Browsing by Author "Sakici O."

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Above-ground biomass and carbon stock equations for Crimean pine stands in Kastamonu region of Turkey
(2018-01-01) Sakici O.; Seki M.; Saglam F.
For above-ground biomass and carbon stock estimations, the most common single- and double-entry allometric equations were fitted for Crimean pine (Pinus nigra J.F. Arnold subsp. pallasiana (Lamb.) Holmboe) stands in Kastamonu region, northwestern Turkey. The data were obtained from 227 sample trees in 192 sample plots that represent different stand structures and topographic features. Following the fittings, the best models were selected for each component (i.e., stemwood, stembark, branch and needles) and above-ground total biomass and carbon stock estimations. The selected models for aboveground biomass and carbon stock accounted more than 86% of the total variance for each component and 98% for the above-ground total, with low root mean square errors (RMSE). These models also provided biologically realistic estimates.
Dominant height growth and dynamic site index models for crimean pine in the Kastamonu-Taşköprü region of Turkey
(2017-01-01) Seki M.; Sakici O.
Some dynamic site index models based on the generalized algebraic difference approach (GADA) were fitted for Crimean pine (Pinus nigra J.F. Arnold subsp. pallasiana (Lamb.) Holmboe) stands in Taşköprü, Turkey. Data were obtained from 132 dominant trees representing the wide range of site quality in the region. Nonlinear regression analysis and a second-order continuous-time autoregressive error structure were applied. After autoregressive modeling, the fitted models were evaluated both statistically and graphically. The best results were obtained with the dynamic site index model derived from the Bertalanffy- Richards base equation, accounting for about the 99% of the total variance in height-age relationships in dominant trees, with an Akaike information criterion (AIC) value of 119.55 and root mean square error (RMSE) of 0.5446. The selected base-age invariant dynamic site index curves provided the polymorphism with multiple asymptotes and other realistic height growth patterns.
Estimating above-ground carbon biomass using satellite image reflection values: A case study in camyazi forest directorate, Turkey
(2015-01-01) Aricak B.; Bulut A.; Altunel A.; Sakici O.
Forest ecosystems which contain half of the terrestrial carbon deposits; play a significant role in shaping the global climate. Two different methods are used to determine the above-ground carbon stock capacity of forestlands. Direct measurement method takes a long time and requires both extensive as well as expensive field and laboratory work. One of the more indirect methods, satellite imaging on the other hand, costs less, is easier and practical compared to direct methods. It is also easier to integrate into geographic information systems (GIS). This paper provides a regression equation between the reflection values from RapidEye high resolution satellite image and sample areas where terrestrial aboveground biomass (AGB) carbon stock capacity was calculated by direct measurement method. As a result of the calculations made, using the RapidEye imagery and a "Band 4" devised equation producing R2=0.71 depending upon the data from Erzurum Camyazi Forest Directorate encompassing 9,917 ha study area, the amount of carbon stored within stands was found 285 208 tons. From this value, we can conclude that average carbon stock of the study area is 28.8 tons/ha.
Preliminary results of Turkish hazelnut (Corylus colurna L.) populations for testing the nut characteristics
(2018-01-01) Ayan S.; Ünalan E.; Sakici O.; Yer E.; Ducci F.; Isajev V.; Ozel H.
Ovaj rad ima za cilj da identifikuje karakteristike lešnika četiri različite populacije (Agli-Tunuslar, Agli-Musellimler, Arac-Guzluk i Tosia-Kucuksekiler) u severozapadnom regionu crnomorske regije Turske, jednoj od najvažnijih oblasti od ekonomskog interesa za ovu vrstu. Tamo, Turski lešnik (Corylus colurna L.) raste u optimalnim uslovima i otkriva relativno visoku medu-populacionu i intra-populacionu varijaciju u pogledu karakteristika ploda. U cilju procene varijacije, izvršene su merenja u četiri populacije u okrugu Kastamonu za 14 razlicitih karakteristika ploda (broj matica po klasteru, dužina lešnika (mm), širina lešnika (mm), debljina lešnika (mm), debljina školjke (mm), velicina lešnika (mm), oblik lešnika, indeks kompresije, težina matice (g), dužina jezgra (mm), širina jezgra (mm), debljina jezgra (mm), težina jezgra (g) i odnos jezgra (%) na reprezentativnim uzorcima populacije. Značajne razlike su utvrdene medu populacijama u odnosu na sve karakteristike lešnika (p < 0,05). Prema klaster analizi cetiri populacije su stvorile dve grupe, populaciju Agli-Tunuslar i ostale. Najbliže populacije bile su Tosia-Kucuksekiler i Arac-Guzluk u pogledu karakteristika lešnika. Prema rezultatima dobijenim bilo na osnovu populacije ili bez diskriminacijepopulacije, utvrdene su znacajne korelacije izmedu većine osobina lešnika. Populacija Arac-Guzluk je imala najveće lešnike medu onima koji su ispitivani i to je populacija koja je imala najviše vrednosti u pogledu karakteristika velicine oraha dok je provincija Tosia-Kucuksekiler pokazala najviše vrednosti, sa prosecnim vrijednostima od 5, 15,92 mm, 1,32 i 11,75 mm respektivno za lešnike po klasteru, širinu lešnika, indeks kompresije i širinu jezgra. Populacija Agli-Tunuslar je pokazala najviši odnos jezgra sa 38,2%.
Stem taper estimations with artificial neural networks for mixed oriental beech and kazdaği fir stands in karabük region, Turkey
(2018-10-01) Sakici O.; Ozdemir G.
Development of artifi cial neural network (ANN) models to estimate stem tapers of indi- vidual trees in mixed Fagus orientalis and Abies nordmanniana subsp. Equi-trojani stands distributed in Karabük region of Turkey, and comparison of the ANN models with stem taper equations were aimed in this study. The measurements were obtained from 516 sample trees (238 for Oriental beech and 278 for Kazdağı fir) in mixed stands of Karabük region. The measurements included diameter at breast height, tree height, diameter at stump height, and diameters at intervals of 1 m along the stem. In total, 45 ANN models and four stem taper equations were developed. Estimation performances of ANN models and stem taper equations were compared using relative rankings according to seven goodness-of-fi t criteria. As a result, the ANN models were more successful in estimation of stem taper for both tree species. The most successful ANN model structures were (i) the model us- ing logistic function in hidden layer with 10 nodes and hyperbolic tangent function in out- put layer for Fagus orientalis, and (ii) the model using logistic function in hidden layer with 10 nodes and linear function in output layer for Abies nordmanniana subsp. equi-trojani.