title: Topography and age mediate the growth responses of Smith fir to climate warming in the southeastern Tibetan Plateau.
abstract: The Tibetan Plateau holds some of the world's highest undisturbed natural treelines and timberlines. Such extreme environments constitute potentially valuable monitoring sites of the effects of climate warming on high-elevation forests. Here, we analyze a network of 21 Smith fir forests situated in the Sygera Mountains, southeastern Tibetan Plateau, using tree-ring width (TRW) and basal area increment (BAI) chronologies. Sampled sites encompassed a wide elevation gradient, from 3600 to 4400 m, including some treeline sites and diverse aspects and tree ages. In comparison with TRW series, BAI series better capture the long-term warming signal. Previous November and current April and summer temperatures are the dominant climatic factors controlling Smith fir radial growth. The mean inter-series correlations of TRW increased upwards, but the forest limit presented the highest potential to reconstruct past temperature variability. Moreover, the growth responses of young trees were less stable than those of trees older than 100 years. Climate warming is accelerating radial growth of Smith fir forest subjected to mesic conditions. Collectively, these findings confirm that the effects of site elevation and tree age should be considered when quantifying climate-growth relationships. The type of tree-ring data (BAI vs. TRW) is also relevant since BAI indices seem to be a better climatic proxy of low-frequency temperature signals than TRW indices. Therefore, site (e.g., elevation) and tree (e.g., age) features should be considered to properly evaluate the effects of climate warming on growth of high-elevation forests.
authors.affiliation: Key Laboratory of Alpine Ecology and Biodiversity, Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100101, China.|College of Urban and Environmental Sciences, Northwest University, Xi'an, 710127, China.
authors.forename: B
authors.initials: B
authors.lastname: Liu
authors.affiliation: Key Laboratory of Alpine Ecology and Biodiversity, Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100101, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Key Laboratory of Alpine Ecology and Biodiversity, Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100101, China.|CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing, 100101, China.
authors.forename: H
authors.initials: H
authors.lastname: Zhu
authors.affiliation: Key Laboratory of Alpine Ecology and Biodiversity, Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100101, China. liangey@itpcas.ac.cn.|CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing, 100101, China. liangey@itpcas.ac.cn.
authors.forename: E
authors.initials: E
authors.lastname: Liang
authors.affiliation: Instituto Pirenaico de Ecología (IPE-CSIC), Avda. Montañana, 1005, 50059, Zaragoza, Spain.
authors.forename: J J
authors.initials: JJ
authors.lastname: Camarero
mesh_terms: D028202:Abies / Q000254:growth & development*; D000531:Altitude; D002980:Climate; D057231:Climate Change; D065928:Forests; D012621:Seasons; D018609:Tibet
keywords: Basal area increment; Dendroecology; Southeastern Tibetan Plateau; Topography; Tree age; Tree-ring