Tree-Ring Stable Isotopes Reveal Twentieth-Century Increases in Water-Use Efficiency of Fagus sylvatica and Nothofagus spp. in Italian and Chilean Mountains

Given the large contribution of forests to terrestrial carbon storage, there is a need to resolve the environmental and physiological drivers of tree-level response to rising atmospheric CO2. This study examines how site-level soil moisture influences growth and intrinsic water-use efficiency in sugar maple (Acer saccharum Marsh.). We construct tree-ring, δ18O, and Δ13C chronologies for trees across a soil moisture gradient in Ontario, Canada, and employ a structural equation modelling approach to ascertain their climatic, ontogenetic, and environmental drivers. Our results support previous evidence for the presence of strong developmental effects in tree-ring isotopic chronologies — in the range of −4.7‰ for Δ13C and +0.8‰ for δ18O — across the tree life span. Additionally, we show that the physiological response of sugar maple to increasing atmospheric CO2 depends on site-level soil moisture variability, with trees only in relatively wet plots exhibiting temporal increases in intrinsic water-use efficiency. These results suggest that trees in wet and mesic plots have experienced temporal increases in stomatal conductance and photosynthetic capacity, whereas trees in dry plots have experienced decreases in photosynthetic capacity. This study is the first to examine sugar maple physiology using a dendroisotopic approach and broadens our understanding of carbon–water interactions in temperate forests.

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Temporal variability in carbon and nitrogen stable isotopes of Strobilanthes kunthianus leaf: Its photosynthetic efficacy and water-use efficiency in a warming climate

Journal of Earth System Science ◽

10.1007/s12040-021-01737-5 ◽

2021 ◽

Vol 130 (4) ◽

Author(s):

Anjum Farooqui ◽

Rajesh Agnihotri ◽

Salman Khan ◽

S K S Gahlaud ◽

M U Sharief

Keyword(s):

Stable Isotopes ◽

Water Use Efficiency ◽

Water Use ◽

Temporal Variability ◽

Nitrogen Stable Isotopes ◽

Carbon And Nitrogen ◽

Warming Climate ◽

Use Efficiency

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Estimating the Root Water Uptake of Surface-Irrigated Apples Using Water Stable Isotopes and the Hydrus-1D Model

Water ◽

10.3390/w10111624 ◽

2018 ◽

Vol 10 (11) ◽

pp. 1624 ◽

Cited By ~ 5

Author(s):

Lijian Zheng ◽

Juanjuan Ma ◽

Xihuan Sun ◽

Xianghong Guo ◽

Qiyun Cheng ◽

...

Keyword(s):

Stable Isotopes ◽

Water Use Efficiency ◽

Water Use ◽

Water Uptake ◽

Root Water Uptake ◽

Surface Irrigation ◽

Apple Trees ◽

1D Model ◽

Use Efficiency ◽

Hydrus 1D

The future production of irrigated fruit orchards in the Loess Plateau of China is threatened by a shortage of freshwater. To improve water use efficiency under conditions where irrigation is limited, it is necessary to quantify the root water uptake (RWU) of apple trees. The RWU of apple trees was estimated under surface irrigation using water stable isotope technology and the Hydrus-1D model. Using the Romero-Saltos and IsoSource models, the stable isotopes of water in stems, different soil depths, and different precipitation were analyzed in a 5-year-old dwarfing apple orchard during two seasons 2016 and 2017. Hydrus-1D model was able to simulate the RWU of apple using the maximum coefficient of determination (0.9), providing a root mean square error of 0.019 cm3 cm−3 and a relative error of 2.25%. The results showed that the main depth of RWU ranged from 0–60 cm during the growth season, with the main contribution occurring in the 0–40 cm depth. These findings indicated that reducing the traditional surface irrigation depth will be important for improving the irrigation water use efficiency.

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Evidence of changing intrinsic water-use efficiency under rising atmospheric CO2 concentrations in Boreal Fennoscandia from subfossil leaves and tree ring δ13C ratios

Global Change Biology ◽

10.1111/j.1365-2486.2010.02273.x ◽

2011 ◽

Vol 17 (2) ◽

pp. 1064-1072 ◽

Cited By ~ 63

Author(s):

MARY GAGEN ◽

WALTER FINSINGER ◽

FRIEDERIKE WAGNER-CREMER ◽

DANNY MCCARROLL ◽

NEIL J. LOADER ◽

...

Keyword(s):

Water Use Efficiency ◽

Water Use ◽

Tree Ring ◽

Atmospheric Co2 ◽

Co2 Concentrations ◽

Intrinsic Water Use Efficiency ◽

Use Efficiency ◽

Atmospheric Co2 Concentrations

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20th-century changes in carbon isotopes and water-use efficiency: Tree-ring based evaluation of the CLM4.5 and LPX-Bern models

10.5194/bg-2016-515 ◽

2016 ◽

Author(s):

Kathrin M. Keller ◽

Sebastian Lienert ◽

Anil Bozbiyik ◽

Thomas F. Stocker ◽

Olga V. Churakova ◽

...

Keyword(s):

Stomatal Conductance ◽

Water Use Efficiency ◽

20Th Century ◽

Water Use ◽

Tree Ring ◽

Dynamic Global Vegetation Model ◽

Isotopic Discrimination ◽

Tree Ring Data ◽

Intrinsic Water Use Efficiency ◽

Use Efficiency

Abstract. Measurements of the stable carbon isotope ratio (δ13C) on annual tree rings offer new opportunities to evaluate mechanisms of variations in photosynthesis and stomatal conductance under changing CO2 and climate, especially in conjunction with process-based biogeochemical model simulations. The isotopic discrimination is indicative of the ratio between the CO2 partial pressure in the intercellular cavities and the atmosphere (ci / ca) and of the ratio of assimilation to stomatal conductance, termed intrinsic water-use efficiency (iWUE). We performed isotope-enabled simulations over the industrial period with the land biosphere module (CLM4.5) of the Community Earth System Model and the LPX-Bern dynamic global vegetation model. Results for C3 tree species show good agreement with a global compilation of δ13C measurements on leaves, though modeled 13C discrimination by C3 trees is smaller in arid regions than measured. A compilation of seventy-six tree-ring records, mainly from Europe, boreal Asia, and western North America, suggest on average small 20th-century changes in isotopic discrimination and an increase in iWUE of about 27 % since 1900. LPX-Bern results match these century-scale reconstructions, supporting the idea that the physiology of stomata has evolved to optimize trade-offs between carbon gain by assimilation and water loss. In contrast, CLM4.5 simulates an increase in discrimination and in turn a change in iWUE that is almost twice as large as revealed by the tree-ring data. Factorial simulations show that these changes are mainly in response to rising atmospheric CO2. The results suggest that the down-regulation of ci / ca and of photosynthesis by nitrogen limitation is possibly too strong in the standard setup of CLM4.5 or there may be more fundamental problems associated with the prescribed relationship between conductance and assimilation.

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