AmazonFACE – Assessing the response of Amazon rainforest functioning to elevated atmospheric carbon dioxide concentrations

2020 ◽  
Author(s):  
Anja Rammig ◽  
Katrin Fleischer ◽  
Sabrina Garcia ◽  
Nathielly Martins ◽  
Juliane Menezes ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Carbon Sink ◽  
Global Climate ◽  
Terrestrial Ecosystems ◽  
Amazon Rainforest ◽  
Past Century ◽  
Sink Strength ◽  
Climate Conditions ◽  
Use Efficiency

<p>The rapid rise in atmospheric CO<sub>2</sub> concentration over the past century is unprecedented. It has unambiguously influenced Earth’s climate system and terrestrial ecosystems. Elevated atmospheric CO<sub>2</sub> concentrations (eCO<sub>2</sub>) have induced an increase in biomass and thus, a carbon sink in forests worldwide. It is assumed that eCO<sub>2</sub> stimulates photosynthesis and plant productivity and enhances water-use efficiency – the so-called CO<sub>2</sub>-fertilization effect, which may provide an important buffering effect for plants during adverse climate conditions. For these reasons, current global climate simulations consistently predict that tropical forests will continue to sequester more carbon in aboveground biomass, partially compensating human emissions and decelerating climate change by acting as a carbon sink. In contrast to model simulations, several lines of evidence point towards a decreasing carbon sink strength of the Amazon rainforest. Reliable predictions of eCO<sub>2</sub> effects in the Amazon rainforest are hindered by a lack of process-based information gained from ecosystem scale eCO<sub>2</sub> experiments. Here we report on baseline measurements from the Amazon Free Air CO<sub>2</sub> Enrichment (AmazonFACE) experiment and preliminary results from open-top chamber (OTC) experiments with eCO<sub>2</sub>. After three months of eCO<sub>2</sub>, we find that understory saplings increased carbon assimilation by 17% (under light saturated conditions) and water use efficiency by 39% in the OTC experiment. We present our main hypotheses for the FACE experiment, and discuss our expectations on the potential driving processes for limiting or stimulating the Amazon rainforest carbon sink under eCO<sub>2</sub>. We focus on possible effects of eCO<sub>2</sub> on carbon uptake and allocation, nutrient cycling, water-use and plant-herbivore interactions, which need to be implemented in dynamic vegetation models to estimate future changes of the Amazon carbon sink.</p>

scholarly journals Interannual and Seasonal Variations in Ecosystem Transpiration and Water Use Efficiency in a Tropical Rainforest

Forests ◽  
2018 ◽  
Vol 10 (1) ◽  
pp. 14 ◽  
Author(s):  
Maricar Aguilos ◽  
Clément Stahl ◽  
Benoit Burban ◽  
Bruno Hérault ◽  
Elodie Courtois ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Soil Water ◽  
Water Use ◽  
Seasonal Variations ◽  
Radiation Effects ◽  
Global Radiation ◽  
Climate Conditions ◽  
Carbon Cycles ◽  
Use Efficiency ◽  
The Impact

Warmer and drier climates over Amazonia have been predicted for the next century with expected changes in regional water and carbon cycles. We examined the impact of interannual and seasonal variations in climate conditions on ecosystem-level evapotranspiration (ET) and water use efficiency (WUE) to determine key climatic drivers and anticipate the response of these ecosystems to climate change. We used daily climate and eddyflux data recorded at the Guyaflux site in French Guiana from 2004 to 2014. ET and WUE exhibited weak interannual variability. The main climatic driver of ET and WUE was global radiation (Rg), but relative extractable water (REW) and soil temperature (Ts) did also contribute. At the seasonal scale, ET and WUE showed a modal pattern driven by Rg, with maximum values for ET in July and August and for WUE at the beginning of the year. By removing radiation effects during water depleted periods, we showed that soil water stress strongly reduced ET. In contrast, drought conditions enhanced radiation-normalized WUE in almost all the years, suggesting that the lack of soil water had a more severe effect on ecosystem evapotranspiration than on photosynthesis. Our results are of major concern for tropical ecosystem modeling because they suggest that under future climate conditions, tropical forest ecosystems will be able to simultaneously adjust CO2 and H2O fluxes. Yet, for tropical forests under future conditions, the direction of change in WUE at the ecosystem scale is hard to predict, since the impact of radiation on WUE is counterbalanced by adjustments to soil water limitations. Developing mechanistic models that fully integrate the processes associated with CO2 and H2O flux control should help researchers understand and simulate future functional adjustments in these ecosystems.

scholarly journals How is water-use efficiency of terrestrial ecosystems distributed and changing on Earth?

2014 ◽  
Vol 4 (1) ◽  
Author(s):  
Xuguang Tang ◽  
Hengpeng Li ◽  
Ankur R. Desai ◽  
Zoltan Nagy ◽  
Juhua Luo ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Terrestrial Ecosystems ◽  
Use Efficiency

Characteristics of water use efficiency in terrestrial ecosystems and its influence factors in Ningxia Province

2019 ◽  
Vol 39 (24) ◽  
Author(s):  
宫菲 GONG Fei ◽  
杜灵通 DU Lingtong ◽  
孟晨 MENG Chen ◽  
丹杨 DAN Yang ◽  
王乐 WANG Le ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Influence Factors ◽  
Terrestrial Ecosystems ◽  
Use Efficiency

Anthropogenic NOx emissions alter the intrinsic water-use efficiency (WUEi) for Quercus cerris stands under Mediterranean climate conditions

2010 ◽  
Vol 158 (9) ◽  
pp. 2841-2847 ◽  
Author(s):  
Rossella Guerrieri ◽  
Rolf Siegwolf ◽  
Matthias Saurer ◽  
Francesco Ripullone ◽  
Maurizio Mencuccini ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Mediterranean Climate ◽  
Nox Emissions ◽  
Climate Conditions ◽  
Intrinsic Water Use Efficiency ◽  
Use Efficiency ◽  
Quercus Cerris

scholarly journals Responses of Water Use Efficiency to Drought in Southwest China

2020 ◽  
Vol 12 (1) ◽  
pp. 199 ◽  
Author(s):  
Jingxue Zhao ◽  
Tongren Xu ◽  
Jingfeng Xiao ◽  
Shaomin Liu ◽  
Kebiao Mao ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Southwest China ◽  
Vegetation Type ◽  
Terrestrial Ecosystems ◽  
Temporal Variations ◽  
Drought Severity ◽  
Enhancement Effect ◽  
Severe Drought ◽  
Use Efficiency

Water use efficiency (WUE) measures the tradeoff between carbon uptake and water consumption in terrestrial ecosystems. It remains unclear how the responses of WUE to drought vary with drought severity. We assessed the spatio-temporal variations of ecosystem WUE and its responses to drought for terrestrial ecosystems in Southwest China over the period 2000–2017. The annual WUE values varied with vegetation type in the region: Forests (3.25 gC kg−1H2O) > shrublands (2.00 gC kg−1H2O) > croplands (1.76 gC kg−1H2O) > grasslands (1.04 gC kg−1H2O). During the period 2000–2017, frequent droughts occurred in Southwest China, and overall, drought had an enhancement effect on WUE. However, the effects of drought on WUE varied with vegetation type and drought severity. Croplands were the most sensitive to drought, and slight water deficiency led to the decline of cropland WUE. Over grasslands, mild drought increased its WUE while moderate and severe drought reduced its WUE. For forests and shrublands, mild and moderate drought increased their WUE, and only severe drought reduce their WUE, indicating that these ecosystems had stronger resistance to drought. Assessing the patterns and trends of ecosystem WUE and its responses to drought are essential for understanding plant water use strategy and informing ecosystem water management.

Rapid increases in shrubland and forest intrinsic water-use efficiency during an ongoing megadrought

2021 ◽  
Vol 118 (52) ◽  
pp. e2118052118
Author(s):  
Steven A. Kannenberg ◽  
Avery W. Driscoll ◽  
Paul Szejner ◽  
William R. L. Anderegg ◽  
James R. Ehleringer
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Pinus Ponderosa ◽  
Plant Density ◽  
High Elevation ◽  
American Southwest ◽  
Past Century ◽  
Intrinsic Water Use Efficiency ◽  
Use Efficiency ◽  
Negative Impacts

Globally, intrinsic water-use efficiency (iWUE) has risen dramatically over the past century in concert with increases in atmospheric CO2 concentration. This increase could be further accelerated by long-term drought events, such as the ongoing multidecadal “megadrought” in the American Southwest. However, direct measurements of iWUE in this region are rare and largely constrained to trees, which may bias estimates of iWUE trends toward more mesic, high elevation areas and neglect the responses of other key plant functional types such as shrubs that are dominant across much of the region. Here, we found evidence that iWUE is increasing in the Southwest at one of the fastest rates documented due to the recent drying trend. These increases were particularly large across three common shrub species, which had a greater iWUE sensitivity to aridity than Pinus ponderosa, a common tree species in the western United States. The sensitivity of both shrub and tree iWUE to variability in atmospheric aridity exceeded their sensitivity to increasing atmospheric [CO2]. The shift to more water-efficient vegetation would be, all else being equal, a net positive for plant health. However, ongoing trends toward lower plant density, diminished growth, and increasing vegetation mortality across the Southwest indicate that this increase in iWUE is unlikely to offset the negative impacts of aridification.

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