scholarly journals Temperature, moisture and freeze–thaw controls on CO2 production in soil incubations from northern peatlands

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Eunji Byun ◽  
Fereidoun Rezanezhad ◽  
Linden Fairbairn ◽  
Stephanie Slowinski ◽  
Nathan Basiliko ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Carbon Sink ◽  
Growing Season ◽  
Co2 Production ◽  
Sudden Increase ◽  
Production Rates ◽  
Apparent Lack ◽  
Freeze Thaw ◽  
Standard Reaction ◽  
Northern Peatlands

AbstractPeat accumulation in high latitude wetlands represents a natural long-term carbon sink, resulting from the cumulative excess of growing season net ecosystem production over non-growing season (NGS) net mineralization in soils. With high latitudes experiencing warming at a faster pace than the global average, especially during the NGS, a major concern is that enhanced mineralization of soil organic carbon will steadily increase CO2 emissions from northern peatlands. In this study, we conducted laboratory incubations with soils from boreal and temperate peatlands across Canada. Peat soils were pretreated for different soil moisture levels, and CO2 production rates were measured at 12 sequential temperatures, covering a range from − 10 to + 35 °C including one freeze–thaw event. On average, the CO2 production rates in the boreal peat samples increased more sharply with temperature than in the temperate peat samples. For same temperature, optimum soil moisture levels for CO2 production were higher in the peat samples from more flooded sites. However, standard reaction kinetics (e.g., Q10 temperature coefficient and Arrhenius equation) failed to account for the apparent lack of temperature dependence of CO2 production rates measured below 0 °C, and a sudden increase after a freezing event. Thus, we caution against using the simple kinetic expressions to represent the CO2 emissions from northern peatlands, especially regarding the long NGS period with multiple soil freeze and thaw events.

scholarly journals Assessing the influence of soil freeze-thaw cycles on catchment water storage – flux – age interactions using a tracer-aided ecohydrological model

2019 ◽  
Author(s):  
Aaron A. Smith ◽  
Doerthe Tetzlaff ◽  
Hjalmar Laudon ◽  
Marco Maneta ◽  
Chris Soulsby
Keyword(s):  
Soil Moisture ◽  
Growing Season ◽  
Winter Period ◽  
Soil Frost ◽  
Freeze Thaw ◽  
Stream Discharge ◽  
Spatial Differences ◽  
Ecohydrological Model ◽  
Vegetation Water ◽  
Storage Flux

Abstract. Ecohydrological models are powerful tools to quantify the effects that independent fluxes may have on catchment storage dynamics. Here, we adapted the tracer-aided ecohydrological model, EcH2O-iso, for cold regions with the explicit conceptualisation of dynamic soil freeze-thaw processes. We tested the model at the data-rich Krycklan site in northern Sweden with multi-criteria calibration using discharge, stream isotopes and soil moisture in 3 nested catchments. We utilized the model’s incorporation of ecohydrological partitioning to evaluate the effect of soil frost on evaporation and transpiration water ages, and thereby the age of source waters. The simulation of stream discharge, isotopes, and soil moisture variability captured the seasonal dynamics at all three stream sites and both soil sites, with notable reductions in discharge and soil moisture during the winter months due to the development of the frost front. Stream isotope simulations reproduced the response to the isotopically-depleted pulse of spring snowmelt. The soil frost dynamics adequately captured the spatial differences in the freezing-front throughout the winter period, despite no direct calibration of soil frost to measured soil temperature. The simulated soil frost indicated a maximum freeze-depth of 0.25 m below forest vegetation. Water ages of evaporation and transpiration reflect the influence of snowmelt-inputs, with a high proclivity of old water (pre-winter storage) at the beginning of the growing season and a mix of snowmelt and precipitation (young water) toward the end of the summer. Soil frost had an early season influence of the transpiration water ages, with water pre-dating the snowpack mainly sustaining vegetation at the start of the growing season. Given the long-term expected change in the energy-balance of northern climates, the approach presented provides a framework for quantifying the interactions of ecohydrological fluxes and waters stored in the soil and understanding how these may be impacted in future.

scholarly journals Assessing the influence of soil freeze–thaw cycles on catchment water storage–flux–age interactions using a tracer-aided ecohydrological model

2019 ◽  
Vol 23 (8) ◽  
pp. 3319-3334 ◽  
Author(s):  
Aaron Smith ◽  
Doerthe Tetzlaff ◽  
Hjalmar Laudon ◽  
Marco Maneta ◽  
Chris Soulsby
Keyword(s):  
Soil Moisture ◽  
Growing Season ◽  
Winter Period ◽  
Soil Frost ◽  
Freeze Thaw ◽  
Stream Discharge ◽  
Spatial Differences ◽  
Ecohydrological Model ◽  
Vegetation Water ◽  
Storage Flux

Abstract. Ecohydrological models are powerful tools to quantify the effects that independent fluxes may have on catchment storage dynamics. Here, we adapted the tracer-aided ecohydrological model, EcH2O-iso, for cold regions with the explicit conceptualization of dynamic soil freeze–thaw processes. We tested the model at the data-rich Krycklan site in northern Sweden with multi-criterion calibration using discharge, stream isotopes and soil moisture in three nested catchments. We utilized the model's incorporation of ecohydrological partitioning to evaluate the effect of soil frost on evaporation and transpiration water ages, and thereby the age of source waters. The simulation of stream discharge, isotopes, and soil moisture variability captured the seasonal dynamics at all three stream sites and both soil sites, with notable reductions in discharge and soil moisture during the winter months due to the development of the frost front. Stream isotope simulations reproduced the response to the isotopically depleted pulse of spring snowmelt. The soil frost dynamics adequately captured the spatial differences in the freezing front throughout the winter period, despite no direct calibration of soil frost to measured soil temperature. The simulated soil frost indicated a maximum freeze depth of 0.25 m below forest vegetation. Water ages of evaporation and transpiration reflect the influence of snowmelt inputs, with a high proclivity of old water (pre-winter storage) at the beginning of the growing season and a mix of snowmelt and precipitation (young water) toward the end of the summer. Soil frost had an early season influence of the transpiration water ages, with water pre-dating the snowpack mainly sustaining vegetation at the start of the growing season. Given the long-term expected change in the energy balance of northern climates, the approach presented provides a framework for quantifying the interactions of ecohydrological fluxes and waters stored in the soil and understanding how these may be impacted in future.

Effects of elevated O3 on soil respiration in a winter wheat - soybean rotation cropland

Soil Research ◽  
2012 ◽  
Vol 50 (6) ◽  
pp. 500 ◽  
Author(s):  
Shutao Chen ◽  
Yong Zhang ◽  
Haishan Chen ◽  
Zhenghua Hu
Keyword(s):  
Soil Respiration ◽  
Winter Wheat ◽  
Growing Season ◽  
Co2 Production ◽  
Soil Co2 ◽  
Production Rates ◽  
Elevated O3 ◽  
Respiration Rates ◽  
Nitrification And Denitrification ◽  
Soil Co2 Production

The increasing tropospheric ozone (O3) concentration has been reported to have negative effects on ecosystems. However, few investigations have focussed on the impacts of elevated O3 on soil respiration in cropland. This study aimed to examine the responses of soil respiration to elevated O3 with open-top chambers (OTCs) in a winter wheat (Triticum aestivum L.)–soybean (Glycine max (L.) Merr) rotation. The experiment was performed in the cropland near Nanjing city, south-east China. Seasonal changes in soil respiration rates, soil CO2 production rates, and nitrification and denitrification rates in ambient air (control) and elevated O3 (100 ppb) treatments were investigated in the 2009–10 winter wheat and 2010 soybean growing seasons. Seasonal mean soil respiration rates for the control and 100 ppb treatments were 3.16 and 2.66 μmol/m2.s, respectively, in the winter wheat growing season, and they were 3.59 and 2.51 μmol/m2.s, respectively, in the soybean growing season. Mean soil respiration rate in the control was ~29% higher than that in the 100 ppb treatment across the whole winter wheat–soybean rotation season. Elevated O3 significantly decreased soil respiration in both crops, with a larger effect observed in soybean. Mean soil CO2 production rates were reduced by ~42% in the 100 ppb O3 treatment compared with the control. No O3 effects were observed on soil nitrification and denitrification during the period monitored. A further analysis of covariance showed that soil respiration was significantly correlated with both soil temperature and moisture, and no interaction effects of O3 treatment and covariate (temperature or moisture) were observed.

A Multiscale Soil Moisture and Freeze–Thaw Monitoring Network on the Third Pole

2013 ◽  
Vol 94 (12) ◽  
pp. 1907-1916 ◽  
Author(s):  
Kun Yang ◽  
Jun Qin ◽  
Long Zhao ◽  
Yingying Chen ◽  
Wenjun Tang ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Monitoring Network ◽  
Freeze Thaw ◽  
The Third

Ecological responses of Stipa steppe in Inner Mongolia to experimentally increased temperature and precipitation. 3. Soil respiration

2018 ◽  
Vol 40 (2) ◽  
pp. 153 ◽  
Author(s):  
Xuexia Wang ◽  
Yali Chen ◽  
Yulong Yan ◽  
Zhiqiang Wan ◽  
Ran Chao ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Soil Respiration ◽  
Soil Temperature ◽  
Respiration Rate ◽  
Inner Mongolia ◽  
Growing Season ◽  
Climatic Warming ◽  
Soil Respiration Rate ◽  
Natural Rainfall ◽  
Temperature And Precipitation

The response of soil respiration to simulated climatic warming and increased precipitation was evaluated on the arid–semi-arid Stipa steppe of Inner Mongolia. Soil respiration rate had a single peak during the growing season, reaching a maximum in July under all treatments. Soil temperature, soil moisture and their interaction influenced the soil respiration rate. Relative to the control, warming alone reduced the soil respiration rate by 15.6 ± 7.0%, whereas increased precipitation alone increased the soil respiration rate by 52.6 ± 42.1%. The combination of warming and increased precipitation increased the soil respiration rate by 22.4 ± 11.2%. When temperature was increased, soil respiration rate was more sensitive to soil moisture than to soil temperature, although the reverse applied when precipitation was increased. Under the experimental precipitation (20% above natural rainfall) applied in the experiment, soil moisture was the primary factor limiting soil respiration, but soil temperature may become limiting under higher soil moisture levels.

Populations of endogonaceous fungi at two locations in central Iowa

1982 ◽  
Vol 60 (12) ◽  
pp. 2518-2529 ◽  
Author(s):  
Christopher Walker ◽  
Carl W. Mize ◽  
Harold S. McNabb Jr.
Keyword(s):  
Soil Moisture ◽  
Growing Season ◽  
Experimental Period ◽  
Spore Production ◽  
Moisture Level ◽  
Small Samples ◽  
Soil Moisture Level ◽  
Hybrid Poplars ◽  
Herbicide Treatment

Two different sites in central Iowa were planted with hybrid poplars and subsequently sampled over a growing season for spores of endogonaceous fungi. At one of the sites, the effects of plowing and herbicide treatment on spore numbers also were examined. Ten species of fungi in the genera Acaulospora, Gigaspora, and Glomus were recorded at the first site. The second location yielded 12 species from the same genera. In both sites, the distribution of spores was highly variable. The poplars rarely became endomycorrhizal and had no effect on spore populations during the experimental period. Changes in spore populations were correlated with soil-moisture level. Evidence was found for some depression of spore production caused by plowing and herbicide treatment. The conclusion was drawn that small samples with but few replicates may not adequately represent populations of endogonaceous spores.

The hydrosphere State (hydros) Satellite mission: an Earth system pathfinder for global mapping of soil moisture and land freeze/thaw

2004 ◽  
Vol 42 (10) ◽  
pp. 2184-2195 ◽  
Author(s):  
D. Entekhabi ◽  
E.G. Njoku ◽  
P. Houser ◽  
M. Spencer ◽  
T. Doiron ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Earth System ◽  
Satellite Mission ◽  
Freeze Thaw ◽  
Global Mapping

scholarly journals Different climate sensitivity for radial growth, but uniform for tree-ring stable isotopes along an aridity gradient in Polylepis tarapacana, the world’s highest elevation tree-species

2021 ◽  
Author(s):  
Milagros Rodriguez-Caton ◽  
Laia Andreu-Hayles ◽  
Mariano S Morales ◽  
Valérie Daux ◽  
Duncan A Christie ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Carbon Source ◽  
Tree Ring ◽  
Tree Growth ◽  
Carbon Sink ◽  
Growing Season ◽  
Wood Formation ◽  
Aridity Gradient ◽  
Leaf Level ◽  
Δ13c And Δ18o

Abstract Tree growth is generally considered to be temperature-limited at upper elevation treelines. Yet, climate factors controlling tree growth at semiarid treelines are poorly understood. We explored the influence of climate on stem growth and stable isotopes for Polyepis tarapacana, the world’s highest elevation tree-species found only in the South American Altiplano. We developed tree-ring width index (RWI), oxygen (δ18O) and carbon (δ13C) chronologies for the last 60 years at four P. tarapacana stands located above 4,400 meters in elevation, along a 500-km latitude-aridity gradient. Total annual precipitation decreased from 300 to 200 mm from the northern to the southern sites. We used RWI as a proxy of wood formation (carbon sink) and isotopic tree-ring signatures as proxies of leaf-level gas exchange processes (carbon source). We found distinct climatic conditions regulating carbon-sink processes along the gradient. Current-growing season temperature regulated RWI at wetter-northern sites, while prior-growing season precipitation determined RWI at arid-southern sites. This suggests that the relative importance of temperature to precipitation in regulating tree growth is driven by site-water availability. In contrast, warm and dry growing-seasons resulted in enriched tree-ring δ13C and δ18O at all study sites, suggesting that similar climate conditions control carbon-source processes. Site-level δ13C and δ18O chronologies were significantly and positively related at all sites, with the strongest relationships among the southern-drier stands. This indicates an overall regulation of intercellular carbon dioxide via stomatal conductance for the entire P. tarapacana network, with greater stomatal control when aridity increases. The manuscript also highlights a coupling and decoupling of physiological processes at leaf level versus wood formation depending on their respectively uniform and distinct sensitivity to climate. This study contributes to better understand and predict the response of high-elevation Polylepis woodlands to rapid climate changes and projected drying in the Altiplano.

Exploring the variation in ecosystem scale methane fluxes and its drivers within a boreal mire complex

2021 ◽  
Author(s):  
Koffi Dodji Noumonvi ◽  
Joshua L. Ratcliffe ◽  
Mats Öquist ◽  
Mats B. Nilsson ◽  
Matthias Peichl
Keyword(s):  
Eddy Covariance ◽  
Land Surface ◽  
Chemical Properties ◽  
Growing Season ◽  
Small Scale ◽  
Atmospheric Methane ◽  
Flux Footprint ◽  
Growing Season Length ◽  
Methane Fluxes ◽  
Northern Peatlands

<p>Northern peatlands cover a small fraction of the earth’s land surface, and yet they are one of the most important natural sources of atmospheric methane. With climate change causing rising temperatures, changes in water balance and increased growing season length, peatland contribution to atmospheric methane concentration is likely to increase, justifying the increased attention given to northern peatland methane dynamics. Northern peatlands often occur as heterogeneous complexes characterized by hydromorphologically distinct features from < 1 m² to tens of km², with differing physical, hydrological and chemical properties. The more commonly understood small-scale variation between hummocks, lawns and hollows has been well explored using chamber measurements. Single tower eddy covariance measurements, with a typical 95% flux footprint of < 0.5 km², have been used to assess the ecosystem scale methane exchange. However, how representative single tower flux measurements are of an entire mire complex is not well understood. To address this knowledge gap, the present study takes advantage of a network of four eddy covariance towers located less than 3 km apart at four mires within a typical boreal mire complex in northern Sweden. The variation of methane fluxes and its drivers between the four sites will be explored at different temporal scales, i.e. half-hourly, daily and at a growing-season scale.</p>

Hydrological implications of vegetation change in a subarctic, alpine catchment, Yukon Territory, Canada 

2021 ◽  
Author(s):  
Erin Nicholls ◽  
Gordon Drewitt ◽  
Sean Carey
Keyword(s):  
Soil Moisture ◽  
Interannual Variability ◽  
Sap Flow ◽  
Vegetation Change ◽  
Vegetation Type ◽  
Growing Season ◽  
White Spruce ◽  
Yukon Territory ◽  
Precipitation Regimes ◽  
Tall Shrub

<p>As a result of altitude and latitude amplified impacts of climate change, widespread alterations in vegetation composition, density and distribution are widely observed across the circumpolar north. The influence of this vegetation change on the timing and magnitude of hydrological fluxes is uncertain, and is confounded by changes driven by increased temperatures and altered precipitation (P) regimes. In northern alpine catchments, quantification of total evapotranspiration (ET) and evaporative partitioning across a range of elevation-based ecosystems is critical for predicting water yield under change, yet remains challenging due to coupled environmental and phenological controls on transpiration (T). In this work, we analyze 6 years of surface energy balance, ET, and sap flow data at three sites along an elevational gradient in a subarctic, alpine catchment near Whitehorse, Yukon Territory, Canada. These sites provide a space-for-time evaluation of vegetation shifts and include: 1) a low-elevation boreal white spruce forest (~20 m), 2) a mid-elevation subalpine taiga comprised of tall willow (Salix) and birch (Betula) shrubs (~1-3 m) and 3) a high-elevation subalpine taiga with shorter shrub cover (< 0.75 m) and moss, lichen, and bare rock. Specific objectives are to 1) evaluate interannual ET dynamics within and among sites under different precipitation regimes , and 2) assess the influence of vegetation type and structure, phenology, soil and meteorological controls on ET dynamics and partitioning.  Eddy covariance and sap flow sensors operated year-round at the forest and during the growing season at the mid-elevation site on both willow and birch shrubs for two years. Growing season ET decreased and interannual variability increased with elevation, with June to August ET totals of 250 (±3) mm at Forest, 192 (±9) mm at the tall shrub site, and 180 (± 26) mm at the short shrub site. Comparatively, AET:P ratios were the highest and most variable at the forest (2.4 ± 0.3) and similar at the tall and short shrub (1.2 ± 0.1).  At the forest, net radiation was the primary control on ET, and 55% was direct T from white spruce. At the shrub sites, monthly ET rates were similar except during the peak growing season when T at the tall shrub site comprised 89% of ET, resulting in greater total water loss. Soil moisture strongly influenced T at the forest, suggesting the potential for moisture stress, yet not at the shrub sites where there was no moisture limitation. Results indicate that elevation advances in treeline will increase overall ET and lower interannual variability; yet the large water deficit during summer implies a strong reliance on early spring snowmelt recharge to sustain soil moisture. Changes in shrub height and density will increase ET primarily during the mid-growing season. This work supports the assertion that predicted changes in vegetation type and structure will have a considerable impact on water partitioning in northern regions, and will also vary in a multifaceted way in response to changing temperature and P regimes.  </p>

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