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Developing sustainable materials for recovering and recycling nutrients from wastewater is critically needed for nutrients such as phosphorus that have a diminishing supply. Struvite crystallization is emerging as a promising strategy for phosphorus recovery which can be enhanced with seeding through microalgal biochar. The main bottleneck of using microalgae is its high harvesting cost. In this study, an integrated electrocoagulation-flotation (ECF) process is used to recover and at the same time modify the algal surface with magnesium anode and inert carbon cathode. Harvesting efficiency of 98% was achieved with 40.78 mA cm−2, 0.5 cm inter-electrode distance and energy consumption of 4.03 kWh kg−1 in 15 min. The harvested microalgae were pyrolyzed to obtain a yield of 52.90% Mg-laden microalgal biochar. Simultaneously, surface impregnation of 28% magnesium was attained as confirmed by Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Phosphorus recovery and struvite yield of 93.70% and 2.66 g L−1, respectively, were obtained from dosing 1.50 g L−1 Mg-laden microalgal biochar. Comparison of physicochemical characteristics of residual supernatant after microalgal harvesting and struvite recovery showed that the combined use of both the residuals can serve as a sustainable growth medium for microalgae. The overall operating cost of the integrated process was found to be 2.48 USD kg−1 with a total energy consumption of 10.76 kWh kg−1, which was found to be lower than conventional harvesting unit processes such as centrifugation and filtration. This novel approach can help attaining a circular bioeconomy by encompassing nutrient recovery and waste management in an integrated process. [ABSTRACT FROM AUTHOR]

Background and Aims: Roots are of critical importance to plants due to their role in absorbing soil water and nutrients and adapting to ever-changing environmental conditions. Grazing changes plant and soil conditions and can affect root growth and resource utilization strategies. However, it is still unclear how grazing intensity affects plant root traits in desert steppes, especially by altering soil resource availability. Methods: Here, we studied the effect of four levels of grazing intensity, including no grazing (CK), light grazing (LG), moderate grazing (MG), and heavy grazing (HG), on the root traits of Stipa breviflora and soil physical, chemical, and microbial properties in a desert steppe dominated by S. breviflora under in Siziwang Banner, Inner Mongolia, China. Results: Compared to the CK treatment, all grazing treatments significantly reduced root diameter, and increased root length density and root-to-shoot ratio, but did not affect root nitrogen concentration and tissue density. The light grazing treatment significantly increased the root fractal dimension, root fractal abundance, and root biomass. The heavy grazing treatment significantly increased specific root length and root fractal abundance. Principal component analysis revealed that grazing influenced the root-mycorrhizal "collaboration" gradient, shifting root resources utilization strategies from "outsourcing" in the CK to "do-it-yourself" in the grazed plots. Structural equation modeling showed that shifts in root traits were mainly associated with changes in soil pH, ammonium nitrogen availability, and microbial diversity under grazing. Conclusions: Under increasing grazing intensity, S. breviflora adapted to higher soil pH and lower nitrogen availability by producing longer, thinner, more branching roots and a "do-it-yourself" strategy. Our results suggest that changes in root traits play a very important role in the adaption of a dominant desert steppe plant to grazing intensity. [ABSTRACT FROM AUTHOR]

Grassland plants, especially their root systems, are dynamic and can buffer changes resulting from exposure to multiple stressors; however, the interactive stressor effects on root dynamics and associated above‐ground growth are poorly understood.Here, we examine the effects of changed precipitation and air temperature, and defoliation intensity on root length dynamics and above‐ground biomass using the third year data from a multifactor experiment conducted across three northern temperate grasslands.We found that root length was more sensitive to the changes in environmental and management conditions than root mass, demonstrating the importance of root length as an indicator of rapid root system changes. Across all sites, warming, altered precipitation and defoliation intensity interacted to affect root length while above‐ground biomass was only affected by defoliation intensity, indicating that the root system was more responsive than above‐ground biomass when climatic conditions change. Overall, drought reduced root length, particularly under low defoliation intensity, as well as in combination with warming and heavy defoliation, highlighting the risk of additive effects of such environmental stresses. Across unclipped plots, above‐ground biomass was positively associated with total root length, the latter of which further interacted with precipitation, to affect above‐ground biomass. Compared to defoliated communities, non‐defoliated plant communities exhibited a greater ability to maintain above‐ground biomass under drought conditions via increases in root system efficiency (the amount of above‐ground biomass produced per unit of root length invested).Our results highlight the rapid change of root length in the face of interactive stressors. We postulate that the degree of stability in above‐ground biomass is driven by the altered root system dynamics or species turnover. Future studies are warranted that more directly assess how root length responses under climate change impact other important plant traits in grasslands. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Abstract Application of biochars produced by pyrolyzing organic residues to cropland has been proposed to be an effective approach to better use of organic residues, decrease soil greenhouse gas emission and increase soil fertility. However, the effect of biochar application on processes occurring in the bulk soil vs that in the rhizosphere is poorly understood. This study investigated the effects of manure pellet and woodchip biochars, as compared to that of unpyrolyzed (raw) manure pellet and woodchip, on plant grain yield, and soil respiration in the bulk and rhizosphere soils in a greenhouse experiment using the rhizobox technique. The raw manure pellet and woodchip and their biochars were applied to the soil at the rate of 57 t ha−1 and spring wheat (Triticum aestivum L. var. GP168) was grown in the rhizosphere compartment of the rhizobox. Soil amendment with raw manure pellet and its biochar significantly increased plant grain yield by 36.3 and 16.1%, as compared to the control (without amendment), while raw woodchip and its biochar applications significantly decreased plant grain yield. Manure pellet and woodchip biochars significantly reduced soil respiration from the rhizosphere by 24.6 and 29.7%, respectively, relative to the control, but not that from the bulk soil (P > 0.05). Relativized cumulative CO 2 emission was significantly reduced by both manure pellet and woodchip biochars from rhizosphere and bulk soils. Dissolved organic carbon and nitrogen were increased (P < 0.01) in all soil amendment treatments in both bulk and rhizosphere soils, but microbial biomass carbon and nitrogen in the rhizosphere soil were reduced by manure pellet biochar application. We conclude that biochars produced from organic residues have differential impacts on processes in bulk and rhizosphere soils, and thus measurements based on bulk soil alone may result in erroneous conclusions about the effect of biochars on soil CO 2 emission. Graphical abstract Unlabelled Image Highlights • CO 2 emission from bulk and rhizosphere soils was studied using rhizobox technique. • Biochars reduced CO 2 emission from rhizosphere but not from bulk soil. • Manure pellet biochar increased but woodchip biochar decreased wheat grain yield. • MBC decreased in rhizosphere but increased in bulk soil by manure pellet biochar. [ABSTRACT FROM AUTHOR]

Aims: Nitrogen (N) addition could affect litter decomposition through its direct effects on soil N availability and indirect effects on initial litter chemistry. The aim of this study was to evaluate the relative contribution of these direct and indirect effects to the decomposition of fine roots with different diameter classes.Methods: A two-year reciprocal replant-transplant field experiment was conducted in a Mongolian pine (Pinus sylvestris var. mongolica) plantation to examine the relative effect of exogenous and endogenous N enrichment induced by N addition (10 g N m−2 yr.−1) on the decomposition of fine roots with different diameter classes: < 0.5 mm (small fine root, SFR) and 0.5-2 mm (large fine root, LFR).Results: The LFR had significantly higher decomposition rates (k: 0.315-0.397 yr.−1) than the SFR (0.245-0.274 yr.−1) after 2 years of incubation. Exogenous N (i.e., increased soil N availability due to N addition) had no significant effect on the decomposition rates of fine roots, whereas endogenous N (i.e. increased N concentration in litter due to N addition) inhibited and accelerated the decomposition of SFR and LFR, respectively. Endogenous N decreased the net release of N but both endogenous and exogenous N increased the net release of phosphorus (P) from SFR. By contrast, exogenous and endogenous N decreased the net release of N and P from LFR.Conclusions: Our results suggest that N addition affected fine root decomposition indirectly by changing the chemical traits of fine roots rather than directly through changing soil N availability. Elevated input and decreased net N release of fine roots might be a potential mechanism explaining the increases of total organic carbon and total N in the semi-arid forest soil under N addition. Our study also suggests that SFR may be a more important source of stable soil organic matter relative to LFR. [ABSTRACT FROM AUTHOR]

Soil microorganisms play critical roles in maintaining ecological functions of the northern mixed-grass prairie. While defoliation regimes and elevated precipitation affect plant community composition and primary productivity in these grasslands, their effects on soil microbiome and interactome have not been studied. We examined the response of soil microbiome and interactome to long-term (2010–2015) treatments of varying defoliation regimes (low vs. high intensity and low vs. high frequency) and two precipitation conditions (ambient vs. elevated) on two contrasting sites (a dry vs. a mesic site) in a northern mixed-grass prairie. High intensity defoliation reduced alpha-diversity and altered the beta-diversity of soil microbial communities in the mesic site but not in the dry site, while elevated precipitation reduced alpha-diversity and altered the beta-diversity of soil microbial communities in both sites. Defoliation and precipitation did not show interaction effects on overall alpha- and beta-diversity, but did combine to influence the interactome network. High intensity defoliation promoted the oligotrophic genera Spartobacteria (Verrucomicrobia), Pseudonocardia (Actinobacteria), and Conexibacter (Actinobacteria), while elevated precipitation promoted the copiotrophic genera Nitrososphaera (Thaumarchaeota), Anderseniella (Proteobacteria), Sphingomonas (Proteobacteria), and Acidobacteria Gp16 (Acidobacteria). High intensity defoliation increased the number of linkages for Alphaproteobacteria and Acidobacteria, and decreased the number of linkages for Gemmatimonadetes and Spartobacteria in the interactome networks. However, elevated precipitation increased the number of linkages for Actinobacteria and Gemmatimonadetes and decreased the number of linkages for Spartobacteria and Acidobacteria. Our results show that defoliation intensity and elevated precipitation affected the microbiome and associated interactome network within soils of the northern mixed-grass prairie by affecting different functional taxonomic groups, indicating distinct scenarios for defoliation and precipitation in affecting soil microbial communities. [ABSTRACT FROM AUTHOR]

More livestock is being raised globally (increasing from 3.55 billion in 2000 to 4.24 billion in 2014 for cattle, sheep, goats and horses, based on 2017 FAO data) due to the increasing demand for livestock products, which inevitably results in increased excreta (urine and dung) deposition onto grasslands. Urine and dung patches are hotspots for emissions of the three principal greenhouse gases (GHGs): nitrous oxide (N 2 O), methane (CH 4 ) and carbon dioxide (CO 2 ) from grazed grasslands; however, the underlying mechanisms controlling GHG emissions are still not well understood and few strategies have been developed to mitigate such GHG emissions. Here, we review research on GHG emissions from excreta patches and propose possible mitigation strategies. The emission of N 2 O from excreta patches is mainly caused by increased nitrification and denitrification, in association with the increased abundance of ammonia-oxidizing bacteria (AOB) and denitrifying bacteria. Emission of N 2 O increases after urine deposition regardless of the type of urine (net increases ranged from 1.06 to 6.51 kg N ha − 1 ), while it increases (2.42 ± 1.95 kg N ha − 1 ; mean ± 95% confidence interval) only after cattle dung deposition, which also increases CH 4 (11.8 ± 5.32 kg C ha − 1 ) and CO 2 (893 ± 693 kg C ha − 1 ) emissions. The effect of urine on CH 4 emission is complex and further research is required. The application of dicyandiamide (DCD) is effective in reducing N 2 O emissions from both cattle urine (− 4.24 ± 1.10 kg N ha − 1 ) and dung (− 0.66 ± 0.61 kg N ha − 1 ) patches. In urine patches, DCD can reduce AOB population size, but does not influence the denitrifying bacteria population size. Diet manipulation and grazing management are also potential measures for mitigating GHG emissions from excreta patches. Further research is required to ascertain the overall emission of GHGs from excreta patches at the ecosystem level and to explore strategies for the sustainable development of grazed grassland ecosystems. [ABSTRACT FROM AUTHOR]

Methane (CH 4 ) production in soils can occur by microbial and non-microbial processes. We postulated that there exist the mixed microbial and non-microbial CH 4 emissions from fresh soils in nature. To test both emissions and their importance, this study examined CH 4 releases from fresh soils of forest, orchard, croplands, grasslands, and wetland. By designing the treatments with or without inhibitor(s) in the laboratory conditions, we used inhibition method to compare/distinguish microbial and non-microbial CH 4 releases from fresh soils at a series of temperatures. Microbial CH 4 release occurred mainly in wetland soils and moist upland soils, with the peak rates of 10 1 –10 3 ng gdw − 1 h − 1 around 40 °C. Non-microbial CH 4 release occurred mainly in upland soils and usually increased with temperature, showing negligible rates at ambient temperatures of 0–40 °C and detectable rates of approximately 0.2–0.7 ng gdw − 1 h − 1 at high temperatures of 50–70 °C. Microbial CH 4 release was much more important than non-microbial CH 4 release from fresh soils at different temperatures, when all land uses were considered together. In nature, soils are frequently exposed to various forms of environmental stress. Besides temperature fluctuation examined in the present study, solar ultraviolet radiation, soil water deficit and flooding, hypoxia and hyperoxia, tillage, and herbicide may also affect non-microbial CH 4 production. Thus, more measurements are required for understanding the contribution of non-microbial CH 4 emission to the total from soils. [ABSTRACT FROM AUTHOR]

The losses of soil organic carbon (SOC) in orchards are more intensive than those of cereal production and result from poor orchard management. Grass cover in orchards is an optimal approach to enhance the sequestration of SOC that has been shown to improve the biological properties of soil. China has the largest area of orchards and the highest production of fruit in the world. However, a quantitative assessment of soil biological properties in orchards in response to grass cover across China is lacking. In this study, a meta-analysis was conducted based on data collected from 103 peer-reviewed publications to evaluate the effect of grass cover on microbial abundance and enzyme activities, which were primarily invertase, urease, phosphatase and polyphenol oxidase, in the 0–40 cm soil layer and to assess the spatial and temporal variations of those parameters in orchards. The results indicated that the grass cover increased the microbial biomass carbon; abundances of bacteria, fungi, and actinobacteria; and microbial diversity (Shannon index) by 52.6 %, 61.2 %, 78.7 %, 47.3 %, and 9.4 %, respectively, compared with orchards without grass cover. The grass had been removed by clean tillage. A grass cover also increased activities of invertase, urease, acid phosphatase, alkaline phosphatase, catalase, and cellulase by 26.0 %, 27.0 %, 15.1 %, 26.6 %, 11.9 %, and 71.0 %, respectively. These changes varied with the traits of cover grass, such as grass source and nitrogen fixation; climatic conditions, such as mean annual temperature and precipitation; edaphic variables, such as soil pH, soil texture, and soil sampling season; and management practices, such as orchard age, duration of grass cover, and grass sowing mode. Additionally, we provided a scientific basis to bridge the knowledge of soil nutrients, soil microbes, enzyme activities, SOC contents, and fruit yield in grass-covered orchards. Therefore, given the traits of cover grass, climate, soil, and managerial conditions, the data from this study has valuable implications for the site-specific management of grass coverage and sustainable orchard production. • Grass coverage increased microbial biomass carbon, Shannon index, and microbial abundance. • Grass coverage increased soil extracellular enzyme activities • Biological properties with grass cover varied with grass traits\management, climate, soils. • Summarized potential mechanisms of enhanced soil biological properties [ABSTRACT FROM AUTHOR]

Forest floor mineral soil mix (FMM) and peat mineral soil mix (PMM) are cover soils commonly used for reclamation of open-pit oil sands mining disturbed land in northern Alberta, Canada; coarse woody debris (CWD) is another source of organic matter for land reclamation. We investigated net nitrogen (N) transformation rates in FMM and PMM cover soils near and away from CWD 4-6 years after oil sands reclamation. Monthly net nitrification and N mineralization rates varied over time; however, mean rates across the incubation periods and microbial biomass were greater (p<0.05) in FMM than in PMM. Net N mineralization rates were positively related to soil temperature (p<0.001) and microbial biomass carbon (p=0.045). Net N transformation rates and inorganic N concentrations were not affected by CWD; however, the greater 15N isotope ratio of ammonium near CWD than away from CWD indicates that CWD application increased both gross N mineralization/nitrification (causing N isotope fractionation) and gross N immobilization (no isotopic fractionation).Microbial biomass was greater near CWD than away from CWD, indicating the greater potential for N immobilization near CWD. We conclude that (1)CWDapplication affected soil microbial properties andwould create spatial variability and diversemicrosites and (2) cover soil type and CWD application had differential effects on net N transformation rates. Applying FMM with CWD for oil sands reclamation is recommended to increase N availability and microsites. [ABSTRACT FROM AUTHOR]

Peat mineral soil mix (PMM) and forest floor mineral soil mix (FMM) are cover soils commonly used for land reclamation, while coarse woody debris (CWD) can be added to create structural diversity and provide an additional source of organic matter. However, the effect of cover soil type and CWD on emission rates of greenhouse gases, such as carbon dioxide (CO 2 ) methane (CH 4 ) and nitrous oxide (N 2 O) in reclaimed oil sands soils has not been studied. Soil respiration, CH 4 uptake and N 2 O emission rates were studied in a factorial experiment consisting of 2 cover soils (FMM vs PMM) × 2 sampling distances from the CWD (near vs away from CWD). Greenhouse gas emission rates were measured in July, August, and September 2012 and 2013 using static chambers. Soil respiration rates were greater in FMM than in PMM regardless of the distance from CWD at each sampling time ( p < 0.05). Rates ranged from 461 to 1148 and 293 to 677 mg CO 2 m −2 h −1 for FMM and PMM, respectively, in 2012, and from 355 to 1318 and 235 to 700 mg CO 2 m −2 h −1 , respectively, in 2013. The CWD increased soil respiration by 22–33% in FMM but not in PMM. Soil respiration rates were positively related to microbial biomass carbon ( p = 0.004) and nitrogen ( p < 0.001). Soil respiration rates decreased from July to September in 2012 and 2013, and were positively related to soil temperature ( p < 0.01) but not with soil water content measured at 5 cm depth. Methane uptake rates were greater in FMM (0.026–0.037) than in PMM (0.015–0.028 mg CH 4 m −2 h −1 ). The CWD increased CH 4 uptake rates only in July and August 2012 in FMM, and were negatively related to soil water content ( p < 0.001) but not to soil temperature. Nitrous oxide emission rates (0.001–0.016 mg N 2 O m −2 h −1 ) were not affected by either cover soil type or CWD. Global warming potential of CO 2 , CH 4 and N 2 O effluxes was greater in FMM than in PMM and near CWD than away from CWD, especially in FMM. Our study demonstrates that applying CWD for oil sands reclamation increases organic matter decomposition (increased CO 2 evolution), driven by the effect on microbial populations. Results from this study provide support to findings in earlier studies that CWD application benefits vegetation establishment through enhancing soil processes in reclaimed oil sands lands. [ABSTRACT FROM AUTHOR]

Agroforestry systems are common land uses across Canada and could play a substantial role in sequestering carbon (C) as part of efforts to combat climate change. We studied the impact of component land cover types (forested vs. adjacent herbland) in three agroforestry systems (hedgerow, shelterbelt and silvopasture) on organic C and nitrogen (N) distribution in three density fractions of soils at the 0–10 and 10–30 cm layers. The study evaluated 36 sites (12 hedgerows, 12 shelterbelts and 12 silvopastures) in central Alberta, Canada, distributed along a soil/climate gradient of increasing moisture availability. At the 0–10 cm layer, soil organic C (SOC) stock in the bulk soil was significantly greater in the silvopasture system (101) than in either the hedgerow (77) or shelterbelt system (67 Mg C ha −1 ). Soil organic C stock in both soil layers (0–10 and 10–30 cm) was also significantly greater in the forested land cover (89 and 119 Mg C ha −1 , respectively) than in adjacent herblands (76 and 77 Mg C ha −1 ). Across all sites, 31.5, 29.1, and 35.5% of SOC was found in the light fraction (<1.6 g cm −3 ), occluded fraction (ultrasonic dispersion at 360 W for 5 min, <1.6 g cm −3 ), and heavy fraction (>1.6 g cm −3 ) of soils, respectively. The largest pool of SOC in the more labile light fraction of the 0–10 cm layer was in the silvopasture system (50 Mg C ha −1 ), whereas the smallest labile light fraction component of SOC was in the shelterbelt system (17 Mg C ha −1 ). The largest pool of SOC in the more stable heavy fraction of both the 0–10 and 10–30 cm depth classes was in the shelterbelt (33 and 35 Mg C ha −1 , respectively), while the least SOC was in the silvopasture system (26 and 20 Mg C ha −1 , respectively). We conclude that the presence of Populus based silvopasture system can increase C storage in surface mineral soils, and that the establishment of Picea based shelterbelts in an otherwise annually cropped agricultural landscape enhances the size of the stable SOC pool. [ABSTRACT FROM AUTHOR]

Forest floor mineral soil mix (FMM) and peat mineral soil mix (PMM) are cover soils commonly used for upland reclamation post open-pit oil sands mining in northern Alberta, Canada. Coarse woody debris (CWD) can be used to regulate soil temperature and water content, to increase organic matter content, and to create microsites for the establishment of microorganisms and vegetation in upland reclamation. We studied the effects of CWD on soil microbial community level physiological profile (CLPP) and soil enzyme activities in FMM and PMM in a reclaimed landscape in the oil sands. This experiment was conducted with a 2 (FMM vs PMM) × 2 (near CWD vs away from CWD) factorial design with 6 replications. The study plots were established with Populus tremuloides (trembling aspen) CWD placed on each plot between November 2007 and February 2008. Soil samples were collected within 5 cm from CWD and more than 100 cm away from CWD in July, August and September 2013 and 2014. Microbial biomass was greater (p<0.05) in FMM than in PMM, in July, and August 2013 and July 2014, and greater (p<0.05) near CWD than away from CWD in FMM in July and August samplings. Soil microbial CLPP differed between FMM and PMM (p<0.01) according to a principal component analysis and CWD changed microbial CLPP in FMM (p<0.05) but not in PMM. Coarse woody debris increased microbial community functional diversity (average well color development in Biolog Ecoplates) in both cover soils (p<0.05) in August and September 2014. Carbon degrading soil enzyme activities were greater in FMM than in PMM (p<0.05) regardless of distance from CWD but were not affected by CWD. Greater microbial biomass and enzyme activities in FMM than in PMM will increase organic matter decomposition and nutrient cycling, improving plant growth. Enhanced microbial community functional diversity by CWD application in upland reclamation has implications for accelerating upland reclamation after oil sands mining. [ABSTRACT FROM AUTHOR]

Low nitrogen (N) availability may affect lodgepole pine ( Pinus contorta , Pl) and white spruce ( Picea glauca , Sw) growth in some reconstructed boreal forest soils in the Athabasca oil sands region in Alberta, Canada. The objective of this study was to investigate the effect of fertilization (N alone or complete fertilizer) on foliar nutrient concentrations in and growth of Pl (planted in soils with tailings sand as a substrate) and Sw (planted in soils with overburden material as a substrate) in a single-tree fertilization study. Two growing seasons after fertilization, both N alone and complete fertilizer treatments increased the height, diameter at breast height and aboveground biomass growth of Sw ( p = 0.005, 0.009 and 0.015, respectively). In contrast, fertilization did not affect Pl growth. Foliar N concentration and content in current-year needles of Sw were higher following fertilization than in the control treatment in 2012 ( p < 0.001 for both), but not in 2013. Foliar δ 15 N in current-year and 1-year-old needles was greater in the fertilization than in the control treatment for Sw ( p < 0.001 for both), in association with the increase of δ 15 N in soil NO 3 − -N. No fertilization effect on foliar micronutrients (Fe, Mn, Cu, Zn, B and Mo) or soil NH 4 + -N, NO 3 − -N or dissolved organic N was found in either Pl or Sw sites. We conclude that N was a limiting factor for tree growth in Sw but not in Pl sites and that N fertilization may be used to improve Sw growth in some reclaimed sites with overburden as a substrate in the oil sands region. [ABSTRACT FROM AUTHOR]

Forest floor mineral soil mix (FMM) and peat mineral soil mix (PMM) are common cover soils and sources of organic matter for reclamation of open-pit mining disturbed land in the Athabasca oil sands region. Coarse woody debris (CWD) can be an additional source of organic matter and can provide nutrient and habitat for plant growth. However, the effect of CWD on nitrogen (N) cycling in reclaimed oil sands soils has not been studied. A laboratory incubation experiment was conducted to assess chemical effects of a CWD extract on gross and net N transformation rates in FMM and PMM using the 15 N pool dilution method. The CWD extract was used to simulate CWD leachates (with rainwater as a control) that are produced in the field. The effect of the simulated CWD leachate on the cover soils was studied in a 2 (FMM vs PMM) × 2 (CWD extract vs rainwater addition) factorial design. There was no difference in gross N mineralization rates between FMM and PMM, although net N mineralization rates were greater in FMM than in PMM ( p < 0.001) due to greater NH 4 + immobilization rates in PMM. Gross and net nitrification rates were greater in FMM than in PMM ( p < 0.001). The ratio of gross nitrification to gross NH 4 + immobilization rates (N/IA) was greater in FMM than in PMM ( p < 0.001), as the greater NH 4 + immobilization rates in PMM decreased gross nitrification rates by decreasing NH 4 + availability. Addition of the CWD extract decreased gross ( p < 0.01) and net ( p < 0.001) N mineralization rates, increased ( p < 0.001) NH 4 + immobilization and decreased ( p < 0.001) gross nitrification rates in both cover soils. The N/IA ratios were decreased by the CWD extract addition, indicating that heterotrophic NH 4 + immobilization was superior to autotrophic nitrification due to the high C/N ratio of the CWD extract. We conclude that FMM will have greater N availability for oil sands reclamation than PMM. Leachates from CWD would decrease N availability by decreasing gross N mineralization and nitrification rates and by increasing N immobilization rates. [ABSTRACT FROM AUTHOR]

Open-pit mining activities in the oil sands region of Alberta, Canada, create disturbed lands that, by law, must be reclaimed to a land capability equivalent to that existed before the disturbance. Re-establishment of forest cover will be affected by the production and turnover rate of fine roots. However, the relationship between fine root dynamics and tree growth has not been studied in reclaimed oil sands sites. Fine root properties (root length density, mean surface area, total root biomass, and rates of root production, turnover, and decomposition) were assessed from May to October 2011 and 2012 using sequential coring and ingrowth core methods in lodgepole pine ( Pinus contorta Dougl.) and white spruce ( Picea glauca (Moench.) Voss) stands. The pine and spruce stands were planted on peat mineral soil mix placed over tailings sand and overburden substrates, respectively, in reclaimed oil sands sites in Alberta. We selected stands that form a productivity gradient (low, medium, and high productivities) of each tree species based on differences in tree height and diameter at breast height ( DBH) increments. In lodgepole pine stands, fine root length density and fine root production, and turnover rates were in the order of high > medium > low productivity sites and were positively correlated with tree height and DBH and negatively correlated with soil salinity ( P < 0.05). In white spruce stands, fine root surface area was the only parameter that increased along the productivity gradient and was negatively correlated with soil compaction. In conclusion, fine root dynamics along the stand productivity gradients were closely linked to stand productivity and were affected by limiting soil properties related to the specific substrate used for reconstructing the reclaimed soil. Understanding the impact of soil properties on fine root dynamics and overall stand productivity will help improve land reclamation outcomes. [ABSTRACT FROM AUTHOR]

Species mixtures have been widely reported to increase aboveground productivity; however, how tree species mixtures affect root systems in natural forests remains unclear. We hypothesize that mixtures have a greater fine root length compared to single species‐dominated stands to support their greater productivity.Here, we collected monthly root images from the minirhizotrons installed in 18 stands either dominated by Populus tremuloides, Pinus banksiana, and their mixtures for three years (2015–2017) in post‐fire boreal forests of two stand ages (8 and 34 years old) to test our hypotheses.We found that the fine root length was higher in mixtures than in single species‐dominated stands, and the magnitude of mixture effects was greater in the 34‐ than in the 8‐year‐old stands in the third year. The mixture effects on fine root length revealed a positive relationship with forest net primary productivity. Root length production, which is the growth of new roots within a year, was not affected by tree species mixtures except for the 8‐year‐old stand in 2015. Tree species mixtures did not affect root length turnover. Root length and root biomass were not significantly correlated at stand level.Synthesis. Our results show that tree species mixtures positively affect fine root length, with that positive effect increasing with stand development in the studied natural forests. Our results suggest that the greater root length in species mixtures supported the greater forest productivity in species mixtures as the greater root length benefits plant uptake of nutrients and water. Therefore, conserving tree species diversity has implications for improving forest productivity and carbon sequestration in forest ecosystems. [ABSTRACT FROM AUTHOR]

Biochar from biomass and waste is a valuable component of various urban green infrastructures, including green roofs, permeable pavements, green walls, and green parking lots. Incorporating biochar into substrate mixtures offers numerous benefits, including improved water retention, nutrient availability, plant growth, and carbon sequestration. Moreover, biochar plays a crucial role in stormwater management by effectively retaining and filtering stormwater, reducing runoff, mitigating urban flooding, and improving surface water quality. This study conducted a comprehensive bibliometric analysis and synthesis of the literature to provide a broad perspective of the current understanding of biochar use in green infrastructure projects, focusing on the impact of biochar on soil and environmental quality, water retention, pollutant removal and the overall performance and sustainability of green infrastructure systems. This review also provides a comprehensive synthesis of the potential of biochar in enhancing green infrastructure systems and guiding future research and implementation strategies. The insights provided in this review can guide corporate stakeholders in understanding the benefits, challenges, and applications of biochar in urban green infrastructure management, empowering them to make informed decisions and contribute to the development of sustainable and resilient urban environments aligned with the principles of the UN SDGs and ESG considerations. [ABSTRACT FROM AUTHOR]

The application of biochar to soil is widely recognized as a promising strategy for enhancing the accumulation and stability of soil organic carbon (SOC), which is crucial in mitigating climate change. However, the influence of interactions between plants and biochar on soil microbial communities and their involvement in SOC mineralization and stability remains unclear. This understanding is essential for optimizing carbon (C) sequestration in systems involving plants, soil, and biochar. In this study, employing a 13C natural abundance approach, we investigated the effect of biochar on the maize rhizosphere priming effect (RPE) in paddy soil. We also examined alterations in microbial communities and functional genes related to C degradation and fixation. Over the 99 days of maize growth, biochar application increased RPE and total SOC while decreasing dissolved organic C. It also elevated soil pH, resulting in shifts in fungal and bacterial community structure, favoring oligotrophic species. Fungal and bacterial assemblies were dominated by deterministic and stochastic processes, respectively. While the abundance of fungal guilds varied irregularly, bacterial guilds were uniformly enriched under biochar-plant interactions. Functional traits such as ecoenzymatic activities, bacterial guilds, and functional genes predominantly affected RPE under biochar application. Bacterial functional genes associated with C degradation and fixation were concurrently enhanced with biochar application. Our results indicate that interactions between plants and biochar can enhance native SOC mineralization and accumulation in a short timeframe by modulating functional traits of soil microorganisms, particularly the bacterial community involved in C degradation and fixation. Article Highlights: Biochar application altered rhizosphere priming effects by − 116.96% to + 171.59% during maize growth. Biochar application increased total soil organic carbon and boosted bacterial abundance. Biochar-plant interactions accelerated soil carbon mineralization and accumulation. [ABSTRACT FROM AUTHOR]

Anthropogenic land‐use practices influence ecosystem functions and the environment. Yet, the effect of global land‐use change on ecosystem nitrogen (N) cycling remains unquantified despite that ecosystem N cycling plays a critical role in maintaining food security. Here, we analysed 2430 paired observations globally to show that converting natural to managed ecosystems increases ratios of autotrophic nitrification to ammonium immobilisation and nitrate to ammonium, but decreases soil immobilisation of mineral N, causing increased N losses via leaching and gaseous N emissions, such as nitrous oxide (e.g., via denitrification), resulting in a leaky N cycle. Changing land use from intensively managed to one that resembles natural ecosystems reversed N losses by 108% on average, resulting in a more conservative N cycle. Structural equation modelling revealed that changes in soil organic carbon, pH and carbon to N ratio were more important than changes in soil moisture content and temperature in predicting ecosystem N retention capacities following land‐use conversion and its reversion. The hotspots of leaky N cycles were mostly in equatorial and tropical regions, as well as in Western Europe, the United States and China. Our results suggest that whether an ecosystem exhibits a conservative N cycle after land‐use reversion depends on management practices. [ABSTRACT FROM AUTHOR]

Question Revealing how plant traits vary over disparate spatial scales and how ecological processes mediate such variation is important for understanding plant community assembly. However, to what extent does the distribution of trait variation among ecological scales differ between leaf and wood tissues and between physical and chemical traits? What are the consequences of resource competition and/or habitat filtering on the community assembly with respect to differences between leaf and wood traits, and between physical and chemical traits? Location Subtropical evergreen broad-leaved forests in five sites in the Ningbo area (29°41-50′ N, 121°36-52′ E) in eastern China. Methods Traits of 96 woody plant species were sampled and variation of ten physical- and chemical-based leaf and wood traits were partitioned across six ecological scales (site, plot, species, individual plant, twigs and leaf age) using a linear mixed model. Results From individual plant to site scales, variance partitions were distinct between leaf and wood traits. In leaf tissues, physical and chemical traits showed a consistent pattern, with the majority of variation found among species and individual plants, with little among plots. For wood tissues, the largest variation in physical traits was at the species and individual plant scales, with the largest variation in chemical traits observed at the plot scale. Variance partition was markedly similar within and across species. Conclusion Leaf and wood traits vary differently in relation to ecological scale, suggesting that trait variability is tissue-specific. The large variability of wood traits at the plot scale suggests a strong habitat filtering process. The large variation in leaf traits within plots may reflect niche differentiation across species and the importance of intra-specific variation that affects species co-existence. Our study demonstrated that physical and chemical traits may be independent. These decoupled trait axes may increase the dimensionality of niche space and facilitate species co-existence in forest communities. [ABSTRACT FROM AUTHOR]

Soil texture and its vertical spatial heterogeneity may greatly influence soil hydraulic properties and the distribution of water and solutes in the soil profile; therefore, they are of great importance for agricultural, environmental, and geo-engineering applications such as land reclamation and landfill construction. This paper reviews the following aspects on water and salt dynamics in the presence of a water table: ( i) the effect of soil texture on the extent of upward movement of groundwater in homogenous soils and ( ii) the impact of soil textural layering on water and salt dynamics. For a homogenous soil, the maximum height of capillary rise ( hmax) or the evaporation characteristic length (ECL) is closely related to the soil texture. When the water table is deeper than hmax, water will evaporate at some depth below surface and salts will be retained below the evaporation front, causing the separation of water and salt. For layered soils, flow barriers (capillary and hydraulic barriers) can make the soil hold more water than a nonlayered one. A capillary barrier may work when a fine-textured layer overlies a coarse-textured layer during infiltration or a coarse-textured layer overlies a fine-textured layer during evaporation, and a hydraulic barrier may occur when a poorly permeable layer exists in the soil profile. The extra water held by flow barriers may improve water availability to plants and may at the same time increase salinization and other environmental risks. Under special conditions, such as in seasonally frozen soils with a shallow water table, there is an additional soil salinization incentive caused by freeze-thaw cycles. Above all, further research is needed to understand the complex effects of soil texture and layering on water and salt dynamics, especially in artificial soils such as reclaimed soils with contrasting properties. [ABSTRACT FROM AUTHOR]

Abstract: Non-microbial methane (CH4) production is more pervasive in nature than previously thought, but it has received less attention than microbial CH4 production. Non-microbial CH4 is produced commonly by an instantaneous reaction involving organic compounds under environmental stresses, without enzymatic catalysis by methanogenic archaea. In addition to the widely known sources of non-microbial CH4, i.e., energy usage, biomass burning, and geological emissions, non-microbial CH4 emissions from plants, animals, fungi, soils, and surface waters of oceans have been recently reported. In most ecosystems, microbial and non-microbial CH4 production co-occur and/or alternate depending on the conditions, and thus CH4 emission in terrestrial ecosystems represents a mixture of microbial and non-microbial CH4 production. Global CH4 emission was estimated at 582Tgyr−1 over the 2000–2004 period, where geological sources of non-microbial CH4 were not included. When geological sources are included, total emissions will likely not increase but its partition among the individual sources would change, and emissions of non-microbial CH4 might account for approximately 40% of the global total. This fraction would slightly increase if non-microbial CH4 emissions of plants, animals, fungi and soils in terrestrial ecosystems and surface waters of oceans are considered, although no global estimates for those fractions currently exist. The stable isotope signatures of C and H in CH4 may be a useful tool for identifying the source of CH4. Based on this review of the literature, we conclude that non-microbial CH4 production may occur in any organism or dead organic matter when organic compounds are exposed to environmental stresses. [Copyright &y& Elsevier]

• Used meta -analysis to investigate SOC fractions responses to agricultural practice. • Fertilization increased and tillage decreased SOC fractions, particularly for POC. • cPOC and frPOC were the most sensitive to fertilization and tillage, respectively. • frPOC content decreased the most with increasing temperature and precipitation. • pH and fertilizer type were consistently important moderators to SOC fractions. Soil organic carbon (SOC), as the largest terrestrial carbon pool, plays an important role in global carbon cycling, which is significantly impacted by agricultural practices. However, our ability to accurately detect and predict the impacts of fertilization and tillage on SOC dynamics is still limited. Investigating the effects of fertilization and tillage on different SOC fractions [i.e. mineral-associated organic carbon (MAOC), particulate organic carbon (POC), free POC (frPOC), occluded POC (oPOC), coarse POC (cPOC), and fine POC (fiPOC)]can aid in the understanding of overall SOC accumulation and stabilization. To this end, we evaluated the fertilization and tillage influences on SOC fractions through a global meta -analysis. We also quantified the role of environmental and agronomic factors in modulating these effects. Fertilization increased SOC fractions by mean percent change (MPC)13 %-77 %, while tillage decreased by MPC 4 %-63 %. Among them, cPOC was the most sensitive to fertilization, while frPOC had the highest sensitivity to tillage. MAOC was the least sensitive to both practices. The application of organic fertilizer increased MAOC, SOC, and POC the most (MPC 20 %-77 %), while mineral-organic fertilizer increased frPOC, oPOC, fiPOC, and cPOC the most (MPC 81 %-126 %). Fertilization in alkaline soils with warm and humid (MAT=16–24 °C, MAP>1000 mm) climate could maximally increase SOC contents from various fractions in surface layer (<20 cm depth), particularly when the altitude was 500–1000 m. However, tillage in acidic soils with low temperatures and rainy climate (MAT=8–16 °C, MAP>1000 mm) reduced the contents of SOC fractions the most in deep layer (>40 cm depth), especially at altitudes greater than 2000 m. Whether under fertilization or tillage, POC (occupying 62 %-74 %) consistently contributed more to SOC than MAOC (26 %-38 %). Overall, we suggest that SOC fractions should be prioritized over total SOC when evaluating the effects of site-specific management strategies on carbon sequestration in agricultural lands. [ABSTRACT FROM AUTHOR]

Abstract: We investigated the critical load (CL) and exceedance (EX) of sulfur (S) deposition, temporal changes in soil chemistry, and H+ budget of soils in plots dominated by Pinus banksiana (jack pine) or Populus tremuloides (trembling aspen, aspen) in two acid-sensitive watersheds to assess the risk of soil acidification by S emissions from oil sands mining in the Athabasca oil sands region (AOSR), Canada. The CLs and EXs were determined by two methods: one was based on bulk deposition and the other based on total deposition (as a sum of bulk deposition and interception deposition). The CLs ranged from 223 to 711 molc ha−1 yr−1 based on bulk deposition. Those values were similar to that obtained based on total deposition. However, EXs based on bulk deposition were significantly lower (p < 0.001) than those based on total deposition due to the relative increase of concentrations in interception deposition, indicating that EXs based on bulk deposition only could underestimate the risk of soil acidification in the AOSR. The S deposition did not exceed CLs in the long-term for both methods. The pH in the forest floor increased and available (as the sum of soluble and adsorbed ) in the forest floor and surface mineral soils increased in both jack pine and aspen stands between 2005 and 2010. The H+ budget ranged from −289 to −130 molc ha−1 yr−1 in jack pine stands and from −510 to −371 molc ha−1 yr−1 in aspen stands. Our results suggest that 1) soils in the studied forest stands have recovered from acidification based on the increasing soil pH over time and the negative H+ budget, and 2) the risk of soil acidification should be assessed by CL and EX calculated based on total deposition. [Copyright &y& Elsevier]

Abstract: The spatial variability of soil chemistry and Ca/Al ratios of soil solution and fine roots were investigated in jack pine (Pinus banksiana) and trembling aspen (Populus tremuloides, aspen) stands to assess the impact of chronic acid deposition on boreal forest ecosystems in the Athabasca oil sands region (AOSR) in Alberta, Canada. Available SO4 2− (as the sum of soluble and adsorbed SO4 2−) accumulated in the soil near tree boles of both species, reflecting the influence of canopy intercepted SO4 2−. In jack pine stands, pH and soluble base cation concentrations decreased towards tree boles due to increased SO4 2− leaching; the reverse was found in aspen stands due to deposition of base cations leached from the canopy. As a result, Ca/Al ratios in the soluble fraction in soils near jack pine boles were 5–20 times lower than that near aspen boles. The Ca/Al ratio did not reach the critical limits of 1.0 for soil solution (ranged from 1.0 to 4.1) or 0.5 for fine roots (0.7–7.9) in the studied watersheds. However, Al n+ concentrations in the soil solution ranged from 0.2 to 4.1mgL−1 in NE7 and from 0.1 to 8.5mgL−1 in SM8 that can inhibit the growth of white spruce (Picea glauca) seedlings that commonly succeed aspen in upland sites in the AOSR. We suggest that the spatial variation caused by tree canopies/stems will affect forest regeneration and the effect of acid deposition on forest succession in the AOSR should be further studied. [Copyright &y& Elsevier]

The temperature sensitivity of soil organic C contained in different particle-size fractions is important in the context of global climate change but to date has been poorly studied. We compared the effects of temperature (7, 14, and 21°C) on C mineralization rates in fractionated soils from four land use systems [agriculture, AG; plantation; grassland, GRA; and native aspen (Populus tremuloides Michx.) stand, NAT] in the parkland region of Alberta, Canada, over a 370-d laboratory incubation. Carbon was largely held in the fine (<53 µm) fraction (59%), followed by the medium (53-250 µm, 31%) and coarse (250-2000 µm, 10%) fractions. Across land uses and incubation temperatures, the amount of C mineralized from bulk soil over 370 d ranged between 2 and 9% of initial total organic carbon (Ci), with mineralization rates based on per unit of Ci ranging from 0.4 to 5.8 x 10-4 mg C mg-1 Ci d-1 and mean residence times (MRTs) ranging from 15 to 65 yr. Of the total amount of C mineralized, 77, 14, and 9% came from the coarse, medium, and fine fractions, respectively. The temperature sensitivity (Qt0) of organic C under NAT increased with decreasing particle size, while plantation- and GRA-derived soil organic C showed significantly greater Q10 in the medium and fine fractions only. We conclude that the mineralization potential and temperature sensitivity of soil organic C in the studied land use systems were controlled mainly by organic matter quality and physical protection provided through aggregation and adsorption. [ABSTRACT FROM AUTHOR]

ABSTRACT Drought continues to be a major constraint on cereal production in many areas, and the frequency of drought is likely to increase in most arid and semi-arid regions under future climate change scenarios. Considerable research and breeding efforts have been devoted to investigating crop responses to drought at various levels and producing drought-resistant genotypes. Plant physiology has provided new insights to yield improvement in drought-prone environments. Crop performance could be improved through increases in water use, water-use efficiency (WUE) and harvest index. Greater WUE can be achieved by coordination between photosynthesis and transpiration. Carbon isotope discrimination (Δ13C) has been demonstrated to be a simple but reliable measure of WUE, and negative correlation between them has been used to indirectly estimate WUE under selected environments. New tools, such as quantitative trait loci (QTL) mapping and gene expression profiling, are playing vital roles in dissecting drought resistance-related traits. The combination of gene expression and association mapping could help identify candidate genes underlying the QTL of interest and complement map-based cloning and marker-assisted selection. Eventually, improved cultivars can be produced through genetic engineering. Future efficient and effective breeding progress in cereals under targeted drought environments will come from the integrated knowledge of physiology and genomics. [ABSTRACT FROM AUTHOR]

Abstract: Sequestering C in biomass and soils in hybrid poplar plantations can help mitigate global climate change caused by the rising atmospheric CO2 concentration. However, the impact of the establishment of hybrid poplar plantations on C and N storage and dynamics is poorly understood. We studied the distribution and temporal changes of C and N in soil organic matter (SOM) density fractions in 2-, 5-, 11-, and 13-year-old (age as in 2006) hybrid poplar stands that form a chronosequence by sampling the plantations in both 2004 and 2006. Sodium polytungstate (SPT, density=1.6 g mL-1) was used to fractionate the soil into light (LF, density<1.6 g mL-1), occluded light (LFo, density<1.6 g mL-1) and heavy fractions (HF density>1.6 g mL-1). The results showed that C and N concentrations (g kg-1 of fraction) in the SOM density fractions decreased in the order of LFo>LF>HF, while the C/N ratio was in the order of LF>LFo>HF. The amount of C and N stored in the LF, LFo and HF fractions and bulk soil in the top 10 cm of soil was: 149-504, 70-336, 1380-2876 and 1617-3776 g m-2, respectively, for C, and 6-26, 3-20, 149-271 and 152-299 g m-2, respectively, for N. From 2004 to 2006, C and N storage decreased in the LF and LFo fractions but increased in the HF fraction in the youngest stand. However, stand-age effects were likely muted by high inherent soil variability among the stands. Carbon storage in the light fraction was responsive in the short term to hybrid poplar plantation establishment. [Copyright &y& Elsevier]

How resource availabilities affect the competitiveness of Canada bluejoint grass [Calamagrostis canadensis (Michx.) P. Beauv., hereafter referred to as bluejoint] is poorly understood. Bluejoint is a widespread grass species in boreal forests and competes with tree species such as white spruce [Picea glauca (Moench) Voss] for belowground resources (e.g., soil N and water) when their supply is limited. In this greenhouse-based study, we tested the following hypotheses: (i) bluejoint competition reduces white spruce growth when belowground resource availabilities are limited; (ii) greater N and water availabilities may increase bluejoint competition and its adverse effects on white spruce growth; and (iii) white spruce foliar δ13C and δ15N are affected by soil N and water availabilities and bluejoint competition. A 2 × 2 2 (competition × N availability × water availability) factorial experiment was conducted using pots of planted white spruce seedlings with or without bluejoint. Bluejoint competition reduced the volume index (diameter² × height) of white spruce by 50%. The competitiveness of bluejoint appeared to be independent of resource availabilities, but bluejoint had greater growth response to increased N availability than white spruce. Bluejoint competition depleted white spruce foliar δ13C and δ13N by 1.2 and 1.2‰ respectively, even under adequate water supply, indicating that N deficiency caused by bluejoint competition had a dominant effect (increasing 13C discrimination during photosynthesis) compared with the potential effect of drought stress on foliar δ13, and that strong NH4 uptake by bluejoint may have prevented significant soil N losses and 15N enrichment through nitrification and subsequent denitrification. [ABSTRACT FROM AUTHOR]

Abstract: Mechanical site preparation in forests often results in soil compaction, mixing of forest litter with mineral soil, and/or displacement of surface organic material in forest ecosystems. We used a 9-month laboratory incubation experiment to examine the effects of soil compaction and forest litter amendment on microbial biomass C (MBC) and N (MBN), soluble organic C and N, and C and net N mineralization rates in a boreal forest soil with a silt loam texture. Four treatments: forest litter unamended and noncompacted (OM0C0, bulk density at 1.1Mgm−3), forest litter unamended and compacted (OM0C1, 1.5Mgm−3), forest litter amended and noncompacted (OM1C0), and forest litter amended and compacted (OM1C1) were applied to the soil. Soil compaction reduced MBC, MBN, soluble organic C and N on several sampling dates. Carbon mineralization and net nitrification rates were reduced by soil compaction whether forest litter was amended or not. The total amount of C mineralized from OM0C0, OM0C1, OM1C0, and OM1C1 in 9-month was 1.8, 1.6, 2.6 and 1.7mgCg−1 soil, respectively. Forest litter amendment alone increased MBC in the early stage of the incubation and soluble organic C and N on every sampling date except the initial one. Forest litter amendment had a positive priming effect on C and net N mineralization and nitrification rates. The total amount of N mineralized from OM0C0, OM0C1, OM1C0, and OM1C1 was 40, 39, 61, and 59mgNkg−1 soil, respectively. We conclude that soil compaction and forest litter amendment influenced microbial properties and processes in this boreal forest soil under controlled conditions. Our results imply that forest management practices that alter soil porosity (through compaction) and organic matter distribution in the soil profile can dramatically change soil C and N dynamics that may result in the eventual change in soil C and N concentrations or availability. [Copyright &y& Elsevier]

The lowering of the water table resulting from peatland drainage may dramatically alter C and N cycling in peatland ecosystems, which contain one-third of the total terrestrial C. In this study, tree annual ring width and C (δ13C) and N (δ15N) isotope ratios in soil and plant tissues (tree foliage, growth rings, and understory foliage) in a black spruce-tamarack (Picea mariana-Larix laricina) mixed-wood forest were examined to study the effects of drainage on tree growth and C and N dynamics in a minerotrophic peatland in west-central Alberta, Canada. Drainage increased the δ15N of soil NH4+ from a range of +0.6‰ to +2.9‰ to a range of +4.6‰ to +7.0‰ most likely through increased nitrification following enhanced mineralization. Plant uptake of 15N-enriched NH4+ in the drained treatment resulted in higher plant δ15N (+0.8‰ to +1.8‰ in the drained plots and -3.9‰ to -5.4‰ in the undrained plots), and deposition of litterfall N enriched with 15N increased the δ15N of total soil N in the surface layer in the drained (+2.9‰) as compared with that in the undrained plots (+0.6‰). The effect of drainage on foliar δ13C was species-specific, i.e., only tamarack showed a considerably less negative foliar δ13C in the drained (-28.1‰) than in the undrained plots (-29.1‰), indicating improved water use efficiency (WUE) by drainage. Tree ring area increments were significantly increased following drainage, and δ13C and δ15N in tree growth rings of both species showed responses to drainage retrospectively. Tree-ring δ13C data suggested that drainage improved WUE of both species, with a greater and more prolonged response in tamarack than in black spruce. Our results indicate that drainage caused the studied minerotrophic peatland to become a more open ecosystem in terms of C and N cycling and loss. The effects of forested peatland drainage or drying on C and N balances deserve further research in order to better understand their roles in future global change. [ABSTRACT FROM AUTHOR]

Abstract: The effects of timber harvesting and the resultant soil disturbances (compaction and forest floor removal) on relative soil water content, microbial biomass C and N contents (Cmic and Nmic), microbial biomass C:N ratio (Cmic-to-Nmic), microbial respiration, metabolic quotient (qCO2), and available N content in the forest floor and the uppermost mineral soil (0–3cm) were assessed in a long-term soil productivity (LTSP) site and adjacent mature forest stands in northeastern British Columbia (Canada). A combination of principal component analysis and redundancy analysis was used to test the effects of stem-only harvest, whole tree harvest plus forest floor removal, and soil compaction on the studied variables. Those properties in the forest floor were not affected by timber harvesting or soil compaction. In the mineral soil, compaction increased soil total C and N contents, relative water content, and Nmic by 45%, 40%, 34% and 72%, respectively, and decreased Cmic-to-Nmic ratio by 29%. However, these parameters were not affected by stem only harvesting or whole tree harvesting plus forest floor removal, contrasting the reduction of white spruce and aspen growth following forest floor removal and soil compaction reported in an earlier study. Those results suggest that at the study site the short-term effects of timber harvesting, forest floor removal, and soil compaction are rather complex and that microbial populations might not be affected by the perturbations in the same way as trees, at least not in the short term. [Copyright &y& Elsevier]

Abstract: A better understanding of N availability in co-composted drilling wastes is required to evaluate the potential use of the composts as growth media. We investigated N dynamics in co-composted drilling wastes by examining the changes in the concentrations and partition of applied 15N in various soil N pools (, , dissolved organic N, microbial biomass N, and non-extractable N) in a 4-month greenhouse incubation experiment using 1-, 2-, 3-, and 4-year-old (referred to below as 1Y, 2Y, 3Y, and 4Y, respectively) composts, representing substrates with different quality. Regardless of compost age, after 4 months of incubation extractable N concentrations decreased (P<0.05), in contrast with the increasing pattern of the non-extractable N, indicating stabilization of the extractable N into the recalcitrant soil organic fraction. Fertilizer N application increased (P<0.05) extractable N concentrations. In the younger composts, a major part of the applied 15N was recovered in the non-extractable N fraction (44.0% for 1Y and 38.5% for 2Y) with little recovered as mineral N. On the other hand, a considerable percentage of the applied 15N (21.8% for 3Y and 18.8% for 4Y) was found in the pool in the older composts with relatively high mineral N but low organic C contents. This study shows that the dynamics of biologically available N and fate of applied N in the composts depend on compost quality such as mineral N and organic C contents, and compost C:N ratio. To use the co-composted drilling waste as growth media, different N management strategies need to be established for those composts with differed substrate quality. [Copyright &y& Elsevier]

Nitrogen (N) concentrations and stable N isotope abundances (δ15N) of common reed (Phragmites australis) planted in a constructed wetland were measured periodically between July 2001 and May 2002 to examine their seasonal variations in relation to N uptake and N translocation within common reed. Nitrogen concentrations in P. australis shoots were higher in the growing stage (7.5 to 24.8 g N kg-1)than in the senescence stage (4.2 to 6.8 g N kg-1), indicating N translocation from shoots to rhizomes. Meanwhile, the corresponding δ15N values were higher in the senescence stage (+12.2 to +22.4‰) than in the growing stage (+5.1 to +11.3‰). Coupled with the negative correlation (R² 0.24, P < 0.05, n 18) between N concentrations and δ15N values of shoots in the senescence stage, our results suggested that shoot N became enriched in δ15N due to N isotopic fractionation (with an isotopic fractionation factor, αs/p' of 1.012) during N translocation to rhizomes. However, the positive correlation between N concentrations and δ15N values in the growing stage (R² 0.19, P < 0.001, n 54) suggested that P. australis relies on N re-translocated from rhizome in the early growing stage and on mineral N in the sediment during the active growing stage. Therefore, seasonal δ15N variations provide N-isotopic evidence of N translocation within and N uptake from external N sources by common reed. [ABSTRACT FROM AUTHOR]

Many experiments conducted under controlled environmental conditions suggest that deciduous tree species are adapted to NO3– rather than NH4+ uptake. To test this under field conditions, we studied soil retention, tree uptake, and tree resorption of 15N derived from either 15NH4NO3 or NH415NO3 applied to trembling aspen (Populus tremuloides Michx.) and hybrid aspen (Populus tremula L. × P. tremuloides) at planting. Overall, the hybrid had greater dry-matter yield and took up more total N than the trembling aspen over two growing seasons after fertilization. The recovery of 15N per tree was also higher for the hybrid aspen than for the trembling aspen. Trembling aspen showed higher resorption efficiency of foliage N before abscission than hybrid aspen; however, the total amount of N retranslocated before leaf senescence was the reverse because of higher foliar dry-matter yield of hybrid aspen. The higher recovery of 15NH4+ than 15NO3– by trees seemed to be governed by higher N retention potential of NH4+ than NO3– in the soil. These results suggest that fertilization strategies need to be made based on both N acquisition capability of species and site-related factors, such as soil pH and immobilization–mineralization potential. [ABSTRACT FROM AUTHOR]

A greenhouse experiment was conducted to investigate the effects of P and S fertilization on the growth and nutrition of two aspens, a clonal aspen (Populus tremuloides Michx.) and a hybrid aspen (a mixture of Populus tremu loides × P. tremula L. and Populus tremula × P. tremuloides), grown in a Gray Luvisol fertilized with N. Phosphorus application significantly increased basal diameter (BD) increment and most other growth parameters for both clonal and hybrid aspens, whereas S application increased BD increment only for the hybrid aspen. Diameter increment, leaf area, and seedling biomass were generally increased by P application, regardless of S levels, but they responded to S application only if P was also applied. Phosphorus application significantly increased foliar P concentrations and foliar N and P contents and their uptake for the clonal aspen. For the hybrid aspen, P application increased foliar N, P, and S concentrations, contents, and uptake. Sulfur application significantly increased foliar S concentration, content, and uptake for the hybrid aspen but not foliar N concentration, content, and uptake for the clonal aspen. Except for height increment, growth parameters were significantly related to foliar percent P and N/P ratios and percent S and N/S ratios. It can be concluded that both P and S were deficient, but P was more limiting after potential N limitation was removed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Multi-cationic toxic elements compete for the exchange sites of biochar surfaces. • Negatively charged acidic functional groups on biochar surface act as electron donors. • Biochar promoted the transformation of As(V) to As(III), and Pb(II) to PbCO 3 /Pb(OH) 2. • Production of glomalin constrained the phytoavailability of Cd and Pb. • Pristine biochar is not recommended to soils with abundant multi-contaminants. The effect and mechanistic evidence of biochar on the (im)mobilization of potentially toxic elements (PTEs) in multi-contaminated soils, with respect to the role of surface-functional groups and organic/inorganic compounds of biochar, are poorly understood. Herein, biochars produced from grass residues, rice straw, and wood were applied to a mining-soil contaminated with As, Cd, Pb, and Zn for 473-d. Biochars did not reduce the mobilization of Cd and Zn, whereas they simultaneously exhibited disparate effects on As and Pb mobilization. The phenolic hydroxyl and carboxylic groups on the wood biochar's surfaces promoted the conversion of Pb2+ into PbCO 3 /Pb(OH) 2 and/or PbO, minimally by the rice and grass biochars. Rice and grass biochars led to the dissolution of scorodite and the formation of less stable forms of Fe-oxide-bound As (i.e., goethite and ferrihydrite); furthermore, it resulted in the reduction of As(V) to As(III). The PTEs mobilization and phytoavailability was mainly governed by the release of dissolved aliphatic- and aromatic-carbon, chloride, sulfur chemistry, phosphate competition, and the electrostatic repulsion in biochar-treated soils. In conclusion, pristine-biochar has a limited impact on the remediation of multi-contaminated soils, and the use of modified-biochar, possessing higher surface areas and functionality and active exchange sites, are preferred under such conditions. [ABSTRACT FROM AUTHOR]

Unprecedented increases in agricultural nitrous oxide (N 2 O) emissions in recent years have caused substantial environmental pollution that leads to ozone depletion and global warming. Application of biochar and/or nitrification inhibitors (NIs) has the potential to reduce N 2 O emissions; however, it is not clear how biochar application may affect the efficacy of NI in reducing nitrification rates, soil enzyme activities, and N 2 O emissions under different soil moisture regimes. We conducted a 60-day laboratory incubation experiment to study the effects of manure biochar and nitrapyrin (as a NI) on N 2 O emissions from a urea fertilized soil with either 60 (low) or 80% (high) water-filled pore space (WFPS). Nitrification rates were significantly affected by biochar × NI × WFPS and biochar × WFPS interactions. Biochar initially increased and then decreased the rates, resulting in 45.2 and 26.6% (P < 0.001 for both) overall reductions in low and high WFPS, respectively while NI reduced the rates only in the first 10 days at 60% WFPS. Biochar decreased (P < 0.001) and NI increased (P = 0.007) β-1,4-N-acetyl glucosaminidase activities while urease activities were increased (P < 0.001) by biochar across WFPS. Biochar had significant interaction with NI in cumulative N 2 O emissions with the efficacy of NI being reduced when co-applied with biochar. Cumulative N 2 O emissions were greater at high than at low WFPS; the emissions were decreased by biochar at 60% WFPS and NI at both 60 and 80% WFPS. We conclude that biochar reduces efficacy of nitrapyrin in mitigating N 2 O emissions and their effects on net nitrification rates, enzyme activities and N 2 O emissions are dependent on soil moisture level. • Biochar reduces the impact of nitrapyrin on N 2 O emission mitigation from the cropland soil. • Nitrapyrin has short-term but biochar has persistent effects on reducing nitrification rates. • Efficiency of nitrapyrin increases with soil moisture levels but decreases by biochar application. • Biochar decreased but nitrapyrin increased soil NAG activities. [ABSTRACT FROM AUTHOR]

Over-dose pesticide application disrupts plant physiological processes and soil biological functions; however, the toxicity mechanisms of pesticides and the effectiveness of mitigation measures are still unclear. Our review shows that over-dose of pesticide can cause plant phytotoxicity by enhancing reactive oxygen species and cellular membrane electrolyte leakage, which subsequently decrease chlorophyll biosynthesis, vegetative growth and yield. However, the optimum use of pesticides (insecticides at 0.21 kg a.i. ha-1; herbicides at 1.44 kg a.i. ha-1 and fungicides at =0.4 kg a.i. ha-1) may not interfere with plant physiological functions, while indirectly improving plant nutrients absorption, translocation and yield. In the soil system, pesticide application decreases microbial population by disrupting the microbial metabolism and cellular protein denaturation. Moreover, pesticide application can restrict (by adsorption, etc.) glucose release from organic matter by decreasing the hydrolysis of extracellular enzymes, thereby reducing the labile C source for microbes and resulting in lower soil organic carbon cycling. The pesticide residue can decrease biological nitrogen fixation and nitrogen mineralization by decreasing diazotrophs and saprophytic bacterial population due to cellular hyperkinesis and misfunctions, respectively. Organo-phosphate pesticides can induce oxidative stress to microbes which can affect phosphorus (P) mineralization, but may also enhance P-solubilizing bacterial activities and P availability. The use of biosurfactants, exogenously induced microbes, and soil amendments (e.g., biochar) can effectively remediate pesticide toxicity through solubilization, microbial catabolism and sorption of pesticides by 70%, 78% and 69%, respectively. However, field application of biosurfactants and optimization of biochar characteristics remain challenging for effective pesticide sorption and remediation. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "Biochar affects compressive strength of Portland cement composites: a meta-analysis." The correction states that the positions of certain figures in the original article were incorrectly reversed. The corrected figures show the effect sizes of biochar addition on the compressive strength of Portland cement composites at different time intervals, as influenced by various factors. The original article has been updated to reflect these corrections. [Extracted from the article]

One strategy to reduce CO2 emissions from cement production is to reduce the amount of Portland cement produced by replacing it with supplementary cementitious materials (SCMs). Biochar is a potential SCM that is an eco-friendly and stable porous pyrolytic material. However, the effects of biochar addition on the performances of Portland cement composites are not fully understood. This meta-analysis investigated the impact of biochar addition on the 7- and 28-day compressive strength of Portland cement composites based on 606 paired observations. Biochar feedstock type, pyrolysis conditions, pre-treatments and modifications, biochar dosage, and curing type all influenced the compressive strength of Portland cement composites. Biochars obtained from plant-based feedstocks (except rice and hardwood) improved the 28-day compressive strength of Portland cement composites by 3–13%. Biochars produced at pyrolysis temperatures higher than 450 °C, with a heating rate of around 10 C min-1, increased the 28-day compressive strength more effectively. Furthermore, the addition of biochar with small particle sizes increased the compressive strength of Portland cement composites by 2–7% compared to those without biochar addition. Biochar dosage of < 2.5% of the binder weight enhanced both compressive strengths, and common curing methods maintained the effect of biochar addition. However, when mixing the cement, adding fine and coarse aggregates such as sand and gravel affects the concrete and mortar's compressive strength, diminishing the effect of biochar addition and making the biochar effect nonsignificant. We concluded that appropriate biochar addition could maintain or enhance the mechanical performance of Portland cement composites, and future research should explore the mechanisms of biochar effects on the performance of cement composites. Highlights: Biochar effects on Portland cement composites were studied through a meta-analysis. Effects of biochar production condition, modification and pre-treatment were studied. The above parameters affected the compressive strength of Portland cement composites. Biochar addition effects were dependent on batch designs of Portland cement composites. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are emerging contaminants that adversely affect environmental health. In this review, we discuss the uptake of MPs by plants via endocytosis and crack-entry pathways in the roots and stomata of leaves; the translocation of MPs via xylem and phloem; and the toxicity of MPs to diverse plant species through oxidative stress, inhibition of photosynthesis, cytotoxicity, and genotoxicity. It's difficult to assess the health risks of MPs because they directly cause toxicity and also change soil properties and the bioavailability of coexisting pollutants, such as plastic additives, in the plant rhizosphere, and bioaccumulate along the food chain. Moreover, compared to the uptake behavior and phytotoxicity effects of MPs in laboratory and hydroponic studies, MPs of various shapes, sizes, and types are likely to cause different effects on plants in complex natural environments. This review proposes potential phytoremediation strategies, including phytoextraction, immobilization, and rhizoremediation, for MP pollutants and provides guidelines for the bioremediation of MP-contaminated environments to enhance environmental sustainability. In the phytoremediation of MP pollution, the selection and disposal of plants used for phytoremediation and the optimization of functional microbes in the rhizosphere remain challenging. Future studies should address knowledge gaps in (i) methods for determining environmentally-relevant concentrations of MPs, (ii) the assessment of the ecological and human health risks of MPs in the natural environment, and (iii) the development of effective strategies for the phytoremediation of MP pollution. [ABSTRACT FROM AUTHOR]

One strategy to reduce CO2 emissions from cement production is to reduce the amount of Portland cement produced by replacing it with supplementary cementitious materials (SCMs). Biochar is a potential SCM that is an eco-friendly and stable porous pyrolytic material. However, the effects of biochar addition on the performances of Portland cement composites are not fully understood. This meta-analysis investigated the impact of biochar addition on the 7- and 28-day compressive strength of Portland cement composites based on 606 paired observations. Biochar feedstock type, pyrolysis conditions, pre-treatments and modifications, biochar dosage, and curing type all influenced the compressive strength of Portland cement composites. Biochars obtained from plant-based feedstocks (except rice and hardwood) improved the 28-day compressive strength of Portland cement composites by 3–13%. Biochars produced at pyrolysis temperatures higher than 450 °C, with a heating rate of around 10 C min-1, increased the 28-day compressive strength more effectively. Furthermore, the addition of biochar with small particle sizes increased the compressive strength of Portland cement composites by 2–7% compared to those without biochar addition. Biochar dosage of < 2.5% of the binder weight enhanced both compressive strengths, and common curing methods maintained the effect of biochar addition. However, when mixing the cement, adding fine and coarse aggregates such as sand and gravel affects the concrete and mortar's compressive strength, diminishing the effect of biochar addition and making the biochar effect nonsignificant. We concluded that appropriate biochar addition could maintain or enhance the mechanical performance of Portland cement composites, and future research should explore the mechanisms of biochar effects on the performance of cement composites. Highlights: Biochar effects on Portland cement composites were studied through a meta-analysis. Effects of biochar production condition, modification and pre-treatment were studied. The above parameters affected the compressive strength of Portland cement composites. Biochar addition effects were dependent on batch designs of Portland cement composites. [ABSTRACT FROM AUTHOR]

Highly diverse exoenzymes mediate the energy flow from substrates to the multitrophic microbiota within the soil decomposer micro‐food web. Here, we used a "soil enzyme profile analysis" approach to establish a series of enzyme profile indices; those indices were hypothesized to reflect micro‐food web features. We systematically evaluated the shifts in enzyme profile indices in relation to the micro‐food web features in the restoration of an abandoned cropland to a natural area. We found that enzymatic C:N stoichiometry and decomposability index were significantly associated with substrate availability. Furthermore, the higher Shannon diversity index in the exoenzyme profile, especially for the C‐degrading hydrolase, corresponded to a greater microbiota community diversity. The increased complexity and stability of the exoenzyme network reflected similar changes with the micro‐food web networks. In addition, the gross activity of the enzyme profile as a parameter for soil multifunctionality, effectively predicted the substrate content, microbiota community size, diversity, and network complexity. Ultimately, the proposed enzymic channel index was closely associated with the traditional decomposition channel indices derived from microorganisms and nematodes. Our results showed that soil enzyme profile analysis reflected very well the decomposer food web features. Our study has important implications for projecting future climate change or anthropogenic disturbance impacts on soil decomposer micro‐food web features by using soil enzyme profile analysis. Highlights: Soil enzyme profile analysis for indicating decomposer micro‐food web features was first proposed.Diversity indication utilities for contrasting enzyme profiles were different.Protozoa channel index and enzymatic channel index were proposed. [ABSTRACT FROM AUTHOR]

How cattle urine and dung addition, and their interaction with the mineral soil regulate cumulative autotrophic and heterotrophic nitrifications and greenhouse gas (GHG) emission is poorly understood. We investigated the effect of urine (applied at 425 mg N kg−1 soil) and dung (applied at 200 mg total N kg−1 soil) addition on cumulative autotrophic and heterotrophic nitrifications, and GHG emission in a grassland soil in a 35-day laboratory incubation experiment under six treatments: CK, unamended control; U, urine addition; Ds, dung added on the soil surface; U-Ds, urine addition + dung added on the soil surface; Dm, dung mixed into the soil; and U-Dm, urine addition + dung mixed into the soil. Compared with the CK, the U, U-Ds, and U-Dm treatments increased cumulative net nitrification (autotrophic + heterotrophic) by 548, 587, and 505% and cumulative autotrophic nitrification by 593, 618, and 508%, but the Dm treatment decreased cumulative net and autotrophic nitrifications by 77 and 83%, respectively. However, cumulative heterotrophic nitrification was less than 1% of the cumulative autotrophic nitrification in the CK and it was decreased by Ds and Dm as compared with the CK at the end of the incubation. Cumulative emissions of carbon dioxide (CO2) and nitrous oxide (N2O) were in the order of CK < U < Ds < Dm < U-Ds < U-Dm. In addition, all urine and dung treatments reduced cumulative methane (CH4) uptake (negative values of CH4 emission) as compared with the CK. Overall, soil cumulative net and autotrophic nitrifications were higher, but GHG emission was lower, with dung added on the soil surface than with it mixed into the soil. We conclude that urine addition increases but dung addition decreases cumulative autotrophic nitrification; dung addition also decreases heterotrophic nitrification, and how dung is added to the soil is important in regulating the nitrification processes and GHG emission. Therefore, urine and dung management can alter soil N transformations and has implications for mitigating climate change. [ABSTRACT FROM AUTHOR]

Microplastic (MP) pollution in agricultural soils, resulting from the use of plastic mulch, compost, and sewage sludge, jeopardizes the soil microbial populations. However, the effects of MPs on soil chemical properties and microbial communities remain largely unknown. Here, we investigated the effects of different concentration levels (0, 0.1, 1, 3, 5, and 7%; w:w) of low-density polyethylene (LDPE) MPs on the chemical properties and bacterial communities of agricultural soil in an incubation study. The addition of LDPE MPs did not drastically change soil pH (ranging from 8.22 to 8.42). Electrical conductivity increased significantly when the LDPE MP concentrations were between 1 and 7%, whereas the total exchangeable cations (Na+, K+, Mg2+, and Ca2+) decreased significantly at higher LDPE MP concentrations (3–7%). The highest available phosphorus content (2.13 mg kg−1) was observed in 0.1% LDPE MP. Bacterial richness (Chao1 and Ace indices) was the lowest at 0.1% LDPE MP, and diversity indices (Shannon and Invsimpson) were higher at 0 and 1% LDPE MP than at other concentrations. The effect of LDPE MP concentrations on bacterial phyla remained unchanged, but the bacterial abundance varied. The relative abundance of Proteobacteria (25.8–33.0%) was the highest in all treatments. The abundance of Acidobacteria (15.8–17.2%) was also high, particularly in the 0, 0.1, and 1% LDPE MPs. With the increase in LDPE MP concentration, the abundance of Actinobacteria gradually increased from 7.80 to 31.8%. Our findings suggest that different MP concentration levels considerably alter soil chemical properties and microbial composition, which may potentially change the ecological functions of soil ecosystems. [ABSTRACT FROM AUTHOR]

Biochar has been widely recommended as an effective soil amendment for reducing nitrous oxide (N2O) emissions and nitrogen (N) leaching. However, the effects of biochar application to Lei bamboo plantations on soil N2O emissions and N leaching remain unclear. These effects on soil N2O emissions and N leaching were investigated in the present study using five treatments applied with the same amount of N: rice husk at 10 t ha−1 (10H) and 30 t ha−1 (30H), biochar at 10 t ha−1 (10B) and 30 t ha−1 (30B), and no additions (control, CK). Both the 10H and 30H treatments significantly increased cumulative N2O emissions compared to the CK treatment, with an increment of 0.78 and 2.20 kg N ha−1, respectively. The 30B treatment significantly reduced cumulative N2O emissions by 0.90 kg N ha−1, whereas the 10B treatment had no significant effect. The reduction in N2O emissions following the high-rate biochar addition was probably due to the increased pH and the total abundance of nosZ I and nosZ II genes. The 30H treatment significantly increased nitrate N (NO3−–N) and dissolved organic N (DON) leaching by 38% and 170% respectively compared to the CK treatment, and had the largest N loss via N2O emissions and N leaching, while the 30B treatment had the lowest N loss. Partial least squares path modeling revealed that soil chemical properties [ammonium nitrogen (NH4+–N), NO3−–N, DON, dissolved organic C (DOC), total N (TN), soil organic C (SOC), and pH] dominantly affected soil N2O emissions, while the total abundance of denitrifying genes (nirS, nirK, nosZ I, and nosZ II) were the key factors involved in reducing NO3−–N leaching. There was a strong positive correlation between cumulative N2O emissions and N leaching loss, which may be related to excessive N surplus in the soil. Our results suggest that the replacement of rice husk by its biochar at a high-rate would reduce the risk of N2O emissions and N leaching loss effectively from Lei bamboo forests in subtropical China. [ABSTRACT FROM AUTHOR]