Herbivory and competition during the regeneration phase influence forest successional dynamics. We demonstrated the importance of using the Target Plant Concept to identify and overcome site limiting factors for subtropical maritime forest restoration associated with deer browsing and competition. Quercus virginiana Mill. (live oak) bareroot seedlings were planted into clearcuts along the US Southern Atlantic coast with different treatment combinations of herbivory control (fenced or non-fenced) against white-tailed deer (Odocoileus virginianus Zimm.) browsing and competing vegetation removal (none, one-year, or two-years). After three growing seasons, mean seedling survival was 61% with no significant treatment differences. Control of browse and vegetation interacted to facilitate growth of live oak; seedlings were significantly larger for all response parameters (diameter, height, crown width) when fenced and treated with vegetation control. Removal of vegetation improved seedling performance only in fenced plots, however, indicating a shift in pressure from herbivory to competition as the most limiting site factor when deer were excluded. After the second growing season, foliar nitrogen was greater in fenced plots than non-fenced plots and greater in two-year vegetation control subplots than non-vegetation control subplots. This result, however, was absent after the third growing season. Three years after clearcutting, there was no evidence of Q. virginiana natural regeneration in non-fenced plots. Even with artificial regeneration in non-fenced plots, Q. virginiana growth was slow, indicating that herbivory was a key limiting factor. Our findings illustrate the importance of accounting for site limiting factors and may aid in developing management prescriptions to promote semi-evergreen oak regeneration in ecosystems with high pressure from herbivory and competing vegetation.

Herbivory is a common forest regeneration challenge across ecosystems. While fencing effectively reduces animal browse damage, it can be impractical. Tree shelters are an alternative forest restoration tool to protect seedlings from herbivory that may also provide a favorable microclimate. Yet, regeneration responses to tree shelters often vary among tree species, environmental conditions, and shelter specifications. To restore the once dominant Quercus virginiana (live oak) and its associated conservation values to subtropical U.S. maritime forests, control of animal browsing is critical. We evaluated the effects of tube and mesh tree shelters to exclude animal browse, combined with the use of controlled-release fertilizer to promote Q. virginiana seedling growth. After two growing seasons, mean seedling survival was 83% for protected seedlings, either from tube or mesh shelters, compared to 68% with non-sheltered seedlings. Seedlings in solid-wall tube shelters had significantly less browse incidence compared to both seedlings in mesh shelters and non-sheltered seedlings. Seedlings in tube shelters had greater height and diameter, followed by mesh shelters, and lastly, the no shelter treatment. Fertilizer resulted in higher browsing incidence and greater seedling height and diameter after the first growing season only, with no shelter treatment interactions. Our findings illustrate the efficacy of tree shelters to improve early regeneration success of Q. virginiana and may have application to the restoration of other forest ecosystems.

Restoration of root hemiparasite trees, such as Hawaiʻi's endemic Santalum species (ʻiliahi), may benefit from underplanting in stands of suitable hosts like the nitrogen‐fixing native tree, Acacia koa (koa). At a pasture site on Hawaiʻi Island previously reforested with koa, we underplanted seedlings of the island‐endemic sandalwood species, Santalum paniculatum, to examine the tradeoff between access to an established root network (distance to the nearest koa tree) under variable overstory shading (8.8–90.1% canopy openness range) during regeneration establishment. We hypothesized that there is an optimal parasite–host spacing and canopy openness that balance parasitic resource transfer with light availability. ʻIliahi seedling survival was 96% with no survival treatment differences. ‘Iliahi seedling growth was positively related to canopy openness but negatively related to the distance to the nearest koa tree, and the slope of these relationships increased over time. Leaf photosynthetic light compensation points, light saturation points, and stomatal density mostly followed similar trends as growth. These results demonstrate that ‘iliahi can be successfully underplanted in an established koa stand, which benefits ‘iliahi plantings and contributes to diversifying initial restoration and reforestation plantings. There appears to be a significant tradeoff in planting distance between benefits from and competition with the host; however, the improvement in growth with increased canopy openness appeared to be much greater than the effect of planting distance. Underplanting into an established host stand with sufficient canopy openness can help restore functionally compatible and abundant ‘iliahi regeneration into forests.