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Abstract: Background: The rRNA operon (rrn) copy number is associated with protein synthesis and reproduction, reflecting microbial r- and K-life strategies and influencing soil ecosystem function. Although the positive relationship between microbial community-level rrn copy numbers and nutrient availability has been reported, the association between rrn copy number and soil stoichiometry or environmental stress remains largely unknown, particularly in the context of long-term nutrient inputs.Results: Using long-term (> 30 years) field experiments across three agro-ecosystems, we consistently found that N fertilization increased the microbial community-level rrn copy number. This increase was equivalently explained by soil CN stoichiometry (22%) and soil acidification (21%). Balanced soil CN stoichiometry favored the growth of N-dependent copiotrophs such as Bacilliand Flavobacteriia containing high rrn copy numbers (an average of 2.5), and enhanced their nutrient competition ability. Moreover, N fertilization-induced soil acidification, as an environmental stressor, increased the abundance of pH-negative responders such as Clostridia and Ktedonobacteria which also contained high rrn copy numbers (2.8), and threatened rare taxa with low rrn copy numbers.Conclusions: Consequently, our finding challenges the concept of microbial life-strategy regulation solely by nutrient availability, highlighting the novelty of significant contributions of soil stoichiometric balance and environmental stress to microbial strategies in agro-ecosystems under long-term nutrient inputs.

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Buffelgrass (Cenchrus ciliaris), an invasive perennial grass in arid regions of the United States, has drastically modified natural ecosystems. Understanding the aboveground–belowground links between buffelgrass invasion and soil microbial communities will be critical for developing a comprehensive understanding of arid ecosystems and for deploying successful control strategies. In a randomized block‐field experiment located in Tucson, AZ, U.S.A., we investigated the effects of buffelgrass removal via hand pulling and nitrogen addition (and their interaction) on soil microbial communities during an extreme drought (summer 2020). We found that experimental treatments did not significantly impact bacterial and archaeal community diversity and composition, while plant removal affected fungal community diversity and composition. In addition, the removal treatment increased the proportion of putative chitinolytic bacteria (genus Lysobacter) and decreased the proportion of putative fungal endophytes (genus Darksidea). Buffelgrass manual removal appeared to favor fungal endophyte death around and inside of leftover intact roots, which may result in an increase of chitinolytic bacteria thriving on the degradation of fungal cell walls. Overall, our results suggest that hand removal—which is a common type of buffelgrass control—can alter soil fungal communities and the proportion of certain microbial functional groups. As these changes could subsequently affect native plants, more research is needed to develop a comprehensive understanding of the effect of buffelgrass control efforts on target plants as well as surrounding ecosystem dynamics. [ABSTRACT FROM AUTHOR]

Legacy effects after the removal of invasive plants present significant challenges to restoration. The pivotal role of soil microbial communities in shaping these legacy effects is increasingly recognized, yet there is a lack of effective methods to mitigate altered microbial communities. In Point Reyes National Seashore (California), although the invaded European beachgrass (Ammophila arenaria [L.] Link) was successfully controlled by herbicide treatment, beachgrass litter remained undecomposed for over 5 years, leaving pronounced legacy effects on soil organic matter and microbial community composition. We hypothesized that soil inoculation from uninvaded dune scrub can accelerate the decomposition of beachgrass litter in herbicide‐treated sites by restoring the soil microbial communities and the abundance of microbial decomposers. Three litterbags containing European beachgrass litter or litter from two common shrubs at dune scrub were deployed into each plot to assess the impact of soil inoculation on litter decomposition rates. Our results revealed that soil inoculation, regardless of the inoculation level, did not accelerate the decomposition of European beachgrass. Only the decomposition of bush lupine litter, which had the highest litter quality among three types of litter, was accelerated at the highest inoculation level (approximately 11,880 g/m2). Additionally, soil inoculation increased the richness and compositional homogeneity of soil microbial communities, along with the relative abundances of wood saprotrophic fungi, soil saprotrophic fungi, and lichenized fungi. Although these findings demonstrate the potential of soil inoculation, the cost‐effectiveness of soil inoculation limits its feasibility in accelerating the delayed decomposition of European beachgrass litter in Point Reyes. [ABSTRACT FROM AUTHOR]