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Our knowledge of carbon (C) and nitrogen (N) dynamics during stand development is not only essential for evaluating the role of secondary forests in the global terrestrial C cycle, but also crucial for understanding long-term C—N interactions in terrestrial ecosystems. However, a comprehensive understanding of forest C and N dynamics over age sequence remains elusive due to the diverse results obtained across individual studies. Here, we synthesized the results of more than 100 studies to examine C and N dynamics during forest stand development. Our results showed that C accumulated in aboveground vegetation, litter and forest floor pools, while the mineral soil C pool did not exhibit significant changes in most studies. The rate of C changes declined with stand age and approached equilibrium during the later stage of stand development. The rate of N changes exhibited linear increases with that of C changes, indicating that N also accrued in various ecosystem components except mineral soil. These results demonstrate that substantial increases in C pools over age sequence are accompanied by N accretion in forest ecosystems. The concurrent C and N dynamics suggest that forest ecosystems may have an intrinsic ability to preclude progressive N limitation during stand development.

Background and aims While a limited number of studies have investigated cereal-legume temporary intercropping in organic systems, the potential for temporary intercropping to improve soil properties or cash crop yield/quality in conventional systems remains unknown. Methods A field experiment comparing monoculture wheat to wheat with a temporary (9 week) vetch intercrop was conducted in a water-limited environment. Wheat root growth and biomass, plant available water (PAW) and soil mineral nitrogen (N) were measured at anthesis (9 weeks after vetch termination) and grain yield/protein were determined at maturity. Soil parameters including soil total carbon (C) and N, hot water extractable C (HWC), water soluble C (WSC), citrate-extractable protein, microbial biomass carbon (MBC), and soil enzyme activities were also assessed. Results Compared to monoculture wheat, temporary vetch-wheat intercropping increased MBC, HWC and WSC by 37%, 15% and 7%, respectively, across the monitoring period. Temporary intercropping increased the activity of C- and N-acquiring enzymes by 45% compared to monoculture wheat. At anthesis, the intercrop treatment had 30 mm more PAW and an additional 20 kg mineral N ha −1 to 90 cm depth than the monoculture wheat. This didn’t result in higher grain yields, presumably because spring rainfall was adequate for grain filling, and didn’t increase grain protein, likely because the system wasn’t N-limited. Conclusion Higher mineral N and PAW under wheat-vetch intercrops at anthesis suggests temporary intercropping could increase wheat grain protein under the right conditions, and potentially increase grain yields in seasons with limited rainfall during grain filling.

Background and aimsSorghum (Sorghum bicolor) is able to exude allelochemicals with biological nitrification inhibition (BNI) capacity. Therefore, sorghum might be an option as cover crop since its BNI ability may reduce N pollution in the following crop due to a decreased nitrification. However, BNI exudation is related to the physiological state and development of the plant, so abiotic stresses such as drought might modify the rate of BNI exudation. Hence, the objective was to determine the effect of drought stress on sorghum plants’ BNI release.MethodsThe residual effects of sorghum crops over ammonia-oxidizing bacteria (AOB) were monitored in a 3-year field experiment. In a controlled-conditions experiment, sorghum plants were grown under Watered (60% WFPS) or Moderate drought (30% WFPS) conditions, and fertilized with ammonium sulphate (A), ammonium sulphate + DMPP (A+D), or potassium nitrate (KNO3−). Soil mineral N was determined, and AOB populations were quantified. Additionally, plant biomass, isotopic discrimination of N and C, and photosynthetic parameters were measured in sorghum plants.ResultsIn the driest year, sorghum was able to reduce the AOB relative abundance by 50% at field conditions. In the plant-soil microcosm, drought stress reduced leaf photosynthetic parameters, which had an impact on plant biomass. Under these conditions, sorghum plants exposed to Moderate drought reduced the AOB abundance of A treatment by 25% compared to Watered treatment.ConclusionThe release of BNI by sorghum under limited water conditions might ensure high soil NH4+-N pool for crop uptake due to a reduction of nitrifying microorganisms.

PurposeIntensification of farming means that organic soils, of low phosphorus (P) holding capacity, are being brought into production. Consequently, farmers may have to adjust their fertiliser application regimes to reduce environmental risk. The aim of this paper is to test the hypothesis that overall loads of P and nitrogen are smaller when applications are split in two compared to a single application.Materials and methodsA laboratory column experiment was conducted in which two soils, one organic and one mineral, were exposed to dairy slurry applications of 15, 30 and 55 kg P ha−1 applied in one single application or split into two applications. The columns were uniformly irrigated weekly with 160 mL of distilled water (equivalent to average precipitation in Ireland) and the leached water was analysed for nutrients.Results and discussionThere were no significant cumulative P loads in the leached water for any soil type or treatment (minimum and maximum values ranging from 0.04 to 0.12 kg dissolved reactive phosphorus (DRP) ha−1 and 0.09 to 0.14 kg DRP ha−1 for the organic and mineral soil, respectively, and 1.5 to 1.8 kg total phosphorus (TP) ha−1 and 1.8 to 2.9 kg TP ha−1 for the organic and mineral soil, respectively). There was high ammonium-N retention within the organic soil (0.2–0.4 kg ha−1, compared to 15.0–36.8 ha−1 for mineral soils in the leached water). Nitrate–N loads were higher from the organic soil (6.5–105.3 ha−1) than the mineral soil (9.7–17.4 ha−1), although for both soils, loads from the amended columns were lower than the controls (110.7 and 20.1 NO3-N ha−1 for the organic and mineral soil, respectively).ConclusionsThe overall finding of this study was that split slurry applications had little effect on nutrient exports when compared to single applications, making the amounts of slurry applied, and not the application regime, the predominant factor in nutrient loss.

Changes in forest composition as a result of forest management, natural disturbances, and climate change may affect the accumulation of soil organic carbon (SOC). We examined the influence of common boreal tree species (trembling aspen, black spruce, and jack pine), either in pure stands or in conifer-broadleaf mixtures, on the amount, distribution, and quality of SOC in two regions of the Canadian boreal biome. Long-term laboratory incubations were used to assess SOC quality by quantifying proportions of fast carbon (C) (that is, proportion of total C released during the first 100 days of incubation) and active C (that is, modeled proportion of total C that can be potentially released). Total amounts of SOC did not differ between stand types, but the effects of stand type on SOC stocks and quality differed with soil depth. Among stand types, aspen stands had the greatest relative proportion of total SOC in deeper mineral layers and the lowest amount of active C in the organic layer. For these reasons, the SOC stock that developed under aspen was more stable than in the other stand types. Although black spruce stands allowed a greater accumulation of SOC in surface layers, these stocks, however, might become more vulnerable to extra losses if environmental conditions are to become more favorable to decomposition in the future. Our work highlights that boreal forest composition influences the stability of SOC stocks and how climate change could alter this large C pool.

Background and Aims Litter decomposition is poorly investigated in young temperate alley cropping (AC) systems but may be an integrative indicator to explore the early effect of trees on overall biological activity throughout soil profile. We evaluated the effect of four-year-old trees on recalcitrant-rooibos and labile-green tea mass loss at different soil depths at the Ramecourt AC experimental site. Methods In May 2021, tea bags were inserted within aluminum ingrowth bags and incubated at three depths 1.5 m from a reference tree for 6 months. The tea mass loss variability was analyzed according to factors: type of tea, type of system (AC, sole-crop control or CC and forest plantation control or FC), soil incubation depth, tree species and was correlated with fine roots and soil parameters. Results At 30 cm depth, the mass loss was significantly lower for rooibos than green tea regardless of the type of system, whereas at 50 cm and 100 cm depth, this difference was observed only in AC and FC. We observed a lower rooibos mass loss in AC than in CC at 100 cm depth. At 30 cm depth, soil mineral nitrogen content explained 23% of the rooibos tea mass loss variability whereas, soil organic matter content and fine root biomass within tea bags accounted for 50% of green tea mass loss variability. Conclusion We highlighted the ability of AC to slow recalcitrant litter decomposition in depth, however further works are needed to elucidate the processes leading to retarded decomposition.

Contemporary trends in horticulture are aimed at limiting the use of mineral fertilizers to the necessary minimum, which is to guarantee adequate profitability of production while maintaining high-quality fruit and at the same time preventing environmental pollution. Thus, in the presented study, we investigate the effect of diversified nitrogen fertilization on soil mineral nitrogen content during vegetation season, yielding of apple trees and the nutritional status of apple leaves and fruits. We compared several ammonium nitrate treatments as well as growth without fertilization as a control. The results of our study show that under the conditions of humus-rich soils and with appropriate agrotechnics, N mineralization from the organic matter available in the soil may completely cover demand of apple trees for this component. Achieved outcomes clearly revealed that nitrogen fertilization in the amount of 100 kg N · ha−1 on the entire soil surface carries a real risk of groundwater contamination, and the same nitrogen dose applied within the grassland does not bring any production effects, therefore it should be considered as unjustified. Obtained results revealed that in a rationally managed, fully fruiting apple orchard, the annual dose of N should not exceed 50 kg N∙ha−1. This dosage of N should fully secure the nutritional needs of apple trees, guaranteeing their high yield and complete safety for the environment. What is important is, nitrogen fertilization strongly affects macroelemental composition of apple leaves and fruits.

1. Plant diversity can increase nitrogen cycling and decrease soil-borne pests, which are feedback mechanisms influencing subsequent plant growth. The relative strength of these mechanisms is unclear, as is the influence of preceding plant quantity and quality. Here, we studied how plant diversity in space and time influences subsequent crop growth. 2. During 2 years, we rotated two main crops (Avena sativa, Cichorium endivia) with four winter cover crop (WCC) species in monocultures and mixtures. We hypothesized that, relative to monocultures, WCC mixtures promote WCC biomass (quantity) and nitrogen concentration (quality), soil mineral nitrogen, soil organic matter, and reduce plant-feeding nematode abundance. Additionally, we predicted that preceding crops modified WCC legacies. By structural equation modelling (SEM), we tested the relative importance of WCC shoot biomass and nitrogen concentration on succeeding crop productivity directly and indirectly via nitrogen cycling and root-feeding nematode abundance. 3. WCC shoot biomass, soil properties and succeeding Avena productivity were affected by first-season cropping, whereas subsequent Cichorium only responded to the WCC treatments. WCC mixtures' productivity and nitrogen concentration showed over- and under-yielding, depending on mixture composition. Soil nitrogen and nematode abundance did not display WCC mixture effects. Soil organic matter was lower than expected after Raphanus sativus + Vicia sativa mixture. Subsequent Avena productivity depended upon mixture composition, whereas final Cichorium productivity was unresponsive to WCC mixtures. SEM indicated that WCC legacy effects on subsequent Avena (R² = 0.52) and Cichorium (R² = 0.59) productivity were driven by WCC biomass and nitrogen concentration, although not by the quantified soil properties. 4. Synthesis and applications. Through understanding plant-soil feedback, legacy effects of plant species and species mixtures can be employed for sustainable management of agro-ecosystems. Biomass and nitrogen concentration of plants returned to the soil stimulate subsequent plant productivity. Winter cover crop quantity and quality are both manipulable with mixtures. The specificity of spatial and temporal diversity effects warrants consideration of plant species choice in mixtures and rotations for optimal employment of beneficial legacy effects.

Intrinsic soil properties have been shown to mediate the effects of ectomycorrhizal (ECM) fungi and their associated trees on soil organic matter (SOM) and nitrogen (N) cycling, but variation in the contribution of fungal communities to ECM effects across different forests remains uncertain. To investigate the potential role of fungal communities in driving observed variation in ECM effects, we characterized fungal community composition and function using DNA sequence variability of the ITS2 region of the fungal rRNA operon and measured chemical properties of forest floor leaf litter, soil organic horizon, and soil mineral horizons (0–5cm, 15–20 cm depth) beneath ECM-associated Oreomunnea mexicana focal trees. We sampled beneath focal trees in arbuscular mycorrhizal (AM)- and ECM-dominated stands within four adjacent watersheds that differed in underlying soil pH and fertility. We found that overall fungal community composition and the ratio of ECM to saprotrophic fungi differed between AM- and ECM-dominated stands in the lowest pH and fertility watershed but were similar between stand mycorrhizal types in the highest pH and fertility watershed. Patterns in fungal community composition and function aligned with patterns in N isotopic composition of forest floor leaf litter and mineral soil, which could reflect greater ECM transfer of N to the trees and greater contribution of hyphal biomass to SOM in the lowest pH and fertility watershed. Overall, our results suggest the potential for watershed-scale variation in soil pH and fertility to mediate fungal community contributions to variation in ECM effects on biogeochemical syndromes.

Interactions of dissolved organic matter (DOM) with soil minerals, such as metal oxides and clays, involve various sorption mechanisms and may lead to sorptive fractionation of certain organic moieties. While sorption of DOM to soil minerals typically involves a degree of irreversibility, it is unclear which structural components of DOM correspond to the irreversibly bound fraction and which factors may be considered determinants. To assist in elucidating that, the current study aimed at investigating fractionation of DOM during sorption and desorption processes in soil. Batch DOM sorption and desorption experiments were conducted with organic matter poor, alkaline soils. Fourier‐transform infrared (FTIR) and UV‐Vis spectroscopy were used to analyze bulk DOM, sorbed DOM, and desorbed DOM fractions. Sorptive fractionation resulted mainly from the preferential uptake of aromatic, carboxylic, and phenolic moieties of DOM. Soil metal‐oxide content positively affected DOM sorption and binding of some specific carboxylate and phenolate functional groups. Desorptive fractionation of DOM was expressed by the irreversible‐binding nature of some carboxylic moieties, whereas other bound carboxylic moieties were readily desorbed. Inner‐sphere, as opposed to outer‐sphere, ligand‐exchange complexation mechanisms may be responsible for these irreversible, as opposed to reversible, interactions, respectively. The interaction of aliphatic DOM constituents with soil, presumably through weak van der Waals forces, was minor and increased with increasing proportion of clay minerals in the soil. Revealing the nature of DOM‐fractionation processes is of great importance to understanding carbon stabilization mechanisms in soils, as well as the overall fate of contaminants that might be associated with DOM.