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Bettinger P.,University of Georgia | Demirci M.,General Directorate of Forestry | Boston K.,Oregon State University
Silva Fennica | Year: 2015

The use of a reversion technique during the search process of s-metaheuristics has received little attention with respect to forest management and planning problems. Reversion involves the inter-ruption of the sequence of events that are used to explore the solution space and the re-initiation of the search process from a high-quality, known starting point. We explored four reversion rates when applied to three different types of s-metaheuristics that have previously shown promise for the forest planning problem explored, threshold accepting, tabu search, and the raindrop method. For two of the s-metaheuristics, we also explored three types of decision choices, a change to the harvest timing of a single management unit (1-opt move), the swapping of two management unit’s harvest timing (2-opt moves), and the swapping of three management unit’s harvest timing (3-opt moves). One hundred independent forest plans were developed for each of the metaheuristic/reversion rate combinations, all beginning with randomly-generated feasible starting solutions. We found that (a) reversion does improve the quality of the solutions generated, and (b) the rate of reversion is an important factor that can affect solution quality. © 2015, Silva Fennica. All rights reserved. Source


Bagci S.,General Directorate of Forestry | Cayci G.,Ankara University | Kutuk C.,Ankara University
Journal of Plant Nutrition | Year: 2011

This study was performed under greenhouse conditions, with coir dust, moss peat, and sedge peat as the main components of the growing media. The performance of the media was evaluated through the growth of the primula (Primula obconica) plant. In general, aeration capacities were found to be relatively low, except for growing media that included moss peat mixtures. Nevertheless, easily available water content of all growing media was found to be within the appropriate ranges. Total and water-available plant nutrient contents of coir dust, moss peat, and sedge peat significantly fluctuated. Ornamental parameters related to media treatments were statistically significant, with respect to visual score performances, total leaf numbers, crown width, and total plant fresh weights. This study determined that coir dust, which is an industrial by-product, could be utilized for up to 50% of the total composition of coir dust-moss peat based media in floricultural aims. As floricultural quality parameters considered, 50% coir dust and 50% moss peat and 25% coir dust and 75% moss peat gave good results as much as 100% moss peat © Taylor & Francis Group. Source


Demirci M.,General Directorate of Forestry | Bettinger P.,University of Georgia
Forest Policy and Economics | Year: 2015

Sustainable forest management is a key to maintaining the economic, social, environmental and cultural benefits and services of forests for the long term. In Turkey, all forestry activities, such as regeneration and stand tending, are carried out according to forest management plans, which are used as a tool for achieving sustainable forest management goals. An intermediate yield harvest plan, which is a part of management plan, is used for stand tending. Every year, the compartments (stands) within the same stand tending block are thinned. Decision support systems have not been used so far in order to designate the size and location of these stand tending blocks. In this study, we used multi-objective goal programming to designate stand tending blocks for an entire decade. We developed two models: a linear goal programming model and a nonlinear goal programming model. To design these models, we only considered wood flow and distance between the centroids of compartments as the objectives. Then, we used a working circle of the Golcuk forest sub-district, which is a planning unit in Turkey, as a case study. The linear model worked very well, and for reference scenarios, the deviation in volume scheduled for the entire decade was only 16.8m3 and the deviation in total distance between compartments was 172km. Scenario 3, with weights of 0.2 for distance and 0.8 for volume, produced the best results. The nonlinear model, which in theory would better represent the problem, was not as useful due to a combination of the time required to produce a solution and the quality of the solutions. The linear model can be developed by including other factors and used by forest planners. © 2015 Elsevier B.V. Source


Ozcelik R.,Suleyman Demirel University of Turkey | Yavuz H.,Karadeniz Technical University | Karatepe Y.,Suleyman Demirel University of Turkey | GurlevIk N.,Suleyman Demirel University of Turkey | Kiris R.,General Directorate of Forestry
Turkish Journal of Agriculture and Forestry | Year: 2014

Seven different nonlinear height (h)-diameter (d) models were developed and compared for brutian pine (Pinus brutia Ten.), black pine (Pinus nigra Arnold), and Taurus cedar (Cedrus libani A.Rich.) in southern Turkey. Residual analysis was conducted to identify the error structure. A weighting factor of wi =1/d was found to be appropriate for achieving the equal error variance assumption. The performance of the models was compared and evaluated based on 6 statistical criteria and residual analysis. Results suggested that the Gompertz model was superior to the other models in terms of its predictive ability. These tree species were located throughout the Mediterranean region, covering a wide range of topographic and climatic conditions. It is well known that height-diameter relationships depend heavily on local environmental conditions. Differences in the height-diameter relationship among and between ecoregions were tested using the nonlinear extra sum of squares method. Test results suggested that height-diameter models significantly differed between ecoregions, indicating that ecoregion-based height-diameter models are needed for prediction purposes. The ecoregion-based height-diameter models developed in this study may provide more accurate information for developing forest growth and yield models. © Tübïtak. Source


Tolunay D.,Istanbul University | Karabiyik B.,General Directorate of Forestry | Temerit A.,General Directorate of Forestry
IForest | Year: 2011

Monitoring of forest condition in Turkey started in 2006 when a 16x16 km grid of Level I plots was established. In 2007, the first 48 Pinus brutia plots were surveyed for crown condition. In 2008 and 2009, the plots were 398 and 563, respectively. In 2007, the mean defoliation for P. brutia was 13.0 %. In 2008-2009, the mean defoliation was 19.5-19.8 % and 27.0-23.0 % for coniferous and broadleaved species, respectively. Defoliation was higher than 25 % on 24.6-18.7 % of the monitored trees. The species with the highest defoliation were Carpinus betulus and Juniperus foetidissima in 2008, and Quercus pubescens and Juniperus communis in 2009. The slight improvement in forest health in 2009 may be attributed to better weather conditions than in 2008 (higher precipitation). The forests along the Black Sea coast of Thrace showed the highest defoliation in both 2008 and 2009. This may be due to transboundary air pollution from Istanbul, where sources of sulphate and nitrate pollution occur. Elevated defoliation rates were also observed in the Black Sea region; they were most probably caused by biotic factors in plots subject to industrial pollution. © iForest - Biogeosciences and Forestry. Source

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