The net photosynthetic rate (A), stomatal conductance (g_s), and transpiration rate (E), chlorophyll content, and midday xylem water potential (Ψ_md) of Pinus nigra Arn. subsp. pallasiana (Lamb.) Holmboe trees were studied in a natural stand (Burdur-Aziziye, Turkey) for the first (2015), second (2016) and third (2017) years after precommercial thinning (PCT) to better understand the physiological and biochemical responses of trees in a semiarid region. In this study, three treatments (control, 2–2.5 × 2–2.5 m and 3–3.5 × 3–3.5 m spacing) were applied. Soil water content (SWC) and soil temperature (ST) was greater in both PCT treatments than in the control treatments. In general, the control treatment had a lower Ψ_md compared with PCT treatments. A, g_s, and E are generally higher than PCT treatments applied with 3–3.5 m spacing. The lowest g_s and E were determined in the control trees. Ψ_md and A were positively correlated with SWC, but negatively correlated with ST. The decrease in stress level, improvement in resources, and reduced competition for resources by fewer trees increased the A and g_s in trees in the PCT treatments. Chlorophyll a, chlorophyll b, and total chlorophyll content are higher in the control treatments as compared to PCT treatments. SWC, ST, Ψ_md, A, g_s, E, and photosynthetic pigment showed seasonal changes. The two PCT treatments were generally similar in the ecophysiological changes in plots and a longer time is needed to decide for PCT treatments applied with 3–3.5 m spacing. According to the results obtained, it is recommended that PCT be applied with spacings of 2–2.5 × 2–2.5 m.

黑松Arn的净光合速率（A），气孔导度（g _s）和蒸腾速率（E），叶绿素含量和中午木质部水势（_Ψmd）。亚种 在天然稀疏林（土耳其Burdur- Aziziye）中研究了pallasiana（Lamb。）Holmboe树，进行了商业稀疏（PCT）后的第一年（2015年），第二年（2016年）和第三年（2017年），以更好地了解生理和生化半干旱地区树木的反应。在这项研究中，应用了三种处理方法（对照，2-2.5×2-2.5 m和3-3.5×3-3.5 m间距）。两种PCT处理的土壤含水量（SWC）和土壤温度（ST）均高于对照处理。一般情况下，控制的治疗具有较低的Ψ _MD与PCT治疗相比。A，g _s和E通常高于以3–3.5 m间距应用的PCT处理。在对照树中确定了最低的g _s和E。Ψ_的md和A均与SWC相关，而与ST负相关。更少的树木减少了压力水平，改善了资源，减少了对资源的竞争，增加了PCT处理中树木的A和g _s。与PCT处理相比，对照处理中的叶绿素a，叶绿素b和总叶绿素含量更高。SWC，ST，_Ψmd，A，g _s，E和光合色素显示季节性变化。两种PCT处理在地块的生态生理变化方面通常是相似的，并且需要更长的时间来决定间隔为3–3.5 m的PCT处理。根据获得的结果，建议以2–2.5×2–2.5 m的间距应用PCT。