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Using Planetscope imagery, we trained a random forest model to detect Callery pear (Pyrus calleryana) throughout a diverse urban landscape in Columbia, Missouri. The random forest model had a classification accuracy of 89.78%, a recall score of 0.693, and an F1 score of 0.819. The key hyperparameters for model tuning were the cutoff and class–weight parameters. After the distribution of Callery pear was predicted throughout the landscape, we analyzed the distribution pattern of the predictions using Ripley’s K and then associated the distribution patterns with various socio-economic indicators. The analysis identified significant relationships between the distribution of the predicted Callery pear and population density, median household income, median year the housing infrastructure was built, and median housing value at a variety of spatial scales. The findings from this study provide a much-needed method for detecting species of interest in a heterogenous landscape that is both low cost and does not require specialized hardware or software like some alternative deep learning methods.

AimsNitrogen (N) enrichment from excessive fertilization influences the coupling of nutrients in terrestrial ecosystems, but whether it could alter the scaling relationships between multinutrients [including macronutrients: N, phosphorus (P), potassium, calcium (Ca), magnesium (Mg) and micronutrients: manganese (Mn), iron (Fe) and zinc] remains unclear.MethodsWe conducted an control experiment using two-year-old Chinese hickory (Carya cathayensis) saplings in hydroponics system, with six levels of N fertilization, to evaluate variations in scaling relationships of multinutrient concentrations in vegetative organs of Chinese hickory under consistent N fertilization.ResultsCorrelational relationships between multinutrients concentrations were most significant in leaves, while stems and roots were less related. Micronutrients, in particular, were mostly negatively related to macronutrients. Significant allometric relationships were detected among multinutrients, but the response patterns were both organ- and nutrient-dependent. For example, positive allometric relationships were detected in N versus other macronutrients while negative allometric relationships were observed with N related to micronutrient response. Leaves generally presented more positive allometric relationships than negative relationships. Beyond expectation, increasing N fertilization minimally altered the scaling exponents between multinutrients, except stem N-Mg, root Mn-Fe, root P-Ca, and leaf P-Ca.ConclusionsChinese hickory saplings displayed relatively high nutrient homeostasis when excessive N fertilizer was applied. These results will enhance our understanding of organ-dependent allometric relationships between multinutrients in forest trees and may offer new insights into how plants develop adaptive functional traits to increasing N fertilization.

Background Frequent low-intensity fires historically shaped forest composition and structure in the southeastern United States of America (USA). However, in modern times, fire suppression has inadvertently facilitated the recruitment of mesophytic trees and potentially the invasion of non-native woody plants. In this study, we selected twelve woody broadleaved plants from forested areas of South Carolina and categorized them into three groups: (1) non-native invasive species, (2) native pyrophytic species, and (3) native mesophytic species. We used these categories to examine bark thickness—one critical determinant of fire tolerance—across a spectrum of stem sizes (16.3 mm < DBH < 69.4 mm). Results Across all species, pyrophytic species consistently exhibited the thickest bark at all measurement heights, followed by invasive species, while mesophytic species had the thinnest bark. Invasive and mesophytic species displayed similar absolute and relative bark thickness values and demonstrated comparable trends in bark thickness variation with increasing stem size. Absolute bark thickness decreased with increasing height along the stem in all groups; however, pyrophytic species exhibited a more pronounced decline in bark thickness from the ground line to breast height compared to mesophytic and invasive species. For pyrophytic species, relative bark thickness at the ground line decreased sharply with increasing stem diameter, indicating a significant early-life investment in bark development. Conclusions The congruence in absolute and relative bark thickness patterns between mesophytic and woody invasive plants along both horizontal (DBH) and vertical (height) gradients indicates that fire suppression may have helped to facilitate invasive species establishment and spread and that the restoration of historical fire regimes (e.g., repeated surface fire), suggested for reducing mesophytes, could aid in the management of woody invasive plants.

Chinese tallow is a non-native invasive tree expanding in range and abundance throughout the southern United States. Several biogeographical studies mapping tallow distribution and examining key underlying environmental factors relied on the U.S. Forest Service Forest Inventory and Analysis (FIA) data, representing forestlands at scales of ~2400 ha. However, given that most invasive trees, like tallow, are cosmopolitan and dynamic in nature, FIA data fails to capture the extent and severity of the invasion especially outside areas classified as forestlands. To develop tallow maps that more adequately depict its distribution at finer spatial scales and to capture observations in non-forestlands, we combined verified citizen science observations with FIA data. Further, we described spatiotemporal patterns and compared citizen science to FIA and other previously published distribution maps. From our work, although tallow is prevalent in the south, Louisiana, Texas, and Mississippi were the most invaded states. Tallow was associated with flatwoods and prairie grasslands of the Gulf Coast. Annual extreme minimum temperatures of less than −12.2 °C (10 °F) represented the northern limit of naturalized tallow populations. Tallow’s northward and inland expansion was captured in citizen science and FIA data, indicating a tallow spread rate ranging from 5 to 20 km annually over the last decade. Systematic sampling, such as FIA, and citizen science data both have their own unique pitfalls. However, the use of citizen science data can complement invasive plant distribution mapping, especially when combined with data from established systematic monitoring networks. This approach provides for a more complete understanding of invasive tree extent and spatiotemporal dynamics across large landscapes.

Longleaf pine (Pinus palustris Mill.) savannas and woodlands are known for providing numerous ecosystem services such as promoting biodiversity, reducing risk of wildfire and insect outbreaks, and increasing water yields. In these open pine systems, there is also interest in managing carbon (C) in ways that do not diminish other ecosystem services. Additionally, there may be management strategies for accomplishing these same objectives in plantations and degraded stands that developed from natural regeneration. For example, C accumulation in live trees and C storage in harvested wood products could be increased by extending rotations and converting plantations to multi-aged stands. Belowground C storage could be enhanced by incorporating pyrogenic C into the mineral soil before planting longleaf pines in clearcut areas, but this may be contrary to findings that indicate that minimizing soil disturbance is important for long-term soil C storage. We suggest examining approaches to reduce total ecosystem C emissions that include using targeted browsing or grazing with domesticated livestock to supplement prescribed burning, thereby reducing C emissions from burning. The mastication of woody vegetation followed by a program of frequent prescribed burning could be used to reduce the risk of substantial C emissions from wildfires and to restore function to savannas and woodlands with hardwood encroachment and altered fire regimes. Many of these approaches need to be validated with field studies or model simulations. There is also a need to improve the estimates of dead wood C stocks and C storage in harvested wood products. Finally, eddy covariance techniques have improved our understanding of how disturbances influence longleaf pine C dynamics over multiple time scales. However, there is a need to determine the degree to which different silvicultural approaches, especially those for adapting ecosystems to climate change, influence C accumulation. Overall, our review suggests that there are numerous opportunities for research on C dynamics in longleaf pine ecosystems, and these systems are likely well-positioned to accomplish C objectives while offering other ecosystem services.

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.

Abstract Species ranges are expected to move northward with climate warming. However, species will likely encounter soil conditions that differ from their historic ranges. Black (Quercus velutina) and chestnut (Q. montana) oaks are expected to do well in climates that are hotter and drier, but it is unknown as to how they respond to soils of different geological histories. At a glaciated and nonglaciated site in northwestern Pennsylvania, we compared the growth, biomass allocation, and mycorrhizal association for black and chestnut oak seedlings at two different levels of light. On nutrient-poor, nonglaciated soils at high light levels, both species had greater growth and biomass accumulation than on nutrient-rich, glaciated soils. However, at low light levels, these responses were greatest on glaciated soils, especially for chestnut oak. Although mycorrhizal association was beneficial on nonglaciated soil at high light levels, low light levels were associated with reduced growth when compared to glaciated soils. In low light and nutrient-poor soils, mycorrhizal association may result in a carbon sink with lower net photosynthesis, as carbon for plant growth is, instead, allocated to the mycorrhizae symbiont. Variable species response to soil types indicates reduced performance for black and chestnut oak seedlings on high-quality glaciated soils especially in high light environments.

Biological invasions by woody species in forested ecosystems can have significant impacts on forest management and conservation. We designed and tested several management options based on the physiology of Chinese tallow (Triadica sebifera [L.] Small). Specifically, we tested four treatments, including mastication, foliar herbicide, and fire (MHfolF), mastication and foliar herbicide (MHfol), dormant-stem herbicide and fire (HdorF), and dormant-stem herbicide (Hdor), to determine their efficacy in reducing the density and regeneration of this highly invasive tree species. Mastication treatments were significant in reducing density the first year but not after 3 years. Prescribed fire significantly reduced density combined with previous treatments. Regeneration coverage was highest on those sites with mastication, which was not affected by the addition of prescribed fire. Overall, we found that the most comprehensive treatment (MHfolF) was more effective in reducing density but did not result in a difference in the amount of regeneration after treatment. Management and Policy Implications Chinese tallow is a highly invasive tree species in the southeastern coastal plain, USA. Chinese tallow invasions can displace native species, potentially having substantial economic impacts on timber resources and desirable forest diversity. Attempts to manage and control Chinese tallow with single treatments are often only temporarily effective because of its ability to regenerate from a persistent seed bank and by root and stump sprouting. In this study, we developed and tested a multiple-treatment regime using mastication and herbicide treatments followed by prescribed burning to reestablish this important ecological process. Individual treatments were timed and sequenced to reduce Chinese tallow densities when they were physiologically most susceptible to further limit their regrowth and new seedling establishment. Long-term control will require additional burning or treatments before seedlings escape to larger size classes. Therefore, effective management of Chinese tallow requires a forward-thinking, integrated approach that aims not only to reduce or exclude the invader but also to restore the affected community by building resistance to future invasion. Furthermore, in the selection of invasive species management practices, the prevention of future invasion must be considered because management actions themselves are disturbance events and many invasive species thrive in disturbed environments.

Background Ecosystem management, community restoration, and managing for climate resilience have become major priorities of land management in recent decades. For woodlands and savannas (i.e., “open forests”), this transition has meant moving fire-deprived, closed-canopy forests to structures and compositions characteristic of natural communities that are rare today: open-grown, wide-spreading trees, and endemic flora and fauna associated with frequent, low to moderate intensity fires. Open forest restoration is complex; its approach and operational prescriptions are dependent on a multitude of factors. Reopening forests to achieve ecological objectives associated with open forests is hampered by site histories, novel species compositions, and structures that resist fire. Results Fire histories shed light on fire regimes that promote open forests, informing prescriptions at stand and landscape levels, but due to many social and environmental factors, managers are challenged to recreate those fire regimes. As fire was removed from these ecosystems, successional processes led to changes in species compositions concomitant with changes in woody structure and fuel complexes further inhibiting restoration without active management. As active management aims to transition residing fine fuels from mesophytic hardwood-shrub litter to herbaceous dominant fuels with canopy openness, fire effects, and prescriptions also change. Silvicultural prescriptions have been developed to aid in the process of transition but maintaining mature, continuous canopy open forests through the regeneration and recruitment phase of predominantly shade intolerant of oaks and pines remains speculative. Further, as a legacy of woody densification, contemporary fire practices may result in undesirable increases in sprouting woody species impacting objectives for herbaceous cover and diversity. Invasive plants and depauperate seed banks may further limit successful outcomes. Conclusions Even with these formidable challenges, transitioning closed forests to open structures and compositions is critically important for wildlife that depend on them, especially at the size, scale, and connectivity necessary to sustain their populations. Many birds and pollinators of conservation concern require open forests and early successional forests may not serve as surrogates for mature, open forest habitat. In this review, we outline the advances, challenges, and importance for reopening closed canopied forests to open forests in the central and midsouth, USA. Further, we set the stage for new approaches and learned outcomes from the papers of the 7th Fire in Eastern Oak Forests Conference in Tyler, TX, included in this special collection of Fire Ecology .

Backcross breeding programs have been used to transfer disease resistance and other traits from one forest tree species to another in order to meet restoration objectives. Evaluating the field performance of such material is critical for determining the success of breeding programs. In eastern North America, The American Chestnut Foundation has a backcross breeding program that uses Chinese chestnut (Castanea mollissima Blume) to introduce resistance of the fungal pathogen chestnut blight [Cryphonectria parasitica (Murr.) Barr.] to the native American chestnut [Castanea dentata (Marsh.) Borkh.]. We compared physiological and morphological characteristics among seedlings of American chestnut, Chinese chestnut, and BC₁F₃, BC₂F₃, and BC₃F₃ hybrid chestnuts during their fourth growing season after field-planting. American chestnut and the BC₃F₃ breeding generation displayed photosynthetic light-response curves that were similar to each other but different from Chinese chestnut. Rates of photosynthesis were higher for American chestnut and the BC₃F₃ breeding generation when compared to Chinese chestnut for light levels ≥800 μmol m⁻² s⁻¹ photosynthetic photon flux density and for maximum photosynthetic capacity. Leaf morphology variables were not different between American chestnut and any of the breeding generations, but leaf area (on a per leaf basis) of Chinese chestnut was lower than that of any other chestnut type. Our results suggest that backcross breeding can be used to transfer desirable traits for restoration of native species threatened by non-native pathogens.