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Poly(butylene succinate-co-adipate) (PBSA) degradation and its plastisphere microbiome in cropland soils have been studied; however, such knowledge is limited in the case of forest ecosystems. In this context, we investigated: i) the impact of forest types (conifer and broadleaved forests) on the plastisphere microbiome and its community assembly, ii) their link to PBSA degradation, and iii) the identities of potential microbial keystone taxa. We determined that forest type significantly affected microbial richness (F = 5.26-9.88, P = 0.034 to 0.006) and fungal community composition (R 2  = 0.38, P = 0.001) of the plastisphere microbiome, whereas its effects on microbial abundance and bacterial community composition were not significant. The bacterial community was governed by stochastic processes (mainly homogenizing dispersal), whereas the fungal community was driven by both stochastic and deterministic processes (drift and homogeneous selection). The highest molar mass loss was found for PBSA degraded under Pinus sylvestris (26.6 ± 2.6 to 33.9 ± 1.8 % (mean ± SE) at 200 and 400 days, respectively), and the lowest molar mass loss was found under Picea abies (12.0 ± 1.6 to 16.0 ± 0.5 % (mean ± SE) at 200 and 400 days, respectively). Important fungal PBSA decomposers (Tetracladium) and atmospheric dinitrogen (N 2 )-fixing bacteria (symbiotic: Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium and Methylobacterium and non-symbiotic: Mycobacterium) were identified as potential keystone taxa. The present study is among the first to determine the plastisphere microbiome and its community assembly processes associated with PBSA in forest ecosystems. We detected consistent biological patterns in the forest and cropland ecosystems, indicating a potential mechanistic interaction between N 2 -fixing bacteria and Tetracladium during PBSA biodegradation., Competing Interests: Declaration of competing interest The authors declare that they have no competing interests. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Although microbial decomposition of plant litter plays a crucial role in nutrient cycling and soil fertility, we know less about likely links of specific microbial traits and decomposition, especially in relation to climate change. We study here wheat straw decomposition under ambient and manipulated conditions simulating a future climate scenario (next 80 years) in agroecosystems, including decay rates, macronutrient dynamics, enzyme activity, and microbial communities. We show that future climate will accelerate straw decay rates only during the early phase of the decomposition process. Additionally, the projected climate change will increase the relative abundance of saprotrophic fungi in decomposing wheat straw. Moreover, the impact of future climate on microbial community assembly and molecular ecological networks of both bacteria and fungi will strongly depend on the decomposition phase. During the early phase of straw decomposition, stochastic processes dominated microbial assembly under ambient climate conditions, whereas deterministic processes highly dominated bacterial and fungal communities under simulated future climate conditions. In the later decomposition phase, similar assembly processes shaped the microbial communities under both climate scenarios. Furthermore, over the early phases of decomposition, simulated future climate enhanced the complexity of microbial interaction networks. We concluded that the impact of future climate on straw decay rate and associated microbial traits like assembly processes and inter-community interactions is restricted to the early phase of decomposition., (© 2022. The Author(s).)

Biobased and biodegradable plastics have been intensively used in agriculture as mulching films. They provide a distinctive habitat for soil microbes, yet much less is known about the community assembly and interactions of plastisphere microbiota in soils under future climate change. For the first time, we explored the relative importance of ecological processes and the co-occurrence networks of plastic-associated microbes under ambient and future climates. The drift primarily dominated the community assembly of bacteria and fungi after 180D and 328D incubation in both climate regimes. The neutral community model prediction indicated that the migration rate of the plastisphere community in the later decay phase was lower than that in the early decay phase, contributing to the generation of the specific niches. Furthermore, future climate promoted the complexity and modularity of plastic-associated microbial networks: more competition and cooperation were observed in bacteria (or inter-kingdom) and fungi under future climate conditions, respectively. Overall, our findings strengthened the understanding of ecological processes and interplay of plastisphere microbiota during plastic biodegradation in soils under ambient and future climate regimes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

Even though it is widely acknowledged that litter decomposition can be impacted by climate change, the functional roles of microbes involved in the decomposition and their answer to climate change are less understood. This study used a field experimental facility settled in Central Germany to analyze the effects of ambient vs. future climate that is expected in 50-80 years on mass loss and physicochemical parameters of wheat litter in agricultural cropland at the early phase of litter decomposition process. Additionally, the effects of climate change were assessed on microbial richness, community compositions, interactions, and their functions (production of extracellular enzymes), as well as litter physicochemical factors shaping their colonization. The initial physicochemical properties of wheat litter did not change between both climate conditions; however, future climate significantly accelerated litter mass loss as compared with ambient one. Using MiSeq Illumina sequencing, we found that future climate significantly increased fungal richness and altered fungal communities over time, while bacterial communities were more resistant in wheat residues. Changes on fungal richness and/or community composition corresponded to different physicochemical factors of litter under ambient (Ca 2+ , and pH) and future (C/N, N, P, K + , Ca 2+ , pH, and moisture) climate conditions. Moreover, highly correlative interactions between richness of bacteria and fungi were detected under future climate. Furthermore, the co-occurrence networks patterns among dominant microorganisms inhabiting wheat residues were strongly distinct between future and ambient climates. Activities of microbial β-glucosidase and N-acetylglucosaminidase in wheat litter were increased over time. Such increased enzymatic activities were coupled with a significant positive correlation between microbial (both bacteria and fungi) richness and community compositions with these two enzymatic activities only under future climate. Overall, we provide evidence that future climate significantly impacted the early phase of wheat litter decomposition through direct effects on fungal communities and through indirect effects on microbial interactions as well as corresponding enzyme production., (© 2021. The Author(s).)

Microbial community members are the primary microbial colonizers and active decomposers of deadwood. This study placed sterilized standardized beech and spruce sapwood specimens on the forest ground of 8 beech- and 8 spruce-dominated forest sites. After 370 days, specimens were assessed for mass loss, nitrogen (N) content and 15 N isotopic signature, hydrolytic and lignin-modifying enzyme activities. Each specimen was incubated with bromodeoxyuridine (BrdU) to label metabolically active fungal and bacterial community members, which were assessed using amplicon sequencing. Fungal saprotrophs colonized the deadwood accompanied by a distinct bacterial community that was capable of cellulose degradation, aromatic depolymerization, and N 2 fixation. The latter were governed by the genus Sphingomonas , which was co-present with the majority of saprotrophic fungi regardless of whether beech or spruce specimens were decayed. Moreover, the richness of the diazotrophic Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium group was significantly correlated with mass loss, N content and 15 N isotopic signature. By contrast, presence of obligate predator Bdellovibrio spp. shifted bacterial community composition and were linked to decreased beech deadwood decay rates. Our study provides the first account of the composition and function of metabolically active wood-colonizing bacterial and fungal communities, highlighting cross-kingdom interactions during the early and intermediate stages of wood decay.

Decomposition by microorganisms of plastics in soils is almost unexplored despite the fact that the majority of plastics released into the environment end up in soils. Here, we investigate the decomposition process and microbiome of one of the most promising biobased and biodegradable plastics, poly(butylene succinate- co -adipate) (PBSA), under field soil conditions under both ambient and future predicted climates (for the time between 2070 and 2100). We show that the gravimetric and molar mass of PBSA is already largely reduced (28-33%) after 328 days under both climates. We provide novel information on the PBSA microbiome encompassing the three domains of life: Archaea, Bacteria, and Eukarya (fungi). We show that PBSA begins to decompose after the increase in relative abundances of aquatic fungi ( Tetracladium spp.) and nitrogen-fixing bacteria. The PBSA microbiome is distinct from that of surrounding soils, suggesting that PBSA serves as a new ecological habitat. We conclude that the microbial decomposition process of PBSA in soil is more complex than previously thought by involving interkingdom relationships, especially between bacteria and fungi.

Computational approaches that link bacterial 16S rRNA gene amplicon data to functional genes based on prokaryotic reference genomes have emerged. This study aims to validate or refute the applicability of the functional gene prediction tools for assessment and comparison of community functionality among experimental treatments, inducing either fast or slow responses in rhizosphere microbial community composition and function. Rhizosphere samples of wheat and barley were collected in two consecutive years at active and mature growth phases from organic and conventional farming plots with ambient or future-climate treatments of the Global Change Experimental Facility. Bacterial community composition was determined by 16S rRNA gene amplicon sequencing, and the activities of five extracellular enzymes involved in carbon (β-glucosidases, cellobiohydrolase, and xylosidase), nitrogen ( N -acetylglucosaminidase), and phosphorus (acid phosphatase) cycles were determined. Structural community data were used to predict functional patterns of the rhizosphere communities using Tax4Fun and PanFP. Subsequently, the predictions were compared with the measured activities. Despite the fact that different treatments mainly drove either community composition (plant growth phase) or measured enzyme activities (farming system), the predictions mirrored patterns in the treatments in a qualitative but not quantitative way. Most of the discrepancies between measured and predicted values resulted from plant growth stages (fast community response), followed by farming management and climate (slower community response). Thus, our results suggest the applicability of the prediction tools for comparative investigations of soil community functionality in less-dynamic environmental systems. IMPORTANCE Linking soil microbial community structure to its functionality, which is important for maintaining health and services of an ecosystem, is still challenging. Besides great advances in structural community analysis, functional equivalents, such as metagenomics and metatranscriptomics, are still time and cost intensive. Recent computational approaches (Tax4Fun and PanFP) aim to predict functions from structural community data based on reference genomes. Although the usability of these tools has been confirmed with metagenomic data, a comparison between predicted and measured functions is so far missing. Thus, this study comprises an expansive reality test on the performance of these tools under different environmental conditions, including relevant global change factors (land use and climate). The work provides a valuable validation of the applicability of the prediction tools for comparison of soil community functions across different sufficiently established soil ecosystems and suggest their usability to unravel the broad spectrum of functions provided by a given community structure.