Browsing by Author "Seki M."

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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.
Ecoregion-based height-diameter models for Crimean pine
(2022-01-01) Seki M.; Sakici O.E.
Generalized height (h)–diameter (d) models were developed for Crimean pine stands in the Kastamonu Regional Directorate of Forestry, northwestern Turkey. Nine generalized h-d models were fitted and evaluated based on data set consisting of 2697 h-d measurements obtained from 274 sample plots located in three ecoregions of the studied region. The best results were obtained by modified Richards h-d model accounting for the 93% of the total variance in height–diameter relationship. It is a known fact that h-d relationship can vary in ecological conditions, especially for regions with large areas and various ecological conditions such as Kastamonu. To investigate the differences of height–diameter relationship among the ecoregions located in Kastamonu region, nonlinear extra sum of squares method was performed. The test results showed that there were significant differences, especially between coastal and the inland ecoregions. When compared to reduced model with the same set of parameters for the whole region, full model with a different set of parameters for each ecoregion achieved better accuracy in estimating tree height. Besides, applying h-d model fitted for the coastal ecoregion to the others, or vice versa, could lead under- or over-estimates of tree heights by about 1.8%.
Ecoregional Variation of Crimean Pine (Pinus nigra subspecies pallasiana [Lamb.] Holmboe) Stand Growth
(2022-10-01) Seki M.; Sakici O.E.
Investigation and numerical determination of the effects of ecologically different regions on forest growth are important issues to be considered for sustainable forest management. In this study, differences in growth patterns of Crimean pine (Pinus nigra subsp. pallasiana [Lamb.] Holmboe) stands among the ecoregions located in the Kastamonu region of northwestern Turkey were investigated. For this purpose, stand-level growth models for dominant height, number of trees, basal area, and volume were fitted using the data from 274 sample plots and 293 stem analysis in even-aged, pure, and productive Crimean pine stands. The nonlinear extra sum of squares method and graphical examinations revealed that growth characteristics of these Crimean pine stands were affected by ecoregional differences. Ecoregion-based growth models, which are more flexible and have the ability to reflect the ecoregional differences in growth patterns, were found to be superior to regional models. Applying general models without any ecoregional classification resulted in biases of 5.3%, 23.1%, 5.5%, and 6.2% in the estimates of dominant height, number of trees, basal area, and volume of Crimean pine stands, respectively. The results showed that ecological differences must be considered in studies on forest growth modeling and forest management. Study Implications: Investigation and numerical determination of the effects of ecoregional differences on forest growth are important issues to be considered for sustainable forest management. In this study, differences in growth patterns (dominant height, number of trees, stand basal area, and stand volume) of Crimean pine (Pinus nigra subsp. pallasiana [Lamb.] Holmboe) stands among the ecoregions located in the Kastamonu region of northwestern Turkey were investigated. Growth characteristics of the Crimean pine stands in the coastal ecoregion showed significant differences to those in the interior. Therefore, it was found necessary to use ecoregion-based growth models instead of a regional model for the entire region.
How good is TanDEM-X 50 m forest/non-forest map? Product validation using temporally corrected geo-browser supplied imagery through Collect Earth
(2023-01-01) Akturk E.; Altunel A.O.; Atesoglu A.; Seki M.; Erpay S.
TanDEM-X Forest/Non-Forest (FNF) map(s) have been one such data focusing on the status of global forest coverage, which has played an essential role in combating climate change. Although the producers have carried out verification and comparison analyses, the need for accuracy assessments in a broader sense creates uncertainties for the users to approve the new data. For this purpose, TanDEM-X 50 m FNF maps were exclusively examined visually through 66,000 test grids within 30 geocells selected from temperate, boreal, and tropical forest zones. Thus, it was aimed to provide product accuracy utilizing visual inspections to the end users of TanDEM-X FNF maps. In addition, Collect Earth (CE) software was used to evaluate the dataset visually, and its advantages or disadvantages were compared with similarly designed studies. Consequently, even though the producers’ data sets were found to have an accuracy of around 85%, it was observed that there were some issues, especially in the definition of the “non-forest” class. CE software was found to be helpful in such studies. However, the dependence of the analyses on geo-browser supplied imagery had some limitations in estimating the accuracy of a new dataset.
The effects of pine mistletoe (Viscum album subsp. austriacum) on the growth of Scots pine and Crimean pine in Turkey
(2023-01-01) Sakici O.E.; Özcan G.E.; Seki M.; Sağlam F.
In this study, the effect of pine mistletoe (Viscum album subsp. austriacum) on basal area increment of Crimean pine and Scots pine was investigated. Dendrochronological data were collected from 223 (71 uninfected and 152 infected) Crimean pines and 195 (77 uninfected and 118 infected) Scots pines located in Kastamonu province of Turkey in 2014. Infected sample trees were classified as light, moderate or severe infection levels. Growth trends and basal area increment loses were compared between uninfected and infected trees for the periods of the last 10, 20 and 30 years. In addition, infection status of forest stands was investigated using temporary sample plots; 27 plots in Crimean pine stands and 26 plots in Scots pine. Results demonstrated that basal area increments were negatively affected by pine mistletoe for both species. Mean basal area increment losses of infected trees for the last decade were determined as 24% for Scots pine and 26% for Crimean pine. Basal area increment losses varied by infection levels (light, moderate and severe) as follows: 25%, 20% and 28% for Scots pines and 20%, 32% and 9% for Crimean pines. Scots pine stands were more severely infected by pine mistletoe than Crimean pine stands. There were negative correlations between number of infected trees and stand density for both species, while positive correlation was detected between the number of infected trees and mean diameter for Scots pine. The results of this study indicate that the pine mistletoe infection has negative effect on radial growth of Scots pine and Crimean pine trees. The results can be an important contribution to the forest management and protection activities in mistletoe-infected stands.