaptation of clonal trees to environmental heterogeneity, i.e. soil nutrient heterogeneity and burials after disturbance
Treatments of 15 cm in length root fragments had significantly higher survival and growth measures than those 5 cm in length root fragments in downward burial position (P < 0.05), but not for fragments in horizontal or upward positions (P > 0.05) (Table 1, Fig. 1G–L). These results suggest that burial orientation altered the effects of fragment type and fragment length of P. deltoides × P. simonii
The results indicate that burial orientation partly altered the effects of fragment length and fragment diameter of P. deltoides × P. simonii
Summary
Clonal propagations of shoot or root fragments play pivotal roles in adaptation of clonal trees to environmental heterogeneity, i.e. soil nutrient heterogeneity and burials after disturbance. Very thin root cuttings may lack sufficient nutritional reserves or the ability to regenerate shoot primordial[11,17,18] Disturbance such as deforestation (clear-cutting), fire and landslips can disrupt plant structures and modify environmental conditions, such as soil nutrients and burial orientation or depth[19]. Burial orientation in soils may greatly affect survival and growth of clonal fragments because both biotic (e.g., pathogen activities) and abiotic conditions (e.g., nutrient, temperature and moisture) were changed in buried parts of fragments[22,23] After deforestation, such small clonal fragments might become positioned in orientations away from the horizontal, which is the typical orientation for re-growth for Poplar. Nitrate is known to facilitate the biosynthesis of cytokinins[32,35,36], which are known to be involved in sucker initiation in aspen[1,32]
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