Successful re-introduction of native species through ecological restoration requires understanding the complex process of seed germination. Soil microbes play an important role in promoting native establishment, and are often added to restoration sites during seed sowing. We tested the role of soil and lab-grown bacterial inoculants on germination timing and percent germination for nineteen species of plants commonly found in coastal California. Each species exhibited a different response to inoculant treatments, but overall time-to-germination was longer and percent germination was lower with soil inoculant compared to control or other treatments.The invasive species in our study had the highest percent germination of all species and germinated faster than all native shrubs. Germination timing was negatively correlated with percent germination and with seed weight. Our results suggest that lab grown inoculant and chemical treatment are effective at increasing germination in some native species, while soil inoculant is not. Given differences in germination timing between native and invasive species, restoration practitioners could consider using herbicide to treat areas seeded with native shrubs immediately following germination of invasive species without harming most natives, although germination timing and herbicides need further study in relation to microbial effects on seed germination.
Practitioners are challenged with choosing among many potentially effective methods for sowing seed in ecological restoration projects to achieve sufficient native plant establishment. We tested the effectiveness of seed sowing techniques on moderate and steep slopes in a Mediterranean climate by measuring native seedling density immediately following germination, as well as plant density, recruitment success, and soil movement through the second growing season. We calculated cost effectiveness of different methods as the native plant density per dollar spent sowing seed. While all sowing techniques resulted in significant native establishment compared with unseeded controls, hydro seeding on moderate slopes was the most cost effective (native seedlings established per dollar spent). Although all steep‐sloped seeding techniques resulted in high densities of native species, all methods also resulted in significant soil loss. Shrubs preferred hand seeding followed by jute netting on steep slopes, while forbs reached greatest densities with hydro seeding on moderate slopes. Seedlings of species with heavy seeds were present in greater densities than species with lighter seeds in imprint sowing treatments. The “best” seed sowing technique varied depending on slope and metric of success (native density, species richness, shrub density, or forb density). Different combinations of slope, technique, and success metric resulted in significantly different project costs, which implies opportunities for savings given careful decision‐making relative to mitigation needs on heterogeneous landscapes. Evaluations of techniques for restoring slopes are limited, yet critical for expanding the area capable of being restored and the application of limited conservation funding.
<p>Isotope ratios of soil water and atmospheric water vapor have been used to estimate soil evaporation fluxes and to partition evapotranspiration at local (plot, stand) scales, but the application of these methods has been limited by 1) challenges associated with data acquisition, and 2) the complexity of and lack of consensus about appropriate data interpretation methods. New initiatives that have expanded access to data, such as the U.S. National Ecological Observatory Network (NEON), are beginning to address the first of these limitations. In order to make progress toward the second, we link a model of soil water and water isotope balance, based on the widely used Noah land surface model, to a range of core NEON measurements and ancillary field-collected data using a Bayesian hierarchical framework. This model framework allows self-consistent treatment of the water and isotope cycles, including representation of uncertainties and differing assumptions, and simultaneous optimization of all model parameters conditioned on all data using Markov-Chain Monte Carlo sampling. We test the framework by applying it to estimate evapotranspiration partitioning at a dryland NEON site in central Utah and show that the posterior estimates give reasonable and useful constraints on flux rates and provide constraints on model parameters that could inform our understanding of soil properties and isotopic systematics in the system. This flexible framework for interpretation of water isotope data in evapotranspiration studies is amenable to application across ecosystems and at sites with different levels of data availability in support of cross-site syntheses and validation/testing of earth system models.</p>
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