Pine Savanna Research Articles

Competition limits first-year growth and flowering of wiregrass (Aristida beyrichiana) at a sandhills restoration site.

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.

Fire refugia patch dynamics differ between prescribed fires and wildfires in longleaf pine savanna

Increasing wildfire activity has spurred an increasing push for the application of prescribed fire to reduce wildfire risk while simultaneously acting as a surrogate for fire’s historical role as a fundamental ecosystem process. However, prescribed fires are often ignited using uniform ignitions to maintain operational control and there are concerns that they may not be able to replicate the landscape heterogeneity, particularly patterns in unburned patches, generated by historical fires. Fire refugia, unburned areas within fire perimeters, play an integral role in determining post-fire recovery and community structure. We assess patterns in fire refugia across 443 large (>200 ha) wildfire and prescribed fire perimeters using remotely sensed fire severity data in longleaf pine (Pinus palustris) savannas of the Florida Panhandle. Contrary to concerns, large prescribed fires had a significantly greater proportion of unburned area than wildfires, driven by larger refugia patch sizes. Drier conditions promoted smaller and more numerous fire refugia patches. Our study demonstrates differences in wildfires versus prescribed fire outcomes on landscape structure, with implications for future longleaf pine savanna management.

Phosphorus controls symbiotic nitrogen fixation in fire‐dependent longleaf pine savannas

Abstract Symbiotic nitrogen (N) fixation has the potential to replenish fire‐induced N losses in frequently burned ecosystems. A strong relationship between fire and fixation may exist because fire volatilizes N and mineralizes phosphorus (P), creating N‐poor, P‐rich soils that favour plants capable of N‐fixation. However, human activities have enriched ecosystems with N, which may complicate the interplay among fire, fixation and soil P. We evaluated how N and P modulate the relationship between fire and symbiotic N fixation in longleaf pine savannas, where it was previously documented that N fixation fails to replenish N losses from fire. Across gradients of stand age and fire frequency, we investigated how N and P availability influence fixation, and we established a nutrient addition experiment to evaluate the effects of N and P on legume growth, fixation and mycorrhizal investment. We uncovered a clear signal of P limitation of herbaceous legumes. Legume growth and fixation were linked to the availability of soil mineral P and were further stimulated by P additions. In contrast, neither soil N availability nor N additions affected legume growth or fixation. Synthesis. Our findings suggest that symbiotic N fixation in sandhill longleaf pine savannas is controlled by soil P availability, which varies according to soil age and parent material. Therefore, fixation may only counterbalance N losses from fire if there is enough P in the soil to support this process. Nonetheless, recent N enrichment in contemporary longleaf pine ecosystems may have reduced the importance of N fixation as a post‐fire recovery mechanism.

Studies in the vascular flora of the southeastern United States. X

As part of ongoing work on the Flora of the Southeastern United States (Weakley & Southeastern Flora Team 2023) and related projects, as well as for general floristic, conservation, and scientific work in eastern North America, it is essential to document taxonomic and nomenclatural changes and significant distribution records. Here, we propose six new species of graminoids (two Rhynchospora, three Dichanthelium, and one Anatherum)—five from fire-maintained pine savannas and embedded wetlands of the southeastern Coastal Plain and one from the floristically and ecologically related fire-maintained pine savannas of North Andros Island in The Bahamas. We provide rationale and documentation for the “taxonomic resurrection” of Vaccinium ashei, an economically important member of Vaccinium sect. Cyanococcus, based on morphology, estimation of ploidy level with flow cytometry, and phylogenomic analysis based on high-throughput DNA sequencing. We make four new combinations in Convolvulus to accommodate the inclusion of Calystegia in Convolvulus to resolve paraphyly. We also make six new combinations necessary to recognize sect. Leptopogon of Andropogon at generic rank, as Anatherum, based on the phylogenetic work of other researchers and the previously incomplete transfer of recognized species to Anatherum, providing the needed names to recognize this group of species in genus Anatherum in North American floristic treatments. We document the surprising discovery of Carex lutea, previously believed to be endemic to two counties in eastern North Carolina, in two counties in the panhandle of Florida, and a county in eastern South Carolina—discoveries aided by iNaturalist and Facebook. We document new states as being within the distribution ranges of additional species: Quercus similis (Florida), Juncus brachycephalus (Arkansas and Missouri), Rhexia mariana var. mariana (Ohio), Asarum acuminatum and Elionurus tripsacoides (Alabama), and Mecardonia procumbens (Georgia). Other important distributional records, many representing rediscoveries of conservationally significant, extant populations of plants previously considered of only historical occurrence in a state, are also reported: Alabama (Arnica acaulis, Asclepias connivens, Berberis canadensis, Bulbostylis warei, Ctenodon viscidulus, Parnassia grandifolia, and Pinguicula pumila) and Georgia and Florida (Lobelia boykinii).

Pine trees structure plant biodiversity patterns in savannas.

Overstory trees serve multiple functions in grassy savannas. Past research has shown that understory species can vary along gradients of canopy cover and basal area in savannas. This variation is frequently associated with light availability but could also be related to other mechanisms, such as heterogeneity in soil and litter depth and fire intensity. Several savanna studies have found differences in understory plant functional groups within the local environment near trees versus away from them in canopy openings. Although small-scale variation is known to be high in southeastern U.S. pine savannas, patterns in understory species diversity have not been examined at the scale of individual overstory pine trees in this system. We conducted an observational study of the relationship between understory plant communities and proximity to individual pine trees in xeric and mesic pine savannas in frequently burned sites (1-3 year intervals). We recorded the plant community composition in plots adjacent to tree boles (basal) or outside crown driplines (open). Within each environment, raw species richness was significantly greater in open locations, where light transmittance was greater. In contrast, rarified species richness did not differ. Multivariate analyses showed that community composition differed significantly between basal and open plots. One native, woody species in each environment, Serenoa repens (W. Bartram) Small in mesic and Diospyros virginiana L. in xeric, was more abundant in basal plots. In mesic environments, eight species had greater occurrence in open plots. In xeric environments, four understory forbs were more abundant in open plots. Our results support previous research indicating that individual pine trees are associated with significant variation in understory vegetation in pine savannas.

Forest management for water yield: Assessing the barriers and impacts of privately-owned open pine woodlands in the Southeastern United States

In the Southeastern United States, freshwater resources are stressed due to human development, population growth, expansion of agricultural irrigation, and climate change. Restoring land to a low-density, fire-maintained longleaf pine (Pinus palustris) savanna and woodland ecosystem may provide distinct ecosystem services such as increases in water quantity for vulnerable watersheds. To understand how economic incentives may bolster restoration programs, we analyze the economic and hydrologic impacts of longleaf pine restoration scenarios. We compare these scenarios against other common land uses in the Coastal Plain of Georgia, a major forestry state located in the Southern United States, identifying the financial barriers and water use impacts of alternative forest management regimes. Longleaf pine restoration shows the greatest increase in water yield per acre at 66 % over baseline timber production scenarios but at a lower timber value return. Thinning planted loblolly pine (Pinus taeda) stands to low-density woodlands may offer a more cost-efficient, immediate alternative that improves water yields by 38 %. Current incentives to restore native habitats on private lands increase financial returns but lack sufficient incentives and governance to meet or exceed baseline forest income levels by $90-$235 ha-1 annually for longleaf savanna restoration. In the future, the emerging ecosystem service market in Georgia may steer decisions about competing values of carbon storage, water yield, and native habitat restoration.

Characterization of the bee community and pollination network in a southeastern U.S. pine savanna

Although the fire-maintained pine savannas of the southeastern U.S. Coastal Plain are recognized for their plant diversity, pollinators associated with these ecosystems remain comparatively understudied. Here we present the results from a season-long effort to record bee-flower interactions at a single site in Florida. We collected 93 bee species (out of an estimated 117) from 79 flower species, with a total of 446 unique interactions. Bee richness and the number of interactions exhibited a bimodal pattern, dipping in mid-summer before an estimated peak in October. The most important floral resources changed throughout the season as did the composition of bees, with the spring and fall periods being particularly distinct. We found that pollen specialists (that collect pollen from a single family of plants) and pollen generalists accounted for a similar proportion of bee species over the entire season. However, pollen generalists outnumbered pollen specialists in the spring and summer before reversing in the fall. Pollen specialists visited significantly fewer plant species and families than pollen generalists and many were collected exclusively from their host family. This was particularly the case for aster specialists active only during the fall. We estimate that between 18.3-25.8% of the local bee fauna depends directly on the overstory trees for nesting habitat including dead wood and resin. Two management recommendations can be made based on these results. First, because fall is the period of peak floral abundance and bee richness, including many late-season aster specialists, it is probably the least favorable time for prescribed fire. Second, considering that a significant proportion of native bees depend on dead wood for nesting, it is important to retain standing dead trees and fallen wood whenever possible.

Mechanical soil disturbance in a pine savanna has multiyear effects on plant species composition

AbstractSoil disturbance threatens native perennial grasslands and savannas worldwide, including pine savannas of the North American Coastal Plain. Disk harrows are used in the region to plow linear features for firebreaks to contain prescribed fires, to manage game and other wildlife, and to reduce wildfire hazard to protect forest resources. However, the long‐term response of vegetation to these disturbances has not been well investigated. Our aim was to compare vegetation changes over time (0–9 years) following repeated disturbance by disking and a single disturbance by disking for firebreaks with undisturbed vegetation within a native pine savanna. We hypothesized that (1) a single disking event has multiyear effects on plant species composition and abundance because of the loss of perennial, dispersal‐limited species, but that partial survival of propagules allows the recovery to be more complete than following repeated disturbance, and (2) post‐disturbance changes are determined by species' life‐history characteristics resulting in a successional trajectory toward the undisturbed community. We established 10 plots within a repeated‐disturbance firebreak and a single‐disturbance firebreak, and in undisturbed vegetation (n = 30). We identified plant species within the plots six times over nine years, categorized plant species by life span, seed bank persistence, and dispersal mechanism, and assessed changes in the plant community using ordination. Changes in species composition in both repeated and single disturbance treatments showed a pattern consistent with succession toward the undisturbed plant community, but vegetation in neither disturbance treatment matched undisturbed treatment conditions within the nine years of study. Repeated‐disturbance plots progressed from a high occurrence of annuals to species with persistent seed banks and wind‐dispersed species. Single‐disturbance plots were more strongly associated with perennials, species lacking a persistent seed bank, and species dispersed by vertebrate consumption, but not to the same degree as undisturbed plots, although differences decreased slightly over time. Our results relating to narrow mechanical soil disturbances in pine savanna vegetation are consistent with studies concluding that similar but larger scale disturbances have long‐term degradational effects on the plant community. Therefore, conservation management plans should consider the possible negative long‐term effects of soil disturbance on native perennial herbaceous plant communities.

Priority effects and competitive exclusion by C4 grasses on longleaf pine savanna restoration sites

On grassland and savanna restoration sites, planted native C4 grasses can competitively exclude other co‐introduced plant functional groups, with negative implications for ecosystem functioning and restoration success. Previous studies have suggested that C4 grass competitive exclusion does not occur in longleaf pine savannas of the North American Coastal Plain; however these studies were primarily conducted on old growth xeric sites. We designed an experiment to test competitive interactions between C4 grasses and forbs introduced by seed to mesic savanna restoration sites. Research installations were established on three former bahiagrass (Paspalum notatum) pastures in Florida, within which six different seed treatments were applied: (1) C4 grasses and forbs together in years 1 and 2, (2) C4 grasses alone in year 1 and forbs alone in year 2, (3) forbs alone in year 1 and C4 grasses alone in year 2, (4) C4 grasses alone in both years, (5) forbs alone in both years, and (6) an unplanted control. All plots were sampled 1 year after the second seeding event. We found that C4 grasses competitively excluded forbs, reducing cover of forbs arriving on the site at the same time, as well as those arriving in the second year. The highest forb species richness and cover was found in the three treatments that did not contain C4 grasses in year 1, and different C4 grass species exhibited different community associations. These findings suggest that restoration seed mixes for longleaf pine savannas should account for the competitive interactions of C4 grasses.

Culex erraticus (Diptera: Culicidae) utilizes gopher tortoise burrows for overwintering in North Central Florida.

Mosquito-borne diseases represent a significant threat to human and animal health in the United States. Several viruses, including West Nile, Saint Louis encephalitis, and Eastern equine encephalitis are endemic. In humans, the disease is typically detected during the summer months, but not during the winter months. The ability of these viruses to reemerge year after year is still not fully understood, but typically involves persistence in a reservoir host or vector during periods of low transmission. Mosquito species are known to overwinter at different life stages (adults, larvae, or eggs) in manufactured or natural sites. Gopher tortoise burrows are known to serve as refuge for many vertebrate and invertebrate species in pine savannas. In this study, we surveyed the interior of gopher tortoise burrows for overwintering mosquitoes. We identified 4 species (Anopheles crucians s.l., Culex erraticus, Mansonia dyari, and Uranotaenia sapphirina). Cx. erraticus was the most abundant, and its presence and abundance increased in winter months, implying that this species utilized gopher tortoise burrows for overwintering. Bloodfed Cx. erraticus and An. crucians s.l. females were detected. While An. crucians s.l. fed exclusively on the white-tailed deer, Cx. erraticus had a more diverse host range but fed primarily on the gopher tortoise. Tortoises and other long-lived reptiles like the American alligator have been shown to sustain high viremia following West Nile virus (WNV) and Eastern equine encephalitis virus (EEEV) infection and therefore could play a role in the maintenance of these viruses. In addition, Cx. erraticus is naturally infected with WNV and is a known bridge vector for EEEV. As such, these overwintering sites may play a role in perpetuating over-winter arboviral activity in Florida.

Plant‐mediated effects of fire and fragmentation drive plant–pollinator interaction β‐diversity in fire‐dependent pine savannas

Interaction β‐diversity is a measure essential for understanding and conserving species interactions and ecosystem functioning. Interaction β‐diversity explains the variation in species interactions across spatial and temporal gradients, resulting from species turnover or interaction rewiring. Each component of interaction β‐diversity has different ecological implications and practical consequences. While interaction β‐diversity due to species turnover is related to assembly processes and fragmentation, rewiring can support high biodiversity and confer resilience to ecological networks. However, it is unclear whether both components respond to the same or different ecological drivers. Here, we assessed the ecological drivers of plant–pollinator interaction β‐diversity and its components across 24 sites in 9 longleaf pine (LLP) savannas in north and central Florida. We evaluated the effects of flowering plant composition and flower abundance, vegetation, fire regime, soil moisture, terrain characteristics, climate, spatial context and geographic location. We used path analysis to evaluate the drivers of spatial interaction β‐diversity and its main components. We then used generalized linear mixed models to assess the temporal patterns of spatial β‐diversity among sites within preserves. We found that plant–pollinator networks in LLP savannas are highly variable across space and time, mainly due to species turnover and possibly in response to abiotic gradients and dispersal boundaries. Flower abundance and flowering plant composition, geographic location, fire seasonality, soil moisture, and landscape context were the main drivers of plant–pollinator β‐diversity, highlighting the role of fire management and habitat connectivity in preserving plant–pollinator networks.

The influence of wildfire on invasive plant abundance and spatial structure in eastern ponderosa pine savanna

The influence of wildfire on invasive plant abundance and spatial structure in eastern ponderosa pine savanna

Documenting Two Centuries of Change in Longleaf Pine (Pinus palustris) Forests of the Coastal Plain Province, Southeastern USA

While many tree species occur across the Coastal Plain of the southeastern United States, longleaf pine (Pinus palustris C. Lawson) savannas and woodlands once dominated this region. To quantify longleaf pine’s past primacy and trends in the Coastal Plain, we combined seven studies consisting of 255,000 trees from land surveys, conducted between 1810 and 1860 with other descriptions of historical forests, including change to the present day. Our synthesis found support that Pinus palustris predominantly constituted 77% of historical Coastal Plain trees and upland oaks (Quercus) contributed another 8%. While Pinus still dominates these forests today (58% of all trees), most are now either planted loblolly (Pinus taeda L.) or slash (Pinus elliottii Engelm.) pines. Water oak (Quercus nigra L.), live oak (Quercus virginiana Mill.), sweetgum (Liquidambar styraciflua L.), and red maple (Acer rubrum L.) have increased their proportions compared to historical surveys; both longleaf pine and upland oaks have declined to ≤5% of all trees. Our work also supports previous estimates that longleaf pine originally dominated over 25–30 million ha of Coastal Plain forests. As late as the early 1900s, longleaf pine may still have covered 20 million ha, but declined to 7.1 million ha by 1935 and dropped to 4.9 million ha by 1955. Longleaf pine’s regression continued into the mid-1990s, reaching a low of about 1.3 million ha; since then, restoration efforts have produced a modest recovery to 2.3 million ha. Two centuries of overcutting, land clearing, turpentining for chemicals, fire exclusion followed by forest densification by fire-sensitive species, and other silvicultural influences, including widespread loblolly and slash pine plantations, have greatly diminished the Coastal Plain’s once extensive open longleaf pine forests.

Longleaf pine savannas reveal biases in current understanding of savanna biogeography

AbstractBiased understanding of savanna biogeographyGrasslands and savannas exist across a wide range of climates. Mesic savannas, with highly variable tree densities, are particularly misunderstood and understudied in comparison to arid and semi‐arid savannas. North America contains historically extensive mesic savannas dominated by longleaf pine. Longleaf pine savannas may have once been the largest savanna type on North America, yet these ecosystems have been overlooked in global syntheses. Excluding these “Forgotten Ecosystems” from global syntheses biases our understanding of savanna biogeography and distribution.Evolutionary history and distinct climate of longleaf savannasWe assessed the evolutionary history and biogeography of longleaf pine savannas. We then harmonize plot data from longleaf savannas with plot data from valuable existing global synthesis of savannas on other continents. We show that longleaf pine savannas occur in a strikingly distinct climate space compared to savannas on Africa, Australia, and South America, and are unique in having wide ranging tree basal areas.Future directionsGrass‐dominated ecosystems are increasingly recognized as being ancient and biologically diverse, yet threatened and undervalued. A new synthesis of savanna ecosystems considering their full range of distributions is needed to understand their ecology and conservation status. Interestingly, the closest analogues to North American savannas and their relatives in Mesoamerica and the Caribbean may be Asian savannas, which also contain mesic fire‐driven pine savannas and have been similarly neglected in existing global syntheses.

Effects of season of fire on bee-flower interaction diversity in a fire-maintained pine savanna.

Whereas the Coastal Plain of the southeastern United States historically experienced fire primarily during the mid-summer lightning season, managers today typically apply prescribed fire during the late winter or early spring months. The ecological implications of this discrepancy remain poorly understood, especially with regard to pollinators and their interactions with flowers. In a replicated field experiment, we compared the abundance and richness of bees and bee-flower interactions among pine savanna plots in Florida that were burned either during the winter, spring, summer, or fall. We netted 92 bee species from 77 species of flowers, representing 435 unique bee-flower interactions in total. When analyzing the results from each month separately, we detected significant short-term reductions in the number of bees and bee-flower interactions following fires regardless of season. Although bee abundance and richness did not differ over the entire season, bee-flower interaction richness was significantly higher overall in spring and summer plots than in fall plots and the composition of both bees and bee-flower interactions differed significantly among treatments. Several bee-flower interactions were significantly associated with one or more of the treatments. Some of these associations could be attributed to differences in flowering phenology among treatments. Taken together, our findings suggest that season of fire has modest but potentially important implications for interactions between bees and flowers in southeastern pine ecosystems. Because most flowering plants within our study region are pollinated by a variety of bees and other insects, and most bees endemic to the region are polylectic, season of fire may not be very important to either group overall. However, the timing of fire may be more important to particular species including certain flower specialists and fire-sensitive taxa such as butterflies. Future research targeting such species would be of interest.

Seed Source for Restoration: Little Bluestem (Schizachyrium scoparium (Michx.) Nash) and the Carolina Sandhills

Prairie and savanna ecosystems have declined dramatically worldwide. In the Southeastern United States, longleaf pine savannas have been reduced to less than 3% of their pre-European range. Restoring longleaf pine across the area has become a regional goal. Little bluestem (Schizachyrium scoparium (Michx.) Nash) is critical to carrying the ecologically important fire through this ecosystem in some longleaf pine savannas. Little bluestem has a range that spans most of north America and is thought to display ecotypic variation. As a part of a longleaf pine restoration project in Camden, SC, we investigated whether the seed source of little bluestem and the site preparation techniques impacted the survival and growth of broadcasted seeds. In the field and greenhouse, we compared locally and commercially sourced seeds and field site preparation techniques including discing, raking, or no treatment. At the end of the growing season, there were significantly more plants grown from seeds collected locally compared to plants from seeds available commercially. Plants grown from locally collected seeds also invested more heavily in roots than plants grown from commercial seeds. Site preparation techniques did not appear to significantly impact plant survival. Collecting seed locally will help to ensure long-term restoration success by establishing populations of plants that are adapted to the local environmental conditions.

A cost assessment of intensive wild quail management on private lands in the southeastern United States

AbstractPrivate landowners who operate multifunctional landscapes play a critical role in the conservation of native and imperiled species, and the restoration of native ecosystems. In the southeastern United States, both northern bobwhite (Colinus virginianus) and pine savanna ecosystems are imperiled and heavily reliant on conservation efforts by private landowners. Engaging private landowners in the restoration and management of pine savannas and grasslands is essential to the recovery of northern bobwhite, which is also managed as a game species. Since the early 1900s, the cultural tradition of wild bobwhite hunting has motivated landowners to manage their properties to increase bobwhite populations. However, the costs and revenues associated with intensive wild bobwhite management and hunting are imperfectly understood. From May 2021 to February 2022, we conducted semistructured interviews with landowners and land managers of 37 wild bobwhite hunting properties (total of 65,317 ha in bobwhite management) in Alabama, Georgia, Florida, and South Carolina to enumerate the costs and revenues associated with intensive wild bobwhite management. Landowners spent an average of $154/acre/year (~$381/ha/year; median of $142/acre/year or ~$352/ha/year) to manage for northern bobwhite. These costs included salaries and benefits for labor, depreciated equipment and infrastructure expenditures, and other supplies (e.g., fuel, seed) needed to maintain wild bobwhite populations and their habitat. Few properties offset their bobwhite management costs with revenues generated on the property, including hunting revenues. Non‐financial motivations for owning a bobwhite property included a strong land stewardship ethic, the desire to maintain rural lifestyles and family heritage, and securing hunting and recreational opportunities. Through wild quail management, private landowners are helping to secure critical habitat for threatened and endangered species and increasing the landscape's overall resilience to climate change without the use of public funding.

Experimental translocation for restoration of an ecosystem engineer

The longleaf pine (Pinus palustris Mill.) savanna ecosystem in North America has declined by 97% from its historic range and its restoration is a conservation priority. The southeastern pocket gopher (Geomys pinetis), an ecosystem engineer in longleaf pine savannas, is absent from most of its historic range. Translocation of pocket gophers may be needed to reestablish ecosystem services of restored longleaf savannas. To determine translocation feasibility, we quantified survival, site fidelity, and homing of pocket gophers translocated using soft releases (with a starter burrow system; n = 13), hard releases (without a starter burrow system; n = 17), or released into their own burrows (control; n = 10). Naïve survival was 46 and 35% for soft‐ and hard‐released individuals, respectively, and 80% for controls. Most mortalities of translocated individuals (75.0%) occurred within 12 days. Including all radiotagged pocket gophers, daily survival of soft‐released animals ( = 0.990) was intermediate between hard‐released ( = 0.986) and controls ( = 0.993), and only hard‐released was lower than controls. Using only individuals that survived greater than 14 days, we found no difference in daily survival. Site fidelity was low, with 70% of translocated pocket gophers making aboveground movements away from release point. However, soft‐released individuals stayed at the release point three times longer than hard‐released animals. No pocket gopher exhibited homing. Our results suggest translocation has potential for establishing pocket gopher populations into restored longleaf pine savannas and that mitigating mortality during establishment will increase the likelihood of success.

Long-term, large-scale experiment reveals the effects of seed limitation, climate, and anthropogenic disturbance on restoration of plant communities in a biodiversity hotspot

Ecological restoration is essential for maintaining biodiversity in the face of dynamic, global changes in climate, human land use, and disturbance regimes. Effective restoration requires understanding bottlenecks in plant community recovery that exist today, while recognizing that these bottlenecks may relate to complex histories of environmental change. Such understanding has been a challenge because few long-term, well-replicated experiments exist to decipher the demographic processes influencing recovery for numerous species against the backdrop of multiyear variation in climate and management. We address this challenge through a long-term and geographically expansive experiment in longleaf pine savannas, an imperiled ecosystem and biodiversity hotspot in the southeastern United States. Using 48 sites at three locations spanning 480 km, the 8-y experiment manipulated initial seed arrival for 24 herbaceous plant species and presence of competitors to evaluate the impacts of climate variability and management actions (e.g., prescribed burning) on plant establishment and persistence. Adding seeds increased plant establishment of many species. Cool and wet climatic conditions, low tree density, and reduced litter depth also promoted establishment. Once established, most species persisted for the duration of the 8-y experiment. Plant traits were most predictive when tightly coupled to the process of establishment. Our results illustrate how seed additions can restore plant diversity and how interannual climatic variation affects the dynamics of plant communities across a large region. The significant effects of temperature and precipitation inform how future climate may affect restoration and conservation via large-scale changes in the fundamental processes of establishment and persistence.

Pyrophilic Plants Respond to Postfire Soil Conditions in a Frequently Burned Longleaf Pine Savanna.

AbstractFire-plant feedbacks engineer recurrent fires in pyrophilic ecosystems like savannas. The mechanisms sustaining these feedbacks may be related to plant adaptations that trigger rapid responses to fire's effects on soil. Plants adapted for high fire frequencies should quickly regrow, flower, and produce seeds that mature rapidly and disperse postfire. We hypothesized that the offspring of such plants would germinate and grow rapidly, responding to fire-generated changes in soil nutrients and biota. We conducted an experiment using longleaf pine savanna plants that were paired on the basis of differences in reproduction and survival under annual ("more" pyrophilic) versus less frequent ("less" pyrophilic) fire regimes. Seeds were planted in different soil inoculations from experimental fires of varying severity. The more pyrophilic species displayed high germination rates followed by species-specific rapid growth responses to soil location and fire severity effects on soils. In contrast, the less pyrophilic species had lower germination rates that were not responsive to soil treatments. This suggests that rapid germination and growth constitute adaptations to frequent fires and that plants respond differently to fire severity effects on soil abiotic factors and microbes. Furthermore, variable plant responses to postfire soils may influence plant community diversity and fire-fuel feedbacks in pyrophilic ecosystems.