Protists, as the core component of the soil microbiome, may play an important role in forest succession by altering soil nutrient cycling and plant performance. However, knowledge of how protists change with plant succession is extremely limited. To illustrate protistan community dynamics following plant succession in subalpine natural and planted ecosystems, we used high-throughput sequencing to identify protists in rhizosphere and bulk soils at different successional stages, and the effects of soil abiotic and biotic factors on protists were analysed. Overall, the α-diversity and community composition of protists differed significantly between natural and planted ecosystems, but not between rhizosphere and bulk soils. Moving along the successional gradient, the richness and diversity of protists in rhizosphere and bulk soils of natural ecosystems, as well as the richness of functional taxa (i.e., consumers, parasites and phototrophs), gradually increased. In contrast, the richness of protists and functional taxa in the plantations was generally lowest in the old stands (75 years). The community composition of protists in rhizosphere and bulk soils of these two ecosystems varied significantly among successional stages, and their community composition variation was positively correlated with the time interval of successional stages, indicating that community dynamics exhibited directionality along successional gradients. Soil abiotic and biotic factors jointly regulate protistan α-diversity and community composition, and forest succession regulates functional taxa through multiple pathways. However, the key influencing factors and specific regulatory pathways are not consistent across different ecosystems, soil types and functional taxa. Therefore, our study has revealed that protistan community assembly was distinct along two separate successional gradients, indicating potential functional differences. These results provide a basis for the development of future forest management measures.

中文翻译：

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亚高山天然林和人工林植物演替过程中土壤因子对原生生物群落动态的影响

原生生物作为土壤微生物组的核心组成部分，可能通过改变土壤养分循环和植物性能在森林演替中发挥重要作用。然而，关于原生生物如何随着植物演替而变化的知识极其有限。为了阐明亚高山自然和种植生态系统植物演替后的原生生物群落动态，我们利用高通量测序技术鉴定了不同演替阶段根际和大块土壤中的原生生物，并分析了土壤非生物和生物因素对原生生物的影响。总体而言，原生生物的α多样性和群落组成在自然生态系统和人工生态系统之间存在显着差异，但在根际和土壤之间没有显着差异。沿着演替梯度，自然生态系统根际和土体土壤中原生生物的丰富度和多样性，以及功能类群（即消费者、寄生虫和光养生物）的丰富度逐渐增加。相比之下，人工林中原生生物和功能类群的丰富度通常在老林（75年）中最低。这两个生态系统根际和土体土壤中的原生生物群落组成在演替阶段存在显着差异，其群落组成变化与演替阶段的时间间隔呈正相关，表明群落动态沿演替梯度呈现方向性。土壤非生物和生物因素共同调节原生生物α多样性和群落组成，森林演替通过多种途径调节功能类群。然而，不同生态系统、土壤类型和功能类群的关键影响因素和具体调控途径并不一致。因此，我们的研究表明，原生生物群落组装沿着两个独立的演替梯度是不同的，表明潜在的功能差异。这些结果为未来森林管理措施的制定提供了基础。