Global pattern of ecosystem respiration tendencies and its implications on terrestrial carbon sink potential

Abstract As the largest component of carbon export from terrestrial ecosystems, ecosystem respiration (RECO) determines the carbon stock changes in terrestrial ecosystems. It is essential to accurately simulate the response of RECO to climate change. In this study, by constructing an optimal deep learning model for simulating global-scale RECO, we found that there is a 1–2 years' lagged response of RECO to changes in water conditions and an inconsistency in carbon input (NPP) and output (RECO) trends. The NPP growth trend in global terrestrial ecosystems is greater than that of RECO, with a trend showing increasing carbon sinks, particularly in the northern extra-tropics; while the carbon sink capacity of tropical regions has gradually saturated, showing that the changing trend of RECO is close to that of NPP, which poses a potential risk to the sustainable carbon sink capacity of global ecosystems in the future.

Download Full-text

Soil nitrogen cycle unresponsive to decadal long climate change in a Tasmanian grassland

Biogeochemistry ◽

10.1007/s10533-019-00627-9 ◽

2019 ◽

Vol 147 (1) ◽

pp. 99-107 ◽

Cited By ~ 3

Author(s):

Tobias Rütting ◽

Mark J. Hovenden

Keyword(s):

Climate Change ◽

Atmospheric Carbon Dioxide ◽

Carbon Sink ◽

Vegetation Type ◽

Terrestrial Ecosystems ◽

Soil N ◽

Mineral N ◽

N Dynamics ◽

Terrestrial Carbon Sink ◽

Soil Nitrogen Cycle

AbstractIncreases in atmospheric carbon dioxide (CO2) and global air temperature affect all terrestrial ecosystems and often lead to enhanced ecosystem productivity, which in turn dampens the rise in atmospheric CO2 by removing CO2 from the atmosphere. As most terrestrial ecosystems are limited in their productivity by the availability of nitrogen (N), there is concern about the persistence of this terrestrial carbon sink, as these ecosystems might develop a progressive N limitation (PNL). An increase in the gross soil N turnover may alleviate PNL, as more mineral N is made available for plant uptake. So far, climate change experiments have mainly manipulated one climatic factor only, but there is evidence that single-factor experiments usually overestimate the effects of climate change on terrestrial ecosystems. In this study, we investigated how simultaneous, decadal-long increases in CO2 and temperature affect the soil gross N dynamics in a native Tasmanian grassland under C3 and C4 vegetation. Our laboratory 15N labeling experiment showed that average gross N mineralization ranged from 4.9 to 11.3 µg N g−1 day−1 across the treatment combinations, while gross nitrification was about ten-times lower. Considering all treatment combinations, no significant effect of climatic treatments or vegetation type (C3 versus C4 grasses) on soil N cycling was observed.

Download Full-text

Inferring non-steady-state terrestrial vegetation carbon turnover times from multi-decadal space-borne observations on global scale

10.5194/egusphere-egu2020-17717 ◽

2020 ◽

Author(s):

Naixin Fan ◽

Simon Besnard ◽

Maurizio Santoro ◽

Oliver Cartus ◽

Nuno Carvalhais

Keyword(s):

Climate Change ◽

Steady State ◽

Carbon Fixation ◽

Carbon Sink ◽

Gross Primary Production ◽

Terrestrial Ecosystems ◽

Global Scale ◽

Turnover Time ◽

Terrestrial Vegetation ◽

Time Step

The global biomass is determined by the vegetation turnover times (&#964;) and carbon fixation through photosynthesis. Vegetation turnover time is a central parameter that not only partially determines the terrestrial carbon sink but also the response of terrestrial vegetation to the future changes in climate. However, the change of magnitude, spatial patterns and uncertainties in &#964; as well as the sensitivity of these processes to climate change is not well understood due to lack of observations on global scale. In this study, we explore a new dataset of annual above-ground biomass (AGB) change from 1993 to 2018 from spaceborne scatterometer observations. Using the long-term, spatial-explicit global dynamic dataset, we investigated how &#964; change over almost three decades including the uncertainties. Previous estimations of &#964; under steady-state assumption can now be challenged acknowledging that terrestrial ecosystems are, for the most of cases, not in balance. In this study, we explore this new dataset to derive global maps of &#964; in non-steady-state for different periods of time. We used a non-steady-state carbon model in which the change of AGB is a function of Gross Primary Production (GPP) and &#964; (&#916;AGB = &#945;*GPP-AGB/ &#964;). The parameter &#945; represents the percentage of incorporation of carbon from GPP to biomass. By exploring the AGB change in 5 to 10 years of time step, we were able to infer &#964; and &#945; from the observations of AGB and GPP change by solving the linear equation. We show how &#964; changes after potential disturbances in the early 2000s in comparison to the previous decade. We also show the spatial distributions of &#945; from the change of AGB. By accessing the change in biomass, &#964; and &#945; as well as their associated uncertainties, we provide a comprehensive diagnostic on the vegetation dynamics and the potential response of biomass to disturbance and to climate change.&#160; &#160;

Download Full-text

Riverine carbon export in the arid-semiarid Wuding River catchment on the Chinese Loess Plateau

10.5194/bg-2018-51 ◽

2018 ◽

Cited By ~ 1

Author(s):

Lishan Ran ◽

Mingyang Tian ◽

Nufang Fang ◽

Suiji Wang ◽

Xixi Lu ◽

...

Keyword(s):

Loess Plateau ◽

Carbon Sink ◽

Terrestrial Ecosystems ◽

Chinese Loess Plateau ◽

Spatial And Temporal Variability ◽

Wet Season ◽

Carbon Export ◽

Chinese Loess ◽

Carbon Burial ◽

The Chinese Loess Plateau

Abstract. Riverine export of terrestrially-derived carbon represent a key component of the global carbon cycle. In this study we quantify the redistribution of riverine carbon within the Wuding catchment on the Chinese Loess Plateau. Export of dissolved organic and inorganic carbon (DOC and DIC) exhibited pronounced spatial and temporal variability. While the DOC concentration was spatially comparable within the catchment, it was generally higher in spring and summer than in autumn, especially in the loess subcatchment. This reflects the enhanced organic matter inputs from agricultural tillage in spring and from terrestrial ecosystems in summer. DIC concentration in the loess subcatchment is significantly higher than that in the sandy subcatchment, due largely to dissolution of carbonates that are abundant in loess. In addition, content of particulate organic carbon (POC) shown strong seasonal variability with low values in the wet season owing to input of subsurface soils by gully erosion. The downstream carbon flux was (7±1.9)×1010 g C year−1 and dominated by DIC and POC. Total CO2 emissions from water surface were (3.7±0.5)×1010 g C year−1. Radiocarbon analysis revealed that the degassed CO2 was 810–1890 years old, indicating the release of old carbon previously stored in soil horizons. Riverine carbon export in the Wuding catchment has been greatly modified by check dams. Our estimate shows that carbon burial through sediment storage was (7.8±4.1)×1010 g C year−1, representing 42% of the total riverine carbon export from terrestrial ecosystems on an annual basis ((18.5±4.5)×1010 g C year−1). Moreover, the riverine carbon export accounted for 16 % of the catchment NEP. It appears that the magnitude of carbon sink of terrestrial ecosystems in this arid-semiarid catchment has been significantly offset by riverine carbon export.

Download Full-text

Carbon leaks from flooded land: do we need to re-plumb the inland water active pipe?

10.5194/bg-2018-239 ◽

2018 ◽

Cited By ~ 1

Author(s):

Gwenaël Abril ◽

Alberto V. Borges

Keyword(s):

Ecosystem Respiration ◽

Terrestrial Ecosystems ◽

Global Scale ◽

Inland Waters ◽

Organic C ◽

Wetland Ecosystems ◽

High Productivity ◽

Biogeochemical Models ◽

Waterlogged Soils ◽

The Tropics

Abstract. At the global scale, inland waters are a significant source of atmospheric carbon (C), particularly in the tropics. The active pipe concept predicts that C emissions from streams, lakes and rivers are largely fuelled by terrestrial ecosystems. The traditionally recognized C transfer mechanisms from terrestrial to aquatic systems are surface runoff and groundwater drainage. We present here a series of arguments that support the idea that land flooding is an additional significant process that fuels inland waters with C at the global scale. Whether the majority of CO2 emitted by rivers comes from floodable land (approximately 10 % of the continents) or from well-drained land is a fundamental question that impacts our capacity to predict how these C fluxes might change in the future. Using classical concepts in ecology, we propose, as a necessary step forward, an update of the active pipe concept that differentiates floodable land from drained land. Contrarily to well-drained land, wetlands combine strong hydrological connectivity with inland waters, high productivity assimilating CO2 from the atmosphere, direct transfer of litter and exudation products to water and waterlogged soils, a generally dominant allocation of ecosystem respiration below the water surface and a slow gas exchange rate at the water-air interface. These properties force plants to pump atmospheric C to wetland waters and, when hydrology is favourable, to inland waters as organic C and dissolved CO2. This wetland CO2 pump may contribute disproportionately to CO2 emissions from inland waters, particularly in the tropics, and consequently at the global scale. In future studies, more care must be taken in the way that vertical and horizontal C fluxes are conceptualized along watersheds and 2D-models that adequately account for the hydrological export of all C species are necessary. In wetland ecosystems, significant effort should be dedicated to quantifying the components of primary production and respiration in air, water and waterlogged soils, and these metabolic rates should be used in coupled hydrological-biogeochemical models. The construction of a global typology of wetlands also appears necessary to adequately integrate continental C fluxes at the global scale.

Download Full-text

Projecting long-term soil organic dynamics in Australia's rangelands

10.5194/ismc2021-92 ◽

2021 ◽

Author(s):

Mingxi Zhang ◽

Raphael Viscarra Rossel

Keyword(s):

Short Term Memory ◽

Carbon Sink ◽

Soil C ◽

Tropical Regions ◽

Explanatory Variables ◽

The North ◽

Terrestrial Carbon Sink ◽

Organic Carbon Stock ◽

Trees And Shrubs

Rangelands in Australia are vast and occupy more than 80% of the continental land area. They extend across arid, semi-arid, and the tropical regions with seasonal, variable rainfall in the north. They include diverse, relatively undisturbed grasslands, shrublands, woodlands and tropical savanna ecosystems. They represent Australia&#8217;s largest terrestrial carbon sink as they account for almost 70% of Australia's total soil organic carbon stock (Viscarra Rossel et al., 2014), more than all above-ground sources of carbon (native grasses, trees and shrubs) in these regions (Gifford et al., 1992). Here we have developed a novel space-time approach for projecting the long-term C dynamics of rangelands soils using Long Short-Term Memory (LSTM) deep learning neural networks. We further demonstrate how the networks might be interpreted and quantified the influence of explanatory variables on the spatiotemporal dynamics of soil C in these regions. Our results provide an improved ability to accurately model long-term carbon dynamics, which is needed to confidently predict changes in soil C from change in climate or anthropogenic disturbance. The information is critical for improving our understanding of soil C in these regions and for understanding the potential for sequestering C in the rangelands.

Download Full-text

Calculation of Terrestrial Carbon Sink Capacity in Dongying City, Shandong Province

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.734-737.1901 ◽

2013 ◽

Vol 734-737 ◽

pp. 1901-1904

Author(s):

Zi Jun Li

Keyword(s):

Carbon Sink ◽

Environmental Crisis ◽

Low Carbon ◽

Wetland Ecosystem ◽

Terrestrial Carbon ◽

Sink Capacity ◽

Excessive Consumption ◽

Rapid Transition ◽

Terrestrial Carbon Sink ◽

Dongying City

Based on the reality of Dongying City, combined with relevant statistical data, the carbon sink capacity of the forest ecosystem, wetland ecosystem, landscaping ecosystem and farmland ecosystem in Dongying City was calculated systematically by using the empirical coefficient method. The results showed that the carbon sink capacity of terrestrial ecological system in Dongying City was about 596.72×104 t CO2 in 2009, and wetland ecosystem, whose carbon sink capacity accounted for 84.82% of the total terrestrial carbon sink, was the major terrestrial carbon sink of Dongying City. The research results have important significance for Dongying City in rapid transition to low carbon ecological development, mitigating and avoiding the environmental crisis resulted from high carbon development as well as resources crisis caused by energy excessive consumption, and realizing sustainable development.

Download Full-text

Ideas and perspectives: Carbon leaks from flooded land: do we need to replumb the inland water active pipe?

Biogeosciences ◽

10.5194/bg-16-769-2019 ◽

2019 ◽

Vol 16 (3) ◽

pp. 769-784 ◽

Cited By ~ 15

Author(s):

Gwenaël Abril ◽

Alberto V. Borges

Keyword(s):

Co2 Emissions ◽

Ecosystem Respiration ◽

Terrestrial Ecosystems ◽

Global Scale ◽

Hydrological Connectivity ◽

Inland Waters ◽

Organic C ◽

High Productivity ◽

Biogeochemical Models ◽

The Tropics

Abstract. At the global scale, inland waters are a significant source of atmospheric carbon (C), particularly in the tropics. The active pipe concept predicts that C emissions from streams, lakes and rivers are largely fuelled by terrestrial ecosystems. The traditionally recognized C transfer mechanisms from terrestrial to aquatic systems are surface runoff and groundwater drainage. We present here a series of arguments that support the idea that land flooding is an additional significant process that fuels inland waters with C at the global scale. Whether the majority of CO2 emitted by rivers comes from floodable land (approximately 10 % of the continents) or from well-drained land is a fundamental question that impacts our capacity to predict how these C fluxes might change in the future. Using classical concepts in ecology, we propose, as a necessary step forward, an update of the active pipe concept that differentiates floodable land from drained land. Contrarily to well-drained land, many wetlands (in particular riparian and littoral wetlands) combine strong hydrological connectivity with inland waters, high productivity assimilating CO2 from the atmosphere, direct transfer of litter and exudation products to water and waterlogged soils, a generally dominant allocation of ecosystem respiration (ER) below the water surface and a slow gas-exchange rate at the water–air interface. These properties force plants to pump atmospheric C to wetland waters and, when hydrology is favourable, to inland waters as organic C and dissolved CO2. This wetland CO2 pump may contribute disproportionately to CO2 emissions from inland waters, particularly in the tropics where 80 % of the global CO2 emissions to the atmosphere occur. In future studies, more care must be taken in the way that vertical and horizontal C fluxes are conceptualized along watersheds, and 2-D models that adequately account for the hydrological export of all C species are necessary. In flooded ecosystems, significant effort should be dedicated to quantifying the components of primary production and respiration by the submerged and emerged part of the ecosystem community and to using these metabolic rates in coupled hydrological–biogeochemical models. The construction of a global typology of wetlands that includes productivity, gas fluxes and hydrological connectivity with inland waters also appears necessary to adequately integrate continental C fluxes at the global scale.

Download Full-text

Recent pause in the growth rate of atmospheric CO2 due to enhanced terrestrial carbon uptake

Nature Communications ◽

10.1038/ncomms13428 ◽

2016 ◽

Vol 7 (1) ◽

Cited By ~ 130

Author(s):

Trevor F Keenan ◽

I. Colin Prentice ◽

Josep G Canadell ◽

Christopher A Williams ◽

Han Wang ◽

...

Keyword(s):

Growth Rate ◽

Carbon Sink ◽

Large Fraction ◽

Terrestrial Ecosystems ◽

Anthropogenic Emissions ◽

Terrestrial Carbon ◽

Vegetation Models ◽

Terrestrial Carbon Sink ◽

Global Vegetation ◽

Global Carbon

Abstract Terrestrial ecosystems play a significant role in the global carbon cycle and offset a large fraction of anthropogenic CO2 emissions. The terrestrial carbon sink is increasing, yet the mechanisms responsible for its enhancement, and implications for the growth rate of atmospheric CO2, remain unclear. Here using global carbon budget estimates, ground, atmospheric and satellite observations, and multiple global vegetation models, we report a recent pause in the growth rate of atmospheric CO2, and a decline in the fraction of anthropogenic emissions that remain in the atmosphere, despite increasing anthropogenic emissions. We attribute the observed decline to increases in the terrestrial sink during the past decade, associated with the effects of rising atmospheric CO2 on vegetation and the slowdown in the rate of warming on global respiration. The pause in the atmospheric CO2 growth rate provides further evidence of the roles of CO2 fertilization and warming-induced respiration, and highlights the need to protect both existing carbon stocks and regions, where the sink is growing rapidly.

Download Full-text

Climate-driven shifts in sediment chemistry enhance methane production in northern lakes

10.1101/161653 ◽

2017 ◽

Author(s):

E.J.S Emilson ◽

M.A. Carson ◽

K.M. Yakimovich ◽

J.M. Gunn ◽

N.C.S Mykytczuk ◽

...

Keyword(s):

Carbon Sink ◽

Typha Latifolia ◽

Global Scale ◽

Freshwater Ecosystems ◽

Sediment Chemistry ◽

Littoral Sediments ◽

Terrestrial Carbon Sink ◽

Earth System Models ◽

Global Carbon

AbstractFreshwater ecosystems are a major source of methane (CH4), contributing 0.65 Pg (in CO2 equivalents) yr-1 towards global carbon (C) emissions and thereby offsetting ∼25% of the terrestrial carbon sink. Most CH4 emissions come from littoral sediments, where large quantities of plant material are decomposed. As climate change is predicted to shift plant community composition, and thus change the quality of inputs into detrital food webs, this can affect CH4 production and have far-reaching consequences for global C emissions. Here we find that variation in polyphenol availability from decomposing organic matter underlies large differences in CH4 production in lake sediments. Production was at least 400-times higher from sediments composed of macrophyte litter compared to terrestrial sources (coniferous and deciduous), which we link to the inhibition of methanogenesis by polyphenol leachates. Applying our estimates to projected northward advances in the distribution of Typha latifolia, a widespread and dominant macrophyte, we find that CH4 production could increase by at least 73% in the lake-rich Boreal Shield ecozone solely due to increases in this one macrophyte species. Our results now suggest that earth system models and carbon budgets should consider the effects of plant communities on sediment chemistry and ultimately CH4 emissions at a global scale.One-sentence summaryProduction of methane from lakes is at least 400-times lower when 24 sediments receive forest- as opposed to macrophyte-derived (Typha latifolia) litterfall.

Download Full-text

Twentieth-Century Droughts and Their Impacts on Terrestrial Carbon Cycling in China

Earth Interactions ◽

10.1175/2009ei275.1 ◽

2009 ◽

Vol 13 (10) ◽

pp. 1-31 ◽

Cited By ~ 83

Author(s):

Jingfeng Xiao ◽

Qianlai Zhuang ◽

Eryuan Liang ◽

Xuemei Shao ◽

A. David McGuire ◽

...

Keyword(s):

Twentieth Century ◽

Carbon Cycling ◽

Carbon Balance ◽

Carbon Sink ◽

Ring Width ◽

Terrestrial Ecosystems ◽

Terrestrial Carbon ◽

Terrestrial Ecosystem Model ◽

Terrestrial Carbon Sink ◽

Drought Effects

Abstract Midlatitude regions experienced frequent droughts during the twentieth century, but their impacts on terrestrial carbon balance are unclear. This paper presents a century-scale study of drought effects on the carbon balance of terrestrial ecosystems in China. The authors first characterized the severe extended droughts over the period 1901–2002 using the Palmer drought severity index and then examined how these droughts affected the terrestrial carbon dynamics using tree-ring width chronologies and a process-based biogeochemistry model, the Terrestrial Ecosystem Model (TEM). It is found that China suffered from a series of severe extended droughts during the twentieth century. The major drought periods included 1920–30, 1939–47, 1956–58, 1960–63, 1965–68, 1978–80, and 1999–2002. Most droughts generally reduced net primary productivity (NPP) and net ecosystem productivity (NEP) in large parts of drought-affected areas. Moreover, some of the droughts substantially reduced the countrywide annual NPP and NEP. Out of the seven droughts, three (1920–30, 1965–68, and 1978–80) caused the countrywide terrestrial ecosystems to switch from a carbon sink to a source, and one (1960–63) substantially reduced the magnitude of the countrywide terrestrial carbon sink. Strong decreases in NPP were mainly responsible for the anomalies in annual NEP during these drought periods. Changes in heterotrophic respiration happened in the same direction, but mostly with smaller magnitude. The results show that severe extended droughts had significant effects on terrestrial carbon cycling in China, although future studies should consider other important processes such as drought-induced mortality and regrowth, land-use change, disturbances (e.g., fire), human management (e.g., fertilization and irrigation), and environmental pollution (e.g., ozone pollution, nitrogen deposition). These drought effects are of particular importance in light of projected widespread summer drying in midlatitude regions during the twenty-first century. Future droughts could lead to a reduced terrestrial carbon sink or even a source and exert a positive feedback to the global climate system.

Download Full-text