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Aims Plants of similar life forms and closely related species have been observed to create similar types of plant-soil feedbacks (PsFs). However, investigations of the consistency of PsFs within species have not yielded clear results. For example, it has been reported that species create different types of PsFs in their native and introduced ranges. The aim of this project is to examine if four species create similar PsF types from soils collected from widely distributed areas within their introduced range. The soil for this project was collected from three areas in western North america. With this design, we aim to determine species-and site-specific ability to create PsFs and if the type of PsF created is consistent in all soil from all three collection areas. The species examined are Agropyron cristatum, Centaurea solstitialis, Poa pratensis and Taeniatherum caput-medusae. Methods We used three-field collected soils (from northern Nevada, western montana and eastern montana) in a two-phase greenhouse experiment to quantify the type of PsFs created by four invasive species. The first phase was a conditioning phase wherein each invasive species created species-specific changes to the soil. The second phase of the experiment was the response phase wherein both the conditioning species and a native phytometer were grown in the conditioned soil and in unconditioned (control) soil. The final aboveground biomass was used to evaluate the effect of conditioning and to determine the type of PsF created by each invasive species. Important Findings our results suggest that three of our four study species did show consistency in relation to PsF. Two species A. cristatum and T. caputmedusae consistently created PsF types that benefit conspecifics more than heterospecifics (and thus are 'invasive' PsF types) and P. pratensis consistently exhibited no, or 'neutral', feedbacks. The fourth species (C. solstitialis) was inconsistent: in one soil, no feedback was created; in other soil, an invasive PsF was created and in the last soil, a feedback that relatively benefited the native phytometer was created. Thus, PsFs appear to uniformly contribute to the success of two species (A. cristatum and T. caput-medusae) but not C. solstitialis nor P. pratensis.

Midmorning N2O flux estimates were not consistent with near‐continual data for spring and fall applied urea. Local N2O sampling protocols must account for temporal changes in management and climatic conditions. Non‐alignment in soil temperature and N2O patterns in annual‐crop soils is consistent with Fick's Law. Non‐alignment between temperatuer and N2O emissions can occur when the soil is saturated with water. Near‐continuous automated data collection at anticipated max and min emissions may improve the accuracy of N2O estimates. A common approach for measuring N2O emissions is to collect midmorning or early evening gas samples from experiments utilizing the chamber‐based flux methodology. However, due to high spatial and temporal variability, N2O estimates based on midmorning or early evening sampling may not provide accurate estimates of total emissions. This study determined the impact of sampling collection timing on the precision and accuracy of N2O emissions estimates. Nitrous oxide emissions, air and soil temperatures, and soil moisture were measured for 21 d following the application of 224 kg urea‐N ha–1 on 20 Sept. 2017, 11 Oct. 2017, and 1 May 2018, at six time intervals (0130–0230, 0530–0630, 0930–1030, 1330–1430, 1730–1830, and 2130–2230 h) over a 24‐h period. Based on multiple daily measurements, point samples collected between 0930 and 1030 h (midmorning) were inconsistent in their ability to predict N2O emissions. However, samples collected between 2130 and 2230 h (early evening) were similar to average emissions. The number of randomly collected point samples to be within 20% of the mean 80% of the time over a 21‐d period ranged from 13 samples for fertilizer applied on 20 Sept. 2017 to 48 samples for fertilizer applied on 11 Oct. 2017. This research indicates that management and climatic variability affect N2O emissions, and that accurate sampling protocols vary across management and climates. To reduce uncertainty, N2O sampling protocol should be tested under conditions likely to occur and where possible, near‐continuous measurement systems should be adopted.

Seedling performance is often a limiting factor in ecological restoration. Changes in the soil microbial community generated by invasive plants contribute to seedling failure. A method to remediate invasive species‐induced changes to the soil microbial community that results in increased native species seedling performance and decreased invasive species seedling performance could have a large impact on the success of many restoration efforts. In a greenhouse experiment, we first examined the changes in the soil microbial community created by invasive compared to native grasses. Then, we investigated four microbial treatments (bacterial inoculant, fungal inoculant, fungicide, and bactericide/fungicide) to remediate microbial plant–soil feedbacks (PSFs) created by invasive species Bromus inermis and Poa pratensis and increase the performance of natives Andropogon gerardii, Elymus canadensis, Pascopyrum smithii, and Schizachyrium scoparium. We found that the PSF mitigation treatments had some context‐dependent utility for restoration. For example, all of the treatments decreased the performance of B. inermis and fungal inoculant decreased the performance of P. pratensis. However, no single treatment increased the performance of all natives. Fungicide increased the performance of A. gerardii and E. canadensis in soil previously occupied by B. inermis and the performance of S. scoparium in soil previously occupied by P. pratensis. If validated in the field, PSF mitigation treatments may have utility for restoration practitioners.

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