Aims

The impacts associated with litter decomposition in intensive cropping on eco-enzymatic stoichiometry and microbial nutrient limitation are still under debate.

Methods

To evaluate the dynamics of carbon (C), nitrogen (N), and phosphorus (P) in response to different litter additions, we investigated the variations in soil nutrients (nitrate N, ammonium N, available P), carbon mineralization rate, soil microbial biomass, and extracellular eco-enzymatic activities (alkaline phosphatase enzyme, AP; β-1,4-glucosidase, BG; β-1,4-N-acetyl-glucosaminidase, NAG; l-leucine aminopeptidase, LAP) of soils inoculated with different orchard litters (citrus leaf and alfalfa leaf) and their mixtures in a microcosm experiment.

Results

Litter addition improved soil nutrients and microbial biomass. During the plant litter decomposition process, soil BG and AP continuously increased in the first 7 days and then decreased, while NAG and ALP reached a peak at the 14th day and then continuously reduced. Litter type was the main factor controlling eco-enzymatic activities and the ratios of eco-enzymatic activities (stoichiometry). The additions of alfalfa leaf enhanced soil nutrients and eco-enzymatic activities more than citrus leaf alone. Enzyme vector analysis revealed that soil microbial communities were co-limited by C and P during litter decomposition. Enzyme vector analysis showed that all vector angles were > 45°, suggesting that soil microorganisms were more limited by P than by N during the decomposition process. Random forest model revealed that litter type, cumulative mineralized C, and microbial biomass were the best predictor of enzyme vector angle.

Conclusions

The present study indicates that soil microbial activity (microbial biomass and enzyme activities) was sensitive to litter decomposition in orchards, and litter additions would relieve microbial nutrient limitations in orchards. Alfalfa litter played positive roles in improving soil nutrients and regulating nutrient limitation in citrus orchards, which would help manage highly intensive cropping and develop organic orchards for smart farming.

中文翻译：

---

植物凋落物质量调节柑橘园土壤生态酶化学计量和微生物养分限制

宗旨

集约化种植中凋落物分解对生态酶化学计量学和微生物养分限制的影响仍在争论中。

方法

为了评估碳 (C)、氮 (N) 和磷 (P) 响应不同凋落物添加的动态，我们研究了土壤养分（硝酸盐 N、铵态氮、有效磷）、碳矿化率、土壤接种土壤的微生物生物量和细胞外生态酶活性（碱性磷酸酶，AP；β-1,4-葡萄糖苷酶，BG；β-1,4-N-乙酰氨基葡萄糖苷酶，NAG；l-亮氨酸氨基肽酶，LAP）在微观实验中使用不同的果园凋落物（柑橘叶和苜蓿叶）及其混合物。

结果

添加凋落物可改善土壤养分和微生物生物量。在植物凋落物分解过程中，土壤BG和AP在前7天持续升高，然后下降，而NAG和ALP在第14天达到峰值，然后持续降低。凋落物类型是控制生态酶活性和生态酶活性比例（化学计量）的主要因素。添加苜蓿叶比单独添加柑橘叶更能增强土壤养分和生态酶活性。酶载体分析表明，在凋落物分解过程中，土壤微生物群落受到 C 和 P 的共同限制。酶载体分析表明，所有矢量角度均 > 45°，表明土壤微生物在分解过程中受 P 的限制比 N 更受限制。随机森林模型揭示了凋落物类型，

结论

本研究表明土壤微生物活性（微生物生物量和酶活性）对果园凋落物分解敏感，添加凋落物可以缓解果园微生物养分限制。苜蓿凋落物在改善柑橘园土壤养分和调节养分限制方面发挥了积极作用，有助于管理高度集约化种植和发展有机果园以实现智能农业。