ABSTRACT The effects of restoration on dissolved organic carbon (DOC) dynamics were examined at the Boi~-des-Bel peatland. This study included both laboratory measurements of DOC production by different peatland vegetative components and field measurements of DOC dynamics within a recently restored, a cutover and a natural peatland. Shrub and herbaceous plant material were found to be the most significant producers of DOC in the short term. Moss, peat and straw samples had a high potential to release DOC ;;ontinuously under warm, moist and aerobic conditions. On a short timescale, all components have the potential to release the three dissolved organic matter (DOM) fractions examined with humic acid (HA) most prominently being produced by shrubs and herbaceous plants and hydrophilic (HPI) and hydrophobic (HPO) fractions by mosses, peat and straw. Comparison of growing season results over three study years at the restored and cutover site indicated that DOC concentrations increased after restoration while DOC export decreased due to lowered runoff caused by the blockage of drainage ditches. Compared to the natural peatland, both the restored and the cutover site had a more humic DOM character. No difference could be found between the character of DOM released from the restored and cutover sites. The most active layer of DOM production was the top 75 em where the water iii table fluctuated during the season. Water storage units such as pools and ditches also play an important role in DOM export from the site. Spring snowmelt was found to be the most significant DOC export event of the study season in 2001, when export values were significantly larger than those measured during the growing season. Solubility of the different DOM fractions was the main controlling factor on the DOM character seen at the outflows. Storm events contributed significantly to the summer DOC output. DOC dynamics were affected by antecedent moisture conditions and differences emerged between the restored and cutover site during this period. The results of this study emphasize the importance of managing water table fluctuations and the restoration (reestablishment) of Sphagnum species in order to improve the retention of DOM within cutover peatlands. / Thesis / Master of Science (MS)

Inland waters such as streams and lakes have recently been found to be supersaturated with both carbon dioxide (CO2) and methane (CH4) – the high concentrations resulting in significant natural emissions of greenhouse gases (GHGs). Previous studies have shown that streams emit particularly large amounts of GHGs per area covered, but the spatial variability is very high and has rarely been studied in detail. This study focuses on the variability of aquatic CO2 and CH4 concentrations with high spatial resolution in a hemi-boreal stream. The study area is a 7 km2 catchment in Skogaryd in southwest Sweden. 131 samples were collected and the stream was divided into groups depending on slope gradient and geographical placement. The results show that the concentrations had high spatial variability, especially regarding CH4, and that the concentrations are higher and more variable at lower slope gradients, which possibly indicates an increased gas exchange at higher slopes. The results also showed that concentrations can increase or decrease sharply over short distances in relation to changing slope gradient. This shows that frequent spatial sampling is needed to more accurately represent streams than what is often the case in many studies. A general distance between sampling locations could not be found due to the high variability of concentrations. Instead, the authors suggest that future studies of CO2 and CH4 concentrations in streams use a stratified random sampling strategy based on slope gradients.

The land ecosystems in northern high latitudes (>45° N) occupy 22% of the global surface and store more than 1600 Pg soil organic carbon. Warming in this region has been documented during the past decades. Warming-induced changes in regional carbon dynamics are expected to loom large in the global carbon cycle and exert large feedbacks to the global climate system. Numerous Earth System Models have been widely used to quantify the response of terrestrial ecosystem carbon dynamics to climatic changes. However, predictions of terrestrial ecosystem carbon responses to increasing levels of atmospheric carbon dioxide (CO2) and climate change is still uncertain due to model limitations. The limitations include relatively low levels of representation of ecosystem processes that determine the exchanges of water, energy, and carbon between land ecosystems and the atmosphere and omitting some key biogeochemical mechanisms. To improve model realism and provide a better projection of the Arctic carbon dynamics, this dissertation developed three new versions of a process-based biogeochemistry models that involve more fundamental processes of terrestrial ecosystems. First, microbial dynamics and enzyme kinetics that catalyze soil carbon decomposition have been incorporated into the extant terrestrial ecosystem model TEM to remedy the inadequate representation of soil decomposition process. Furthermore, a vital microbial life-history trait, microbial dormancy, has been implemented into previous microbial-based model to consider the impacts of microbial dormancy in modeling. Additionally, the role of moss in the Arctic terrestrial ecosystem carbon quantification was also demonstrated by incorporating moss and higher plant interactions in modelling.

This study examined the annual C balance and its shifting trend in Canada’s managed forests from 1991 to 2006 using the Integrated Terrestrial Ecosystem C-budget (InTEC) model. During this period, Canada’s managed forests remained a moderate C sink of 58 Mt C yr¬¬¬-1 on average, but displayed an apparent trend of shifting towards a C source. The combined risk of climate change and increased disturbances are weakening the C sink in Canada’s managed forests. This study also compared the results from InTEC with those from CBM-CFS (Carbon Budget Model of the Canadian Forest Sector) at both national and regional levels. InTEC shows larger inter-annual variability and regional difference than CBM-CFS due to its incorporation of both disturbance and non-disturbance factors. In comparison, CBM-CFS3 has likely underestimated both the true C loss and the C sink potential of Canada’s managed forests, given that it does not account for the non-disturbance factors.

This study examined the annual C balance and its shifting trend in Canada’s managed forests from 1991 to 2006 using the Integrated Terrestrial Ecosystem C-budget (InTEC) model. During this period, Canada’s managed forests remained a moderate C sink of 58 Mt C yr¬¬¬-1 on average, but displayed an apparent trend of shifting towards a C source. The combined risk of climate change and increased disturbances are weakening the C sink in Canada’s managed forests. This study also compared the results from InTEC with those from CBM-CFS (Carbon Budget Model of the Canadian Forest Sector) at both national and regional levels. InTEC shows larger inter-annual variability and regional difference than CBM-CFS due to its incorporation of both disturbance and non-disturbance factors. In comparison, CBM-CFS3 has likely underestimated both the true C loss and the C sink potential of Canada’s managed forests, given that it does not account for the non-disturbance factors.

Submitted by Natalia de Souza Gonçalves (natalia.goncalves@ufpe.br) on 2016-09-20T14:48:56Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação_Natache_Ferrão.pdf: 350140 bytes, checksum: fbbfdb5e63d78d74c935fcea9cf90919 (MD5) / Made available in DSpace on 2016-09-20T14:48:56Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação_Natache_Ferrão.pdf: 350140 bytes, checksum: fbbfdb5e63d78d74c935fcea9cf90919 (MD5) Previous issue date: 2016-02-24 / CNPq / A matéria orgânica do solo (MOS) compõe um compartimento dinâmico, composto por uma mistura complexa de resíduos vegetais e animais em diversos estádios de decomposição. De forma didática, o carbono (C) presente na MOS pode ser dividido em compartimentos, diferenciados por similaridades estruturais, estabilidade e dinâmica. Neste trabalho utilizamos as definições dos compartimentos da MO: Compartimento ativo ou lábil: constituído por componentes facilmente oxidáveis, estando fortemente sujeito a alterações resultantes do manejo do solo; Compartimento lento: ligado a formação de micro e macroagregados do solo (o manejo influencia diretamente na ocorrência dos macroagregados, mas muito pouco a ocorrência de microagregados); Compartimento passivo: substâncias húmicas estáveis supostamente não afetadas pelas técnicas de manejo. Na literatura, ainda há muitas lacunas e controvérsias sobre as metodologias para quantificação do C nessas frações em diferentes tipos de solos. Parte dessa dificuldade pode ser função das variações das classes de solo, do clima e manejo a que esses solos estão submetidos. Sendo assim, constata-se que esse é um tema de alta relevância, pois, as metodologias de avaliação do C influenciam a geração de dados e as estimativas da dinâmica do C no solo e seu tempo de permanência. Portanto, o presente trabalho tem como objetivo avaliar a viabilidade do fracionamento do carbono da matéria orgânica do solo utilizando o método de hidrólise enzimática, como método alternativo aos métodos tradicionais de fracionamento. Foi utilizado um Argissolo de região de clima tropical úmido sob dois manejos: mata nativa preservada e plantio de cana-deaçúcar. O sítio experimental escolhido para a coleta das amostras de solo foi a estação experimental do Instituto Agronômico de Pernambuco (IPA), no município de Itambé, PE, localizada na Zona da Mata Norte de Pernambuco. As amostras foram coletadas nas camadas de 0-20 cm. Para liberação e quantificação dos compostos de carbono das frações da MOS através da hidrólise enzimática, foi realizada uma sequência analítica constituída por duas etapas: (i) Extração do carbono solúvel em água quente (ii) Hidrólise enzimática. No solo sob cultivo com cana-de-açúcar a proporção da fração mais lábil de carbono, extraída com água quente, foi maior que no solo sob mata. Houve uma maior proporção na quantificação da matéria orgânica em solo sob mata atlântica para o método de demanda química de oxigênio (DQO). O método de DQO mostrou-se eficaz como método auxiliar ao analisador TOC na quantificação da matéria orgânica para o método de extração por água quente. O acetato de sódio utilizado como tampão orgânico causou interferência na leitura do CO dos hidrolisados pelo analisador TOC. A utilização de água deionizada no lugar do tampão orgânico demonstrou ser uma alternativa para substituir o acetato, pois não foram observadas diferenças significativas de pH ao longo do tempo reacional. Nos testes utilizando água deionizada, foi observado decréscimo dos teores da MO em relação ao tempo, podendo estar relacionado à interferência de elementos presentes no solo, à falta de precisão do método analítico empregado, à perda de MO durante o processo reacional e/ou à incorporação da MO ao substrato (solo). Os teores de CO nos hidrolisados obtidos pelo método de hidrólise enzimática mostraram correlação positiva com a adição de enzimas, entretanto, a adição de enzimas introduz quantidades significativas de C ao meio reacional, o que indica que serão necessárias mudanças no método analítico. / The soil organic matter (SOM) comprises a dynamic compartment consists of a complex mixture of plant and animal residues in various stages of decomposition. Didactically, carbon (C) present in the SOM can be divided into compartments, differentiated by structural similarities, stability and dynamics. In this work we use the definitions of the storage MO: active or labile compartment: consisting of easily oxidized components, being strongly subject to change resulting from soil management; slow compartment: on the formation of micro- and macroaggregates soil (management directly influences the occurrence of macroaggregates, but very little the occurrence of micro-aggregates); Passive Housing: stable humic substances supposedly not affected by management techniques. In the literature, there are still many gaps and controversies about the methodologies for quantification of these fractions carbon in different types of soils. Part of this difficulty may be a function of variations in soil types, climate and management that these soils are submitted. Thus, it appears that this is a highly important issue because the evaluation methodologies of C influence the generation of data and the carbon dynamics of the estimates in the soil and your length of stay. Therefore, this study aims to evaluate the viability of the soil organic matter carbon fractionation using the enzymatic hydrolysis method as an alternative method to traditional methods of fractionation. Ultisol of humid tropical climate region was used in two managements: preserved native forest and planting sugarcane. The experimental site chosen for the collection of soil samples was the experimental station of the Agronomic Institute of Pernambuco (IPA), in the city of Itambé, PE, located in the North Forest Zone of Pernambuco. The samples were collected at 0-20 cm. To quantify the release and carbon compounds of SOM fractions by enzymatic hydrolysis, an analytical sequence consists of two steps it taken: (i) Carbon Extraction hot water soluble (ii) Enzymatic hydrolysis. The soil under cultivation of sugarcane the proportion of the more labile fraction of carbon, extracted with hot water, was higher than in the soil under forest. There was a higher proportion in the quantification of organic matter in soil under rainforest for chemical demand method of oxygen (COD). The COD method was effective as an auxiliary method to the TOC analyzer quantification of organic matter to the extraction method by hot water. The sodium acetate buffer used as organic interference caused CO hydrolyzed by reading the TOC analyzer. The use of deionized water in place of the organic buffer to be an alternative to replace the acetate, as significant differences in pH during the reaction time were not observed. In tests using deionized water, was observed decrease of OM content in relation to time, may be related to the interference of elements present in the soil, lack of precision of the analytical method employed, the loss OM during the reaction process and / or OM incorporation of the substrate (soil). CO contents in the hydrolysates obtained by enzymatic hydrolysis method showed a positive correlation with addition of enzymes, however, the addition of enzymes introduces significant amounts of carbon to the reaction medium, which indicates that changes will be needed in the analytical method.

京都大学 / 0048 / 新制・論文博士 / 博士(農学) / 乙第13262号 / 論農博第2875号 / 新制||農||1071(附属図書館) / 学位論文||R1||N5217(農学部図書室) / (主査)教授 山下 洋, 教授 澤山 茂樹, 教授 吉岡 崇仁 / 学位規則第4条第2項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

<p> Forest ecosystems play an important role in the global carbon (C) cycle by exchanging large amounts of carbon dioxide (CO₂) with the atmosphere. Their potential to act as significant sink for atmospheric CO₂ has been recognized and is relevant to current efforts in reducing atmospheric CO₂ concentrations. Besides the most important greenhouse gas CO₂, forests also emit and consume methane (CH₄) and nitrous oxide (N₂O) as the two other important atmospheric greenhouse gases (GHGs). To date, few attempts have been made to quantify the net effect of forest GHG exchange on the global warming potential. Furthermore, a better understanding of successional and environmental effects on forest processes is required to improve large scale estimates of forest C and GHG exchange. </p> <p> This thesis examines C dynamics and the exchange of the three major greenhouse gases (CO₂, CH₄, and N₂O) in an age-sequence (7-, 20-, 35-, and 70-years-old as of 2009) of afforested pine forests, in southern Ontario, Canada. The impacts of environmental controls on these GHG exchanges were also evaluated. Forest C exchange was determined for 2003 to 2008 using the eddy-covariance (EC) technique and inventory-based biometric measurements. Soil CH₄ and N₂O measurements were conducted from 2006 to 2007 using the static closed-chamber method. In addition, concentrations and fluxes of dissolved organic carbon (DOC) throughout the vertical profile in forest canopy and soil were determined from 2004 to 2005 using throughfall buckets and lysimeters. </p> <p> During periods without climatic constraints, monthly gross ecosystem productivity (GEP) and ecosystem respiration (RE) corrected for differences in site index increased with stand age, whereas monthly net ecosystem productivity (NEP) peaked at the 35-year-old site. In contrast, during constrained periods (e.g. seasonal drought events), monthly GEP and NEP at the 20-year-old site were higher compared to the 35-year-old site because trees may have benefited from sustained availability of soil water in deeper layers. This study further demonstrates that differences in site quality may affect the interpretation of age-related C flux dynamics in chronosequence and synthesis studies (Chapter 2). </p> <p> The temperature-RE relationship was an important control on daily NEP anomalies under optimum growing conditions, whereas constrains on GEP primarily determined NEP during environmentally constrained periods. Furthermore, effects from single environmental variable constrains on NEP anomalies were enhanced as well as outbalanced under multiple environmental variable constrains. The results further indicate that future changes in temperature and precipitation patterns towards drier and warmer conditions as well as greater cloud cover may result in reduced C sequestration potentials in these temperate pine forests (Chapter 3). </p> <p> Early summer drought and heat events in 2005 caused NEP to decrease by approximately 100 g C m⁻² y⁻¹ at each site compared to the other years. This decrease was primarily driven by a decrease in photosynthesis, while the effect of these events on ecosystem respiration was small. Overall, for the years 2003-2007, annual NEP was 219, 155, 36, 148, and 120 g C m⁻² y⁻¹ at the 68-year-old site, 666, 318, 346, 511 and 366 g C m⁻² y⁻¹ at the 33-year-old site, 768, 885, 684, 708 and 826 g C m⁻² y⁻¹ at the 18-year-old site, and-18, 145, 125, 34 and 164 g C m⁻² y⁻¹ at the 5-year-old seedling site, respectively (negative numbers indicating net C source (Chapter 4). </p> <p> Four-year mean values of biometric NEP_(B) and EC-based NEP_(EC) were similar at the 7-year-old seedling (77 and 66 g C m⁻² y⁻¹) and the 70-year-old mature site (135 and 124 g C m⁻² y⁻¹), but differed considerably at the 20-year-old (439 and 736 g C m⁻² y⁻¹) and the 35-year-old sites (170 and 392 g C m⁻² y⁻¹). Integrating NEP across the age-sequence resulted in a total net C sequestration of 137 and 229 t C ha⁻¹ over the initial 70 years as estimated by the biometric and EC method, respectively. The total ecosystem C pool at the 70-year-old site suggested an accumulation of 160 t C ha⁻¹. These three estimates resulted in a mean C sequestration of 175 ± 48 t C ha⁻¹ (Chapter 5). </p> <p> For both CH₄ and N₂O, we observed uptake and emission ranging from -160 to 245 μg CH₄ m⁻² hour⁻¹ and -52 to 21 μg N₂O m⁻² hour⁻¹, respectively (negative values indicate net uptake). Mean N₂O fluxes from mid-April to mid-December across the 7-, 20-, 35-, 70-years old stands were -3.7, 1.5, -2.2, and-7.6 μg N₂O m⁻² hour⁻¹, without age-related pattern, whereas the uptake rates of CH₄ increased with stand age from 6.4 to -7.9, -10.8, and-23.3 μg CH₄ m⁻² hour⁻¹, respectively. For the same period, the combined contribution of CH₄ and N₂O exchanges to the global warming potential (GWP) calculated from net ecosystem exchange of CO₂ and aggregated forest floor exchanges of CH₄ and N₂O was on average <4% (Chapter 6). </p> <p> DOC concentration in forest floor leachates was positively correlated to stand age, aboveground biomass and forest floor carbon pools. From the period of Mid-April to December, DOC fluxes via precipitation, throughfall, and leaching through forest floor and Ah-horizon were in the range of ~1 to 2, 2 to 4, 0.5 to 3.5, and 0.1 to 2 g DOC m⁻², respectively. DOC export from the forest ecosystem during that period through infiltration and groundwater discharge decreased with increasing stand age from ~7 to 4, 3, and 2 g DOC m⁻² (Chapter 7). </p> <p> This thesis improved our understanding of C and GHG exchange dynamics and their environmental, physical, and physiological controls in forest ecosystems. This study will also contribute to efforts being made to better predict future forest C and GHG dynamics and their feedbacks on climate under changing environmental conditions. <p> / Thesis / Doctor of Philosophy (PhD)

Canopy structure has long been thought to influence the productivity and ecological dynamics of tropical forests by altering the availability of light to leaves. Theories and methods that can connect detailed quantitative observations of canopy structure with forest dynamics, however, have been lacking. There is urgent need to resolve this uncertainty because human-caused climate change may alter canopy structure and function in the Amazon. This work addresses this problem by, first, developing methods based on LiDAR remote sensing of fine-scale structural variation to predict the spatial structure of leaf area and light in forest canopies of the central Amazon (Appendices B&C). I show that LiDAR-based leaf area and light estimates can be used to predict the productivity of tree size groups and one-hectare forest plots--as well as differences between 2 sites separated by 500km (App. B). Sites also differed in canopy structure and the distribution of tree frequencies over size (size or diameter distribution). A model based on tree architecture, however, was able to connect observed differences in canopy architecture with size distributions to predict plot and site differences (App. D). This model showed that tree architecture is plastic in different light environments. While plasticity may increase light absorption, the smallest size groups appeared light limited. Absorption over size groups in one site, but not the other, agreed with the hypothesis of energetic equivalence across size structure. Ultimately, the performance of individual trees of different sizes in different canopy environments links forest demography with canopy structure and ecosystem function--I present a study aimed at improving tests of individual level theories for the role of light dependence in tree growth (App. A). Together, this work quantitatively connects canopy structure with forest carbon dynamics and demographic structure and further develops LiDAR as premier tool for studying forest ecological dynamics. Assessing variation in biomass growth and demographic structure over tropical landscapes with remote sensing will improve understanding of ecosystem function and the role of the Amazon in global Carbon dynamics.

Foi apresentado um sistema automatizado para monitorar fluxos de metano (CH4) e do dióxido de carbono (CO2) na relação da água/ar de ecossistemas aquáticos. Consiste em uma série de câmaras flutuantes dinâmicas acopladas a um analisador photo acústico infravermelho de gás. Associado os outros sensores atmosféricos e de qualidade da água, foi possível identificar os fatores atmosféricos, hidrológico e biológico que afetam emissões de CH4 e de CO2 no reservatório de Corumbá (estado de Goiás), uma terra inundada antropogenica de savana. O estudo realizado em novembro 2004 e em março/agosto 2005 permitiu uma inter-correlação desobstruídos de estabelecimento da câmara, embora relações ligadas da profundidade-fluxo. Os fluxos de CH4 borbulhando médios em novembro 2004, em março e em agosto 2005 eram respectivamente 0.05 ± 2.19, 4 ± 45 e 505 o ± 1192 mg/m2/d. Para os mesmos meses, as emissões de CH4 difusivo médias foram 17 o ± 6, 37 ± 9 e 69 o ± 28 mg/m2/d, visto que os fluxos difusivo do CO2 foram respectivamente 59 o ± 398, 385 ± 629 e o ± 1466 1223 mg/m2/d. Um aspecto interessante de bolhas de CH4 é a liberação repentina e grande em locais rasos e liberação do escoamento em locais profundos. Em uma base diária, a freqüência e o valor de bolhas de CH4 são condicionados à oxidação durante períodos da flutuação do lago, e às mudanças totais da pressão exercidas no sedimento. Em escalas de tempo sazonal, a intensidade de bolhas de CH4 é condicionada principalmente pela disponibilidade da carcaça ao metanogeneses. As frentes frias são responsáveis pela a ruptura da estratificação (misturar), favorecendo emissões do CO2 depois da oxidação CH4. As emissões do CO2 puderam também ser acopladas ao diel metanotrófico. Nossos resultados sugerem que as emissões de gás do efeito estufa de Corumbá estão controladas pela maior parte pelo nível de água e pela luz solar. / It was present an automated system for monitoring methane (CH4) and carbon dioxide (CO2) fluxes at the water/air interface of aquatic ecosystems. It consists of a series of floating dynamic chambers coupled to an infrared photo acoustic gas analyzer. Associated to other atmospheric and water quality sensors, it was possible to identify atmospheric, hydrologic and biological factors affecting CH4 and CO2 emissions at Corumbá reservoir (State of Goiás), a savanna anthropogenic flooded land. The study carried out in November 2004 and March/August 2005 allowed establishing clear chamber inter-correlations, although intricate depth-flux relations. Mean CH4 bubbling fluxes in November 2004, March and August 2005 were respectively 0.05 ± 2.19, 4 ± 45 and 505 ± 1192 mg/m2/d. For the same months, mean CH4 diffusive emissions were 17 ± 6, 37 ± 9 and 69 ± 28 mg/m2/d, whereas CO2 diffusive fluxes were respectively 59 ± 398, 385 ± 629 and 1466 ± 1223 mg/m2/d. An interesting aspect of CH4 bubbling is the sudden and large release at shallow sites and seepage release at deep sites. On a daily basis, the frequency and magnitude of CH4 bubbling is conditioned to oxidation during overturn periods, and to the total pressure changes exerted on the sediment. At seasonal time scales, CH4 bubbling intensity is mainly conditioned by substrate availability to methanogenesis. Cold fronts are responsible for stratification rupture (mixing), favoring CO2 emissions following CH4 oxidation. CO2 emissions might also be coupled to diel methanotrophy. Our results suggest that greenhouse gas emissions from Corumbá are largely controlled by water level and sunlight.