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Monitoring cambial phenology and intra-annual growth dynamics is a useful approach for characterizing the tree growth response to climate change. However, there have been few reports concerning intra-annual wood formation in lowland temperate forests with high time resolution, especially for the comparison between deciduous and coniferous species. The main objective of this study was to determine how the timing, duration and rate of radial growth change between species as related to leaf phenology and the dynamics of non-structural carbohydrates (NSC) under the same climatic conditions. We studied two deciduous species, Fagus sylvatica L. and Quercus petraea (Matt.) Liebl., and an evergreen conifer, Pinus sylvestris L. During the 2009 growing season, we weekly monitored (i) the stem radial increment using dendrometers, (ii) the xylem growth using microcoring and (iii) the leaf phenology from direct observations of the tree crowns. The NSC content was also measured in the eight last rings of the stem cores in April, June and August 2009. The leaf phenology, NSC storage and intraannual growth were clearly different between species, highlighting their contrasting carbon allocation. Beech growth began just after budburst, with a maximal growth rate when the leaves were mature and variations in the NSC content were low. Thus, beech radial growth seemed highly dependent on leaf photosynthesis. For oak, earlywood quickly developed before budburst, which probably led to the starch decrease quantified in the stem from April to June. For pine, growth began before the needles unfolding and the lack of NSC decrease during the growing season suggested that the substrates for radial growth were new assimilates of the needles from the previous year. Only for oak, the pattern determined from the intraannual growth measured using microcoring differed from the pattern determined from dendrometer data. For all species, the ring width was significantly influenced by growth duration and not by growth rate, which differs from previous studies. The observed between-species difference at the intra-annual scale is key information for anticipating suitability of future species in temperate forests. [ABSTRACT FROM AUTHOR]

Ecology Letters (2012) Abstract Model-based projections of shifts in tree species range due to climate change are becoming an important decision support tool for forest management. However, poorly evaluated sources of uncertainty require more scrutiny before relying heavily on models for decision-making. We evaluated uncertainty arising from differences in model formulations of tree response to climate change based on a rigorous intercomparison of projections of tree distributions in France. We compared eight models ranging from niche-based to process-based models. On average, models project large range contractions of temperate tree species in lowlands due to climate change. There was substantial disagreement between models for temperate broadleaf deciduous tree species, but differences in the capacity of models to account for rising CO2 impacts explained much of the disagreement. There was good quantitative agreement among models concerning the range contractions for Scots pine. For the dominant Mediterranean tree species, Holm oak, all models foresee substantial range expansion. [ABSTRACT FROM AUTHOR]

Abstract: In addition to global warming, the frequency and the intensity of droughts will probably increase in central and southern Europe. Resulting climate changes and soil water deficits could alter tree growth, according to sensitivity of each species. The aim of this study was to compare the growth response of three European species (Fagus sylvatica, Quercus petraea and Pinus sylvestris) to climatic variations and soil water deficits in the same temperate forest. Three mature stands per species were sampled to obtain earlywood, latewood and total ring chronologies from 1960 to 2007. Climate–growth relationships were established by bootstrapped correlations and response function analysis. Monthly bioclimatic regressors were simulated by a physiological water balance model that used daily climatic data and stand parameters to estimate soil water deficits. Our results highlighted a common sensitivity to precipitation from May to July for the dominant tree growth of the three species but also differences in the species vulnerability to climate and soil water deficits. Beech was the most sensitive species to the climatic conditions of the current growing season. Beech growth was positively correlated with precipitation from May to July and negatively with maximal temperatures in June and July. Oak growth was negatively correlated with minimal temperatures in the previous August and September and positively with precipitation in the previous October and December during pointer years. This led to long-term consequences for growth, probably due to carbon reserve depletion. Pine growth was positively influenced by warm December but was also vulnerable to maximal temperatures and soil water deficits from June to August. The climate in August only influenced the pine growth probably because the growing season of pine was longer than that of the deciduous species. For both oak and pine, latewood was the component that was most sensitive to climatic variations and soil water deficits. According to the study findings, an increase in the frequency and the intensity of droughts could affect the three species. Maximum summer temperatures could have negative impacts for beech and pine growth. Dry and warm autumns could lead to long-term consequences and decrease the oak growth. [Copyright &y& Elsevier]

Abstract: Modelling phenology is crucial to assess the impact of climate change on the length of the canopy duration and the productivity of terrestrial ecosystems. Focusing on six dominant European tree species, the aims of this study were (i) to examine the accuracy of different leaf phenology models to simulate the onset and ending of the leafy season, with particular emphasis on the putative role of chilling to release winter bud dormancy and (ii) to predict seasonal shifts for the 21st century in response to climate warming. Models testing and validation were done for each species considering 2 or 3 years of phenological observations acquired over a large elevational gradient (1500m range, 57 populations). Flushing models were either based solely on forcing temperatures (1-phase models) or both on chilling and forcing temperatures (2-phases models). Leaf senescence models were based on both temperature and photoperiod. We show that most flushing models are able to predict accurately the observed flushing dates. The 1-phase models are as efficient as 2-phases models for most species suggesting that chilling temperatures are currently sufficient to fully release bud dormancy. However, our predictions for the 21st century highlight that chilling temperature could be insufficient for some species at low elevation. Overall, flushing is expected to advance in the next decades but this trend substantially differed between species (from 0 to 2.4 days per decade). The prediction of leaf senescence appears more challenging, as the proposed models work properly for only two out of four deciduous species, for which senescence is expected to be delayed in the future (from 1.4 to 2.3 days per decade). These trends to earlier spring leafing and later autumn senescence are likely to affect the competitive balance between species. For instance, simulations over the 21st century predict a stronger lengthening of the canopy duration for Quercus petraea than for Fagus sylvatica, suggesting that shifts in the elevational distributions of these species might occur. [Copyright &y& Elsevier]