Conversion of monoculture to agroforestry (integrating trees with crops) is promoted as a promising management in reducing N2O emissions from croplands. How agroforestry influences gross N2O emission (N2O + N2 from N2O reduction) and uptake (N2O reduced to N2) compared to monoculture is unknown. We used the 15N2O pool dilution technique to quantify these processes using soil cores (top 5 cm) incubated in the field with monthly measurements over two growing seasons (2018–2019) at two sites (each with paired agroforestry and monoculture) and one site with monoculture only. The unfertilized tree rows showed the lowest gross N2O emissions (P ≤ 0.002). Although tree rows occupied only 20% in agroforestry, gross N2O emissions tended to decrease by 6–36% in agroforestry (0.98–1.02 kg N2O‐N ha−1 yr−1) compared to monoculture (1.04–1.59 kg N2O‐N ha−1 yr−1). Gross N2O emissions were influenced by soil mineral N, soil respiration, and moisture content rather than by denitrification gene abundance. Soil gross N2O uptake was highest in the tree row and decreased with distance into crop rows (P = 0.012). The agroforestry tended to increase gross N2O uptake by 27–42% (0.38–0.44 kg N2O‐N ha−1 yr−1) compared to monoculture (0.30–0.31 kg N2O‐N ha−1 yr−1). In tree rows, soil gross N2O uptake correlated with nirK gene abundance which was indirectly influenced by the low mineral N‐to‐soil CO2‐C ratio. Adjusting the tree and crop areal coverages of agroforestry and optimizing fertilization can further augment the benefits of agroforestry in reducing emission and increasing uptake of N2O in soils.

In order to investigate the effects of N deposition on soil biochemistry in secondary forests, one N addition experiment was conducted in a secondary evergreen broad-leaved forest in the western edge of Sichuan Basin, with the highest level of background N deposition (about 95 kg N ha−1 yr−1) in China. Three N treatment levels (+0, +50, +150 kg N ha−1 yr−1) were monthly added to soil surface in this forest beginning in April 2013. Soil biochemistry and root biomass of the 0–10 cm soil horizon were measured from May 2014 to April 2015. Soil respiration was measured for two years (September 2013 to August 2015). It was showed that N additions were correlated to significantly lower soil pH, microbial biomass C (MBC) concentration, MBC/microbial biomass N (MBN) ratio, root biomass, and soil respiration rate, and significantly higher concentrations of ammonium (NH4 +) and nitrate (NO3 −). These results indicate that N additions had a significant effect on the size of soil microbial community. In addition, soil C storage may potentially increase due to the dropped soil C release under N addition.

Intensively managed open croplands are highly productive but often have deleterious environmental impacts. Temperate agroforestry potentially improves ecosystem functions, although comprehensive analysis is lacking. Here, we measured primary data on 47 indicators of seven ecosystem functions in croplands and 16 indicators of four ecosystem functions in grasslands to assess how alley-cropping agroforestry performs compared to open cropland and grassland. Carbon sequestration, habitat for soil biological activity, and wind erosion resistance improved for cropland agroforestry (P ≤ 0.03) whereas only carbon sequestration improved for grassland agroforestry (P < 0.01). In cropland agroforestry, soil nutrient cycling, soil greenhouse gas abatement, and water regulation did not improve, due to customary high fertilization rates. Alley-cropping agroforestry increased multifunctionality, compared to open croplands. To ameliorate the environmental benefits of agroforestry, more efficient use of nutrients is required. Financial incentives should focus on conversion of open croplands to alley-cropping agroforestry and incorporate fertilizer management.

&lt;p&gt;Monoculture cropland is a major contributor to agriculture-related sources of N&lt;sub&gt;2&lt;/sub&gt;O emission, a potent greenhouse gas and an agent of ozone depletion. Cropland agroforestry has the potential to minimize deleterious environmental impacts. Presently, there is no systematic comparison of soil N&lt;sub&gt;2&lt;/sub&gt;O emission between cropland agroforestry (CAF) and monoculture systems (MC) in Western Europe. Our study aimed to (1) quantify the spatial-temporal dynamics of soil N&lt;sub&gt;2&lt;/sub&gt;O fluxes, and (2) determine their soil controlling factors in CAF and MC. We selected three sites with different soil types (Phaeozem, Cambisol, and Arenosol) in Germany. Each site has paired CAF and MC (agroforestry sites consisted of 12-m wide tree row and 48-m wide crop row and were established in 2007, 2008 and 2019 in these soil types, respectively). In each management system at each site, we had four replicate plots. In the CAF, we conducted measurements in the tree row and within the crop row at 1 m, 7 m, and 24 m from the tree row. We measured soil N&lt;sub&gt;2&lt;/sub&gt;O fluxes monthly over 2 years (March 2018&amp;#8210;February 2020) using static vented chambers method. Following gas sampling, we also measured soil temperature, water-filled pore space (WFPS), and mineral N (NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt; and NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;) within the same day. Across all sites, soil moisture and N availability were major drivers of soil N&lt;sub&gt;2&lt;/sub&gt;O fluxes. Both CAF and MC were net sources of soil N&lt;sub&gt;2&lt;/sub&gt;O at all sites. At the site with Phaeozem soil, annual soil N&lt;sub&gt;2&lt;/sub&gt;O emissions from CAF in both years (1.84 &amp;#177; 0.35 and 1.17 &amp;#177; 0.30 kg N ha&lt;sup&gt;&amp;#8722;&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; yr&lt;sup&gt;&amp;#8722;&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt;) were greater than MC (0.89 &amp;#177; 0.09 and 0.34 &amp;#177; 0.05 kg N ha&lt;sup&gt;&amp;#8722;&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; yr&lt;sup&gt;&amp;#8722;&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt;) (&lt;em&gt;P&lt;/em&gt; = 0.03). At the site with Cambisol soil, annual soil N&lt;sub&gt;2&lt;/sub&gt;O emission did not differ between MC (0.49 &amp;#177; 0.07 kg N ha&lt;sup&gt;&amp;#8722;&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; yr&lt;sup&gt;&amp;#8722;&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt;) and CAF (0.73 &amp;#177; 0.13 kg N ha&lt;sup&gt;&amp;#8722;&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; yr&lt;sup&gt;&amp;#8722;&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt;) in 2018/2019 (&lt;em&gt;P&lt;/em&gt; = 0.20) whereas in 2019/2020 MC was 134% greater than CAF (2.92 &amp;#177; 0.45 and 1.25 &amp;#177; 0.08 kg N ha&lt;sup&gt;&amp;#8722;&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; yr&lt;sup&gt;&amp;#8722;&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt;, respectively; &lt;em&gt;P&lt;/em&gt; = 0.03). The inter-annual differences were largely related to crop types and to climate conditions. At the site with Arenosol soil, there was no difference between CAF and MC. Our results indicated that CAF may decrease, maintain and/or increase soil N&lt;sub&gt;2&lt;/sub&gt;O emissions compared to MC depending on tree age, soil characteristics, management and precipitation.&lt;/p&gt;

Extensive mining of rare earth deposits has caused severe soil erosion, resulting in the degradation of plant–soil systems and the reduction in microbial diversity. Combined ecological remediation technology is the key method of vegetation reconstruction and ecological restoration in abandoned tailings. In this study, the effects of different cover crops–biochar–organic fertilizer and biochar–organic fertilizer treatments on soil fungal communities in rare earth tailings soil were analysed using high-throughput sequencing technology. Linear discriminant analysis effect size (LEfSe) was used to analyse saprophytic, mycorrhizal, and potential pathogenic fungi in soils after different combined remediations. Moreover, the effects of soil environmental factors on fungal community species’ composition were analysed by redundancy analysis (RDA) and variance partitioning analysis (VPA) after different combined remediations. LEfSe indicated a risk of citrus pathogenicity by Diaporthaceae indicator fungi after biochar–organic fertilizer combined treatment. RDA and VPA revealed that pH was the main environmental factor affecting the fungal community in the different combined remediation treatments. Additionally, the Paspalum wettsteinii cover crops–biochar–organic fertilizer and biochar–livestock manure treatments were more conducive to arbuscular mycorrhizal fungi recruitment. We also clarified the fungal community composition structure, soil environmental factors, and fungal community relationships in rare earth tailings soil after different combined remediation treatments.

A pot experiment was conducted to study the effect of decomposing Cinnamomum septentrionale leaf litter on the growth of maize. In this study, the morphological traits of maize were significantly inhibited when the leaf litter amount reached or exceeded 40 g per pot; Furthermore, during the early growth stage or with a large amount of litter addition, the pigment contents were inhibited by C. septentrionale leaf litter. Gas chromatography-mass spectrometry was used to determine the volatile substances of leaf litter and 34 compounds were identified, several of which were reported to be phytotoxic. In conclusion, the leaf litter of C. septentrionale showed a strong allelopathic effect on the growth of maize. Thus, it is better to avoid the growing of maize under or near the C. septentrionale plantation unless the leaf litter could be eliminated in time or other effective leaf litter processing methods could be implemented.

The disordered mining of ion‐type rare soil has caused significant ecological and environmental problems. Arbuscular mycorrhizal fungi (AMF) can promote soil quality, providing new ideas about the ecological restoration of degraded soil. In this study, the degraded ion‐type rare earth tailing soils in Xinfeng County, southern Jiangxi Province, was used as a research object. The soil was subjected to different restoration methods (biochar + fly ash + surface vegetation planting) for 2 yr. A total of six treatments were set up in this experiment, and the phospholipid fatty acid method was used to determine the microbial community structure and biomass of the rhizosphere soil of navel oranges [Citrus sinensis (L.) Osbeck] treated with different amounts of biochar (0, 1, and 5%) plus surface mulching (Trifolium repens L.) or soil without plants. Additionally, a pot experiment was conducted to study the effects of single and double inoculation of AMF (Septoglomus viscosum and Claroideoglomus claroideum) on plant growth and soil improvement under various P levels (0 and 50 mg kg–1) in ion‐type rare soil. The results showed that the microbial biomass (fungi, Gram‐positive bacteria, Gram‐negative bacteria, actinomycetes, AMF, and protozoa) when T. repens was present was noticeably higher than that when T. repens was not present. In particular, the biomass of the AMF under the T. repens treatment with 5% biochar (1.28 nmol g–1) was 34.38% higher than that under the 5% biochar treatment without plants (p < .05). Furthermore, the pot experiments showed that AMF inoculation significantly increased the plant biomass, single AMF inoculation significantly increased soil P in the absence of basal P, and double inoculation significantly increased the glomalin (a component of soil organic matter) content. Our findings indicated that the soil microbial biomass was greatly affected by planting T. repens and adding biological modifiers. These composite remediation methods could provide an increasing number of C sources for the soil microbial community and could effectively improve soil quality and plant growth.

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