Free and protected soil organic carbon dynamics respond differently to abandonment of mountain grassland

Abstract. Land-use change (LUC) and management are among the major driving forces of soil carbon (C) storage. Abandonment of mountain grassland promotes accumulation of aboveground biomass and litter, but related responses of soil organic matter (SOM) dynamics are uncertain. To determine SOM-C turnover we sampled 0–10 cm of soils in the European Alps along two land-use gradients (hay meadows, grazed pastures and abandoned grasslands) of different management intensity. A first land-use gradient was located at Stubai Valley (MAT: 3 °C, MAP: 1097 mm) in Austria and a second at Matsch Valley (MAT: 6.6 °C, MAP: 527 mm) in Italy. We estimated C input and decomposition rates of water-floatable and free particulate organic matter (wPOM, fPOM <1.6 g cm−3) and aggregate-occluded particulate and mineral-associated organic matter (oPOM <1.6 g cm−3, mOM >1.6 g cm−3) using bomb radiocarbon. In mountain grasslands average C turnover increased from roots (3 yr) < wPOM (5 yr) < fPOM (80 yr) < oPOM (108 yr) < mOM (192 yr). Among SOM fractions the turnover of fPOM-C varied most in relation to management. Along both land-use gradients C input pathways shifted from root-derived towards litter-derived C. The C input rates of both wPOM-C and fPOM-C were affected by land management at both sites. In contrast, oPOM-C and mOM-C dynamics remained relatively stable in response to grassland abandonment. Carbon accumulation rates of free POM decreased strongly with time since LUC (10, 25 and 36 yr). For wPOM-C, for example, it decreased from 7.4 > 2.2> 0.8 g C m−2 yr−1. At both sites, most C was sequestered in the first years after LUC and free POM reached new steady state within 20–40 yr. We conclude that w-and fPOM-C vs. oPOM-C dynamics respond differently to grassland management change and thus POM does not represent a homogeneous SOM fraction. Sequestered C is stored in the labile POM and not stabilized in the long-term. Thus, it is unlikely that abandonment, the dominant form of LUC in the European Alps, provides a substantial net soil C sink.

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Free and protected soil organic carbon dynamics respond differently to abandonment of mountain grassland

Biogeosciences Discussions ◽

10.5194/bgd-8-9943-2011 ◽

2011 ◽

Vol 8 (5) ◽

pp. 9943-9976 ◽

Cited By ~ 3

Author(s):

S. Meyer ◽

J. Leifeld ◽

M. Bahn ◽

J. Fuhrer

Keyword(s):

Land Use ◽

Organic Matter ◽

Driving Forces ◽

Carbon Accumulation ◽

European Alps ◽

Decomposition Rates ◽

Dominant Form ◽

Mountain Grassland ◽

C Dynamics ◽

C Input

Abstract. Land-use change (LUC) and management are among the major driving forces of soil carbon (C) storage. Abandonment of mountain grassland promotes accumulation of aboveground biomass and litter, but related responses of soil organic matter (SOM) dynamics are uncertain. To determine SOM-C turnover we sampled 0–10 cm of soils along land-use gradients (hay meadows, grazed pastures and abandoned grasslands) in the European Alps varying in management intensity at Stubai Valley (MAT: 3 °C, P: 1097 mm) in Austria and Matsch Valley (MAT: 6.6 °C, P: 527 mm) in Italy. We determined C input and decomposition rates of labile water-floatable and free particulate organic matter (wPOM, fPOM <1.6 g cm−3) and stable aggregate-occluded particulate and mineral-associated organic matter (oPOM <1.6 g cm−3, mOM >1.6 g cm−3) using bomb radiocarbon. At both sites C turnover decreased from w- and fPOM (4–8 yr) to oPOM (76–142 yr) to mOM (142–250 yr). Following abandonment C input pathways shifted from root-derived towards litter-derived C. The decomposition rates of labile wPOM-C declined with a decrease in litter quality, while both C input and C decomposition rates of labile fPOM increased with an increase in litter quantity. In contrast, protected stable SOM-C (oPOM-C, mOM-C) dynamics remained relatively unaffected by grassland abandonment. Carbon accumulation rates of labile POM fractions decreased strongly with time since LUC (10, 25 and 36 yr). For wPOM-C, for example, it decreased from 7.45 &pm; 0.99 to 2.18 &pm; 1.06 to 0.82 &pm; 0.21 g C m−2 yr−1. At both sites, most C was sequestered in the first years after LUC and labile SOM fractions reached new steady state within 20–40 yr. We concluded that w-and fPOM-C vs. oPOM-C dynamics respond differently to grassland management change and thus POM does not represent a homogeneous SOM fraction. Sequestered C is stored in the labile readily decomposable POM fractions and not stabilized in the long-term. Thus it is unlikely that abandonment, the dominant form of LUC in the European Alps, provides a substantial net soil C sink.

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No long-term effect of land-use activities on soil carbon dynamics in tropical montane grasslands

10.5194/bg-2017-113 ◽

2017 ◽

Author(s):

Viktoria Oliver ◽

Imma Oliveras ◽

Jose Kala ◽

Rebecca Lever ◽

Yit Arn Teh

Keyword(s):

Land Use ◽

Organic Matter ◽

Co2 Fluxes ◽

Soil Co2 ◽

Soil C ◽

C Dynamics ◽

Total Soil ◽

C Stocks ◽

Montane Grasslands

Abstract. Montane tropical soils are a large carbon (C) reservoir, acting as both a source and a sink of CO2. Enhanced CO2 emissions originate, in large part, from the decomposition and losses of soil organic matter (SOM) following anthropogenic disturbances. Therefore, quantitative knowledge of the stabilization and decomposition of SOM is necessary in order to understand, assess and predict the impact of land management in the tropics. In particular, labile SOM is an early and sensitive indicator of how SOM responds to changes in land use and management practices, which could have major implications for long term carbon storage and rising atmospheric CO2 concentrations. The aim of this study was to investigate the impacts of grazing and fire history on soil C dynamics in the Peruvian montane grasslands; an understudied ecosystem, which covers approximately a quarter of the land area in Peru. A combination of density and particle-size fractionation was used to quantify the labile and stable organic matter pools, along with soil CO2 flux and decomposition measurements. Grazing and burning together significantly increased soil CO2 fluxes and decomposition rates and reduced temperature as a driver. Although there was no significant effect of land use on total soil C stocks, the combination of burning and grazing decreased the proportion of C in the free LF, especially at the lower depths (10–20 and 20–30 cm). The free LF in the control soils made 20 % of the bulk soil mass and 30 % of the soil C content compared to the burnt-grazed soils, which had the smallest recovery of free LF (10 %) and significantly lower C content (14 %). The burnt soils had a much higher proportion of C in the occluded LF (12 %) compared to the non-burnt soils (7 %) and there was no significant difference among the treatments in the heavy F (~ 70 %). The synergistic effect of burning and grazing caused changes to the soil C dynamics. CO2 fluxes were increased and the dominant temperature driver was obscured by some other process, such as changes in plant C and N allocation promoting autotrophic respiration. In addition, the free LF was negatively affected when these two anthropogenic activities took place on the same site. Most likely a result of reduced detritus being incorporated into the soil. A positive finding from this study is that the total soil C stocks were not significantly affected and the long term C storage in the occluded LF and heavy F were not negatively impacted. Possibly this is because of low intensity fire, fire-resilient grasses and the grazing pressure is below the threshold to cause severe degradation.

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The effects of burning and grazing on soil carbon dynamics in managed Peruvian tropical montane grasslands

Biogeosciences ◽

10.5194/bg-14-5633-2017 ◽

2017 ◽

Vol 14 (24) ◽

pp. 5633-5646 ◽

Cited By ~ 3

Author(s):

Viktoria Oliver ◽

Imma Oliveras ◽

Jose Kala ◽

Rebecca Lever ◽

Yit Arn Teh

Keyword(s):

Land Use ◽

Organic Matter ◽

Co2 Fluxes ◽

Soil Co2 ◽

Soil C ◽

C Dynamics ◽

Total Soil ◽

C Stocks ◽

Montane Grasslands

Abstract. Montane tropical soils are a large carbon (C) reservoir, acting as both a source and a sink of CO2. Enhanced CO2 emissions originate, in large part, from the decomposition and losses of soil organic matter (SOM) following anthropogenic disturbances. Therefore, quantitative knowledge of the stabilization and decomposition of SOM is necessary in order to understand, assess and predict the impact of land management in the tropics. In particular, labile SOM is an early and sensitive indicator of how SOM responds to changes in land use and management practices, which could have major implications for long-term carbon storage and rising atmospheric CO2 concentrations. The aim of this study was to investigate the impacts of grazing and fire history on soil C dynamics in the Peruvian montane grasslands, an understudied ecosystem, which covers approximately a quarter of the land area in Peru. A density fractionation method was used to quantify the labile and stable organic matter pools, along with soil CO2 flux and decomposition measurements. Grazing and burning together significantly increased soil CO2 fluxes and decomposition rates and reduced temperature as a driver. Although there was no significant effect of land use on total soil C stocks, the combination of burning and grazing decreased the proportion of C in the free light fraction (LF), especially at the lower depths (10–20 and 20–30 cm). In the control soils, 20 % of the material recovered was in the free LF, which contained 30 % of the soil C content. In comparison, the burnt–grazed soil had the smallest recovery of the free LF (10 %) and a significantly lower C content (14 %). The burnt soils had a much higher proportion of C in the occluded LF (12 %) compared to the not-burnt soils (7 %) and there was no significant difference among the treatments in the heavy fraction (F) ( ∼  70 %). The synergistic effect of burning and grazing caused changes to the soil C dynamics. CO2 fluxes were increased and the dominant temperature driver was obscured by some other process, such as changes in plant C and N allocation. In addition, the free LF was reduced when these two anthropogenic activities took place on the same site – most likely a result of reduced detritus being incorporated into the soil. A positive finding from this study is that the total soil C stocks were not significantly affected and the long-term (+10 years) C storage in the occluded LF and heavy F were not negatively impacted. Possibly this is because of low-intensity fire, fire-resilient grasses and because the grazing pressure is below the threshold necessary to cause severe degradation.

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Land use intensification effects on soil C dynamics in subtropical grazing land ecosystems

Tropical Grasslands - Forrajes Tropicales ◽

10.17138/tgft(2)142-144 ◽

2014 ◽

Vol 2 (1) ◽

pp. 142 ◽

Cited By ~ 2

Author(s):

Maria L. Silveira ◽

Sutie Xu ◽

Julius Adewopo ◽

Kanika S. Inglett ◽

◽

...

Keyword(s):

Land Use ◽

Grazing Land ◽

Soil C ◽

Land Use Intensification ◽

C Dynamics

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Regulation of priming effect by soil organic matter stability over a broad geographic scale

Nature Communications ◽

10.1038/s41467-019-13119-z ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 20

Author(s):

Leiyi Chen ◽

Li Liu ◽

Shuqi Qin ◽

Guibiao Yang ◽

Kai Fang ◽

...

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Priming Effect ◽

Basal Respiration ◽

Soil Conditions ◽

The Tibetan Plateau ◽

Geographic Scale ◽

Soil C ◽

Chemical Structures ◽

C Dynamics

Abstract The modification of soil organic matter (SOM) decomposition by plant carbon (C) input (priming effect) represents a critical biogeochemical process that controls soil C dynamics. However, the patterns and drivers of the priming effect remain hidden, especially over broad geographic scales under various climate and soil conditions. By combining systematic field and laboratory analyses based on multiple analytical and statistical approaches, we explore the determinants of priming intensity along a 2200 km grassland transect on the Tibetan Plateau. Our results show that SOM stability characterized by chemical recalcitrance and physico-chemical protection explains more variance in the priming effect than plant, soil and microbial properties. High priming intensity (up to 137% of basal respiration) is associated with complex SOM chemical structures and low mineral-organic associations. The dependence of priming effect on SOM stabilization mechanisms should be considered in Earth System Models to accurately predict soil C dynamics under changing environments.

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Influence of climate change factors on carbon dynamics in northern forested peatlands

Canadian Journal of Soil Science ◽

10.4141/s05-089 ◽

2006 ◽

Vol 86 (Special Issue) ◽

pp. 269-280 ◽

Cited By ~ 28

Author(s):

C. C. Trettin ◽

R. Laiho ◽

K. Minkkinen ◽

J. Laine

Keyword(s):

Climate Change ◽

Organic Matter ◽

Management Practices ◽

Atmospheric Temperature ◽

Soil C ◽

Altered Hydrology ◽

Biogeochemical Models ◽

C Dynamics ◽

C Balance ◽

C Cycle

Peatlands are carbon-accumulating wetland ecosystems, developed through an imbalance among organic matter production and decomposition processes. Soil saturation is the principal cause of anoxic conditions that constrain organic matter decay. Accordingly, changes in the hydrologic regime will affect the carbon (C) dynamics in forested peatlands. Our objective is to review ecological studies and experiments on managed peatlands that provide a basis for assessing the effects of an altered hydrology on C dynamics. We conclude that climate change influences will be mediated primarily through the hydrologic cycle. A lower water table resulting from altered precipitation patterns and increased atmospheric temperature may be expected to decrease soil CH4 and increase CO2 emissions from the peat surface. Correspondingly, the C balance in forested peatlands is also sensitive to management and restoration prescriptions. Increases in soil CO2 efflux do not necessarily equate with net losses from the soil C pool. While the fundamentals of the C balance in peatlands are well-established, the combined affects of global change stressors and management practices are best considered using process-based biogeochemical models. Long-term studies are needed both for validation and to provide a framework for longitudinal assessments of the peatland C cycle. Key words: Peatland, carbon cycle, methane, forest, wetland.

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Soil organic matter dynamics in changing forests: linking ecosystem manipulation experiments with soil inventories across Switzerland

10.5194/egusphere-egu2020-18241 ◽

2020 ◽

Author(s):

Frank Hagedorn ◽

Sia Gosheva ◽

Stephan Zimmermann ◽

Konstantin Gavazov

Keyword(s):

Land Use ◽

Organic Matter ◽

Soil Organic Matter ◽

Forest Soils ◽

Dry Forest ◽

Soil Profiles ◽

Forest Age ◽

Forest Expansion ◽

Soil C ◽

Ecosystem Manipulation

Forest soils are storing large quantities of carbon, but their quantitative role in sequestering C is less certain. In principal, soils developed over millennia are assumed to be &#8216;in equilibrium&#8217; with minimal C stock changes. This concept is challenged by forest soil inventories (in Germany and France) indicate a substantial increase in soil C storage. However, soil organic matter (SOM) storage is susceptible to recent changes in forests - climate warming and droughts, increasing forest disturbances, and a more intensive forest management are all potentially increasing SOM turnover which may turn forest soils into C sources. Here, I will critically discuss the role in Swiss forest soils as C sinks by presenting data from 1000 soil profiles across environmental gradients and from flux measurements in large scale ecosystem manipulation experiments.Swiss forests soils are among the C-richest soils in Europe storing on average 140 t C/ha. Analysis of 1000 forest soils show that these SOM stocks are caused by their high contents in potential SOM sorbents (pH, Al+Fe-oxides, Ca, clay), but also by the cool temperatures and high amounts of precipitation. Climate manipulation experiments suggest Swiss forest soils are vulnerable to loose C with expected climatic changes. A six year long soil warming experiment at treeline revealed soil C losses, while a 15 year long irrigation experiment in a dry forest induced C gains in the mineral soil, implying that a warmer and more frequent droughts will lead to C losses.Switzerland - as other European mountainous areas &#8211; is currently experiencing a major change in land-use due to land abandonment, with the forests expanding by 3 to 4% per decade. Forest expansion affects a multitude of factors driving SOM cycling and storage, including the quantity and quality of organic matter inputs above and below the ground, a cooler and drier microclimate, and change in microbial diversity and activity. In contrast to the intuitive assumption that forests expansion leads to C gains in soils, measurements along an afforestation chronosequence of alpine grassland show that forest expansion leads to minimal changes in SOM stocks but a strong change in SOM quality. Soils gains in particulate organic matter with increasing forest age but lose C in mineral-associated organic matter. In support, reconstructing forest cover ages of 850 soil profiles showed that forest age and hence time since conversion into forest (predominantly from grasslands) did not significantly affect total SOM stocks, while other factors, especially physico-chemical soil characteristics and climate were more important. Overall, these results show that the inherently C rich forest soils in Switzerland are unlikely to gain additional C but rather loose it in response to the ongoing changes in climate and land-use.

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Soil Organic Carbon Accumulation under Different Forms of Organo-Mineral Fertilizers and Methods of Their Application on Ukrainian Black Soil

10.5194/egusphere-egu2020-3282 ◽

2020 ◽

Cited By ~ 1

Author(s):

Viktoriia Hetmanenko ◽

Ievgen Skrylnyk ◽

Anzhela Kutova

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Soil Organic Carbon ◽

Black Soil ◽

Carbon Accumulation ◽

Mineral Fertilizers ◽

Fertilizer Treatment ◽

Soil C ◽

Significant Difference ◽

Humus Composition

Soil organic carbon management is a key element in solving such urgent global-scale challenges as overcoming degradation of soils and mitigating climate change. Organic fertilizers application has a significant potential for sequestering C in soils, but their efficiency depends on decomposition characteristics. Firstly, it noted the dependence of resynthesis of humic compounds in a soil on a quality of organic inputs, secondly - a need for zonal approach to fertilizers production based on amphiphile properties of macromolecules.The present study was conducted in long-term field experiment on black soil in Forrest-Steppe zone of Ukraine. The technology of production of organo-mineral fertilizers (OMFs) was based on the regulated processing of livestock waste with mineral components to stabilize it with hydrophobic bonds. OMFs in amorphous and granular form were compared in case of broadcast and band method of incorporation. The dose of OMF input was equivalent 350 C kg ha-1 and 80 N, 80 P, 80 K kg ha-1. Organic carbon content in soil was determined by Turin method. Different organic matter fractions were isolated: humic acids (HA), fulvic acids (FA), and humin.The soil C accumulation rates in OMF treatment was by 15 % higher than in manure treatment and up to 70 % higher than in chemical fertilizer treatment, respectively. The soil C accumulation was strongly influenced by the form of OMF and method of their application. The highest TOC level was found over band application of amorphous OMF, accumulating 6.2 t C ha&#8211;1 yr&#8211;1 in 0-20 cm soil layer. Lower efficiency of broadcast incorporation OMFs could be explained by more intensive mineralization due to higher aeration. Taking into account the effect of OMFs on C stock an advantage of amorphous form versus granulated OMF with similar composition was proven. Black soil on control plot (without fertilization) had almost equal ratio between HA, FA and humin in humus composition. The content of humic compound increased in all treatments. Applying OMF significantly increased HA content in black soil compared to applying mineral fertilizer. OMFs application promoted the increase of the degree of condensation of organic matter. The highest HA/FA was found under the effect of broadcast incorporation OMF. That means that low molecular weight compounds were rapidly degraded while more resistant to mineralization HA were formed in soil. There was no significant difference in humus composition between amorphous and granulated OMF.

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Continuous Maize Cropping Accelerates Loss of Soil Organic Matter in Northern Thailand as Revealed by Natural 13C Abundance

10.21203/rs.3.rs-1149438/v1 ◽

2021 ◽

Author(s):

Kazumichi Fujii ◽

Risako Mitani ◽

Yoshiyuki Inagaki ◽

Chie Hayakawa ◽

Makoto Shibata ◽

...

Keyword(s):

Land Use ◽

Organic Matter ◽

Upland Rice ◽

Rice Fields ◽

C4 Plant ◽

Soil C ◽

Fallow Period ◽

C Stocks ◽

Maize Cultivation ◽

Continuous Maize

Abstract AimsThe loss of soil organic matter (SOM) has widely been reported in the tropics after changing land use from shifting cultivation to continuous cropping. We tested whether continuous maize cultivation accelerates SOM loss compared to upland rice and forest fallow. Methods: Because litter sources include C4 plants (maize in maize fields and Imperata grass in upland rice fields) in Thailand, C3-derived and C4-derived SOM can be traced using the differences in natural 13C abundance (δ13C) between C3 and C4 plants. We analyzed the effects of land use history (cultivation or forest fallow period) on C stocks in the surface soil. Soil C stocks decreased with the cultivation period in both upland rice and maize fields. ResultsThe rate of soil organic carbon loss was higher in maize fields than in upland rice fields. The decomposition rate constant (first order kinetics) of C3-plant-derived SOM was higher in the maize fields than in the upland rice fields and the C4-plant-derived SOM in the forest fallow. Soil surface exposure and low input of root-derived C in the maize fields are considered to accelerate SOM loss. Soil C stocks increased with the forest fallow period, consistent with the slow decomposition of C4-plant-derived SOM in the forest fallows. ConclusionsContinuous maize cultivation accelerates SOM loss, while forest fallow and upland rice cultivation could mitigate the SOM loss caused by continuous maize cultivation.

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Soil organic matter dynamics in a North America tallgrass prairie after 9 yr of experimental warming

Biogeosciences ◽

10.5194/bg-8-1487-2011 ◽

2011 ◽

Vol 8 (6) ◽

pp. 1487-1498 ◽

Cited By ~ 46

Author(s):

X. Cheng ◽

Y. Luo ◽

X. Xu ◽

R. Sherry ◽

Q. Zhang

Keyword(s):

Organic Matter ◽

Global Warming ◽

Soil Organic Matter ◽

North America ◽

Tallgrass Prairie ◽

Decay Rates ◽

Experimental Warming ◽

Δ13c And Δ15n ◽

Soil C ◽

C Input

Abstract. The influence of global warming on soil organic matter (SOM) dynamics in terrestrial ecosystems remains unclear. In this study, we combined soil fractionation with isotope analyses to examine SOM dynamics after nine years of experimental warming in a North America tallgrass prairie. Soil samples from the control plots and the warmed plots were separated into four aggregate sizes (>2000 μm, 250–2000 μm, 53–250 μm, and <53 μm), and three density fractions (free light fraction – LF, intra-aggregate particulate organic matter – iPOM, and mineral-associated organic matter – mSOM). All fractions were analyzed for their carbon (C) and nitrogen (N) content, and δ13C and δ15N values. Warming did not significantly effect soil aggregate distribution and stability but increased C4-derived C input into all fractions with the greatest in LF. Warming also stimulated decay rates of C in whole soil and all aggregate sizes. C in LF turned over faster than that in iPOM in the warmed soils. The δ15N values of soil fractions were more enriched in the warmed soils than those in the control, indicating that warming accelerated loss of soil N. The δ15N values changed from low to high, while C:N ratios changed from high to low in the order LF, iPOM, and mSOM due to increased degree of decomposition and mineral association. Overall, warming increased the input of C4-derived C by 11.6 %, which was offset by the accelerated loss of soil C. Our results suggest that global warming simultaneously stimulates C input via shift in species composition and decomposition of SOM, resulting in negligible net change in soil C.

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