Empirical modelling of plant and soil carbon flux drivers under field conditions

2020 ◽  
Author(s):  
Chris McCloskey ◽  
Guy Kirk ◽  
Wilfred Otten ◽  
Eric Paterson
Keyword(s):  
Soil Moisture ◽  
Soil Temperature ◽  
Soil Carbon ◽  
Field Conditions ◽  
Gas Flux ◽  
Soil C ◽  
C Dynamics ◽  
Plant Respiration ◽  
Soil Temperature And Moisture

<p>Our understanding of soil carbon (C) dynamics is limited; field measurements necessarily conflate fluxes from plant and soil sources and we therefore lack long-term field-scale data on soil C fluxes to use to test and improve soil C models. Furthermore, it is often unclear whether findings from lab-based studies, such as the presence of rhizosphere priming, apply to soil systems in the field. It is particularly important that we are able to understand the roles of soil temperature and moisture, and plant C inputs, as drivers of soil C dynamics in order to predict how changing climate and plant productivity may affect the net C balance of soils. We have developed a field laboratory with which to generate much-needed long-term C flux data under field conditions, giving near-continuous measurements of plant and soil C fluxes and their drivers.</p><p>The laboratory contains 24 0.8-m diameter, 1-m deep, naturally-structured soil monoliths of two contrasting C3 soils (a clay-loam and a sandy soil) in lysimeters. These are sown with a C4 grass (<em>Bouteloua dactyloides</em>), providing a large difference in C isotope signature between C4 plant respiration and C3-origin soil organic matter (SOM) decomposition, which enables clear partitioning of the net C flux. This species is used as a pasture grass in the United States, and regular trimming through the growing season simulates low-intensity grazing. The soil monoliths are fitted with gas flux chambers and connected via an automated sampling loop to a cavity ring-down spectrometer, which measures the concentration and <sup>12</sup>C:<sup>13</sup>C isotopic ratio of CO<sub>2</sub> during flux chamber closure. Depth-resolved measurements of soil temperature and moisture in each monolith are made near-continuously, along with measurements of incoming solar radiation, rainfall, and air temperature a the field site. The gas flux chambers are fitted with removable reflective backout covers allowing flux measurements both incorporating, and in the absence of, photosynthesis.</p><p>We have collected net ecosystem respiration data, measurements of photosynthesis, and recorded potential drivers of respiration over two growing seasons through 2018 and 2019. Through partitioning fluxes between plant respiration and SOM mineralisation we have revealed clear diurnal trends in both plant and soil C fluxes, along with overarching seasonal trends which modify both the magnitude of fluxes and their diurnal patterns. Rates of photosynthesis have been interpolated between measurement periods using machine learning to generate a predictive model, which has allowed us to investigate the effect of plant productivity on SOM mineralisation and assess whether rhizosphere priming can be detected in our system. Through regression analyses and linear mixed effects modelling we have evaluated the roles of soil temperature, soil moisture, and soil N content as drivers of variation in plant and soil respiration in our two contrasting soils. This has shown soil temperature to be the most important control on SOM mineralisation, with soil moisture content playing only a minor role. We have also used our empirical models to suggest how the carbon balance of pasture and grassland soils may respond to warming temperatures.</p>

 Implementation of mycorrhizal mechanism into a soil carbon model improves the prediction of long-term processes of plant litter decomposition

2021 ◽  
Author(s):  
Weilin Huang ◽  
Peter van Bodegom ◽  
Toni Viskari ◽  
Jari Liski ◽  
Nadejda Soudzilovskaia
Keyword(s):  
Soil Carbon ◽  
Litter Decomposition ◽  
Arbuscular Mycorrhizae ◽  
Plant Litter ◽  
Climate Impacts ◽  
Microbial Interactions ◽  
Soil C ◽  
Plant Litter Decomposition ◽  
C Dynamics

<p>Mycorrhizae, a plant-fungal symbiosis, is an important contributor to below ground-microbial interactions, and hypothesized to play a paramount role in soil carbon (C) sequestration. Ectomycorrhizae (EM) and arbuscular mycorrhizae (AM) are the two dominant forms of mycorrhizae featured by nearly all Earth plant species. However, the difference in the nature of their contributions to the processes of plant litter decomposition is still understood poorly. Current soil carbon models treat mycorrhizal impacts on the processes of soil carbon transformation as a black box. This retards scientific progress in mechanistic understanding of soil C dynamics.</p><p>We examined four alternative conceptualizations of the mycorrhizal impact on plant litter C transformations, by integrating AM and EM fungal impacts on litter C pools of different recalcitrance into the soil carbon model Yasso15. The best performing concept featured differential impacts of EM and AM on a combined pool of labile C, being quantitatively distinct from impacts of AM and EM on a pool of recalcitrant C.</p><p>Analysis of time dynamics of mycorrhizal impacts on soil C transformations demonstrated that these impacts are larger at the long-term (>2.5yrs) litter decomposition processes, compared to the short-term processes. We detected that arbuscular mycorrhizae controls shorter term decomposition of labile carbon compounds, while ectomycorrhizae dominate the long term decomposition processes of highly recalcitrant carbon elements. Overall, adding our mycorrhizal module into the Yasso model greatly improved the accuracy of the temporal dynamics of carbon sequestration.</p><p>A sensitivity analysis of litter decomposition to climate and mycorrhizal factors indicated that ignoring the mycorrhizal impact on the decomposition leads to an overestimation of climate impacts. This suggests that being co-linear with climate impacts, mycorrhizal impacts could be partly hidden within climate factors in soil carbon models, reducing the capability of such models to mechanistically predict impacts of climate vs vegetation change on soil carbon dynamics.</p><p>Our results provide a benchmark to mechanistic modelling of microbial impacts on soil C dynamics. This work opens new pathways to examining the impacts of land-use change and climate change on plant-microbial interactions and their role in soil C dynamics, allowing the integration of microbial processes into global vegetation models used for policy decisions on terrestrial carbon monitoring.</p>

scholarly journals Inclusion of biochar in a C-dynamics model based on observations from a 8 years field experiment

2021 ◽  
Author(s):  
Roberta Pulcher ◽  
Enrico Balugani ◽  
Maurizio Ventura ◽  
Diego Marazza
Keyword(s):  
Field Experiment ◽  
Degradation Rate ◽  
C Sequestration ◽  
Field Conditions ◽  
Soil C ◽  
Short Rotation ◽  
C Dynamics ◽  
Rothc Model ◽  
Using Data

Abstract. Biochar production and application as soil amendment is a promising carbon (C) negative technology to increase soil C sequestration and mitigate climate change. However, there is a lack of knowledge about biochar degradation rate in soil and its effects on native soil organic carbon (SOC), mainly due to the absence of long term experiments performed in field conditions. The aim of this work was to investigate the long term degradation rate of biochar in a field experiment of 8 years in a poplar short rotation coppice plantation in Piedmont (Italy), and to modify the RothC model to assess and predict how biochar influences soil C dynamics. The RothC model was modified by including two biochar pools, labile (4 % of the total biochar mass) and recalcitrant (96 %), and the priming effect of biochar on SOC. The model was calibrated and validated using data from the field experiment. The results confirm that biochar degradation can be faster in field conditions in comparison to laboratory experiments; nevertheless, it can contribute to substantially increase the soil C stock in the long-term. Moreover, this study shows that the modified RothC model was able to simulate the dynamics of biochar and SOC degradation in soils in field conditions in the long term, at least in the specific conditions examined.

Effects of Soil Temperature and Drought on Root–Soil Respiration in Apple under Field Conditions

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 453a-453
Author(s):  
Liqin Wang ◽  
David M. Eissenstat ◽  
Dora E. Flores-Alva
Keyword(s):  
Soil Moisture ◽  
Soil Respiration ◽  
Soil Temperature ◽  
Root Respiration ◽  
Hot Water ◽  
Field Conditions ◽  
Drought Treatment ◽  
Dry Soil ◽  
Heated Soil ◽  
Soil Temperature And Moisture

Root respiration is very important to root efficiency, root lifespan, and carbon cycling in plant ecosystems. Yet, the effects of soil temperature and moisture on root respiration are poorly understood, especially under field conditions. In this study, we manipulated soil temperature and moisture by six bearing `Red Chief' Delicious/M26 trees near State College, Pa. Soil temperature was elevated 5 °C at 5-cm depth using circulating hot water and stainless steel grids. Soil temperature was monitored using thermocouples and a data logger, and soil moisture was monitored using TDR. Root–soil respiration was determined by static trapping at the soil surface. Heating was conducted from 8 May to 28 Oct. Drought was initiated on 21 Aug. and lasted 2 months. Root–soil respiration was lowest in spring and increased from June to late August. After September, respiration decreased until the experiment ended in November. Root-soil respiration was not correlated with root length density. Heating enhanced root–soil respiration about 15% to 20% in spring (May) and 10% in summer (June–August). After the drought treatment began, heating increased root-soil respiration about 42% in wet soil, but did not influence respiration in dry soil. Heating accentuated the effect of the drought treatment on soil moisture. After 2 months of no irrigation and no rain, soil moisture was reduced 5% in unheated soil and 10% in heated soil. Drought slowed root–soil respiration 17% in unheated soil and 36% in heated soil, mainly because heating increased respiration in wet soil, but compared to the unheated treatment, had no effect in dry soil.

scholarly journals Seasonal variation of gross nitrification rates at three differently treated long-term fertilisations sites

2009 ◽  
Vol 6 (1) ◽  
pp. 1565-1598 ◽  
Author(s):  
C. F. Stange ◽  
H.-U. Neue
Keyword(s):  
Soil Moisture ◽  
Soil Temperature ◽  
Temporal Variability ◽  
Dry Mass ◽  
Control Site ◽  
Field Conditions ◽  
Gross Nitrification ◽  
Mineral Fertiliser ◽  
And Control

Abstract. The formation of nitrate (nitrification) in soils is an important process that influences the form of N available for plant uptake and the potential off-site N losses. Gross nitrification is one of the main sources of nitrous oxide (N2O) and nitric oxide (NO) from soils. A field experiment was designed to verify the idea that gross nitrification rates in soils can be readily predicted by a model approach where seasonal variability is described only by soil moisture and soil temperature and the magnitude of gross nitrification is controlled by the soil organic matter (SOM). Gross nitrification rates were measured by a Barometric Process Separation (BaPS), first described by Ingwersen et al. (1999). The BaPS measurements were validated with the commonly used 15N pool dilution technique measurements at six times. In general, the rates determined from both measurement approaches were in the same order of magnitude and showed a good correlation. The effects of three different fertilisations (mineral fertiliser, manure and the control) over more than 100 years on gross nitrification rates were investigated. During 2004 soil probes from the long-term "static fertilisation experiment" at Bad Lauchstädt were sampled weekly and were measured in the laboratory under field conditions and subsequently under standardised conditions (16°C soil temperature and −30 kPa matrix potential) with the Barometric Process Separation system (BaPS). Gross nitrification rates determined by the BaPS-method under field conditions showed a high temporal variability and ranged from 5 to 77 μg N h−1 kg−1 dry mass, 2 to 74 μg N h−1 kg−1 dry mass and 0 to 49 μg N h−1 kg−1 dry mass with respect to manure, mineral fertiliser and control. The annual average was 0.32, 0.26 and 0.18 g N a−1 kg−1 dry mass for the manure site, mineral fertiliser site and control site, respectively. On all sites gross nitrification revealed a strong seasonal dynamic. Three different methods (a temperature and soil moisture dependency model from Recous et al., 1998, a multiple linear regression and the method proposed in this paper) were applied for reproducing the measured results. On the manure site 78% to 80%, on the mineral fertiliser site 66% to 72% and on the control site 39% to 56% of the observed variations could be explained by the tested models. Gross nitrification rates determined under standardised conditions did not show any seasonal trends but did also however reveal high temporal variability.

scholarly journals Decreased summer drought affects plant productivity and soil carbon dynamics in Mediterranean woodland

2011 ◽  
Vol 8 (3) ◽  
pp. 5955-5990 ◽  
Author(s):  
M. F. Cotrufo ◽  
G. Alberti ◽  
I. Inglima ◽  
H. Marjanović ◽  
D. LeCain ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Primary Production ◽  
Soil C ◽  
Precipitation Patterns ◽  
C Dynamics ◽  
Precipitation Regimes ◽  
C Stocks ◽  
C Input ◽  
Mediterranean Woodland

Abstract. Precipitation patterns are expected to change in the Mediterranean region within the next decades, with projected decreases in total rainfall and increases in extreme events. We manipulated precipitation patterns in a Mediterranean woodland, dominated by Arbutus unedo L., to study the effects of changing precipitation regimes on above-ground net primary production (ANPP) and soil C dynamics, specifically plant-derived C input to soil and soil respiration (SR). Experimental plots were exposed to either a 20 % reduction of throughfall or to water addition targeted at maintaining soil water content above a minimum of 10 % v/v. Treatments were compared to control plots which received ambient precipitation. The throughfall manipulation experiment started in 2004 and we report data up to the 2009 growing season. Enhanced soil moisture during summer months highly stimulated annual stem primary production, litter fall, SR and net annual plant-derived C input to soil which on average increased by 130 %, 26 %, 50 % and 220 %, respectively, as compared to control. In contrast, the 20 % reduction in throughfall (equivalent to 10 % reduction of precipitation) did not significantly change soil moisture at the site, and therefore did not significantly affect ANPP or SR. We conclude that minor changes (around 10 % reduction) in precipitation amount are not likely to significantly affect ANPP or soil C dynamics in Mediterranean woodland. However, if summer rain increases, C cycling will significantly accelerate but soil C stocks are not likely to be changed in the short-term. More studies involving modelling of long term C dynamics are needed to predict if the estimated increases in soil C input under wet conditions is going to be sustained and if labile C is being substituted to stable C, with a negative effect on long term soil C stocks.

scholarly journals Decreased summer drought affects plant productivity and soil carbon dynamics in a Mediterranean woodland

2011 ◽  
Vol 8 (9) ◽  
pp. 2729-2739 ◽  
Author(s):  
M. F. Cotrufo ◽  
G. Alberti ◽  
I. Inglima ◽  
H. Marjanović ◽  
D. LeCain ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Primary Production ◽  
Soil C ◽  
Precipitation Patterns ◽  
C Dynamics ◽  
Precipitation Regimes ◽  
C Stocks ◽  
C Input ◽  
Mediterranean Woodland

Abstract. Precipitation patterns are expected to change in the Mediterranean region within the next decades, with projected decreases in total rainfall and increases in extreme events. We manipulated precipitation patterns in a Mediterranean woodland, dominated by Arbutus unedo L., to study the effects of changing precipitation regimes on above-ground net primary production (ANPP) and soil C dynamics, specifically plant-derived C input to soil and soil respiration (SR). Experimental plots were exposed to either a 20 % reduction of throughfall or to water addition targeted at maintaining soil water content above a minimum of 10 % v/v. Treatments were compared to control plots which received ambient precipitation. Enhanced soil moisture during summer months highly stimulated annual stem primary production, litter fall, SR and net annual plant-derived C input to soil which on average increased by 130 %, 26 %, 58 % and 220 %, respectively, as compared to the control. In contrast, the 20 % reduction in throughfall (equivalent to 10 % reduction in precipitation) did not significantly change soil moisture at the site, and therefore did not significantly affect ANPP or SR. We conclude that minor changes (around 10 % reduction) in precipitation amount are not likely to significantly affect ANPP or soil C dynamics in Mediterranean woodlands. However, if summer rain increases, C cycling will significantly accelerate but soil C stocks are not likely to be changed in the short-term. More studies involving modelling of long-term C dynamics are needed to predict if the estimated increases in soil C input under wet conditions is going to be sustained and if labile C is being substituted to stable C, with a negative effect on long-term soil C stocks.

scholarly journals Insights Into Fire-based Soil Temperature and Moisture Changes From a Long-term Data Set in Alaska

2021 ◽  
Author(s):  
Kristen Manies ◽  
Jennifer Harden ◽  
William Cable ◽  
Jamie Hollingsworth
Keyword(s):  
Soil Temperature ◽  
Data Set ◽  
Term Data ◽  
Soil Temperature And Moisture

scholarly journals Soil carbon release responses to long-term versus short-term climatic warming in an arid ecosystem

2019 ◽  
Author(s):  
Hongying Yu ◽  
Zhenzhu Xu ◽  
Guangsheng Zhou ◽  
Yao Shou
Keyword(s):  
Soil Temperature ◽  
Soil Carbon ◽  
Field Experiments ◽  
Arid Ecosystems ◽  
Organic Carbon Content ◽  
Climatic Warming ◽  
Short Term ◽  
Desert Steppes ◽  
Carbon Release

Abstract. Climate change severely impacts grassland carbon cycling, especially in arid ecosystems, such as desert steppes. However, little is known about the responses of soil respiration (Rs) to different warming magnitudes and watering pulses in situ in desert steppes. To examine their effects on Rs, we conducted long-term moderate warming, short-term acute warming and watering field experiments in a desert grassland of Northern China. While experimental warming significantly reduced Rs by 32.5 % and 40.8 % under long-term and moderate and short-term and acute warming regimes, respectively, watering pulses stimulated it substantially. Warming did not change the exponential relationship between Rs and soil temperature, whereas the relationship of Rs with soil water content (SWC) was well fitted to the Gompertz function. The soil features were not significantly affected by either long-term or short-term warming regimes, respectively; however, soil organic carbon content tended to decrease with long-term climatic warming. This indicates that soil carbon release responses strongly depend on the duration and magnitude of climatic warming, which may be driven by SWC and soil temperature. The results of this study highlight the great dependence of soil carbon emission on warming regimes of different durations and the important role of precipitation pulse during growing season in assessing the terrestrial ecosystem carbon balance and cycle.

Influence of pesticides, soil temperature and moisture on entomopathogenic nematodes from southern Benin and control of underground termite nest populations

Nematology ◽  
2015 ◽  
Vol 17 (9) ◽  
pp. 1057-1069 ◽  
Author(s):  
Hugues Baimey ◽  
Lionel Zadji ◽  
Leonard Afouda ◽  
Maurice Moens ◽  
Wilfrida Decraemer
Keyword(s):  
Soil Moisture ◽  
Soil Temperature ◽  
Entomopathogenic Nematodes ◽  
Galleria Mellonella ◽  
Macrotermes Bellicosus ◽  
And Control ◽  
The Impact ◽  
Termite Nest ◽  
Southern Benin ◽  
Soil Temperature And Moisture

The influence of three pesticides on the viability and infectivity of four Beninese isolates of entomopathogenic nematodes (EPN), Heterorhabditis indica Ayogbe1, H. sonorensis Azohoue2, H. sonorensis Ze3, and Steinernema sp. Bembereke, was determined. The impact of both soil temperature and soil moisture on the virulence of these EPN to Trinervitermes occidentalis was investigated in laboratory assays. The effect of EPN-infected Galleria mellonella larvae on underground populations of Macrotermes bellicosus was also examined. All tested Heterorhabditis species were more tolerant to glyphosate and fipronil than the Steinernema species. Heterorhabditis sonorensis Azohoue2, showed the best results with 63.2% termite mortality at a soil temperature of 35°C. The increase of soil moisture to 20% (w/w) did not negatively influence the virulence of tested EPN. The underground populations of 71% or 60% treated nests were controlled by H. sonorensis Azohoue2- or H. indica Ayogbe1-infected G. mellonella larvae, respectively.

Herbage biomass and its relationship to soil carbon under long-term grazing in northern temperate grasslands

2019 ◽  
Vol 99 (6) ◽  
pp. 905-916
Author(s):  
E.W. Bork ◽  
M.P. Lyseng ◽  
D.B. Hewins ◽  
C.N. Carlyle ◽  
S.X. Chang ◽  
...  
Keyword(s):  
Soil Carbon ◽  
Root Biomass ◽  
Mineral Soil ◽  
Belowground Biomass ◽  
Cattle Grazing ◽  
Shoot Biomass ◽  
Positive Contribution ◽  
Temperate Grasslands ◽  
Soil C

While northern temperate grasslands are important for supporting beef production, it remains unclear how grassland above- and belowground biomass responds to long-term cattle grazing. Here, we use a comprehensive dataset from 73 grasslands distributed across a broad agro-climatic gradient to quantify grassland shoot, litter, and shallow (top 30 cm) root biomass in areas with and without grazing. Additionally, we relate biomass to soil carbon (C) concentrations. Forb biomass was greater (p < 0.05) in grazed areas, particularly those receiving more rainfall. In contrast, grass and total aboveground herbage biomass did not differ with grazing (total: 2320 kg ha−1 for grazed vs. 2210 kg ha−1 for non-grazed; p > 0.05). Forb crude protein concentrations were lower (p < 0.05) in grazed communities compared with those that were non-grazed. Grasslands subjected to grazing had 56% less litter mass. Root biomass down to 30 cm remained similar between areas with (9090 kg ha−1) and without (7130 kg ha−1) grazing (p > 0.05). Surface mineral soil C concentrations were positively related to peak grassland biomass, particularly total (above + belowground) biomass, and with increasing forb biomass in grazed areas. Finally, total aboveground shoot biomass and soil C concentrations in the top 15 cm of soil were both positively related to the proportion of introduced plant diversity in grazed and non-grazed grasslands. Overall, cattle grazing at moderate stocking rates had minimal impact on peak grassland biomass, including above- and belowground, and a positive contribution exists from introduced plant species to maintaining herbage productivity and soil C.

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