Seedling Uptake and Fate of Soil-applied Capsaicin, a Potential Browse Deterrent

Seedling damage due to browse constitutes a major challenge to afforestation and reforestation efforts in the Central Hardwood Forest region of the USA. Many efforts have been made to deter herbivores, but the costs, implementation methods, and relative ineffectiveness of existing mitigation options often preclude operational implementation. An alternate means of deterring wildlife browse is capsaicin, a hot pepper concentrate, which has been reported to decrease herbivory of tree seedlings and is available in a controlled-release form designed to act systemically following application to the soil and subsequent plant uptake. However, the degree to which seedlings are capable of absorbing capsaicin from the soil solution and the location of absorbed capsaicin within the plant remain largely unexamined. A greenhouse experiment was conducted to determine the potential absorption of soil-applied capsaicin in post-transplant northern red oak (Quercus rubra L.) seedlings in conjunction with a growth chamber study investigating the fate of capsaicin in the soil. In the first experiment, each seedling received the recommended dose of 0.03g of soil-applied capsaicin, was separated into roots, leaves, and stems at three and five weeks after capsaicin application, and was analyzed using QQQ-LC/MS. No capsaicin or capsaicinoids were found in any of the tissues. Capsaicin was quantified in the soil, leachates, and ambient air using QQQ-LC/MS in a related experiment with the same growing conditions and capsaicin application rate. These results reflect observed efficacy of capsaicin in the field, and the implications of this study should be considered when evaluating animal browse mitigation measures

Simulated predation of Quercus variabilis acorns impairs nutrient remobilization and seedling performance irrespective of soil fertility

Background and aims Predators may partially orcompletely consume Quercus spp. acorns, but effectson nutrient remobilization and seedling performance arepoorly understood. We investigated interactions betweensoil fertility and the removal of Quercus variabilisacorn cotyledons at different early developmental stageson seedling nutrition and development.Methods Seedlings were grown in two soils of contrastingfertility and the kinetics of acorn nitrogen, phosphorusand potassium remobilization, and seedling survival,growth and nutrient content were analyzed.Results Acorn mass and macronutrients decreased remarkably<2 weeks after emergence, with nitrogen andphosphorus remobilizing faster than potassium. Acornremoval at or 1 week after emergence inhibited seedlingsurvival, growth and fine root formation, whereas removalfrom 2 to 10 weeks after emergence had minor effects. Acorn macronutrient remobilization and effects of acorn removal on seedling performance were not reversed under high soil fertility. When acorns were removed &#8805; 2 weeks after emergence, fertilization increased root surface and seedling nitrogen content. Conclusions. Acorn nutrients are more important than soil nutrients during very early seedling development. Cotyledon damage at emergence impairs seedling performance despite no direct damage to the remainder of the seedling. This effect cannot be reverted by high soil fertility and has potential ecological and practical implications for oak regeneration.National Natural Science Foundation of ChinaComunidad de Madri

The role of stored carbohydrates and nitrogen in the growth and stress tolerance of planted forest trees

Plants store compounds that supplement external resources to maintain primaryfunctions. We reviewed the role of stored non-structural carbohydrates (NSC) and nitrogen(N) in juvenile woody species for spring growth and cold and drought stress tolerance,which are crucial processes for early performance of forest plantations. Plant functionaltypes differed in NSC and N partitioning and allocation to new growth. In general,however, new leaves/shoots were more enriched in remobilized resources than new fineroots. Conifers used less remobilized resources than broadleaf species for fine root growth.New shoots/leaves were mostly comprised of remobilized N ([60 %) in conifers andbroadleaf deciduous species, while broadleaf evergreens relied more on soil N (\50 %remobilized N). In contrast, few differences among functional groups existed in the contributionof remobilized carbon (C) to new leaves/shoots, which comprised 28&-45 % ofstored C reflecting the importance of current photosynthesis and distinctions in C and N remobilization physiology. Organ source strength for remobilized N was positively related to its contribution to seedling N content. However, leaves are priority N sources in evergreens, which remobilized more N than predicted by their contribution to seedling N content. In contrast, roots in broadleaf evergreens and conifers were poor contributors of remobilized N. Under low stress, spring growth has little effect on NSC reserves. However, prolonged and intense photosynthesis depression strongly reduces NSC. In contrast, N reserves usually decline after planting and their replenishment takes longer than for NSC reserves. Strong storage reduction can hinder seedling stress acclimation and survival capacity. Accumulation of stored resources can be promoted in the nursery by arresting plant growth and supplying resources at a higher rate than seedling growth and maintenance rate. We conclude that the way in which woody plants manage stored resources drives their growth and stress tolerance. However, plant functional types differ in storage physiology, which should be considered in silvicultural managementMinisterio de Ciencia e InnovaciónComunidad de MadridUniversidad de Alcal

An exponential fertilization dose–response model to promote restoration of the Mediterranean oak Quercus ilex

Nursery nitrogen (N) fertilization influences seedling N reserves, morphology, photosynthesis rate and stress tolerance and frequently enhances outplanting performance. Although mineral nutrition is a critical aspect of seedling quality, fertility targets of Mediterranean sclerophylous species have not been thoroughly quantified. We sought to define those fertility targets for seedlings of Quercus ilex, a key species in Mediterranean areas. Nine fertility treatments, ranging from 0 to 200 mg N seedling-1 applied under an exponential regime were tested in a greenhouse dose response trial in which phosphorus (P) and potassium (K) were increased in the same proportion as N (15N:5P:15K). Height and diameter growth were measured weekly, and biomass and nutritional status were analyzed at the end of culture (24 week). Plant growth and nutritional response to increased fertilization followed a curvilinear pattern depicting phases that ranged from deficiency to luxury consumption. Seedling dry mass production was maximized at 125 mg N seedling-1 (sufficiency level). N content and concentration increased with fertilization, reaching a maximum at 200 mg N seedling-1 (luxury consumption). P and K concentrations peaked at 75 and 25 mg N, respectively, suggesting a dilution effect of these nutrients. Root volume increased linearly up to 100 mg N and declined thereafter. The sufficiency level for Q. ilex (125 mg of applied N seedling-1) is notably higher than for other Quercus species from other biomes but intermediate to other Mediterranean Quercus species. No toxicity was observed at the highest treatment rate (200 mg N) suggesting that increased exponential N rates along with greater P and K proportions than those used in our experiment may further maximize nutrient storage

The Photosynthetic Response of Northern Red Oak (Quercus rubra L.) and American Chestnut (Castanea dentata (Marsh.) Borkh) Under Varying Light Intensity and Weed Competition

Although widely distributed across Indiana and the United States Midwest, conifer plantations consist largely of non-native species that are of no value to the state’s forest products industry. This project’s goal is to develop science-based protocols and specific silvicultural prescriptions for successfully converting conifer plantations to higher value native hardwoods. Quantifying photosynthesis rate in a plant is an important tool to help us discern the best methods for implementing conifer conversion. Seedlings from two different native species, northern red oak (Quercus rubra L.) and American chestnut (Castanea dentata (Marsh.) Borkh), were distributed among three different silvicultural cutting treatments (control, thinning and clear cut). Inside each one, two distinct categories of herbaceous control treatments (weed control and no weed control) were installed. Using an AccuPAR LP-80 sensor, canopy PAR (photosynthetically active radiation) interception was measured. Photosynthetic capacity was assessed with a LICOR 6400-XT analyzer to evaluate efficiency in resource use (water, light, gas exchange) and productivity. Among the treatments, clear cut presented maximum PAR intensity, followed by thinning and control, respectively. Both American chestnut and northern red oak seedlings demonstrated the highest photosynthesis rate (Amax) under high light conditions (clear cut), though photosynthesis of chestnut was greater than that of northern red oak. No significant differences were found between species in the weeding treatment for photosynthesis. Results of this study will provide valuable silvicultural prescriptions to Non-Industrial Private Forest (NIPF) landowners, forestry professionals, as well as state and federal agencies in Indiana and other Midwestern states

Exploration of a rare population of Chinese chestnut in North America: stand dynamics, health and genetic relationships

With the transport of plants around the globe, exotic species can readily spread disease to their native relatives; however, they can also provide genetic resistance to those relatives through hybrid breeding programmes. American chestnut (Castanea dentata) was an abundant tree species in North America until its decimation by introduced chestnut blight. To restore chestnut in North America, efforts are ongoing to test putative blight-resistant hybrids of Castanea dentata and Chinese chestnut (Castanea mollissima), but little is known about the ecology of C. mollissima. In a forest in northeastern USA in which C. mollissima has become established, we explored questions of stand dynamics, health and genetic relationships of C. mollissima offspring to an adjacent parent orchard. We found that C. mollissima was adapted and randomly distributed among native species in this relatively young forest. The genetics of the C. mollissima population compared with its parents indicated little effect of selection pressure as each of the parent trees contributed at least one offspring. The ease with which this exotic species proliferated calls to question why C. mollissima is rare elsewhere in forests of North America. It is likely that a time window of low animal predation allowed seedlings to establish, and the shallow soil at this site limited the maximum forest canopy height, permitting the characteristically short-statured C. mollissima to avoid suppression. Our results indicate that because C. mollissima exhibited pioneer species characteristics, hybrids between C. mollissima and C. dentata have the potential to be successful pioneer species of future forests in North America, and we challenge the paradigm that exotic tree species are wholly detrimental to native biodiversity. We contend that exotic tree species should be assessed not only by their level of threat to native species, but also by their potential positive impacts on ecosystems via hybrid breeding programmes

Vegetative and Adaptive Traits Predict Different Outcomes for Restoration Using Hybrids

Hybridization has been implicated as a driver of speciation, extinction, and invasiveness, but can also provide resistant breeding stock following epidemics. However, evaluating the appropriateness of hybrids for use in restoration programs is difficult. Past the F1 generation, the proportion of a progenitor’s genome can vary widely, as can the combinations of parental genomes. Detailed genetic analysis can reveal this information, but cannot expose phenotypic alterations due to heterosis, transgressive traits, or changes in metabolism or development. In addition, because evolution is often driven by extreme individuals, decisions based on phenotypic averages of hybrid classes may have unintended results. We demonstrate a strategy to evaluate hybrids for use in restoration by visualizing hybrid phenotypes across selected groups of traits relative to both progenitor species. Specifically, we used discriminant analysis to differentiate among butternut (Juglans cinerea L.), black walnut (J. nigra L.), and Japanese walnut (J. ailantifolia Carr. var. cordiformis) using vegetative characters and then with functional adaptive traits associated with seedling performance. When projected onto the progenitor trait space, naturally occurring hybrids (J. × bixbyi Rehd.) between butternut and Japanese walnut showed introgression toward Japanese walnut at vegetative characters but exhibited a hybrid swarm at functional traits. Both results indicate that hybrids have morphological and ecological phenotypes that distinguish them from butternut, demonstrating a lack of ecological equivalency that should not be carried into restoration breeding efforts. Despite these discrepancies, some hybrids were projected into the space occupied by butternut seedlings’ 95% confidence ellipse, signifying that some hybrids were similar at the measured traits. Determining how to consistently identify these individuals is imperative for future breeding and species restoration efforts involving hybrids. Discriminant analysis provides a useful technique to visualize past selection mechanisms and current variation in hybrid populations, especially when key ecological traits that distinguish progenitors are unknown. Furthermore, discriminant analysis affords a tool to assess ecological equivalency of hybrid populations and breeding program efforts to select for certain traits and monitor the amount of variability of those traits, relative to progenitors

Consequences of Shifts in Abundance and Distribution of American Chestnut for Restoration of a Foundation Forest Tree

Restoration of foundation species, such as the American chestnut (Castanea dentata) that was devastated by an introduced fungus, can restore ecosystem function. Understanding both the current distribution as well as biogeographic patterns is important for restoration planning. We used United States Department of Agriculture Forest Service Forest Inventory and Analysis data to quantify the current density and distribution of C. dentata. We then review the literature concerning biogeographic patterns in C. dentata. Currently, 431 ± 30.2 million stems remain. The vast majority (360 ± 22 million) are sprouts \u3c 2.5 cm dbh. Although this number is approximately 10% of the estimated pre-blight population, blight has caused a major shift in the size structure. The current-day population has a larger range, particularly west and north, likely due to human translocation. While climate change could facilitate northward expansion, limited seed reproduction makes this unlikely without assisted migration. Previous research demonstrates that the current, smaller population contains slightly higher genetic diversity than expected, although little information exists on biogeographic patterns in the genetics of adaptive traits. Our research provides a baseline characterization of the contemporary population of C. dentata, to enable monitoring stem densities and range limits to support restoration efforts

A conceptual framework for restoration of threatened plants: the effective model of American chestnut (Castanea dentata) reintroduction

We propose a conceptual framework for restoration of threatened plant species that encourages integration of technological, ecological, and social spheres. A sphere encompasses ideas relevant to restoration and the people working within similar areas of influence or expertise. Increased capacity within a sphere and a higher degree of coalescing among spheres predict a greater probability of successful restoration. We illustrate this with Castanea dentata, a foundation forest tree in North America that was annihilated by an introduced pathogen; the species is a model that effectively merges biotechnology, reintroduction biology, and restoration ecology. Because of C. dentata\u27s ecological and social importance, scientists have aggressively pursued blight resistance through various approaches. We summarize recent advancements in tree breeding and biotechnology that have emerged from C. dentata research, and describe their potential to bring new tools to bear on socio-ecological restoration problems. Successful reintroduction of C. dentata will also depend upon an enhanced understanding of its ecology within contemporary forests. We identify a critical need for a deeper understanding of societal influences that may affect setting and achieving realistic restoration goals. Castanea dentata may serve as an important model to inform reintroduction of threatened plant species in general and foundation forest trees in particular

Species ecology determines the role of nitrogen nutrition on the frost tolerance of pine seedlings

Frost determines the evolution and distribution of plants in temperate and cold regions. Several environmental factors can influencefrost acclimation of woody plants but the magnitude and direction of the effect of nitrogen (N) availability is controversial.We studied the effect of N availability on root and shoot frost tolerance in mid-fall and in winter in seedlings of four pines of contrastingecology: Pinus nigra J.F. Arnold, P. pinaster Ait., P. pinea L. and P. halepensis Mill.. Organ N and soluble sugar concentration,and timing of cessation of shoot elongation were measured to assess the physiological mechanisms underlying frostacclimation. Nitrogen was supplied at high and low rates only during the pre-hardening period and at a moderate N rate duringhardening in the fall. Shoot frost tolerance increased over winter while root frost tolerance did not change in any species. PrehardeningN availability affected the frost tolerance of both roots and shoots, although the effect was species-specific: high Nreduced the overall root and shoot frost tolerance in P. pinea and P. halepensis, and increased the frost tolerance in P. nigra, buthad no effect in P. pinaster. Nitrogen supply in the fall consistently increased frost tolerance in all speciesComunidad de Madri