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Uncertainty in ecosystem restoration can be mitigated by information on drivers of variability in restoration outcomes, especially through experimental study. In southeastern USA pine savannas, efforts to restore the perennial bunchgrass wiregrass ( Aristida beyrichiana ) often achieve variable outcomes in the first year. Although ecotypic differentiation and competition with other native vegetation are known to influence wiregrass seedling establishment and growth, to our knowledge, no studies have examined interactions between these drivers. We experimentally quantified individual and interactive effects of competition, seed source, and soil type on wiregrass density, size, and flowering culm production in the field. We sowed seeds from dry and wet sites reciprocally into dry and wet soils and weeded half of the plots. We found that competition removal resulted in significantly larger plants and a greater proportion of flowering plants with more culms on average, regardless of seed source or soil type. Seeds sourced from a wet site resulted in more plants per plot than seeds from a dry site, which might have been influenced by the greater number of filled seeds from the wet site. After seedlings become established, competition contributes to variation in growth and reproduction. Although competition removal could help start wiregrass populations, the necessity of mitigation depends on fire management needs.

The duration of tree seedling persistence in the understory varies greatly between forests and across environmental conditions within a forest ecosystem. To examine species‐level variation in understory persistence and passage to the sapling life stage, we followed 5236 seedlings in single‐tree canopy gaps and closed canopy conditions over three years and simulated seedling passage times and the number of seedlings required to produce one 1.5‐m tall sapling of five common tree species in a hemlock–hardwood forest of Massachusetts, USA. Averaged across species, it took 26 years in gaps and 31 years under closed canopies to go from a first‐year seedling to a 1.5‐m sapling. Across species, the average number of seedlings needed for one sapling was 294 in gaps and 2674 in closed canopy environments. We observed high interspecific variation in passage times and number required for one sapling. Betula congeners and Pinus strobus took less time and significantly fewer individuals than Acer rubrum and Tsuga canadensis, which are generally regarded as more tolerant of understory conditions. The largest intraspecific difference in gaps versus closed canopy environments was for Quercus rubra, where we estimated the number of seedlings required to produce one sapling in closed canopies to be 172 times higher than in gaps. Stem breakage also increased the number of seedlings needed per sapling, especially in closed canopy environments. We evaluated our estimates in the lab by aging cross‐sections obtained from seedlings in gap and closed canopy conditions. Compared to our empirical age‐to‐height relationships, most simulations tended to underpredict seedling age for a given height, suggesting that passage times may be even longer than our simulations indicated. Our study shows that trees can persist for decades in the seedling life stage, highlighting a need for better‐parameterized recruitment processes in demographic forecasting.

The restoration of herbaceous groundcover species is a challenge in old‐growth grasslands and savannas. Many species persist via below‐ground structures and bud banks, and seed production is often variable. In pine savannas of the south‐eastern United States, wiregrass (Aristida beyrichiana) is a fire‐promoting species that is targeted for re‐establishing vegetation–fire feedbacks. This species is typically sown from seed in sites from which native vegetation has already been eliminated. Because wiregrass seed production and viability are notably variable, we assumed that high seeding rates might be necessary to achieve a high density of recruiting wiregrass. We examined whether seeding rates and soil types affected the number, growth and survival of new seedlings of wiregrass seeds from wet and dry sites. We initiated a 2.0‐ha field restoration project in north‐central Florida in the spring of 2022. We sowed seeds from wet and dry sites (wet and dry seeds, respectively) at each of three seeding rates (very high, 28.0 kg/ha; high, 16.8 kg/ha; typical, 11.2 kg/ha) in wet soil and dry soil. Data on wiregrass size and survival were collected in the fall of 2022 and 2023. In the first year, the number of seedlings per plot from dry and wet seeds was significantly higher at the highest seeding rate than at the other seeding rates. The numbers of seedlings did not differ significantly by soil type. Neither seed source nor soil type significantly affected wiregrass seedling size in the first year or survival to the second year, but seedlings from both dry and wet seeds had significantly lower growth on wet soils. Practical implication. We conclude that high seeding rates are not necessary within the range of percent filled seed that we observed. Overall, the densities of seedlings we documented (2–8 plants/m2) are within the range of those found in other restoration studies. Additionally, although soil moisture may promote establishment, its influence on subsequent demography may depend on putative ecotypes. We examined whether seeding rates and soil types affected the number, growth and survival of new seedlings of wiregrass (Aristida beyrichiana). We sowed seeds from wet and dry sites on wet and dry soils at three seeding rates. In the first year of restoration, the number of seedlings per plot was greatest at the highest seeding rate, and seedlings from both dry and wet seeds had lower growth on wet soils.

Planting or sowing native perennial bunchgrasses is a common restoration practice in grasslands disturbed by agricultural or forestry operations. Bunchgrasses provide fine fuel loads for reinstating fire regimes that promote native plant community development. Wiregrass ( Aristida beyrichiana ) is a dominant bunchgrass used in the restoration of south‐eastern US pine savannas. Amending disturbed soils with native soils or inoculating them with mycorrhizal fungi are restoration practices used to enhance plant growth or establishment. It is unknown, however, whether these practices increase wiregrass biomass, which would promote fire spread and reinstatement of frequent fire regimes We grew wiregrass from seed in four treatments: (1) undisturbed soil from an undisturbed pine savanna (reference treatment), (2) soil disturbed by plantation forestry, (3) disturbed soil mixed with a small amount of undisturbed soil and (4) disturbed soil inoculated with commercial arbuscular mycorrhizal inoculum. After 6 months, we harvested plants and weighed above‐ and below‐ground biomass. We compared total biomass, soil spore counts and root colonization between treatments. Although the undisturbed and disturbed soils used in the experiment did not initially differ in nutrients or mycorrhizal inoculum potential, spore counts were significantly higher in the disturbed soils we collected. At the end of the experiment, total plant biomass (above‐ and below‐ground) was significantly lower in the undisturbed treatment than in all other treatments, which were not significantly different from each other. There were no significant differences in percent root colonization at the end of the experiment, but soil spore counts were significantly higher in the disturbed and commercially inoculated soils than in the undisturbed and mixed soils. Our results suggest that the mycorrhizal relationship might be enhanced in disturbed soils as arbuscular mycorrhizal fungi mobilize nutrients needed by wiregrass; alternatively, disturbed and commercially inoculated soils might harbour a different fungal community than native soils. Although plants had lower biomass in the undisturbed soils, this difference may disappear over time. Practical implication . If the goal of savanna restoration is to re‐establish fire regimes using wiregrass, inoculation is likely unnecessary. In contrast, inoculating the soil may support other objectives, such as increasing biodiversity or accelerating succession.

Uncertainty in ecosystem restoration can be mitigated by information on drivers of variability in restoration outcomes, especially through experimental study. In southeastern USA pine savannas, efforts to restore the perennial bunchgrass wiregrass (Aristida beyrichiana) often achieve variable outcomes in the first year. Although ecotypic differentiation and competition with other native vegetation are known to influence wiregrass seedling establishment and growth, to our knowledge, no studies have examined interactions between these drivers. We experimentally quantified individual and interactive effects of competition, seed source, and soil type on wiregrass density, size, and flowering culm production in the field. We sowed seeds from dry and wet sites reciprocally into dry and wet soils and weeded half of the plots. We found that competition removal resulted in significantly larger plants and a greater proportion of flowering plants with more culms on average, regardless of seed source or soil type. Seeds sourced from a wet site resulted in more plants per plot than seeds from a dry site, which might have been influenced by the greater number of filled seeds from the wet site. After seedlings become established, competition contributes to variation in growth and reproduction. Although competition removal could help start wiregrass populations, the necessity of mitigation depends on fire management needs.

Uncertainty in ecosystem restoration can be mitigated by information on drivers of variability in restoration outcomes, especially through experimental study. In southeastern USA pine savannas, efforts to restore the perennial bunchgrass wiregrass (Aristida beyrichiana) often achieve variable outcomes in the first year. Although ecotypic differentiation and competition with other native vegetation are known to influence wiregrass seedling establishment and growth, to our knowledge, no studies have examined interactions between these drivers. We experimentally quantified individual and interactive effects of competition, seed source, and soil type on wiregrass density, size, and flowering culm production in the field. We sowed seeds from dry and wet sites reciprocally into dry and wet soils and weeded half of the plots. We found that competition removal resulted in significantly larger plants and a greater proportion of flowering plants with more culms on average, regardless of seed source or soil type. Seeds sourced from a wet site resulted in more plants per plot than seeds from a dry site, which might have been influenced by the greater number of filled seeds from the wet site. After seedlings become established, competition contributes to variation in growth and reproduction. Although competition removal could help start wiregrass populations, the necessity of mitigation depends on fire management needs.