Impacts of precommercial thinning on gas exchange, midday water potential, and chlorophyll content in Pinus nigra subsp.
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ORIGINAL ARTICLE
Impacts of precommercial thinning on gas exchange, midday water potential, and chlorophyll content in Pinus nigra subsp. pallasiana stand from the semiarid region Esra Bayar1 · Ayşe Deligöz1 Received: 24 July 2019 / Accepted: 13 May 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The net photosynthetic rate (A), stomatal conductance (gs), and transpiration rate (E), chlorophyll content, and midday xylem water potential (Ψmd) 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, gs, and E are generally higher than PCT treatments applied with 3–3.5 m spacing. The lowest gs and E were determined in the control trees. Ψmd 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 gs 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, Ψmd, A, gs, 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. Keywords Stand · Gas exchange · Water potential · Soil water content · Pinus nigra · Precommercial thinning
Introductıon In the recent years, global warming and climate change have become one of the biggest topics. Forests are exposed to changes in climatic conditions because of global warming. In order to minimize their negative impact on plant communities, especially on forests, we should protect, maintain and improve our forests and lead them to more carbon capture. One of the ways to improve forests is to take tending operations. Tending operations are used to determine stand * Esra Bayar [email protected] Ayşe Deligöz [email protected] 1
Department of Forestry Engineering, Faculty of Forestry, Isparta University of Applied Sciences, 32260 Isparta, Turkey
density to improve wood quality and to grow trees (Mäkinen et al. 2006), namely prepare forests for future management operations. Thinning or removing trees from the forest is widely performed to produce more valuable and largediameter timber and also to reduce competition among the remaining trees and maintain a
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