Response of Pinus nigra subsp. pallasiana to Precommercial Thinning in a Humid Region Under the Oro-Mediterranean Climatic Conditions

Precommercial thinning is the basic management practice in young Anatolian black pine [ Pinus nigra Arn. subsp. pallasiana ] stands. The aim of this study was to address the lack of knowledge with regard to the impact of the intensity of precommercial thinning on tree growth and stability in Anatolian black pine forest in a humid region under the oro-mediterranean climatic conditions. The field experiment was established in late April 2015 by three precommercial thinning treatments, unthinned control (4941 stems ha − 1 ), 2–2.5 m spacing (PCT 2–2.5 m ) = 2133 stems ha − 1 , and 3–3.5 m spacing (PCT 3–3.5 m ) = 1093 stems ha − 1 , and monitored for three growing seasons. Tree diameter (diameter at breast height), basal area, and crown radius increments showed a positive response to precommercial thinning, especially in the PCT 3–3.5 m plots. The height incre- ment was highest in the unthinned plots. Height:diameter 1.30 m ( h/d ) ratio of trees grown at the PCT 3–3.5 m plots was lower than the other precommercial thinning treatments. The negative correlation between DBH and h/d ratio was slightly decreased for the PCT 3–3.5 m plots in the 3 years after precommercial thinning. The percentage of trees damaged by snow or wind in the second year of the PCT was not significantly affected by precommercial thinning. Precommercial thinning promotes diameter at breast height and crown growth by reducing competition between neighboring trees for natural resources. In addition, findings indicate that precommercial thinning increased stand stability with increasing diameter against snow/wind damage likely to occur at high altitudes of the oro-mediterranean belt.