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Seed‐based restoration is one of the most difficult challenges for dryland restoration. Identifying environmental conditions that drive variation in seed and seedling mortality across similar restoration efforts could increase understanding of when and where restoration outcomes are likely to be favourable and identify new tools and strategies to improve outcomes.We asked how variation in a suite of environmental predictors influenced germination, emergence, seedling establishment and juvenile survival of four commonly sown perennial grass species across 33 seeding experiments distributed over an ~160,000‐km2 area of the Great Basin, a cold desert system in the western United States.Across experiments, we observed wide variation in the rates of four demographic transitions and wide variation in environmental conditions experienced by plants at each stage. For all species, higher precipitation during the first 30 days following seeding was associated with an increase in germination. Conversely, higher soil temperature over this same time period was associated with a significant decrease in germination and emergence, and soil temperature was associated with a substantial portion of the variation in germination and emergence probabilities observed across our seeding experiments.Within the range of precipitation variation observed, we were unable to detect a significant relationship between seedling establishment the first growing season and cumulative precipitation the first year, precipitation during the first spring growing season or annual climatic water deficit (CWD) the first year. Higher CWD the second growing season reduced seedling survival over that time period.Synthesis and applications. Our results show higher soil temperature negatively impacts grass seedling establishment. Restoration efforts should be prioritized when seasonal or subseasonal temperature forecasts indicate likely periods of below average temperatures. These results also indicate that climate warming will make restoration even more difficult, with our model estimates suggesting the 2°C increase in temperature expected in the Great Basin over the coming decades will decrease germination and emergence by about 30%. Lastly, while our field‐based approach provided insight into short‐term drivers of mortality, it did not provide insight into drivers of longer term survival, suggesting a need for further work on predicting long‐term restoration outcomes. [ABSTRACT FROM AUTHOR]

Background: Annual grass invasion and dominance creates a self-sustaining cycle that promotes wildfires and reduces forage abundance. Restoring native plant species to annual grass-invaded ecosystems is fundamental to fostering self-sustaining native plant communities. Aims: We sought to clarify varying restoration strategies on invasive annual and native perennial grass assembly, including strategically modified seeding times, seeding rates, and added water. Methods: We tested the effects of seeding perennial grasses in autumn, spring, or seeding half in autumn and the remaining half in spring, adding water, and varying annual and perennial grass seeding rates on annual and perennial grass life history. Results: While varying perennial grass seeding times did not affect perennial grass germination rates, annual grass germination rates were highest when perennial grasses were seeded in autumn. Seeding perennial grasses in spring produced the highest adult perennial grass density in the first-growing season, but adult perennial grass density in the second-growing season was greatest when seeding occurred in autumn. Second-growing season perennial grass density was highest where annual grass seeding rates were lowest and perennial grass seeding rates were highest. Adding water in the first-growing season produced almost two-times more second-year adult perennial grasses compared to where water was not added. Conclusions: High water availability during the seeding year appears to be the most important factor for retaining perennial grasses in annual grass-invaded ecosystems. [ABSTRACT FROM AUTHOR]

Seeding native plants is a key management practice to counter land degradation across the globe, yet the majority of seeding efforts fail, limiting our ability to accelerate ecosystem recovery., Recruitment requires transitions through several seed and seedling stages, some of which may have overriding influences on restoration outcomes. We lack, however, a general framework to understand and predict differences in these critical demographic processes across species. Functional traits influence fitness, and consequently, trait variation could provide the basis for a framework to explain and predict variation in life stage transition probabilities., We used seed and seedling traits, and field probabilities of germination, emergence, seedling establishment, and survival for 47 varieties of drylands grasses under two watering treatments to identify critical life stage transitions and quantify the effect of traits on cumulative survival through the first growing season., Variation in germination and emergence probabilities explained over 90% of the variation in cumulative survival regardless of seedling survival probabilities or watering treatment, with emergence probability being the strongest predictor of cumulative survival., Coleoptile tissue density and seed mass had significant effects on emergence and germination, respectively, explaining 10-23% of the variation in transition probabilities., Synthesis and applications. While the majority of functional trait work has centred on linking leaf and root traits to resource acquisition and utilization, our study demonstrates that traits associated with germination and emergence may have prevailing influences on restoration outcomes. A portion of these traits have been examined, but there is substantial opportunity to identify other key traits driving these demographic processes. These advancements will underpin our ability to develop trait-based frameworks for overcoming recruitment barriers and facilitating recovery of degraded systems across the globe. [ABSTRACT FROM AUTHOR]

Abstract: Invasive annual grasses tend to construct thinner and less dense root and leaf tissue than native perennial grasses. This allows invasive annuals to grow faster and produce more biomass in the arid grasslands of the United States. Based on these differences we tested the hypotheses that: 1) Competitive effects of the native perennial on the invasive annual will increase as plant developmental stage increases and as drought stress increases. 2) Drought stress will reduce the competitive effect of invasive annuals on native perennials proportionately more than drought stress reduces the competitive effect of native perennials on the invasive annual. 3) Facilitation among native perennial grass seedlings will decrease as developmental stage increases. Competitive effects of native squirreltail, on invasive medusahead, increased as the initial developmental stage of squirreltail increased, but not vice versa. Drought stress reduced the competitive effect of medusahead on squirreltail target biomass more than drought stress reduced the competitive effect of squirreltail on medusahead target biomass. While both squirreltail and medusahead displayed intraspecific facilitation, the net effect of their interspecific interaction was negative for both species. Habitat amelioration manifests itself differently depending on species traits, and can create conditions that simultaneously benefit one species while hindering another. [Copyright &y& Elsevier]

Abstract: Multiple species of annual grasses are invading sagebrush-steppe communities throughout the western United States. Most research has focused on dominant species such as Bromus tectorum (cheatgrass), yet other, less studied annual grasses such as Taeniatherum caput-medusae (medusahead) and Ventenata dubia (ventenata) are spreading rapidly. Future precipitation regimes are expected to have less frequent but more intense rain events, which may affect soil moisture availability and favor these ‘newer’ invasives over cheatgrass. We conducted a full factorial, growth chamber study examining the effects of two watering regimes (small/frequent, large/infrequent rain pulses) across nine soil types on the growth of cheatgrass, medusahead and ventenata. We tested a hypothesis that medusahead or ventenata would have greater growth than cheatgrass with larger/infrequent rain events. The two watering regimes had relatively strong effects on soil water content, but generally did not impact plant growth. In contrast, variation in soil properties such as clay content, pH and soil N correlated with a two- to four-fold change in plant growth. The three invasive grass species generally respond similarly to changes in precipitation regimes and to edaphic factors. Nevertheless, medusahead had 30–40% overall greater root growth compared to the other species and a 15% increase in root growth in response to the large/infrequent watering treatment. Our findings reveal that 1) greater biomass allocation to roots and 2) greater responsiveness of root growth to differing precipitation regimes of medusahead may favor its ecological success over other invasive annuals under future climate scenarios. [Copyright &y& Elsevier]