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  • 1
    Language: English
    In: Tree physiology, 2012-05, Vol.32 (5), p.612-625
    Description: We investigated whether timing and rate of growth are related to the life strategies and fitness of three conifer species. Intra-annual dynamics of wood formation, shoot elongation and needle phenology were monitored over 3 years in five Norway spruces (Picea abies (L.) Karst.), five Scots pines (Pinus sylvestris L.) and five silver firs (Abies alba Mill.) grown intermixed. For the three species, the growing season (delimited by cambial activity onset and cessation) lasted about 4 months, while the whole process of wood formation lasted 5-6 months. Needle unfolding and shoot elongation followed the onset of cambial activity and lasted only one-third of the season. Pines exhibited an 'extensive strategy' of cambial activity, with long durations but low growth rates, while firs and spruces adopted an 'intensive strategy' with shorter durations but higher growth rates. We estimated that about 75% of the annual radial increment variability was attributable to the rate of cell production, and only 25% to its duration. Cambial activity rates culminated at the same time for the three species, whereas shoot elongation reached its maximal rate earlier in pines. Results show that species-specific life strategies are recognizable through functional traits of intra-annual growth dynamics. The opposition between Scots pine extensive strategy and silver fir and Norway spruce intensive strategy supports the theory that pioneer species are greater resource expenders and develop riskier life strategies to capture resources, while shade-tolerant species utilize resources more efficiently and develop safer life strategies. Despite different strategies, synchronicity of the maximal rates of cambial activity suggests a strong functional convergence between co-existing conifer species, resulting in head-on competition for resources.
    Subject(s): Pinus sylvestris - growth & development ; Plant Shoots - growth & development ; Species Specificity ; Time Factors ; Picea - growth & development ; Plant Leaves - growth & development ; Abies - growth & development ; Seasons ; Trees - growth & development ; France ; Wood - growth & development ; Index Medicus ; Life Sciences ; Agricultural sciences
    ISSN: 0829-318X
    E-ISSN: 1758-4469
    Source: Academic Search Ultimate
    Source: Oxford Journals 2016 Current and Archive A-Z Collection
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 2
    Language: English
    In: Global change biology, 2016-11, Vol.22 (11), p.3804-3813
    Description: The interaction between xylem phenology and climate assesses forest growth and productivity and carbon storage across biomes under changing environmental conditions. We tested the hypothesis that patterns of wood formation are maintained unaltered despite the temperature changes across cold ecosystems. Wood microcores were collected weekly or biweekly throughout the growing season for periods varying between 1 and 13 years during 1998–2014 and cut in transverse sections for assessing the onset and ending of the phases of xylem differentiation. The data set represented 1321 trees belonging to 10 conifer species from 39 sites in the Northern Hemisphere and covering an interval of mean annual temperature exceeding 14 K. The phenological events and mean annual temperature of the sites were related linearly, with spring and autumnal events being separated by constant intervals across the range of temperature analysed. At increasing temperature, first enlarging, wall‐thickening and mature tracheids appeared earlier, and last enlarging and wall‐thickening tracheids occurred later. Overall, the period of wood formation lengthened linearly with the mean annual temperature, from 83.7 days at −2 °C to 178.1 days at 12 °C, at a rate of 6.5 days °C−1. April–May temperatures produced the best models predicting the dates of wood formation. Our findings demonstrated the uniformity of the process of wood formation and the importance of the environmental conditions occurring at the time of growth resumption. Under warming scenarios, the period of wood formation might lengthen synchronously in the cold biomes of the Northern Hemisphere.
    Subject(s): cell production ; cell differentiation ; secondary wall formation ; cambium ; conifers ; meristem ; growth ; climate change ; Trees ; Cold Temperature ; Plant Development ; Xylem ; Ecosystem ; Coniferophyta ; Seasons ; Biomes ; Environmental aspects ; Global temperature changes ; Cell differentiation ; Ecosystems ; Analysis ; Index Medicus ; Life Sciences ; Vegetal Biology
    ISSN: 1354-1013
    E-ISSN: 1365-2486
    Source: Alma/SFX Local Collection
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 3
    Language: English
    In: Global change biology, 2019-03, Vol.25 (3), p.1089-1105
    Description: The phenology of wood formation is a critical process to consider for predicting how trees from the temperate and boreal zones may react to climate change. Compared to leaf phenology, however, the determinism of wood phenology is still poorly known. Here, we compared for the first time three alternative ecophysiological model classes (threshold models, heat‐sum models and chilling‐influenced heat‐sum models) and an empirical model in their ability to predict the starting date of xylem cell enlargement in spring, for four major Northern Hemisphere conifers (Larix decidua, Pinus sylvestris, Picea abies and Picea mariana). We fitted models with Bayesian inference to wood phenological data collected for 220 site‐years over Europe and Canada. The chilling‐influenced heat‐sum model received most support for all the four studied species, predicting validation data with a 7.7‐day error, which is within one day of the observed data resolution. We conclude that both chilling and forcing temperatures determine the onset of wood formation in Northern Hemisphere conifers. Importantly, the chilling‐influenced heat‐sum model showed virtually no spatial bias whichever the species, despite the large environmental gradients considered. This suggests that the spring onset of wood formation is far less affected by local adaptation than by environmentally driven plasticity. In a context of climate change, we therefore expect rising winter–spring temperature to exert ambivalent effects on the spring onset of wood formation, tending to hasten it through the accumulation of forcing temperature, but imposing a higher forcing temperature requirement through the lower accumulation of chilling. A temperature sum model influenced by chilling accumulation predicts the spring onset of xylem enlargement across temperate and boreal latitudes, in four major Northern Hemisphere conifers. This model outperformed heat‐sums and threshold models. On the figure, plots per species show predicted (coloured lines) and observed (grey dots) xylem onset dates, sorted by temperatures during the January–June period. The central plot shows the species‐specific relation between chilling and forcing accumulation.
    Subject(s): chilling temperatures ; forcing temperatures ; cambium ; conifers ; phenological models ; wood phenology ; Weather forecasting ; Analysis ; Biodiversity and Ecology ; Environmental Sciences ; Global Changes
    ISSN: 1354-1013
    E-ISSN: 1365-2486
    Source: Alma/SFX Local Collection
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  • 4
    Language: English
    In: Annals of botany, 2013-12-01, Vol.112 (9), p.1911-1920
    Description: • Background and Aims Ongoing global warming has been implicated in shifting phenological patterns such as the timing and duration of the growing season across a wide variety of ecosystems. Linear models are routiriely used to extrapolate these observed shifts in phenology into the future and to estimate changes in associated ecosystem properties such as net primary productivity. Yet, in nature, linear relationships may be special cases. Biological processes frequently follow more complex, non-linear patterns according to limiting factors that generate shifts and discontinuities, or contain thresholds beyond which responses change abruptly. This study investigates to what extent cambium phenology is associated with xylem growth and differentiation across conifer species of the northern hemisphere. • Methods Xylem cell production is compared with the periods of cambial activity and cell differentiation assessed on a weekly time scale on histological sections of cambium and wood tissue collected from the stems of nine species in Canada and Europe over 1-9 years per site from 1998 to 2011. • Key Results The dynamics of xylogenesis were surprisingly homogeneous among conifer species, although dispersions from the average were obviously observed. Within the range analysed, the relationships between the phenological timings were linear, with several slopes showing values close to or not statistically different from 1. The relationships between the phenological timings and cell production were distinctly non-linear, and involved an exponential pattern • Conclusions The trees adjust their phenological timings according to linear patterns. Thus, shifts of one phenological phase are associated with synchronous and comparable shifts of the successive phases. However, small increases in the duration of xylogenesis could correspond to a substantial increase in cell production. The findings suggest that the length of the growing season and the resulting amount of growth could respond differently to changes in environmental conditions.
    Subject(s): Climate change ; Cell growth ; Xylem ; Tracheids ; Phenology ; Cell walls ; Conifers ; Cambium ; Cellular differentiation ; Species ; Cambium - growth & development ; Canada ; Xylem - cytology ; Climate Change ; Coniferophyta - growth & development ; Europe ; Xylem - growth & development ; Cell Differentiation ; Index Medicus ; Life Sciences ; xylogenesis ; cell production ; cell differentiation ; secondary wall formation ; conifers ; meristem ; productivity ; phenology ; growth ; Original ; climate change
    ISSN: 0305-7364
    E-ISSN: 1095-8290
    Source: Academic Search Ultimate
    Source: PubMed Central
    Source: Alma/SFX Local Collection
    Source: Oxford Journals 2016 Current and Archive A-Z Collection
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 5
    Language: English
    In: The New phytologist, 2014-09-01, Vol.203 (4), p.1231-1241
    Description: Conifer tree rings are generally composed of large, thin-walled cells of light earlywood followed by narrow, thick-walled cells of dense latewood. Yet, how wood formation processes and the associated kinetics create this typical pattern remains poorly understood. We monitored tree-ring formation weekly over 3 yr in 45 trees of three conifer species in France. Data were used to model cell development kinetics, and to attribute the relative importance of the duration and rate of cell enlargement and cell wall deposition on tree-ring structure. Cell enlargement duration contributed to 75% of changes in cell diameter along the tree rings. Remarkably, the amount of wall material per cell was quite constant along the rings. Consequently, and in contrast with widespread belief, changes in cell wall thickness were not principally attributed to the duration and rate of wall deposition (33%), but rather to the changes in cell size (67%). Cell enlargement duration, as the main driver of cell size and wall thickness, contributed to 56% of wood density variation along the rings. This mechanistic framework now forms the basis for unraveling how environmental stresses trigger deviations (e.g. false rings) from the normal tree-ring structure.
    Subject(s): Full papers ; Cell growth ; Tracheids ; Cell walls ; Conifers ; Pine trees ; Kinetics ; Wood density ; Growth rings ; Modeling ; Latewood ; xylogenesis ; cambial activity ; conifers ; generalized additive models (GAMs) ; tree‐ring structure ; wood density ; kinetics of tracheid development ; quantitative wood anatomy ; Wood - anatomy & histology ; Coniferophyta - growth & development ; Models, Biological ; Coniferophyta - anatomy & histology ; Xylem - growth & development ; Trees - growth & development ; France ; Wood - growth & development ; Trees - anatomy & histology ; Index Medicus ; Life Sciences ; Agricultural sciences ; Vegetal Biology
    ISSN: 0028-646X
    E-ISSN: 1469-8137
    Source: Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 6
    Language: English
    In: Frontiers in plant science, 2016, Vol.7, p.734-734
    Description: Wood is of crucial importance for man and biosphere. In this mini review, we present the fundamental processes involved in tree-ring formation and intra-annual dynamics of cambial activity, along with the influences of the environmental factors. During wood formation, new xylem cells produced by the cambium are undergoing profound transformations, passing through successive differentiation stages, which enable them to perform their functions in trees. Xylem cell formation can be divided in five major phases: (1) the division of a cambial mother cell that creates a new cell; (2) the enlargement of this newly formed cell; (3) the deposition of its secondary wall; (4) the lignification of its cell wall; and finally, (5) its programmed cell death. In most regions of the world cambial activity follows a seasonal cycle. At the beginning of the growing season, when temperature increases, the cambium resumes activity, producing new xylem cells. These cells are disposed along radial files, and start their differentiation program according to their birth date, creating typical developmental strips in the forming xylem. The width of these strips smoothly changes along the growing season. Finally, when climatic conditions deteriorate (temperature or water availability in particular), cambial activity stops, soon followed by cell enlargement, and later on by secondary wall deposition. Without a clear understanding of the xylem formation process, it is not possible to comprehend how annual growth rings and typical wood structures are formed, recording normal seasonal variations of the environment as well as extreme climatic events.
    Subject(s): Life Sciences ; Vegetal Biology ; xylem ; Plant Science ; tree-ring structure ; cambial activity ; cellulose ; tree growth ; lignin ; quantitative wood anatomy ; climatic factors ; Quantitative wood anatomy ; Lignin ; Xylem ; Cellulose
    ISSN: 1664-462X
    E-ISSN: 1664-462X
    Source: PubMed Central
    Source: Directory of Open Access Journals
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 7
    Language: English
    In: Annals of forest science., 2019-09, Vol.76 (3), p.1-12
    Description: This study presents a novel histologic approach to quantify the intra-annual dynamics of carbon sequestration in forming wood. This innovative approach, based on repeated measurements of xylem apparent density, is more direct, and more accurate than the previously published cellular-based approach. Moreover, this new approach, which was tested here on softwoods, is also applicable to hardwoods without any modification. Forest ecosystems are key players of the terrestrial carbon cycle. Indeed, wood represents the principal carbon pool of terrestrial biomass, accumulated in trees through cambial activity.Here, we present a novel, simple, and fast approach to accurately estimate the intra-annual dynamics of aboveground woody biomass production based on image analysis of forming xylem sections.During the 2015 growing season, we weekly collected wood samples (microcores) containing the forming xylem on seven Norway spruces (Picea abies (L.) Karst), grown in Hesse forest (North-East France). The microcores were prepared to allow the observation of the forming tissues with an optical microscope. Xylem apparent density and radial increment were then measured directly on images of the histological sections. In order to compare our “histologic approach” with the previously published “cellular approach,” we also counted the number of tracheids in each differentiation zones, and measured the tracheid dimensions all along the last-formed tree ring.The two approaches yielded comparable meaningful results, describing xylem size increase and aboveground woody biomass production as bell-shaped curves culminating in May and June respectively. However, the histologic approach provided a shorter time lag between xylem size increase and biomass production than the cellular one.Better quantification of the shift between stem growth in size and in biomass will require addressing the knowledge gap regarding lignin deposition kinetics. Nevertheless, our novel histologic approach is simpler and more direct than the cellular one, and may open the way to a first quantification of intra-annual dynamics of woody biomass production in angiosperms, where the cellular approach is hardly applicable.
    Subject(s): Life Sciences ; Environment, general ; Image analysis ; Wood Science & Technology ; Forestry ; Forestry Management ; Xylogenesis ; Norway spruce ; Wood density ; Tree Biology ; Carbon sequestration ; Cambial activity ; Cellular manufacture ; Bulk density ; Trees ; Lignin ; Forests ; Xylem ; Image processing ; Wood ; Hardwoods ; Terrestrial environments ; Biomass ; Forest ecosystems ; Time lag ; Carbon cycle ; Tree rings ; Dynamics ; Kinetics ; Optical microscopes ; Carbon capture and storage ; Softwoods ; Angiosperms
    ISSN: 1286-4560
    E-ISSN: 1297-966X
    Source: Alma/SFX Local Collection
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 8
    Language: English
    In: Plant physiology (Bethesda), 2016-05-01, Vol.171 (1), p.306-317
    Description: The complex inner mechanisms that create typical conifer tree-ring structure (i.e. the transition from large, thin-walled earlywood cells to narrow, thick-walled latewood cells) were recently unraveled. However, what physiological or environmental factors drive xylogenesis key processes remain unclear. Here, we aim to quantify the influence of seasonal variations in climatic factors on the spectacular changes in the kinetics of wood cell differentiation and in the resulting tree-ring structure. Wood formation was monitored in three sites over 3 years for three coniferous species (Norway spruce [ ], Scots pine [ ], and silver fir [ ]). Cell differentiation rates and durations were calculated and related to tracheid final dimensions and corresponding climatic conditions. On the one hand, we found that the kinetics of cell enlargement and the final size of the tracheids were not explained by the seasonal changes in climatic factors. On the other hand, decreasing temperatures strongly constrained cell wall deposition rates during latewood formation. However, the influence of temperature was permanently written into tree-ring structure only for the very last latewood cells, when the collapse of the rate of wall deposition was no longer counterbalanced by the increase of its duration. Our results show that the formation of the typical conifer tree-ring structure, in normal climatic conditions, is only marginally driven by climate, suggesting strong developmental control of xylogenesis. The late breakage of the compensatory mechanism at work in the wall deposition process appears as a clue to understand the capacity of the maximum latewood density to record past temperature conditions.
    Subject(s): ECOPHYSIOLOGY AND SUSTAINABILITY ; Climate ; Forests ; Trees - cytology ; Abies - physiology ; Signal Transduction ; Picea - physiology ; Plant Cells ; Coniferophyta - physiology ; Pinus sylvestris - physiology ; Abies - cytology ; Xylem - cytology ; Trees - physiology ; Coniferophyta - cytology ; Cell Differentiation ; Pinus sylvestris - cytology ; Seasons ; Picea - cytology ; Botanical research ; Plant physiological ecology ; Tree-rings ; Conifers ; Environmental aspects ; Physiological aspects ; Research ; Index Medicus ; Life Sciences
    ISSN: 0032-0889
    E-ISSN: 1532-2548
    Source: American Society of Plant Biologists
    Source: HighWire Press (Free Journals)
    Source: Hellenic Academic Libraries Link
    Source: PubMed Central
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 9
    Language: English
    In: Plant, cell and environment, 2016-06, Vol.39 (6), p.1338-1352
    Description: Because of global warming, high‐latitude ecosystems are expected to experience increases in temperature and drought events. Wood formation will have to adjust to these new climatic constraints to maintain tree mechanical stability and long‐distance water transport. The aim of this study is to understand the dynamic processes involved in wood formation under warming and drought. Xylogenesis, gas exchange, water relations and wood anatomy of black spruce [Picea mariana (Mill.) B.S.P.] saplings were monitored during a greenhouse experiment where temperature was increased during daytime or night‐time (+6 °C) combined with a drought period. The kinetics of tracheid development expressed as rate and duration of the xylogenesis sub‐processes were quantified using generalized additive models. Drought and warming had a strong influence on cell production, but little effect on wood anatomy. The increase in cell production rate under warmer temperatures, and especially during the night‐time warming at the end of the growing season, resulted in wider tree‐rings. However, the strong compensation between rates and durations of cell differentiation processes mitigates warming and drought effects on tree‐ring structure. Our results allowed quantification of how wood formation kinetics is regulated when water and heat stress increase, allowing trees to adapt to future environmental conditions. Global warming in high‐latitude ecosystems will affect wood formation. This work focuses on the dynamic processes involved in wood formation under experimental drought and warming treatments. Our study demonstrates that drought and warming have a strong impact on cell production, but a weak influence on xylem anatomy. Using innovative analysis of kinetics of tracheid development, we quantified how the compensation mechanisms between rates and durations of the xylogenesis sub‐processes strongly mitigate negative effects of multistress on wood structure.
    Subject(s): xylogenesis ; water deficit ; global warming ; tree‐ring structure ; wood anatomy ; Xylem - physiology ; Picea - physiology ; Wood - physiology ; Adaptation, Physiological - physiology ; Trees - growth & development ; Trees - anatomy & histology ; Global Warming ; Trees - physiology ; Wood - anatomy & histology ; Picea - anatomy & histology ; Picea - growth & development ; Xylem - growth & development ; Dehydration - physiopathology ; Wood - growth & development ; Global warming ; Erythromycin ; Droughts ; Analysis ; Index Medicus ; Life Sciences ; Vegetal Biology ; Environmental Sciences ; Global Changes
    ISSN: 0140-7791
    E-ISSN: 1365-3040
    Source: Alma/SFX Local Collection
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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  • 10
    Language: English
    In: Plant, cell and environment, 2019-04, Vol.42 (4), p.1222-1232
    Description: Conifer trees possess a typical anatomical tree‐ring structure characterized by a transition from large and thin‐walled earlywood tracheids to narrow and thick‐walled latewood tracheids. However, little is known on how this characteristic structure is maintained across contrasting environmental conditions, due to its crucial role to ensure sap ascent and mechanical support. In this study, we monitored weekly wood cell formation for up to 7 years in two temperate conifer species (i.e., Picea abies (L.) Karst and Larix decidua Mill.) across an 8°C thermal gradient from 800 to 2,200 m a.s.l. in central Europe to investigate the impact of air temperature on rate and duration of wood cell formation. Results indicated that towards colder sites, forming tracheids compensate a decreased rate of differentiation (cell enlarging and wall thickening) by an extended duration, except for the last cells of the latewood in the wall‐thickening phase. This compensation allows conifer trees to mitigate the influence of air temperature on the final tree‐ring structure, with important implications for the functioning and resilience of the xylem to varying environmental conditions. The disappearing compensation in the thickening latewood cells might also explain the higher climatic sensitivity usually found in maximum latewood density. The structure of conifer wood cells depends on the speed and duration of processes shaping their formation. In this study, we show for the first time that cells growing at colder sites increase their duration of their processes to compensate for a speed reduction. This compensation allows conifers to mitigate the effect of air temperature to maintain a more similar tree‐ring structure despite contrasting conditions.
    Subject(s): temperature response ; xylogenesis ; quantitative wood anatomy ; wood formation dynamics ; tree ring ; conifer ; Temperature ; Picea - physiology ; Wood - cytology ; Wood - anatomy & histology ; Picea - anatomy & histology ; Picea - growth & development ; Larix - physiology ; Xylem - growth & development ; Kinetics ; Larix - growth & development ; Wood - growth & development ; Cell Differentiation - physiology ; Larix - anatomy & histology ; Cell differentiation ; Analysis ; Index Medicus ; Life Sciences
    ISSN: 0140-7791
    E-ISSN: 1365-3040
    Source: Alma/SFX Local Collection
    Source: © ProQuest LLC All rights reserved〈img src="https://exlibris-pub.s3.amazonaws.com/PQ_Logo.jpg" style="vertical-align:middle;margin-left:7px"〉
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