What drives interannual variation in tree ring oxygen isotopes in the Amazon?

Baker, Jessica C. A.; Gloor, Manuel; Spracklen, D. V.; Arnold, S. R.; Tindall, Julia; Clerici, Santiago; Leng, Melanie J.; Brienen, Roel J. W.

doi:10.1002/2016gl071507

Cited by 31 publications

(52 citation statements)

References 74 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These indices represent the state of the forest cover and the atmospheric processes along the air mass pathways to our monitoring site. A similar approach has been used in other studies (Baker et al, 2016;Fiorella et al, 2015). Daily indices were averaged across the four vertical levels mentioned above.…”

Section: Methodsmentioning

confidence: 99%

The Forest Effects on the Isotopic Composition of Rainfall in the Northwestern Amazon Basin

et al. 2020

View full text Add to dashboard Cite

In the Amazon basin, intense precipitation recycling across the forest significantly modifies the isotopic composition of rainfall (δ18O, δD). In the tropical hydrologic cycle, such an effect can be identified through deuterium excess (dxs), yet it remains unclear what environmental factors control dxs, increasing the uncertainty of dxs‐based paleoclimate reconstructions. Here we present a 4‐year record of the isotopic composition of rainfall, monitored in the northwestern Amazon basin. We analyze the isotopic variations as a function of the air mass history, based on atmospheric back trajectory analyses, satellite observations of precipitation upstream, leaf area index, and simulated moisture recycling along the transport pathway. We show that the precipitation recycling in the forest exerts a significant control on the isotopic composition of precipitation in the northwestern Amazon basin, especially on dxs during the dry season (r = 0.71). Applying these observations to existing speleothem and pollen paleorecords, we conclude that winter precipitation increased after the mid‐Holocene, as the expansion of the forest allowed for more moisture recycling. Therefore, forest effects should be considered when interpreting paleorecords of past precipitation changes.

show abstract

Section: Methodsmentioning

confidence: 99%

The Forest Effects on the Isotopic Composition of Rainfall in the Northwestern Amazon Basin

et al. 2020

View full text Add to dashboard Cite

show abstract

“…18 O relationships (see Baker et al 2016). Trees from the other sites had a high incidence of strongly wedging rings, which weaken interradial ring-width relationships and, thus, between-tree correlations were also expected to be weak.…”

Section: Methodsmentioning

confidence: 99%

“…Tropical tree rings and their associated characteristics can be used to reconstruct climate (e.g. Baker et al 2016;Mendivelso et al 2013;Schöngart et al 2006;Vlam et al 2014;Xu et al 2015), inform sustainable forest management (e.g. Brienen and Zuidema 2006;De Ridder et al 2013;Schöngart 2008), study forest dynamics (e.g.…”

Section: Introductionmentioning

confidence: 99%

Does Cedrela always form annual rings? Testing ring periodicity across South America using radiocarbon dating

Baker

Santos

Gloor

et al. 2017

Trees

View full text Add to dashboard Cite

Key Message Radiocarbon dating shows that Cedrela trees from Bolivia, Ecuador and Venezuela form one ring per year but Cedrela trees from Suriname form two rings per year. Abstract Tropical tree rings have the potential to yield valuable ecological and climate information, on the condition that rings are annual and accurately dated. It is important to understand the factors controlling ring formation, since regional variation in these factors could cause trees in different regions to form tree rings at different times. Here, we use 'bomb-peak' radiocarbon ( 14 C) dating to test the periodicity of ring formation in Cedrela trees from four sites across tropical South America. We show that trees from Bolivia, Ecuador and Venezuela have reliably annual tree rings, while trees from Suriname regularly form two rings per year. This proves that while tree rings of a particular species may be demonstrably annual at one site, this does not imply that rings are formed annually in other locations. We explore possible drivers of variation in ring periodicity and find that Cedrela growth rhythms are most likely caused by precipitation seasonality, with a possible degree of genetic control. Therefore, tree-ring studies undertaken at new locations in the tropics require independent validation of the annual nature of tree rings, irrespective of how the studied species behaves in other locations.

show abstract

“…In the absence of evaporation and transpiration, fractionation during condensation and condensate removal via precipitation will cause a gradual depletion of the heavy water isotope in water vapor of air parcels (so‐called “Rayleigh distillation”) travelling over the land. Put another way, and under the same conditions, spatiotemporal patterns in the precipitation isotope ratio R≡H 2 18 O/H 2 16 O (mol/mol) contain information about the amount of condensation along an air‐parcel's path and thus about the hydrological cycle, both today and in the past (Baker et al, ; Brienen et al, ; Salati et al, ; Thompson et al, ; van Breukelen et al, ; Wang et al, ; Wright et al, ). Air parcels moving into continents from the sea tend indeed to show an increasing heavy‐isotope depletion signal the further into the continent they have travelled.…”

Section: Introductionmentioning

confidence: 99%

Can We Detect Changes in Amazon Forest Structure Using Measurements of the Isotopic Composition of Precipitation?

Pattnayak

Tindall

Brienen

et al. 2019

Geophysical Research Letters

Self Cite

View full text Add to dashboard Cite

Large-scale (>500 km) spatial gradients of precipitation oxygen isotope ratios (δ 18 O p ) hold information about the hydrological cycle. They result from the interplay between rainout and evapotranspiration along air-parcel paths, but these counteracting effects are difficult to disentangle, complicating quantification of the effect of land cover change on δ 18 O p . We show that disentangling can qualitatively be achieved using climate model simulations with a land-derived precipitation tracer for tropical South America. We then either vary land cover as observed since 1870 or replace Amazon forests with bare land to determine the resulting signals. Our results indicate that effects of historically changing land cover on annual mean δ 18 O isotope-ratio gradients are small and unlikely detectable, although there is a noticeable signal during the dry season. Furthermore, the effect of changes in water recycling on Amazon δ 18 O p in paleo-records may have been overestimated and need reinterpretation. Plain Language Summary Deforestation causes reduction in precipitation downwind becausetrees act as pumps of water from soils to the atmosphere. This mechanism is primarily important during the dry season. How strong this effect is currently in the Amazon, given that approximately 20% of the forests have been cut, and how important it may be in the future if more forests are being destroyed is of great interest. One indicator of such changes is the east-west difference in heavy water isotope content of precipitation. While preferential rainout of the heavy isotope along air parcel trajectories enhances this difference, transpiration by forests decreases the difference. This is because forests inject water back into the atmosphere that is more enriched than the overlying water vapor. Records of this difference during the last ice age, in particular, have been interpreted in a previous study as providing information on continental recycling. We apply a land-derived water tagging approach in model simulations to investigate the effect of continental recycling on precipitation isotope content and to estimate this effect for varying land cover. We find that a 20% deforestation has only a small impact on precipitation isotope content. Even for a complete deforestation, in contrast to a previous interpretation, thus, only some of the isotopic signal observed during the ice age can be attributed to changes in continental recycling.

show abstract

What drives interannual variation in tree ring oxygen isotopes in the Amazon?

Cited by 31 publications

References 74 publications

The Forest Effects on the Isotopic Composition of Rainfall in the Northwestern Amazon Basin

The Forest Effects on the Isotopic Composition of Rainfall in the Northwestern Amazon Basin

Does Cedrela always form annual rings? Testing ring periodicity across South America using radiocarbon dating

Can We Detect Changes in Amazon Forest Structure Using Measurements of the Isotopic Composition of Precipitation?

Contact Info

Product

Resources

About