Evaluating climate signal recorded in tree-ring δ¹³C and δ¹⁸O values from bulk wood and α-cellulose for six species across four sites in the northeastern US

Ajuts: National Aeronautics and Space Administration (NASA), Grant/Award Number:NNX12AK56GRationale : we evaluated the applicability of tree-ring δ¹³C and δ¹⁸O values in bulk wood - instead of the more time and lab-consuming α-cellulose δ¹³C and δ¹⁸O values, to assess climate and physiological signals across multiple sites and for six tree species along a latitudinal gradient (35°97'N to 45°20'N) of the northeastern United States. -Methods: wood cores (n = 4 per tree) were sampled from ten trees per species. Cores were cross-dated within and across trees at each site, and for the last 30 years. Seven years, including the driest on record, were selected for this study. The δ¹³C and δ¹⁸O values were measured on two of the ten trees from the bulk wood and the α-cellulose. The offsets between materials in δ¹³C and δ¹⁸O values were assessed. Correlation and multiple regression analyses were used to evaluate the strength of the climate signal across sites. Finally the relationship between δ¹³C and δ¹⁸O values in bulk wood vs α-cellulose was analyzed to assess the consistency of the interpretation, in terms of CO2 assimilation and stomatal conductance, from both materials. - Results: we found offsets of 1.1‰ and 5.6‰ between bulk and α-cellulose for δ¹³C and δ¹⁸O values, respectively, consistent with offset values reported in the literature. Bulk wood showed similar or stronger correlations to climate parameters than α-cellulose for the investigated sites. In particular, temperature and vapor pressure deficit and standard precipitation-evaporation index (SPEI) were the most visible climate signals recorded in δ¹³C and δ¹⁸O values, respectively. For most of the species, there was no relationship between δ13C and δ18O values, regardless of the wood material considered. - conclusions: extraction of α-cellulose was not necessary to detect climate signals in tree rings across the four investigated sites. Furthermore, the physiological information inferred from the dual isotope approach was similar for most of the species regardless of the material considered

Detecting long-term changes in stomatal conductance: challenges and opportunities of tree-ring δ18 O proxy

N/An/

Disentangling the role of photosynthesis and stomatal conductance on rising forest water-use efficiency

Multiple lines of evidence suggest that plant water-use efficiency (WUE) -the ratio of carbon assimilation to water loss- has increased in recent decades. Although rising atmospheric CO2 has been proposed as the principal cause, the underlying physiological mechanisms are still being debated, and implications for the global water cycle remain uncertain. Here, we addressed this gap using 30-y tree ring records of carbon and oxygen isotope measurements and basal area increment from 12 species in 8 North American mature temperate forests. Our goal was to separate the contributions of enhanced photosynthesis and reduced stomatal conductance to WUE trends and to assess consistency between multiple commonly used methods for estimating WUE. Our results show that tree ring-derived estimates of increases in WUE are consistent with estimates from atmospheric measurements and predictions based on an optimal balancing of carbon gains and water costs, but are lower than those based on ecosystemscale flux observations. Although both physiological mechanisms contributed to rising WUE, enhanced photosynthesis was widespread, while reductions in stomatal conductance were modest and restricted to species that experienced moisture limitations. This finding challenges the hypothesis that rising WUE in forests is primarily the result of widespread, CO2-induced reductions in stomatal conductance

Interface air-lac: les ostracodes des lacs tempérés

International audienc

Reconstitution du dernier cycle climatique dans le sud des Balkans (géochimie des ostracodes lacustres (Ohrid))

ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Climate controlled ostracod preservation in Lake Ohrid (Albania, Macedonia)

International audienc

Evaluating climate signal recorded in tree‐ring δ13C and δ18O values from bulk wood and α‐cellulose for six species across four sites in the northeastern US

Rationale: We evaluated the applicability of tree‐ring δ13C and δ18O values in bulk wood – instead of the more time and lab‐consuming α‐cellulose δ13C and δ18O values, to assess climate and physiological signals across multiple sites and for six tree species along a latitudinal gradient (35°97\u27N to 45°20\u27N) of the northeastern United States. Methods: Wood cores (n = 4 per tree) were sampled from ten trees per species. Cores were cross‐dated within and across trees at each site, and for the last 30 years. Seven years, including the driest on record, were selected for this study. The δ13C and δ18O values were measured on two of the ten trees from the bulk wood and the α‐cellulose. The offsets between materials in δ13C and δ18O values were assessed. Correlation and multiple regression analyses were used to evaluate the strength of the climate signal across sites. Finally the relationship between δ13C and δ18O values in bulk wood vs α‐cellulose was analyzed to assess the consistency of the interpretation, in terms of CO2 assimilation and stomatal conductance, from both materials. Results: We found offsets of 1.1‰ and 5.6‰ between bulk and α‐cellulose for δ13C and δ18O values, respectively, consistent with offset values reported in the literature. Bulk wood showed similar or stronger correlations to climate parameters than α‐cellulose for the investigated sites. In particular, temperature and vapor pressure deficit and standard precipitation‐evaporation index (SPEI) were the most visible climate signals recorded in δ13C and δ18O values, respectively. For most of the species, there was no relationship between δ13C and δ18O values, regardless of the wood material considered. Conclusions: Extraction of α‐cellulose was not necessary to detect climate signals in tree rings across the four investigated sites. Furthermore, the physiological information inferred from the dual isotope approach was similar for most of the species regardless of the material considered

Seasonal and synoptic climatic drivers of tree growth in the Bighorn Mountains, WY, USA (1654–1983 CE)

In the United States' (US) Northern Rockies, synoptic pressure systems and atmospheric circulation drive interannual variation in seasonal temperature and precipitation. The radial growth of high-elevation trees in this semi-arid region captures this temperature and precipitation variability and provides long time series to contextualize instrumental-era variability in synoptic-scale climate patterns. Such variability in climate patterns can trigger extreme climate events, such as droughts, floods, and forest fires, which have a damaging impact on human and natural systems. We developed 11 tree-ring width (TRW) chronologies from multiple species and sites to investigate the seasonal climatic drivers of tree growth in the Bighorn Mountains, WY. A principal component analysis of the chronologies identified 54% of shared common variance (1894-2014). Tree growth (expressed by PC1) was driven by multiple seasonal climate variables: previous October and current July temperatures, as well as previous December and current April precipitation, had a positive influence on growth, whereas growth was limited by July precipitation. These seasonal growth-climate relationships corresponded to circulation patterns at higher atmospheric levels over the Bighorn Mountains. Tree growth was enhanced when the winter jet stream was in a northward position, which led to warmer winters, and when the spring jet stream was further south, which led to wetter springs. The second principal component, explaining 19% of the variance, clustered sites by elevation and was strongly related to summer temperature. We leverage this summer temperature signal in our TRW chronologies by combining it with an existing maximum latewood density (MXD) chronology in a nested approach. This allowed us to reconstruct Bighorn Mountains summer (June, July, and August) temperature (BMST) back to 1654, thus extending the instrumental temperature record by 250 years. Our BMST reconstruction explains 39-53% of the variance in regional summer temperature variability. The 1830s were the relatively coolest decade and the 1930s were the warmest decade over the reconstructed period (1654-1983 CE) - which excludes the most recent 3 decades. Our results contextualize recent drivers and trends of climate variability in the US Northern Rockies, which contributes to the information that managers of human and natural systems need in order to prepare for potential future variability.24 month embargo; published online: 1 December 2019This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

The oxygen and carbon isotopic signatures of biogenic carbonates in Gerzensee, Switzerland, during the rapid warming around 14,685years BP and the following interstadial

International audienc

Tree-ring δ 13C tracks flux tower ecosystem productivity estimates in a NE temperate forest

We investigated relationships between tree-ring δ ^13 C and growth, and flux tower estimates of gross primary productivity (GPP) at Harvard Forest from 1992 to 2010. Seasonal variations of derived photosynthetic isotope discrimination ( Δ ^13 C) and leaf intercellular CO _2 concentration ( c _i ) showed significant increasing trends for the dominant deciduous and coniferous species. Δ ^13 C was positively correlated to growing-season GPP and is primarily controlled by precipitation and soil moisture indicating that site conditions maintained high stomatal conductance under increasing atmospheric CO _2 levels. Increasing Δ ^13 C over the 1992–2010 period is attributed to increasing annual and summer water availability identified at Harvard Forest and across the region. Higher Δ ^13 C is coincident with an enhancement in growth and ecosystem-level net carbon uptake. This work suggests that tree-ring δ ^13 C could serve as a measure of forest GPP and be used to improve the calibration and predictive skill of ecosystem and carbon cycle models