Species in the genus Populus (poplars) have shown the potential to be utilized as short rotation woody crops for bioenergy production in the Southeast. A lack of knowledge on which poplar taxa perform best on marginal sites throughout the Southeast exists. Through measurement of relationships between growth metrics, water usage and physiological parameters of 2400 poplar trees, I was able to assess: 1) early rotation suitability of numerous poplar varietals to be grown as bioenergy feedstocks in northeast Mississippi, and 2) the effectiveness of early rotation physiological parameters in predicting future productivity and water usage. Overall findings from this study suggest that trees with D x M parentage may be best fit for large-scale plantation growth in the Southeast. They demonstrated low mortality and collectively grew the tallest of all taxa. Early-rotation physiology demonstrated mixed results in predicting future growth and water usage. Findings from this study will be used in future bioenergy feedstock selection.

This study aimed at developing allometric equations for the estimation of aboveground biomass of black willow and eastern cottonwood and determine biomass production by these species under several planting spacing and harvest frequency combinations. Logarithmic model with dbh and tree height was the best fitting model for individual tree aboveground biomass estimation of both species. At area level, logarithmic models with stand age, dominant height, and planting density produced the best results. Mixed-effects modeling showed statistically significant effects of harvest frequency for eastern cottonwood but not for black willow. Overall, we conclude that, biomass production of black willow and eastern cottonwood would play a critical role in the fulfillment of the wood energy demands and biomass yields can be enhanced by considering management factors during plantation. These findings will be useful to forest owners in Lower Mississippi Alluvial Valley for estimating biomass without destructive sampling and have optimal biomass production.

Climate change poses a significant threat to bioenergy production, impacting plant’s phenology and physiological performance. Investigating the adaptation of bioenergy crops like Populus is crucial for sustaining production. Populus, known for its genetic variation and ease of study, offers insights into tree responses to climate change. My research, part of the Advancing Populus Pathways in the Southeast (APPS) project, focuses on various Populus genotypes across multiple growing seasons, exploring phenology under different management strategies. Planting Populus across two sites, namely Monroe and Pontotoc, allows for the examination of genotype responses to climate change factors, particularly in terms of phenology and productivity. Factors like parentage provenance and temperature fluctuations influence budburst timing. Additionally, management practices, such as coppicing, significantly affect budburst, with coppiced trees showing delayed timing (five to ten days) compared to non-coppiced ones. Cold spell damage during budbreak reveals vulnerability, with northern provenances exhibiting greater resilience. Understanding such events is vital for tailored management. Cold spells not only impact initial budbreak but also alter leaf phenology and canopy dynamics, affecting overall productivity. Genotypes exhibit varied responses to rising temperatures and CO2 levels, influenced by their parentage. Trees with northern provenance, for instance, display higher photosynthetic capacity, but may face thermal stress under certain temperature increases. Conversely, southern genotypes demonstrate moderate photosynthetic capacity, but showcase better adaptation to heat, offering potential for breeding resilient varieties. Leaf traits serve as proxies for biomass production and water use efficiency prediction, aiding in genotype screening. Mechanisms like self-shading and leaf movability influence responses to environmental changes. For instance, self-shading helps regulate leaf temperature, thereby enhancing photosynthetic performance, albeit with some trade-offs. Elevated CO2 levels enhance water use efficiency, but determining whole-tree water use efficiency requires integration of various methods. While leaf-level measurements correlate with whole-tree water use efficiency, an integrated approach, combining leaf-level gas exchange and isotopic measurements, shows promise. In conclusion, understanding Populus responses to climate change is crucial for sustainable bioenergy production in the southeastern United States. Insights into phenology, productivity, and adaptation mechanisms offer avenues for management and breeding strategies, ensuring resilience amidst shifting climates.

[ES] Los encargados de diseñar políticas, los trabajadores y los habitantes rurales deben ser conscientes de la relevancia de la erosión del suelo como un proceso irreversible de degradación de la tierra. Esto es clave para lograr la neutralidad en la degradación de la tierra y lograr la sostenibilidad para la humanidad y los ecosistemas naturales. Especialmente, las áreas agrícolas se ven afectadas por la erosión del suelo que amenaza la calidad del suelo y, posteriormente, la seguridad alimentaria. Por tanto, es necesario el desarrollo de nuevas técnicas atractivas visualmente, de fácil manejo y eficientes en la divulgación de los resultados. ISUM (Improve Stock Unearthing Method) es un procedimiento contrastado para estimar y cartografiar las tasas de movilización del suelo y los procesos de erosión. Para lograr este objetivo, el uso del injerto como biomarcador realizando mediciones topográficas in situ (cada 10 cm) a lo largo de transectos perpendiculares permite: i) explicar los factores de la activación de los procesos de erosión del suelo como la labranza, la edad de la plantación, material parental o posición en laderas; ii) complementar otros métodos bien contrastados como la RUSLE (Revised Universal Soil Loss Equation), IC (Índice de conectividad) o parcelas de erosión; y, iii) detectar áreas críticas afectadas por el agotamiento, acumulación o movilización del suelo. En esta tesis doctoral, se pretende mostrar cómo se ha desarrollado una nueva mejora de este método en diferentes cultivos (viñedos, cítricos, caquis, etc.), bajo diferentes condiciones ambientales (roca madre, edades de la planta, manejo del suelo o pendiente) con diversos procedimientos geomáticos (métodos de interpolación y análisis geoestadístico, mediciones y modelos topográficos) mediante técnicas SIG. Los resultados pretenden demostrar la utilidad de un método fácil de aprender, rápido de aplicar y de bajo coste para ser aplicado en diferentes tipos de cultivos injertados y ser una referencia a escala mundial para estudios comparados, por ejemplo, dentro de la geografía de los suelos, la agronomía o la ingeniería geomática. / [CA] Els encarregats de dissenyar polítiques, els treballadors i els habitants rurals han de ser conscients de la rellevància de l'erosió del sòl com a procés irreversible de degradació de la terra. Això és clau per assolir la neutralitat en la degradació de la terra i assolir la sostenibilitat per a la humanitat i els ecosistemes naturals. Especialment, les àrees agrícoles es veuen afectades per l'erosió del sòl que amenaça la qualitat del sòl i, posteriorment, la seguretat alimentària. Per tant, cal el desenvolupament de noves tècniques atractives visualment, de fàcil maneig i eficients en la divulgació dels resultats. ISUM (Improve Stock Unearthing Method) és un procediment contrastat per estimar i cartografiar les taxes de mobilització del sòl i els processos d'erosió. Per assolir aquest objectiu, l'ús de l'empelt com a biomarcador realitzant mesuraments topogràfics in situ (cada 10 cm) al llarg de transectes perpendiculars permet: i) explicar els factors de l'activació dels processos d'erosió del sòl com el cultiu, l'edat de la plantació, material parental o posició en vessants; ii) complementar altres mètodes ben contrastats com la RUSLE (Revised Universal Soil Loss Equation), IC (Índex de connectivitat) o parcel·les d'erosió; i, iii) detectar àrees crítiques afectades per l'esgotament, l'acumulació o la mobilització del sòl. En aquesta tesi doctoral, es pretén mostrar com s'ha desenvolupat una nova millora d'aquest mètode en diferents cultius (vinyes, cítrics, caquis, etc) sota diferents condicions ambientals (roca mare, edats de la planta, maneig del sòl o pendent) amb diversos procediments geomàtics (mètodes d'interpolació i anàlisi geoestadístic, mesuraments i models topogràfics) mitjançant tècniques SIG. Els resultats pretenen demostrar la utilitat d'un mètode fàcil d'aprendre, ràpid d'aplicar i de baix cost per ser aplicat a diferents tipus de cultius empeltats i ser una referència a nivell mundial per a estudis comparats, per exemple, dins la geografia dels sòls , l'agronomia o l'enginyeria geomàtica. / [EN] Policy makers, farmers and rural stakeholders need to be aware of the relevance of soil erosion as an irreversible process of land degradation. This is key to achieving land degradation neutrality and sustainability for the humankind and natural ecosystems. Especially agricultural areas are affected by soil erosion which threatens soil quality and subsequently food security. Therefore, it is necessary to develop new techniques that are visually attractive, easy to use and efficient in disseminating the results. ISUM (Improve Stock Unearthing Method) is a proven procedure for estimating and mapping soil mobilization rates and erosion processes. To achieve this goal, the use of the graft as a biomarker by performing in situ topographic measurements (every 10 cm) along perpendicular transects allows: i) to explain the factors that activate soil erosion processes such as tillage, age of the plantation, parent material or position on slopes; ii) complement other well-proven methods such as RUSLE (Revised Universal Soil Loss Equation), CI (Connectivity Index) or erosion plots; and, iii) detect critical areas affected by the depletion, accumulation or mobilization of the soil. In this doctoral thesis, it is intended to show how a new improvement of this method has been developed in different crops (vineyards, citrus, persimmons, etc.), under different environmental conditions (parent rock, plant ages, soil management or slope) with various geomatic procedures (interpolation methods and geostatistical analysis, measurements and topographic models) using GIS techniques. The results aim to demonstrate the usefulness of an easy-to-learn, fast-to-apply and low-cost method to be applied to different types of grafted crops and to be a worldwide reference for comparative studies, for example, within the soil geography, agronomy or geomatics engineering. / Rodrigo Comino, J. (2023). El método mejorado del tocón (isum) para evaluar procesos de erosión del suelo en plantas injertadas utilizando medidas topográficas in situ [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/191874