Nina Ryzhkova, Alexander Kryshen, Zhou Wang, Jingye Li, Victor Voronin, Yves Bergeron, Rui Li, Jian-Guo Huang, Igor Drobyshev. 352 years long fire history of a Siberian boreal forest and its primary driving factor 2021. Global and Planetary Change 207:103653
DOI : 10.1016/j.gloplacha.2021.103653
Fire is a major disturbance agent in the boreal forest, affecting the structure, dynamics and biogeochemical cycles in this biome. In the Asian section of boreal forest, the records of long-term fire history are few that limits our understanding of factors forcing regional fire dynamics. We presented an annually-resolved 352-year (1666–2017) fire chronology based on fire scars of Scots pine (Pinus sylvestris L.) and Siberian larch (Larix sibirica Ledeb) from the Transbaikal area in the southeastern Siberia. Fire activity showed an increasing trend from 1720 to 1929 (R2 = 0.80, P < 0.0001), and a significant decreasing trend from 1920 to 2010 (R2 = 0.62, P < 0.001). We assessed the potential relationships between drought (as represented by the Palmer Drought Severity Index, PDSI, and the Monthly Drought Code, MDC), ocean-atmosphere circulation and forest fire by Superposed epoch analyses, cross-wavelet analysis and Granger causality analysis. Increased fire activity was associated with stronger drought from previous winter to current summer of fire event years and positive Arctic Oscillation (AO) before and during major fire season (February and April to May), as revealed by superposed epoch analysis. Granger causality pointed to the significant role of drought in driving forest fires. Our findings provide insights into the climate drivers of forest fire activity and its prediction in the Transbaikal region.
Jian Kang, Shaowei Jiang, Hanxue Liang, Shaokang Zhang, Jingye Li, Biyun Yu, Yves Bergeron, Sergio Rossi, Zhou Wang, Peng Zhou, Jian-Guo Huang, Jacques Tardif. Radial growth responses of two dominant conifers to climate in the Altai
Mountains, Central Asia. 2021. Agric. For. Meteorol. 298-299:108297
DOI : 10.1016/j.agrformet.2020.108297
The boreal forests of Central Asia play a vital role in biodiversity protection and regional economic development. It is important to study potential changes in the growth dynamics of boreal species in a context of global change. In this study, we developed a network of 34 tree-ring chronologies for two tree species, Siberian larch (Larix sibirica Ledeb.) and Siberian pine (Pinus sibirica Du Tour). The network extended across a large latitudinal gradient (45°N to 55°N). Principal component analysis (PCA) was used to detect spatial patterns in tree radial growth during a common period 1943–2004. Results indicated an obvious clustering pattern with chronologies being divided into a northeastern (NR) and a southwestern (SR) region. Bootstrapped correlation analyses of regional climate versus aggregated chronologies showed that tree radial growth in both regions was positively associated with summer temperature (June and July). Tree radial growth in the northeastern region was however positively associated with early spring precipitation and spring Palmer Drought Severity Index (PDSI) whereas, in the southwestern region, it was characterized by negative correlations with early summer precipitation and summer PDSI. The warm pool El Niño-Southern Oscillation (WP ENSO) and North Atlantic Oscillation (NAO) regulated tree radial growth through their influence on regional precipitation and temperature. Results suggest that tree radial growth in the region may decline with future projected climate change. This study provides a more comprehensive understanding to tree growth-climate associations across Central Asia.
Yves Bergeron, Filipe Campelo, Qianqian Ma, Yaling Zhang, Patrick Fonti, Annie Deslauriers, Eryuan Liang, Jian-Guo Huang, Harri Mäkinen, Walter Oberhuber, Cyrille B.K. Rathgeber, Roberto Tognetti, Václav Treml, Bao Yang, Lihong Zhai, Jiao-Lin Zhang, Serena Antonucci, J. Julio Camarero, Katarina Cufar, Martin De Luis, Alessio Giovannelli, Henri E. Cuny, Jožica Gricar, Andreas Gruber, Vladimír Gryc, Aylin Güney, Xiali Guo, Wei Huang, Tuula Jyske, Jakub Kašpar, Gregory King, Cornelia Krause, Audrey Lemay, Feng Liu, Fabio Lombardi, Edurne Martinez del Castillo, Hubert Morin, Cristina Nabais, Pekka Nöjd, Richard L. Peters, Peter Prislan, Antonio Saracino, Irene Swidrak, Hanuš Vavrcík, Joana Vieira, Biyun Yu, Shaokang Zhang, Qiao Zeng, Emanuele Ziaco, Sergio Rossi. REPLY TO ELMENDORF AND ETTINGER:
Photoperiodplaysadominantandirreplaceablerole
in triggering secondary growth resumption 2020. PNAS 117(52) 32865-32867
DOI : 10.1073/pnas.2019931117
Qianqian Ma, Sergio Rossi, Annie Deslauriers, Jian-Guo Huang, Yves Bergeron, Cornelia Krause, Hubert Morin. Photoperiod and temperature as dominant environmental drivers triggering secondary growth resumption in Northern Hemisphere conifers. Proceedings of the National Academy of Sciences. 2020. PNAS
DOI : 10.1073/pnas.2007058117
Wood formation consumes around 15% of the anthropogenic CO2 emissions per year and plays a critical role in long-term sequestration of carbon on Earth. However, the exogenous factors driving wood formation onset and the underlying cellular mechanisms are still poorly understood and quantified, and this hampers an effective assessment of terrestrial forest productivity and carbon budget under global warming. Here, we used an extensive collection of unique datasets of weekly xylem tissue formation (wood formation) from 21 coniferous species across the Northern Hemisphere (latitudes 23 to 67°N) to present a quantitative demonstration that the onset of wood formation in Northern Hemisphere conifers is primarily driven by photoperiod and mean annual temperature (MAT), and only secondarily by spring forcing, winter chilling, and moisture availability. Photoperiod interacts with MAT and plays the dominant role in regulating the onset of secondary meristem growth, contrary to its as-yet-unquantified role in affecting the springtime phenology of primary meristems. The unique relationships between exogenous factors and wood formation could help to predict how forest ecosystems respond and adapt to climate warming and could provide a better understanding of the feedback occurring between vegetation and climate that is mediated by phenology. Our study quantifies the role of major environmental drivers for incorporation into state-of-the-art Earth system models (ESMs), thereby providing an improved assessment of long-term and high-resolution observations of biogeochemical cycles across terrestrial biomes.
Lei Chen, Qianqian Ma, Heikki Hänninen, Yves Bergeron, Jian-Guo Huang, Francine Tremblay. Long-term changes in the impacts of global warming on leaf phenology of four temperate tree species. 2019. Global Change Biology 25(3):997-1004
DOI : 10.1111/gcb.14496
Contrary to the generally advanced spring leaf unfolding under global warming, the effects of the climate warming on autumn leaf senescence are highly variable with advanced, delayed, and unchanged patterns being all reported. Using one million records of leaf phenology from four dominant temperate species in Europe, we investigated the temperature sensitivities of spring leaf unfolding and autumn leaf senescence (ST, advanced or delayed days per degree Celsius). The ST of spring phenology in all of the four examined species showed an increase and decrease during 1951–1980 and 1981–2013, respectively. The decrease in the ST during 1981–2013 appears to be caused by reduced accumulation of chilling units. As with spring phenology, the ST of leaf senescence of early successional and exotic species started to decline since 1980. In contrast, for late successional species, the ST of autumn senescence showed an increase for the entire study period from 1951 to 2013. Moreover, the impacts of rising temperature associated with global warming on spring leaf unfolding were stronger than those on autumn leaf senescence. The timing of leaf senescence was positively correlated with the timing of leaf unfolding during 1951–1980. However, as climate warming continued, the differences in the responses between spring and autumn phenology gradually increased, so that the correlation was no more significant during 1981–2013. Our results further suggest that since 2000, due to the decreased temperature sensitivity of leaf unfolding the length of the growing season has not increased any more. These finding needs to be addressed in vegetation models used for assessing the effects of climate change.
Yuyun Fu, Rui Li, Yves Bergeron, Yunfei Fu, Yu Wang, Zongting Gao, Jian-Guo Huang. Satellite-Observed Impacts of Wildfires on Regional
Atmosphere Composition and the Shortwave
Radiative Forcing: A Multiple Case Study. 2018. J. Geophys. Res. 123(15): 8326-8343
DOI : 10.1029/2017JD027927
Emissions of aerosols and trace gases from wildfires and their direct shortwave radiative forcing (DSRF) at the top of atmosphere were studied using satellite observations from Moderate?Resolution Imaging Spectroradiometer, Atmospheric Infrared Sounder, Clouds and Earth Radiant Energy System on Aqua, and Ozone Monitoring Instrument on Aura. The dominant fuel types of the selected fire cases in the northeast of China (NEC), Siberia (Russia), and California (USA) are cropland, mixed forest, and needle?leaf forest, respectively. For the cropland fire case in NEC, the fire radiative power?based emission coefficients (Ce) of aerosol is 20.51 ± 2.55 g/MJ, half that of the forest fire cases in Siberia (40.01 ± 9.21 g/MJ) and California (45.23 ± 8.81 g/MJ), and the carbon monoxide (CO) Ce (23.94 ± 11.83 g/MJ) was about one third and half that of the forest fire cases in Siberia and California, respectively. However, the NOx (NO2 + NO) Ce (2.76 ± 0.25g MJ?1) of the cropland fire in NEC was nearly 3 times that of those forest fire cases. Ratios of NOx to aerosol, HCHO, and CO in the cropland case in NEC show much higher values than those in the forest fire cases. Despite the differences of the Ce and the composition ratios, the DSRF efficiency of smoke aerosol at the top of atmosphere showed similar values among those fire cases. Our results highlight the large variability of emission rate and relative chemical composition but similar DSRF efficiencies among wildfires, which would provide valuable information for understanding the impact of fire on air quality and climate.
Lei Chen, Qianqian Ma, Heikki Hänninen, Sergio Rossi, Shilong Piao, Yves Bergeron, Jian-Guo Huang. Spring phenology at different altitudes is becoming more
uniform under global warming in Europe. 2018. Global Change Biology 24(9):3969-3975
DOI : 10.1111/gcb.14288
Under current global warming, high-elevation regions are expected to experience
faster warming than low-elevation regions. However, due to the lack of studies
based on long-term large-scale data, the relationship between tree spring phenology
and the elevation-dependent warming is unclear. Using 652k records of leaf unfolding
of five temperate tree species monitored during 1951–2013 in situ in Europe,
we discovered a nonlinear trend in the altitudinal sensitivity (SA, shifted days per
100 m in altitude) in spring phenology. A delayed leaf unfolding (2.7 0.6 days per
decade) was observed at high elevations possibly due to decreased spring forcing
between 1951 and 1980. The delayed leaf unfolding at high-elevation regions was
companied by a simultaneous advancing of leaf unfolding at low elevations. These
divergent trends contributed to a significant increase in the SA (0.36 0.07 days
100/m per decade) during 1951–1980. Since 1980, the SA started to decline with a
rate of 0.32 0.07 days 100/m per decade, possibly due to reduced chilling at
low elevations and improved efficiency of spring forcing in advancing the leaf
unfolding at high elevations, the latter being caused by increased chilling. Our
results suggest that due to both different temperature changes at the different altitudes,
and the different tree responses to these changes, the tree phenology has
shifted at different rates leading to a more uniform phenology at different altitudes
during recent decades.
Yves Bergeron, Guillermo Gea Izquierdo, Marie-Pierre Lapointe-Garant, J. Grace, Jian-Guo Huang, Frank Berninger. The relationship between productivity and tree-ring growth in boreal coniferous forests. 2014. Boreal Environment Research 19(5-6):363-378
Ecosystem productivity estimated with a model calibrated with eddy-covariance data was related to tree-ring growth of two different boreal conifers along a latitudinal gradient. The relationship between ecosystem productivity and growth changed with species and site. Greater photosynthesis in spring and summer increased annual anomalies of radial growth in both species, and the response of growth to productivity was earlier in warmer southern stands particularly for pine. Radial growth of jack pine increased in the long-term with higher productivity, whereas this relationship was more reduced in black spruce. This could express species-specific differences in carbon allocation strategies but likely it is a consequence of the limiting marginal soils where spruce is found in the south. Only tree-rings of jack pine at some sites showed certain potential as direct proxies for ecosystem productivity at the low and high-frequency responses. Introduction Climate warming and the increase in atmos-pheric-CO 2 concentrations cause changes in forest growth and ecosystem productivity. There are reports of contrasting growth responses to warming over recent decades in different types of forests. Although some boreal species show negative growth trends in response to recent climate change (Hoofgaard et al. 1999, D'Arrigo et al. 2004), net ecosystem productivity in boreal and temperate conditions is generally expected to increase with increasing temperatures (Myneni et al. 1997, Boisvenue and Running 2006). Forest growth measurements and models assume that there is a close connection between the stem
Yves Bergeron, Lihong Zhai, Frank Berninger, Jian-Guo Huang, Bernhard Denneler, Jacques Tardif. Impact of Future Climate on Radial Growth of Four Major Boreal Tree Species in the Eastern Canadian Boreal Forest. 2013. PlosOne
DOI : 10.1371/journal.pone.0056758
Immediate phenotypic variation and the lagged effect of evolutionary adaptation to climate change appear to be two key processes in tree responses to climate warming. This study examines these components in two types of growth models for predicting the 2010–2099 diameter growth change of four major boreal species Betula papyrifera, Pinus banksiana, Picea mariana, and Populus tremuloides along a broad latitudinal gradient in eastern Canada under future climate projections. Climate-growth response models for 34 stands over nine latitudes were calibrated and cross-validated. An adaptive response model (A-model), in which the climate-growth relationship varies over time, and a fixed response model (F-model), in which the relationship is constant over time, were constructed to predict future growth. For the former, we examined how future growth of stands in northern latitudes could be forecasted using growth-climate equations derived from stands currently growing in southern latitudes assuming that current climate in southern locations provide an analogue for future conditions in the north. For the latter, we tested if future growth of stands would be maximally predicted using the growth-climate equation obtained from the given local stand assuming a lagged response to climate due to genetic constraints. Both models predicted a large growth increase in northern stands due to more benign temperatures, whereas there was a minimal growth change in southern stands due to potentially warm-temperature induced drought-stress. The A-model demonstrates a changing environment whereas the F-model highlights a constant growth response to future warming. As time elapses we can predict a gradual transition between a response to climate associated with the current conditions (F-model) to a more adapted response to future climate (A-model). Our modeling approach provides a template to predict tree growth response to climate warming at mid-high latitudes of the Northern Hemisphere.
Yves Bergeron, Lihong Zhai, Frank Berninger, Jian-Guo Huang. Variation in intra-annual wood formation, and foliage and shoot development of three major Canadian boreal tree species. 2012. American Journal of Botany. 99(5):827-837
DOI : 10.3732/ajb.1100235
• Premise of the study: In a warming climate, boreal trees may have adjusted their growth strategy (e.g., onset and coordination of growth among different organs such as stem, shoot, and foliage, within and among species) to cope with the extended growing seasons. A detailed investigation into growth of different organs during a growing season may help us assess the potential effects of climate change on tree growth in the boreal forest.
• Methods: The intra-annual growth of stem xylem, shoot tips, and foliage area of Pinus banksiana, Populus tremuloides, and Betula papyrifera was monitored in a boreal forest in Quebec, Canada during the growing season of 2007. Xylem formation was measured at weekly intervals, and shoot elongation and foliage expansion were measured three times per week from May to September. Growth indices for stem, shoot, and foliage were calculated and used to identify any climate–growth dependence.
• Key results: The time periods required for stem growth, branch extension, and foliage expansion differed among species. Of the three species, P. banksiana had the earliest budburst (20 May) yet the latest completion date of the foliage growth (2 August); P. tremuloides had the latest budburst (27 May) yet the earliest completion date of the foliage growth (10 July). Air temperature positively affected shoot extension growth of all three species. Precipitation positively influenced stem growth of the two broadleaf species, whereas growing season temperature positively impacted stem growth of P. banksiana.
• Conclusion: The results show that both the timing of growth processes and environmental dependences differ among co-occurring species, thereby leading to different adaptive capability of these boreal tree species to climate change.
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Jian-Guo Huang, Yves Bergeron, Jacques Tardif, Bernhard Denneler, Frank Berninger, Martin-Philippe Girardin. Response of four major boreal tree species to climate warming along a latitudinal gradient in western Quebec, Canada.
1st American Dendro Conference, Vancouver, BC.
Jian-Guo Huang, Yves Bergeron, Bernhard Denneler, Jacques Tardif. Dendroclimatological analyses of trembling aspen (Populus tremuloides Michx.) along a latitudinal gradient in western Quebec, Canada.
7th International Conference on Dendrochronology, Beijing, China.
