Nevzat Gürlevik

Development of ecoregion-based merchantable volume systems for Pinus brutia Ten. and Pinus nigra Arnold. in southern Turkey

Estimating individual tree volume is one of the essential building blocks in forest growth and yield models. Ecologically based taper equations provide accurate volume predictions and allow classification by merchantable sizes, assisting in sustainable forest management. In the present study, ecoregion-based compatible volume systems for brutian pine and black pine in the three ecoregions of southern Turkey were developed. Several well-known taper functions were evaluated. A second-order continuous-time autoregressive error structure was used to correct the inherent autocorrelation in the hierarchical data, allowing the model to be applied to irregularly spaced and unbalanced data. The compatible segmented model of Fang et al. (For Sci 46:1–12, 2000) best described the experimental data. It is therefore recommended for estimating diameter at a specific height, height to a specific diameter, merchantable volume, and total volume for the three ecoregions and two species analyzed. The nonlinear extra sum of squares method indicated differences in ecoregion and tree-specific taper functions. A different taper function should therefore be used for each pine species and ecoregion in southern Turkey. Using ecoregion-specific taper equations allows making more robust estimations and, therefore, will enhance the accuracy of diameter at different heights and volume predictions.

EFFECTS OF STRATIFICATION AND MECHANICAL PRETREATMENTS ON GERMINATION OF SYRIAN JUNIPER (Arceuthos drupacea Ant. et Kotschy) SEEDS

Syrian juniper is an important local species which has only a limited distribution on earth. However, there is a lack of information on how to germinate and grow this species. In this study, effects of various stratification and mechanical pretreatments on germination of Syrian juniper seeds were investigated. Stratification treatments included cold-moist and warm-moist stratification for up to 30 months. Breaking (seeds fully exposed) and cracking (seeds remained inside the seed coat) were tried as mechanical treatments. Results showed that, while cold-moist stratification failed to result in any germination, germination percentage following warm-moist stratification first increased, then decreased as the period of stratification got longer. Both breaking and cracking produced successful results among the mechanical treatments. Especially, cracking resulted in a 66 % germination percentage, which was the highest rate achieved in the study. Therefore, Arceuthos seeds either have to be warm-moist stratified for a long time up to 24 months, or seed coats have to be cracked partially for a successful germination to take place.

SINGLE and DOUBLE ENTRY TREE VOLUME TABLE of BLACK LOCUST (Robinia pseudoacacia L.) in ISPARTA-GOLCUK REGION

In this study, a local single and double entry volume table was formed for artificially grown black locust (Robinia pseudoacacia L.). Regression analysis was used in forming the tree volume table. A total of 13 tree volume models were tested for single-entry (6) and double-entry (7) tables. Correlation coefficients for Dissescu-Meyer and Schumacher-Hall models selected were 0.994 and 0.997, respectively. Standard errors of the two regression models were 0.036 and 0.087 m3, total error percentages were –0.255 and 0.820, absolute mean error percentages were 2.426 and 5.370 for the first and second models, respectively. Valuations of these two volume functions were performed against an independent dataset, and it was concluded that they were suitable for black locust plantations in Isparta-Golcuk region with a 95% confidence. As a result, a single and double entry volume table was created for black locust. Keywords: Black locust, Robinia pseudoacacia L., Regression analysis, Single and double entry tree volume table.