Abstract Legume-based silvopastoral systems drive the soil total bacterial, diazotrophic and ammonium-oxidizing bacterial communities and represent a sustainable strategy for preserving and restoring soil health. These systems increase the input of organic matter and nutrients and can drive the biodiversity and abundance of soil microorganisms, which leads to an intensification of nutrient cycling, mainly nitrogen. However, spatial and seasonal variations in the nitrogen-cycling bacterial community in soils under silvopastoral systems have not been well demonstrated. Therefore, we investigated the influence of silvopastoral systems with shrub-tree legumes on the structure, diversity, and abundance of total bacterial, diazotrophic and ammonium-oxidizing bacterial communities at different sites around the legumes in wet and dry seasons. The experimental design consisted of i) pure signalgrass (Brachiaria decumbens), ii) a silvopastoral system consisting of signalgrass intercropping with gliricidia (Gliricidia sepium) and iii) signalgrass intercropping with Sabia (Mimosa caesalpiniaefolia) in a randomized block design with three replications each. Samples were collected at zero (0 m), four (4 m) and eight meters (8 m) away from the legume rows and randomly in pure signalgrass. We used DGGE (denaturing gradient gel electrophoresis) and real-time quantitative PCR (qPCR) to investigate the influence of treatments on the structure, diversity, and abundance of total bacteria, diazotrophs and ammonium-oxidizing bacteria (AOB). In addition, the samples were subjected to physical and chemical analysis. Soils under silvopastoral systems presented higher acidity, cation-exchange capacity (CEC) and nitrate (NO3−-N) content than those of the soil under pure signalgrass cultivation. The soil community structures of total bacteria, diazotrophs and AOB were influenced by the silvopastoral system and were not similar among all distances from the legume row, particularly in the wet season. The diversity of the diazotrophic community was higher in silvopastoral systems than in pure signalgrass. There was a greater abundance of microbial communities in both silvopastoral systems, in which total bacteria and diazotrophs were more abundant in the dry season than in the wet season. Silvopastoral systems with shrub-tree legumes improved soil biological quality by promoting the abundance and spatial and temporal heterogeneity of the nitrogen-cycling bacterial community.

中文翻译：

---

固氮菌和氨氧化细菌对豆科林牧系统的空间和季节响应

摘要 基于豆科植物的林牧系统驱动土壤总细菌、固氮和氨氧化细菌群落，并代表了保护和恢复土壤健康的可持续策略。这些系统增加了有机物质和养分的输入，并可以推动土壤微生物的生物多样性和丰度，从而导致养分循环（主要是氮）的强化。然而，林牧系统下土壤中氮循环细菌群落的空间和季节变化尚未得到很好的证明。因此，我们研究了灌丛豆科林牧系统对湿季和旱季豆科植物周围不同地点的总细菌、固氮菌和氨氧化细菌群落的结构、多样性和丰度的影响。实验设计包括 i) 纯信号草 (Brachiaria decumbens)，ii) 林牧系统，由信号草与 gliricidia (Gliricidia sepium) 间作和 iii) 信号草与 Sabia (Mimosa caesalpiniaefolia) 间作组成，每个随机区组设计重复三个。在距豆科植物行的零 (0 m)、四 (4 m) 和八米 (8 m) 处并在纯信号草中随机收集样品。我们使用 DGGE（变性梯度凝胶电泳）和实时定量 PCR (qPCR) 来研究处理对总细菌、固氮菌和氨氧化细菌 (AOB) 的结构、多样性和丰度的影响。此外，还对样品进行了理化分析。林牧系统下的土壤呈现较高的酸度，阳离子交换能力 (CEC) 和硝酸盐 (NO3--N) 含量比纯信号草栽培土壤的含量高。总细菌、固氮菌和 AOB 的土壤群落结构受林牧系统的影响，并且在距豆科植物行的所有距离之间并不相似，特别是在雨季。林牧系统中固氮群落的多样性高于纯信号草。在两个林牧系统中微生物群落的数量都更多，其中干季的总细菌和固氮菌比湿季更丰富。具有灌木-豆科植物的林牧系统通过促进氮循环细菌群落的丰度和时空异质性来改善土壤生物质量。