Data from: Direct and indirect effects of native range expansion on soil microbial community structure and function

Analogous to the spread of non-native species, shifts in native species’ ranges resulting from climate and land use change are also creating new combinations of species in many ecosystems. These native range shifts may be facilitated by similar mechanisms that provide advantages for non-native species and may also have comparable impacts on the ecosystems they invade. Soil biota, in particular bacteria and fungi, are important regulators of plant community composition and below-ground ecosystem function. Compared to non-native plant invasions, there have been relatively few studies examining how soil biota influence – or are influenced by – native species range shifts. Here, we examined how a native range-expanding sagebrush species (Artemisia rothrockii) affects below-ground abiotic conditions and microbial community structure and function using next-generation sequencing coupled with other biotic and abiotic soil analyses. We utilized a range-expansion gradient, together with a shrub removal experiment and structural equation models, to determine the direct and indirect drivers of these interconnected processes. Sagebrush colonization increased bacterial and archaeal richness and diversity and altered community composition across the expansion gradient. Soil organic C and N and soil moisture increased with sagebrush presence; however, results varied across the expansion gradient. We found no relationship between sagebrush and soil pH; however, pH strongly influenced microbial richness and diversity. Microbial (substrate-induced) respiration was influenced by soil organic N, as well as microbial diversity and functional group relative abundances, highlighting direct and indirect effects of sagebrush on microbial community structure and function. Microbial community composition of soils after 4 years of sagebrush removal was more similar to communities in shrub interspaces than underneath shrubs, suggesting microbial community resilience. Synthesis. Our results suggest that native range expansions can have important impacts on soil biological communities, soil chemistry and hydrology which can further impact below-ground ecosystem processes such as nutrient cycling and litter decomposition. The combination of high-throughput sequencing and structural equation modelling used here offers an exciting yet underutilized approach to understanding how both native and non-native species’ range expansions may affect the structure and function of soil ecosystems.与外来物种的扩散类似，由气候与土地利用变化引发的本地物种分布范围转移，同样在众多生态系统中造就了全新的物种组合。此类本地物种分布范围转移，或可借助与外来物种获得竞争优势相同的机制得以实现，且对其所侵入的生态系统可能产生相似的影响。 土壤生物群（soil biota），尤其是细菌与真菌，是调控植物群落组成与地下生态系统功能的关键因子。相较于外来植物入侵，针对土壤生物群如何影响本地物种分布范围转移，或受其影响的研究相对较少。 本研究以一种正在发生分布范围扩张的本地蒿属物种——罗斯罗克蒿（Artemisia rothrockii）为研究对象，采用下一代测序（next-generation sequencing）结合其他土壤生物与非生物分析手段，探究其对地下非生物环境以及微生物群落结构与功能的影响。我们通过构建分布范围扩张梯度，结合灌木移除实验与结构方程模型（structural equation models），明确了这些相互关联过程的直接与间接驱动因子。 蒿属灌木的定植提升了细菌与古菌的丰富度和多样性，并在整个分布扩张梯度上改变了微生物群落组成。伴随蒿属灌木的定植，土壤有机碳、氮含量与土壤含水量均有所升高，但该效应在不同扩张梯度间存在差异。本研究未发现蒿属灌木与土壤pH值存在显著关联，但pH值对微生物丰富度和多样性具有显著调控作用。微生物底物诱导呼吸（substrate-induced respiration）受到土壤有机氮、微生物多样性以及功能类群相对丰度的共同影响，这凸显了蒿属灌木对微生物群落结构与功能的直接与间接调控效应。在移除蒿属灌木4年后，土壤微生物群落组成与灌木间空地的群落更为相似，而非灌木冠幅下方的群落，这表明土壤微生物群落具备恢复力。 研究总结：本研究结果表明，本地物种的分布范围扩张可对土壤生物群落、土壤化学性质与水文状况产生重要影响，进而进一步作用于养分循环、枯落物分解等地下生态系统过程。本研究所采用的高通量测序与结构方程模型（structural equation models）相结合的研究方案，为解析本地与外来物种的分布范围扩张如何影响土壤生态系统的结构与功能提供了一种极具前景但尚未得到充分应用的研究路径。