Estimating tree bole volume using artificial neural network models for four species in Turkey.

Tree bole volumes of 89 Scots pine (Pinus sylvestris L.), 96 Brutian pine (Pinus brutia Ten.), 107 Cilicica fir (Abies cilicica Carr.) and 67 Cedar of Lebanon (Cedrus libani A. Rich.) trees were estimated using Artificial Neural Network (ANN) models. Neural networks offer a number of advantages including the ability to implicitly detect complex nonlinear relationships between input and output variables, which is very helpful in tree volume modeling. Two different neural network architectures were used and produced the Back propagation (BPANN) and the Cascade Correlation (CCANN) Artificial Neural Network models. In addition, tree bole volume estimates were compared to other established tree bole volume estimation techniques including the centroid method, taper equations, and existing standard volume tables. An overview of the features of ANNs and traditional methods is presented and the advantages and limitations of each one of them are discussed. For validation purposes, actual volumes were determined by aggregating the volumes of measured short sections (average 1 meter) of the tree bole using Smalian's formula. The results reported in this research suggest that the selected cascade correlation artificial neural network (CCANN) models are reliable for estimating the tree bole volume of the four examined tree species since they gave unbiased results and were superior to almost all methods in terms of error (%) expressed as the mean of the percentage errors.

Effects of release cutting on the development of young natural lebanon cedar (Cedrus libani A. Rich) stands of western Mediterranean region of Turkey.

Release cutting is ecologically and economically one of the most important silvicultural treatments for establishing a new stand. The study was designed to determine the suitable silvicultural treatments of different spacing of thinning for release cutting on young natural lebanon cedar (Cedrus libani A. Rich) stands at the thicket stage. Studies were carried out at Bucak and Gölhisar forest districts in the Western Mediterranean region of Turkey between the years of 1999-2005. Results showed that release cutting treatment had a positive effect on diameter growth for individual trees with the 1.5 m x 3 m spacing and positively correlated with spacing of thinning. However there was not significant effect of the thinning application on height growth of young natural Lebanon cedar stands.

Tree species diversity of natural mixed stands in eastern Black Sea and western Mediterranean region of Turkey.

Differences in free species diversity of natural mixed stands were compared between the eastern Black sea region (EBSR) and western Mediterranean region (WMR) of Turkey, to clarify the effects of differences in forest structure, focusing on the tree species occurring in each. Species diversity with special reference to stand structure, of natural mixed stands was quantified by Shannon-Wiener index (H'), equitability index (J'), and species richness index (R). All species diversity indices were significantly higher in EBSR than in WMR. According to the coefficients of homogeneity (CH), stands in EBSR are generally have uneven-aged stand structure, but in WMR even-aged stand structure is more common. Uneven-aged stands have more tree species diversity than even-aged forests due to complex vertical forest structure and species composition. According to Pearson's coefficients, species diversity indices and richness are closely related the average stand diameter (Ds) in uneven-aged stands of EBSR, but average stand diameter (Ds), age (A), and stand density (SDI) are the most important stand parameters in even-aged stands of WMR in Turkey.

Tree species diversity and its relationship to stand parameters and geomorphology features in the eastern Black Sea region forests of Turkey.

We studied the effects of stand parameters (crown closure, basal area, stand volume, age, mean stand diameter number of trees, and heterogeneity index) and geomorphology features (elevation, aspect and slope) on tree species diversity in an example of untreated natural mixed forest stands in the eastern Black Sea region of Turkey. Tree species diversity and basal area heterogeneity in forest ecosystems are quantified using the Shannon-Weaver and Simpson indices. The relationship between tree species diversity basal area heterogeneity stand parameters and geomorphology features are examined using regression analysis. Our work revealed that the relationship between tree species diversity and stand parameters is loose with a correlation coefficient between 0.02 and 0.70. The correlation of basal area heterogeneity with stand parameters fluctuated between 0.004 and 0.77 (R2). According to our results, stands with higher tree species diversity are characterised by higher mean stand diameter number of diameter classes, basal area and lower homogeneity index value. Considering the effect of geomorphology features on tree species or basal area heterogeneity we found that all investigated relationships are loose with R < or = 0.24. A significant correlation was detected only between tree species diversity and aspect. Future work is required to verify the detected trends in behaviour of tree species diversity if it is to estimate from the usual forest stand parameters and topography characteristics.