scholarly journals From sink to source: high inter-annual variability in the carbon budget of a Southern African wetland

2021 ◽  
Vol 380 (2215) ◽  
Author(s):  
Carole Helfter ◽  
Mangaliso Gondwe ◽  
Michael Murray-Hudson ◽  
Anastacia Makati ◽  
Ute Skiba
Keyword(s):  
Carbon Dioxide ◽  
Primary Productivity ◽  
Continuous Monitoring ◽  
Carbon Budget ◽  
Sharp Decrease ◽  
Okavango Delta ◽  
Vegetation Types ◽  
Effects Of Drought ◽  
The Individual ◽  
Carbon Losses

We report on three years of continuous monitoring of carbon dioxide (CO 2 ) and methane (CH 4 ) emissions in two contrasting wetland areas of the Okavango Delta, Botswana: a perennial swamp and a seasonal floodplain. The hydrographic zones of the Okavango Delta possess distinct attributes (e.g. vegetation zonation, hydrology) which dictate their respective greenhouse gas (GHG) temporal emission patterns and magnitude. The perennial swamp was a net source of carbon (expressed in CO 2 -eq units), while the seasonal swamp was a sink in 2018. Despite differences in vegetation types and lifecycles, the net CO 2 uptake was comparable at the two sites studied in 2018/2020 (−894.2 ± 127.4 g m −2  yr −1 at the perennial swamp, average of the 2018 and 2020 budgets, and −1024.5 ± 134.7 g m −2  yr −1 at the seasonal floodplain). The annual budgets of CH 4 were however a factor of three larger at the permanent swamp in 2018 compared to the seasonal floodplain. Both ecosystems were sensitive to drought, which switched these sinks of atmospheric CO 2 into sources in 2019. This phenomenon was particularly strong at the seasonal floodplain (net annual loss of CO 2 of 1572.4 ± 158.1 g m −2 ), due to a sharp decrease in gross primary productivity. Similarly, drought caused CH 4 emissions at the seasonal floodplain to decrease by a factor of 4 in 2019 compared to the previous year, but emissions from the perennial swamp were unaffected. Our study demonstrates that complex and divergent processes can coexist within the same landscape, and that meteorological anomalies can significantly perturb the balance of the individual terms of the GHG budget. Seasonal floodplains are particularly sensitive to drought, which exacerbate carbon losses to the atmosphere, and it is crucial to improve our understanding of the role played by such wetlands in order to better forecast how their emissions might evolve in a changing climate. Studying such hydro-ecosystems, particularly in the data-poor tropics, and how natural stressors such as drought affect them, can also inform on the potential impacts of man-made perturbations (e.g. construction of hydro-electric dams) and how these might be mitigated. Given the contrasting effects of drought on the CO 2 and CH 4 flux terms, it is crucial to evaluate an ecosystem's complete carbon budget instead of treating these GHGs in isolation. This article is part of a discussion meeting issue ‘Rising methane: is warming feeding warming? (part 2)’.

scholarly journals Discrepancies between Global Forest Net Primary Productivity Estimates Derived from MODIS and Forest Inventory Data and Underlying Factors

2021 ◽  
Vol 13 (8) ◽  
pp. 1441
Author(s):  
Jin Han Park ◽  
Jianbang Gan ◽  
Chan Park
Keyword(s):  
Low Income ◽  
Primary Productivity ◽  
Carbon Stock ◽  
Forest Cover ◽  
Net Primary Productivity ◽  
Estimation Methods ◽  
Future Research ◽  
Important Indicator ◽  
Sequestration Potential ◽  
Carbon Losses

The net primary productivity (NPP) of a forest is an important indicator of its potential for the provision of ecosystem services such as timber, carbon, and biodiversity. However, accurately and consistently quantifying global forest NPP remains a challenge in practice. We converted carbon stock changes using the Global Forest Resources Assessment (FRA) data and carbon losses associated with disturbances and timber removals into an NPP equivalent measurement (FRA NPP*) and compared it with the NPP derived from the MODIS satellite data (MOD17 NPP) for the world’s forests. We found statistically significant differences between the two NPP estimates, with the FRA NPP* being lower than the MOD17 NPP; the differences were correlated with forest cover, normalized difference vegetation index (NDVI), and GDP per capita in countries, and may also stem from the NPP estimation methods and scopes. While the former explicitly accounts for carbon losses associated with timber removals and disturbances, the latter better reflects the principles of photosynthesis. The discrepancies between the two NPP estimates increase in countries with a low income or low forest cover, calling for enhancing their forest resource assessment capacity. By identifying the discrepancies and underlying factors, we also provide new insights into the relationships between the MOD17 NPP and global forest carbon stock estimates, motivating and guiding future research to improve the robustness of quantifying global forest NPP and carbon sequestration potential.

A comparison of the compressibilities of some gases with that of nitrogen at pressures below one atmosphere

1950 ◽  
Vol 200 (1061) ◽  
pp. 201-218 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Differential Method ◽  
Linear Extrapolation ◽  
Volume Changes ◽  
Pure Nitrogen ◽  
Molecular Weights ◽  
Nitrous Oxide Oxygen ◽  
The Individual ◽  
Straight Lines ◽  
High Degree

A differential method for comparing the compressibilities of gases at pressures below 1 atm. has been developed in which many of the errors inherent in methods employed previously have been to a large extent eliminated, especially those due to meniscus volume changes and capillary depression. Using pure nitrogen as a standard the low-pressure isothermals of carbon monoxide, carbon dioxide, nitrous oxide, oxygen, ethylene and propane have been determined at a temperature of 22-05° C. The deviations of the individual points from straight lines do not in most cases exceed 2 parts in 100,000. In no case, even with propane, was any curvature in the isotherms detectable. The contention of Moles and other recent workers that the molecular weights of liquefiable gases can be determined to a high degree of accuracy by linear extrapolation is rendered highly probable by this fresh evidence.

Continuous monitoring of gastric carbon dioxide with optical fibres

2003 ◽  
Vol 90 (1-3) ◽  
pp. 132-138 ◽  
Author(s):  
F. Baldini ◽  
A. Falai ◽  
A.R. De Gaudio ◽  
D. Landi ◽  
A. Lueger ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Continuous Monitoring ◽  
Optical Fibres

scholarly journals Effects of climatic factors on the net primary productivity in the source region of Yangtze River, China

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Zhe Yuan ◽  
Yongqiang Wang ◽  
Jijun Xu ◽  
Zhiguang Wu
Keyword(s):  
Climate Change ◽  
Primary Productivity ◽  
Yangtze River ◽  
Net Primary Productivity ◽  
Climatic Factors ◽  
Source Region ◽  
Primary Reason ◽  
Vegetation Types ◽  
Temperature And Precipitation ◽  
Increasing Trend

AbstractThe ecosystem of the Source Region of Yangtze River (SRYR) is highly susceptible to climate change. In this study, the spatial–temporal variation of NPP from 2000 to 2014 was analyzed, using outputs of Carnegie–Ames–Stanford Approach model. Then the correlation characteristics of NPP and climatic factors were evaluated. The results indicate that: (1) The average NPP in the SRYR is 100.0 gC/m2 from 2000 to 2014, and it shows an increasing trend from northwest to southeast. The responses of NPP to altitude varied among the regions with the altitude below 3500 m, between 3500 to 4500 m and above 4500 m, which could be attributed to the altitude associated variations of climatic factors and vegetation types; (2) The total NPP of SRYR increased by 0.18 TgC per year in the context of the warmer and wetter climate during 2000–2014. The NPP was significantly and positively correlated with annual temperature and precipitation at interannual time scales. Temperature in February, March, May and September make greater contribution to NPP than that in other months. And precipitation in July played a more crucial role in influencing NPP than that in other months; (3) Climatic factors caused the NPP to increase in most of the SRYR. Impacts of human activities were concentrated mainly in downstream region and is the primary reason for declines in NPP.

The Effect of Pursed - Lip Breathing Exercise Vs Diaphragmatic Breathing in Stabilizing the Vitals after 6-MWT among Overweight Individuals

2021 ◽  
Vol 9 (VIII) ◽  
pp. 299-308
Author(s):  
Dr. Jaya Chandra
Keyword(s):  
Carbon Dioxide ◽  
Data Collection ◽  
Null Hypothesis ◽  
Deep Breathing ◽  
Diaphragmatic Breathing ◽  
Breathing Exercise ◽  
Breathing Exercises ◽  
Paired Samples ◽  
The Individual ◽  
Harmful Effects

When you exercise and your muscles work harder, your body uses more oxygen and produces more carbon dioxide. To cope with this extra demand, your breathing has to increase from about 15 times a minute (12 litres of air) when you are resting, up to about 40–60 times a minute (100 litres of air) during exercise. Your circulation also speeds up to take the oxygen to the muscles so that they can keep moving. Any kind of exertion causes some change in vitals. Some amount of fluctuation in vitals after any kind of exertion occurs in every individual and is considered to be normal. But if there is extreme fluctuation in vitals even after mild or moderate form of exertion, it indicates some kind of abnormality or an increased stress on cardiovascular or respiratory system and needs attention.In any case if the vitals fluctuate during any kind of exertion it needs to be stabilized so that its harmful effects can be avoided. For these breathing exercises have been proven to be very beneficial. There are several types of breathing exercises such as deep breathing, diaphragmatic breathing, pursed lip breathing, etc. The need for the study is to compare the effectiveness of Pursed-Lip Breathing & Diaphragmatic Breathing exercise instabilizing the vitals after 6 MWT in young individuals. The objective of this study is to measure the exertion level of the individual, to assess the effect of pursed lip and diaphragmatic breathing exercises on vitals after exertion and also the comparison of both techniques. In the present study we took 60 subjects from saaii college, Kanpur. Method of data collection is random and study design is comparative study with study duration of 4 weeks. Subjects were divided into two equal groups. The paired samples t-test shows significant changes observed i.e., null hypothesis is rejected and alternate hypothesis is accepted and we observed that significant improvement along with effectiveness of pursed lip breathing on stabilizing vitals in overweight individuals.

scholarly journals Carbon dioxide fluxes over an ancient broadleaved deciduous woodland in southern England

2011 ◽  
Vol 8 (6) ◽  
pp. 1595-1613 ◽  
Author(s):  
M. V. Thomas ◽  
Y. Malhi ◽  
K. M. Fenn ◽  
J. B. Fisher ◽  
M. D. Morecroft ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Primary Productivity ◽  
Management Practices ◽  
Net Primary Productivity ◽  
Deciduous Forest ◽  
Carbon Sink ◽  
Ecosystem Respiration ◽  
Flux Chamber ◽  
Southern England ◽  
Temperate Deciduous

Abstract. We present results from a study of canopy-atmosphere fluxes of carbon dioxide from 2007 to 2009 above a site in Wytham Woods, an ancient temperate broadleaved deciduous forest in southern England. Gap-filled net ecosystem exchange (NEE) data were partitioned into gross primary productivity (GPP) and ecosystem respiration (Re) and analysed on daily, monthly and annual timescales. Over the continuous 24 month study period annual GPP was estimated to be 21.1 Mg C ha−1 yr−1 and Re to be 19.8 Mg C ha−1 yr−1; net ecosystem productivity (NEP) was 1.2 Mg C ha−1 yr−1. These estimates were compared with independent bottom-up estimates derived from net primary productivity (NPP) and flux chamber measurements recorded at a plot within the flux footprint in 2008 (GPP = 26.5 ± 6.8 Mg C ha−1 yr−1, Re = 24.8 ± 6.8 Mg C ha−1 yr−1, biomass increment = ~1.7 Mg C ha−1 yr−1). Over the two years the difference in seasonal NEP was predominantly caused by changes in ecosystem respiration, whereas GPP remained similar for equivalent months in different years. Although solar radiation was the largest influence on daily values of CO2 fluxes (R2 = 0.53 for the summer months for a linear regression), variation in Re appeared to be driven by temperature. Our findings suggest that this ancient woodland site is currently a substantial sink for carbon, resulting from continued growth that is probably a legacy of past management practices abandoned over 40 years ago. Our GPP and Re values are generally higher than other broadleaved temperate deciduous woodlands and may represent the influence of the UK's maritime climate, or the particular species composition of this site. The carbon sink value of Wytham Woods supports the protection and management of temperate deciduous woodlands (including those managed for conservation rather than silvicultural objectives) as a strategy to mitigate atmospheric carbon dioxide increases.

Carbocentric limnology: looking back, looking forward

2008 ◽  
Vol 65 (3) ◽  
pp. 543-548 ◽  
Author(s):  
Yves T Prairie
Keyword(s):  
Carbon Dioxide ◽  
Organic Matter ◽  
Microbial Community ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Carbon Budget ◽  
Metabolic Balance ◽  
Lake Ecosystems ◽  
Looking Back ◽  
Landscape Level

In this perspective article, I argue that dissolved organic carbon occupies a central role in the functioning of lake ecosystems, comparable in importance to that played by nutrients. Because lakes receive so much dissolved organic carbon from the terrestrial landscape, its accumulation in water bodies usually represents the largest pool of lacustrine organic matter within the water column. The transformation of even a small fraction of this external carbon by the microbial community can alter significantly the metabolic balance of lake ecosystems, simultaneously releasing carbon dioxide to the atmosphere and burying organic carbon in lake sediments. At the landscape level, even if they occupy a small fraction of the landscape, lakes play a surprisingly important role in the regional carbon budget, particularly when considered at the appropriate temporal scale.

scholarly journals Predicting photosynthesis and transpiration responses to ozone: decoupling modeled photosynthesis and stomatal conductance

2012 ◽  
Vol 9 (8) ◽  
pp. 3113-3130 ◽  
Author(s):  
D. Lombardozzi ◽  
S. Levis ◽  
G. Bonan ◽  
J. P. Sparks
Keyword(s):  
Carbon Dioxide ◽  
Stomatal Conductance ◽  
Primary Productivity ◽  
Environmental Conditions ◽  
Water Exchange ◽  
Global Scale ◽  
Community Land Model ◽  
Climate Regulation ◽  
The Tropics ◽  
Tulip Poplar

Abstract. Plants exchange greenhouse gases carbon dioxide and water with the atmosphere through the processes of photosynthesis and transpiration, making them essential in climate regulation. Carbon dioxide and water exchange are typically coupled through the control of stomatal conductance, and the parameterization in many models often predict conductance based on photosynthesis values. Some environmental conditions, like exposure to high ozone (O3) concentrations, alter photosynthesis independent of stomatal conductance, so models that couple these processes cannot accurately predict both. The goals of this study were to test direct and indirect photosynthesis and stomatal conductance modifications based on O3 damage to tulip poplar (Liriodendron tulipifera) in a coupled Farquhar/Ball-Berry model. The same modifications were then tested in the Community Land Model (CLM) to determine the impacts on gross primary productivity (GPP) and transpiration at a constant O3 concentration of 100 parts per billion (ppb). Modifying the Vcmax parameter and directly modifying stomatal conductance best predicts photosynthesis and stomatal conductance responses to chronic O3 over a range of environmental conditions. On a global scale, directly modifying conductance reduces the effect of O3 on both transpiration and GPP compared to indirectly modifying conductance, particularly in the tropics. The results of this study suggest that independently modifying stomatal conductance can improve the ability of models to predict hydrologic cycling, and therefore improve future climate predictions.

scholarly journals Small waterbodies reduce the carbon sink of a polygonal tundra landscape

2021 ◽  
Author(s):  
Lutz Beckebanze ◽  
Zoé Rehder ◽  
David Holl ◽  
Charlotta Mirbach ◽  
Christian Wille ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Carbon Budget ◽  
Carbon Sink ◽  
Open Water ◽  
Methane Emissions ◽  
The Arctic ◽  
Sink Strength ◽  
Small Waterbodies ◽  
Methane Fluxes ◽  
The Impact

Abstract. Arctic permafrost landscapes have functioned as a global carbon sink for millennia. These landscapes are very heterogeneous, and the omnipresent waterbodies are a carbon source within them. Yet, only a few studies focus on the impact of these waterbodies on the landscape carbon budget. We compare carbon dioxide and methane fluxes from small waterbodies to fluxes from the surrounding tundra using eddy covariance measurements from a tower located between a large pond and semi-terrestrial vegetated tundra. When taking the open-water areas of small waterbodies into account, the carbon dioxide sink strength of the landscape was reduced by 11 %. While open-water methane emissions were similar to the tundra emissions, some parts of the studied pond's shoreline exhibited much higher emissions, underlining the high spatial variability of methane emissions. We conclude that gas fluxes from small waterbodies can contribute significantly to the carbon budget of arctic tundra landscapes. Consequently, changes in arctic hydrology and the concomitant changes in the waterbody distribution may substantially impact the overall carbon budget of the Arctic.

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