Project description:To study long-term elevated CO2 and enriched N deposition interactive effects on microbial community and soil ecoprocess, here we investigated soil microbial community in a grassland ecosystem subjected to ambient CO2 (aCO2, 368 ppm), elevated CO2 (eCO2, 560 ppm), ambient nitrogen deposition (aN) or elevated nitrogen deposition (eN) treatments for a decade. There exist antagonistic CO2×N interactions on microbial functional genes associated with C, N, P S cycling processes. More strong antagonistic CO2×N interactions are observed on C degradation genes than other genes. Remarkably antagonistic CO2×N interactions on soil microbial communities could enhance soil C accumulation.
Project description:Fire disturbances are becoming more common, more intense, and further-reaching across the globe, with consequences for ecosystem functioning. Importantly, fire can have strong effects on the soil microbiome, including community and functional changes after fire, but surprisingly little is known regarding the role of soil fire legacy in shaping responses to recent fire. To address this gap, we conducted a manipulative field experiment administering fire across 32 soils with varying fire legacies, including combinations of 1-7 historic fires and 1-33 years since most recent fire. We analyzed soil metatranscriptomes, determining for the first time how fire and fire legacy interactively affect metabolically-active soil taxa, the microbial regulation of important carbon (C), nitrogen (N) and phosphorus (P) cycling, expression of carbohydrate-cycling enzyme pathways, and functional gene co-expression networks. Experimental fire strongly downregulated fungal activity while upregulating many bacterial and archaeal phyla. Further, fire decreased soil capacity for microbial C and N cycling and P transport, and drastically rewired functional gene co-expression. Perhaps most importantly, we highlight a novel role of soil fire legacy in regulation of microbial C, N, and P responses to recent fire. We observed a greater number of functional genes responsive to the interactive effects of fire and fire legacy than those affected solely by recent fire, indicating that many functional genes respond to fire only under certain fire legacy contexts. Therefore, without incorporating fire legacy of soils, studies will miss important ways that fire shapes microbial roles in ecosystem functioning. Finally, we showed that fire caused significant downregulation of carbon metabolism and nutrient cycling genes in microbiomes under abnormal soil fire histories, producing a novel warning for the future: human manipulation of fire legacies, either indirectly through global change-induced fire intensification or directly through fire suppression, can negatively impact soil microbiome functional responses to new fires.
Project description:Anthropogenic nitrogen (N) deposition may affect soil organic carbon (SOC) decomposition, thus affecting the global terrestrial carbon (C) cycle. However, it remains unclear how the level of N deposition affects SOC decomposition by regulating microbial community composition and function, especially C-cycling functional genes structure. We investigated the effects of short-term N addition on soil microbial C-cycling functional gene composition, SOC-degrading enzyme activities, and CO2 emission in a 5-year field experiment established in an artificial Pinus tabulaeformis forest on the Loess Plateau, China.
Project description:Soil transplant serves as a proxy to simulate climate change in realistic climate regimes. Here, we assessed the effects of climate warming and cooling on soil microbial communities, which are key drivers in Earth’s biogeochemical cycles, four years after soil transplant over large transects from northern (N site) to central (NC site) and southern China (NS site) and vice versa. Four years after soil transplant, soil nitrogen components, microbial biomass, community phylogenetic and functional structures were altered. Microbial functional diversity, measured by a metagenomic tool named GeoChip, and phylogenetic diversity are increased with temperature, while microbial biomass were similar or decreased. Nevertheless, the effects of climate change was overridden by maize cropping, underscoring the need to disentangle them in research. Mantel tests and canonical correspondence analysis (CCA) demonstrated that vegetation, climatic factors (e.g., temperature and precipitation), soil nitrogen components and CO2 efflux were significantly correlated to the microbial community composition. Further investigation unveiled strong correlations between carbon cycling genes and CO2 efflux in bare soil but not cropped soil, and between nitrogen cycling genes and nitrification, which provides mechanistic understanding of these microbe-mediated processes and empowers an interesting possibility of incorporating bacterial gene abundance in greenhouse gas emission modeling.
Project description:Reforestation is effective in restoring ecosystem functions and enhancing ecosystem services of degraded land. The three most commonly employed reforestation methods of natural reforestation, artificial reforestation with native Masson pine (Pinus massoniana Lamb.), and introduced slash pine (Pinus elliottii Engelm.) plantations were equally successful in biomass yield in southern China. However, it is not known if soil ecosystem functions, such as nitrogen (N) cycling, are also successfully restored. Here, we employed a functional microarray to illustrate soil N cycling. The composition and interactions of N-cycling genes in soils varied significantly with reforestation method. Natural reforestation had more superior organization of N-cycling genes, and higher functional potential (abundance of ammonification, denitrification, assimilatory, and dissimilatory nitrate reduction to ammonium genes) in soils, providing molecular insight into the effects of reforestation.
Project description:Aeolian soil erosion, exacerbated by anthropogenic perturbations, has become one of the most alarming processes of land degradation and desertification. By contrast, dust deposition might confer a potential fertilization effect. To examine how they affect topsoil microbial community, we conducted a study GeoChip techniques in a semiarid grassland of Inner Mongolia, China. We found that microbial communities were significantly (P<0.039) altered and most of microbial functional genes associated with carbon, nitrogen, phosphorus and potassium cycling were decreased or remained unaltered in relative abundance by both erosion and deposition, which might be attributed to acceleration of organic matter mineralization by the breakdown of aggregates during dust transport and deposition. As a result, there were strong correlations between microbial carbon and nitrogen cycling genes. amyA genes encoding alpha-amylases were significantly (P=0.01) increased by soil deposition, reflecting changes of carbon profiles. Consistently, plant abundance, total nitrogen and total organic carbon were correlated with functional gene composition, revealing the importance of environmental nutrients to soil microbial function potentials. Collectively, our results identified microbial indicator species and functional genes of aeolian soil transfer, and demonstrated that functional genes had higher susceptibility to environmental nutrients than taxonomy. Given the ecological importance of aeolian soil transfer, knowledge gained here are crucial for assessing microbe-mediated nutrient cyclings and human health hazard.
Project description:Soil transplant serves as a proxy to simulate climate change in realistic climate regimes. Here, we assessed the effects of climate warming and cooling on soil microbial communities, which are key drivers in EarthM-bM-^@M-^Ys biogeochemical cycles, four years after soil transplant over large transects from northern (N site) to central (NC site) and southern China (NS site) and vice versa. Four years after soil transplant, soil nitrogen components, microbial biomass, community phylogenetic and functional structures were altered. Microbial functional diversity, measured by a metagenomic tool named GeoChip, and phylogenetic diversity are increased with temperature, while microbial biomass were similar or decreased. Nevertheless, the effects of climate change was overridden by maize cropping, underscoring the need to disentangle them in research. Mantel tests and canonical correspondence analysis (CCA) demonstrated that vegetation, climatic factors (e.g., temperature and precipitation), soil nitrogen components and CO2 efflux were significantly correlated to the microbial community composition. Further investigation unveiled strong correlations between carbon cycling genes and CO2 efflux in bare soil but not cropped soil, and between nitrogen cycling genes and nitrification, which provides mechanistic understanding of these microbe-mediated processes and empowers an interesting possibility of incorporating bacterial gene abundance in greenhouse gas emission modeling. Fifty four samples were collected from three soil types (Phaeozem,Cambisol,Acrisol) in three sites (Hailun, Fengqiu and Yingtan) along a latitude with reciprocal transplant; Both with and without maize cropping in each site; Three replicates in every treatments.
Project description:Aeolian soil erosion, exacerbated by anthropogenic perturbations, has become one of the most alarming processes of land degradation and desertification. By contrast, dust deposition might confer a potential fertilization effect. To examine how they affect topsoil microbial community, we conducted a study GeoChip techniques in a semiarid grassland of Inner Mongolia, China. We found that microbial communities were significantly (P<0.039) altered and most of microbial functional genes associated with carbon, nitrogen, phosphorus and potassium cycling were decreased or remained unaltered in relative abundance by both erosion and deposition, which might be attributed to acceleration of organic matter mineralization by the breakdown of aggregates during dust transport and deposition. As a result, there were strong correlations between microbial carbon and nitrogen cycling genes. amyA genes encoding alpha-amylases were significantly (P=0.01) increased by soil deposition, reflecting changes of carbon profiles. Consistently, plant abundance, total nitrogen and total organic carbon were correlated with functional gene composition, revealing the importance of environmental nutrients to soil microbial function potentials. Collectively, our results identified microbial indicator species and functional genes of aeolian soil transfer, and demonstrated that functional genes had higher susceptibility to environmental nutrients than taxonomy. Given the ecological importance of aeolian soil transfer, knowledge gained here are crucial for assessing microbe-mediated nutrient cyclings and human health hazard. The experimental sites comprised of three treatments of control, soil erosion and deposition, with 5 replicates of each treatment.
Project description:Clipping (i.e., harvesting aboveground plant biomass) is common in agriculture and for bioenergy production. However, microbial responses to clipping in the context of climate warming are poorly understood. We investigated the interactive effects of grassland warming and clipping on soil properties, plant and microbial communities, in particular microbial functional genes. Clipping alone did not change the plant biomass production, but warming and clipping combined increased the C4 peak biomass by 47% and belowground net primary production by 110%. Clipping alone and in combination with warming decreased the soil carbon input from litter by 81% and 75%, respectively. With less carbon input, the abundances of genes involved in degrading relatively recalcitrant carbon increased by 38-137% in response to either clipping or the combined treatment, which could weaken the long-term soil carbon stability and trigger a positive feedback to warming. Clipping alone also increased the abundance of genes for nitrogen fixation, mineralization and denitrification by 32-39%. The potentially stimulated nitrogen fixation could help compensate for the 20% decline in soil ammonium caused by clipping alone, and contribute to unchanged plant biomass. Moreover, clipping tended to interact antagonistically with warming, especially on nitrogen cycling genes, demonstrating that single factor studies cannot predict multifactorial changes. These results revealed that clipping alone or in combination with warming altered soil and plant properties, as well as the abundance and structure of soil microbial functional genes. The aboveground biomass removal for biofuel production needs to be re-considered as the long-term soil carbon stability may be weakened.