Growth and yield prediction Models for Ash (Fraxinus angustifolia Vahl.)

Ash (Fraxinus angustifolia subsp. oxycarpa [Bieb. ex Willd.] Franco & Rocha Afonso) is a very fast growing species that has been introduced in the plantations in Turkey for its faster growth and high range of adaptability. Ash forests formed pure stands along the alluvial delta on Sakarya stream of the East Marmara Sea region. In spite of the importance of ash, information on the growth and yield of this species is still not sufficient. In this study, growth and yield characteristics of volume and volume elements in ash forests were investigated in Adapazarı region of Turkey. Data were collected from 27 temporary sample plots from plantations ranging in age from 16 to 36 years. Models selected for ash plantations estimated number of trees, stand mean diameter, stand mean height, stand dominant height, stand basal area and total volume yield. Growth and yield characteristics of ash stands were investigated for different stand age, site index and stand densities. Relationships were determined with multiple regression analysis. Paired t- test, 45 degree line test, percent absolute deviation (AD%) and biological principle of stand development were used for the validation of chosen models. The stand number of trees, stand mean diameter, stand mean height, stand dominant height, stand basal area and stand volume yield models explain 77.4 %, 84.7 %, 92.9 %, 83.5 %, 97.3 % and 95.2 % of the total variation, respectively.