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Mangrove wetlands are highly productive ecosystems in tropical and subtropical coastal zones, play crucial roles in water purification, biodiversity maintenance, and carbon sequestration. Recent years have seen the implementation of pond return initiatives, which have facilitated the gradual recovery of mangrove areas in China. However, the implications of these initiatives for soil aggregate stability, microbial community structure, and network interactions remain unclear. This study assesses the impacts of converting ponds to mangroves-both in natural and artificially restored settings-on soil aggregate stability and microbial networks at typical mangrove restoration sites along China's southeastern coast. Our observations confirmed our hypothesis that pond-to-mangrove conversions resulted in an increase in the proportion of large aggregates (>0.25 mm), improved soil aggregate structural stability, and increased carbon sequestration. However, mangrove recovery led to a decrease in the abundance and diversity of soil fungi communities. In terms of co-occurrence networks, naturally restored mangrove wetlands exhibited more nodes and edges. The naturally recovered mangrove wetlands demonstrated a higher level of community symbiosis compared to those that were manually restored. Conversely, bacterial networks showed a different pattern, with significant shifts in key taxa related to carbon sequestration functions. For instance, the proportion of bacterial Desulfobacterota and fungi Basidiomycota in natural recovery mangrove increased by 15.03 % and 7.82 %, respectively, compared with that in aquaculture ponds. Soil fungi and bacteria communities, as well as carbon sequestration by aggregates, were all positively correlated with soil total carbon content (P < 0.05). Both bacterial and fungal communities contributed to soil aggregate stability. Our study highlights the complex relationships between soil microbial communities, aggregate stability, and the carbon cycle before and after land-use changes. These findings underscore the potential benefits of restoring mangrove wetlands, as such efforts can enhance carbon storage capacity and significantly contribute to climate change mitigation., Competing Interests: Declaration of competing interest The authors declare no competing interests., (Copyright © 2024. Published by Elsevier B.V.)

Silicon (Si) biogeochemical cycling is beneficial for crop productivity and carbon (C) sequestration in agricultural ecosystem, thus offering a nonnegligible role in alleviating global warming and food crisis. Compared with other crops, rice plants have a greater quantity of phytolith production, because they are able to take up a lot of Si. However, it remains unclear on Si supply capacity of paddy soils across the world, general rice yield-increasing effect after Si fertilizer addition, and factors affecting phytolith production and potential of phytolith C sequestration in paddy fields. This study used a meta-analysis of >3500 data from 87 studies to investigate Si supply capacity of global paddy soils and elaborate the benefits of Si regarding rice productivity and phytolith C sequestration in paddy fields. Analytical results showed that the Si supply capacity of paddy soils was insufficient in the major rice producing countries/regions. Dealing with this predicament, Si fertilization was an effective strategy to supply plant-available Si to improve rice productivity. Our meta-analysis results further revealed that Si fertilization led to the average increasing rate of 36 % and 39 % in rice yield and biomass, which could reach up to 52 % and 46 % with the increasing doses of Si fertilizer, respectively. Especially, this strategy also improved the potential of phytolith C sequestration through the increased phytolith content and rice biomass, despite that this potential might have a decline in old paddy soils (≥ 7000 year) compared to in young paddy soils (≤ 1000 year) due to the slow migration and dissolution of phytoliths at millennial scale. Our findings thus indicate that a deep investigation on the benefits of Si in agroecosystem will further improve our understanding on regulating crop production and the potential of biogeochemical C sequestration within phytoliths in global cropland., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Phytoliths are silica biomineralization products within plants and have been considered as a promising material to sequester carbon (C). However, there is considerable uncertainty and controversy regarding the C content in phytoliths due to the lack of detailed information on variation of C under different extraction procedures. Herein, we established a series of batch digestion experimental procedures coupled with analyses of phytoliths using Scanning Electron Microscopy and Energy-Dispersive X-ray Spectroscopy to divide phytoliths into three fractions. We then reported an approach for standardizing across hundreds of values found in the literature. Combining this standardized approach with C contents in phytoliths extracted from different digestion degrees, we revaluated the potential production rates of phytolith-occluded carbon (PhytOC) input globally in rice paddy fields. The results showed that the C content in recovered phytoliths exhibited a significantly fitting exponential relationship (p < 0.01) with digestion degrees and decreased from 30 to 75 g kg -1 under moderate digestion to <5 g kg -1 under over digestion. On a global scale, the production of total PhytOC in the world paddy fields reached up to (2.71 ± 0.85) × 10 6 t year -1 . Therein, the contribution of sub-stable PhytOC fraction, stable PhytOC fraction, and recalcitrant PhytOC fraction was 63 %, 28 %, and 9 %, respectively. Our results imply that the estimation of phytolith C sequestration potential across the global paddy fields is associated with specific PhytOC fractions. Therefore, further determining the storage time limits of these specific PhytOC fractions after returning to soil will be vital for predicting terrestrial biogeochemical C sequestration potentials of phytoliths., Competing Interests: Declaration of competing interest All authors declare no conflict of competing interest., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Phytolith carbon (C) sequestration plays a key role in mitigating global climate change at a centennial to millennial time scale. However, previous estimates of phytolith-occluded carbon (PhytOC) storage and potential in China's grasslands have large uncertainties mainly due to multiple data sources. This contributes to the uncertainty in predicting long-term C sequestration in terrestrial ecosystems using Earth System Models. In this study, we carried out an intensive field investigation (79 sites, 237 soil profiles [0-100 cm], and 61 vegetation assessments) to quantify PhytOC storage in China's grasslands and to better explore the biogeographical patterns and influencing factors. Generally, PhytOC production flux and soil PhytOC density in both the Tibetan Plateau and the Inner Mongolian Plateau had a decreasing trend from the Northeast to the Southwest. The aboveground PhytOC production rate in China's grassland was 0.48 × 10 6 t CO 2 a -1 , and the soil PhytOC storage was 383 × 10 6 t CO 2 . About 45% of soil PhytOC was stored in the deep soil layers (50-100 cm), highlighting the importance of deep soil layers for C stock assessments. Importantly, the Tibetan Plateau had the greatest contribution (more than 70%) to the PhytOC storage in China's grasslands. The results of multiple regression analysis indicated that altitude and soil texture significantly influenced the spatial distribution of soil PhytOC, explaining 78.1% of the total variation. Soil phytolith turnover time in China's grasslands was mainly controlled by climatic conditions, with the turnover time on the Tibetan Plateau being significantly longer than that on the Inner Mongolian Plateau. Our results offer more accurate estimates of the potential for phytolith C sequestration from ecological restoration projects in degraded grassland ecosystems. These estimates are essential to parameterizing and validating global C models., (© 2022 John Wiley & Sons Ltd.)

Terrestrial biogeochemical carbon (C) sequestration is coupled with the biogeochemical silicon (Si) cycle through mechanisms such as phytolith C sequestration, but the size and distribution of the phytolith C sink remain unclear. Here, we estimate phytolith C sequestration in global terrestrial biomes. We used biome data including productivity, phytolith and silica contents, and the phytolith stability factor to preliminarily determine the size and distribution of the phytolith C sink in global terrestrial biomes. Total phytolith C sequestration in global terrestrial biomes is 156.7±91.6TgCO 2 yr -1 . Grassland (40%), cropland (35%), and forest (20%) biomes are the dominant producers of phytolith-based carbon; geographically, the main contributors are Asia (31%), Africa (24%), and South America (17%). Practices such as bamboo afforestation/reforestation and grassland recovery for economic and ecological purposes could theoretically double the above phytolith C sink. The potential terrestrial phytolith C sequestration during 2000-2099 under such practices would be 15.7-40.5PgCO 2 , equivalent in magnitude to the C sequestration of oceanic diatoms in sediments and through silicate weathering. Phytolith C sequestration contributes vitally to the global C cycle, hence, it is essential to incorporate plant-soil silica cycling in biogeochemical C cycle models., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Phytolith-occluded carbon (PhytOC) is a stable carbon (C) fraction that has effects on long-term global C balance. Here, we report the phytolith and PhytOC accumulation in moso bamboo leaves developed on four types of parent materials. The results show that PhytOC content of moso bamboo varies with parent material in the order of granodiorite (2.0 g kg(-1)) > granite (1.6 g kg(-1)) > basalt (1.3 g kg(-1)) > shale (0.7 g kg(-1)). PhytOC production flux of moso bamboo on four types of parent materials varies significantly from 1.0 to 64.8 kg CO₂ ha(-1) yr(-1), thus a net 4.7 × 10(6) -310.8 × 10(6) kg CO₂ yr(-1) would be sequestered by moso bamboo phytoliths in China. The phytolith C sequestration rate in moso bamboo of China will continue to increase in the following decades due to nationwide bamboo afforestation/reforestation, demonstrating the potential of bamboo in regulating terrestrial C balance. Management practices such as afforestation of bamboo in granodiorite area and granodiorite powder amendment may further enhance phytolith C sequestration through bamboo plants.

The occlusion of carbon (C) by phytoliths, the recalcitrant silicified structures deposited within plant tissues, is an important persistent C sink mechanism for croplands and other grass-dominated ecosystems. By constructing a silica content-phytolith content transfer function and calculating the magnitude of phytolith C sink in global croplands with relevant crop production data, this study investigated the present and potential of phytolith C sinks in global croplands and its contribution to the cropland C balance to understand the cropland C cycle and enhance long-term C sequestration in croplands. Our results indicate that the phytolith sink annually sequesters 26.35 ± 10.22 Tg of carbon dioxide (CO2) and may contribute 40 ± 18% of the global net cropland soil C sink for 1961-2100. Rice (25%), wheat (19%) and maize (23%) are the dominant contributing crop species to this phytolith C sink. Continentally, the main contributors are Asia (49%), North America (17%) and Europe (16%). The sink has tripled since 1961, mainly due to fertilizer application and irrigation. Cropland phytolith C sinks may be further enhanced by adopting cropland management practices such as optimization of cropping system and fertilization.

Coastal wetlands play a vital role in carbon (C) sequestration, named 'blue carbon'. The review aims to disentangle the processes and influencing factors, including elevated atmospheric CO 2 , global climate warming, sea level rise and anthropogenic activities. Firstly, we provided an overview of C processes, including input, output, and deposition, in coastal wetlands. We then summarized the impacts of different factors on C processes by modifying soil physicochemical properties, plant growth, vegetation type, and microbial community composition. Vegetation composition was a major contributor to C inputs, and C outputs was mainly controlled by microbial decomposition. Increased atmospheric CO 2 concentration and associated climate warming often enhanced vegetation growth, while climate warming also promoted soil C decomposition. As a result, C storage could increase under mild warming conditions in the short-term, but decrease in the long-term as the severity of warming intensifies. Elevated salinity, caused by sea level rise, can be harmful to plant growth and inhibit organic C decomposition because of the reduced biomass and the weakened metabolic capacity of microorganisms. Most of human activities, such as reclamation, can lead to less C input and more C output, resulting in decreased C storage in coastal wetlands. Additionally, we also illustrate various coastal wetland restoration methods aimed at enhancing C sequestration, including legal frameworks, scientific theories, vegetation management, hydrological restoration, and other relevant constructions. Vegetation management could benefit plant growth and enhance C input effectively, and hydrological restoration can maintain the harmonious development of coastal wetland ecosystems. Other constructions, including breakwater, spillway, and dredged material, could protect coastal wetlands, especially facing sea level rise. This review offers valuable theoretical support and scientific references for the sustainable development and management of coastal wetlands in a changing climate. • Carbon sequestration in coastal wetlands is driven by both natural and human factors. • Warming has negative influence on C storage under serious conditions in the long-term. • The effects of N input on C cycle vary under different N forms and duration. • Vegetation management benefits plant growth and enhances C input effectively. • Protecting coastal wetlands will offer new opportunities to raise C sequestration. [ABSTRACT FROM AUTHOR]

Abstract The terrestrial biogeochemical silicon (Si) cycle may significantly influence the stabilization of soil organic carbon (SOC), and thus plays an important role in regulating the global carbon (C) balance and climate change. Processes involved in Si-enhanced SOC stability at a decadal or centennial scale include protection of SOC through amorphous Si and interactions of Si-iron and Si-aluminum. Strategic manipulation of the Si cycle in terrestrial ecosystems offers a new opportunity to enhance soil C sequestration. Rock powder amendment, establishment of Si-rich plant buffer strips and innovative management practices that return Si-rich biomass materials to soil can be implemented as strategies to enhance soil C sequestration through regulating the terrestrial Si cycle. However, quantifying (i) the contribution of different processes to the enhancement of soil dissolved Si and secondary Si minerals, (ii) the relative importance of different SOC stabilization mechanisms, and (iii) the potential and cost of different measures has not been attempted. [ABSTRACT FROM AUTHOR]

Keywords: phytolith; silica; silicon; biomineralisation; biogeochemistry; carbon sequestration EN phytolith silica silicon biomineralisation biogeochemistry carbon sequestration 1 3 3 04/22/20 20200417 NES 200417 Interest in phytoliths has grown significantly in recent years. Since Ma et al. ([5]) first described a Si transporter in the rice root, considerable interest was raised in establishing the molecular basis of plant Si uptake. So it is quite possible that the work of Zancajo et al. which suggests that bilobate silica cells in sorghum leaves have a different type of occluded organic matter compared with prickles and long cells may yet prove important when we consider carbon sequestration and dating. Phytolith, silica, silicon, biomineralisation, biogeochemistry, carbon sequestration. [Extracted from the article]

Carbon (C) occlusion within phytoliths (PhytOC) has a significant potential for long-term C sequestration in forest ecosystems. To unravel the role of forest composition on phytolith production, soil phytolith distribution, and phytolith C sequestration in soils, we investigated community composition and examined phytoliths and PhytOC of mature leaves or needles of dominant trees and understory herbs, as well as soil profiles (50 cm depth) within Quercus , Betula , Larix and Pinus forest ecosystems of northern China. Results showed that herb layers contributed 72%, 52%, 40%, and 5% to the flux of phytolith production within Betula forest (18.0 ± 1.26 kg ha − 1 yr − 1 ), Quercus forest (28.5 ± 0.77 kg ha − 1 yr − 1 ), Larix forest (37.7 ± 1.80 kg ha − 1 yr − 1 ) and Pinus forest (16.9 ± 0.30 kg ha − 1 yr − 1 ), respectively. The distribution pattern of soil phytoliths from topsoil to subsoil could be classified into three types: significantly decreasing pattern ( Betula forest and Quercus forest), non-significantly decreasing pattern ( Larix forest), and initially increasing and then decreasing pattern ( Pinus forest). Within 0–50 cm soil depth, the PhytOC storage of Betula forest, Quercus forest, Larix forest and Pinus forest were 0.29 ± 0.02 t ha − 1 , 0.67 ± 0.03 t ha − 1 , 0.46 ± 0.03 t ha − 1 and 0.37 ± 0.02 t ha − 1 , respectively. Moreover, the soil PhytOC turnover times of these four forest types were estimated to be 537,503,363 and 560 year, respectively, which were at least 8–20 times slower than soil organic carbon contributing to climate change mitigation. Overall, our findings indicate that composition of the forest community controls the production flux of phytoliths and the distribution of soil phytoliths, and influences the biogenic silica and its coupled carbon cycles. [ABSTRACT FROM AUTHOR]

Grasslands play an important role in the terrestrial biogeochemical carbon (C) cycle and partly mitigate climate change through C occlusion within phytoliths. Grassland degradation has a significant influence on the coupled biogeochemical cycles of C and silicon in the Inner Mongolian steppe of China, but there are few reports about the impact of grassland degradation on phytolith C sequestration in the steppe, the main grassland in northern China. Twelve sampling sites were chosen in the Xilingol League. Soil samples (0–50 cm) were collected from grasslands of four different degradation degrees to investigate the impact of grassland degradation on the soil phytolith and phytolith-occluded C (PhytOC) accumulation using a mass-balance approach. Soil phytolith storages were 12.97 ± 2.15, 15.90 ± 0.65, 14.35 ± 0.79 and 13.22 ± 1.07 t ha − 1 in non-degraded, lightly degraded, moderately degraded and seriously degraded grasslands, respectively. The corresponding storages of soil PhytOC were 0.11 ± 0.02, 0.16 ± 0.02, 0.12 ± 0.01 and 0.07 ± 0.01 t ha − 1 , respectively. The observed significant differences in soil phytoliths and PhytOC among grasslands of different degradation degrees indicate that grassland degradation influenced the phytolith and PhytOC accumulation in grassland soils. Grazing and harvesting are likely the major factors affecting soil phytolith and PhytOC storages through reducing the litterfall returning fluxes. Our preliminary findings imply that grassland restoration could be a promising way to increase long-term phytolith C sequestration through maximizing plant PhytOC production fluxes and soil PhytOC accumulation in degraded grasslands. [ABSTRACT FROM AUTHOR]

Carbon sequestered in phytoliths, the silicified features of plants, may accumulate in soils and sediments for several hundreds to thousands of years depending mainly on the morphology and chemical composition of phytoliths and environmental conditions. Phytolith carbon sequestration is thought to be one of the key biogeochemical carbon sequestration mechanisms. This review summarizes the current state of understanding of occurrence, turnover and carbon sequestration potential of phytoliths in terrestrial ecosystems. The accumulation rate of phytoliths in soils is controlled not only by plant litter inputs but also by geochemical stability and turnover of phytoliths. Most of the organic carbon in phytoliths is from photosynthesis of atmospheric carbon dioxide (CO 2 ) during formation of phytoliths. Phytolith carbon sequestration in terrestrial ecosystems is a promising biogeochemical carbon sequestration mechanism and may contribute to the mitigation of global climate warming. Further questions such as the turnover of phytoliths with different properties and under different environmental conditions, the relative contribution of different ecosystems to the global terrestrial phytolith carbon sequestration, and the cost and potential of each management measure to enhance phytolith carbon sequestration should be investigated. [ABSTRACT FROM AUTHOR]

Phytolith carbon (C) sequestration has been identified to be a relatively stable and efficacious mechanism to securely reduce atmospheric carbon dioxide (CO2) concentration. As a fast-growing and Si-accumulating plant, moso bamboo (Phyllostachys pubescens) can produce large quantities of phytolith-occluded carbon (PhytOC). In this study, we sampled the mature leaves, leaf litter and soils from moso bamboo stands located in Qingshan (30°13′N, 119°47′E; Lin'an, China) to study topographic effects on phytolith and PhytOC production in moso bamboo ecosystems. Our results showed that the phytolith contents of mature leaves and leaf litter in moso bamboo stand decreased with the slope steepness as follows: 2–5° > 5–15° > 15–35°, and showed an increasing tendency with the slope position as follows: lower slope < middle slope < upper slope. The PhytOC production flux also showed the same trend as that for phytoliths and ranged from 10.32 to 16.16 kg CO2ha−1year−1. Our data indicate that topography, especially slope position and slope steepness, should be considered as some key factors to enhance bamboo phytolith C sequestration during future bamboo afforestation and reforestation. [ABSTRACT FROM PUBLISHER]

Purpose: Occlusion of carbon in phytoliths is an important biogeochemical carbon sequestration mechanism and plays a significant role in the global biogeochemical carbon cycle and atmospheric carbon dioxide (CO) concentration regulation at a millennial scale. However, few studies have focused on the storage of phytolith and phytolith-occluded carbon (PhytOC) in subtropical forest soils. Materials and methods: Soil profiles with 100-cm depth were sampled from subtropical bamboo forest, fir forest, and chestnut forest in China to investigate the variation of phytoliths and PhytOC storage in the soil profiles based on amass-balance assessment. Results and discussion: The storage of phytoliths in the top 100 cm of the bamboo forest soil (198.13 ± 25.08 t ha) was much higher than that in the fir forest (146.76 ± 4.53 t ha) and chestnut forest (170.87 ± 9.59 t ha). Similarly, the storage of PhytOC in the bamboo forest soil (3.91 ± 0.64 t ha) was much higher than that in the fir forest soil (1.18 ± 0.22 t ha) and chestnut forest soil (2.67 ± 0.23 t ha). The PhytOC percentage in the soil organic carbon pool increased with soil depth and was the highest (4.29 %) in the bamboo forest soil. Our study demonstrated that PhytOC in soil was significantly influenced by forest type and the bamboo forest ecosystem contributed more significantly to phytolith carbon sequestration than other forest ecosystems. Conclusions: Different forest types have a significant influence on the soil PhytOC storage. Optimization of bamboo afforestation/reforestation in future forest management plans may significantly enhance the biogeochemical carbon sink in the following centuries. [ABSTRACT FROM AUTHOR]

Global agricultural ecosystems, the largest biospheric sources of atmospheric carbon dioxide (CO 2 ), may turn into considerable net carbon (C) sinks through adopting management strategies advised by research. As C sequestration is usually coupled with the silicon (Si) cycle, strategic manipulation of the biogeochemical Si cycle in agricultural ecosystems offers a not yet fully explored possibility to enhance C sequestration. This review summarizes current knowledge of C sequestration coupled with the Si cycle and its management in agricultural ecosystems. Carbon sequestration is coupled with the Si cycle through many processes including dynamics of phytoliths and aggregates, and silicate weathering at different temporal and spatial scales. Cultivation of deep rooting crops, erosion mitigation with buffer strips, fertilization of Si-rich materials are some of the potential management strategies to increase both crop production and C sequestration coupled with the Si cycle. Further questions such as identifying the controlling factors of bioavailable Si pools and C sequestration, and quantifying the cost-efficiency of different management strategies to manipulate the Si cycle with the aim to enhance C sequestration should be investigated. [ABSTRACT FROM AUTHOR]

Highlights: [•] A recent found persistent carbon sink is C occluded within plant phytoliths. [•] The Chinese cropland phytolith C sink contributes 18% of world's croplands. [•] The predominant phytolith producing crop species were rice, wheat and corn. [•] The sink has doubled since 1978 due to fertilizer application and irrigation. [•] Management practices may further enhance the cropland phytolith C sink. [ABSTRACT FROM AUTHOR]

Highlights: [•] Reed PhytOC content depends on phytolith content and carbon content of phytoliths. [•] The above-ground production rate of PhytOC is about 2.01×108 gCO2 a−1. [•] Reed has a major role in sequestrating CO2 through formation of PhytOC. [ABSTRACT FROM AUTHOR]

Among the most promising approaches of long-term atmospheric CO2 sequestration is terrestrial biogeochemical carbon sequestration. One of the most promising terrestrial biogeochemical carbon sequestration mechanisms is the occlusion of carbon within phytoliths, the silicified features that deposit within plant tissues. Using phytolith content-biogenic silica content transfer function obtained from our investigation, in combination with published silica content and above-ground net primary productivity ( ANPP) data of China's grasslands, we estimated the production of phytoliths and phytolith-occluded carbon ( PhytOC) in grasslands. The results show that the average above-ground phytolith production rates of China's grasslands (10.9 106 t yr−1 or 1.45% of world grasslands) are much lower than those of other grasslands (e.g. North American nonwoody grasslands) mainly because of much lower ANPP. Assuming a median content of PhytOC of 1.5%, the average above-ground PhytOC production rates of China's grasslands and world grasslands are estimated to be 0.6 106 t CO2 yr−1 and 41.4 106 t CO2 yr−1, respectively. The management of grasslands to maximize ANPP has the potential to result in considerable quantities of phytoliths and securely bio-sequestered carbon. [ABSTRACT FROM AUTHOR]

Abstract: The coupled terrestrial biogeochemical cycles of silicon (Si) and carbon (C) that are driven by plant action play a crucial role in the regulation of atmospheric CO2. Generally, the processes involved in the coupled cycles of Si and C include plant-enhanced silicate weathering, phytolith formation and solubilization, secondary aluminosilicate accumulation, phytolith occlusion of C as well as physico-chemical protection of organic C in soils. There is increasing evidence of biological pumping of Si in terrestrial ecosystems, suggesting that complex feedbacks exist amongst the processes within the coupled Si and C cycles. Recent advances in the coupled Si and C cycles offer promising new possibilities for enhancing atmospheric CO2 sequestration. Organic mulching, rock powder amendment, cultivating Si-accumulating plants and partial plant harvesting are potential measures that may allow for long-term manipulation and biogeochemical sequestration of atmospheric CO2 in soil–plant systems. [Copyright &y& Elsevier]

Among the most promising approaches of long-term atmospheric CO2 sequestration is terrestrial biogeochemical carbon sequestration. One of the most promising terrestrial biogeochemical carbon sequestration mechanisms is the occlusion of carbon within phytoliths, the silicified features that deposit within plant tissues. Using phytolith content-biogenic silica content transfer function obtained from our investigation, in combination with published silica content and above-ground net primary productivity ( ANPP) data of China's grasslands, we estimated the production of phytoliths and phytolith-occluded carbon ( PhytOC) in grasslands. The results show that the average above-ground phytolith production rates of China's grasslands (10.9 106 t yr−1 or 1.45% of world grasslands) are much lower than those of other grasslands (e.g. North American nonwoody grasslands) mainly because of much lower ANPP. Assuming a median content of PhytOC of 1.5%, the average above-ground PhytOC production rates of China's grasslands and world grasslands are estimated to be 0.6 106 t CO2 yr−1 and 41.4 106 t CO2 yr−1, respectively. The management of grasslands to maximize ANPP has the potential to result in considerable quantities of phytoliths and securely bio-sequestered carbon. [ABSTRACT FROM AUTHOR]

• A paired waterlogging-control system was established to evaluate effects of sea‐level rise on BSi and BSiOC accumulations. • Sea‐level rise significantly reduced BSi and BSiOC densities, particularly in the salt marsh dominated by the Phragmites australis. • Although sea‐level rise increased SOC content, it generally decreased soil BSiOC content and its contribution to total SOC. • The depleted BSi and BSiOC stocks was attributed to increased anaerobiosis, higher salinity and pH, and higher soil erosion. The fate of soil biogenic silica (BSi) in coastal salt marshes is of global importance because of its role in providing both available silicon (Si) for the growth of plants and diatoms and in sequestering carbon (C) (blue C) in soils and sediments. However, the accumulation of BSi and BSi-occluded C (BSiOC) under different vegetation habitats in coastal ecosystems, particularly in response to relative sea‐level rise (RSLR), remains poorly understood. Here we established a paired waterlogging-control system and collected the soil samples under both waterlogged and non-waterlogged conditions from three vegetation habitats (single Phragmites australis , a mixture of P. australis and Suaeda salsa , and single S. salsa) corresponding to a gradient of distance from the coastline in three independent salt marshes. Our findings indicated that RSLR decreased average BSi content, especially in the 0–20 cm soil layer of the single P. australis and the mixed P. australis and S. salsa community. Although RSLR increased soil organic C (SOC) content, it generally decreased soil BSiOC content and its contribution to SOC. Consequently, RSLR resulted in lower soil BSi and BSiOC densities, particularly in the salt marsh dominated by the Si accumulator P. australis. Here, BSi and BSiOC densities at depths of 0–80 cm decreased by an average of 19% and 18% following waterlogging, respectively. The BSi pool was dominated by phytoliths in non-waterlogged soils, while both diatoms and phytoliths were present in soils subjected to RSLR. Soil physicochemical properties including SOC, electrical conductivity and dissolved Si were influenced by RSLR. These factors, along with erosion were suggested as key influencers for BSi and its C sequestration in coastal salt marshes. Our results provide a scientific basis for elucidating biogeochemical Si cycles and predicting changes in BSiOC sequestration to optimize its storage. [ABSTRACT FROM AUTHOR]

The publisher regrets that this article has been temporarily removed. A replacement will appear as soon as possible in which the reason for the removal of the article will be specified, or the article will be reinstated. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy . [ABSTRACT FROM AUTHOR]

• ~98% of the total C from black shales was recalcitrant C fraction. • The δ13C value was higher in SOC compared to the ROC fraction. • The ROC accounted for ~60% of the SOC pool in terrestrial ecosystems. • Paddy soils have a higher potential for SOC storage than forest soils. • LOC, Semi-LOC, and ROC content are significantly correlated with SOC content. Black shales are characterized by a high content of organic carbon (C). Few studies have focused on the influence of land use on soil organic C (SOC) fractions from soils derived from black shale (black shale soils). The objective of this study was to elucidate the influence of land use on SOC fractions in black shale soils combining chemical determination and stable C isotope analysis techniques. Herein, we determined labile organic C (LOC), semi-labile organic C (Semi-LOC), and recalcitrant organic C (ROC) fractions in various depths of soils in paddy fields (0–70 cm) and forests (0–120 cm) from black shale distribution region in Hunan province, China, and then investigated δ13C values of these soils. Results showed that the contents of LOC, Semi-LOC, and ROC in paddy soils (1.63–7.35 g kg−1, 0.35–1.21 g kg−1, and 3.75–14.8 g kg−1, respectively) and forest soils (0.73–4.94 g kg−1, 0.12–0.89 g kg−1, and 1.44–8.96 g kg–1, respectively) are significantly decreased with increasing depth. The contribution made by LOC to SOC in paddy soils was significantly lower than that in forest soils, while the contribution made by ROC to SOC was significantly higher in paddy soils than that in forest soils. In these two land uses, the δ13C values were higher in SOC compared to the ROC fraction, while the δ13C values were close in the ROC fraction below 20 cm soil depth. Our study indicated that i) new C is mainly limited to the surface soil layer (0–10 cm) in forests, while it can be leached along the soil profiles in paddy fields; ii) the estimated ROC pool is ~900 Pg within the 0–100 cm soil layer in terrestrial ecosystems, which should better represent the ability of soil C sequestration. [ABSTRACT FROM AUTHOR]

Carbon (C) present in lake sediments is an important global sink for CO 2 ; however, an in-depth understanding of the impact of climate variability and the associated changes in vegetation on sediment C dynamics is still lacking. A total of 13 lakes were studied to quantify the influence of climate and vegetation on the reconstructed Holocene C accumulation rate (CAR) in lake sediments of the modern East Asian monsoonal margin. The corresponding paleoclimate information was assessed, including the temperature (30–90°N in the Northern Hemisphere) and precipitation (indicated by the δ18O of the Sanbao, Dongge, and Hulu caves). The Holocene vegetation conditions were inferred by pollen records, including arboreal pollen/non-arboreal pollen and pollen percentages. The results showed that the peak CAR occurred during the mid-Holocene, coinciding with the strongest period of the East Asian summer monsoon and expansion of forests. Lakes in the temperate steppe (TS) regions had a mean CAR of 13.41 ± 0.88 g C m−2 yr−1, which was significantly greater than the CARs of temperate desert (TD) and highland meadow/steppe (HMS; 6.76 ± 0.29 and 7.39 ± 0.73 g C m−2 yr−1, respectively). The major influencing factor for the TS sub-region was vegetation dynamics, especially the proportion of arboreal vegetation, while temperature and vegetation coverage were more important for the HMS. These findings indicate that C accumulation in lake sediments is linked with climate and vegetation changes over long timescales; however, there was notable spatial heterogeneity in the CARs, such as opposing temporal changes and different major influencing factors among the three sub-regions during the mid-Holocene. Aridification and forest loss would decrease C storage. However, prediction of C accumulation remains difficult because of the spatial heterogeneity in CARs and the interaction between the CAR and various factors under future climate change conditions. Unlabelled Image • Climate and vegetation are important factors controlling the CAR. • Three sub-regions have different temporal trends and factors influencing the CAR. • Reduced future C storage is projected for lakes in the East Asian monsoonal margin. • Lower C storage is likely to be driven by the loss of vegetation and coverage. [ABSTRACT FROM AUTHOR]