Guoju Wu

Northwest Institute of Eco-Environment and Resources

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Guobao Xu

Northwest Institute of Eco-Environment and Resources

Xiaomin Zeng

Shaanxi Normal University

Wenzhi Wang

Aerospace Information Research Institute

Tuo Chen

Chinese Academy of Sciences

Bo Wang

Zhejiang Academy of Forestry

Xiaohong Liu

Shaanxi Normal University

Xiaohong Liu

Shaanxi Normal University

Xuanwen Zhang

Fudan University

Wenling An

Institute of Geology and Geophysics

Weizhen Sun

China University of Petroleum, East China

Cooperative Institutions

Chinese Academy of Sciences

Northwest Institute of Eco-Environment and Resources

University of Chinese Academy of Sciences

Institute of Tibetan Plateau Research

Shaanxi Normal University

Lanzhou University

China Meteorological Administration

Northwest A&F University

University of Arizona

Center for Excellence in Tibetan Plateau Earth Sciences

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Elevation-dependent variations of tree growth and intrinsic water-use efficiency in Schrenk spruce (Picea schrenkiana) in the western Tianshan Mountains, China

Frontiers in Plant Science (2015)

Guoju Wu Xiaohong Liu Tuo Chen Guobao Xu Wenzhi Wang

Rising atmospheric CO2 concentration (C a) is expected to accelerate tree growth by enhancing photosynthesis and increasing intrinsic water-use efficiency (iWUE). However, the extent of this effect on long-term iWUE and its interactions with climate remains unclear in trees along an elevation gradient. Therefore, we investigated the variation in the radial growth and iWUE of mature Picea schrenkiana trees located in the upper tree-line (A1: 2700 m a.s.l.), middle elevation (A2: 2400 m a.s.l.), and lower forest limit (A3: 2200 m a.s.l.), in relation to the rising C a and changing climate in the Wusun Mountains of northwestern China, based on the basal area increment (BAI) and tree-ring δ(13)C chronologies from 1960 to 2010. We used the CRU TS3.22 dataset to analyze the general response of tree growth to interannual variability of regional climate, and found that BAI and δ(13)C are less sensitive to climate at A1 than at A2 and A3. The temporal trends of iWUE were calculated under three theoretical scenarios, as a baseline for interpreting the observed gas exchange at increasing C a. We found that iWUE increased by 12-32% from A1 to A3 over the last 50 years, and showed an elevation-dependent variation in physiological response. The significant negative relationship between BAI and iWUE at A2 and A3 showed that tree growth has been decreasing despite long-term increases in iWUE. However, BAI remained largely stable throughout the study period despite the strongest iWUE increase [at constant intercellular CO2 concentration (C i) before 1980] at A1. Our results indicate a drought-induced limitation of tree growth response to rising CO2 at lower elevations, and no apparent change in tree growth and diminished iWUE improvement since 1980 in the upper tree-line. This study may contradict the expectation that combined effects of elevated C a and rising temperatures have increased forest productivity, especially in high-elevation forests.

Basal area

Elevation (ballistics)

Tree line

10.3389/fpls.2015.00309

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Citations (68)

Tree‐ring δ¹⁸O evidence for the drought history of eastern Tianshan Mountains, northwest China since 1700 AD

International Journal of Climatology (2013)

Guobao Xu Xiaohong Liu Dahe Qin Tuo Chen Wenzhi Wang

ABSTRACT We developed an annual tree‐ring δ 18 O chronology from Larix sibirica in the eastern Tianshan Mountains of northwestern China. Climatic response revealed that tree‐ring δ 18 O was significantly positively correlated with the mean and maximum July–August temperatures, whereas the July precipitation and relative humidity were significantly negatively correlated with tree‐ring δ 18 O . The self‐calibrating Palmer drought severity index (sc_PDSI) in July–August was significantly correlated with the tree‐ring δ 18 O , which reflects the comprehensive effects of the three parameters on tree‐ring δ 18 O fractionation. We established a robust reconstruction of July–August sc_ PDSI that accounted for 38.4% of the total variance of sc_PDSI from 1959 to 2008. The sc_PDSI reconstruction yields new insights on past drought that were not previously realized in other PDSI reconstructions (e.g. Monsoon Asia Drought Atlas) from the region. The reconstruction revealed several wet and dry periods but no trend towards a wetter climate in the eastern Tianshan Mountains during the last two decades. It also detected synergistic effects of the North Atlantic Oscillation and the El Niño‐Southern Oscillation on regional moisture conditions as a result of teleconnections between tropical oceans and mid‐latitude circulation patterns.

Teleconnection

Chronology

10.1002/joc.3911

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A shift in cloud cover over the southeastern Tibetan Plateau since 1600: evidence from regional tree-ring δ18O and its linkages to tropical oceans

Quaternary Science Reviews (2014)

Xiaohong Liu Guobao Xu Jussi Grießinger Wenling An Wenzhi Wang

δ18O

Chronology

Forcing (mathematics)

10.1016/j.quascirev.2014.01.009

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Citations (53)

No altitude‐dependent effects of climatic signals are recorded in Smith fir tree‐ring δ¹⁸O on the southeastern Tibetan Plateau, despite a shift in tree growth

Boreas (2013)

Xiaomin Zeng Xiaohong Liu Wenzhi Wang Guobao Xu Wenling An

To reveal the influence of current warming on tree growth and δ 18 O in a sensitive high‐latitude region that is undergoing rapid climate change, we examined tree width and the earlywood and latewood δ 18 O at two sites with a 400‐m elevation difference in the S ygera M ountains of the southeastern T ibetan P lateau. The study period was from 1950 to 2011. The mean tree‐ring index at the low site was higher than that at the high site during the study period. The climatic responses of earlywood and latewood δ 18 O at both sites were similar. Earlywood δ 18 O was mainly influenced by the J une to A ugust temperature and total cloud cover, whereas latewood δ 18 O was mainly controlled by relative humidity from J uly to A ugust. Spatial correlations with CRU TS 3.1 regional data suggest that our δ 18 O chronologies can represent climatic changes over large regions. The high offset between earlywood δ 18 O at the two sites (2.3‰ higher at the low site) was mainly influenced by the high temperature lapse rate as a function of altitude during the earlywood growing season. Furthermore, meltwater with lower δ 18 O values might have affected earlywood δ 18 O at the high site, and thereby increased the earlywood δ 18 O offset between two sites. The low latewood δ 18 O offset between the two sites (0.4‰ higher at the low site) was not significant, but appears to have been primarily influenced by the low precipitation δ 18 O lapse rate as a function of altitude during the latewood growing season. Earlywood δ 18 O of S mith fir suitable for reconstructing past temperatures and latewood δ 18 O suitable for reconstructing past relative humidity on the southeastern T ibetan P lateau were identified.

10.1111/bor.12053

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Citations (15)

Nitrogen rather than streamflow regulates the growth of riparian trees

Chemical Geology (2020)

Keyi Wang Xiaomin Zeng Xiaohong Liu Matthew Lanning Guoju Wu

δ18O

δ15N

10.1016/j.chemgeo.2020.119666

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Citations (1)

Increased mercury pollution revealed by tree rings from the China’s Tianshan Mountains

Science Bulletin (2018)

Huhu Kang Liu Xiao-hong Junming Guo Guobao Xu Guoju Wu

Mercury

Mercury pollution

10.1016/j.scib.2018.09.010

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Citations (18)

[Mercury in tree rings: Advances, problems and prospects].

PubMed (2021)

Huhu Kang Xiaohong Liu Xinyu Zhang Junming Guo Guoju Wu

As a highly biotoxic element, mercury (Hg) can be enriched by the food chain and has negative effect on ecosystems. Changes of Hg flux and reserves in forest have important effects on its biogeochemical cycle in forest ecosystem. Due to limitation of temporal and spatial monitoring, there is not comprehensive understanding on Hg distribution. Widely distributed trees can be used as effective bio-monitors and Hg records in tree rings can be used to study Hg temporal and spatial distribution. Hg accumulated by root, leaf, bark, and other tissues can be detained in bole and record environmental Hg variations. Therefore, historical Hg trends can be restructured by analyzing Hg concentration in tree rings and the biogeochemical characteristics can be understood with Hg isotope ratio. We reviewed the method of measurement of Hg concentration and isotope ratio and application of reconstruction using Hg concentration in tree ring. We suggested the great application potential of Hg isotope ratio in atmospheric Hg construction and biogeochemistry cycle and raised concerns in further studies.汞作为生物毒性较强的金属元素之一,通过食物链富集进而威胁生态系统健康。汞在森林生态系统中的通量以及储量变化成为汞地球化学循环的重要影响因素。受汞监测记录的时空分布限制,对汞的时空分布变化认识尚不全面。分布广泛的树木是环境汞污染的有效生物监测器之一,能够利用树轮中的汞记录开展汞的时空分布变化研究。环境中的汞通过根系、叶片、树皮等组织吸收富集,最终在树木年轮中得以保存。因此,树轮能够重建污染历史并根据同位素比率反映地球化学循环特征。本文综述树木年轮汞浓度和汞同位素比率测量方法以及树轮汞浓度重建的应用,探讨树轮汞同位素记录在环境重建中以及森林生态系统汞的地球化学循环研究潜力,指出今后研究需要关注的问题。.

Biogeochemical Cycle

Mercury

Biogeochemistry

10.13287/j.1001-9332.202110.003

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Citations (0)

Contrasting growth responses of Qilian juniper (Sabina przewalskii) and Qinghai spruce (Picea crassifolia) to CO2 fertilization despite common water-use efficiency increases at the northeastern Qinghai–Tibetan plateau

Tree Physiology (2020)

Wenzhi Wang Nate G. McDowell Xiaohong Liu Guobao Xu Guoju Wu

Rising atmospheric carbon dioxide (CO2) may enhance tree growth and mitigate drought impacts through CO2 fertilization. However, multiple studies globally have found that rising CO2 has not translated into greater tree growth despite increases in intrinsic water-use efficiency (iWUE). The underlying mechanism discriminating between these two general responses to CO2 fertilization remains unclear. We used two species with contrasting stomatal regulation, the relatively anisohydric Qilian juniper (Sabina przewalskii) and the relatively isohydric Qinghai spruce (Picea crassifolia), to investigate the long-term tree growth and iWUE responses to climate change and elevated CO2 using tree ring widths and the associated cellulose stable carbon isotope ratios (δ13C). We observed a contrasting growth trend of juniper and spruce with juniper growth increasing while the spruce growth declined. The iWUE of both species increased significantly and with similar amplitude throughout the trees' lifespan, though the relatively anisohydric juniper had higher iWUE than the relatively isohydric spruce throughout the period. Additionally, with rising CO2, the anisohydric juniper became less sensitive to drought, while the relatively isohydric spruce became more sensitive to drought. We hypothesized that rising CO2 benefits relatively anisohydric species more than relatively isohydric species due to greater opportunity to acquire carbon through photosynthesis despite warming and droughts. Our findings suggest the CO2 fertilization effect depends on the isohydric degree, which could be considered in future terrestrial ecosystem models.

Water Use Efficiency

10.1093/treephys/tpaa169

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Citations (27)

Differential response of Qilian juniper radial growth to climate variations in the middle of Qilian Mountains and the northeastern Qaidam Basin

Climatic Change (2015)

Wenzhi Wang Xiaohong Liu Xuemei Shao Dahe Qin Guobao Xu

Dendroclimatology

10.1007/s10584-015-1467-2

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Citations (10)

Age-dependent impacts of climate change and intrinsic water-use efficiency on the growth of Schrenk spruce (Picea schrenkiana) in the western Tianshan Mountains, China