Relation of Fraxinus excelsior seedling morphology to growth and root proliferation during field establishment

Abstract

The demand for hardwood seedlings has increased in recent years in Italy, particularly for tree farming programmes oriented towards quality wood production; the availability of high-quality seedlings is a crucial step towards being successful in establishing such productive plantations. The aim of this work was to identify the most important morphological seedling quality attributes. Nursery stock consisting of 1-year-old bareroot Fraxinus excelsior seedlings was evaluated for field performance at the end of the first growing season on a plantation site in the Po Valley, northern Italy, in relation to the objective of producing high-quality timber plantations. The approach consisted of (1) morphological characterization (i.e. stem height, root collar diameter, shoot and root architecture) of the seedlings before outplanting; (2) morphological assessment (including root excavations) of the plants after the first year of field growth; (3) relating attributes observed during phases (1) and (2); and (4) identifying those morphological characteristics that effectively predict outplanting success. The results indicate that the highest quality seedlings are best selected on the basis of initial shoot height and root system morphological type (i.e. stem heights 40–50 cm with a fasciculate root system of at least 40 cm length and rich in fine roots). Planting these seedling morphological types may dramatically improve field performance (i.e. more than 100% increase of height increment in this case), which will help to promote the development of afforestation plantations oriented towards high-quality wood production.

Keywords:

• bareroot seedlings
• field performance
• forest nurseries
• Fraxinus excelsior
• reforestation

Acknowledgements

This research is part of the project “Sperimentazione nei settori della vivaistica forestale e dell'arboricoltura da legno—Definizione di standard qualitativi del postime tramite field performance”, financed by Regione Piemonte (Piemonte Regional Administration), Italy.