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Aim of study: The aim of this study was to analyze the effects of initial spacing on early growth and carbon sequestration rates in Turkish red pine plantations up to 12 years old, established with improved seeds and deep soil cultivation.Area of study: The study was conducted on experimental sites established in two locations within the Turkish red pine natural distribution areas, namely Duacı and Nebiler close to Antalya city.Material and methods: Data were collected from the experimental sites established as a Nelder design (fan-shaped), with 72 rays and 18 arcs (circles), and trees were planted (almost square) at distances ranging from 1.15 to 4.77 m. Soil type of both sites is loamy, with soil clay content varying between 70-87% in Duacı and 51-70% in Nebiler. Soils are deep being more than one m in both sites, but rockier in Nebiler, providing better soil drainage in this site.Main results: The results showed that mean total height was greater at closer spacing than those of wider spacing until age eight. Growth retardation at wider spacing in early years may be related to water loss due to evaporation in hot summer days and weed suppression. Following the age eight, competition among trees appears to be the major factor reducing the growth and carbon fixation. Diameter at breast height and individual tree volume increased, while stand volume, mean annual volume increment and annual carbon storage per hectare considerably decreased for wider spacing. Our results suggest that in order to obtain higher yield and more carbon fixation, short rotation plantations should initially be established in closer spacing, followed by thinning in subsequent years as required by silvicultural concerns. In this context, spacing 3.0 × 1.0 m or 3.0 × 1.5 m (3.0 and 4.5 m 2 growing area per tree, respectively) seems to be more plausible, providing farm machinery for maintenance and harvesting. We also found that mean annual volume increment per unit area can be considerably increased by using improved seed and deep soil cultivation in plantations.Research highlights: Results encourage managers for short rotation management in industrial plantations using closer spacing in terms of carbon sequestration as well as wood production.Keywords

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Background The purpose of this study was to investigate the effects of thinning on stand growth, carbon (C) sequestration, and soil properties in Brutia pine (Pinus brutia Ten.) plantations. The study was conducted at two experimental sites -the Antalya-Kaş and Isparta-Eğirdir plantation areas- in Turkey between 1985 and 2015. Different thinning intensities -unthinned (control), moderate, and heavy- were replicated in four blocks. We determined the C in the living biomass, litter, soil, and some soil features for each experimental parcel. Results We found no statistically significant difference in total stand volume between thinning-intensity treatments 30 years after thinning. This may be due to more light availability and less competition between trees and faster tree-diameter growth rate after thinning, thus explaining the volume in the treated parcels compared to the control over time. The C stocks in the biomass, litter, and soil were not significantly influenced by the thinning intensity. The nutrients in the litter and soil, and other soil properties, were not significantly different among thinning parcels. This implies that the C and other nutrients in the litter and soil are related to the stand volume and biomass, which were not changed by thinning in time. Conclusion This finding is important in terms of showing that there was no change in total stand volume by thinning, which has been debated in the literature. This information is useful for forest managers when determining thinning strategy.

Bu çalışma ile sıklık çağına gelmiş kızılçam ağaçlandırma alanlarında yapılacak değişik dozdaki ayıklamaların ve aralamaların, meşcere artım ve büyümesi üzerine olan etkilerinin incelenmesi amaçlanmıştır. Araştırma, 1982-2016 yılları arasında Kaş-Tekircik ve Eğirdir-Aşağı Narlı kızılçam ağaçlandırma alanı olmak üzere iki yerde yürütülmüştür. Rastlantı blokları deneme deseni kullanılmış; Kaş ve Eğirdir deneme alanlarında toplam 5 blok ve 35 parselden elde edilen veriler değerlendirilmiştir. Araştırmada aralama şiddeti işlem olarak; 1) kontrol, 2) mutedil aralama ve 3) şiddetli aralama şeklinde üç işlemli bir uygulama yapılmıştır. Deneme parsellerinde, kontrol parselleri hariç olmak üzere, 1990 ve 2004 yıllarında, meşcerenin ihtiyaç gösterdiği parsellerde ve düzeyde aralamalara devam edilmiştir. Araştırma sonucu; Meşcereye müdahale edilen parsellerde, 1985, 1990 ve 2004 yıllarında yapılan ölçme sonuçlarına göre Ortalama çapın, belirgin bir şekilde arttığını göstermiştir. Yine her iki yerde, toplam 5 blok üzerinden yapılan varyans analiz sonucunda, aralamaların göğüs yüzeyi ve kalan meşcere hacmi üzerinde p<0,05 anlamlılık düzeyinde etkili olduğu anlaşılmıştır. Parsellerde 44. yaşında, kalan meşcere hacmi için yapılan varyans analizi sonuçlarına göre, aralama şiddetinin kalan meşcere hacmi üzerinde etkili olduğu gözlenmiştir. Genel meşcere hacminin ise, yapılan istatistik analizler sonucunda p<0,05 anlamlılık düzeyinde, aralamalardan etkilenmediği sonucuna ulaşılmıştır. Sonuç olarak, kızılçam ormanlarında, işletme amaçları çerçevesinde, büyümeyi kaliteli gövdeler üzerinde toplamaya yönelik olarak, büyümenin hızlı olduğu genç yaşlarda, ekonomik açıdan da uygun olacağı düşüncesi ile müdahale sıklığını azaltmak ve bunun için de şiddetli aralama ile göğüs yüzeyinin %35-40'ının alınması şeklinde aralamanın yapılabileceği önerilebilir.