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.

与外来物种的扩散过程类似，气候与土地利用变化引发的本地物种分布区转移，同样在众多生态系统中催生了全新的物种组合。这类本地物种分布区转移可能借助与外来物种类似的竞争优势机制得以实现，且对其所侵入的生态系统产生与外来物种入侵相近的影响。土壤生物群落（soil biota），尤其是其中的细菌与真菌，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，针对土壤生物群落如何影响（或受其影响）本地物种分布区转移的研究相对匮乏。
本研究聚焦于一种扩域原生灌木——洛氏蒿（Artemisia rothrockii），结合下一代测序（next-generation sequencing）与其他土壤生物、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。我们依托扩域梯度，配合灌木移除实验与结构方程模型（structural equation models），明确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，并沿扩域梯度改变了群落组成。土壤有机碳、氮与含水量随洛氏蒿的存在而升高，但该结果在扩域梯度不同区段存在差异。我们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影响。微生物（底物诱导）呼吸受到土壤有机氮、微生物多样性以及功能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作用。经过4年灌木移除后的土壤微生物群落组成，与灌丛间隙中的群落更为相似，而非灌丛下方的群落，这表明微生物群落具备恢复力。
综合与结论：本研究结果显示，本地物种的扩域过程可对土壤生物群落、土壤化学性质与水文环境产生重要影响，进而进一步作用于养分循环、枯落物分解等地下生态过程。本研究结合高通量测序（high-throughput sequencing）与结构方程模型的方法，为理解本地与外来物种的分布区扩张如何影响土壤生态系统的结构与功能提供了一种新颖且尚未被充分利用的研究路径。