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Anthropogenic activities have raised nitrogen (N) input worldwide with profound implications for soil carbon (C) cycling in ecosystems. The specific impacts of N input on soil organic matter (SOM) pools differing in microbial availability remain debatable. For the first time, we used a much‐improved approach by effectively combining the 13C natural abundance in SOM with 21 years of C3–C4 vegetation conversion and long‐term incubation. This allows to distinguish the impact of N input on SOM pools with various turnover times. We found that N input reduced the mineralization of all SOM pools, with labile pools having greater sensitivity to N than stable ones. The suppression in SOM mineralization was notably higher in the very labile pool (18%–52%) than the labile and stable (11%–47%) and the very stable pool (3%–21%) compared to that in the unfertilized control soil. The very labile C pool made a strong contribution (up to 60%) to total CO2 release and also contributed to 74%–96% of suppressed CO2 with N input. This suppression of SOM mineralization by N was initially attributed to the decreased microbial biomass and soil functions. Over the long‐term, the shift in bacterial community toward Proteobacteria and reduction in functional genes for labile C degradation were the primary drivers. In conclusion, the higher the availability of the SOM pools, the stronger the suppression of their mineralization by N input. Labile SOM pools are highly sensitive to N availability and may hold a greater potential for C sequestration under N input at global scale. [ABSTRACT FROM AUTHOR]

Peanut (Arachis hypogea L.) yield is dramatically declined by extreme weather stresses under climate change. Adjusting the sowing date and plant density are effective strategies to mitigate these stresses and improve peanut yield. However, a mechanistic understanding of the influence of environmental drivers and an optimized strategy have yet to be developed. Here, a 3‐year field experiment was conducted to evaluate the sowing date (April 25, early sowing; May 5, middle sowing; May 15, late sowing) and plant density (24, 30, and 36 plants m−2 as low, medium, and high) of peanut in the North China Plain. We found that higher pod yield was observed in the middle sowing (∼4492.4 kg ha−1) compared with the early and late sowing (∼3317.2 and 4088.1 kg ha−1, respectively). Meanwhile, the pod yield in high density (∼4162.5 kg ha−1) was 10.6% and 4.7% higher than low and medium density, respectively, mainly due to higher leaf area index. The relative peanut pod yield was positively correlated with the average minimum temperature 5 days before and after the flowering pegging stage, whilst it was negatively correlated with average maximum temperature 5 days before and after pod filling stage. Therefore, optimizing temperature conditions to improve the peanut yield can be achieved by adjusting the sowing date. In conclusion, sowing date and plant density manipulation constitute a useful method to mitigate heat and chilling stress and improve peanut yield. Core Ideas: Adjusting sowing date is recommended for peanut to adapt to heat and chilling stress.Higher peanut pod yield is observed in the middle sowing (May 5).High plant density (36 plants m−2) improves peanut yield due to higher leaf area index.Middle sowing and high plant density ensure a high peanut yield. [ABSTRACT FROM AUTHOR]

Aim: The Paris Climate Agreement is pursuing efforts to limit global warming to less than 2 °C in this century, but increasing evidence shows that temperatures are likely to rise up to 4.8 °C by 2100. This points to an urgent need to investigate how the temperature impact on microbial regulation will endanger soil organic matter stability under warming approaching or exceeding 2 °C. Location: Southern Germany and the globe. Time Period: 2010–2018. Major Taxa Studied: Soil organic matter stability and microbial adaptations. Methods: We analyzed soil properties and enzyme activities within (a) a long‐term field experiment with soil warming to below and above 2 °C (+1.6 vs. +3.2 °C), and (b) a literature review of 213 comparable studies globally (+0–2 vs. +2–4 °C). Results: The soil organic C (SOC) stock remained unchanged after 8 years under both warming magnitudes, whereas the labile C pool increased by 10% under >2 °C. Unlike the SOC pool, total N (TN) content increased by 20% under >2 °C as compared to ambient. A potential explanation for the increased TN content is linked to unbalanced processes of necromass formation and enzymatic decomposition. Warming induced faster microbial growth and turnover, but reduced catalytic efficiency and the enzyme‐mediated decomposition of oligosaccharides and polypeptides. This consequently caused N accumulation in microbial necromass. Although microbial regulation can maintain SOC at stable levels, warming exceeding 2 °C will change the projected effects of temperature on soil TN pools in the future. Early action to accomplish the 2 °C temperature goal can therefore markedly reduce the likelihood that large regions will face substantial increase of SOC availability, N accumulation and related climate impacts on C and N cycling. Main Conclusions: It is crucial to include microbial metabolic responses (i.e., faster microbial growth and turnover) to warming in global C and N cycle models to improve the prediction of climate warming scenarios. [ABSTRACT FROM AUTHOR]