Abstract
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 m2 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: Pinus brutia Ten.; spacing; forest growth and yield; carbon sequestration; Nelder experimental design.Abbreviations used: TFS: Turkish Forest Service; OGM: General Directorate of Forestry; Dbh: Diameter at breast height.
Highlights
Initial spacing affects the stand growth rate and mean tree size (Zhang et al, 1996; Harms et al, 2000; Sharma et al, 2002; Harrington et al, 2009; Amateis & Burkhart, 2012) and determines the timing and intensity of competition among trees for resources (Harrington et al, 2009)
The main objective of this study is to investigate the effects of planting spacing on individual tree growth of Turkish red pine stands in young ages (4 to 12 years-old)
— Height growth was greater in closer spacing than in wider spacing in early stages of the plantation sites, namely before inter-tree competition starts
Summary
Initial spacing affects the stand growth rate and mean tree size (Zhang et al, 1996; Harms et al, 2000; Sharma et al, 2002; Harrington et al, 2009; Amateis & Burkhart, 2012) and determines the timing and intensity of competition among trees for resources (Harrington et al, 2009). There have been rather limited studies on the effects of spacing on various stand parameters on Turkish red pine (P. brutia Ten.) native to Turkey. Boydak (1982) investigated the effects of spacing on growth of P. brutia in Northwestern part of Turkey on different soil types and ecological conditions using
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