Search

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 × 106 t CO2 a–1, and the soil PhytOC storage was 383 × 106 t CO2. 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.

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 × 106 t CO2 a–1, and the soil PhytOC storage was 383 × 106 t CO2. 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.

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 x 10(6) t CO2 a(-1), and the soil PhytOC storage was 383 x 10(6) t CO2. 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.

Returning crop straw into the soil is an important practice to balance biogenic and bioavailable silicon (Si) pool in paddy, which is crucial for the healthy growth of rice. However, owing to little knowledge about soil microbial communities responsible for straw degradation, how straw return affects Si bioavailability, its uptake, and rice yield remains elusive. Herein, we investigate the change of soil Si fractions and microbial community in a 39-year-old paddy field amended by a long-term straw return. Results show that rice straw return significantly increased soil bioavailable Si and rice yield from 29.9% to 61.6% and from 14.5% to 23.6%, respectively, when compared to NPK fertilization alone. Straw return significantly altered soil microbial community abundance. Acidobacteria was positively and significantly related to amorphous Si, while Rokubacteria at phylum level, Deltaproteobacteria, and Holophagae at class level was negatively and significantly related to organic matter adsorbed and Fe/Mn-oxide-combined Si in soils. Redundancy analysis of their correlations further demonstrated that Si status significantly explained 12% of soil bacterial community variation. These findings suggest that soil bacteria community and diversity interact with Si mobility by altering its transformation, thus resulting in the balance of various nutrient sources to drive biological Si cycle in agroecosystem.

Soil amendments of black bone (BB), biochar (BC), silicon fertilizer (SI), and leaf fertilizer (LF) play vital roles in decreasing cadmium (Cd) availability, thereby supporting healthy plant growth and food security in agroecosystems. However, the effect of their additions on soil microbial community and the resulting soil Cd bioavailability, plant Cd uptake and health growth are still unknown. Therefore, in this study, BB, BC, SI, and LF were selected to evaluate Cd amelioration in wheat grown in Cd-contaminated soils. The results showed that relative to the control, all amendments significantly decreased both soil Cd bioavailability and its uptake in plant tissues, promoting healthy wheat growth and yield. This induced-decrease effect in seeds was the most obvious, wherein the effect was the highest in SI (52.54%), followed by LF (43.31%), and lowest in BC (35.24%) and BB (31.98%). Moreover, the induced decrease in soil Cd bioavailability was the highest in SI (29.56%), followed by BC (28.85%), lowest in LF (17.55%), and BB (15.30%). The significant effect in SI likely resulted from a significant increase in both the soil bioavailable Si and microbial community (Acidobacteria and Thaumarchaeota), which significantly decreased soil Cd bioavailability towards plant roots. In particular, a co-occurrence network analysis indicated that soil microbes played a substantial role in wheat yield under Si amendment. Therefore, supplying Si alters the soil microbial community, positively and significantly interacting with soil bioavailable Si and decreasing Cd bioavailability in soils, thereby sustaining healthy crop development and food quality.

Phytolith-occluded carbon (PhytOC) is resistant to decomposition and, if crop residue biomass is incorporated into soil, has a significant potential for long-term soil carbon sequestration. However, the magnitude and spatial distribution of rice straw PhytOC sequestration remain unclear. Here, we used 279 samplings from nine provinces across China to establish the relationship between soil nutrients availability and rice straw phytoliths concentra-tion, thereby predicting annual PhytOC sequestration of Chinese rice systems. The results suggest that rice straw phytoliths sequester about 0.26 Tg CO2 per yr (8.7 kg CO2 ha(-1) yr(-1)) in China. Great variability of PhytOC exists across the region depending on rice variety. If rice varieties that occluded little PhytOC were replaced by ones with the highest PhytOC concentration, the sequestration rate might be increased to 0.83 Tg CO2 yr(-1) (27.7 kg CO2 ha(-1) yr(-1)). The distribution pattern shows that 51% of rice straw PhytOC sequestration can be attributed to the Middle-Lower Yangtze Plain due to its vast rice production. PhytOC sequestration is a crucial mechanism of global biogeochemical carbon sink, and practices such as appropriate fertilization application and selection of rice varieties with higher PhytOC concentration may alleviate climate warming.

Background and aims Silicon (Si) deficiency is a major constraint on rice production. The objective of this study was to evaluate the long-term influence of phytolith-rich straw return and groundwater table management on labile Si fractions in paddy soil and subsequent plant Si uptake. Methods A field experiment was conducted over 36 years in subtropical China with different application doses of phytolith-rich straw and a groundwater table of either 20 or 80 cm. An optimized sequential chemical extraction procedure allowed us to determine labile Si fractions, represented by CaCl2-Si, Acetic-Si, H2O2-Si, Oxalate-Si, and Na2CO3-Si. Additional analyses included the determination of amorphous silica particles in soil, phytoliths in supplied straw, Si in planted rice straw, and the dissolution rate of phytoliths extracted from supplied straw. Results Long-term application of phytolith-rich straw significantly increased the H2O2-Si and Na2CO3-Si contents. The CaCl2-Si (5.21-7.91 mg kg(- 1)), H2O2-Si (50.0-72.4 mg kg(- 1)) and Na2CO3-Si (3.33-4.60 g kg(- 1)) contents were positively correlated with soil organic carbon. The Si content (13.6-28.9 g kg(-& x200d;1)) in planted rice straw significantly (p < 0.05) increased with the application dose of phytolith-rich straw under both groundwater tables. This effect was significantly (p < 0.05) greater under 80 cm groundwater table than under 20 cm groundwater table for matching straw amendments. Conclusions This study indicates that long-term application of phytolith-rich straw and groundwater management significantly increase soil Si bioavailability by promoting accumulation of organic matter and phytoliths, and enhancing the soil-plant Si cycle.

Crop harvesting and residue removal from croplands often result in imbalanced biogeochemical cycles of carbon and nutrients in croplands, putting forward an austere challenge to sustainable agricultural production. As a beneficial element, silicon(Si) has multiple eco-physiological functions, which could help crops to acclimatize their unfavorable habitats. Although many studies have reported that the application of Si can alleviate multiple abiotic and biotic stresses and increase biomass accumulation, the effects of Si on carbon immobilization and nutrients uptake into plants in croplands have not yet been explored. This review focused on Si-associated regulation of plant carbon accumulation, lignin biosynthesis, and nutrients uptake, which are important for biogeochemical cycles of carbon and nutrients in croplands. The tradeoff analysis the supply of bioavailable Si can enhance plant net photosynthetic rate and biomass carbon production (especially root biomass input to soil organic carbon pool), but reduce shoot lignin biosynthesis. Besides, the application of Si could improve uptake of most nutrients under deficient conditions, but restricts excess uptake when they are supplied in surplus amounts. Nevertheless, Si application to crops may enhance the uptake of nitrogen and iron when they are supplied in deficient to luxurious amounts, while potassium uptake enhanced by Si application is often involved in alleviating salt stress and inhibiting excess sodium uptake in plants. More importantly, the amount of Si accumulated in plant positively correlates with nutrients release during the decay of crop biomass, but negatively correlates with straw decomposability due to the reduced lignin synthesis. The Si-mediated plant growth and litter decomposition collectively suggest that Si cycling in croplands plays important roles in biogeochemical cycles of carbon and nutrients. Hence, scientific Si management in croplands will be helpful for maintaining sustainable dev

Crop harvesting and residue removal from croplands often result in imbalanced biogeochemical cycles of carbon and nutrients in croplands, putting forward an austere challenge to sustainable agricultural production. As a beneficial element, silicon(Si) has multiple eco-physiological functions, which could help crops to acclimatize their unfavorable habitats. Although many studies have reported that the application of Si can alleviate multiple abiotic and biotic stresses and increase biomass accumulation, the effects of Si on carbon immobilization and nutrients uptake into plants in croplands have not yet been explored. This review focused on Si-associated regulation of plant carbon accumulation, lignin biosynthesis, and nutrients uptake, which are important for biogeochemical cycles of carbon and nutrients in croplands. The tradeoff analysis the supply of bioavailable Si can enhance plant net photosynthetic rate and biomass carbon production (especially root biomass input to soil organic carbon pool), but reduce shoot lignin biosynthesis. Besides, the application of Si could improve uptake of most nutrients under deficient conditions, but restricts excess uptake when they are supplied in surplus amounts. Nevertheless, Si application to crops may enhance the uptake of nitrogen and iron when they are supplied in deficient to luxurious amounts, while potassium uptake enhanced by Si application is often involved in alleviating salt stress and inhibiting excess sodium uptake in plants. More importantly, the amount of Si accumulated in plant positively correlates with nutrients release during the decay of crop biomass, but negatively correlates with straw decomposability due to the reduced lignin synthesis. The Si-mediated plant growth and litter decomposition collectively suggest that Si cycling in croplands plays important roles in biogeochemical cycles of carbon and nutrients. Hence, scientific Si management in croplands will be helpful for maintaining sustainable dev

Crop harvesting and residue removal from croplands often result in imbalanced biogeochemical cycles of carbon and nutrients in croplands, putting forward an austere challenge to sustainable agricultural production. As a beneficial element, silicon(Si) has multiple eco-physiological functions, which could help crops to acclimatize their unfavorable habitats. Although many studies have reported that the application of Si can alleviate multiple abiotic and biotic stresses and increase biomass accumulation, the effects of Si on carbon immobilization and nutrients uptake into plants in croplands have not yet been explored. This review focused on Si-associated regulation of plant carbon accumulation, lignin biosynthesis, and nutrients uptake, which are important for biogeochemical cycles of carbon and nutrients in croplands. The tradeoff analysis the supply of bioavailable Si can enhance plant net photosynthetic rate and biomass carbon production (especially root biomass input to soil organic carbon pool), but reduce shoot lignin biosynthesis. Besides, the application of Si could improve uptake of most nutrients under deficient conditions, but restricts excess uptake when they are supplied in surplus amounts. Nevertheless, Si application to crops may enhance the uptake of nitrogen and iron when they are supplied in deficient to luxurious amounts, while potassium uptake enhanced by Si application is often involved in alleviating salt stress and inhibiting excess sodium uptake in plants. More importantly, the amount of Si accumulated in plant positively correlates with nutrients release during the decay of crop biomass, but negatively correlates with straw decomposability due to the reduced lignin synthesis. The Si-mediated plant growth and litter decomposition collectively suggest that Si cycling in croplands plays important roles in biogeochemical cycles of carbon and nutrients. Hence, scientific Si management in croplands will be helpful for maintaining sustainable dev

Crop harvesting and residue removal from croplands often result in imbalanced biogeochemical cycles of carbon and nutrients in croplands, putting forward an austere challenge to sustainable agricultural production. As a beneficial element, silicon(Si) has multiple eco-physiological functions, which could help crops to acclimatize their unfavorable habitats. Although many studies have reported that the application of Si can alleviate multiple abiotic and biotic stresses and increase biomass accumulation, the effects of Si on carbon immobilization and nutrients uptake into plants in croplands have not yet been explored. This review focused on Si-associated regulation of plant carbon accumulation, lignin biosynthesis, and nutrients uptake, which are important for biogeochemical cycles of carbon and nutrients in croplands. The tradeoff analysis the supply of bioavailable Si can enhance plant net photosynthetic rate and biomass carbon production (especially root biomass input to soil organic carbon pool), but reduce shoot lignin biosynthesis. Besides, the application of Si could improve uptake of most nutrients under deficient conditions, but restricts excess uptake when they are supplied in surplus amounts. Nevertheless, Si application to crops may enhance the uptake of nitrogen and iron when they are supplied in deficient to luxurious amounts, while potassium uptake enhanced by Si application is often involved in alleviating salt stress and inhibiting excess sodium uptake in plants. More importantly, the amount of Si accumulated in plant positively correlates with nutrients release during the decay of crop biomass, but negatively correlates with straw decomposability due to the reduced lignin synthesis. The Si-mediated plant growth and litter decomposition collectively suggest that Si cycling in croplands plays important roles in biogeochemical cycles of carbon and nutrients. Hence, scientific Si management in croplands will be helpful for maintaining sustainable dev

Crop harvesting and residue removal from croplands often result in imbalanced biogeochemical cycles of carbon and nutrients in croplands, putting forward an austere challenge to sustainable agricultural production. As a beneficial element, silicon(Si) has multiple eco-physiological functions, which could help crops to acclimatize their unfavorable habitats. Although many studies have reported that the application of Si can alleviate multiple abiotic and biotic stresses and increase biomass accumulation, the effects of Si on carbon immobilization and nutrients uptake into plants in croplands have not yet been explored. This review focused on Si-associated regulation of plant carbon accumulation, lignin biosynthesis, and nutrients uptake, which are important for biogeochemical cycles of carbon and nutrients in croplands. The tradeoff analysis the supply of bioavailable Si can enhance plant net photosynthetic rate and biomass carbon production (especially root biomass input to soil organic carbon pool), but reduce shoot lignin biosynthesis. Besides, the application of Si could improve uptake of most nutrients under deficient conditions, but restricts excess uptake when they are supplied in surplus amounts. Nevertheless, Si application to crops may enhance the uptake of nitrogen and iron when they are supplied in deficient to luxurious amounts, while potassium uptake enhanced by Si application is often involved in alleviating salt stress and inhibiting excess sodium uptake in plants. More importantly, the amount of Si accumulated in plant positively correlates with nutrients release during the decay of crop biomass, but negatively correlates with straw decomposability due to the reduced lignin synthesis. The Si-mediated plant growth and litter decomposition collectively suggest that Si cycling in croplands plays important roles in biogeochemical cycles of carbon and nutrients. Hence, scientific Si management in croplands will be helpful for maintaining sustainable dev

Crop harvesting and residue removal from croplands often result in imbalanced biogeochemical cycles of carbon and nutrients in croplands, putting forward an austere challenge to sustainable agricultural production. As a beneficial element, silicon(Si) has multiple eco-physiological functions, which could help crops to acclimatize their unfavorable habitats. Although many studies have reported that the application of Si can alleviate multiple abiotic and biotic stresses and increase biomass accumulation, the effects of Si on carbon immobilization and nutrients uptake into plants in croplands have not yet been explored. This review focused on Si-associated regulation of plant carbon accumulation, lignin biosynthesis, and nutrients uptake, which are important for biogeochemical cycles of carbon and nutrients in croplands. The tradeoff analysis the supply of bioavailable Si can enhance plant net photosynthetic rate and biomass carbon production (especially root biomass input to soil organic carbon pool), but reduce shoot lignin biosynthesis. Besides, the application of Si could improve uptake of most nutrients under deficient conditions, but restricts excess uptake when they are supplied in surplus amounts. Nevertheless, Si application to crops may enhance the uptake of nitrogen and iron when they are supplied in deficient to luxurious amounts, while potassium uptake enhanced by Si application is often involved in alleviating salt stress and inhibiting excess sodium uptake in plants. More importantly, the amount of Si accumulated in plant positively correlates with nutrients release during the decay of crop biomass, but negatively correlates with straw decomposability due to the reduced lignin synthesis. The Si-mediated plant growth and litter decomposition collectively suggest that Si cycling in croplands plays important roles in biogeochemical cycles of carbon and nutrients. Hence, scientific Si management in croplands will be helpful for maintaining sustainable dev

The main objectives of this study were to elucidate the roles of silicon (Si) in alleviating cadmium-induced oxidative stress in roots of pakchoi grown hydroponically using two contrasting pakchoi (Brassica chinensis L.) cultivars: cv. Shanghaiqing (SHQ), a Cd-sensitive cultivar and cv. Hangyoudong (HYD), a Cd-tolerant cultivars. Lipid peroxidation, enzymatic and non-enzymatic antioxidants and histochemical stainning were examined in the two pakchoi plants grown under lower (0.5 mg Cd L-1) and higher (5 mg Cd L-1) Cd stress without or with 1.5 mM Si. Root length was decreased by Cd stress, especially in the sensitive cultivar. Addition of Si significantly increased root length of both cultivars under both levels of Cd tested. The decreases in activities of superoxide dismutase (SOD), catalase (CAT), asorbate peroxidases (APX) and increases in concentrations of malondialdehyde (MDA) were observed in the Cd treatments, which were all counteracted by addition of Si. These alleviative effects of Si were more significant in the Cd-tolerant cultivar than in the Cd-sensitive cultivar. Such effects were confirmed by using histochemical staining methods. All these results suggest that Si-mediated alleviation of Cd toxicity be attributed mainly to Si-enhanced root length, antioxidant defense capacity and membrane integrity and to Si-suppressed oxidative damage.

The main objectives of this study were to elucidate the roles of silicon (Si) in alleviating cadmium-induced oxidative stress in roots of pakchoi grown hydroponically using two contrasting pakchoi (Brassica chinensis L.) cultivars: cv. Shanghaiqing (SHQ), a Cd-sensitive cultivar and cv. Hangyoudong (HYD), a Cd-tolerant cultivars. Lipid peroxidation, enzymatic and non-enzymatic antioxidants and histochemical stainning were examined in the two pakchoi plants grown under lower (0.5 mg Cd L-1) and higher (5 mg Cd L-1) Cd stress without or with 1.5 mM Si. Root length was decreased by Cd stress, especially in the sensitive cultivar. Addition of Si significantly increased root length of both cultivars under both levels of Cd tested. The decreases in activities of superoxide dismutase (SOD), catalase (CAT), asorbate peroxidases (APX) and increases in concentrations of malondialdehyde (MDA) were observed in the Cd treatments, which were all counteracted by addition of Si. These alleviative effects of Si were more significant in the Cd-tolerant cultivar than in the Cd-sensitive cultivar. Such effects were confirmed by using histochemical staining methods. All these results suggest that Si-mediated alleviation of Cd toxicity be attributed mainly to Si-enhanced root length, antioxidant defense capacity and membrane integrity and to Si-suppressed oxidative damage.

The objective of this study is to elucidate the roles of silicon (Si) in enhancing tolerance to excess zinc (Zn) in two contrasting rice (Oryza sativa L.) cultivars: i.e. cv. TY-167 (Zn-resistant) and cv. FYY-326 (Zn-sensitive). Root morphology, antioxidant defense reactions and lipid peroxidation, and histochemical staining were examined in rice plants grown in the nutrient solutions with normal (0.15 mu M) and high (2 mM) Zn supply, without or with 1.5 mM Si. Significant inhibitory effects of high Zn treatment on plant growth were observed. Total root length (TRL), total root surface area (TRSA) and total root tip amount (TRTA) of both cultivars were decreased significantly in plants treated with high Zn, whereas these root parameters were significantly increased when Zn-stressed plants were supplied with 1.5 mM Si. Supply of Si also significantly decreased Zn concentration in shoots of both cultivars, indicating lower root-to-shoot translocation of Zn. Moreover, superoxide dismutase (SOD), catalase (CAT), and asorbate peroxidase (APX) activities were increased, whereas malondialdehyde (MDA) and hydrogen peroxide (H2O2) concentrations were decreased in Si-supplied plants of both Zn-sensitive and Zn-resistant rice cultivars exposed to Zn stress. These alleviative effects of Si, further confirmed by the histochemical staining methods, were more prominent in the Zn-resistant cultivar than in the Zn-sensitive one. Taken together, all these results suggest that Si-mediated alleviation of Zn toxicity is mainly attributed to Si-mediated antioxidant defense capacity and membrane integrity. The possible role of Si in reduction of root-to-shoot translocation of Zn can also be considered.