Cerne e alburno em eucaliptos: influência da espécie e da idade nas propriedades tecnológicas

Pós-graduação em Ciência Florestal - FCA

Effects of irrigation on water use and water use efficiency in two fast growing Eucalyptus plantations

Eucalyptus plantations occupy almost 20 million ha worldwide and exceed 3.7 million ha in Brazil alone. Improved genetics and silviculture have led to as much as a three-fold increase in productivity in Eucalyptus plantations in Brazil and the large land area occupied by these highly productive ecosystems raises concern over their effect on local water supplies. As part of the Brazil Potential Productivity Project, we measured water use of Eucalyptus grandis x urophylla clones in rainfed and irrigated stands in two plantations differing in productivity. The Aracruz (lower productivity) site is located in the state of Espirito Santo and the Veracel (higher productivity) site in Bahia state. At each plantation, we measured stand water use using homemade sap flow sensors and a calibration curve using the clones and probes we utilized in the study. We also quantified changes in growth, leaf area and water use efficiency (the amount of wood produced per unit of water transpired). Measurements were conducted for 1 year during 2005 at Aracruz and from August through December 2005 at Veracel. Transpiration at both sites was high compared to other studies but annual estimates at Aracruz for the rainfed treatment compared well with a process model calibrated for the Aracruz site (within 10%). Annual water use at Aracruz was 1394 mm in rainfed treatments versus 1779 mm in irrigated treatments and accounted for approximately 67% and 58% of annual precipitation and irrigation inputs respectively. Increased water use in the irrigated stands at Aracruz was associated with higher sapwood area, leaf area index and transpiration per unit leaf area but there was no difference in the response of canopy conductance with air saturation deficit between treatments. Water use efficiency at the Aracruz site was also not influenced by irrigation and was similar to the rainfed treatment. During the period of overlapping measurements, the response to irrigation treatments at the more productive Veracel site was similar to Aracruz. Stand water use at the Veracel site totaled 975 mm and 1102 mm in rainfed and irrigated treatments during the 5-month measurement period respectively. Irrigated stands at Veracel also had higher leaf area with no difference in the response of canopy conductance with air saturation deficit between treatments. Water use efficiency was also unaffected by irrigation at Veracel. Results from this and other studies suggest that improved resource availability does not negatively impact water use efficiency but increased productivity of these plantations is associated with higher water use and should be given consideration during plantation management decision making processes aimed at increasing productivity. Published by Elsevier B.V.

WOOD NATURAL RESISTANCE OF SEVEN FOREST SPECIES TO WHITE ROT CAUSED BY Pycnoporus sanguineus

This research evaluated the natural resistance of Platanus x acerifolia, Luehea divaricate, Carya illinoinensis, Peltophorum dubium, Araucaria angustifolia, Eucalyptus grandis and Hovenia dulcis, to accelerated decay of the white-rot fungus Pycnoporus sanguineus. The Specific Density at 12% was determinated. The accelerated decay test was conducted with glass bottles (capacity of 500 mL) filled with 100 g of moist soil, autoclaved, and kept at 25 degrees C. The initial establishment of fungal colonies on plates was supported by samples of Pinus elliottii sapwood. In this study, three samples of dimensions 9.0 x 25.0 x 25.0 mm were used for each species evaluated and, after 16 weeks of incubation, the percentage loss of mass was calculated. The degree of natural resistance was performed according to the percentages of mass loss. The results obtained from weight loss were compared by Tukey test at 5%. The natural resistance of woods was not influenced by specific gravity The wood of Carya illinoinensis, Eucalyptus grandis, Platanus x acerifolia, Luehea divaricata and Peltophorum dubium were classified as very resistant, Houvenia dulcis as resistant and Araucaria angustifolia as moderate resistant.

Unearthing the roots of degradation of Quercus pyrenaica coppices: A root-to-shoot imbalance caused by historical management?

Slow growth, branch dieback and scarce acorn yield are visible symptoms of decay in abandoned Quercus pyrenaica coppices. A hypothetical root-to-shoot (R:S) imbalance provoked by historical coppicing is investigated as the underlying driver of stand degradation. After stem genotyping, 12 stems belonging to two clones covering 81 and 16 m2 were harvested and excavated to measure above- and below-ground biomass and nonstructural carbohydrate (NSC) pools. To study root system functionality, root connections and root longevity were assessed by radiocarbon analysis. Seasonality of NSC was monitored on five additional clones. NSC pools, R:S biomass ratio and fine roots-to-foliage ratio were higher in the large clone, whose centennial root system, estimated to be 550 years old, maintained large amounts of sapwood (51.8%) for NSC storage. 248 root connections were observed within the large clone, whereas the small clone showed comparatively simpler root structure (26 connections). NSC concentrations were higher in spring (before bud burst) and autumn (before leaf fall), and lower in summer (after complete leaf expansion); they were always higher in roots than in stems or twigs. The persistence of massive and highly inter-connected root systems after coppicing may lead to increasing R:S biomass ratios and root NSC pools over time. We highlight the need of surveying belowground organs to understand aboveground dynamics of Q. pyrenaica, and suggest that enhanced belowground NSC storage and consumption reflect a trade-off between clonal vegetative resilience and aboveground performance.

Variation throughout the tree stem in the physical-mechanical properties of the wood of Abies alba Mill. from the Spanish Pyrenees

This study analyses the variation of main physical-mechanical properties of wood along the longitudinal and radial directions of the tree for Abies alba Mill. growing in the Spanish Pyrenees. Small clear specimens were used to study the properties of volumetric shrinkage (VS), density (?), hardness (H), bending strength (MOR), modulus of elasticity (MOE), maximum compressive strength parallel to the grain (MCS) and impact strength (K). Several models of properties variation in the longitudinal and radial directions were analyzed. Main trends of variation of properties throughout the tree stem were identified although none of them could be fitted to predictive statistical models. Along the longitudinal direction, the properties studied followed a downward trend from the base to the crown, which was not significant in all cases, indicating that no differences in quality existed. Throughout the radial direction the trend is upward for the first 40-50 growth rings, after which it slopes downwards, more gently at first until rings 70-75 and then more steeply. This behaviour is related to variation in wood structure from the pith to the bark, depending on whether the wood is juvenile, sapwood or heartwood, and to wood maturity and microfibril angle. Authors encourage carrying further studies on other populations of A. alba in the Spanish Pyrenees to check if the trends found in this study apply to other provenances.

Unearthing the roots of degradation of Quercus pyrenaica coppices: an integrative perspective from clonal structure to carbon budgets

Quercus pyrenaica es una especie rebrotadora de raíz intensa e históricamente aprovechada en monte bajo para la obtención de leñas, carbón y pastos. Debido al éxodo rural y a la aparición de nuevas fuentes energéticas, este aprovechamiento fue abandonado en la década de 1970. Desde entonces, las bajas producciones de madera y bellota y el puntisecado de los pies evidencian el generalizado estancamiento de estas masas. Uno de los mayores retos actuales de la selvicultura en el ámbito mediterráneo es encontrar usos alternativos para estos montes abandonados, siendo la conversión a monte alto una de las alternativas preferidas. Se han realizado resalveos de conversión, sin embrago, éstos se aplican sin un conocimiento integral de las causas de la degradación. En esta tesis doctoral, estudiamos un hipotético desequilibrio entre la parte radical y la parte aérea (R:S) de las cepas de rebollo como causa subyacente de su decaimiento. En una parcela experimental, aprovechada al menos desde el siglo XII, se realizaron análisis genéticos a priori para elucidar la estructura genética del rodal, y así estudiar la influencia del tamaño clonal en el funcionamiento de las cepas. Las cepas de mayor tamaño presentaron un menor crecimiento diametral de sus pies, así como mayores tasas de respiración radical, estimadas a partir de flujos internos de CO2 a través del xilema (FT) y de los flujos de CO2 del suelo. Estos resultados sugieren que el desequilibrio R:S aumenta con el tamaño clonal, dado que la eliminación periódica de órganos aéreos, al mismo tiempo que las raíces permanecen intactas, da lugar a un gran desarrollo del sistema radical que consume gran parte de los carbohidratos no estructurales (NSC) en respiración de mantenimiento, comprometiendo así el desarrollo de órganos aéreos. Se excavaron y pesaron dos cepas compuestas por cuatro y ocho pies, las cuales mostraron ratios R:S (0.5 y 1, respectivamente) superiores a los registrados en pies de origen sexual. Al igual que en otras especies rebrotadoras de raíz, se observaron altas concentraciones de NSC en las raíces (> 20% en primavera) y una gran proporción de albura en el sistema radical (52%) que alberga una notable reserva de NSC (87 kg en la cepa de mayor tamaño). En el sistema radical de dicha cepa, estimada mediante dataciones radiocarbónicas en 550 años de edad, se contaron 248 uniones radicales. La persistencia de sistemas radicales grandes, viejos, y altamente interconectados sugiere que la gran cantidad de recursos almacenados y consumidos en las raíces compensan un pobre desarrollo aéreo con una alta resiliencia vegetativa. Para un mejor entendimiento de los balances de carbono y del agotamiento de NSC en las cepas de rebollo, se midieron los flujos internos y externos de CO2 en troncos y los flujos de CO2 del suelo, y se estimó la respiración de órganos aéreos (RS) y subterráneos (RR). Estacionalmente, RS y RR reflejaron las dinámicas de flujo de savia y de crecimiento del tronco, y estuvieron determinadas principalmente por los flujos externos de CO2, dada la escasa contribución de FT a RS y RR (< 10% y < 2%, respectivamente). En una escala circadiana, la contribución de FT a RS aumentó hasta un 25% en momentos de alta transpiración. Las bajas concentraciones de CO2 en el xilema ([CO2] hasta un 0.11%) determinaron comparativamente unos bajos FT, probablemente causados por una limitada respiración del xilema y una baja resistencia a la difusión radial del CO2 impuestos por la sequía estival. Los pulsos de [CO2] observados tras las primeras lluvias de otoño apoyan esta idea. A lo largo del periodo vegetativo, el flujo medio de CO2 procedente del suelo (39 mol CO2 day-1) fue el mayor flujo respiratorio, tres y cuatro veces superior a RS (12 mol CO2 day-1) y RR (8-9 mol CO2 day-1), respectivamente. Ratios RR/RS menores que la unidad evidencian un importante peso de la respiración aérea como sumidero de carbono adicional. Finalmente, se ensayó el zanjado de raíces y el anillamiento de troncos como tratamientos selvícolas alternativos con el objetivo de aumentar las reservas de NSC en los troncos de las cepas. Los resultados preliminares desaconsejan el zanjado de raíces por el alto coste derivado posiblemente de la cicatrización de las heridas. El anillado de troncos imposibilitó el transporte de NSC a las raíces y aumentó la concentración de almidón por encima de la zona anillada, mientras que sistema radical se mantiene por los pies no anillados de la cepa. Son necesarias más mediciones y datos adicionales para comprobar el mantenimiento de esta respuesta positiva a largo plazo. Para concluir, destacamos la necesidad de estudios multidisciplinares que permitan una comprensión integral de la degradación de los rebollares ibéricos para poder aplicar a posteriori una gestión adecuada en estos montes bajos abandonados. ABSTRACT Quercus pyrenaica is a vigorous root-resprouting species intensively and historically coppiced for firewood, charcoal and woody pastures. Due to the rural exodus and the appearance of new energy sources, coppicing was abandoned towards 1970. Since then, tree overaging has resulted in stand stagnation displayed by slow stem growth, branch dieback, and scarce acorn production. The urgent need to find new alternative uses for abandoned coppices is recognized as one of the biggest challenges which currently faces Mediterranean silviculture; conversion into high forest by thinning is one of the preferred alternatives. For this aim, thinning has been broadly applied and seldom tested, although without a comprehensive understanding of the causes of stand stagnation. In this PhD study, we test the hypothesis of an imbalance between above- and below-ground organs, result of long term coppicing, as the underlying cause of Q. pyrenaica decay. In an experimental plot coppiced since at least the 12th century, genetic analyses were performed a priori to elucidate inconspicuous clonal structure of Q. pyrenaica to evaluate how clonal size affects the functioning of these multi-stemmed trees. Clonal size negatively affected diametric stem growth, whereas root respiration rates, measured by internal fluxes of CO2 through xylem (FT) and soil CO2 efflux, increased with clonal size. These results suggest root-to-shoot (R:S) imbalance intensifying with clonal size: periodic removal of aboveground organs whilst belowground organs remain undisturbed may have led to massive root systems which consume a great proportion of non-structural carbohydrates (NSC) for maintenance respiration, thus constraining aboveground performance. Furthermore, excavation of two multi-stemmed trees, composed by four and eight stems, revealed R:S ratios (0.5 and 1, respectively) greater than those reported for sexually regenerated trees. Moreover, as similarly observed in several root-resprouting species, NSC allocation to roots was favored ([NSC] > 20% in spring): a large proportion of sapwood maintained throughout the root system (52%) stored a remarkable NSC pool of 87 kg in the case of the largest clone. In this root system of the eight-stemmed tree, 248 root connections were counted and, by radiocarbon dating, its age was estimated to be 550-years-old. Persistence of massive, old and highly interconnected root systems suggests that enhanced belowground NSC storage and consumption reflects a trade-off between vegetative resilience and aboveground development. For a better understanding of tree carbon budget and the potential role of carbon starvation in Q. pyrenaica decay, internal and external stem CO2 fluxes and soil CO2 effluxes were monitored to evaluate respiratory costs above- and below-ground. On a seasonal scale, stem and root respiration (RS and RR) mirrored sap flow and stem growth dynamics. Respiration was determined to the greatest extent by external fluxes of CO2 to the atmosphere or soil, since FT accounted for a low proportion of RS and RR (< 10% and < 2%, respectively). On a diel scale, the contribution of FT to RS increased up to 25% at high transpiration rates. Comparatively low FT was determined by the low concentration of xylem CO2 registered ([CO2] as low as 0.11%), likely as a consequence of constrained xylem respiration and reduced resistance to CO2 radial diffusion imposed by summer drought. Xylem [CO2] pulses following first autumn rains support this idea. Averaged over the growing season, soil CO2 efflux was the greatest respiratory flux (39 mol CO2 day-1), three and four times greater than RS (12 mol CO2 day-1) and RR (8-9 mol CO2 day-1), respectively. Ratios of RR/RS below one evidence an additional and important weight of aboveground respiration as a tree carbon sink. Finally, root trenching and stem girdling were tested as complimentary treatments to thinning as a means to improve carbon reserves in stems of clonal trees. Preliminary results discouraged root trenching due to the high cost likely incurred for wound closure. Stem girdling successfully blocked NSC translocation downward, increasing starch concentrations above the girdled zone whilst the root system is fed by non-girdled stems within the clone. Further measurements and ancillary data are necessary to verify that this positive effect hold over time. To conclude, the need of multidisciplinary approaches for an integrative understanding on the functioning of abandoned Q pyrenaica coppices is highlighted for an appropriate management of these stands.

Predicting Forest Responses to Changing Environmental Conditions

Forests change with changes in their environment based on the physiological responses of individual trees. These short-term reactions have cumulative impacts on long-term demographic performance. For a tree in a forest community, success depends on biomass growth to capture above- and belowground resources and reproductive output to establish future generations. Here we examine aspects of how forests respond to changes in moisture and light availability and how these responses are related to tree demography and physiology.

First we address the long-term pattern of tree decline before death and its connection with drought. Increasing drought stress and chronic morbidity could have pervasive impacts on forest composition in many regions. We use long-term, whole-stand inventory data from southeastern U.S. forests to show that trees exposed to drought experience multiyear declines in growth prior to mortality. Following a severe, multiyear drought, 72% of trees that did not recover their pre-drought growth rates died within 10 years. This pattern was mediated by local moisture availability. As an index of morbidity prior to death, we calculated the difference in cumulative growth after drought relative to surviving conspecifics. The strength of drought-induced morbidity varied among species and was correlated with species drought tolerance.

Next, we investigate differences among tree species in reproductive output relative to biomass growth with changes in light availability. Previous studies reach conflicting conclusions about the constraints on reproductive allocation relative to growth and how they vary through time, across species, and between environments. We test the hypothesis that canopy exposure to light, a critical resource, limits reproductive allocation by comparing long-term relationships between reproduction and growth for trees from 21 species in forests throughout the southeastern U.S. We found that species had divergent responses to light availability, with shade-intolerant species experiencing an alleviation of trade-offs between growth and reproduction at high light. Shade-tolerant species showed no changes in reproductive output across light environments.

Given that the above patterns depend on the maintenance of transpiration, we next developed an approach for predicting whole-tree water use from sap flux observations. Accurately scaling these observations to tree- or stand-levels requires accounting for variation in sap flux between wood types and with depth into the tree. We compared different models with sap flux data to test the hypotheses that radial sap flux profiles differ by wood type and tree size. We show that radial variation in sap flux is dependent on wood type but independent of tree size for a range of temperate trees. The best-fitting model predicted out-of-sample sap flux observations and independent estimates of sapwood area with small errors, suggesting robustness in new settings. We outline a method for predicting whole-tree water use with this model and include computer code for simple implementation in other studies.

Finally, we estimated tree water balances during drought with a statistical time-series analysis. Moisture limitation in forest stands comes predominantly from water use by the trees themselves, a drought-stand feedback. We show that drought impacts on tree fitness and forest composition can be predicted by tracking the moisture reservoir available to each tree in a mass balance. We apply this model to multiple seasonal droughts in a temperate forest with measurements of tree water use to demonstrate how species and size differences modulate moisture availability across landscapes. As trees deplete their soil moisture reservoir during droughts, a transpiration deficit develops, leading to reduced biomass growth and reproductive output.

This dissertation draws connections between the physiological condition of individual trees and their behavior in crowded, diverse, and continually-changing forest stands. The analyses take advantage of growing data sets on both the physiology and demography of trees as well as novel statistical techniques that allow us to link these observations to realistic quantitative models. The results can be used to scale up tree measurements to entire stands and address questions about the future composition of forests and the land’s balance of water and carbon.

STUDIES OF FUNCTIONALIZED NANOPARTICLES FOR SMART SELF-ASSEMBLY AND AS CONTROLLED DRUG DELIVERY

This dissertation is related to the studies of functionalized nanoparticles for self-assembly and as controlled drug delivery system. The whole topic is composed of two parts. In the first part, the research was conducted to design and synthesize a new type of ionic peptide-functionalized copolymer conjugates for self-assembly into nanoparticle fibers and 3D scaffolds with the ability of multi-drug loading and governing the release rate of each drug for tissue engineering. The self-assembly study confirmed that such peptide-functionalized amphiphilic copolymers underwent different self-assembly behavior. The bigger nanoparticles were more easily assembled into nanoparticle fibers and 3D scaffolds with larger pore size, while the smaller nanoparticle underwent faster self-assembly to form more compact 3D scaffolds with smaller porosity but more stable structure. Controlled release studies confirmed the ability of governing simultaneous release of different model drugs with independent release rate from a same scaffold. Cytotoxicity tests showed that all synthesized peptides, copolymers and peptide-copolymer conjugates were biocompatible with SW-620 cell lines and NIH3T3 cell lines. This new type of self-assembled scaffolds combined the advantages of peptide nanofibers and versatile controlled release of polymeric nanoparticles to achieve simultaneous multi-drug loading and controlled release of each drug, uniform distribution and flexibility of hydrogel scaffolds. The investigations in second part were first to design and synthesize organic biocide-loaded nanoparticles for low-leaching wood preservation using a cost-effective one-pot method to synthesize amphiphilic chitosan-g-PMMA nanoparticles loading with ~25-28 wt.% of the fungicide tebuconazole with particle size of ~100 nm diameter by FESEM. FESEM analysis confirmed efficient penetration of nanoparticles throughout the treated wooden stake with dimension of 19 × 19 × 455 mm^3. Leaching studies showed that biocide introduced into sapwood via nanoparticles leached only ~9% compared with the amount leached from tebuconazole solution-treated control, while soil jar tests showed that the nanoparticle-treated wood blocks were effectively protected from biological decay tested against G. trabeum, a brown rot fungus. Copper oxide nanoparticles with and without polymer stabilizers were also investigated to use as inorganic wood preservatives to clarify the factor affecting copper leaching from treated wood. Copper oxide nanoparticles with uniform diameters of ~10 nm and ~50 nm were prepared, and the leachates from southern pine sapwood treated with these nanoparticles were analyzed. It was found by TEM and EDS analysis that significant numbers of nanoparticles leached from the treated wood. The 50 nm nanoparticles leached slightly less than a soluble copper salt control, but 10 nm nanoparticles leached substantially more than the control. The effect of polymer stabilizers on nanoparticle leaching was also investigated. Results showed that polymer stabilizers increased leaching. The trends showed that nanoparticle size was a major factor in copper leaching.