scholarly journals Carbon dioxide flux and net primary production of a boreal treed bog: responses to warming and water table manipulations

2014 ◽  
Vol 11 (9) ◽  
pp. 12937-12983 ◽  
Author(s):  
T. M. Munir ◽  
M. Perkins ◽  
E. Kaing ◽  
M. Strack
Keyword(s):  
Carbon Dioxide ◽  
Primary Production ◽  
Water Level ◽  
Water Table ◽  
Forest Floor ◽  
Net Primary Production ◽  
Carbon Dioxide Flux ◽  
Water Levels ◽  
Co2 Uptake ◽  
Experimental Site

Abstract. Mid-latitude treed bogs are significant carbon (C) stocks and are highly sensitive to global climate change. In a dry continental treed bog, we compared three sites; control, recent (1–3 years; experimental) and older drained (10–13 years; drained) with water levels at 38, 74 and 120 cm below the surface, respectively. At each site we measured carbon dioxide (CO2) fluxes and tree root respiration (Rr) (across hummock-hollow microtopography of the forest floor) and net primary production (NPP) of trees during the growing seasons (May to October) of 2011–2013. The carbon (C) balance was calculated by adding net CO2 exchange of the forest floor (NEff–Rr) to the NPP of the trees. From cooler and wetter 2011 to driest and warmest 2013, The control site was a~C sink of 92, 70 and 76 g m−2, experimental site was a C source of 14, 57 and 135 g m−2, and drained site was a progressively smaller source of 26, 23 and 13 g m−2, respectively. Although all microforms at the experimental site had large net CO2 emissions, the longer-term drainage and deeper water level at the drained site resulted in the replacement of mosses with vascular plants (shrubs) at the hummocks and lichens at the hollows leading to the highest CO2 uptake at drained hummocks and significant losses at hollows. The tree NPP was highest at the drained site. We also quantified the impact of climatic warming at all water table treatments by equipping additional plots with open-top chambers (OTCs) that caused a passive warming on average of ∼1 °C and differential air warming of ∼6 °C (at mid-day full sun) across the study years. Warming significantly enhanced the shrub growth and CO2 sink function of the drained hummocks (exceeding the cumulative respiration losses at hollows induced by the lowered water level × warming). There was an interaction of water level with warming across hummocks that resulted in largest net CO2 uptake at warmed drained hummocks. Thus in 2013, the warming treatment enhanced the sink function of control by 13 g m−2, reduced the source function of experimental by 10 g m−2, and significantly enhanced the sink function of the drained site by 73 g m−2. Therefore, drying and warming in continental bogs is expected to initially accelerate C losses via respiration but persistent drought and warming is expected to restore the peatland's original C sink function as a result of transitional shift of vegetation between the microforms and increased NPP of trees over time.

scholarly journals Carbon dioxide flux and net primary production of a boreal treed bog: Responses to warming and water-table-lowering simulations of climate change

2015 ◽  
Vol 12 (4) ◽  
pp. 1091-1111 ◽  
Author(s):  
T. M. Munir ◽  
M. Perkins ◽  
E. Kaing ◽  
M. Strack
Keyword(s):  
Climate Change ◽  
Carbon Dioxide ◽  
Primary Production ◽  
Water Level ◽  
Water Table ◽  
Forest Floor ◽  
Net Primary Production ◽  
Control Site ◽  
Co2 Uptake ◽  
Experimental Site

Abstract. Midlatitude treed bogs represent significant carbon (C) stocks and are highly sensitive to global climate change. In a dry continental treed bog, we compared three sites: control, recent (1–3 years; experimental) and older drained (10–13 years), with water levels at 38, 74 and 120 cm below the surface, respectively. At each site we measured carbon dioxide (CO2) fluxes and estimated tree root respiration (Rr; across hummock–hollow microtopography of the forest floor) and net primary production (NPP) of trees during the growing seasons (May to October) of 2011–2013. The CO2–C balance was calculated by adding the net CO2 exchange of the forest floor (NEff-Rr) to the NPP of the trees. From cooler and wetter 2011 to the driest and the warmest 2013, the control site was a CO2–C sink of 92, 70 and 76 g m−2, the experimental site was a CO2–C source of 14, 57 and 135 g m−2, and the drained site was a progressively smaller source of 26, 23 and 13 g CO2–C m−2. The short-term drainage at the experimental site resulted in small changes in vegetation coverage and large net CO2 emissions at the microforms. In contrast, the longer-term drainage and deeper water level at the drained site resulted in the replacement of mosses with vascular plants (shrubs) on the hummocks and lichen in the hollows leading to the highest CO2 uptake at the drained hummocks and significant losses in the hollows. The tree NPP (including above- and below-ground growth and litter fall) in 2011 and 2012 was significantly higher at the drained site (92 and 83 g C m−2) than at the experimental (58 and 55 g C m−2) and control (52 and 46 g C m−2) sites. We also quantified the impact of climatic warming at all water table treatments by equipping additional plots with open-top chambers (OTCs) that caused a passive warming on average of ~ 1 °C and differential air warming of ~ 6 °C at midday full sun over the study years. Warming significantly enhanced shrub growth and the CO2 sink function of the drained hummocks (exceeding the cumulative respiration losses in hollows induced by the lowered water level × warming). There was an interaction of water level with warming across hummocks that resulted in the largest net CO2 uptake at the warmed drained hummocks. Thus in 2013, the warming treatment enhanced the sink function of the control site by 13 g m−2, reduced the source function of the experimental by 10 g m−2 and significantly enhanced the sink function of the drained site by 73 g m−2. Therefore, drying and warming in continental bogs is expected to initially accelerate CO2–C losses via ecosystem respiration, but persistent drought and warming is expected to restore the peatland's original CO2–C sink function as a result of the shifts in vegetation composition and productivity between the microforms and increased NPP of trees over time.

Ecosystem modeling of methane and carbon dioxide fluxes for boreal forest sites

2001 ◽  
Vol 31 (2) ◽  
pp. 208-223 ◽  
Author(s):  
Christopher Potter ◽  
Jill Bubier ◽  
Patrick Crill ◽  
Peter Lafleur
Keyword(s):  
Carbon Dioxide ◽  
Boreal Forest ◽  
Land Surface ◽  
Net Primary Production ◽  
Ground Cover ◽  
Methane Flux ◽  
Growing Season ◽  
Ecosystem Model ◽  
Heat Fluxes ◽  
Water Levels

Predicted daily fluxes from an ecosystem model for water, carbon dioxide, and methane were compared with 1994 and 1996 Boreal Ecosystem–Atmosphere Study (BOREAS) field measurements at sites dominated by old black spruce (Picea mariana (Mill.) BSP) (OBS) and boreal fen vegetation near Thompson, Man. Model settings for simulating daily changes in water table depth (WTD) for both sites were designed to match observed water levels, including predictions for two microtopographic positions (hollow and hummock) within the fen study area. Water run-on to the soil profile from neighboring microtopographic units was calibrated on the basis of daily snowmelt and rainfall inputs to reproduce BOREAS site measurements for timing and magnitude of maximum daily WTD for the growing season. Model predictions for daily evapotranspiration rates closely track measured fluxes for stand water loss in patterns consistent with strong controls over latent heat fluxes by soil temperature during nongrowing season months and by variability in relative humidity and air temperature during the growing season. Predicted annual net primary production (NPP) for the OBS site was 158 g C·m–2 during 1994 and 135 g C·m–2 during 1996, with contributions of 75% from overstory canopy production and 25% from ground cover production. Annual NPP for the wetter fen site was 250 g C·m–2 during 1994 and 270 g C·m–2 during 1996. Predicted seasonal patterns for soil CO2 fluxes and net ecosystem production of carbon both match daily average estimates at the two sites. Model results for methane flux, which also closely match average measured flux levels of –0.5 mg CH4·m–2·day–1 for OBS and 2.8 mg CH4·m–2·day–1 for fen sites, suggest that spruce areas are net annual sinks of about –0.12 g CH4·m–2, whereas fen areas generate net annual emissions on the order of 0.3–0.85 g CH4·m–2, depending mainly on seasonal WTD and microtopographic position. Fen hollow areas are predicted to emit almost three times more methane during a given year than fen hummock areas. The validated model is structured for extrapolation to regional simulations of interannual trace gas fluxes over the entire North America boreal forest, with integration of satellite data to characterize properties of the land surface.

scholarly journals Short-term Effects of Grazing Exclusion on Net Ecosystem CO2 Exchange and Net Primary Production in a Pannonian Sandy Grassland

2012 ◽  
Vol 40 (2) ◽  
pp. 67 ◽  
Author(s):  
Szilard CZOBEL ◽  
Orsolya SZIRMAI ◽  
Zoltan NEMETH ◽  
Csaba GYURICZA ◽  
Judit GAZI ◽  
...  
Keyword(s):  
Carbon Sequestration ◽  
Primary Production ◽  
Net Primary Production ◽  
Plant Productivity ◽  
Co2 Exchange ◽  
Co2 Uptake ◽  
Aboveground Phytomass ◽  
Grazing Exclusion ◽  
Sequestration Potential ◽  
Sandy Grassland

Using portable, non-destructive own developed chambers (d=60 cm) and infrared gas analyses, the in situ field investigation was performed to study the seasonal and inter-annual dynamics of the stand level CO2-flux and production of sandy grassland that has been extensively grazed for decades. Furthermore, NEE measurements and biomass samples were used to identify the initial effects of grazing exclusion on CO2 exchange, aboveground phytomass and potential plant productivity in years of significantly different precipitation levels. A considerable inter-annual variation in all of the studied parameters was found both in the non-grazed and grazed stands. As a result of the grazing exclusion the CO2 uptake potential of the non-grazed stand increased by 13% compared to the grazed stand. It was more significant in the extreme dry year (220%), however, in wet year slightly lower average carbon sequestration was detected at the non-grazed stand (-13%), than that of the grazed area. Significant carbon sequestration potential was only detected during wet periods in both stands. The rate of CO2 uptake was found to be nearly six times higher in the non-grazed stand in the wet year than in the previous extremely dry year. The drought in 2003 significantly reduced the CO2 uptake of both stands, leading to lower annual net primary production and potential plant productivity. The annual net primary production dropped by almost 40% in the extremely dry year but then it rose by nearly two and a half times in the subsequent year with adequate rainfall.

scholarly journals Methane and carbon dioxide flux in the profile of wood ant (Formica aquilonia) nests and the surrounding forest floor during a laboratory incubation

2016 ◽  
Vol 92 (10) ◽  
pp. fiw141 ◽  
Author(s):  
Veronika Jílková ◽  
Tomáš Picek ◽  
Martina Šestauberová ◽  
Václav Krištůfek ◽  
Tomáš Cajthaml ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Forest Floor ◽  
Carbon Dioxide Flux ◽  
Laboratory Incubation ◽  
Formica Aquilonia

scholarly journals Marine biogeochemical cycling and oceanic CO<sub>2</sub> uptake simulated by the NUIST Earth System Model version 3

2019 ◽  
Author(s):  
Yifei Dai ◽  
Long Cao ◽  
Bin Wang
Keyword(s):  
Primary Production ◽  
Large Scale ◽  
Net Primary Production ◽  
Earth System Model ◽  
System Model ◽  
Upper Ocean ◽  
Carbon Uptake ◽  
Co2 Uptake ◽  
Earth System ◽  
Cmip5 Model

Abstract. In this study, we evaluate the performance of Nanjing University of Information Science and Technology Earth System Model, version 3 (hereafter NESM v3) in simulating the marine biogeochemical cycle and CO2 uptake. Compared with observations, NESM v3 reproduces reasonably well the large-scale patterns of upper ocean biogeochemical fields including nutrients, alkalinity, dissolved inorganic, chlorophyll, and net primary production. The model also reasonably reproduces current-day oceanic CO2 uptake, the total CO2 uptake is 149 PgC from 1850 to 2016. In the 1ptCO2 experiment, the NESM v3 produced carbon-climate (γ=-7.9 PgC/K) and carbon-concentration sensitivity parameters (β=0.8 PgC/ppm) are comparable with CMIP5 model results. The nonlinearity of carbon uptake in the NESM v3 accounts for 10.3% of the total carbon uptake, which is within the range of CMIP5 model results (3.6%~10.6%). Some regional discrepancies between model simulations and observations are identified and the possible causes are investigated. In the upper ocean, the simulated biases in biogeochemical fields are mainly associated with the shortcoming in simulated ocean circulation. Weak upwelling in the Indian Ocean suppresses the nutrient entrainment to the upper ocean, therefore reducing the biological activities and resulting in underestimation of net primary production and chlorophyll concentration. In the Pacific and the Southern Ocean, high-nutrient and low-chlorophyll result from the strong iron limitation. Alkalinity shows high biases in high-latitude oceans due to the strong convective mixing. The major discrepancy in biogeochemical fields is seen in the deep Northern Pacific. The simulated high concentration of nutrients, alkalinity and dissolved inorganic carbon water is too deep due to the excessive deep ocean remineralization. Despite these model-observation discrepancies, it is expected that the NESM v3 can be employed as a useful modeling tool to investigate large scale interactions between the ocean carbon cycle and climate change.

scholarly journals Particle Tracking Using Dynamic Water-Level Data

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 2063
Author(s):  
Yuan Gao
Keyword(s):  
Groundwater Flow ◽  
Water Level ◽  
Water Table ◽  
Flow Direction ◽  
Water Levels ◽  
Subsurface Water ◽  
Pressure Transducers ◽  
Level Data ◽  
Water Level Data ◽  
Fluid Particles

The movement of fluid particles about historic subsurface releases is often governed by dynamic subsurface water levels. Motivations for tracking the movement of fluid particles include tracking the fate of subsurface contaminants and resolving the fate of water stored in subsurface aquifers. This study provides a novel method for predicting the movement of subsurface particles relying on dynamic water-level data derived from continuously recording pressure transducers. At least three wells are needed to measure water levels which are used to determine the plain of the water table. Based on Darcy’s law, particle flow pathlines at the study site are obtained using the slope of the water table. The results show that hydrologic conditions, e.g., seasonal transpiration and precipitation, influence local groundwater flow. The changes of water level in short periods caused by the hydrologic variations made the hydraulic gradient diversify considerably, thus altering the direction of groundwater flow. Although a range of groundwater flow direction and gradient with time can be observed by an initial review of water levels in rose charts, the net groundwater flow at all field sites is largely constant in one direction which is driven by the gradients with higher magnitude.

scholarly journals Fire, hurricane and carbon dioxide: effects on net primary production of a subtropical woodland

2013 ◽  
Vol 200 (3) ◽  
pp. 767-777 ◽  
Author(s):  
Bruce A. Hungate ◽  
Frank P. Day ◽  
Paul Dijkstra ◽  
Benjamin D. Duval ◽  
C. Ross Hinkle ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Primary Production ◽  
Net Primary Production

scholarly journals Classical Karst hydrodynamics: a shared aquifer within Italy and Slovenia

2014 ◽  
Vol 364 ◽  
pp. 499-504 ◽  
Author(s):  
L. Zini ◽  
C. Calligaris ◽  
E. Zavagno
Keyword(s):  
Comparative Analysis ◽  
Water Level ◽  
River Water ◽  
Water Table ◽  
Water Levels ◽  
Transboundary Aquifer ◽  
Precise Evaluation ◽  
Transit Times ◽  
Two Sectors ◽  
Temperature Water

Abstract. The classical Karst transboundary aquifer is a limestone plateau of 750 km2 that extends from Brkini hills in Slovenia to Isonzo River in Italy. For 20 years, and especially in the last two years, the Mathematic and Geosciences Department of Trieste University has run a monitoring project in order to better understand the groundwater hydrodynamics and the relation between the fracture and conduit systems. A total of 14 water points, including caves, springs and piezometers are monitored and temperature, water level and EC data are recorded. Two sectors are highlighted: the southeastern sector mainly influenced by the sinking of the Reka River, and a northwestern sector connected to the influent character of the Isonzo River. Water table fluctuations are significant, with risings of > 100 m. During floods most of the circuits are under pressure, and only a comparative analysis of water levels, temperature and EC permits a precise evaluation of the water transit times in fractured and/or karstified volumes.

Microbial primary production and phototrophy

2018 ◽  
Author(s):  
David L. Kirchman
Keyword(s):  
Carbon Dioxide ◽  
Primary Production ◽  
Microbial Mats ◽  
Higher Plants ◽  
Net Primary Production ◽  
Terrestrial Plants ◽  
Anoxygenic Photosynthesis ◽  
Photosynthetic Organisms ◽  
Anoxic Environments ◽  
Large Numbers

This chapter is focused on the most important process in the biosphere, primary production, the turning of carbon dioxide into organic material by higher plants, algae, and cyanobacteria. Photosynthetic microbes account for roughly 50% of global primary production while the other half is by large, terrestrial plants. After reviewing the basic physiology of photosynthesis, the chapter discusses approaches to measuring gross and net primary production and how these processes affect fluxes of oxygen and carbon dioxide into and out of aquatic ecosystems. It then points out that terrestrial plants have high biomass but relatively low growth, while the opposite is the case for aquatic algae and cyanobacteria. Primary production varies greatly with the seasons in temperate ecosystems, punctuated by the spring bloom when the biomass of one algal type, diatoms, reaches a maximum. Other abundant algal types include coccolithophorids in the oceans and filamentous cyanobacteria in freshwaters. After the bloom, small algae take over and out-compete larger forms for limiting nutrients because of superior uptake kinetics. Abundant types of small algae include two coccoid cyanobacteria, Synechococcus and Prochlorococcus, the latter said to be the most abundant photoautotroph on the planet because of its large numbers in oligotrophic oceans. Other algae, often dinoflagellates, are toxic. Many algae can also graze on other microbes, probably to obtain limiting nitrogen or phosphorus. Still other microbes are mainly heterotrophic but are capable of harvesting light energy. Primary production in oxic environments is carried out by oxygenic photosynthetic organisms, whereas in anoxic environments with sufficient light, it is anaerobic anoxygenic photosynthesis in which oxygen is not produced. Although its contribution to global primary production is small, anoxygenic photosynthesis helps us understand the biophysics and biochemistry of photosynthesis and its evolution on early Earth. These microbes as well as aerobic phototrophic and heterotrophic microbes make up microbial mats. These mats can provide insights into early life on the planet when a type of mat, “stromatolites,” covered vast areas of primordial seas in the Proterozoic.

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