The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Xinhua He - One of the best experts on this subject based on the ideXlab platform.
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responses of Soil carbon pool and Soil Aggregates associated organic carbon to straw and straw derived biochar addition in a dryland cropping mesocosm system
Agriculture Ecosystems & Environment, 2018Co-Authors: Rong Huang, Xinhua He, Dong Tian, Sheng LvAbstract:Abstract How to address Soil carbon (C) sequestration and crop straw recycling is an intractable challenge for agriculture. The application of various agricultural straws (including fresh straw, decomposed straw, straw-derived biochar) to Soil alters the Soil C pool. In order to understand Soil C dynamics and the potential C sequestration characters after the addition of straw and/or straw-derived biochar, an in-situ mesocosm experiment was conducted under five treatments as (1) no straw and no biochar control (CT), (2) straw addition only (ST), (3) straw with a straw-decay bacterium (STDB), (4) biochar addition only (BC) and (5) a combination of straw with biochar (STBC). Carbon dioxide (CO2) flux from Soil, total Soil organic C (SOC) and Soil labile organic C (LOC), as well as Soil aggregate associated organic C have been analyzed within a dryland rape-maize cropping system. The results showed that Soil CO2 flux increased with the addition of crop straws (ST, STBC and STDB), but decreased under BC because of a lower LOC under BC, especially microbial biomass C fraction in the LOC. The combined application of STDB increased the percentages of macro-Aggregates (>2 mm and 0.25–2 mm). Meanwhile, the decomposition of organic matter was increased, and the CO2 flux was also increased. The 0.053-0.25 mm aggregate under BC had the highest fine intra-aggregate particulate organic C (iPOC), which promoted C sequestration. However, the higher coarse-iPOC in >2 mm and 0.25–2 mm Aggregates under ST and STDB promoted SOC decomposition and also CO2 flux. Compared with all three straw treatments (ST, STBC and STDB), the sole biochar addition reduced CO2 flux while increased net C sequestration without significant decreases of crop yields and net primary productivity. The sole biochar addition did improve the physical protections for SOC from Soil Aggregates. The obtained results showed differential responses of Soil C pool and Aggregates associated organic C to straw and/or straw-derived biochar addition while providing insights into potential Soil C sequestrations or mitigations by using agriculture based organic materials.
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particles interaction forces and their effects on Soil Aggregates breakdown
Soil & Tillage Research, 2015Co-Authors: Feinan Hu, Chenyang Xu, Hang Li, Song Li, Zhenghong Yu, Yue Li, Xinhua HeAbstract:A B S T R A C T Soil Aggregates profoundly influence Soil fertility and environmental problems, and usually improving Soil aggregation is the central issue in Soil management. Compared with external forces, the internal forces of Soil, i.e., surface hydration force, electrostatic force and van der Waals force, may play a crucial role in aggregate formation and stability. However, there are few quantitative investigations on those fundamental issues. In the present work we aim to calculate surface hydration force, electrostatic force and van der Waals force of Soil/clay particles in aqueous solution, and then quantitatively evaluate the effects of the three forces on Soil/clay Aggregates breakdown. There was critical surface potential in particles interaction pressure and Aggregates breakdown, and if the surface potential exceeded this critical point, a further increase of the surface potential could not significantly increase particles interaction pressure and aggregate breakdown. The critical surface potentials for particle interaction pressure were 207.0 and 179.7 mV for the Soil and montmorillonite, respectively. Our study suggested two steps in aggregate breakdown when dried Aggregates were re-wetted: (1) separating Soil particles in Aggregates to a distance of 1.2–1.4 nm between two adjacent particle surfaces by the surface hydration forces (swelling process); (2) breaking Soil Aggregates in a way of explosion or dispersion under strong or weak electric field conditions. Surface hydration force played a crucial role in aggregate swelling, and without this repulsive pressure, a dried aggregate could not be dispersed again after re-wetting.
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spatial distribution of glomalin related Soil protein and its relationships with root mycorrhization Soil Aggregates carbohydrates activity of protease and β glucosidase in the rhizosphere of citrus unshiu
Soil Biology & Biochemistry, 2012Co-Authors: Qiangsheng Wu, Xinhua He, Kaiping HeAbstract:Abstract Relationships between the spatial distributions of glomalin-related Soil protein (GRSP) and Soil Aggregates, carbohydrates or relevant enzymes are poorly studied. We found that two categories of GRSP, the easily extractable Bradford-reactive Soil protein (EE-BRSP) and total BRSP (T-BRSP), respectively ranged between 0.3–0.6 and 0.5–0.8 mg/g DW Soil, and these two BRSPs decreased with the increase of Soil depth (0–40 cm) in the rhizosphere of a 22-year-old Citrus unshiu orchard. Both EE-BRSP and T-BRSP were significantly positively correlated with mycorrhization, 0.25–0.50 mm Soil water-stable Aggregates, water-extractable or hydrolyzable carbohydrates, and β-glucosidase, but significantly negatively correlated with protease. Our results demonstrate that the spatial distribution of GRSP is significantly affected by mycorrhization, Soil carbohydrate, β-glucosidase and protease.
Shan Yang - One of the best experts on this subject based on the ideXlab platform.
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base cations and micronutrients in Soil Aggregates as affected by enhanced nitrogen and water inputs in a semi arid steppe grassland
Science of The Total Environment, 2017Co-Authors: Ruzhen Wang, Jennifer A J Dungait, Heather L Buss, Shan Yang, Yuge Zhang, Zhuwen Xu, Yong JiangAbstract:Abstract The intensification of grassland management by nitrogen (N) fertilization and irrigation may threaten the future integrity of fragile semi-arid steppe ecosystems by affecting the concentrations of base cation and micronutrient in Soils. We extracted base cations of exchangeable calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na) and extractable micronutrients of iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) from three Soil aggregate sizes classes (microAggregates, 2 mm) from a 9-year N and water field manipulation study. There were significantly more base cations (but not micronutrients) in microAggregates compared to macroAggregates which was related to greater Soil organic matter and clay contents. Nitrogen addition significantly decreased exchangeable Ca by up to 33% in large and small macroAggregates and exchangeable Mg by up to 27% in three Aggregates but significantly increased extractable Fe, Mn and Cu concentrations (by up to 262%, 150%, and 55%, respectively) in all aggregate size classes. However, water addition only increased exchangeable Na, while available Fe and Mn were decreased by water addition when averaging across all N treatments and aggregate classes. The loss of exchangeable Ca and Mg under N addition and extractable Fe and Mn in Soil Aggregates under water addition might potentially constrain the productivity of this semi-arid grassland ecosystem.
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responses of enzymatic activities within Soil Aggregates to 9 year nitrogen and water addition in a semi arid grassland
Soil Biology & Biochemistry, 2015Co-Authors: Ruzhen Wang, Shan Yang, Yuge Zhang, Zhuwen Xu, Maxim Dorodnikov, Yongyong Zhang, Timothy R Filley, Ronald F Turco, Hui LiAbstract:Soil microorganisms secrete enzymes used to metabolize carbon (C), nitrogen (N), and phosphorus (P) from the organic materials typically found in Soil. Because of the connection with the active microbial biomass, Soil enzyme activities can be used to investigate microbial nutrient cycling including the microbial response to environmental changes, transformation rates and to address the location of the most active biomass. In a 9-year field study on global change scenarios related to increasing N inputs (ambient to 15 g N m � 2 yr � 1 ) and precipitation (ambient to 180 mm yr � 1 ), we tested the activities of Soil bglucosidase (BG), N-acetyl-glucosaminidase (NAG) and acid phosphomonoesterase (PME) for three Soil aggregate classes: large macroAggregates (>2000 mm), small macroAggregates (250e2000 mm) and microAggregates (<250 mm). Results showed higher BG and PME activities in micro-vs. small macroAggregates whereas the highest NAG activity was found in the large macroAggregates. This distribution of enzyme activity suggests a higher contribution of fast-growing microorganisms in the micro-compared with the macroAggregates size fractions. The responses of BG and PME were different from NAG activity under N addition, as BG and PME decreased as much as 47.1% and 36.3%, respectively, while the NAG increased by as much as 80.8%, which could imply better adaption of fungi than bacteria to lower Soil pH conditions developed under increased N. Significant increases in BG and PME activities by as much as 103.4 and 75.4%, respectively, were found under water addition. Lower ratio of BG:NAG and higher NAG:PME underlined enhanced microbial N limitation relative to both C and P, suggesting the repression of microbial activity and the accompanied decline in their ability to compete for N with plants and/or the accelerated proliferation of Soil fungi under elevated N inputs. We conclude that changes in microbial activities under increased N input and greater water availability in arid- and semi-arid grassland ecosystems where NPP is co-limited by N and water may result in substantial redistribution of microbial activity in different-sized Soil particles. This shift will influence the stability of SOM in the Soil Aggregates and the nutrient limitation of Soil biota.
Ruzhen Wang - One of the best experts on this subject based on the ideXlab platform.
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base cations and micronutrients in Soil Aggregates as affected by enhanced nitrogen and water inputs in a semi arid steppe grassland
Science of The Total Environment, 2017Co-Authors: Ruzhen Wang, Jennifer A J Dungait, Heather L Buss, Shan Yang, Yuge Zhang, Zhuwen Xu, Yong JiangAbstract:Abstract The intensification of grassland management by nitrogen (N) fertilization and irrigation may threaten the future integrity of fragile semi-arid steppe ecosystems by affecting the concentrations of base cation and micronutrient in Soils. We extracted base cations of exchangeable calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na) and extractable micronutrients of iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) from three Soil aggregate sizes classes (microAggregates, 2 mm) from a 9-year N and water field manipulation study. There were significantly more base cations (but not micronutrients) in microAggregates compared to macroAggregates which was related to greater Soil organic matter and clay contents. Nitrogen addition significantly decreased exchangeable Ca by up to 33% in large and small macroAggregates and exchangeable Mg by up to 27% in three Aggregates but significantly increased extractable Fe, Mn and Cu concentrations (by up to 262%, 150%, and 55%, respectively) in all aggregate size classes. However, water addition only increased exchangeable Na, while available Fe and Mn were decreased by water addition when averaging across all N treatments and aggregate classes. The loss of exchangeable Ca and Mg under N addition and extractable Fe and Mn in Soil Aggregates under water addition might potentially constrain the productivity of this semi-arid grassland ecosystem.
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carbon and nitrogen dynamics in Soil Aggregates under long term nitrogen and water addition in a temperate steppe
Soil Science Society of America Journal, 2015Co-Authors: Ruzhen Wang, Jennifer A J Dungait, Yuge Zhang, Zhuwen Xu, Courtney A Creamer, Bo Li, Yong JiangAbstract:Anthropogenic-driven changes in N and water availability are two of the most important factors determining Soil C and N turnover in temperate grassland ecosystems. To gain insight into changes in Soil aggregation and C and N dynamics in response to N and water addition, we collected Soil samples from a field study conducted for 9 yr in a semiarid steppe grassland in Inner Mongolia, China. Three aggregate size classes (microAggregates, 2000 μm) were isolated and analyzed for their mass proportions, Soil organic C (SOC), total N (TN), total extractable inorganic N (TIN), and stable isotope ratio of 13C relative to 12C (δ13C) and stable isotope ratio of 15N relative to 14N (δ15N) values. Water addition on average increased large macroAggregates by 33% and decreased microAggregates by 42%. Nitrogen and water addition interacted significantly and increased TIN concentration but had no impact on SOC or TN. Soil organic C was negatively correlated with δ13C values of large and small macroAggregates under ambient precipitation and within all Soil Aggregates under water addition. Significant positive correlations between TIN and δ15N values were detected for large macroAggregates and microAggregates under ambient precipitation. Our results suggest that water addition accelerated plant residue incorporation into Soil organic matter (SOM) (indicated by depleted 13C values) while N addition potentially increased gaseous N losses (suggested by 15N enrichment without changing Soil C and N concentrations). Water, but not N, improved Soil structure in this semiarid grassland. Our study provides new insights for using natural abundance 13C and 15N to better understand the sensitivity of SOM within different Soil particles to coupled N–water changes under global change scenarios.
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responses of enzymatic activities within Soil Aggregates to 9 year nitrogen and water addition in a semi arid grassland
Soil Biology & Biochemistry, 2015Co-Authors: Ruzhen Wang, Shan Yang, Yuge Zhang, Zhuwen Xu, Maxim Dorodnikov, Yongyong Zhang, Timothy R Filley, Ronald F Turco, Hui LiAbstract:Soil microorganisms secrete enzymes used to metabolize carbon (C), nitrogen (N), and phosphorus (P) from the organic materials typically found in Soil. Because of the connection with the active microbial biomass, Soil enzyme activities can be used to investigate microbial nutrient cycling including the microbial response to environmental changes, transformation rates and to address the location of the most active biomass. In a 9-year field study on global change scenarios related to increasing N inputs (ambient to 15 g N m � 2 yr � 1 ) and precipitation (ambient to 180 mm yr � 1 ), we tested the activities of Soil bglucosidase (BG), N-acetyl-glucosaminidase (NAG) and acid phosphomonoesterase (PME) for three Soil aggregate classes: large macroAggregates (>2000 mm), small macroAggregates (250e2000 mm) and microAggregates (<250 mm). Results showed higher BG and PME activities in micro-vs. small macroAggregates whereas the highest NAG activity was found in the large macroAggregates. This distribution of enzyme activity suggests a higher contribution of fast-growing microorganisms in the micro-compared with the macroAggregates size fractions. The responses of BG and PME were different from NAG activity under N addition, as BG and PME decreased as much as 47.1% and 36.3%, respectively, while the NAG increased by as much as 80.8%, which could imply better adaption of fungi than bacteria to lower Soil pH conditions developed under increased N. Significant increases in BG and PME activities by as much as 103.4 and 75.4%, respectively, were found under water addition. Lower ratio of BG:NAG and higher NAG:PME underlined enhanced microbial N limitation relative to both C and P, suggesting the repression of microbial activity and the accompanied decline in their ability to compete for N with plants and/or the accelerated proliferation of Soil fungi under elevated N inputs. We conclude that changes in microbial activities under increased N input and greater water availability in arid- and semi-arid grassland ecosystems where NPP is co-limited by N and water may result in substantial redistribution of microbial activity in different-sized Soil particles. This shift will influence the stability of SOM in the Soil Aggregates and the nutrient limitation of Soil biota.
Pedro M Antunes - One of the best experts on this subject based on the ideXlab platform.
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mycelium of arbuscular mycorrhizal fungi increases Soil water repellency and is sufficient to maintain water stable Soil Aggregates
Soil Biology & Biochemistry, 2010Co-Authors: Matthias C Rillig, Noor F Mardatin, Eva F Leifheit, Pedro M AntunesAbstract:Using an in vitro bioreactor system in which the arbuscular mycorrhizal (AM) fungus Glomus intraradices was grown in a Soil devoid of detectable living microbes, we could show that the mycelium of this fungus contributed to the maintenance of water-stable Soil Aggregates and increased Soil water repellency, as measured by water drop penetration time. This is to our knowledge the first demonstration of a causal link between AM fungal growth and water repellency of Soil Aggregates. Our results also place AM fungal contributions to Soil aggregation on a firm mechanistic footing by showing that hyphae are sufficient to produce effects, in the absence of other Soil biota, which have always been included in previous studies.
Paul D Hallett - One of the best experts on this subject based on the ideXlab platform.
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water repellency and distribution of hydrophilic and hydrophobic compounds in Soil Aggregates from different tillage systems
Geoderma, 2007Co-Authors: Emilia Urbanek, Paul D Hallett, Debbie S Feeney, Rainer HornAbstract:Water repellency properties of individual Soil Aggregates offer increased reduction of carbon (C) mineralization within Soils. These studies explore the spatial distributions of C and groupings of C–H and Cdouble bond; length as m-dashO compounds at multiple Soil depths, on surfaces and within multiple sized Soil Aggregates. Measurements were conducted on Soil Aggregates, sampled from three horizons in a silty loam Anthrosol under long term grassland pastures and short term conservation tillage wheat and in a silty loam Luvisol subjected to long term conventional tillage of maize. Soil Aggregates were fractionated into seven size classes by dry sieving and single Aggregates were mechanically separated into external, transitional and interior regions by Soil aggregate erosion (SAE) chambers. Soil materials from different aggregate-size classes and aggregate layers were evaluated for total C and nitrogen (N) contents. Functional hydrophobic and hydrophilic groups in each of these Soils were identified by DRIFT spectrometry. Water repellency was identified on the surfaces of different size-class Aggregates and each of their interior regions by the ethanol/water sorptivity method. Total organic C contents within individual Aggregates and size classes varied considerably and were influenced by Soil depths and management practices. Whole microAggregates had greater C contents than macroAggregates. Total organic C content was highly correlated to hydrophobic (C–H) groups (R2 = 0.78), but not hydrophilic groups. External surfaces of Aggregates from no tilled Soils of wheat and grass exhibited the largest gradients of hydrophobic C–H groups when compared to their interiors. More hydrophilic Cdouble bond; length as m-dashO groups were observed in maize and grassland biomes where plant biomass was greater. Although highly variable, the largest gradients of Cdouble bond; length as m-dashO groups were measured in the Ap and Ah horizons of maize and grasslands. Water repellency indices were greater in aggregate sizes ranging from 8 to 5 mm for agricultural Soil management systems and were similar for most aggregate sizes measured for grasslands. Soil aggregate water repellency appears to be controlled by the uniform distribution of these compounds at surfaces of all Soil aggregate-size fractions and possibly by the concentrations of hydrophobic compounds on surfaces of Aggregates at multiple Soil depths. Further inquires into the mechanisms controlling Soil wetting require more than a quantification of total organic C. These studies demonstrated spatial interactions between the locations and quantities of hydrophobic and hydrophobic compounds distributed among Soil aggregate-size fractions located within the Soil profile.
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changes to water repellence of Soil Aggregates caused by substrate induced microbial activity
European Journal of Soil Science, 1999Co-Authors: Paul D Hallett, Iain M YoungAbstract:Summary Soil microbes produce exudates which upon drying become water-repellent, thus altering hydraulic properties. The influence of microbial activity caused by adding plant nutrients on the hydraulic characteristics of Soil Aggregates is reported. Soil Aggregates were collected from a field that had been fertilized with different amounts of nitrogen. Aggregates were also incubated with different nutrient treatments in the laboratory. Their sorptivity, hydraulic conductivity and water repellency were measured with a new device. Adding nitrogen was found to decrease sorptivity and hydraulic conductivity because of increased water repellency in the field. In the laboratory studies, the addition of nutrients caused severe water repellency in the Soil Aggregates. Respiration studies identified a large increase in biological activity following nutrient amendment which produces water-repellent materials.