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Agricultural ecosystems are facing increasing environmental changes. Revealing ecological stability of belowground organisms is key to developing management strategies that maintain agricultural ecosystem services in a changing world. Here, we collected soils from adjacent pairs of maize and rice fields along large spatial scale across Eastern and Southeast China to investigate the importance of core microbiota as a predictor of resistance of soil microbiome (e.g. bacteria, fungi and protist) to climate changes and nutrient fertilization, and their effect on multiple ecosystem functions, representing key services for crop growth and health in agro‐ecosystems. Soil microbiome in maize soils exhibited stronger resistance than that in rice soils, by considering multiple aspects of the resistance index, for example, community, phylogenetic conservation and network complexity. Community resistance of soil microbiome showed a geographic pattern, with higher resistance at lower latitudes, suggesting their stronger resistance in warmer regions. Particularly, we highlighted the role of core phylotypes in enhancing the community resistance of soil microbiome, which was essential for the maintenance of multifunctionality in agricultural ecosystems. Our results represent a significant advance in linking core phylotypes to community resistance and ecosystem functions, and therefore forecasting agro‐ecosystems dynamics in response to ongoing environmental changes. These suggest that core phylotypes should be considered a key factor in enhancing agricultural sustainability and crop productivity under global change scenarios. [ABSTRACT FROM AUTHOR]

Aim: Climate change is the foremost cause of terrestrial biodiversity decline, but the microbial communities from different habitats do not respond equally to environmental change. However, our understanding of the response patterns of microbial diversity to climate change remains limited in distinct agriculture ecosystems across large spatial scales. Here, we explore the response patterns of soil bacterial community structure and function to dry–wet cycles in dryland (maize) and paddy (rice) agricultural ecosystems throughout eastern China. Location: Eastern China. Time period: November 2019 to May 2020. Major taxa studied: Bacterial communities. Methods: Incubation experiments with dry–wet cycles were carried out on the soil samples collected from 25 paired maize and rice fields across eastern China. Bacterial community structure was estimated via high‐throughput sequencing techniques. We applied quantitative polymerase chain reaction to evaluate the effect of the dry–wet cycle on the change of functional genes. Phylogenetic signals were examined based on Blomberg's K to test the phylogenetic conservatism of maize and rice bacterial communities during dry–wet cycles. Results: Dry–wet cycles significantly decreased bacterial alpha diversity in both maize and rice soils, and bacterial communities from warmer regions were more sensitive to dry–wet cycles. The bacterial responses to dry–wet cycles were phylogenetically conserved, with greater phylogenetic conservation in the former. The abundance of functional genes that were related to carbon decomposition, nitrogen fixation, nitrification, denitrification and organophosphorus mineralization decreased during dry–wet cycles, and the resistances of such functional genes to disturbance were stronger in rice soils than in maize soils. In addition, the relative abundances of stable amplicon sequence variants during dry–wet cycles had a significant positive linear relationship with functional gene abundance in the maize and rice soils, indicating their essential roles in the stability of microbial function. Main conclusions: We conclude that soil bacterial community structure and function in dryland agricultural ecosystems are less stable and exhibit greater phylogenetic conservation in response to dry–wet cycles when compared with paddy fields. In addition, our study reveals, for the first time, the response patterns of bacterial communities to dry–wet cycles in dryland and wetland agroecosystems. [ABSTRACT FROM AUTHOR]

Summary: Soil biogeochemical processes are not only gauged by the dominant taxa in the microbiome but also depend on the critical functions of its 'rare biosphere' members. Here, we evaluated the biogeographical pattern of 'rare biosphere' propionate‐oxidizing syntrophs in 113 paddy soil samples collected across China. The relative abundance, activity and growth potential of propionate‐oxidizing syntrophs were analysed to provide a panoramic view of syntroph biogeographical distribution at the continental scale. The relative abundances of four syntroph genera, Syntrophobacter, Pelotomaculum, Smithella and Syntrophomonas were significantly greater at the warm low latitudes than at the cool high latitudes. Correspondingly, propionate degradation was faster in the low latitude soils compared with the high latitude soils. The low rate of propionate degradation in the high latitude soils resulted in a greater increase of the total syntroph relative abundance, probably due to their initial low relative abundances and the longer incubation time for propionate consumption. The mean annual temperature (MAT) is the most important factor shaping the biogeographical pattern of propionate‐oxidizing syntrophs, with the next factor being the soil's total sulfur content (TS). We suggest that the effect of MAT is related to the thermodynamic conditions, in which the endergonic constraint of propionate oxidation is leveraged with the increase of MAT. The TS effect is likely due to the ability of some propionate syntrophs to facultatively perform sulfate respiration. [ABSTRACT FROM AUTHOR]

Abstract Large variation of CH 4 emissions from paddy and wetland ecosystems exists across different geographical locations in China. To obtain mechanistic understanding of this variation, we investigated the dynamics of methanogenesis over the course of glucose degradation in fourteen paddy field soils and five wetland soils collected from different regions of China. The results revealed that the maximal rate (2–3 mM per day) and the total amount (25–30 mM) of CH 4 produced were similar across soil samples. The lag phase of methanogenesis, however, differed substantially with the shortest lag phase of 4 days in a paddy soil from north China and the longest of 32 days in a soil from south China, and this difference reflected a general geographical trend among all soils tested. Nitrate was reduced completely within 4 days in all soils. The reduction of Fe(III) and sulfate was completed after 21 days and 29 days, respectively. The depletion time of Fe(III) and sulfate were positively correlated with the lag phase of methanogenesis. Competition for common substrates between methanogens and iron and sulfate reducers, however, does not explain this coincidence because a slow production of CH 4 was detected at the very beginning. It appears that the geographical variations in methanogenesis and the reduction of ferric iron and sulfate are related to the variation in soil pH but not to temperature, soil organic C and nutrient conditions in paddy and wetland soils across eastern China. Graphical abstract Unlabelled Image Highlights • Lag phase for soil methanogenesis increases from north to south in China. • Depletion time of Fe(III) and sulfate positively correlated with methanogenesis lag phase. • Geographical variations in methanogenesis are related to the soil pH variation. • Greater temperature response for soil methanogenesis from south to north in China [ABSTRACT FROM AUTHOR]

Natural wetlands and anthropogenic paddy fields are the dominant biogenic sources of atmospheric methane emission which have been speculated as the most probable sources for the increase of post-2006 atmospheric methane. Regional differences in CH 4 emission is possibly due to microbial biogeographic distribution. Here we collected soils from 19 wetlands from different regions in China. The methane production capacity (MPC) was measured for each soil samples and varied from 1.11 to 841.94 mg/kg dry soil. High throughput sequencing was employed to investigate the diversity and composition of bacterial, archaeal and methanogenic communities. Similar biogeographic patterns for bacterial, archaeal and methanogenic communities along the latitudinal gradient were observed, and the biogeographic assemblies of different microbial groups were driven by concurrent factors, including edaphic variables (total organic carbon, total phosphorus and pH) and climatic variables (annual frost days, mean annual temperature, direct solar radiation and mean annual precipitation). MPC was significantly correlated with TOC concentration, and in addition, various functional taxa were positively correlated with MPC ( P < 0.05), for example, Sphingomonas , Syntrophomonas , Methanospirillum and Methanoregula , indicating their potential contributions in the methanogenic process, and many of them were fermentative bacteria and methanogens. Network analysis showed that some syntrophs, sulfate-reducers and methanogens were tightly co-occurred in one module, suggesting their involvements in cross-linked functional processes. Our study implicated both temperature and substrate availability altered the biogeographic patterns of microbial community as well as methane production potential in Chinese wetlands. [ABSTRACT FROM AUTHOR]

• A large-scale survey shows the distribution of micronutrients in paddy and maize soils across eastern China. • The available iron, copper and manganese are higher in paddy soils than those in maize soils. • The micronutrient availability in the paddy and maize soils is driven by organic matter content and soil pH. • The available iron is decoupled with environment and total metal in paddy fields. • Soil micronutrients need to be further improved in the northwest region in maize soils. Micronutrient deficiencies, known as 'hidden hunger', harm the growth and development of plants and people alike. However, less attention has been paid to soil micronutrients, the main source of micronutrients for plants and humans, than macronutrients (e.g. N and P availability). Understanding the geographic distribution of soil micronutrients across different agricultural fields is critical to support crop production and quality. Here we investigated the micronutrient composition (total and available copper, iron, manganese and zinc) of parallel 114 maize and rice fields in major crop production regions of eastern China. We found that available iron, copper and manganese were significantly higher in paddy soils than in maize soils, and total zinc was significantly higher in maize soils than in paddy soils. There was geospatial variation in the composition of micronutrients across latitudinal gradients and crop types. Soil organic matter and pH drove geographic variation of available micronutrient concentrations and ratio of total to available micronutrient, which were specific to micronutrient and crop type. Available Fe was decoupled with environment and total metal in paddy fields. Our study sheds light on the distribution patterns and environmental drivers of soil micronutrients in eastern China, and provides theoretical guidance for agricultural practice and fertilization management. [ABSTRACT FROM AUTHOR]

Protists are essential for nutrient cycling and plant performance in diverse ecosystems. However, the biogeographic patterns and driving forces (i.e. abiotic or biotic factors) of protistan communities remain poorly understood in agricultural ecosystems. Here, the biogeographic patterns of soil protists were assessed in adjacent pairs of maize and rice fields across eastern China. By combining our results with previously published datasets, we presented the first evidence that the α - and β -diversity of protists were highly structured by bacterial diversity in maize soils and fungal diversity in rice soils, respectively. Consistently, network analyses showed higher connectedness of protists to bacteria in maize soils, but higher connectedness of protists to fungi in rice soils. In addition, bacteria were more correlated with protistan consumers in maize soils, whereas fungi were more associated with protistan phototrophs. Protists in rice soils with lower diversity displayed broader environmental breadth and stronger phylogenetic conservatism than those in maize soils. Taken together, our results provides novel insights into the importance of biotic factors (trophic interrelationships) in driving the biogeographic patterns of soil protistan community in distinct agricultural ecosystems. • Biotic factors strongly affect the protistan biogeography in agricultural ecosystems. • Higher connectedness of protists to bacteria in maize soils. • Higher connectedness of protists to fungi in rice soils. • Protists displayed broader environmental breadthin rice soilsthan in maize soils. [ABSTRACT FROM AUTHOR]