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Symposium 3. Ecophysiological interpretations of stable isotopes in dendroecology

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14:05, Thursday 30 Jun 2022 (1 hour 45 minutes)
Coeur des Sciences, Sherbrooke Building, UQAM - Amphitheatre (SH-2800)   Virtual session
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The interpretation of stable isotopes in a dendroecological framework can provide powerful insights into how trees adjust physiologically in response to the environment. This symposium aims to bring together researchers who use stable isotopes in tree rings to address ecophysiological responses to environmental changes from intra-annual to multi-decadal resolution. We hope this symposium will enable fruitful discussions and new ideas and help identify new research directions aiming to foster new collaborations between researchers within the scientific community. Therefore, we welcome submissions presenting new scientific approaches on tree-ring isotopic observations and comparisons to data and models based on forest dynamics, ecophysiology, hydrology, biogeochemistry and, remote sensing. Specific topics this session is anticipated to include:

1.         Changes in carbon isotope discrimination and water-use efficiency in response to environmental changes (climate, atmospheric CO2, atmospheric deposition).

2.         Seasonal and environmental changes recorded in intra-annual isotopic variations (Studies using xylogenesis, Quantitative wood anatomy, and isotopes).

3.         Changes in water source and source versus relative humidity interactions. (Oxygen isotopes)

4.         Using d15N in tree rings to assess changes in environmental conditions (Nitrogen availability, atmospheric deposition).

5.         Impacts of climate change on plant functioning under different environmental conditions (dry versus humid) (multi-species interactions).

6.         Forest responses to disturbances (e.g., fires, outbreaks, etc.).

7.         Improvements of vegetation models using multiple tree ring parameters.

8.         Projections of forest responses to future climate change informed by stable isotopes.

Sub Sessions

14:05 - 14:20 | 15 minutes
Symposium 3

Climate change across the western US has increased air temperature, resulting in decreased snow and lengthening of the summer drought. Recent studies have also highlighted the positive feedback loops between soil moisture and vapor pressure deficit (VPD), which can exacerbates aridity in water limited ecosystems. These interactions can make it difficult to untangle the influences of soil moisture and VPD on tree growth, and yet our ability to untangle these parameters is important for buil...

Jia Hu

14:20 - 14:35 | 15 minutes
Symposium 3

In the southwestern U.S. the North American Monsoon (NAM) delivers summer precipitation from July – September and the rest is provided as snowmelt in early spring. Both periods serve as an important water source for plants, but due to the heterogeneous nature of the NAM, not all locations within the region receive precipitation, leading to differences in soil moisture. Understanding how spatially heterogeneous soil water storage controls plant water use is needed, especially with projected...

14:35 - 14:50 | 15 minutes
Symposium 3

Hydrogen isotope ratios in tree ring cellulose (δ2HC) have been recognized as a potential proxy for plant-climate interactions, plant physiology, and carbon metabolism. This goes along with recent studies showing species-specific δ2HC differences that cannot be explained by climatic conditions. However, systematic investigations on the phylogenetic impact on 2H-fractionations in carbohydrates of woody plant species are missing.Here, we sampled leaves and twigs of 152 trees and ...

14:50 - 15:05 | 15 minutes
Symposium 3

The ability of forests to continue absorbing atmospheric CO2, and hence mitigating climate change, depends on the extent to which their productivity is limited by nutrients, with nitrogen (N) being particularly important in temperate and boreal regions. Fertilisation experiments offer an opportunity to directly determine whether atmospheric N input can contribute to alleviating N limitation. However, the majority of the experiments have normally considered soil N applications, which do not...

15:05 - 15:20 | 15 minutes
Symposium 3

Under elevated CO2, photosynthetic carbon isotope discrimination is expected to increase in response to photosynthesis stimulation. While this response is widely documented in laboratory and field experiments, long-term proxies indicate that such response is not universally observed in response to the growth of atmospheric CO2. We investigated historical trends of  photosynthetic carbon isotope discrimination derived from carbon isotope measurements of tree rings (Δ13C) from 147 chron...

15:20 - 15:35 | 15 minutes
Symposium 3

Drought conditions have been projected to increase globally as atmospheric CO2 (ca) and vapor pressure deficit (VPD) increase. Experimental and modelling studies have suggested that forest responses to drought may be bolstered by increased ca, but it remains unclear how prevalent this response is in natural forest ecosystems. We developed a framework using intrinsic water use efficiency (WUEi = assimilation (A)/ stomatal conductance (gs)) and evaporative water use efficiency (WUEE = A/tran...

15:35 - 15:50 | 15 minutes
Symposium 3

The boreal forest located in high northern latitudes stores about a third of the world’s carbon and covers almost a quarter of the Earth’s land surface. This region is experiencing one of the fastest temperatures increases on the planet. Yet it is unclear how global warming affects carbon sequestration and storage in this biome. Here, we explore how white spruce (Picea glauca [Moench] Voss) growing in North America responded to climate change during the 20th century using tree-ring width a...

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