scholarly journals Modeling the effects of litter stoichiometry and soil mineral N availability on soil organic matter formation

2018 ◽  
Author(s):  
Haicheng Zhang ◽  
Daniel S. Goll ◽  
Stefano Manzoni ◽  
Philippe Ciais ◽  
Bertrand Guenet ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Litter Quality ◽  
Plant Litter ◽  
Climate Mitigation ◽  
N Availability ◽  
Mineral N ◽  
Microbial Decomposition ◽  
Soil C ◽  
C Cycle

Abstract. Microbial decomposition of plant litter is a crucial process for the land carbon (C) cycle, as it directly controls the partitioning of litter-C between CO2 released to the atmosphere versus the formation of new soil organic matter (SOM). Land surface models used to study the C cycle rarely considered flexibility in the decomposer C use efficiency (CUEd) defined by the fraction of decomposed litter-C that is retained as SOM (as opposed to be respired). In this study, we adapted a conceptual formulation of CUEd based on assumption that litter decomposers optimally adjust their CUEd as a function of litter substrate C to nitrogen (N) stoichiometry to maximize their growth rates. This formulation was incorporated into the widely used CENTURY soil biogeochemical model and evaluated based on data from laboratory litter incubation experiments. Results indicated that the CENTURY model with new CUEd formulation was able to reproduce differences in respiration rate of litter with contrasting C:N ratios and under different levels of mineral N availability, whereas the default model with fixed CUEd could not. Using the model with adapted CUEd formulation, we also illustrated that litter quality affected the long-term SOM formation crucially. Litter with a small C:N ratio tended to form a larger SOM pool than litter with larger C:N ratios, as it could be more efficiently incorporated into SOM by microorganisms. This study provided a simple but effective formulation to quantify the effect of varying litter quality (N content) on SOM formation across temporal scales. Optimality theory appears to be suitable to predict complex processes of litter decomposition into soil C, and to quantify how plant residues and manure can be harnessed to improve soil C sequestration for climate mitigation.

scholarly journals Modeling the effects of litter stoichiometry and soil mineral N availability on soil organic matter formation using CENTURY-CUE (v1.0)

2018 ◽  
Vol 11 (12) ◽  
pp. 4779-4796 ◽  
Author(s):  
Haicheng Zhang ◽  
Daniel S. Goll ◽  
Stefano Manzoni ◽  
Philippe Ciais ◽  
Bertrand Guenet ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Litter Quality ◽  
Plant Litter ◽  
Climate Mitigation ◽  
N Availability ◽  
Mineral N ◽  
Microbial Decomposition ◽  
Soil C ◽  
C Cycle

Abstract. Microbial decomposition of plant litter is a crucial process for the land carbon (C) cycle, as it directly controls the partitioning of litter C between CO2 released to the atmosphere versus the formation of new soil organic matter (SOM). Land surface models used to study the C cycle rarely considered flexibility in the decomposer C use efficiency (CUEd) defined by the fraction of decomposed litter C that is retained as SOM (as opposed to be respired). In this study, we adapted a conceptual formulation of CUEd based on assumption that litter decomposers optimally adjust their CUEd as a function of litter substrate C to nitrogen (N) stoichiometry to maximize their growth rates. This formulation was incorporated into the widely used CENTURY soil biogeochemical model and evaluated based on data from laboratory litter incubation experiments. Results indicated that the CENTURY model with new CUEd formulation was able to reproduce differences in respiration rate of litter with contrasting C : N ratios and under different levels of mineral N availability, whereas the default model with fixed CUEd could not. Using the model with flexible CUEd, we also illustrated that litter quality affected the long-term SOM formation. Litter with a small C : N ratio tended to form a larger SOM pool than litter with larger C : N ratios, as it could be more efficiently incorporated into SOM by microorganisms. This study provided a simple but effective formulation to quantify the effect of varying litter quality (N content) on SOM formation across temporal scales. Optimality theory appears to be suitable to predict complex processes of litter decomposition into soil C and to quantify how plant residues and manure can be harnessed to improve soil C sequestration for climate mitigation.

Post-thinning soil organic matter evolution and soil CO2 effluxes in temperate radiata pine plantations: impacts of moderate thinning regimes on the forest C cycle

2012 ◽  
Vol 42 (11) ◽  
pp. 1953-1964 ◽  
Author(s):  
Irene Fernandez ◽  
Juan Gabriel Álvarez-González ◽  
Beatríz Carrasco ◽  
Ana Daría Ruíz-González ◽  
Ana Cabaneiro
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Radiata Pine ◽  
Soil Samples ◽  
Mitigation Strategies ◽  
Change Scenario ◽  
Soil C ◽  
C Storage ◽  
C Cycle ◽  
C And N

Forest ecosystems can act as C sinks, thus absorbing a high percentage of atmospheric CO2. Appropriate silvicultural regimes can therefore be applied as useful tools in climate change mitigation strategies. The present study analyzed the temporal changes in the effects of thinning on soil organic matter (SOM) dynamics and on soil CO2 emissions in radiata pine ( Pinus radiata D. Don) forests. Soil C effluxes were monitored over a period of 2 years in thinned and unthinned plots. In addition, soil samples from the plots were analyzed by solid-state 13C-NMR to determine the post-thinning SOM composition and fresh soil samples were incubated under laboratory conditions to determine their biodegradability. The results indicate that the potential soil C mineralization largely depends on the proportion of alkyl-C and N-alkyl-C functional groups in the SOM and on the microbial accessibility of the recalcitrant organic pool. Soil CO2 effluxes varied widely between seasons and increased exponentially with soil heating. Thinning led to decreased soil respiration and attenuation of the seasonal fluctuations. These effects were observed for up to 20 months after thinning, although they disappeared thereafter. Thus, moderate thinning caused enduring changes to the SOM composition and appeared to have temporary effects on the C storage capacity of forest soils, which is a critical aspect under the current climatic change scenario.

scholarly journals Integrating plant litter quality, soil organic matter stabilization, and the carbon saturation concept

2015 ◽  
Vol 21 (9) ◽  
pp. 3200-3209 ◽  
Author(s):  
Michael J. Castellano ◽  
Kevin E. Mueller ◽  
Daniel C. Olk ◽  
John E. Sawyer ◽  
Johan Six
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Litter Quality ◽  
Plant Litter ◽  
Carbon Saturation ◽  
Organic Matter Stabilization

Soil microbial growth and carbon-use efficiency: ecological control mechanisms

2020 ◽  
Author(s):  
Johannes Rousk
Keyword(s):  
Heavy Metal ◽  
Soil Ph ◽  
Bacterial Growth ◽  
Fungal Growth ◽  
Plant Litter ◽  
N Availability ◽  
Mineral N ◽  
Soil C ◽  
Carbon Use Efficiency ◽  
Use Efficiency

<p>During the decomposition of organic matter (OM), microorganisms use the assimilated carbon (C) for biomass production or respiration, and the fraction of growth to total assimilation defines the microbial carbon-use efficiency (CUE). Therefore, microbial CUEs have direct consequences for the balance of C between atmosphere and soil, and is as such a central parameter to represent the global C cycle well in Global Cycling Models (GCMs). Despite its enormous leverage this factor remains critically underexplored. Based on the physiology of cultured microorganisms, it is anticipated that (H1) high nutrient availabilities will increase microbial CUE, (H2) that higher quality substrate will increase microbial CUE, (H3) that microbial communities more dominated by fungi will have higher CUE, and (H4) that microbial CUE will decrease in response to environmental stress. We combined extensive field surveys with experimental treatments in microcosms to assess our hypotheses. We sampled temperate forest soils, temperate agricultural soils, and subarctic forest soils, encompassing a wide range of soil pHs (4.0-7.1), nutrient availabilities (10<soil C/N<33), and soil OM qualities (7-fold differences in respiration per SOM). We also surveyed environmental pollution gradients where metallurgy had contaminated soil with high heavy metal concentrations in boreal forest and temperate grassland sites. We also subjected selected soils to microcosm experiments where soil pH (liming), mineral N (50 kg N ha<sup>-1</sup>), OM quality (plant litter), or heavy metal stress were manipulated and the resulting bacterial and fungal growth, respiration, and CUE were monitored over the course of 2 months.</p><p> </p><p>Fungal-to-bacterial growth ratios (F:B) ranged from 0.02 to 0.44 across the studied ecosystems, and that the fungal dominance was higher in soils with lower C:N ratio and higher C-quality. CUE ranged from 0.03 to 0.30, and values clustered most strongly according to site rather than level of soil N. CUE was higher in soil with high C:N ratios and high C-qualities. However, within each land-use type, a high mineral N-content did result in lower F:B and higher resulting CUE. In the microcosm experiments, plant litter addition stimulated the growth of fungi more than bacteria, while increasing soil pH stimulated bacteria more than fungi. Mineral N additions inhibited bacterial growth and stimulated fungal growth. This resulted in microbial CUE estimates in real time that ranged from ca 0.05 to 0.55, and where increased pH and litter increased values while mineral N supplements decreased values. Long-term exposure to heavy metals decreased microbial CUE, but only marginally, even at very high rates of metal exposure. Short-term exposure to metal stimulated microbial CUE in soil from contaminated sites, while CUE was reduced in soil with no history of metal contamination. In conclusion, a higher site soil C-quality coincided with lower F:B and higher CUE across the surveyed sites, while a higher N availability did not. A higher site N availability resulted in higher CUE and lower F:B within each site, while mineral N supplements in the microcosm induced the opposite response, suggesting that site-specific differences associated with fertility such as the effect of plant communities, overrode the influence of mineral N-availability.</p>

scholarly journals Plant litter quality affects the accumulation rate, composition, and stability of mineral-associated soil organic matter

2018 ◽  
Vol 125 ◽  
pp. 115-124 ◽  
Author(s):  
S. Carolina Córdova ◽  
Dan C. Olk ◽  
Ranae N. Dietzel ◽  
Kevin E. Mueller ◽  
Sotirios V. Archontouilis ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Litter Quality ◽  
Accumulation Rate ◽  
Plant Litter

Leaf-litter production and soil organic matter dynamics along a nitrogen-availability gradient in Southern Wisconsin (U.S.A.)

1983 ◽  
Vol 13 (1) ◽  
pp. 12-21 ◽  
Author(s):  
Knute J. Nadelhoffer ◽  
John D. Aber ◽  
Jerry M. Melillo
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Leaf Litter ◽  
N Mineralization ◽  
N Uptake ◽  
Mineral Soil ◽  
Litter Production ◽  
N Availability ◽  
Net N Mineralization ◽  
Mineral N

Annual net N mineralization in the 0–10 cm mineral soil zone of nine forest stands on silt–loam soils was measured using a series of insitu soil incubations from April 1980 through April 1981. Differences in soil organic matter (SOM) dynamics among sites were shown with net N mineralization ranging from 0.54 to 2.10 mg N mineralized•g SOM−1•year−1. This variation was not related to percent N in SOM. Net N mineralization varied seasonally with maximum rates in June and very low rates in winter. Nitrification rates were constant from May through September despite fluctuations in soil ammonium pools. Nitrification was greater than 50% of annual net N mineralization at all sites. N uptake by vegetation, as estimated by net N mineralization plus mineral N inputs via precipitation, with minor corrections for mineralization below the incubation depth and for mineral N losses to groundwater, ranged from 40.3 to 119.2 kg N•ha−1•year−1. Annual leaf and needle litter production ranged from 2.12 to 4.17 Mg•ha−1•year−1 and was strongly correlated with N uptake (r = 0.938, P < 0.01). N returned in leaf litter was also correlated with N uptake (r = 0.755, P < 0.05). Important feedbacks may exist between N availability and litter quality and quantity.

Characterization of Soil Organic Matter along an elevation gradient at Stelvio Pass (Italian Alps).

2020 ◽  
Author(s):  
Roberta Zangrando ◽  
Maria del Carmen Villoslada Hidalgo ◽  
Clara Turetta ◽  
Nicoletta Cannone ◽  
Francesco Malfasi ◽  
...  
Keyword(s):  
Climate Change ◽  
Organic Matter ◽  
Soil Organic Matter ◽  
Organic Carbon ◽  
Elevation Gradient ◽  
Total Carbon ◽  
Plant Component ◽  
Soil C ◽  
C Cycle ◽  
C Stocks

&lt;p&gt;Climate Change (CC) has evident impacts on the biotic and abiotic components of ecosystems.&lt;/p&gt;&lt;p&gt;Soil is the third largest reservoir of carbon, next to the lithosphere and the oceans, and stores approximately 1500 Gt in the top1 m depth. &amp;#160;Even small changes in soil C stocks could have a vast impact on atmospheric CO&lt;sub&gt;2 &lt;/sub&gt;concentration. Elevated surface temperature can substantially affect global C budgets and produce positive or negative feedbacks to climate change. Therefore, understanding the response of soil organic carbon (SOC) stocks to warming is of critical importance to evaluate the feedbacks between terrestrial C cycle and climate change.&lt;/p&gt;&lt;p&gt;In comparison to other ecosystems, the areas at high altitudes and latitudes are the most vulnerable. In permafrost areas of the Northern Hemisphere the CC has already determined an increase in greenhouse gas emissions, shrub vegetation and variation in the composition of microbial communities. While numerous studies have been performed in Arctic, much less numerous are available for high altitude areas. These areas are a quarter of the emerged lands &amp;#160;and have suffered strong impacts from the CC. Mountain permafrost makes up 14% of global permafrost, stores large quantities of organic carbon (SOC), and can release large quantities of CO&lt;sub&gt;2&lt;/sub&gt; due to climate change. However, permafrost contribution to the IPCC global budget has not yet been correctly quantified, in particular for ecosystems of prairie and shrubland, which alone could incorporate over 80Pg of C between soil and biomass. In the last decades, the plant component has undergone migration of species to higher altitudes, expansion of shrubs, variations in floristic composition and dominance, variations in area distribution. The expansion of the shrubs accelerates the regression of alpine meadows and snow valleys.&lt;/p&gt;&lt;p&gt;The sampling activities have been carried out in July and September, from September 2017 to July 2019 in an area near Stelvio Pass (2,758 m a.s.l.) (Italian Central-Eastern Alps) along an altitude gradient. &amp;#160;&amp;#160;Two sampling sites located at 2600 m a.s.l. and 2200 m a.s.l. in altitude, corresponding to about 3&amp;#176; C difference in the average annual air temperature were chosen. At the 2600 m site, warming experiments using open-top chambers (OTCs) to investigate how climate warming affects SOC were performed.&lt;/p&gt;&lt;p&gt;In order to characterize the SOM (Soil Organic Matter), Total carbon (TC), Organic carbon (OC), Total Nitrogen (TN) and Dissolved Organic Carbon (DOC) were determined in soils. TC and TN were determined in biomass. In both soils and biomass were analyzed to quantify the distribution of stable isotopes of C and N, &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C and &amp;#948;&lt;sup&gt;15&lt;/sup&gt;N.&lt;/p&gt;

scholarly journals Land-use perturbations in ley grassland decouple the degradation of ancient soil organic matter from the storage of newly derived carbon inputs

SOIL ◽  
2020 ◽  
Vol 6 (2) ◽  
pp. 435-451
Author(s):  
Marco Panettieri ◽  
Denis Courtier-Murias ◽  
Cornelia Rumpel ◽  
Marie-France Dignac ◽  
Gonzalo Almendros ◽  
...  
Keyword(s):  
Land Use ◽  
Organic Matter ◽  
Soil Organic Matter ◽  
Temperate Climate ◽  
Soil C ◽  
Legacy Effect ◽  
C Cycle ◽  
13C Nuclear Magnetic Resonance ◽  
Microbial Proliferation ◽  
Soil C Cycle

Abstract. In a context of global change, soil has been identified as a potential carbon (C) sink, depending on land-use strategies. To detect the trends in carbon stocks after the implementation of new agricultural practices, early indicators, which can highlight changes in short timescales, are required. This study proposes the combined use of stable isotope probing and chemometrics applied to solid-state 13C nuclear magnetic resonance (NMR) spectra to unveil the dynamics of the storage and mineralization of soil carbon (C) pools. We focused on light organic matter fractions isolated by density fractionation of soil water stable aggregates because they respond faster to changes in land use than the total soil organic matter (SOM). Samples were collected from an agricultural field experiment with grassland, continuous maize cropping, and ley grassland under temperate climate conditions. Our results indicated contrasting aggregate dynamics depending on land-use systems. Under our experimental conditions, grassland returns larger amounts of C as belowground inputs than maize cropping, evidencing a different distribution of light C fractions between aggregate classes. Coarse aboveground inputs from maize contributed mostly to larger macroaggregates. Land-use changes with the introduction of ley grassland provoked a decoupling of the storage and/or degradation processes after the grassland phase. The newly derived maize inputs were barely degraded during the first 3 years of maize cropping, whereas grassland-derived material was depleted. As a whole, results suggest large microbial proliferation as shown by 13C NMR under permanent grassland, then reduced within the first years after the land-use conversion, and finally restored. The study highlighted a fractal structure of the soil, determining a scattered spatial distribution of the cycles of storage and degradation of soil organic matter related to detritusphere dynamics. As a consequence, vegetal inputs from a new land use are creating new detritusphere microenvironments that may be disconnected from the dynamics of C cycle of the previous land use. The formation of those different and unconnected microenvironments may explain the observed legacy effect of the previous land use, since each microenvironment type contributes separately to the overall soil C cycle. The effects of the new land use on the soil C cycle are delayed until the different detritusphere microenvironments remain unconnected, and the ones from the previous land use represent the predominant microenvironment type. Increasing knowledge of the soil C dynamics at a fine scale will be helpful in refining the prediction models and land-use policies.

Effects of climate change on soil organic matter chemical composition and carbon content in different physical fractions

2021 ◽  
Author(s):  
Moritz Mohrlok ◽  
Victoria Martin ◽  
Alberto Canarini ◽  
Wolfgang Wanek ◽  
Michael Bahn ◽  
...  
Keyword(s):  
Climate Change ◽  
Organic Matter ◽  
Chemical Composition ◽  
Soil Organic Matter ◽  
Soil C ◽  
Size Classes ◽  
Soil Fractions ◽  
Total Soil ◽  
C And N ◽  
Amp Clay

&lt;p&gt;Soil organic matter (SOM) is composed of many pools with different properties (e.g. turnover times) which are generally used in biogeochemical models to predict carbon (C) dynamics. Physical fractionation methods are applied to isolate soil fractions that correspond to these pools. This allows the characterisation of chemical composition and C content of these fractions. There is still a lack of knowledge on how these individual fractions are affected by different climate change drivers, and therefore the fate of SOM remains elusive. We sampled soils from a multifactorial climate change experiment in a managed grassland in Austria four years after starting the experiment to investigate the response of SOM in physical soil fractions to temperature (eT: ambient and elevated by +3&amp;#176;C), atmospheric CO&lt;sub&gt;2&lt;/sub&gt;-concentration (eCO&lt;sub&gt;2&lt;/sub&gt;: ambient and elevated by +300 ppm) and to a future climate treatment (eT x eCO&lt;sub&gt;2&lt;/sub&gt;: +3&amp;#176;C and + 300 ppm). A combination of slaking and wet sieving was used to obtain three size classes: macro-aggregates (maA, &gt; 250 &amp;#181;m), micro-aggregates (miA, 63 &amp;#181;m &amp;#8211; 250 &amp;#181;m) and free silt &amp; clay (sc, &lt; 63 &amp;#181;m). In both maA and miA, four different physical OM fractions were then isolated by density fractionation (using sodium polytungstate of &amp;#961; = 1.6 g*cm&lt;sup&gt;-3&lt;/sup&gt;, ultrasonication and sieving): Free POM (fPOM), intra-aggregate POM (iPOM), silt &amp; clay associated OM (SCaOM) and sand-associated OM (SaOM). We measured C and N contents and isotopic composition by EA-IRMS in all fractions and size classes and used a Pyrolysis-GC/MS approach to assess their chemical composition. For eCO&lt;sub&gt;2&lt;/sub&gt; and eT x eCO&lt;sub&gt;2 &lt;/sub&gt;plots, an isotope mixing-model was used to calculate the proportion of recent C derived from the elevated CO&lt;sub&gt;2 &lt;/sub&gt;treatment. Total soil C and N did not significantly change with treatments.&amp;#160; eCO&lt;sub&gt;2&lt;/sub&gt; decreased the relative proportion of maA-mineral-associated C and increased C in fPOM and iPOM. About 20% of bulk soil C was represented by the recent C derived from the CO&lt;sub&gt;2&lt;/sub&gt; fumigation treatment. This significantly differed between size classes and density fractions (p &lt; 0.001), which indicates inherent differences in OM age and turnover. Warming reduced the amount of new C incorporated into size classes. We found that each size class and fraction possessed a unique chemical fingerprint, but this was not significantly changed by the treatments. Overall, our results show that while climate change effects on total soil C were not significant after 4 years, soil fractions showed specific effects. Chemical composition differed significantly between size classes and fractions but was unaffected by simulated climate change. This highlights the importance to separate SOM into differing pools, while including changes to the molecular composition might not be necessary for improving model predictions.&amp;#160;&amp;#160;&amp;#160;&amp;#160;&lt;/p&gt;

scholarly journals Predicting decadal trends and transient responses of radiocarbon storage and fluxes in a temperate forest soil

2012 ◽  
Vol 9 (8) ◽  
pp. 3013-3028 ◽  
Author(s):  
C. A. Sierra ◽  
S. E. Trumbore ◽  
E. A. Davidson ◽  
S. D. Frey ◽  
K. E. Savage ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Soil Carbon ◽  
Empirical Model ◽  
Temperate Forest ◽  
Global Environmental Change ◽  
Carbon Dynamics ◽  
Co2 Efflux ◽  
Soil C ◽  
Soil Carbon Dynamics

Abstract. Representing the response of soil carbon dynamics to global environmental change requires the incorporation of multiple tools in the development of predictive models. An important tool to construct and test models is the incorporation of bomb radiocarbon in soil organic matter during the past decades. In this manuscript, we combined radiocarbon data and a previously developed empirical model to explore decade-scale soil carbon dynamics in a temperate forest ecosystem at the Harvard Forest, Massachusetts, USA. We evaluated the contribution of different soil C fractions to both total soil CO2 efflux and microbially respired C. We tested the performance of the model based on measurable soil organic matter fractions against a decade of radiocarbon measurements. The model was then challenged with radiocarbon measurements from a warming and N addition experiment to test multiple hypotheses about the different response of soil C fractions to the experimental manipulations. Our results showed that the empirical model satisfactorily predicts the trends of radiocarbon in litter, density fractions, and respired CO2 observed over a decade in the soils not subjected to manipulation. However, the model, modified with prescribed relationships for temperature and decomposition rates, predicted most but not all the observations from the field experiment where soil temperatures and nitrogen levels were increased, suggesting that a larger degree of complexity and mechanistic relations need to be added to the model to predict short-term responses and transient dynamics.

Sign in / Sign up

Export Citation Format

Share Document