Controls of seed quantity and quality on seedling recruitment of smith fir along altitudinal gradient in southeastern Tibetan Plateau |
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Authors: | Jing-sheng Wang Ji-guang Feng Bao-xiong Chen Pei-li Shi Jun-long Zhang Jiang-ping Fang Zhi-kai Wang Shuai-chen Yao Lu-bin Ding |
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Affiliation: | 1.Lhasa Plateau Ecosystem Research Station, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research,Chinese Academy of Sciences,Beijing,China;2.School of Environment and Natural Resources,Renmin University of China,Beijing,China;3.Rural Energy & Environment Agency,Ministry of Agriculture of the People’s Republic of China,Beijing,China;4.National Center for Climate Change Strategy and International Cooperation,Beijing,China;5.Tibet Agricultural and Animal Husbandry College,Tibet Linzhi,China |
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Abstract: | Alpine treeline ecotones are harsh environment for tree establishment due to low temperature.Tree establishment at treelines requires favorable climate,suitable microsites,and viable seeds.But most researches have been addressed treeline microclimate and its effects on tree regeneration,the knowledge of seed quantity and quality and its controls on seedling recruitment were limited.We measured seed rain,soil seed bank,seed germination rate and seedling recruitment in natural forests in combination with seed transplanting manipulation to evaluate the controls of seed quantity and quality on seedling recruitment of Abies georgei var.smithii(smith fir) along altitudinal gradient,withfocus on treeline ecotone in the Sygera Mountains,southeastern Tibetan Plateau.Both seed quantity and seed quality of smith fir decreased with increasing altitude and was thereby associated with decline in seed germination rate.Seed quantity and seedling recruitment were better in north-facing slope than in south slope.The treeline ecotone above 4200 m appeared as the threshold altitude to sharply decrease seed quality and seedling recruitment.The emergence and overwintering rates of transplanting seeds from 3600-3800 m also went down remarkably above 4200 m at north-facing slope.It also underpins the fact that treeline ecotone is the bottleneck of seedling recruitment.Our results suggest that seed quantity and quality are the principal limitation of treeline upward advance.This study also provides evidence tosupport stable treeline position in southeastern Tibetan Plateau. |
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