查看更多>>摘要：Microbial carbon use efficiency (CUE) is a key parameter for soil organic carbon (SOC) cycling. However, there is still lack of evidence for linkages between shifts in SOC stocks and altered microbial CUE under fertilization. Here, we conducted a meta-analysis to explore the effects of fertilization on microbial CUE and its relationships with SOC sequestration. We found that inorganic and combined inorganic-organic fertilization increased microbial CUE by 6.8% and 9.7%, respectively. These two types of fertilizer also increased SOC contents by 4.1% and 51.7%, respectively. Inorganic and combined inorganic-organic fertilization-induced increase in SOC content was positively associated with increased microbial CUE. Our result provided overwhelming evidence that the increase of microbial CUE induced by inorganic and combined inorganic-organic fertilization exerts important effect on SOC sequestration.
查看更多>>摘要：Belowground insect herbivory is an important interaction that can shape ecological communities above- and belowground. A key component of belowground ecosystems are the arbuscular mycorrhizal (AM) fungi that associate with roots of most terrestrial plants. Despite the shared ecological significance of root herbivores and AM fungi, there is an absence of data on how insect root herbivory affects root-colonising AM fungal diversity. This study explored the impacts of root herbivory (from Dermolepida alborhirtum) on the diversity and community composition of AM fungi colonising plant roots (Dichanthium sericeum) and assessed the effects on plant growth and nutrient uptake. Belowground herbivory significantly altered AM fungal community structure and reduced species richness, potentially removing fungal taxa sensitive to root-herbivore disturbance. Meanwhile, herbivory also reduced root biomass and aboveground phosphorus. These findings demonstrate how belowground herbivores can directly shape AM fungal communities in plant roots.
查看更多>>摘要：Revealing regional distribution and diversity of abundant and rare bacterial communities in different cropping systems are crucial to predict trends of microbial changes in farmlands and understand ecosystem functions. Here, we examined the spatial distribution patterns and calculated differences in diversity and function for abundant and rare bacterial sub-communities across 114 typical dryland farmland (corn, soybean and alfalfa) soils in crop monoculture (CM) and rotation (CR) systems in northeastern China. Significant (P < 0.001) distance-decay relationships were detected for the abundant and rare sub-communities in both CM and CR systems. In addition, edaphic variables (CMabundant = 27.3%, CMrare = 9.1%; CRabundant = 33.3%, CRrare = 15.3%) largely contributed to the variation of sub-communities based on variance partitioning analysis (VPA). Shannon and Chao1 indices were significantly (P < 0.05) different between abundant and rare sub-communities in CM and CR systems. Both abundant (RANOSIM = 0.065, P = 0.004) and rare (RANOSIM = 0.054, P = 0.013) bacterial community were significantly (P < 0.05) separated according to CM and CR systems. Based on Tax4Fun, for Proteobacteria, environmental information processing was the main potential function in CM, while metabolism was the one in CR system. Additionally, the potential functions of rare taxa were greater than that of abundant taxa both in CM and CR systems. Our results would not only provide theoretical support for better understanding the roles of rare and abundant bacteria, but also offered new opportunity to improve agricultural ecosystem functions.
查看更多>>摘要：Root decomposition keeps occurring widely in soils, particularly after plant harvest and death, and drives critical microbial ecological functions. However, its role in the destiny of soil organic pollutants and underlying mechanisms remain unclear. In this study, DNA stable isotope probing (DNA-SIP) was combined with metabolomics to investigate the mechanisms of soil polychlorinated biphenyls (PCBs) degradation in the root decomposition process by identifying the active PCBs degraders in situ and corresponding metabolites. The 2,5dichlorobiphenyl (PCB-9) degradation was improved by 7.4% in the root decomposition treatment relative to the rhizosphere treatment, and the degradation was faster in both treatments than the control after 6-week cultivation. Both root decomposition and rhizosphere treatments altered soil microbial community, changing the active PCB-9 degraders to different extents. The root decomposition treatment had the highest "average phylogenetic distance index" (ADI) value, indicating a competition reduction effect of root decomposition on microbial survival, and the lowest corrected average phylogenetic distance index (ADIC) value, suggesting a preference toward aerobic PCBs degraders during root decomposition. Metabolites associated with the root decomposition process critically affected both the whole microbial community and active PCB-9 degraders. Compounds related to carbohydrate and lipid metabolisms were enriched during the root decomposition process and might be important to the active PCB-9-degrading community assembly. Our results confirmed that root decomposition improved the biodegradation of organic pollutants in soil and reminded us of its importance in soil quality.
查看更多>>摘要：Root exudates determine plant's ability to acquire nutrients through influencing plant's interactions with soil microorganisms. Recent studies suggest that plant's associations with beneficial soil microorganisms explain variation in root exudation as plants opt to minimize the exudation cost through such symbiosis. Yet, we have a poor understanding of whether plants change their exudation rates through mycorrhizal symbiosis in soil en-vironments with varying resource availability. Here, we report the effects of plant-mycorrhizal symbiosis on root exudation rates across a gradient of soil phosphorous (P) availability from a field experiment in subtropical forests. Root exudation rates were higher in plants partnering with arbuscular mycorrhizal fungi than those with ectomycorrhizal fungi, but this difference disappeared in soils with high P. Specific root surface area, specific root length and fine root vitality explained high root exudation in P-limited soils. These findings demonstrate that mycorrhizal symbiosis and root functional traits collectively determine the variation in root exudation in P-limited environments.
Holguin, JenniferCollins, Scott L.McLaren, Jennie R.
12页
查看更多>>摘要：Predicted climate change extremes, such as severe or prolonged drought, may considerably impact carbon (C) and nitrogen (N) cycling in water-limited ecosystems. However, we lack a clear and mechanistic understanding of how extreme climate change events impact ecosystem processes belowground. This study investigates the effects of five years of reoccurring extreme growing season drought (66% reduction, extreme drought treatment) and two-month delay in monsoon precipitation (delayed monsoon treatment) on belowground productivity and biogeochemistry in two geographically adjacent semi-arid grasslands: Chihuahuan Desert grassland dominated by Bouteloua eriopoda and Great Plains grassland dominated by B. gracilis. After five years, extreme drought reduced belowground net primary productivity (BNPP) in the Chihuahuan Desert grassland but not in the Great Plains grassland. Across both grasslands, extreme drought increased soil pH and available soil nutrients nitrate and phosphate. The delayed monsoon treatment reduced BNPP in both grasslands. However, while available soil nitrate decreased in the Chihuahuan Desert grassland, the delayed monsoon treatment overall had little effect on soil ecosystem properties. Extreme drought and delayed monsoon treatments did not significantly impact soil microbial biomass, exoenzyme potentials, or soil C stocks relative to ambient conditions. Our study demonstrates that soil microbial biomass and exoenzyme activity in semi-arid grasslands are resistant to five years of extreme and prolonged growing season drought despite changes to soil moisture, belowground productivity, soil pH, and nutrient availability.
NSTL
Elsevier