Bacterial abundance is a fundamental metric for understanding the population dynamics of soil bacteria and their role in biogeochemical cycles. Despite its importance, methodological constraints hamper our ability to assess bacterial abundance in terrestrial environments. Here, we aimed to optimize the use of flow cytometry (FCM) to assay bacterial abundances in soil while providing a rigorous quantification of its limitations. Soil samples were spiked with Escherichia coli to evaluate the levels of recovery efficiency among three extraction approaches. The optimized method added a surfactant (a tetrasodium pyrophosphate [TSP] buffer) to 0.1 g of soil, applied an intermediate degree of agitation through shaking, and used a Nycodenz density gradient to separate the cells from background debris. This procedure resulted in a high (average, 89%) level of cell recovery. Recovery efficiencies did not differ significantly among sites across an elevation gradient but were positively correlated with percent carbon in the soil samples. Estimated abundances were also highly repeatable between technical replicates. The method was applied to samples from two field studies and, in both cases, was sensitive enough to detect treatment and site differences in bacterial abundances. We conclude that FCM offers a fast and sensitive method to assay soil bacterial abundance from relatively small amounts of soil. Further work is needed to assay differential biases of the method across a wider range of soil types. IMPORTANCE The ability to quantify bacterial abundance is important for understanding the contributions of microbial communities in soils, but such assays remain difficult and time-consuming. Flow cytometry offers a fast and direct way to count bacterial cells, but several concerns remain in applying the technique to soils. This study aimed to improve the efficiency of the method for soil while quantifying its limitations. We demonstrated that an optimized procedure was sensitive enough to capture differences in bacterial abundances among treatments and ecosystems in two field studies.

Many degraded ecosystems need active restoration to conserve biodiversity and re‐establish ecosystem function, both highlighted targets of the UN Decade on Ecosystem Restoration and the proposed EU Nature restoration law. Soil translocation, where both plant propagules and their associated soil biota are co‐introduced, has increasingly been proposed as a powerful restoration technique for terrestrial ecosystems. However, a synthesis of the effectiveness of this method across ecosystems is lacking. To address how soil translocation affects restoration success, we performed a meta‐analysis synthesizing data from 46 field experiments and their respective reference ecosystems in 17 countries across four continents. In each experiment, vegetation composition was recorded in response to soil translocation treatments and the resultant vegetational changes (diversity and composition) were quantified. We found that soil translocation leads to plant community development further away from the control and more towards the reference plant communities compared with treatments where only plant propagules were introduced. However, the variability of effect sizes among experiments was large, suggesting strong dependence of restoration success on restoration context. We found that restoration success was more likely on loamy soils and when translocation treatments were implemented over larger spatial areas (>180 m2). Furthermore, we found that restoration success either consistently increased or decreased over time depending on the experiment. Not only is this congruent with positive feedbacks between plant and soil communities driving plant community development, but it also suggests that the composition of the translocated plant and soil communities, and initial starting conditions, are critical for long‐term restoration success. Synthesis and applications. Our analysis highlights soil translocation can be a successful restoration method across a broad range of ecosystems. However, its implementation needs to depend on a thorough evaluation of local conditions and the potential added value. Further refinement of soil translocation techniques is needed to increase success rates.

Although aboveground metrics remain the standard, restoring functional ecosystems should promote both aboveground and belowground biotic communities. Restoration using salvaged soil—removal and translocation of topsoil from areas planned for development, with subsequent deposition at degraded sites—is an alternative to traditional methods. Salvaged soil contains both seed and spore banks, which may holistically augment restoration. Salvaged soil methods may reduce non-native germination by burying non-native seeds, increase native diversity by adding native seeds, or transfer soil microbiomes, including arbuscular mycorrhizal fungi (AMF), to recipient sites. We transferred soil to three degraded recipient sites and monitored soil microbes, using flow cytometry and molecular analyses, and characterized the plant community composition. Our findings suggest that salvaged soil at depths ≥5 cm reduced non-native grass cover and increased native plant density and species richness. Bacterial abundance at recipient sites were statistically equivalent to donor sites in abundance. Overall, topsoil additions affected AMF alpha diversity and community composition and increased rhizophilic AMF richness. Because salvaged soil restoration combines multiple soil components, including native plant and microbial propagules, it may promote both aboveground and belowground qualities of the donor site, when applying this method for restoring invaded and degraded ecosystems.

Restoring biodiversity to degraded sites in the wildland–urban interface is challenging due to many factors, including competition with non‐native species and increased herbivore pressure. In a unique collaboration between land managers, environmental educators, students, and academic ecologists, we tested the effectiveness of multiple restoration techniques in an adaptive management framework, modifying methods each year based on results in the previous years. We evaluated the impact of non‐native species and rabbit herbivores on soil moisture and native plant growth. We added native seedlings to our site either immediately adjacent to existing native shrubs (potential nurse plants) or in the open. One native species, Artemisia californica, was significantly negatively influenced by the presence of an existing shrub and grew more in the open in both a wet and a dry year. Another native species, Eriogonum fasciculatum, experienced high mortality by rabbit herbivores when it was not protected by fencing. Fencing also increased abundance of non‐native plants, so a combination of fencing and non‐native removal without a nurse plant was optimal for restoration. Soil moisture was greater in the open than under existing native shrubs, indicating that existing shrubs decreased soil water available to seedlings. Data collected by trained students was indistinguishable from that collected by professional ecologists. Our use of community‐engaged science demonstrates how scientific adaptive management experiments can include a diversity of participants and allow for immediate dissemination and implementation of results.

Ecological restoration frequently involves the addition of native plants, but the effectiveness (in terms of plant growth, plant survival, and cost) of using seeds versus container plants has not been studied in many plant communities. It is also not known if plant success would vary by species or based on functional traits. To answer these questions, we added several shrub species to a coastal sage scrub restoration site as seeds or as seedlings in a randomized block design. We measured percent cover, density, species richness, size, survival, and costs. Over the two years of the study, shrubs added to the site as seeds grew more and continued to have greater density than plants added from containers. Seeded plots also had greater native species richness than planted plots. However, shrubs from containers had higher survival rates, and percent cover was comparable between the planted and seeded treatments. Responses varied by species depending on functional traits, with deep-rooted evergreen species establishing better from container plants. Our cost analysis showed that it is more expensive to use container plants than seed, with most of the costs attributed to labor and supplies needed to grow plants. Our measurements of shrub density, survival, species richness, and growth in two years in our experimental plots lead us to conclude that coastal sage scrub restoration with seeds is optimal for increasing density and species richness with limited funds, yet the addition of some species from container plants may be necessary if key species are desired as part of the project objectives.