Long-term effects of precipitation removal manipulations on soil carbon balance and exchange in a Danish heathland/grassland ecosystem

2020 ◽  
Author(s):  
Qiaoyan Li ◽  
Klaus Steenberg Larsen ◽  
Per Gundersen
Keyword(s):  
Soil Carbon ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Carbon Flux ◽  
Ecosystem Respiration ◽  
Net Ecosystem Exchange ◽  
Early Summer ◽  
Long Term Effects ◽  
Soil Substrate

<p>The influence of drought on terrestrial carbon cycling has received great attention because of the increasing frequency of extreme drought events in climate scenarios. In the CLIMAITE experiment, we have exposed plots to reduced precipitation since 2006. During the first years, precipitation was only reduced for 4-6 weeks during spring/early summer. In order to increase our focus on finding thresholds for functional and structural change in the ecosystem, the experiment was redesigned towards more extreme manipulations in June 2016 using a new gradient design continuously removing 40, 50, and 66% of ambient precipitation with permanent rainout shelters.</p><p>Rates of net ecosystem exchange (NEE), ecosystem respiration (R<sub>E</sub>) and soil respiration (Rs) are measured inside treatment plots using an LI-6400 connected to a custom-built 210L transparent chamber (for NEE) that can be darkened (for RE) as well as a 1L dark chamber (for Rs). In addition, environmental variables such as soil temperature, precipitation, soil water content and photosynthetically active radiation (PAR) are recorded continuously at the plot or site level. In addition, soil cores from the different treatments will be collected and analyzed for soil substrate (e.g. soil organic carbon) and incubated in the lab for analysis of Q<sub>10</sub>.  Using the observations from the field and the lab together we will develop a new multiple regression model to fit the CO<sub>2</sub> fluxes under severe precipitation removal treatments.</p><p> </p><p>To obtain more reliable and accurate estimates of the seasonal and annual responses of soil carbon flux exchange under precipitation change scenarios, the change in soil water content and temperature, the soil substrate availability as well as the variation of the frequency and timing of precipitation events are included in the carbon flux model. The fitting of models to the observational data will reveal if functional/structural thresholds for the carbon exchange have been exceeded in the ecosystem, thus providing novel experimental and modeling evidence for such thresholds.</p>

Soil water dynamics and growth of perennial pasture species for dryland salinity control

2000 ◽  
Vol 40 (1) ◽  
pp. 37 ◽  
Author(s):  
S. J. Lolicato
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Lotus Corniculatus ◽  
Growth Patterns ◽  
Water Dynamics ◽  
Seasonal Growth ◽  
Long Term Effects ◽  
Soil Water Dynamics

Fortnightly soil water content measurements to a depth of 2.1 m under 4 cocksfoot cultivars, 2 phalaris cultivars, 2 lucerne cultivars and 1 Lotus corniculatus cultivar were used to compare soil profile drying and to define seasonal patterns of plant water use of the species over a 3-year period, on a duplex soil. Cultivars were also selected, within species groups, for varying seasonal growth patterns to assess this influence on soil water dynamics and growth. Over the 3-year period, treatments with the highest and lowest measures of profile soil water content were used to derive and compare values of maximum plant extractable water. Plots were maintained for a further 3 years, after which soil water content measurements in autumn were used to assess long-term effects of the treatments. The effect of seasonal growth patterns within a species was negligible; however, there were significant differences between species. Twenty-one months after pasture establishment, lucerne alone had a drying effect at 2.0 m depth and subsequently it consistently showed profiles with the lowest soil water content. Maximum plant extractable water was greatest for lucerne (230 mm), followed by phalaris (210 mm), Lotus corniculatus (200 mm) and cocksfoot (170 mm). Profiles with the lowest soil water content were associated with greater herbage growth and greater depths of water extraction. The soil water deficits developed by the treatments in autumn of the fourth year were similar to those measured in autumn of the seventh year, implying that a species-dependant equilibrium had been reached. Long-term rainfall data is used to calculate the probabilities of recharge occurring when rainfall exceeds maximum potential deficits for the different pasture species.

Long-term effects of revegetation on soil water content of sand dunes in arid region of Northern China

2004 ◽  
Vol 57 (1) ◽  
pp. 1-16 ◽  
Author(s):  
Xin Rong Li ◽  
Feng Yun Ma ◽  
Hong Lang Xiao ◽  
Xin Ping Wang ◽  
Ke Chung Kim
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Arid Region ◽  
Sand Dunes ◽  
Northern China ◽  
Long Term Effects

scholarly journals Effects of soil water content on carbon sink strength in an alpine swamp meadow of the northeastern Qinghai-Tibet Plateau

2021 ◽  
Author(s):  
Junqi Wei ◽  
Xiaoyan Li ◽  
Lei Liu ◽  
Torben Røjle Christensen ◽  
Zhiyun Jiang ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Climate Warming ◽  
Ecosystem Respiration ◽  
Saturated Soil ◽  
Tibet Plateau ◽  
Sink Strength ◽  
Qinghai Tibet Plateau

Abstract. Predicted intensified climate warming will likely alter the ecosystem net carbon (C) uptake of the Qinghai-Tibet Plateau (QTP). Variations in C sink/source responses to climate warming have been linked to water availability; however, the mechanisms by which net C uptake responds to soil water content in water-saturated swamp meadow ecosystems remain unclear. To explore how soil moisture and other environmental drivers modulate net C uptake in the QTP, field measurements were conducted using the eddy covariance technique in 2014, 2015, 2017, and 2018. The alpine swamp meadow presented in this study was a consistent and strong C sink of CO2 (−168.0 ± −62.5 gC m−2 y−1, average ± standard deviation) across the entire 4-year study period. A random forest machine-learning analysis suggests that the diurnal, seasonal, and annual variations of net ecosystem exchange (NEE) and gross primary productivity (GPP) were controlled by temperature and solar radiation. Ecosystem respiration (Re), however, was found mainly regulated by the variability of soil water content (SWC) at different temporal aggregations followed by temperature, the second contributing driver. We further explored how Re is controlled by nearly saturated soil moisture and temperature comparing two different periods featuring identical temperatures and significantly differences on SWC and vice versa. Our data suggest that, despite the relatively abundant water supply, periods with a substantial decrease of SWC or increase of temperature produced higher Re lowering the C sink strength. Our results reveal that nearly saturated soil conditions during the warm seasons can help to maintain lower ecosystem respiration rates and thus enhance the overall C sequestration capacity in this alpine swamp meadow. We argue that changes in soil hydrological conditions induced by a warming climate near permafrost (or seasonal frozen layers) may affect the C sink magnitude of wet and cold ecosystems through changes in soil hydrology and the subsequent effect on respiration losses.

scholarly journals Hysteresis response of daytime net ecosystem exchange during drought

2010 ◽  
Vol 7 (3) ◽  
pp. 1159-1170 ◽  
Author(s):  
N. Pingintha ◽  
M. Y. Leclerc ◽  
J. P. Beasley ◽  
D. Durden ◽  
G. Zhang ◽  
...  
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Stomatal Closure ◽  
Net Ecosystem Exchange ◽  
Co2 Exchange ◽  
Dominant Factor ◽  
Agricultural Ecosystem ◽  
Eddy Covariance Method ◽  
Southeastern Us

Abstract. Continuous measurements of net ecosystem CO2 exchange (NEE) using the eddy-covariance method were made over an agricultural ecosystem in the southeastern US. During optimum environmental conditions, photosynthetically active radiation (PAR) was the primary driver controlling daytime NEE, accounting for as much as 67 to 89% of the variation in NEE. However, soil water content became the dominant factor limiting the NEE-PAR response during the peak growth stage. NEE was significantly depressed when high PAR values coincided with very low soil water content. The presence of a counter-clockwise hysteresis of daytime NEE with PAR was observed during periods of water stress. This is a result of the stomatal closure control of photosynthesis at high vapor pressure deficit and enhanced respiration at high temperature. This result is significant since this hysteresis effect limits the range of applicability of the Michaelis-Menten equation and other related expressions in the determination of daytime NEE as a function of PAR. The systematic presence of hysteresis in the response of NEE to PAR suggests that the gap-filling technique based on a non-linear regression approach should take into account the presence of water-limited field conditions. Including this step is therefore likely to improve current evaluation of ecosystem response to increased precipitation variability arising from climatic changes.

scholarly journals Grassland Management Influences the Response of Soil Respiration to Drought

Agronomy ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 124 ◽  
Author(s):  
Gabriel Moinet ◽  
Andrew Midwood ◽  
John Hunt ◽  
Cornelia Rumpel ◽  
Peter Millard ◽  
...  
Keyword(s):  
Soil Respiration ◽  
Soil Carbon ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Management Practices ◽  
Grassland Management ◽  
Mitigate Climate Change ◽  
Mowing Regime ◽  
The Impact

Increasing soil carbon stocks in agricultural grasslands has a strong potential to mitigate climate change. However, large uncertainties around the drivers of soil respiration hinder our ability to identify management practices that enhance soil carbon sequestration. In a context where more intense and prolonged droughts are predicted in many regions, it is critical to understand how different management practices will temper drought-induced carbon losses through soil respiration. In this study, we compared the impact of changing soil volumetric water content during a drought on soil respiration in permanent grasslands managed either as grazed by dairy cows or as a mowing regime. Across treatments, root biomass explained 43% of the variability in soil respiration (p < 0.0001). Moreover, analysis of the isotopic composition of CO2 emitted from the soil, roots, and root-free soil suggested that the autotrophic component largely dominated soil respiration. Soil respiration was positively correlated with soil water content (p = 0.03) only for the grazed treatment. Our results suggest that the effect of soil water content on soil respiration was attributable mainly to an effect on root and rhizosphere activity in the grazed treatment. We conclude that farm management practices can alter the relationship between soil respiration and soil water content.

scholarly journals Greenhouse gas balance of open peatlands is globally governed by soil water content and archaeal abundance

2021 ◽  
Author(s):  
Sandeep Thayamkottu ◽  
Jaan Pärn ◽  
Mohammad Bahram ◽  
Mikk Espenberg ◽  
Leho Tedersoo ◽  
...  
Keyword(s):  
Greenhouse Gas ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Ghg Emissions ◽  
Net Ecosystem Exchange ◽  
Greenhouse Gas Balance ◽  
Imaging Spectrometer ◽  
Global Database ◽  
Moderate Resolution

&lt;p&gt;There is a general consensus that peatlands are the source of about 10% of the global CO&lt;sub&gt;2&lt;/sub&gt;, CH&lt;sub&gt;4&lt;/sub&gt; and N&lt;sub&gt;2&lt;/sub&gt;O greenhouse gas (GHG) emissions. Yet, our knowledge about underlying processes and environmental factors that regulate the GHG are limited. Here, we found that the GHG balance of CO&lt;sub&gt;2&lt;/sub&gt;, CH&lt;sub&gt;4&lt;/sub&gt; and N&lt;sub&gt;2&lt;/sub&gt;O in 48 open peatland sites on five continents can be predicted by a model that incorporates soil water content (SWC) and archaeal abundance. We used our global database (2011&amp;#8211;2019) on peat characteristics and field-measured soil respiration (ER), CH&lt;sub&gt;4&lt;/sub&gt; and N&lt;sub&gt;2&lt;/sub&gt;O emissions. Furthermore, we used the gross primary productivity (GPP) dataset by Running, Mu &amp; Zhao (2015) on the basis of satellite data from the Moderate Resolution Imaging Spectrometer (MODIS) sensors alongside the ER to derive net ecosystem exchange (NEE) of carbon. The GHG balance follows SWC along a bell-shaped curve and increases with archaeal abundance and decomposition rate of peat-forming plant species. Thus, the net GHG emission peaks at intermediate SWC. These factors combined explains 61.9% (adjusted R&lt;sup&gt;2&lt;/sup&gt; = 0.587) of GHG balance and most of this variance is made up by the NEE of carbon (adjusted R&lt;sup&gt;2&lt;/sup&gt; = 0.97).&lt;/p&gt;

scholarly journals Response of ecosystem respiration to experimental warming and clipping in Tibetan alpine meadow at three elevations

2013 ◽  
Vol 10 (8) ◽  
pp. 13015-13047 ◽  
Author(s):  
G. Fu ◽  
Y.-J. Zhang ◽  
X.-Z. Zhang ◽  
P.-L. Shi ◽  
Y.-T. Zhou ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Tibetan Plateau ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Water Availability ◽  
Alpine Meadow ◽  
Ecosystem Respiration ◽  
The Tibetan Plateau ◽  
Experimental Warming

Abstract. This study aims to understand the response of ecosystem respiration (Reco) to warming and clipping in the alpine meadow of Tibet. A field warming experiment using open top chambers was conducted in three alpine meadow sites at elevation 4313 m, 4513 m and 4693 m on the Tibetan Plateau since July 2008. Clipping was conducted three times a year since 2009. Reco was measured from June to September in 2010–2012. For most cases, the seasonal variation of Reco was mainly affected by soil water content rather than soil and air temperature, especially under warmer environment. Experimental warming tended to decrease seasonal average Reco by 21.6% and 10.9% at elevation 4313 m and 4513 m, respectively, but significantly increased seasonal average Reco by 11.3% at elevation 4693 m. The different responses of Reco to experimental warming could be mainly dependent on temperature and water availability condition. Clipping decreased seasonal average Reco by 6.9%, 36.9% and 31.6% at elevation 4313 m, 4513 m and 4693 m. The consistent declines caused by clipping may be mainly attributed to clipping-induced decline in aboveground biomass. Our findings suggested that the response of Reco to warming differed among the alpine meadow and was regulated by soil water content on the Tibetan Plateau.

SOIL WATER CONTENT AFFECTS THE AVAILABILITY OF PHOSPHATE

1985 ◽  
pp. 185-189
Author(s):  
M.C.H.Mouat Pieter Nes
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Soil Solution ◽  
Equivalent Reduction

Reduction in water content of a soil increased the concentration of ammonium and nitrate in solution, but had no effect on the concentration of phosphate. The corresponding reduction in the quantity of phosphate in solution caused an equivalent reduction in the response of ryegrass to applied phosphate. Keywords: soil solution, soil water content, phosphate, ryegrass, nutrition.

Effect of inter-row cultivation on soil carbon dioxide emission in a peach plantation

2010 ◽  
Vol 59 (1) ◽  
pp. 157-164 ◽  
Author(s):  
E. Tóth ◽  
Cs. Farkas
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Carbon Dioxide Emission ◽  
Nutrient Content ◽  
Soil Disturbance ◽  
Biological Properties ◽  
Soil Tillage ◽  
Favourable Effect ◽  
Volumetric Soil Water Content

Soil biological properties and CO2emission were compared in undisturbed grass and regularly disked rows of a peach plantation. Higher nutrient content and biological activity were found in the undisturbed, grass-covered rows. Significantly higher CO2fluxes were measured in this treatment at almost all the measurement times, in all the soil water content ranges, except the one in which the volumetric soil water content was higher than 45%. The obtained results indicated that in addition to the favourable effect of soil tillage on soil aeration, regular soil disturbance reduces soil microbial activity and soil CO2emission.

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