Conserving the remaining savanna ecosystems in the Brazilian savanna (Cerrado) — a global biodiversity hotspot that stores carbon and provides water to a large portion of South America — requires understanding the ecological processes maintaining their function. Nutrient cycling supports savanna function via plant litter production and decomposition by soil fauna, releasing nutrients for plant and soil organism uptake. Soil biodiversity and biogeochemistry linkages with litter dynamics in Neotropical savannas under a changing climate are poorly understood. Here, we combined two years of rainfall seasonality, leaf and wood litter production and decomposition with soil epigeic fauna abundance — the number of ground-surface dwelling invertebrates collected through pitfall traps — taxa richness, Shannon's diversity and Pielou's evenness, and 16 soil biogeochemical variables measured in 12 plots of preserved savanna. Rainfall seasonality modulated the mean soil epigeic fauna diversity and evenness across all plots, which were highest in the rainy season, in contrast to litterfall rates, which peaked in the dry season. In the dry season (April to September), the Formicidae family was the most abundant with 50% of all individuals, while in the rainy season (October to March), the Isoptera order was the most abundant with approximately 39% of individuals. Wood litter decomposition grouped with annual Hemiptera abundance, co-varying with soil epigeic fauna diversity and evenness per plot and against soil fertility variables. Leaf litter decomposition co-varied with the total epigeic fauna abundance and soil pH. We speculate that the specific need to decompose wood litter may be associated with a greater need for diversity than an abundance of soil epigeic fauna. Our work highlights the role of rainfall seasonality on soil biodiversity and physicochemistry, which is also tightly linked with litter production and decomposition. This study advances our understanding of the mechanisms governing nutrient cycling in savanna ecosystems on nutrient-impoverished soils, with implications for achieving sustainable conservation and restoration goals.

保护巴西稀树草原（塞拉多）剩余的稀树草原生态系统——一个全球生物多样性热点，为南美洲的大部分地区储存碳和提供水——需要了解维持其功能的生态过程。养分循环支持的稀树草原功能通过植物凋落物的产生和土壤动物分解，释放养分供植物和土壤生物吸收。对气候变化下新热带稀树草原的土壤生物多样性和生物地球化学与凋落物动态的联系知之甚少。在这里，我们将两年的降雨季节性、树叶和木材凋落物的产生和分解与土壤表生动物群丰度——通过陷阱陷阱收集的地表无脊椎动物的数量——分类群丰富度、香农多样性和皮洛的均匀度，以及 16 个土壤生物地球化学变量相结合在 12 个保存的稀树草原地块中测量。降雨季节性调节了所有地块的平均土壤表生动物多样性和均匀度，在雨季最高，而凋落物率在旱季达到顶峰。在旱季（4 月至 9 月），蚁科数量最多，占所有个体的 50%；而在雨季（10 月至 3 月），等翅目数量最多，占个体总数的 39%。枯枝落叶分解与半翅目年度丰度分组，与每个地块的土壤表生动物多样性和均匀度以及土壤肥力变量共同变化。凋落物分解与总表生动物群丰度和土壤 pH 值共同变化。我们推测，与丰富的土壤表生动物群相比，分解枯枝落叶的特定需求可能与对多样性的更大需求有关。我们的工作强调了降雨季节性对土壤生物多样性和物理化学的作用，这也与凋落物的产生和分解密切相关。