Microorganisms are vital in mediating the earth’s biogeochemical cycles; yet, despite our rapidly increasing ability to explore complex environmental microbial communities, the relationship between microbial community structure and ecosystem processes remains poorly understood. Here, we address a fundamental and unanswered question in microbial ecology: ‘When do we need to understand microbial community structure to accurately predict function?’ We present a statistical analysis investigating the value of environmental data and microbial community structure independently and in combination for explaining rates of carbon and nitrogen cycling processes within 82 global datasets. Environmental variables were the strongest predictors of process rates but left 44% of variation unexplained on average, suggesting the potential for microbial data to increase model accuracy. Although only 29% of our datasets were significantly improved by adding information on microbial community structure, we observed improvement in models of processes mediated by narrow phylogenetic guilds via functional gene data, and conversely, improvement in models of facultative microbial processes via community diversity metrics. Our results also suggest that microbial diversity can strengthen predictions of respiration rates beyond microbial biomass parameters, as 53% of models were improved by incorporating both sets of predictors compared to 35% by microbial biomass alone. Our analysis represents the first comprehensive analysis of research examining links between microbial community structure and ecosystem function. Taken together, our results indicate that a greater understanding of microbial communities informed by ecological principles may enhance our ability to predict ecosystem process rates relative to assessments based on environmental variables and microbial physiology.

Soil salinity is a global issue threatening land productivity, and estimates predict that 50% of all arable land will become impacted by salinity by 2050. Consequently, it is important to have a fundamental understanding of crop response to salinity to minimize economic loss and improve food security. While an immense amount of research has been performed assessing corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] response to salinity, there are few, if any, comprehensive reviews compiling previously published literature. This review provides a detailed description of our current knowledge on the impacts of salinity on corn and soybean growth and development. Both osmotic stress and specific ion toxicities with respect to corn and soybean are addressed. Additionally, potential areas of future research are recommended.Core Ideas Review of salinity's effects on corn and soybean growth and development. Impacts of osmotic stress and specific ion toxicities discussed. Potential areas of future research addressed.

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Core Ideas Effectiveness of EEFs varied greatly with their modes of action, soils, and management factors. NIs, DIs, and CRFs reduced N2O emissions by 38, 30, and 19%, respectively, compared with conventional N fertilizers. NIs increased overall crop yields by 7% compared with conventional N fertilizers. DIs might provide added benefits over NIs in alkaline soils, coarse‐textured soils, and irrigated systems. Enhanced efficiency fertilizers (EEFs) have the potential to reduce N2O emissions and improve crop productivity, but the impact of soil and management conditions on their effectiveness is not clear. We conducted a meta‐analysis to evaluate the effectiveness of different EEF types in reducing N2O emissions in three cereal production systems: rice (Oryza sativa L.), corn (Zea mays L.), and wheat (Triticum aestivum L.). We also compared EEF efficacy across soil and management conditions for corn and wheat systems. Results showed that the effect of EEFs on N2O emissions and crop yields varied greatly with their modes of action, soil types, and management conditions. Nitrification inhibitors (NIs), double inhibitors (DIs: urease plus nitrification inhibitors), and controlled‐release N fertilizers (CRFs) consistently reduced N2O emissions compared with conventional N fertilizers across soil and management conditions (grand mean decreases of 38, 30, and 19%, respectively). The DIs more effectively reduced N2O emissions in alkaline soils than did NIs, but the trend was reversed in acidic soils. Urease inhibitors also reduced N2O emissions compared with conventional N fertilizers in coarse‐textured soils and irrigated systems. Overall crop yields increased by 7% with the addition of NIs alone. Compared with conventional N fertilizers, DIs also increased crop yields in alkaline soils, coarse‐textured soils, and irrigated systems. However, CRFs had no effect on crop yields. Overall, this study suggests that NIs or DIs can reduce N2O emissions while improving crop yields. Growers should select EEFs based on their soil and management conditions to maximize their effectiveness.

To link to this Article: DOI: 10.1080/0735268090277655