<p>Quantifying carbon fluxes and pools of forest ecosystems is an active research area in global climate study, particularly in the currently and projected increasing atmospheric carbon dioxide concentration environment. Forest carbon dynamics are closely linked to the water cycle through plant stomata which are regulated by environmental conditions associated with atmospheric and soil humidity, air temperature and light. Thus, it is imperative to study both carbon and water fluxes of a forest ecosystem to be able to assess the impact of environmental changes, including those resulting from climate change, on global carbon and hydrologic cycles. However, challenges hampering such global study lie in the spatial heterogeneity of and the temporal variability of fluxes in forests around the globe. Moreover, continuous, long-term monitoring and measurements of fluxes are not feasible at global forest scale. Therefore, the need to quantify carbon and water fluxes and to identify key variables controlling them at multiple stands and time scales is growing. Such analyses will benefit the upscaling of stand-level observations to large- or global-scale modelling approaches. </p><p>I performed a series of studies investigating carbon and water fluxes in pine forests of various site characteristics, conditions and latitudinal locations. The common techniques used in these studies largely involved sap flux sensors to measure tree-level water flow which is scaled up to stand-level transpiration and a process-based model which calculates canopy light absorption and carbon assimilation constrained by the sap-flux beased canopy stomatal conductance (called Canopy Conductance Constrained Carbon Assimilation or 4C-A model). I collected and analyzed sap flux data from pine forests of two major species: Pinus taeda in temperate (36 °N) and Pinus sylvestris in boreal (64 °N) climatic zones. These forests were of different stage-related canopy leaf area and some were under treatments for elevated atmospheric CO2 concentration or fertilization. </p><p>I found that (Chapter 2) the 17-year long free-air CO2 enrichment (FACE) had little effect on canopy transpiration of a mixed forest with the dominant P. taeda and other broadleaved species as the understory in North Carolina, USA (Duke FACE). The result was due to the compensation of elevated [CO2]-induced increase of canopy leaf area for the reduction of mean canopy stomatal conductance. My next theoretical study (Chapter 3), comparing P. taeda (native at 36 °N in North Carolina), P. sylvestris (native at 64 °N in norther Sweden) and Pinus contorta (native at 58 °N in British Columbia, Canada) canopies, revealed that the interaction between crown architecture and solar elevation associated with site latitude of pine canopies affected the distribution and total amount of canopy light absorption and potentially photosynthesis such that the latitudinally prescribed needle organization of a pine canopy is optimal for light interception and survival in its native location. Then, I quantified and analyzed water fluxes in four pine forests: one composed of P. taeda in North Carolina and three containing P. sylvestris in northern Sweden (Chapter 4). The latter forests consisted of various stage-related canopy leaf area and nutrient status. Combining my estimates with other published results from forests of various types and latitudinal locations, I derived an approach to estimate daily canopy transpiration during the growing season based on a few environmental variables including atmospheric and soil humidity and canopy leaf area. Moreover, based on a water budget analysis, I discovered that the intra-annual variation of precipitation in a forest has a small effect on evapotranspiration and primarily affecting outflow; however, variation of precipitation across latitudes proportionally influences anuual evapotranspiration and outflow. Furthermore, the hydrologic analyses implied the `disequilibrium' of forest water cycling during the growing season when forests may use less and more water in dry and wet regions, respectively, than the incoming precipitation. Nevertherless, at annual timescale, most forests became in `equilibrium' by using similar proportion of incoming precipitation. Finally, (Chapter 5) I estimated and analyzed the temporal and spatial variabilities of carbon fluxes of the same four forests measured in Chapter 4 using the 4C-A computational approach and analyzed their resource-use efficiencies. I concluded that, based on my results and others as available, despite the differences in species clumping and latitudes which influence growing season length and solar elevation, the gross primary productivity can be conservatively linearly related to the canopy light absorption. However, based on previous findings from a global study, different allocation of the acquired carbon to the above- and belowground is regulated by soil nutrient status. </p><p>Overall, the findings in this dissertation offer new insights into the impacts of environmental changes on carbon and water dynamics in forests across multiple sites and temporal scales which will be useful for larger-scale analyses such as those pertaining to global climate projection.</p> / Dissertation

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Submitted by Marlene Santos (marlene.bc.ufg@gmail.com) on 2016-09-15T18:07:05Z No. of bitstreams: 2 Dissertação - Ana Cláudia Oliveira Sérvulo - 2016.pdf: 2434108 bytes, checksum: 3547aafd1a987a6c13667cbd8aa9a2f8 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-09-16T12:18:45Z (GMT) No. of bitstreams: 2 Dissertação - Ana Cláudia Oliveira Sérvulo - 2016.pdf: 2434108 bytes, checksum: 3547aafd1a987a6c13667cbd8aa9a2f8 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-09-16T12:18:45Z (GMT). No. of bitstreams: 2 Dissertação - Ana Cláudia Oliveira Sérvulo - 2016.pdf: 2434108 bytes, checksum: 3547aafd1a987a6c13667cbd8aa9a2f8 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-04-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The African Mahogany’s commercial exploitation in the Brazilian Midwest lacks information to assist management strategies of the specie and natural resources, specially water. The transpiration and growth analysis are useful, not just for water management, but also to support physiological studies. The Granier method (thermal dissipation probe – TDP) uses sap flow measurements to estimate transpiration in woody species, however it requires validate for each new specie. This paper aimed to study the African Mahogany’s water consumption and growth in the Cerrado bioma. The main activities aimed to: a) Adjust the Granier’s sap flux method to African Mahogany; b) Quantify water consumption and vegetative growth on a 2.5 years old African Mahogany’s forest, under two water regimes; c) Establish relations between tree transpiration and atmospheric water demand. This research consisted of two experiments. The first one, happened in oct-nov/2014 and feb-may/2015, consisted of the Granier’s model adjustment with aid of the lysimetry, for use in African Mahogany’s transpiration measurements. The second experiment, happened between oct/2014 and oct/2015, on a commercial forest up to 2.5 years old, evaluated water consumption (transpiration by leaf area – T) using integrated sap flux measurements by TDP, and vegetative growth [leaf area (AF), diameter at breast height (DAP), tree height (Alt), trunk volume (VTR) and leaf dry biomass (BMF)], treatments were defined as: T1 – forest with irrigation interrupted at two years old; T2 – forest without irrigation. The adjusted sap flux model to African mahogany is F    k  AS 6 1,231 268,25 10 , and the original Granier’s model underestimates the transpiration in 39.1%. The average potential transpiration was between 2.1 and 34.8 L day-1. In field conditions, the growth benefits from the T1 are seen in highest values for AF, DAP and BMF. However, the Alt and VTR are not significant different. The monthly T under field conditions varied between 10.2 and 24.2 L m-2, except for jul-aug/2015, when T2 transpiration was higher. The combination of bigger leaf area and low soil water content led to T1’s water deficit scenario. / A exploração comercial do Mogno Africano (Khaya ivorensis) no Centro- Oeste brasileiro carece de informações sobre a espécie para auxiliar no desenvolvimento de estratégias de ações no manejo da espécie e dos recursos naturais, em especial a água. Para tal, os estudos do processo transpiratório e de análise de crescimento são úteis, não só para o manejo da água no processo produtivo, como também para sustentar estudos fisiológicos. O método de Granier (sonda de dissipação térmica – SDT) utiliza a medida do fluxo de seiva como base para estimativa da transpiração em espécies lenhosas, todavia seu uso requer validação do modelo para cada nova espécie. Este trabalho tem como objetivo determinar consumo hídrico e o crescimento do Mogno Africano no bioma Cerrado. As atividades envolvidas visaram: a) Ajustar o modelo de Granier para estimativa da transpiração em Mogno Africano; b) Quantificar o consumo de água e o crescimento vegetativo em uma floresta a partir dos 2,5 anos de idade em dois regimes hídricos; c) Estabelecer a relação entre a transpiração das árvores e a demanda hídrica da atmosfera em condições naturais de disponibilidade de água no solo. A pesquisa constituiu de dois experimentos. O primeiro experimento foi realizado entre out-nov/2014 e fev-mai/2015 e objetivou o ajuste do modelo de Granier a partir da lisimetria na medida da transpiração do Mogno Africano. O segundo experimento foi realizado a campo entre out/2014 e out/2015, em um plantio comercial a partir de 2,5 anos de idade, avaliou-se o consumo hídrico (transpiração por unidade de área foliar – T), por meio da integração do fluxo de seiva medido com a SDT, e o crescimento vegetativo [área foliar (AF), diâmetro à altura do peito (DAP), altura (Alt), volume de tronco (VTR) e biomassa seca de folhas (BMF)]; os tratamentos foram definidos como: T1 – floresta com irrigação interrompida aos dois anos; T2 – floresta não irrigada. O modelo ajustado para o Mogno Africano é F    k  AS 6 1,231 268,25 10 . O modelo original de Granier subestima em 39,1% a transpiração do Mogno Africano. A transpiração potencial média foi de 13,0 L dia-1. Em campo, a superioridade do crescimento em AF, DAP e BMF prevaleceu para o tratamento T1. Porém o incremento em Alt e VTR foi similar nos dois grupos avaliados. A T em campo variou entre 10,2 e 24,2 L m-2 mês-1, respondendo diretamente à demanda evaporativa atmosférica, exceto em jul e ago/2015, nos quais T2 apresentou maior T. A combinação entre maior área foliar e baixo armazenamento de água no solo (a partir de 33,6 mm) promoveu menor transpiração à T1 devido ao esgotamento precoce da água do solo.

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Native plant communities and agricultural land are commonly converted to urban areas as cities across the Western United States continue to grow and expand. This expansion is typically accompanied by afforestation where a common goal among communities is to maximize shade tree composition. Planted forests in these regions are commonly composed of introduced tree species native to mesic environments and their ability to persist is dependent on consistent irrigation inputs. Many potential ecosystem services may be derived from planting trees in urban and suburban areas; however, there are also costs associated with extensive afforestation, and shade tree cover may have significant implications on municipal water budgets. In this study I evaluate variation in daily and seasonal water use of regionally common suburban landscape tree species in the Heber Valley (Wasatch County, Utah). I had two primary objectives: (1) to identify and understand the differences in transpiration between landscape tree species in a suburban setting and (2) to assess the sensitivity of sap flux and transpiration to variation in vapor pressure deficit, wind speed, and incoming shortwave radiation. I used Granier's thermal dissipation method to measure the temperature difference (ΔT) between two sap flux probes. The empirical equation developed by Granier was used to convert ΔT into sap flux density (Jo) measurements, which were then scaled to whole-tree transpiration. There were consistent and substantial differences in sap flux between tree species. I found that Picea pungens under irrigated growing conditions, on average, had Jo rates that were 32% greater and whole tree water use (ET) rates that were 550% greater than all other species studied. The findings of Jo may be partially explained by xylem architecture and physiological control over stomatal aperture. However, the rate of water flux in the outermost portion of sapwood does not necessarily determine the magnitude of whole tree transpiration. Rather, ET in this study was largely explained by the combined effects of irrigation, tree size, and sapwood to heartwood ratio.

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