Effects of experimental warming on phenology, growth and gas exchange of treeline birch (Betula utilis) saplings, Eastern Tibetan Plateau, China |
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Authors: | Zhenfeng Xu Tingxing Hu and Yuanbin Zhang |
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Institution: | (1) Institute of Ecological Forestry, Sichuan Agricultural University, Chengdu, 611830, China;(2) Faculty of Forestry, Sichuan Agricultural University, Ya’an, 625014, China;(3) Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China;(4) Key Laboratory of Forestry Ecological Engineering of Sichuan Province, Faculty of Forestry, Sichuan Agricultural University, Xingkang Road 46, Ya’an, Sichuan, 625014, China |
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Abstract: | Mountain birch (Betula utilis) is the most important treeline species in alpine forests of southwestern China. In order to understand the effects of future
warming on treeline birch, this study was conducted to examine the effects of experimental warming on leaf phenology, growth
and gas exchange of B. utilis saplings using the open top chamber (OTC) method in a treeline ecotone of eastern Tibetan Plateau. The OTCs enhanced daily
mean air temperature by 2.9 K throughout the growing season. Conversely, soil moisture within the OTCs on average declined
by 3% over the experimental period. Experimental warming did not affect the timing of bud break, although treeline birch saplings
growing in the OTCs manifested later leaf abscission, resulting in longer leaf life span. Artificial warming significantly
accelerated the leaf and shoot growth rates of treeline birch saplings, resulting in larger leaf area and longer shoot elongation
late in the growing season. Moreover, experimental warming significantly reduced the leaf fluctuating asymmetry (FA) and tended
to increase specific leaf area (SLA). Moreover, elevated temperatures significantly enhanced the transpiration rate (E), stomatal conductance (g
s), maximum net assimilation rate (A
max), dark respiration rate (R
d) and apparent quantum yield (AQY) but did not influence the light compensation point (LCP) and light saturation point (LSP)
of treeline birch saplings. Taken together, our results indicated that short-term experimental warming markedly altered structural/functional
leaf traits and enhanced photosynthetic capacity of treeline birch saplings; such positive responses in treeline birch would
be favorable for the growth of this species under future warmer world. |
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