Revealing horizontal and vertical variation of soil organic carbon, soil total nitrogen and C:N ratio in subtropical forests of southeastern China.

Soil organic carbon (SOC) and total nitrogen (STN) are crucial soil quality indicators in a forest ecosystem. Their cycling processes and interactions have a key impact on the plants productivity, potential carbon sequestration and stability of the terrestrial ecosystem. In this study, soil profile samples (0-100 cm) were collected from 906 plots of typical subtropical forest in Zhejiang Province, southeastern China. Moran's I, geostatistics and geographic information system (GIS) techniques were used to study the vertical and horizontal heterogeneity of SOC, STN and C:N ratio. The results indicated that the contents of SOC and STN clearly decreased with the soil depth increasing (from 0 to 10 cm layer to 60-100 cm layer). The spatial distributions of SOC and STN were consistent with the topography, showing a decreasing trend from southwest to northeast of Zhejiang Province. The results of ANOVA and correlation analyses indicated that the dominant tree species, elevation and Normalized Difference Vegetation Index (NDVI) were the key factors affecting SOC and STN contents. For the total 0-100 cm soil layer, the mean densities of SOC and STN were 108.53 Mg ha-1 and 0.08 Mg ha-1, respectively. The total stocks of SOC and STN were 877.19 Tg and 84.42 Tg. Approximately 65% SOC and 45% STN were belonged to the upper 30 cm soil layer, which was strongly related to the actual soil thickness. The results could provide critical information for forestry and environmental management related to C and N accumulations in subtropical forests of China.

Quantitative analysis of analytical elements in Al-In-Sn-O thin film based on comprehensive calibration curves using picosecond laser-induced breakdown spectroscopy.

Al-In-Sn-O (AITO) thin film refers to a novel wide-bandgap transparent conductive material, which is formed by doping the aluminum element into In-Sn-O material. It is of promising application in deep ultraviolet optoelectronic devices. Al/Al+In+Sn and Sn/Al+In+Sn are capable of impacting the optical and electrical properties of AITO thin film. Three groups of AITO thin film samples with different sputtering powers, sputtering pressures, and sputtering times were prepared with magnetron sputtering. The concentration ratio of Al/Al+In+Sn and Sn/Al+In+Sn in AITO samples was quantitatively analyzed with laser-induced breakdown spectroscopy (LIBS) technology. A single calibration curve was drawn based on the sputtering parameters of each group, and the comprehensive calibration curves of two concentration ratios under any sputtering parameters were plotted. The accuracy of the comprehensive calibration curve was determined with samples prepared under random sputtering parameters, and the energy dispersive x-ray spectroscopy analysis results were compared with the LIBS technical analysis results. The relative error was less than 5%, so the LIBS technical analysis was demonstrated to be accurate. By building the comprehensive calibration curve, a novel method to conduct rapid online analysis of AITO thin films and timely determination of photoelectrical properties is presented, and the new application of LIBS technology is developed in thin film semiconductor materials.

Effect of lead (Pb) on antioxidation system and accumulation ability of Moso bamboo (Phyllostachys pubescens).

The antioxidation system and accumulation ability of Moso bamboo (Phyllostachys pubescens), which is a valuable remediation material with large biomass and rapid growth rate were studied in hydroponics and pot experiments. In hydroponics experiment, TBARS concentrations and SOD activities decreased with increase of Pb treatments. The activities of POD boost up with elevated Pb treatments, and reached peak level with application of 400µM Pb. Proline concentrations reduced with application of 20µM Pb and then enhanced consistently with application of 100 and 400µM Pb. The biomass of Moso bamboo improved with increase of Pb treatments upto 400mgkg-1, and then decreased with application of each additional increment of Pb in pot experiment. Application of 800mgkg-1 Pb showed significant increase of photosynthetic pigments, however, non significant variation was observed for other treatments. The Pb concentration in roots, stems and leaves attained 523mgkg-1, 303mgkg-1 and 222mgkg-1 respectively with application of 1600mgkg-1 Pb compared with control. Analysis of TEM-EDX revealed that Pb in cell was mostly concentrated in cytoplasm then in cell wall and followed by vacuole. It is concluded that Moso bamboo may be potential remediation species for phytoremediation in low Pb contaminated soils.

Spatial distribution and variability of carbon storage in different sympodial bamboo species in China.

Selection of tree species is potentially an important management decision for increasing carbon storage in forest ecosystems. This study investigated and compared spatial distribution and variability of carbon storage in 8 sympodial bamboo species in China. The results of this study showed that average carbon densities (CDs) in the different organs decreased in the order: culms (0.4754 g g(-1)) > below-ground (0.4701 g g(-1)) > branches (0.4662 g g(-1)) > leaves (0.4420 g g(-1)). Spatial distribution of carbon storage (CS) on an area basis in the biomass of 8 sympodial bamboo species was in the order: culms (17.4-77.1%) > below-ground (10.6-71.7%) > branches (3.8-11.6%) > leaves (0.9-5.1%). Total CSs in the sympodial bamboo ecosystems ranged from 103.6 Mg C ha(-1) in Bambusa textilis McClure stand to 194.2 Mg C ha(-1) in Dendrocalamus giganteus Munro stand. Spatial distribution of CSs in 8 sympodial bamboo ecosystems decreased in the order: soil (68.0-83.5%) > vegetation (16.8-31.1%) > litter (0.3-1.7%). Total current CS and biomass carbon sequestration rate in the sympodial bamboo stands studied in China is 93.184 × 10(6) Mg C ha(-1) and 8.573 × 10(6) Mg C yr(-1), respectively. The sympodial bamboos had a greater CSs and higher carbon sequestration rates relative to other bamboo species. Sympodial bamboos can play an important role in improving climate and economy in the widely cultivated areas of the world.

Effect of 26 years of intensively managed Carya cathayensis stands on soil organic carbon and fertility.

Chinese hickory (Carya cathayensis), a popular nut food tree species, is mainly distributed in southeastern China. A field study was carried out to investigate the effect of long-term intensive management on fertility of soils under a C. cathayensis forest. Results showed that after 26 years' intensive management, the soil organic carbon (SOC) content of the A and B horizons reduced by 19% and 14%, respectively. The reduced components of SOC are mainly the alkyl C and O-alkyl C, whereas the aromatic C and carbonyl C remain unchanged. The reduction of active organic matter could result in degradation of soil fertility. The pH value of soil in the A horizon had dropped by 0.7 units on average. The concentrations of the major nutrients also showed a decreasing trend. On average the concentrations of total nitrogen (N), phosphorus (P), and potassium (K) of tested soils dropped by 21.8%, 7.6%, and 13.6%, respectively, in the A horizon. To sustain the soil fertility and C. cathayensis production, it is recommended that more organic fertilizers (manures) should be used together with chemical fertilizers. Lime should also be applied to reduce soil acidity.

Effect of copper toxicity on root morphology, ultrastructure, and copper accumulation in Moso bamboo (Phyllostachys pubescens).

A hydroponic culture experiment was conducted to study the effect of copper toxicity on root morphology, ultrastructure, and copper accumulation in Moso bamboo (Phyllostachys pubescens). Root ultrastructure of Moso bamboo was studied by transmission electron microscopy and scanning electron microscopy. Application of 200 µM Cu resulted in an accumulation of 810 mg kg(-1) dry weight and 91 mg kg(-1) dry weight Cu in roots and shoots, respectively. The majority of the plants did not survive the application of 400 µM Cu. Biomass production declined consistently with application of each additional increment of Cu. Root growth was more severely inhibited than shoot growth. Cu adversely affected the root morphology of the plants, however, root surface area and number of root tips increased slightly at low levels of Cu. Root cell ultrastructure and organelles changed significantly under Cu stress, in particular, cell walls, mitochondria, and xylem parenchyma were affected.

Combination system of full-scale constructed wetlands and wetland paddy fields to remove nitrogen and phosphorus from rural unregulated non-point sources.

Constructed wetlands (CWs) have been used effectively to remove nitrogen (N) and phosphorus (P) from non-point sources. Effluents of some CWs were, however, still with high N and P concentrations and remained to be pollution sources. Widely distributed paddy fields can be exploited to alleviate this concern. We were the first to investigate a combination system of three-level CWs with wetland paddy fields in a full scale to remove N and P from rural unregulated non-point sources. The removal efficiencies (REs) of CWs reached 57.3 % (37.4-75.1 %) for N and 76.3 % (62.0-98.4 %) for P. The CWs retained about 1,278 kg N ha(-1) year(-1) and 121 kg P ha(-1) year(-1). There was a notable seasonal change in REs of N and P, and the REs were different in different processing components of CWs. The removal rates of wetland paddy fields adopt "zero-drainage" water management according to local rainfall forecast and physiological water demand of crop growth reached 93.2 kg N ha(-1) year(-1) and 5.4 kg P ha(-1) year(-1). The rice season had higher potential in removing N and P than that in the wheat season. The whole combined system (0.56 ha CWs and 5.5 ha wetland paddy fields) removed 1,790 kg N year(-1) and 151 kg P year(-1), which were higher than those from CWs functioned alone. However, another 4.7-ha paddy fields were needed to fully remove the N and P in the effluents of CWs. The combination of CWs and paddy fields proved to be a more efficient nutrient removal system.

[Clinical study of endoscopic surgery for recurrent nasopharyngeal carcinoma].

Objective:To compare the clinical effects and complications of surgery + chemotherapy and radiotherapy + chemotherapy in patients with nasopharyngeal carcinoma recurrence, so as to compare the safety and efficacy of two different therapeutic methods. Methods:A retrospective analysis was performed on 40 patients with recurrent nasopharyngeal carcinoma after radiotherapy and chemotherapy admitted to our hospital from January 2016 to June 2020. Among them, 26 patients were treated with surgery. The recurrent tumor was removed under nasal endoscope, and the frozen resection margin was negative during the operation. Chemotherapy was continued for stage Ⅲ and Ⅳ patients from 3 to 5 weeks after surgery. Fourteen patients received secondary radiotherapy and chemotherapy. Postoperative complications and survival rate were observed. Results:There were 14 patients in the secondary chemoradiotherapy group（control group） and 26 patients in the nasal endoscopic surgery group（observation group）. Among the 26 patients, 19 patients underwent nasal septal mucosal repair, 5 patients underwent temporal muscle flap repair, 2 patients underwent submental flap repair, 2 patients had nasal septal mucosal flap necrosis and cerebrospinal fluid leakage, and the temporal muscle flap was used for secondary repair in the second stage operation, and 8 patients needed cervical lymph node dissection. The patients recovered well after surgery, and the patients in stage Ⅲ and Ⅳ were treated with chemotherapy after 3 weeks to 5 weeks according to the patient's wound condition. There were significant differences in the incidence of complications and 1-, 2-, and 3-year survival rates between the two groups（P<0.05）. Conclusion:Patients with recurrent nasopharyngeal carcinoma can be treated by nasal endoscopic surgery to remove the tumor, and the use of pedicled nasal septal mucosal flap or temporal muscle flap for skull base reconstruction, The operation can effectively prevent major complications such as internal carotid artery rupture and hemorrhage, and improve the survival rate and quality of life of patients. It provides a safe and effective treatment for patients with recurrent nasopharyngeal carcinoma.

[Effects of Long-term Sod Cultivation on Chinese Hickory Plantation Soil Fungal Community and Enzyme Activities].

A long-term field experiment was conducted at a Chinese hickory (Carya cathayensis) plantation from 2011 to 2021, with the purpose of researching the effects of long-term sod cultivation on hickory plantation soil fungal communities and enzyme activities and providing experience for ecological management in other plantations. Sod cultivation included oilseed rape (Brassica chinensis, BR), Chinese milk vetch (Astragalus sinicus, AS), and oilseed rape+Chinese milk vetch (BA), and clear tillage (CT) served as a contrast. The soil fertility, fungal community composition and diversity, and soil enzyme activities were determined. The results showed that:① long-term sod cultivation significantly increased soil nutrient contents and availability, and pH increased variably from different sod cultivation treatments (P<0.05). ②The soil fungal community composition was changed by long-term sod cultivation. The relative abundance of Ascomycota, which utilized the readily decomposed organic matter, was increased, whereas the relative abundance of Basidiomycota, which degraded stubborn organic matter, decreased. Long-term sod cultivation shifted the soil dominant genera, as BR and BA increased the relative abundance of somemycorrhizal fungi that could form mutually beneficial structures with dominant plant genera after sod cultivation,whereas AS increased the relative abundance of saprophytic fungi that could decompose the remains of dead plants and animals. The soil fertility factors including pH, available nitrogen, microbial biomass nitrogen, and water-soluble organic carbon were revealed to have a significant influence on the soil fungal composition (P<0.05). ③ Moreover, long-term sod cultivation stimulated the activities of soil enzymes involved in the carbon and nitrogen cycle. Apart from BA, sod cultivation treatments decreased the activities of alkaline phosphatase, which was involved in the soil P turnover. The correlation analysis demonstrated that the correlations between activities of enzymes decomposing carbon and nitrogen and soil fertility were significant (P<0.05 or P<0.01). The activities of phosphatase were positively correlated with soil microbial biomass carbon and nitrogen. Long-term sod cultivation could improve soil nutrient content and availability, optimized soil fungal community structure, and promoted soil nutrient turnover enzyme activities.

Spatial variation, sources identification and risk assessment of soil heavy metals in a typical Torreya grandis cv. Merrillii plantation region of southeastern China.

Torreya grandis (Torreya grandis cv. Merrillii) is a unique nut tree species in China. Currently, researches on Torreya grandis focus on nuts quality and yield, while few works are related to the soil quality of Torreya grandis plantation. In this study, the typical Torreya grandis production areas of Zhuji, Shengzhou, Keqiao and Dongyang cities along the Kuaiji Mountain were selected. A total of 121 topsoil samples (0-20 cm) were collected based on a grid of 1 km × 1 km. The results indicated that the average concentrations of Cd, Cr, Cu, As, Ni and Pb in soils were 0.12, 49.01, 27.95, 14.28, 26.97 and 40.28 mg kg-1, respectively. The concentrations of six heavy metals all exceeded the background values, and there were different degrees of pollution levels. The results of Moran's I indicated that the spatial high-high clusters of soil heavy metals were mainly distributed in Zhuji and the junction of Shengzhou and Keqiao. The partial least squares path analysis of structural equation modeling (PLS-SEM) showed that OM and soil nutrients had extremely significant effects on soil heavy metals. Sources identification of principle component analysis (PCA) and positive matrix factorization model (PMF) revealed that agricultural activities, natural factors and mining were the main sources of soil heavy metals. The human health risks caused by soil heavy metals pollution were generally acceptable based on Monte Carlo simulation method. For the heavy-metal polluted area, management measures should be considered in order to protect human health.

[Microbial Composition and Diversity in Soil of Torreya grandis cv. Merrillii Relative to Different Cultivation Years After Land Use Conversion].

In order to explore the impacts of the land use conversion from a Phyllostachy pubescens (moso bamboo) forest to a Torreya grandis cv. Merrillii plantation, as well as the cultivating years of the T. grandis cv. Merrillii plantation, on the soil microbial community, this research studied the soil microbial structure and diversity of a moso bamboo forest, T. grandis cv. Merrillii plantations (5, 10, and 30 a), and a T. grandis cv. Merrillii-mountain rice interplanting plantation (5 a) using the high-throughput sequencing technique, and the relationship between the microbial community and environmental factors was further explored. The results showed that after the land use change, the Shannon index and Chao1 index of the soil bacterial community increased significantly; the Simpson index increased significantly in the 30 a T. grandis cv. Merrillii plantation, whereas the Shannon index decreased significantly. Both the Simpson index and Chao index of the soil fungal community had no significant difference under different land use types. whereas the Shannon index was significantly decreased in the 30 a T. grandis cv. Merrillii plantation. PCoA analysis of the soil microbial community at the genus level showed that land use type played a vital role in driving the changes in soil bacterial and fungal communities. The compositions of the soil microbial communities between the two 5 a stands were most similar. The dominant phyla of soil bacteria mainly included Acidobacteria, Proteobacteria, Actinobacteria, and Chloroflexi. The results of cluster analysis showed that the soil bacterial community changed significantly at the genus level after the conversion of land use; the abundance of most dominant bacterial communities decreased with increasing cultivation. The fungal community was mainly composed of Ascomycota, Basidiomycota, and Zygomycota, whose changes in community characteristics were similar to those of bacteria. The results of RDA analysis showed that pH, organic matter, available phosphorus, available potassium, and water-soluble organic carbon and nitrogen were significantly correlated with soil microbial community. Therefore, these soil fertility properties might be the driving factors affecting the structure of bacterial communities. This study provided a theoretical basis for solving the problem of soil quality deterioration in T. grandis cv. Merrillii stand land management.

[Effects of Nitrogen Fertilizer Management on CH4 and N2O Emissions in Paddy Field].

Methane (CH4) and nitrous oxide (N2O) are two extremely important greenhouse gases in the atmosphere. Nitrogen fertilizer is an important factor affecting CH4 and N2O emissions in rice fields. Rational application of nitrogen fertilizer can not only promote high yields of rice but also reduce greenhouse gas emissions. Existing studies have shown that nitrogen reduction and optimal application can effectively improve the nitrogen use efficiency of rice on the basis of ensuring the yield and reduce the loss of N2O caused by nitrification and denitrification of excessive nitrogen in soil. Fertilization times and fertilizer types have significant effects on CH4 and N2O emissions in paddy fields. In this study, a field experiment was conducted for two consecutive years (2019-2020) to study the effects of fertilizer application on CH4 and N2O emissions from rice fields by setting up four treatments consisting of no fertilizer (CK), customary fertilizer application by farmers (CF), twice fertilizer (TT), and 20% replacement of chemical fertilizer by organic fertilizer (OF) using static chamber-gas chromatography. Additionally, the effect of integrating rice yield and integrated global warming potential (GWP) on the greenhouse gas emission intensity (GHGI) per unit of rice yield was analyzed to explore fertilizer application for yield increase and emission reduction in a typical rice growing area in the middle and lower reaches of Yangtze River. The results showed that:① compared with those of CK, the fertilizer treatments reduced CH4 emissions by 14.6%-25.1% and increased N2O emissions by 610%-1836% in both years; ② compared with those of CF, both the TT and OF treatments showed a trend of increasing CH4 emissions and reducing N2O emissions. CH4 emissions increased by 1.8% (P>0.05) and 14.0% (P<0.05), respectively. The annual average of N2O emissions decreased by 63.3% (P<0.05) and 49.2% (P<0.05) in both the TT and OF treatments, respectively. ③ Compared with that of CK, both fertilizer applications increased rice yield and reduced GHGI; compared with that of CF, the OF and TT treatments increased the average annual rice yield by 17.0% and 10.7%, respectively, and reduced GHGI by 6.8% and 13.7%, respectively. The OF treatment had a better yield increase than that of the TT treatment, and the TT treatment had a slightly better emission reduction than that of the OF treatment. In terms of combined yield and GHG emission reduction, both twice fertilizer (TT) and 20% replacement of chemical fertilizer by organic fertilizer (OF) could reduce the intensity of GHG emission per unit of rice yield and achieve yield increase and emission reduction while ensuring rice yield.

Enhanced soil potential N2O emissions by land-use change are linked to AOB-amoA and nirK gene abundances and denitrifying enzyme activity in subtropics.

Conversion of forestland to intensively managed agricultural land occurs worldwide and can increase soil nitrous oxide (N2O) emissions by altering the transformation processes of nitrogen (N) cycling related microbes and environmental conditions. However, little research has been conducted to assess the relationships between nitrifying and denitrifying functional genes and enzyme activities, the altered soil environment and N2O emissions under forest conversion in subtropical China. Here, we investigated the long-term (two decades) effect of converting natural forests to intensively managed tea (Camellia sinensis L.) plantations on soil potential N2O emissions, inorganic N concentrations, functional gene abundances of nitrifying and denitrifying bacteria, as well as nitrifying and denitrifying enzyme activities in subtropical China. The conversion significantly increased soil potential N2O emissions, which were regulated directly by increased denitrifying enzyme activity (52 %) and nirS + nirK gene abundance (38 %) as shown by structural equation modeling, and indirectly by AOB-amoA gene abundance and inorganic N concentration. Our results indicate that converting natural forests to tea plantations directly increases soil inorganic N concentration, resulting in increases in the abundance of soil nitrifying and denitrifying microorganisms and the associated N2O emissions. These findings are crucial for disentangling the factors that directly and indirectly affect soil potential N2O emissions respond to the conversion of forest to tea plantation.

Mitigation of methane emission in a rice paddy field amended with biochar-based slow-release fertilizer.

Despite improving soil quality and reducing nitrogen (N) loss in paddy soil, replacing chemical fertilizer with organic fertilizer would significantly accelerate greenhouse gas emission in terms of methane (CH4). The application of slow-release fertilizer has been proposed an effective approach to control CH4 emissions, in addition to reducing N loss. Yet, the understanding of CH4 emissions from paddy fields with the additions of different fertilizers is still less known. Therefore, the effects of different fertilizer treatments, including chemical fertilizer treatment (CF), mixed chemical and organic fertilizer treatment (OF), biochar-based slow-release fertilizer treatment (SF), and no fertilizer control treatment (CK) on CH4 emissions and methanogenic community structure in paddy soils were investigated through a field experiment. Results showed that slow-release fertilizer addition significantly decreased CH4 emissions by 33.4%, during the whole rice growing season compared to those in OF. The cumulative CH4 emissions were in a significantly positive relation to soil NH4+-N. Slow-release fertilizer amendment decreased the relative abundances of Methanosarcina and Methanoregula and increased the relative abundances of hydrogenotrophic Methanocella and Rice Cluster I. Reduced CH4 emissions with slow-release fertilizer amendment might be mainly attributed to the different forms of N in the fertilizer and available potassium (K) in the paddy soil. Our findings produce novel insights into the application of slow-release fertilizer in controlling CH4 emissions from rice fields.

A 10-year monitoring of soil properties dynamics and soil fertility evaluation in Chinese hickory plantation regions of southeastern China.

Monitoring the temporal and spatial variation of soil properties is helpful to understand the evolution of soil properties and adjust the management method in time. Soil fertility evaluation is an urgent need to understand soil fertility level and prevent soil degradation. Here, we conducted an intensive field investigation in Chinese hickory (Carya cathayensis Sarg.) plantation to clarify the spatial and temporal variation of soil properties and its influencing factors, and to evaluate the change of soil fertility. The results showed that the soil pH and soil organic carbon (SOC) significantly increased from 2008 to 2018, while available nitrogen (AN) significantly decreased from 2008 to 2018. The semi-variance revealed that except available phosphorus (AP), the spatial dependencies of soil properties increased from 2008 to 2018. An increasing south-north gradient was found for soil AN, AP, available potassium (AK) and SOC and a decreasing south-north gradient was found for soil pH. The average soil fertility in the whole area was increased from 2008 to 2018. Our findings demonstrated that the changes of the management measures were the reason for the change of soil properties from 2008 to 2018. Therefore, rational fertilization strategies and sod cultivation are recommended to maintain the long-term development of the producing forest.

Silicon fertilizer and biochar effects on plant and soil PhytOC concentration and soil PhytOC stability and fractionation in subtropical bamboo plantations.

The use of exogenous silicon (Si) amendments, such as Si fertilizers and biochar, can effectively increase crop Si uptake and the formation of phytoliths, which are siliceous substances that are abundant in numerous plant species. Phytolith-occluded carbon (C) (PhytOC) accumulation in soil plays an important role in long-term soil organic C (SOC) storage. Nevertheless, the effects of both Si fertilizer and biochar application on PhytOC sequestration in forest plant-soil systems have not been studied. We investigated the impact of Si fertilizer and biochar applications on 1) the PhytOC pool size, the solubility of plant and soil phytoliths, and soil PhytOC in soil physical fractions (light (LFOM) and heavy fractions of organic matter (HFOM)) in Moso bamboo (Phyllostachys pubescens) forests; and 2) the relationships among plant and soil PhytOC concentrations and soil properties. We used a factorial design with three Si fertilizer application rates: 0 (S0), 225 (S1) and 450 (S2) kg Si ha-1, and two biochar application rates: 0 (B0) and 10 (B1) t ha-1. The concentrations of PhytOC in the bamboo plants and topsoil (0-10 cm) increased with increasing Si fertilizer addition, regardless of biochar application. Biochar addition increased the soil PhytOC pool size, as well as the LFOM- and HFOM-PhytOC fractions, regardless of Si fertilizer application. The Si fertilizer application increased or had no effect on soil phytolith solubility with or without biochar application, respectively. Soil PhytOC was correlated with the concentration of soil organic nitrogen (R2 = 0.32), SOC (R2 = 0.51), pH (R2 = 0.28), and available Si (R2 = 0.23). Furthermore, Si fertilizer application increased plant and soil PhytOC by increasing soil available Si. Moreover, biochar application increased soil PhytOC concentration in LFOM-PhytOC and the unstable fraction of PhytOC. We conclude that Si fertilizer and biochar application promoted PhytOC sequestration in the plant-soil system and changed its distribution in physical fractions in the Moso bamboo plantation in subtropical China.

Converting evergreen broad-leaved forests into tea and Moso bamboo plantations affects labile carbon pools and the chemical composition of soil organic carbon.

This study aimed to explore the effects of conversion from evergreen broad-leaved forests (EBFs) to tea plantations (TPs) and Moso bamboo (Phyllostachys heterocycla var. pubescens) plantations (MBPs) and the subsequent long-term intensive management on the soil carbon pool and the chemical composition of soil organic carbon (SOC). Soil samples from three layers (0-10, 10-30 and 30-60 cm, respectively) were collected from adjacent EBFs, TPs and MBPs in An'ji County, Zhejiang Province, China. The physico-chemical properties of soils, including bulk density, SOC and its different fractions were determined. The chemical composition of SOC was also measured using 13C-nuclear magnetic resonance spectroscopy (NMR). The results showed that conversion from EBFs to TPs and MBPs decreased the concentrations of water soluble organic carbon (WSOC), light and heavy fraction organic carbon (LFOC, HFOC) and humus carbon (HC) (P < 0.05), reduced the O-alkyl C and carbonl C content, but increased the alkyl C, Aromatic C, aromaticity and the ratio of alkyl C/O-alkyl C (A/O-A) (P < 0.05). These results suggested that intensive management markedly altered the chemical structure of SOC and labile carbon pools. Our results demonstrated that converting EBFs to TPs and MBPs had a negative effect on SOC content and a positive effect on SOC stability. Therefore, management practices such as rational fertilization and sod cultivation are recommended after land-use conversion.

Effects of biochar on growth, and heavy metals accumulation of moso bamboo (Phyllostachy pubescens), soil physical properties, and heavy metals solubility in soil.

Pot experiment was conducted to investigate the effects of wood biochar (5%), bamboo biochar (5%), rice straw biochar (5%) and Chinese walnut shell biochar (5%) on growth, accumulation of heavy metals in moso bamboo, soil physical properties, and solubility of heavy metals in soil. The results revealed that dry weight of moso bamboo was significantly increased in treatments of wood biochar (5%), rice straw biochar (5%) and Chinese walnut shell biochar (5%) except bamboo biochar (5%). Application of straw biochar (5%) was most effective in enhancing plants biomass, with increase of 157%, 113% and 111% in leaves, roots and stems of moso bamboo. All treatments of biochar have significantly improved soil electrical conductivity with maximum increase of 360% compared to CK. In case of heavy metals accumulation, application of 5% bamboo biochar, straw biochar and Chinese walnut shell biochar has reduced Cu uptake in roots by 15%, 35% and 26%, respectively. The biochars have significantly reduced solubility of soil heavy metals with maximum reduction of 58.91 mg kg-1 and 10.59 mg kg-1 of Cu and Pb with application of rice straw biochar. It is concluded that dry weight of moso bamboo was significantly enhanced by all treatments of biochar except bamboo biochar.

Belowground Phytolith-Occluded Carbon of Monopodial Bamboo in China: An Overlooked Carbon Stock.

Phytolith-occluded carbon (PhytOC), a highly stable carbon (C) fraction resistant to decomposition, plays an important role in long-term global C sequestration. Previous studies have demonstrated that bamboo plants contribute greatly to PhytOC sink in forests based on their aboveground biomass. However, little is known about the contribution of belowground parts of bamboo to the PhytOC stock. Here, we reported the phytolith and PhytOC accumulation in belowground trunk and rhizome of eight monopodial bamboo species that widely distributed across China. The results showed that the belowground parts made up an average of 39.41% of the total plant biomass of the eight bamboo species. There were significant (p < 0.05) variations in the phytolith and PhytOC concentrations in the belowground trunk and rhizome between the bamboo species. The mean concentrations of PhytOC in dry biomass ranged from 0.34 to 0.83 g kg-1 in the belowground rhizome and from 0.10 to 0.94 g kg-1 in the belowground trunk across the eight bamboo species, respectively. The mean PhytOC stocks in belowground biomass ranged from 2.57 to 23.71 kg ha-1, occupying an average of 23.36% of the total plant PhytOC stocks. This implies that 1.01 × 105 t PhytOC was overlooked based on the distribution of monopodial bamboos across China. Therefore, our results suggest that the belowground biomass of bamboo represents an important PhytOC stock, and should be taken into account in future studies in order to better quantifying PhytOC sequestration capacity.

Sympodial bamboo species differ in carbon bio-sequestration and stocks within phytoliths of leaf litters and living leaves.

Phytolith-occluded carbon (PhytOC) with high resistance against decomposition is an important carbon (C) sink in many ecosystems. This study compared concentrations of phytolith in plants and the PhytOC production of seven sympodial bamboo species in southern China, aiming to provide the information for the managed bamboo plantation and selection of bamboo species to maximize phytolith C sequestration. Leaf litters and living leaves of seven sympodial bamboo species were collected from the field sites. Concentrations of phytoliths, silicon (Si), and PhytOC in leaf litters and living leaves were measured. Carbon sequestration as PhytOC was estimated. There was a considerable variation in the PhytOC concentrations in the leaf litters and living leaves among the seven bamboo species. The mean concentrations of PhytOC ranged from 3.4 to 6.9 g kg(-1) in leaf litters and from 1.6 to 5.9 g kg(-1) in living leaves, with the PhytOC production rates ranging from 5.7 to 52.3 kg e-CO2 ha(-1) year(-1) as leaf litters. Dendrocalamopsis oldhami (Munro) Keng f. had the highest PhytOC production rate. Based on a bio-sequestration rate of 52.3 kg e-CO2 ha(-1) year(-1), we estimated that the current 8 × 10(5) ha of sympodial bamboo stands in China could potentially acquire 4.2 × 10(4) t e-CO2 yearly via phytolith carbon. Furthermore, the seven sympodial bamboo species stored 5.38 × 10(5) t e-CO2 as PhytOC in living leaves and leaf litters in China. It is concluded that sympodial bamboos make a significant contribution to C sequestration and that to maximize the PhytOC accumulation, the bamboo species with the highest PhytOC production rate should be selected for plantation.