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In a recent paper, Jach-Smith and Jackson (2020) used the SP 15 sp N natural abundance ( SP 15 sp N) of two sources of nitrogen (N), available soil N and N in AMF, and SP 15 sp N mass balance equations to calculate the amount of N transferred by arbuscular mycorrhizal fungi (AMF) to switchgrass ( I Panicum virgatum i L.), a perennial grass (the host plant) used in a bioenergy system in the United States. Natural abundance of 15 N in nitrogen-limited forest and tundra can estimate nitrogen cycling through mycorrhizal fungi: a review. In this context, it is critical to measure the SP 15 sp N of available N under different N addition treatments to properly use the isotope mass balance equations (Hobbie and Hobbie 2008). [Extracted from the article]

The effect of long-term nitrogen (N) and sulfur (S) deposition on litter mass loss and changes in carbon (C), N, and S composition and enzyme activities during litter decomposition was investigated in a boreal forest. This study included four N × S treatments: control (CK), N application (30 kg N ha−1 yr−1), S application (30 kg S ha−1 yr−1), and N plus S application (both at 30 kg ha−1 yr−1). Two experiments were conducted for 22 months: 1) a common litter decomposition experiment with litter bags containing a common litter (same litter chemistry) and 2) an in-situ litter decomposition experiment with litter from each treatment plot (and thus having different litter chemistry). Litterbags were placed onto the four treatment plots to investigate the direct effect of N and S addition and the combined effect of N and/or S addition and litter chemistry on litter decomposition, respectively. Regardless of the source of litter, N and/or S addition affected C, N and S composition at a certain period of the experiment but did not affect litter mass loss and enzyme activity throughout the experiment, indicating that the N and S addition rates were below the critical level required to affect C and N cycling in the studied ecosystem. However, the greater change in N composition per unit of litter mass loss in the N addition treatment than in the other treatments in the common litter but not in the in-situ litter experiment, suggests that the effect of N addition on N loss and retention depends on the initial litter chemistry. We conclude that the studied N and S addition rates did not affect litter decomposition and elemental cycling in the studied forest ecosystem even though the N and S addition rates were much greater than their ambient deposition rates. Image 1 • 10-yr N and S addition did not affect litter decomposition. • N and S addition changed litter chemistry including lignin content. • Changed litter chemistry by N and S did not affect litter decomposition. • The studied boreal forest was resistant to low levels of N and S addition. [ABSTRACT FROM AUTHOR]

Abstract Ammonia (NH 3) emission from agricultural sources has contributed significantly to air pollution, soil acidification, water eutrophication, biodiversity loss, and declining human health. Although there are numerous strategies for reducing NH 3 emission from agricultural systems, the effectiveness of these measures is highly variable. Furthermore, the integrated assessment of measures to reduce NH 3 emission both from livestock production and cropping systems based on animal and crop type is lacking. Therefore, we conducted a global meta-analysis and integrated assessment of measures to reduce NH 3 emission from agricultural systems. Most of the studied mitigation strategies were effective in reducing NH 3 emission. In the livestock production system, dietary additive, urease inhibitor (UI), manure acidification and deep manure placement have the highest mitigation potential relative to other mitigation strategies, with reduction ranges of 35.1–54.2%, 24.3–68.7%, 88.8–95.0%, and 93.8–99.7%, respectively, relative to the control, while manure storage management could significantly reduce NH 3 emission by 70.0–82.1%. In the cropping system, fertilizer source, use of enhanced efficiency fertilizers, and method of field application are most effective for reducingNH 3 emission. The use of ammonium nitrate, controlled release fertilizer (CRF), and deep placement of fertilizers could reduce NH 3 emission by 88.3, 56.8, and 48.0%, respectively. Choosing a proper fertilizer is critical for decreasing NH 3 emission from cropping systems. We conclude that carefully planned and adopted strategies suited for local conditions are promising for minimizing NH 3 emission from agricultural systems on a global scale, while possible effects of those mitigation measures on the emission of greenhouse gases should be studied in the future. Graphical abstract Image 1 Highlights • We assessed strategies for mitigating agricultural NH 3 emission by animal and crop type. • Most mitigation strategies significantly reduced NH 3 emission. • Changing fertilizer type from urea to ammonium nitrate was the most effective measure to reduce NH 3 emission from cropland. • Manure acidification is most effective to reduce emission from livestock systems. Ammonia emission from agricultural sources could be markedly reduced by mitigation measures based on this meta-analysis. [ABSTRACT FROM AUTHOR]

Abstract Managing municipal green waste is a challenge to municipalities, partly because of the slow rate of decomposition of green waste during composting due to its high lignin and cellulose contents. Hence, this study evaluated the effect of alkyl polyglycoside (APG), a biosurfactant, and the earthworm Eisenia fetida on the composting process. Addition of APG and E. fetida significantly increased total bacteria, cellulolytic fungi, phosphate solubilizing bacteria and nitrogen fixing bacteria populations, and the activities of cellulase, urease and alkaline phosphatase in composts as compared with the control. The APG and earthworm treatments also increased surface roughness and porosity of the green waste; Compared with control, APG and earthworm addition increased the degradation rate of TOC, lignin and cellulose by 5.9–17.9, 10.3–32.0 and 10.8–18.8%, respectively, and resulted in better compost quality, as was reflected in the neutral pH, higher cation exchange capacity (CEC) and nutrient concentrations (N, P, K, Ca, Mg, Fe, Cu, Zn, Mn). Final germination percentage and growth rate of tomato, eggplant and pepper seedlings were higher (P < 0.05) or similar in all composts produced with the addition of APG and earthworm, while plant growth was lower (P < 0.05) in the compost produced with the control than in peat substrate. The combination of APG+ E. fetida enhanced the decomposition of green waste and improved final compost quality the most. Further research is needed to determine the best level of APG addition and optimum earthworm density for composting green waste. Highlights • Alkyl polyglycoside (APG) and/or E. fetida addition enhanced lignin degradation. • APG and/or E. fetida addition increased disaggregation of green waste. • APG and/or fetida addition improved nutrient availability in compost. • The compost supports the growth of tomato, eggplant and pepper seedlings. [ABSTRACT FROM AUTHOR]

Abstract Nitrogen (N) deposition has rapidly increased and is influencing forest ecosystem processes and functions on a global scale. Understanding process-specific N transformations, i.e., gross N transformations, in forest soils in response to N deposition is of great significance to gain mechanistic insights on the linkages between global N deposition and N availability or loss in forest soils. In this paper, we review factors controlling N mineralization, nitrification and N immobilization, particularly in relation to N deposition, discuss the limitations of net N transformation studies, and synthesize the literature on the effect of N deposition on gross N transformations in forest ecosystems. We found that more than 97% of published papers evaluating the effect of N deposition (including N addition experiments that simulate N deposition) on soil N cycle determined net rates of mineralization and nitrification, showing that N deposition significantly increased those rates by 24.9 and 153.9%, respectively. However, studies on net N transformation do not provide a mechanistic understanding of the effect of N deposition on N cycling. To date, a small number of studies (<20 published papers) have directly quantified the effect of N deposition on gross N transformation rates, limiting our understanding of the response of soil N cycling to N deposition. The responses to N deposition of specific N transformation processes such as autotrophic nitrification, heterotrophic nitrification, dissimilatory nitrate reduction to ammonium, N mineralization, and N immobilization are poorly studied. Future research needs to use more holistic approaches to study the impact of N deposition on gross N transformation rates, N loss and retention, and their microbial-driven mechanisms to provide a better understanding of the processes involved in N transformations, and to understand the differential responses between forest and other ecosystems. Graphical abstract ↑represents an increase in response to N deposition; ↓ represents a decrease in response to N deposition. ? Represents the response is not clear. Image 1 Highlights • N deposition slightly decreases microbial biomass carbon and the fungi to bacteria ratio. • N deposition strongly increases ammonia-oxidizing bacteria and archaea. • N deposition increase or decrease the synthesis of different soil enzymes. • N deposition can increase, decrease or have no effect on gross N mineralization and nitrification rate. • N deposition mostly reduces or has no effect on gross N immobilization rates. Research on simultaneously operating gross N transformations will improve our understanding of the effect of N deposition on N cycling in forest ecosystems and gross N transformation measurements should be fostered in future studies. [ABSTRACT FROM AUTHOR]

In the background of climate warming, the demand for improving soil quality and carbon (C) sequestration is increasing. The application of biochar to soil has been considered as a method for mitigating climate change and enhancing soil fertility. However, it is uncertain whether the effects of biochar application on C-mineralization and N transformation are influenced by the presence or absence of plant growth-promoting bacteria (PGPB) and soil nitrogen (N) level. An incubation study was conducted to investigate whether the effects of biochar application (0 %, 1 %, 2 % and 4 % of soil mass) on soil respiration, N status, and microbial attributes were altered by the presence or absence of PGPB (i.e., Sphingobium yanoikuyae BJ1) under two soil N levels (N0 and N1 soils as created by the addition of 0 and 0.2 g kg−1 urea- N, respectively). The results showed that biochar, BJ1 strain and their interactive effects on cumulative CO 2 emissions were not significant in N0 soils, while the effects of biochar on the cumulative CO 2 emissions were dependent on the presence or absence of BJ1 in N1 soils. In N1 soils, applying biochar at 2 % and 4 % increased the cumulative CO 2 emissions by 141.0 % and 166.9 %, respectively, when BJ1 was absent. However, applying biochar did not affect CO 2 emissions when BJ1 was present. In addition, the presence of BJ1 generally increased ammonium contents in N0 soils, but decreased nitrate contents in N1 soils relative to the absence of BJ1, which indicates that the combination of biochar and BJ1 is beneficial to play the N fixation function of BJ1 in N0 soils. Our results highlight that biochar addition influences not only soil C mineralization but also soil available N, and the direction and magnitude of these effects are highly dependent on the presence of PGPB and the soil N level. [Display omitted] • High biochar application rates promoted CO 2 emissions when BJ1 was absent in N1 soils. • Applying biochar did not affect CO 2 emissions when BJ1 was present in N1 soils. • The presence of BJ1 increased NH 4 + in the N0 soils relative to the absence of BJ1. • The presence of BJ1 decreased NO 3 - in N1 soils relative to the absence of BJ1. [ABSTRACT FROM AUTHOR]

Vermicomposting is a promising method for reusing urban green waste. However, high lignin content in the green waste could hinder the development of earthworm and microorganisms and the vermicomposting process, resulting in a low-quality vermicompost product. The objective of this study was to evaluate the effect of bamboo biochar addition (at 0%, 3%, and 6% on a dry w/w basis) on the activity of Eisenia fetida and the obtained vermicompost. Biochar addition increased ( P  < 0.05) earthworm biomass, juvenile and cocoon numbers of Eisenia fetida , as well as the activities of dehydrogenase, cellulase, urease and alkaline phosphatase. Compared to the control, lignin degradation rate was enhanced up to 13.89% by biochar addition. Biochar addition also improved the vermicompost quality in terms of cation exchange capacity (CEC), dissolved organic carbon (DOC) degradation, humification, nitrogen transformation, toxicity to germinating seeds ( Brassica rapa L., Chinensis group) and heavy metals concentrations. The 6% bamboo biochar addition rate achieved maturity after 60 days of vermicomposting and resulted in the highest quality vermicompost based on parameters such as CEC, DOC, NH 4 + -N/NO 3 - -N ratio, germination index and heavy metal concentration. We conclude that 6% biochar addition promoted earthworm growth and the vermicomposting of green waste. [ABSTRACT FROM AUTHOR]

Our understanding of the effect of agroforestry systems on soil organic carbon (SOC) is largely limited to the upper layer of the mineral soil, while LFH (litter, partially decomposed litter and humus) and deeper soil layers are poorly studied. In this study, the effects of three different agroforestry systems (hedgerow, shelterbelt, and silvopasture) and their component land-cover types (treed area and adjacent herbland) on SOC stock in LFH and mineral soil layers (0–75 cm) were investigated across 36 sites in central Alberta, Canada. The SOC stock of mineral soil (0–75 cm) was not affected by agroforestry systems but by land-cover type. The treed area had greater ( p  < 0.001) SOC in the 0–75 cm mineral soil (25.5 kg C m −2 ) than the herbland (19.4 kg C m −2 ), driven by the greater ( p  < 0.001) SOC level in the top 0–30 cm rather than that in the deeper layers (30–75 cm). Within the treed area, the silvopasture system that was dominated by broad-leaf deciduous trees had 56–70% more SOC in the 0–10 cm soil than in the hedgerow and shelterbelt systems. The SOC stock in the 0–10 cm layer was positively ( p  = 0.025) related to the C stock of the overlying LFH layer in the silvopasture system. These results together with the 22–24% higher dissolved organic carbon (DOC) concentration in the silvopasture than in the other systems suggest that the greater SOC stock in the 0–10 cm mineral soil could be attributed to the higher rates of translocation of DOC from the LFH in the silvopasture than that in shelterbelt or hedgerow. We conclude that SOC stock in the top mineral soil (e.g., 0–30 cm) is more responsive to changes in land-cover type and the LFH layer plays an important role in increasing SOC stock in the surface mineral soil of the agroforestry systems in central Alberta. [ABSTRACT FROM AUTHOR]

Litter decomposition rates are affected by abiotic and biotic factors such as climate, soil physico-chemical properties, litter chemistry, nitrogen (N) availability, and activities of soil organisms. Elevated N and sulfur (S) deposition originated from oil sands mining and upgrading activities can change soil microbial properties, litter chemistry, and litter decomposition rates in the surrounding forest ecosystems in northern Alberta. We studied (1) the effect of long-term N and S deposition on litter chemistry and soil microbial properties, and (2) the effect of changed litter chemistry and soil microbial properties on litter decomposition (CO 2 emission) in a 100-day laboratory incubation experiment using trembling aspen ( Populus tremuloides ) leaf litter and forest floor collected from a mixedwood boreal forest that has been subject to simulated N and S deposition for 10 years. Litter chemistry (lignin, total carbon (C) and N, and calcium (Ca), aluminum (Al), manganese (Mn), and magnesium (Mg) concentration) and forest floor microbial properties (microbial biomass C and N, and extracellular enzyme activities) were analyzed. Ten years of N and S addition increased N ( P  < .05 unless otherwise stated) and decreased lignin concentrations resulting in lower C/N and lignin/N ratios in the litter. In addition, N and S addition increased forest floor microbial biomass ( P  < .01) and enzyme activities. Cumulative CO 2 emission (C cum ) from litter was greater from the N and/or S addition treatments than that from the control, probably due to decreased C/N and lignin/N ratios in litter from the N and S addition treatments; meanwhile, C cum from litter was not affected by soil microbial activity. The results indicate that N and S deposition enhances decomposition of aspen leaf litter by decreasing C/N and lignin/N ratios, suggesting that long-term exposure to high levels of N and S deposition can significantly change C (and associated nutrients) cycling in forest ecosystems in the oil sands region. [ABSTRACT FROM AUTHOR]

Oil sands mining activities in northern Alberta, Canada emit large amounts of nitrogen (N) and sulfur (S) oxides to the atmosphere, increasing N and S deposition. We studied the long-term (2006–2016) effect of elevated concentrations of simulated N and S deposition on soil properties and understory species composition in a mixedwood boreal forest in a two (0 and 30 kg N ha −1 year −1 , as ammonium nitrate) × two (0 and 30 kg S ha −1 year −1 , as sodium sulfate) factorial experiment. Soil (forest floor and 0–15 cm mineral soil) and understory vegetation samples were collected and the cover of understory vegetation was determined in August 2016. Eleven years of N deposition increased (p = .045) total N concentration and decreased (p < .10 unless otherwise indicated) carbon to N ratio by 11 and 7%, respectively, in the forest floor. Sulfur deposition decreased (p = .045) exchangeable calcium concentration by 36% in the mineral soil. Species evenness (by 7%) and the overall diversity (by 7%) were decreased and community composition was changed (p = .008) in the herb stratum by N but not by S deposition, due to species-specific responses to N deposition. However, elevated concentrations of N and S deposition did not change species diversity and composition in the shrub stratum. Decreased foliar phosphorus and potassium concentrations and increased N to phosphorus ratio in some species indicate a potential risk of nutrient imbalance by N deposition. Reducing N emission to minimize its negative effect on boreal forest ecosystems should be a priority in emissions management in the oil sands. [ABSTRACT FROM AUTHOR]

The effectiveness of nitrogen (N) fertilization in improving tree growth in saline forest soils is poorly understood. Hence, in this study, the interactive effect of N fertilization and salt stress on seedling physiology and growth was examined to improve our understanding of possible mechanisms for fertilization to mitigate salt stress. We compared physiological characteristics, growth, and foliar and root nutrient concentrations in lodgepole pine ( Pinus contorta ) and white spruce ( Picea glauca ) seedlings planted in a peat-mineral soil mix during a three months study with N fertilization (0 and 300 mg N seedling −1 ) and salinity (0, 50, 100, 150 mmol L −1 NaCl) in a greenhouse experiment. Nitrogen fertilization significantly increased net photosynthetic rates ( P n ) and N concentrations in needles and roots, resulting in improved seedling height and root collar diameter growth and total seedling biomass for both species when seedlings were subjected to low salinity (50 mmol L −1 NaCl), while it did not help tree growth under high salinity (150 mmol L −1 NaCl). The physiological responses to combined salt stress and N fertilization did not differ between the two species; however, fertilization improved the growth of pine seedlings more than that of spruce seedlings under different salinity levels. The results suggest that the effectiveness of N fertilization in mitigating the salinity effect on seedling growth was species specific. Our study demonstrates that N fertilization improves tree growth through enhanced photosynthesis and N nutrition under low salinity and provides valuable insights into strategies to manage N nutrition in saline boreal forest soils. [ABSTRACT FROM AUTHOR]

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Metabolomic and gut microbial responses of soil fauna to environmentally relevant concentrations of microplastics indicate the potential molecular toxicity of microplastics; however, limited data exist on these responses. In this study, earthworms (Eisenia fetida) were exposed to spherical (25–30 μm diameter) polystyrene microplastic-contaminated soil (0.02%, w:w) for 14 days. Changes in weight, survival rate, intestinal microbiota and metabolic responses of the earthworms were assessed. The results showed that polystyrene microplastics did not influence the weight, survival rate, or biodiversity of the gut microbiota, but significantly decreased the relative abundance of Bacteroidetes at the phylum level. Moreover, polystyrene microplastics disturbed the osmoregulatory metabolism of earthworms, as indicated by the significantly decreased betaine, myo-inositol and lactate, and increased 2-hexyl-5-ethyl-furan-3-sulfonic acid at the metabolic level. This study provides important insights into the molecular toxicity of environmentally relevant concentrations of polystyrene microplastics on soil fauna. [Display omitted] • Molecular toxicity of spherical polystyrene microplastics (PS MPs, 25–30 μm) was assessed. • PS MPs (0.02%, w/w) disturbed the osmoregulatory metabolism of earthworms. • PS MPs did not affect intestinal microbial biodiversity of earthworms. • PS MPs significantly decreased the abundance of Bacteroidetes of earthworms. [ABSTRACT FROM AUTHOR]

[Display omitted] • Broadleaf species identity significantly affected microbial community composition in mixed litter. • Higher bacterial diversity was observed in decomposing mixed litter. • The fungal diversity was no different between single- and mixed-species litter. • Saprotrophic fungi increased in mixed litter and accelerated decomposition. • pH, lignin, air temperature, and soil moisture significantly influenced decomposers. Converting coniferous plantations to mixed plantations influences the microbial community composition and potential functions during litter decomposition. However, it is unclear how litter decomposition and associated microbial communities are interactively affected by litter mixing and environmental factors. Here, an in situ litter decomposition experiment was conducted to investigate the dynamics of microbial diversity in mixed litter (at a mass ratio of 1:1) from coniferous (Pinus massoniana) and broadleaf tree, including Bretschneidera sinensis, Manglietia chingii, Cercidiphyllum japonicum, Michelia maudiae, and Camellia oleifera. We found that the mass loss from mixed litter was higher than that of monospecific litter. The chemical characteristics of the broadleaf tree species included in the mixed litter significantly affected the microbial community composition and diversity, and those effects increased over time. Compared to the monospecific litter, the mixed litter had a higher relative abundance of saprotrophs and microbial functional groups related to carbon and nitrogen cycling. Moreover, litter chemistry (i.e., pH, lignin and cellulose content) and environmental factors (i.e., air temperature and soil moisture content) were the most crucial factors affecting the microbial decomposer community. Our results suggest that introducing broadleaf tree species with high litter quality to coniferous plantations changes the composition and function of microbial communities related to litter decomposition, which is conducive to accelerating litter decomposition in subtropical plantations. [ABSTRACT FROM AUTHOR]

Emerging microplastic pollution and biochar application result in their coexistence in the soil. In this study, a polyethylene microplastic, a straw biochar, and a manure biochar were applied alone or in combination to an agricultural soil to explore their interactive effects on microbial biomass carbon and nitrogen, bacterial community composition, structure and function, and the resultant greenhouse gas emissions in a 45-day laboratory incubation. At the end of incubation, the co-application of microplastic and biochar suppressed the global warming potential of cumulative greenhouse gas emissions compared with the sum of their application alone. Specifically, coexisting with microplastics increased N 2 O emissions by 37.5% but decreased CH 4 emissions by 35.8% in the straw biochar added soil, and decreased N 2 O, CO 2 and CH 4 emissions by 24.8, 6.2, and 65.2%, respectively, in the manure biochar added soil. A correlation network analysis illustrated that the increased global warming potential was related to the changed bacterial function and microbial biomass carbon and nitrogen in the treatments with straw biochar and/or polyethylene microplastic added, and by the changed bacterial community structure and function in the treatments with manure biochar and/or polyethylene microplastic added. Bacterial functions associated with tricarboxylic acid cycle contributed to CO 2 emissions. Bacterial functions associated with the nitrogen cycle such as nosZ and AOBamoABC were negatively and positively correlated with N 2 O emissions, respectively. The interaction between different types of microplastics and soil amendments and the resultant effects on ecosystem function deserve further research. [ABSTRACT FROM AUTHOR]

Afforestation on croplands has been proposed as a means to mitigate the increasing emission of anthropogenic CO 2 . However, the relative contribution of above- and belowground litter input on soil organic carbon (SOC) sequestration following afforestation is not fully understood. We used a 270-day laboratory incubation experiment to examine the impact of litter type (i.e., leaf vs. fine root litter) of a poplar tree ( Populus simonii Carr., C 3 plant) on soil respiration and the turnover of new vs. old soil C in surface (0–10 cm) and subsurface mineral soils (40–50 cm) collected from a marginal cropland planted to maize ( Zea mays L., C 4 plant) in a semi-arid region in northeast China. Our results showed that fine root rather than leaf litter addition helps to sequester SOC even though soil microbial respiration rates were stimulated by both leaf and fine root litter input. Neither leaf nor fine root litter addition stimulated mineralization of old soil C across the two soil layers, but more new C was incorporated into the soil with fine root addition as compared with leaf litter addition. Moreover, the subsurface soil had greater potential to sequester SOC as compared to the surface soil. Our results suggest that root rather than leaf litter input drives soil carbon sequestration on the marginal soil, especially in the subsurface soil, and planting deep-rooted trees with large belowground biomass production could be used to increase SOC sequestration in marginal croplands. [ABSTRACT FROM AUTHOR]

Management practices markedly impact carbon (C) cycling in forest plantations. However, the interactive effects of understory management and fertilization on soil greenhouse gas (GHG) fluxes and labile organic C pools remain unclear in forest plantations. To investigate the effects of understory replacement, fertilization, and their interaction on soil GHG fluxes and labile organic C pools in a Chinese chestnut plantation, we conducted a 2 × 2 factorial experiment over a 12-month field study with four treatments: Control (understory removed without understory replacement or fertilization), understory replacement (understory removed and seeded with Medicago sativa L., MS), fertilization (F), and MS + F. The GHG fluxes were determined using a static chamber/GC technique. The seasonal pattern of GHG fluxes did not change in any of the treatments in this one-year study; however, soil GHG fluxes, total global warming potential (GWP) of GHG fluxes, and soil organic C (SOC), water soluble organic C (WSOC), microbial biomass C (MBC), and NO 3 − –N concentrations were significantly affected by MS, F, and their interaction. In addition, GHG fluxes, GWP, and SOC, WSOC, MBC and NO 3 − –N concentrations were markedly increased by fertilization, regardless of the understory replacement treatment ( P < 0.05), but they were increased by understory replacement only in the fertilized plots. The GHG fluxes were correlated with soil temperature and WSOC in all plots ( P < 0.05), but not with soil moisture and MBC. These findings suggest that understory replacement likely is the optimum management technique for reducing/minimizing GHG fluxes, while F can enhance the effects of MS on increasing soil organic C and nutrient availability. We conclude that a combination of a moderate rate of fertilization and understory replacement with legume species should be adopted to increase soil C sequestration, maintain soil fertility and sustainably develop chestnut plantations. [ABSTRACT FROM AUTHOR]

Agroforestry land-use systems have significant potential for increasing soil carbon (C) storage and mitigating increases in atmospheric greenhouse gas (GHG) concentrations. We studied the impact of three agroforestry systems (hedgerow, shelterbelt, and silvopasture) on soil organic C (SOC) and nitrogen (N) in the 0-10 cm mineral layer, by comparing SOC and N distributions in whole soils and three particle-size fractions (<53, 53-250, 250-2000 μm) to assess the potential role of physical protection on soil C and N storage. We assessed thirty-five sites (12 hedgerows, 11 shelterbelts and 12 silvopastures), each comprised of 2 paired plots (forest and adjacent agricultural herbland), that were distributed along a 270 km long north-south soil/climate gradient in central Alberta, Canada. Across all sites, 48.4%, 28.5%, and 23.1% of SOC was found in the fine (<53 μm), medium (53-250 μm) and coarse fractions (250-2000 μm), respectively. Mean SOC in the whole soil was 62.5, 47.7 and 81.3 g kg-1 in hedgerow, shelterbelt and silvopasture systems, respectively. Soil C in the more stable fine fraction was 34.3, 28.8 and 29.3 g kg-1 in the hedgerow, shelterbelt and silvopasture systems, respectively. Within each agroforestry system, the forested land-use consistently had greater total SOC and SOC in all size fractions than the agricultural component. Our results demonstrate the potential for trees to increase soil C sequestration in agroforestry systems within the agricultural landscape. [ABSTRACT FROM AUTHOR]

Highlights: [•] Land use-change and subsequent intensive management decreased soil C pools. [•] Such practices increased soil total N storage and changed the chemical composition of soil organic C. [•] Practices that increase C input should be developed to enhance soil C storage. [Copyright &y& Elsevier]

Highlights: [•] Low pH and high and Ca2+ concentrations in precipitation. [•] Ca2+ and Mg2+ dominated streamflow had high and constant pH values. [•] The annual S input into the watershed was >40kgSha−1 year−1. [•] Ca2+ (>200kgha−1 year−1) and Mg2+ (⩾150) release was accelerated by acid deposition. [Copyright &y& Elsevier]

Highlights: [•] Nitrate in 28% of tested groundwater exceeded WHO's maximum contaminant level. [•] Cropland and landfill were the two largest sources of nitrate in groundwater. [•] A high resolution map of reactive nitrogen leakage to groundwater was constructed. [•] Anthropogenic factors explained majority of groundwater nitrate source variation. [•] Source appointment results matched well with the sampling data of groundwater nitrate. [ABSTRACT FROM AUTHOR]

Highlights: [•] Long-term fertilization, tillage, and understory removal decreased C pools. [•] Such practices also changed the chemical composition of soil organic C. [•] Labile organic C pools were linked to the chemical composition of soil organic C. [•] Alternative management practices may increase soil organic C storage. [ABSTRACT FROM AUTHOR]