Using X-ray CT based tree-ring width data for tree growth trend analysis

The climate of Nepal has changed rapidly over the recent decades, but most instrumental records of weather and hydrology only extend back to the 1980s. Tree rings can provide a longer perspective on recent environmental changes, and since the early 2000s, a new round of field initiatives by international researchers and Nepali scientists have more than doubled the size of the country’s tree-ring network. In this paper, we present a comprehensive analysis of the current tree-ring width network for Nepal, and use this network to estimate changes in forest growth nation-wide during the last four centuries. Ring-width chronologies in Nepal have been developed from 11 tree species, and half of the records span at least 290 years. The Nepal tree-ring width network provides a robust estimate of annual forest growth over roughly the last four centuries, but prior to this point, our mean ring-width composite fluctuates wildly due to low sample replication. Over the last four centuries, two major events are prominent in the all-Nepal composite: (i) a prolonged and widespread growth suppression during the early 1800s; and (ii) heightened growth during the most recent decade. The early 19th century decline in tree growth coincides with two major Indonesian eruptions, and suggests that short-term disturbances related to climate extremes can exert a lasting influence on the vigor of Nepal’s forests. Growth increases since AD 2000 are mainly apparent in high-elevation fir, which may be a consequence of the observed trend towards warmer temperatures, particularly during winter. This synthesis effort should be useful to establish baselines for tree-ring data in Nepal and provide a broader context to evaluate the sensitivity or behavior of this proxy in the central Himalayas.

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Development of tree-ring width chronologies and tree-growth response to climate in the mountains surrounding the Issyk-Kul Lake, Central Asia

Dendrochronologia ◽

10.1016/j.dendro.2014.03.002 ◽

2014 ◽

Vol 32 (3) ◽

pp. 230-236 ◽

Cited By ~ 14

Author(s):

Tongwen Zhang ◽

Yujiang Yuan ◽

Qing He ◽

Wenshou Wei ◽

Mamatkanov Diushen ◽

...

Keyword(s):

Central Asia ◽

Tree Ring ◽

Tree Growth ◽

Growth Response ◽

Ring Width ◽

Tree Ring Width

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Assimilation of Pseudo-Tree-Ring-Width observations into an Atmospheric General Circulation Model

10.5194/cp-2016-92 ◽

2016 ◽

Cited By ~ 1

Author(s):

Walter Acevedo ◽

Bijan Fallah ◽

Sebastian Reich ◽

Ulrich Cubasch

Keyword(s):

Tree Ring ◽

Tree Growth ◽

General Circulation ◽

Climate Model ◽

Global Climate Model ◽

Ring Width ◽

Circulation Model ◽

Forward Model ◽

Limiting Factors ◽

Tree Ring Width

Abstract. We investigate the assimilation of Tree-Ring-Width (TRW) chronologies into an atmospheric global climate model using Ensemble Kalman Filter (EnKF) techniques and a process-based tree-growth forward model as observation operator. Our results, within a perfect-model experiment setting, indicate that the non-linear response of tree-growth to surface temperature and soil moisture does deteriorate the operation of the time-averaged (EnKF) methodology. Moreover, this skill loss appeared significantly sensitive to the structure of growth rate function, used to represent the Principle of Limiting Factors (PLF)s within the forward model. On the other hand, it was observed that the error reduction achieved by assimilating a particular pseudo-TRW chronology is modulated by the strength of the yearly internal variability of the model at the chronology site. This result might help the dendrochronology community to optimize their sampling efforts. In our experiments, the ''online'' (with cycling) paleao Data Assimilation (DA) approach did not outperform the ''offline'' (no-cycling) one, despite its considerable additional implementation complexity.

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On the ‘Divergence Problem’ in the Alatau Mountains, Central Asia: A Study of the Responses of Schrenk Spruce Tree-Ring Width to Climate under the Recent Warming and Wetting Trend

Atmosphere ◽

10.3390/atmos10080473 ◽

2019 ◽

Vol 10 (8) ◽

pp. 473 ◽

Cited By ~ 3

Author(s):

Zhang ◽

Jiang ◽

Bagila ◽

Ainur ◽

...

Keyword(s):

Central Asia ◽

Tree Ring ◽

Tree Growth ◽

Tree Species ◽

Climatic Factors ◽

Ring Width ◽

Tree Ring Width ◽

Recent Warming ◽

Divergence Problem ◽

The Stability

The divergence problem, which manifests as an unstable response relationship between tree-ring growth and climatic factors under the background of global warming, poses a challenge to both the traditional theory of dendroclimatology and the reliability of climatic reconstructions based on tree-ring data. Although Schrenk spruce, as the dominant tree species in the Tianshan Mountains, is frequently applied in the dendrochronological studies, the understanding of the divergence problem of this tree species is still limited. This study conducted correlation analysis between climatic factors and tree-ring width chronologies from 51 living and healthy specimens of Schrenk spruce at sites of high and low elevation in the Alatau Mountains to determine the stability of the response. The results revealed that the tree-ring width of the spruce specimens was correlated positively with precipitation and correlated negatively with temperature. Although the variations of the two tree-ring chronologies were similar, the radial growth of the spruce at the low elevation was found more sensitive to climatic factors. Furthermore, the sensitivity of tree growth to climate demonstrated an obvious increase after an abrupt change of climate under the background of the recent warming and wetting trend. Increased drought stress, calculated based on climatic data, was regarded as the main reason for this phenomenon. The results supply the gap of the stability of climatic response of tree growth in Central Asia to some extent.

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Assimilation of pseudo-tree-ring-width observations into an atmospheric general circulation model

Climate of the Past ◽

10.5194/cp-13-545-2017 ◽

2017 ◽

Vol 13 (5) ◽

pp. 545-557 ◽

Cited By ~ 9

Author(s):

Walter Acevedo ◽

Bijan Fallah ◽

Sebastian Reich ◽

Ulrich Cubasch

Keyword(s):

Tree Ring ◽

Tree Growth ◽

General Circulation ◽

Climate Model ◽

Global Climate Model ◽

Ring Width ◽

Circulation Model ◽

Forward Model ◽

Limiting Factors ◽

Tree Ring Width

Abstract. Paleoclimate data assimilation (DA) is a promising technique to systematically combine the information from climate model simulations and proxy records. Here, we investigate the assimilation of tree-ring-width (TRW) chronologies into an atmospheric global climate model using ensemble Kalman filter (EnKF) techniques and a process-based tree-growth forward model as an observation operator. Our results, within a perfect-model experiment setting, indicate that the "online DA" approach did not outperform the "off-line" one, despite its considerable additional implementation complexity. On the other hand, it was observed that the nonlinear response of tree growth to surface temperature and soil moisture does deteriorate the operation of the time-averaged EnKF methodology. Moreover, for the first time we show that this skill loss appears significantly sensitive to the structure of the growth rate function, used to represent the principle of limiting factors (PLF) within the forward model. In general, our experiments showed that the error reduction achieved by assimilating pseudo-TRW chronologies is modulated by the magnitude of the yearly internal variability in the model. This result might help the dendrochronology community to optimize their sampling efforts.

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Retrospective Analysis of Tree Decline Based on Intrinsic Water-Use Efficiency in Semi-Arid Areas of North China

Atmosphere ◽

10.3390/atmos11060577 ◽

2020 ◽

Vol 11 (6) ◽

pp. 577

Author(s):

Weiwei Lu ◽

Xinxiao Yu ◽

Guodong Jia

Keyword(s):

Climate Change ◽

Tree Ring ◽

Tree Growth ◽

North China ◽

Isotope Composition ◽

Ring Width ◽

Carbon Isotope Composition ◽

Tree Decline ◽

Tree Ring Width

Long-term tree growth is significantly affected by climate change, which have become a global concern. Tree-ring width and isotopic information can show how trees respond to climate change on a long-term scale and reveal some phenomena of tree decline or death. In this study, we used isotopic techniques and investigated annual changes in carbon isotope composition and tree-ring width of Populus simonii Carr. in Zhangbei, as well as trends in tree-ring carbon discrimination (Δ13C) and iWUE in normal, mildly declining and severely declining trees, in order to make a retrospective analysis and further understand the process of tree decline. We found that there were significant differences (p < 0.01 **) in δ13C, Δ13C, ci and iWUE at different decline stages, meaning that the δ13C and iWUE could be new indicators of tree health. The iWUE of all groups increased significantly, while the growth rate of declined P. simonii was much higher than that of normal growth P. simonii. According to the analysis, there may be a threshold of iWUE for healthy trees, which once the threshold value is exceeded, it indicates that trees are resistant to adversity and their growth is under stress. Similarly, the changing trend of BAI supports our conclusion with its changes showed that tree growth became slower and slower as degradation progressed. iWUE inferred from tree-ring stable carbon isotope composition is a strong modulator of adaptation capacity in response to environmental stressors under climate change. Elevated annual temperatures and increased groundwater depth are all contributing to the decline of P. simonii in north China.

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Tree-ring responses to extreme climate events as benchmarks for terrestrial dynamic vegetation models

Biogeosciences Discussions ◽

10.5194/bgd-11-2537-2014 ◽

2014 ◽

Vol 11 (2) ◽

pp. 2537-2568 ◽

Cited By ~ 12

Author(s):

A. Rammig ◽

M. Wiedermann ◽

J. F. Donges ◽

F. Babst ◽

W. von Bloh ◽

...

Keyword(s):

Tree Ring ◽

Tree Growth ◽

Extreme Events ◽

Ring Width ◽

Climate Extremes ◽

Tree Ring Width ◽

Model Data ◽

Vegetation Models ◽

The Impact

Abstract. Climate extremes can trigger exceptional responses in terrestrial ecosystems, for instance by altering growth or mortality rates. Effects of this kind are often manifested in reductions of the local net primary production (NPP). Investigating a set of European long-term data on annual radial tree growth confirms this pattern: we find that 53% of tree ring width (TRW) indices are below one standard deviation, and up to 16% of the TRW values are below two standard deviations in years with extremely high temperatures and low precipitation. Based on these findings we investigate if climate driven patterns in long-term tree growth data may serve as benchmarks for state-of-the-art dynamic vegetation models such as LPJmL. The model simulates NPP but not explicitly the radial tree ring growth, hence requiring a generic method to ensure an objective comparison. Here we propose an analysis scheme that quantifies the coincidence rate of climate extremes with some biotic responses (here TRW or simulated NPP). We find that the reduction in tree-ring width during drought extremes is lower than the corresponding reduction of simulated NPP. We identify ten extreme years during the 20th century in which both, model and measurements indicate high coincidence rates across Europe. However, we detect substantial regional differences in simulated and observed responses to extreme events. One explanation for this discrepancy could be that the tree-ring data have preferentially been sampled at more climatically stressed sites. The model-data difference is amplified by the fact that dynamic vegetation models are designed to simulate mean ecosystem responses at landscape or regional scale. However, we find that both model-data and measurements display carry-over effects from the previous year. We conclude that using radial tree growth is a good basis for generic model-benchmarks if the data are analyzed by scale-free measures such as coincidence analysis. Our study shows strong reductions in carbon sequestration during extreme years. However, for a better understanding of the impact of extreme events on e.g. the long-term fate of the European carbon balance, more long-term measurement data and improved process-based models are needed.

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A triple tree-ring constraint for tree growth and physiology in a global land surface model

10.5194/bg-2020-446 ◽

2020 ◽

Author(s):

Jonathan Barichivich ◽

Philippe Peylin ◽

Thomas Launois ◽

Valerie Daux ◽

Camille Risi ◽

...

Keyword(s):

Tree Ring ◽

Tree Growth ◽

Land Surface ◽

Ring Width ◽

Land Surface Model ◽

Surface Model ◽

Tree Ring Width ◽

Leaf Physiology ◽

Global Land ◽

Temperate Europe

Abstract. Annually-resolved tree-ring records extending back to pre-industrial conditions have the potential to constrain the responses of global land surface models at interannual to centennial time scales. Here, we demonstrate a framework to constrain the representation of tree growth and physiology in the ORCHIDEE global land surface model using the simulated variability of tree-ring width and carbon (Δ13C) and oxygen (δ18O) stable isotopes in six sites in boreal and temperate Europe. We exploit the tree-ring triplet to derive integrative constraints for leaf physiology and growth from well-known mechanistic relationships among the variables. The model simulates Δ13C (r = 0.31–0.80) and δ18O (r = 0.36–0.74) better than tree-ring width (r

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MAIDENiso: a multiproxy biophysical model of tree-ring width and oxygen and carbon isotopes

Canadian Journal of Forest Research ◽

10.1139/x2012-089 ◽

2012 ◽

Vol 42 (9) ◽

pp. 1697-1713 ◽

Cited By ~ 19

Author(s):

P.-A. Danis ◽

C. Hatté ◽

L. Misson ◽

J. Guiot

Keyword(s):

Carbon Isotopes ◽

Tree Ring ◽

Tree Growth ◽

Extreme Values ◽

Ring Width ◽

Biophysical Model ◽

Biogeochemical Model ◽

Tree Ring Width ◽

Oxygen And Carbon Isotopes ◽

Annual Increment

MAIDENiso is a new version of the process-based biogeochemical model MAIDEN of tree growth. Isotopic modules have been implemented to simulate stable oxygen and carbon isotopes in tree-ring cellulose (TRC). In addition to annual increment biomass, this new model version estimates δ18O and δ13C associated with the daily amount of carbon allocated to the stem. MAIDENiso only requires daily input data: minimal and maximal air temperatures, amount of precipitation, CO2 atmospheric concentration, and δ13C in CO2. MAIDENiso simulates tree-ring width, δ18O in precipitation (δ18OP), δ18O in soil water (δ18OSW), δ18O in xylem water (δ18OXW), δ18O in cellulose (δ18OTRC), and δ13C in cellulose (δ13CTRC). The model has been calibrated and validated with tree-ring series sampled in the Fontainebleau Forest (France) from 1953 to 2000. We first calibrated several parameters for the 1977–2000 period and then validated it for the independent 1953–1976 period. Over the complete interval (1953–2000), we obtained correlations between observations and simulations above 0.5 for both isotopic series and above 0.65 for tree growth series. An important feature of the model is its ability to simulate not only extreme values of tree growth, such as the effect of 1976 drought, but also its persistence over several years.

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A model analysis of climate and CO<sub>2</sub> controls on tree growth in a semi-arid woodland

Biogeosciences Discussions ◽

10.5194/bgd-12-4769-2015 ◽

2015 ◽

Vol 12 (6) ◽

pp. 4769-4800

Author(s):

G. Li ◽

S. P. Harrison ◽

I. C. Prentice

Keyword(s):

Tree Ring ◽

Tree Growth ◽

Radial Growth ◽

Fine Root ◽

Carbon Allocation ◽

Ring Width ◽

Root Mass ◽

Tree Ring Width ◽

Use Efficiency ◽

Semi Arid

Abstract. We used a light-use efficiency model of photosynthesis coupled with a dynamic carbon allocation and tree-growth model to simulate annual growth of the gymnosperm Callitris columellaris in the semi-arid Great Western Woodlands, Western Australia, over the past 100 years. Parameter values were derived from independent observations except for sapwood specific respiration rate, fine-root turnover time, fine-root specific respiration rate and the ratio of fine-root mass to foliage area, which were estimated by Bayesian optimization. The model reproduced the general pattern of interannual variability in radial growth (tree-ring width), including the response to the shift in precipitation regimes that occurred in the 1960s. Simulated and observed responses to climate were consistent. Both showed a significant positive response of tree-ring width to total photosynthetically active radiation received and to the ratio of modeled actual to equilibrium evapotranspiration, and a significant negative response to vapour pressure deficit. However, the simulations showed an enhancement of radial growth in response to increasing atmospheric CO2 concentration (ppm) ([CO2]) during recent decades that is not present in the observations. The discrepancy disappeared when the model was recalibrated on successive 30-year windows. Then the ratio of fine-root mass to foliage area increases by 14% (from 0.127 to 0.144 kg C m-2) as [CO2] increased while the other three estimated parameters remained constant. The absence of a signal of increasing [CO2] has been noted in many tree-ring records, despite the enhancement of photosynthetic rates and water-use efficiency resulting from increasing [CO2]. Our simulations suggest that this behaviour could be explained as a consequence of a shift towards below-ground carbon allocation.

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