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the 18th century. And then, the first studies on yield tables were conducted in pure stands towards the end of the 18th and beginning of the 19th centuries (Vanclay, 1994). These original tables were simplified counterparts of contemporary yield tables. Pretzsch (2009) classified growth models into four historical stages: i) simple yield tables organized using limited data from growth models (between the final quarter of the 18th century and the 19th century), ii) regular yield tables based on age and site index yield strength variables (between the final quarter of the 19th century and the beginning of 20th century), iii) yield tables where growth relationships are calculated using computerized mathematical models (between the first and last quarter of the 20th century), iv) extremely detailed stand simulation models that can be challenging to execute even on systems with a lot of Read Access Memory (RAM) (from the final quarter of the 20th century to the present) (Kahriman et al., 2016a).
Due to its range, growth and increment characteristics, and economic significance, Calabrian pine (Pinus brutia Ten.) is one of Türkiye’s most important main forest tree species (Sönmez et al., 2016). According to the 2020 forest inventory data released by the General Directorate of Forestry, Türkiye’s total forest area is 22,933,000 ha, which corresponds to 29.4 percent of the country’s total area. The Calabrian pine is distributed on the 5,215,292 ha of the total forest area (22.74 percent of the total forest area). The Calabrian pine is composed of high stands that cover 3,407,368 ha (65.33%) and degraded stands that cover 1,807,924 ha (34.67%) (General Directorate of Forestry, 2021). The total growth stock, annual volume increment, regeneration site area, and average annual allowable cut of Calabrian pine stands are 270 million m3, 7.95 million m3, 262,000 ha, and 3.4 million m3, respectively (General Directorate of Forestry, 2021) (Directorate General of Forestry, 2016). Consequently, there is significant potential for applying the findings in practice.
Many researchers have investigated Calabrian pine stands, and they have produced yield tables as a result of their research. For instance, using temporary site data obtained from even-aged, pure, and untreated stands, Alemdağ (1962) produced the first normal yield tables for Calabrian pine stands. Afterwards, normal yield tables for Calabrian pine stands were established by Erkan (1995) and Çatal (2009) for the Mediterranean region (Kahramanmaraº, Adana, Mersin, Antalya, and Muğla) and the western Mediterranean region (Muğla), respectively. However, Yeºil (1992) created yield tables for Calabrian pine stands that depend on density for the entire country, while ªahin (2015) did so for the Mersin Forest Regional Directorate. Additionally, Karaca (2012) compared the values of yield tables for treated Calabrian pine stands in Bucak-Çamlık Forest Management Unit with the values of normal yield tables for Calabrian pines prepared by Alemdağ (1962), Yeºil (1992), Erkan (1995) and Çatal (2009).
The total economic values at the end of the rotation age for the Calabrian pine and other tree species based on the yield tables were investigated by many researchers (Yaprak, 1977; Öztürk and Türker 1998; Öztürk and Türker 2000; Erkan et al., 2002) in Turkey. Their aim was to find the best economic maturity age for the investigated species. According to Yaprak (1977), the technical maturity age of the Calabrian pine tree species in Turkey for site index classes of good (I), medium (II), and poor (III) was 55, 57, and 110 years, respectively. For site index classes I, II, and III, the maturity age for the highest wood yield (ages where the general average growth is greatest) was 50-55, 55-60, and 60-65 years, respectively. The administration period for pole production was 30, 40, and 50 years, respectively. The economic maturity administration period and the highest land value were 25 years for good sites, 30 years for medium and poor sites (if they are cut at this age), and 40 years for poor sites (only pole, pole and firewood can be obtained). The highest average growth yield was given at the administration period of 65, 75 and 90 years (Yaprak, 1977). The physical administration period (the age of natural maturity) was determined as 310 years in the 120 cm diameter Calabrian pine tree grown in Fethiye-Incirköy (Asan, 1998).
In the last century, some yield tables and stand growth models or growth and yield models have been developed for pure and natural Calabrian pine stands in some neighboring countries. Palahí et al. (2008) developed growth and yield models for Calabrian pine in northeastern Greece. Shater et al. (2011) developed a system of models that allows managers to simulate the dynamics of Calabrian pine stands in Syria using 83 temporary plots. de-Miguel et al. (2010) developed a system of models that allows them to simulate the stand dynamics of Pinus brutia in the Middle East (Lebanon and Syria) using 133 semi-permanent sample plots.
The objective of this study is to develop stand-level growth models as yield tables needed for various forestry applications, especially for management plans and silvicultural practices of pure and natural Calabrian pine stands distributed in the central Mediterranean region (Antalya and Mersin) of Turkey. Thus, growth models will be established, which are one of the prerequisites for multipurpose use of pure, natural and even-aged Calabrian pine stands. These models will allow determining the effects of silvicultural interventions on stand growth as well as to create and compare planning options in the management plan decision- making process with regards to multi-purpose utilization.
The study area consists of pure and natural Calabrian pine stands located within the boundaries of the Antalya and