Prairie reconstruction has become a common method for reestablishing tallgrass prairie communities in the central United States. With the objective of creating plant communities that approximate remnant (reference) prairies, managers are interested in identifying: (1) best methods for reconstructing reference community conditions; (2) the rate of change in plant communities through time following reconstruction; and (3) species present in remnant communities but missing from reconstructed communities. This information is important in the development of adaptive management strategies during active reconstruction. We used a chronosequence approach to assess the success of two reconstruction methods in emulating local, reference remnant prairie plant communities. We compared broadcast dormant seeding following two types of site preparation, agricultural cropping (Crop) or herbicide control in existing grass assemblages (Grass), and remnant communities. The Crop site preparation method resulted in a rapid increase in richness shortly following seeding. Although more similar to remnant assemblages initially, the Grass method took longer for mean coefficient of conservatism and floristic quality index to approach conditions of the reference communities. However, neither method resulted in plant community compositions that converged with the reference through time. Further, indicator species analysis identified a diverse assemblage of species lacking from the reconstructed prairies. These results suggest the need to develop management strategies for establishing the “missing” species during reconstruction and provide further support for protection and conservation of existing remnant prairies.

Ecosystems are under increasing stress from environmental change, including invasion by non-native species that can disrupt ecological processes and functions. Chinese tallow [Triadica sebifera (L.) Small] is a highly invasive tree species in southeastern US forests, prairies, and wetlands, and effectively managing this invasive species is a significant challenge for scientists and land managers. In this review, we synthesize the literature on invasion ecology and management of Chinese tallow. Our review suggests that the invaded range of Chinese tallow is currently limited by dispersal in many areas and by low temperatures and low soil moisture, and by high soil salinity and frequent flooding in others, but these barriers may be overcome by increased dispersal, phenotypic plasticity, and/or rapid evolution. Invasions by Chinese tallow are facilitated by both the invasiveness of the species and the invasibility of the recipient communities. Invasiveness of Chinese tallow has been attributed to fast growth, high fecundity, a persistent seed bank, aggressive resprouting, abiotic stress tolerance, and the ability to transform fire maintained ecosystems. Some of these traits may be enhanced in invasive populations. Anthropogenic and natural disturbances, lack of herbivore pressure, and facilitation by soil microbes enhance the intensity of Chinese tallow invasions. Biological control of Chinese tallow is being developed. Treatments such as herbicides, prescribed fire, and mechanical control can effectively control Chinese tallow at the local scale. A combination of these treatments improves results. However, a proactive management approach would simultaneously achieve invasion control and promote subsequent ecological restoration, especially in the context of legacy effects, secondary invasions, and/or variable ecosystem responses to different control treatments. Future research should clarify the roles of species invasiveness and community invasibility, increase our understanding of the effects of Chinese tallow in invaded communities, and develop viable management regimes that are effective in both controlling or reducing the probability of Chinese tallow invasion and restoring desired native communities.

Background: Longleaf pine (Pinus palustris Mill.) seedlings have a morphological "grass stage" that is considered to be an adaptation to frequent surface fire regimes. However, fire can kill longleaf pine seedlings and thus may play an important role in longleaf pine regeneration dynamics. We used a prescribed burn simulation tool designed to treat individual grass stage longleaf pine seedlings with controlled delivery of fire treatments and then measured survival and growth responses through two growing seasons. Naturally regenerated grass stage longleaf pine seedlings were randomly selected from three size classes and each assigned one of four treatments (Control, no treatment; Clip, mechanical needle removal; LB, a low-temperature burn treatment; or HB, a high-temperature burn treatment) in both the dormant season (January) and the growing season (May). Results: Seedlings greater than 15 mm root collar diameter had greater than 0.5 probability of survival after the first growing season in the HB treatment, regardless of the season of treatment application, and seedlings across all sizes had greater than 0.6 probability of survival in the LB treatment after the first growing season. The growing season treatment application resulted in additional mortality during the second growing season, across all seedling size classes, which was not observed in the dormant season application. Burning reduced root collar growth through two growing seasons, likely due to needle mortality and the subsequent prioritization of growth to needle production rather than to root or stem growth. Conclusions: Our results suggest that the interplay between seedling size and fire intensity likely contributes to the success of longleaf pine natural regeneration and that seedling size should be considered when scheduling the first burn following planting of longleaf pine seedlings.

The increase in compounding disturbances, such as “hotter droughts” coupled with insect outbreaks, has significant impacts on the integrity of forested ecosystems and their subsequent management for important ecosystem services and multiple-use objectives. In the Southern Sierra Nevada, years of severe drought have resulted in unprecedented tree mortality across this mountainous landscape. Additionally, past land management practices, including fire suppression, have led to overly stocked, homogenous forest stand structures, dominated by small diameter, shade-tolerant and fire-intolerant tree species. Thus, the current condition of the landscape has further increased the susceptibility of forest trees to multiple stressors. We sought to determine the effects of extreme drought and insect outbreaks on tree mortality and their influence on forest stand structure and composition. To characterize mortality patterns, we monitored the condition of mature forest trees (>25.4 cm diameter at breast height) across 255 monitoring plots with four repeated measurements from 2015 through 2017. Tree mortality varied by species and through time. Reductions in pine species (Pinus lambertiana Douglas and P. ponderosa Lawson & C. Lawson) occurred earlier in the study period than Abies concolor (Gord. & Glend.) Lindl. Ex Hildebr. or Calocedrus decurrens (Torr.) Florin. Across species, larger tree size, most often associated with tree height, was consistently related to increased survival in mature, overstory trees. As expected, sites with greater pine stocking and subsequently more bark beetle (Curculionidae: Scolytinae) host availability had increased pine mortality, especially for P. ponderosa. For Abies concolor, lower overstory basal area increased tree survival for this species. This study highlights the importance of effective forest monitoring, especially during a period of unprecedented ecological change as the compounding disturbance had a disproportional effect on pine species in smaller diameter classes. Proactive forest management may be necessary to maintain and promote these ecologically important species in heterogeneous mixtures across the landscape.

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& Key message The suite of traits expressed as seedlings by coastal and mountain longleaf pine and south Florida slash pine suggest they can survive fire in the seedling stage. In contrast, loblolly pine and typical slash pine tolerate fire when mature but do not exhibit traits that allow them to survive fire when young, representing a different strategy for survival in frequently burned communities. & Context Fire is an important driver in the distribution and abundance of southern US pine species, and seedling fire tolerance often determines individual survival under frequent fire regimes.

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Purpose Biochars are carbon-rich products derived from biomass through pyrolysis, and are useful for soil fertility enhancement and carbon sequestration. Most agricultural and forestry residues could be used for biochars production. In this study, biochars were produced from rice straw, bamboo culm, and reed straw under different pyrolysis temperatures. The physiochemical and morphological properties, and PAHs content of biochars were investigated for determining the effect of protective gas and pyrolysis temperatures on biochars under different pyrolysis processes. Method Rice straw, bamboo culm (8 years old), and giant reed straw were used in this study. These three organic materials were converted into biochars by slow pyrolysis using a lab-scale fixed bed pyrolysis reactor. Treatment temperatures of slow pyrolysis were 400, 500, 600 and 700°C with or without the application of high purity nitrogen ([99.999 %) as the protective gas. Results We found that the high-temperature pyrolysis produced lower biochar yield (25.84-28.84 %) than the low-temperature pyrolysis (29.44-34.4 %). However, the BET and C content of biochar under the high-temperature pyrolysis process was higher. The low H/C and O/C ratios of the biochars produced at higher temperature pyrolysis, was 0.08-0.10, 0.01-0.22, respectively, which showed that the carbon in these biochars was unsaturated. The PAHs content decreased with increasing pyrolysis temperature. Bamboo culms pyrolysed at 700°C had the lowest concentration of P 16 PAH (10.06 lg kg -1 ). Conclusion The pyrolysis temperature significantly affected the properties of the resultant biochars (P \ 0.05) while the protective gas did not (P [ 0.05).