Yaling Zhang, Jian-Guo Huang, Minhuang Wang, Xiaohan Yu, Annie Deslauriers, Patrick Fonti, Eryuan Liang, Harri Mäkinen, Walter Oberhuber, Cyrille B. K. Rathgeber, Roberto Tognetti, Václav Treml, Bao Yang, Lihong Zhai, Jiao-Lin Zhang, Serena Antonucci, Yves Bergeron, Jesus Julio Camarero, Filipe Campelo, Katarina Cufar, Henri E. Cuny, Martin De Luis, Marek Fajstavr, Alessio Giovannelli, Jožica Gricar, Andreas Gruber, Vladimír Gryc, Aylin Güney, 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, Vladimir V. Shishov, Irene Swidrak, Hanuš Vavrcík, Joana Vieira, Qiao Zeng, Yu Liu, Sergio Rossi. A critical thermal transition driving spring phenology of
Northern Hemisphere conifers. 2022. Global Change Biology 29(6):1606-1617
DOI : 10.1111/gcb.16543
Despite growing interest in predicting plant phenological shifts,advanced spring phenology by global climate change remains debated. Evidence documenting either small or large advancement of spring phenology to rising temperature over the spatio-temporal scales implies a potential existence of a thermal threshold in the responses of forests to global warming. We collected a unique data set of xylem cell-wall-thickening onset dates in 20 coniferous species covering a broad mean annual temperature (MAT) gradient (?3.05 to 22.9°C) across the Northern Hemisphere (latitudes 23°?66°?N). Along the MAT gradient,we identified a threshold temperature (using segmented regression) of 4.9?±?1.1°C,above which the response of xylem phenology to rising temperatures significantly decline. This threshold separates the Northern Hemisphere conifers into cold and warm thermal niches,with MAT and spring forcing being the primary drivers for the onset dates (estimated by linear and Bayesian mixed-effect models),respectively. The identified thermal threshold should be integrated into the Earth-System-Models for a better understanding of spring phenology in response to global warming and an improved prediction of global climate-carbon feedbacks.
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.
Shaokang Zhang, Valentina Buttò, Siddhartha Khare, Annie Deslauriers, Hubert Morin, Hai Ren, Jian-Guo Huang, Sergio Rossi. Calibrating PhenoCam Data with Phenological Observations of a Black Spruce Stand. 2020. Can. J. Remote Sensing 46(2):154-165
DOI : 10.1080/07038992.2020.1761251
Bud and leaf development are important phenological events and help in defining the growing period of trees. Canopy greenness derived from PhenoCam has been used to investigate leaf phenology. Questions remain on how much the continuous records of canopy greenness represent bud developmental phases, and how growing period boundaries are related to canopy greenness and bud phenology. In this study, we compared bud phenology of black spruce [Picea mariana (Mill.) B.S.P] during 2015, 2017 and 2018 with the canopy greenness, represented by Green Chromatic Coordinate (GCC), derived from PhenoCam images of a boreal stand in Quebec, Canada. Logit models were applied to estimate the probability of observing sequential phenological phases of bud burst and bud set along with GCC. GCC showed a bell-shaped pattern, with a slow increase in spring, a peak in summer and a gradual decrease in autumn. The start and end of budburst, and bud set, occurred when GCC reached 72% and 92% (spring), and 94% (autumn) of its maximum amplitude, respectively. These GCC values are reliable thresholds indicating the growing period boundaries. Our study builds a bridge between phenological observations and automatic near-surface remote sensing, providing a statistically sound protocol for calibrating PhenoCam with field observations.
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:
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.
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Yves Bergeron, Guillermo Gea Izquierdo, Marie-Pierre Lapointe-Garant, J. Grace, Frank Berninger, Jian-Guo Huang. 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
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.