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 examine 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, 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 modeling used here offers an exciting yet under-utilized 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（non-native species）的扩散类似，因气候与土地利用变化导致的本土物种（native species）分布范围变迁，同样在众多生态系统中催生了全新的物种组合。这类本土分布范围变迁，可能借助与外来物种获得竞争优势相似的机制得以推进，同时也可能对其入侵的生态系统造成类似的影响。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，目前针对土壤生物群如何影响本土物种分布范围变迁，或是受本土物种分布变迁影响的相关研究仍相对匮乏。本研究借助下一代测序技术（next-generation sequencing）结合其他土壤生物与非生物分析方法，探究本土分布扩张型蒿属灌木——洛氏蒿（Artemisia rothrockii）对地下非生物环境以及微生物群落结构与功能的影响。我们通过布设分布扩张梯度样带、开展灌木移除实验，并结合结构方程模型（structural equation models），解析这些相互关联过程的直接与间接驱动因子。洛氏蒿的定植提升了细菌与古菌的丰富度和多样性，并沿其分布扩张梯度改变了微生物群落组成。土壤有机碳、全氮与土壤含水量随洛氏蒿的存在而升高，但该效应沿扩张梯度存在差异。本研究未发现洛氏蒿与土壤pH值存在关联，然而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）受到土壤全氮、微生物多样性以及功能类群相对丰度的共同调控，这体现了洛氏蒿对微生物群落结构与功能的直接与间接影响。在洛氏蒿移除4年后，土壤微生物群落组成与灌木间隙中的群落更为相似，而非灌木冠幅下的群落，这表明微生物群落具有恢复力。综合分析：本研究结果表明，本土物种的分布扩张可对土壤生物群落、土壤化学性质与水文环境产生重要影响，进而进一步调控养分循环、枯落物分解等地下生态系统过程。本研究采用的高通量测序技术（high-throughput sequencing）与结构方程模型结合的研究方法，为解析本土与外来物种的分布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利用的研究路径。