Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
101,532
result(s) for
"organic carbon"
Sort by:
The role of clay content and mineral surface area for soil organic carbon storage in an arable toposequence
Correlations between organic carbon (OC) and fine mineral particles corroborate the important role of the abundance of soil minerals with reactive surfaces to bind and increase the persistence of organic matter (OM). The storage of OM broadly consists of particulate and mineral-associated forms. Correlative studies on the impact of fine mineral soil particles on OM storage mostly combined data from differing sites potentially confounded by other environmental factors. Here, we analyzed OM storage in a soil clay content gradient of 5–37% with similar farm management and mineral composition. Throughout the clay gradient, soils contained 14 mg OC g⁻¹ on average in the bulk soil without showing any systematic increase. Density fractionation revealed that a greater proportion of OC was stored as occluded particulate OM in the high clay soils (18–37% clay). In low clay soils (5–18% clay), the fine mineral-associated fractions had up to two times higher OC contents than high clay soils. Specific surface area measurements revealed that more mineral-associated OM was related to higher OC loading. This suggests that there is a potentially thicker accrual of more OM at the same mineral surface area within fine fractions of the low clay soils. With increasing clay content, OM storage forms contained more particulate OC and mineral-associated OC with a lower surface loading. This implies that fine mineral-associated OC storage in the studied agricultural soils was driven by thicker accrual of OM and decoupled from clay content limitations.
Journal Article
Root effects on soil organic carbon
From recent developments on how roots affect soil organic carbon (SOC) an apparent paradox has emerged where roots drive SOC stabilization causing SOC accrual, but also SOC destabilization causing SOC loss. We synthesize current results and propose the new Rhizo-Engine framework consisting of two linked components: microbial turnover and the soil physicochemical matrix. The Rhizo-Engine is driven by rhizodeposition, root turnover, and plant uptake of nutrients and water, thereby accelerating SOC turnover through both stabilization and destabilization mechanisms. This Rhizo-Engine framework emphasizes the need for a more holistic approach to study root-driven SOC dynamics. This framework would provide better understanding of plant root effects on soil carbon sequestration and the sensitivity of SOC stocks to climate and land-use changes.
Journal Article
Changes in soil particulate and mineral-associated organic carbon concentrations under nitrogen addition in China—a meta-analysis
AimsAs the largest terrestrial carbon (C) pool, soil organic carbon (SOC) plays a critical role in the global C cycle. Particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) are currently popular methods for the fractionation and analysis of SOC. Nitrogen (N) addition affects SOC dynamics. However, the characteristics of POC and MAOC and their potential drivers under N (inorganic and organic N) addition remain unclear.MethodsWe conducted a meta-analysis based on data from 50 studies on terrestrial ecosystems in China to investigate the responses of SOC, POC, and MAOC to N addition, and to reveal the factors influencing POC and MAOC.ResultsThe results showed that organic N addition significantly increased the SOC (effect size: 0.35), POC (effect size: 0.68), and MAOC (effect size: 0.20), whereas inorganic N addition significantly increased SOC (effect size: 0.10) and POC (effect size: 0.21). POC and MAOC concentrations increased with fertilization duration (years); however, the physical stability of SOC remained unchanged. No correlation was observed between the SOC sequestration rate and duration of fertilization under inorganic N addition, whereas the SOC sequestration rate showed a trend of first increasing and then decreasing with organic N addition.ConclusionsThe main factors affecting POC and MAOC were microbial biomass carbon (MBC) and soil pH, and the driving factors of POC and MAOC were different under inorganic and organic N additions. Additionally, N addition may decrease the stability of the SOC pool.
Journal Article
Mineral protection regulates long-term global preservation of natural organic carbon
The balance between photosynthetic organic carbon production and respiration controls atmospheric composition and climate
1
,
2
. The majority of organic carbon is respired back to carbon dioxide in the biosphere, but a small fraction escapes remineralization and is preserved over geological timescales
3
. By removing reduced carbon from Earth’s surface, this sequestration process promotes atmospheric oxygen accumulation
2
and carbon dioxide removal
1
. Two major mechanisms have been proposed to explain organic carbon preservation: selective preservation of biochemically unreactive compounds
4
,
5
and protection resulting from interactions with a mineral matrix
6
,
7
. Although both mechanisms can operate across a range of environments and timescales, their global relative importance on 1,000-year to 100,000-year timescales remains uncertain
4
. Here we present a global dataset of the distributions of organic carbon activation energy and corresponding radiocarbon ages in soils, sediments and dissolved organic carbon. We find that activation energy distributions broaden over time in all mineral-containing samples. This result requires increasing bond-strength diversity, consistent with the formation of organo-mineral bonds
8
but inconsistent with selective preservation. Radiocarbon ages further reveal that high-energy, mineral-bound organic carbon persists for millennia relative to low-energy, unbound organic carbon. Our results provide globally coherent evidence for the proposed
7
importance of mineral protection in promoting organic carbon preservation. We suggest that similar studies of bond-strength diversity in ancient sediments may reveal how and why organic carbon preservation—and thus atmospheric composition and climate—has varied over geological time.
Broadening activation energy distributions and increasing radiocarbon ages reveal the global importance of mineral protection in promoting organic carbon preservation.
Journal Article
Representing the function and sensitivity of coastal interfaces in Earth system models
Between the land and ocean, diverse coastal ecosystems transform, store, and transport material. Across these interfaces, the dynamic exchange of energy and matter is driven by hydrological and hydrodynamic processes such as river and groundwater discharge, tides, waves, and storms. These dynamics regulate ecosystem functions and Earth’s climate, yet global models lack representation of coastal processes and related feedbacks, impeding their predictions of coastal and global responses to change. Here, we assess existing coastal monitoring networks and regional models, existing challenges in these efforts, and recommend a path towards development of global models that more robustly reflect the coastal interface.
Coastal systems are hotspots of ecological, geochemical and economic activity, yet their dynamics are not accurately represented in global models. In this Review, Ward and colleagues assess the current state of coastal science and recommend approaches for including the coastal interface in predictive models.
Journal Article
Rivers across the Siberian Arctic unearth the patterns of carbon release from thawing permafrost
Climate warming is expected to mobilize northern permafrost and peat organic carbon (PP-C), yet magnitudes and system specifics of even current releases are poorly constrained. While part of the PP-C will degrade at point of thaw to CO₂ and CH₄ to directly amplify global warming, another part will enter the fluvial network, potentially providing a window to observe large-scale PP-C remobilization patterns. Here, we employ a decade-long, high-temporal resolution record of 14C in dissolved and particulate organic carbon (DOC and POC, respectively) to deconvolute PP-C release in the large drainage basins of rivers across Siberia: Ob, Yenisey, Lena, and Kolyma. The 14C-constrained estimate of export specifically from PP-C corresponds to only 17 ± 8% of total fluvial organic carbon and serves as a benchmark for monitoring changes to fluvial PP-C remobilization in a warming Arctic. Whereas DOC was dominated by recent organic carbon and poorly traced PP-C (12 ± 8%), POC carried a much stronger signature of PP-C (63 ± 10%) and represents the best window to detect spatial and temporal dynamics of PP-C release. Distinct seasonal patterns suggest that while DOC primarily stems from gradual leaching of surface soils, POC reflects abrupt collapse of deeper deposits. Higher dissolved PP-C export by Ob and Yenisey aligns with discontinuous permafrost that facilitates leaching, whereas higher particulate PP-C export by Lena and Kolyma likely echoes the thermokarst-induced collapse of Pleistocene deposits. Quantitative 14C-based fingerprinting of fluvial organic carbon thus provides an opportunity to elucidate large-scale dynamics of PP-C remobilization in response to Arctic warming.
Journal Article
Calcium-mediated stabilisation of soil organic carbon
Soils play an essential role in the global cycling of carbon and understanding the stabilisation mechanisms behind the preservation of soil organic carbon (SOC) pools is of globally recognised significance. Until recently, research into SOC stabilisation has predominantly focused on acidic soil environments and the interactions between SOC and aluminium (Al) or iron (Fe). The interactions between SOC and calcium (Ca) have typically received less attention, with fewer studies conducted in alkaline soils. Although it has widely been established that exchangeable Ca (CaExch) positively correlates with SOC concentration and its resistance to oxidation, the exact mechanisms behind this relationship remain largely unidentified. This synthesis paper critically assesses available evidence on the potential role of Ca in the stabilisation of SOC and identifies research topics that warrant further investigation. Contrary to the common view of the chemistry of base cations in soils, chemical modelling indicates that Ca²⁺ can readily exchange its hydration shell and create inner sphere complexes with organic functional groups. This review therefore argues that both inner- and outer-sphere bridging by Ca²⁺ can play an active role in the stabilisation of SOC. Calcium carbonate (CaCO₃) can influence occluded SOC stability through its role in the stabilisation of aggregates; however, it could also play an unaccounted role in the direct sorption and inclusion of SOC. Finally, this review highlights the importance of pH as a potential predictor of SOC stabilisation mechanisms mediated by Al- or Fe- to Ca, and their respective effects on SOC dynamics.
Journal Article
The Ecology of Soil Carbon: Pools, Vulnerabilities, and Biotic and Abiotic Controls
Soil organic matter (SOM) anchors global terrestrial productivity and food and fiber supply. SOM retains water and soil nutrients and stores more global carbon than do plants and the atmosphere combined. SOM is also decomposed by microbes, returning CO
2
, a greenhouse gas, to the atmosphere. Unfortunately, soil carbon stocks have been widely lost or degraded through land use changes and unsustainable forest and agricultural practices.
To understand its structure and function and to maintain and restore SOM, we need a better appreciation of soil organic carbon (SOC) saturation capacity and the retention of above- and belowground inputs in SOM. Our analysis suggests root inputs are approximately five times more likely than an equivalent mass of aboveground litter to be stabilized as SOM. Microbes, particularly fungi and bacteria, and soil faunal food webs strongly influence SOM decomposition at shallower depths, whereas mineral associations drive stabilization at depths greater than ∼30 cm. Global uncertainties in the amounts and locations of SOM include the extent of wetland, peatland, and permafrost systems and factors that constrain soil depths, such as shallow bedrock. In consideration of these uncertainties, we estimate global SOC stocks at depths of 2 and 3 m to be between 2,270 and 2,770 Pg, respectively, but could be as much as 700 Pg smaller. Sedimentary deposits deeper than 3 m likely contain >500 Pg of additional SOC. Soils hold the largest biogeochemically active terrestrial carbon pool on Earth and are critical for stabilizing atmospheric CO
2
concentrations. Nonetheless, global pressures on soils continue from changes in land management, including the need for increasing bioenergy and food production.
Journal Article
Global synthesis of temperature sensitivity of soil organic carbon decomposition
The response of soil organic carbon (SOC) decomposition to global warming is a potentially major source of uncertainty in climate prediction. However, the magnitude and direction of SOC cycle feedbacks under climate warming remain uncertain because of the knowledge gap about the global‐scale spatial pattern and temperature sensitivity (Q10) mechanism of SOC decomposition. Here, we collected data of Q10 and corresponding soil variables from 81 peer‐reviewed papers using laboratory incubation to explore how Q10 varied among different ecosystems at the global scale and whether labile and recalcitrant SOC pools had equal Q10 values. Q10 with a global average of 2.41 substantially varied among different ecosystems, ranging from the highest in cropland soils (2.76) and the lowest in wetland soils (1.84). Hump‐shaped correlations of Q10 values with the maximum at SOC = 190 g/kg and the minimum at clay = 37% were observed. However, the main influencing factors of Q10 differed among various ecosystems. Q10 values showed a clear decrease with increasing incubation temperature but no significant decrease above 25°C. In general, labile SOC was less sensitive than recalcitrant SOC to warming. Structural equation model analyses showed that total N and SOC accounted for 53% and 46%, respectively, of the variation in Q10 of labile SOC and recalcitrant SOC. This finding suggested that Q10 values of labile and recalcitrant SOC pools had different controlling factors. Our findings highlighted the importance of Q10’s variations in ecosystem types and the response of recalcitrant SOC to warming in predicting the soil C cycling and its feedback to climate change. Therefore, ecosystem type and difference in Q10 of labile and recalcitrant SOC should be considered to precisely predict the soil C dynamics under global warming. A plain language summary is available for this article. Plain Language Summary
Journal Article