abstract: Rangelands are an extensive land cover type that cover about 40% of earth’s ice-free surface, expanding into many biomes. Moreover, managing rangelands is crucial for long-term sustainability of the vital ecosystem services they provide including carbon (C) storage via soil organic carbon (SOC) and animal agriculture. Arid rangelands are particularly susceptible to dramatic shifts in vegetation cover, physical and chemical soil properties, and erosion due to grazing pressure. Many studies have documented these effects, but studies focusing on grazing impacts on soil properties, namely SOC, are less common. Furthermore, studies testing effects of different levels of grazing intensities on SOC pools and distribution yield mixed results with little alignment. The primary objective of this thesis was to have a better understanding of the role of grazing intensity on arid rangeland soil C storage. I conducted research in long established pastures in Jornada Experimental Range (JER). I established a 1500m transect in three pastures originating at water points and analyzed vegetation cover and SOC on points along these transects to see the effect of grazing on C storage on a grazing gradient. I used the line-point intercept method to measure and categorize vegetation into grass, bare, and shrub. Since soil adjacent to each of these three cover types will likely contain differing SOC content, I then used this vegetation cover data to calculate the contribution of each cover type to SOC. I found shrub cover and total vegetation cover to decrease, while grass and bare cover increased with decreasing proximity to the water source. I found areal (g/m2) and percent (go SOC to be highest in the first 200m of the transects when accounting for the contribution of the three vegetation cover types. I concluded that SOC is being redistributed toward the water source via foraging and defecation and foraging, due to a negative trend of both total vegetation cover and percent SOC (g/g). With the decreasing trends of vegetation cover and SOC further from pasture water sources, my thesis research contributes to the understanding of storage and distribution of SOC stocks in arid rangelands. / Dissertation/Thesis / Masters Thesis Biology 2018

Rising atmospheric CO2 concentrations have motivated efforts to better quantify reservoirs and fluxes of Earth’s carbon. Of these fluxes from the atmosphere, one that has received relatively little attention is the atmospheric carbon sink associated with carbonate mineral dissolution. Osterhoudt (2014) and Salley (2016) explored new normalization techniques to improve and standardize a process for measuring this flux over large river basins. The present research extends this work to the 490,600 km2 Ohio River drainage basin and 11 subbasins. The study estimated the DIC flux leaving these basins between October 1, 2013, and September 30, 2014, based on secondary hydrogeochemical, geologic, and climatic data. The total annual DIC flux for the Ohio River basin was estimated to be 7.54 x 1012 g carbon (C). The time-volume normalized value of DIC flux for the Ohio basin was 3.36 x 108 g C/km3 day, where the km3 refers to the amount of water available during the year. This was within 71.4% agreement with the Barren River data (Salley, 2016) and within 63.9% agreement with the Green River data (Osterhoudt, 2014). In general, normalized DIC flux values of sub-basins containing at least modest amounts (more than 8%) of exposed carbonates (Tennessee, Cumberland, Green, Kentucky, Licking, Monongahela, and Allegheny) were in strong agreement with the normalized DIC flux of the Ohio River basin, whereas inclusion of basins with little or no near surface carbonates (Wabash, Great Miami, Scioto and Kanawha) yielded poor agreement. Regression analysis yielded strong agreement between DIC flux and the normalization parameters for the carbonate-bearing sub-basins (R2 = 0.97, p =

Rangelands have significant potential to sequester carbon and contribute to the mitigation of climate change. This research aimed at better understanding the beliefs, attitudes, and perceptions of Utah rangeland owners concerning carbon sequestration and climate change, examining their current grazing management practices in relation to soil carbon sequestration, and exploring factors influencing their likelihood of participating in future programs. Data were collected through interviews of Utah rangeland owners and range management professionals and a statewide rangeland owner survey. About two-thirds of respondents thought the climate had been changing over the last 30 years, were aware of carbon sequestration, and viewed it positively. Forty-one percent considered it an important management objective. Having positive attitudes was associated with having “biocentric” environmental value and believing climate change and its anthropogenic nature. Respondents valued the potential ecological benefits of carbon sequestration, indicated a preference for educational programs over financial incentives, and preferred working with private agricultural organizations over non-profit or government entities on carbon management. Thirty-seven percent of respondents reported likely to participate in a carbon sequestration program. Higher likelihood was associated with dependence on livestock production, considering carbon sequestration an important management objective, being interested in learning more about it, and placing high importance on the economic and climate benefits of participating in relevant programs. These results suggest potential challenges for developing technically sound and socially acceptable policies and programs for promoting carbon sequestration on private rangelands. Rangeland owners’ attitudes towards carbon sequestration may play a strong role in their participation in future programs. Although education and outreach are considered important, innovative strategies are needed to communicate the concept and processes of carbon sequestration with rangeland owners without politicizing the issue. One approach is to tailor education and outreach messages to focus on the ecological benefits of carbon sequestration. Efforts are also needed to enhance the cooperation between private agricultural organizations and government agencies to promote carbon management on private rangelands. Instead of developing new programs, funneling resources to improve the carbon sequestration potential of existing conservation programs and attract wider participation among rangeland owners may be another cost effective policy strategy.

The boreal forest is one of the worlds largest forest biomes and comprises a major portion of the terrestrial carbon (C) sink. Quantifying the net C change in forest ecosystems is an important step in understanding and modeling the global C cycle. The goals of this project were: to estimate and compare the total change in ecosystem C over a 10-year period in two boreal forest stands using biometric and eddy-covariance approaches, and to evaluate the year-to-year changes in C uptake. This study utilized 10 years of eddy-covariance data and ecosys model data from the Old Aspen (OA) and Old Jack Pine (OJP) sites in central Saskatchewan, part of the Boreal Ecosystem Research and Monitoring Sites (BERMS). According to the eddy-covariance and C stock approaches, between 1994 and 2004 the net change in C storage at OA was 15.6 ± 4.0 and 18.2 ± 8.0 Mg C ha-1, respectively. At OJP, the 10-year net change in C storage from eddy-covariance was 5.8 ± 2.0 Mg C ha-1 in comparison to 6.9 ± 1.6 Mg C ha-1 from the carbon stock approach. While both sites were sinks of C between 1994 and 2004, the greatest increase in C occurred in different components - the forest floor at OA (14.6 Mg C ha-1) and in the living vegetation at OJP (8.0 Mg C ha-1). In 2004, total ecosystem C content was greater at OA (180.6 Mg C ha-1) than OJP (78.9 Mg C ha-1), with 50% (OA) and 39% (OJP) of the C in the detritus and mineral soil pools. During the 10-year period of eddy-covariance measurements, there was a positive correlation between both annual and growing season gross ecosystem photosynthesis (GEP) and live stem C biomass increment at OA, whereas no significant relationships were found at OJP. Stem C increment accounted for 30% of total net primary productivity (NPP) at both sites, and NPP/GEP ratios were 0.36 and 0.32 at OA and OJP, respectively. Overall, this study found good agreement between eddy-covariance and biometric estimates of ecosystem C change at OA and OJP between 1994 and 2004. Over that period at OA, eddy-covariance estimates of photosynthesis captured the inter-annual variability in C uptake based on the growth of tree rings.

The boreal forest is one of the worlds largest forest biomes and comprises a major portion of the terrestrial carbon (C) sink. Quantifying the net C change in forest ecosystems is an important step in understanding and modeling the global C cycle. The goals of this project were: to estimate and compare the total change in ecosystem C over a 10-year period in two boreal forest stands using biometric and eddy-covariance approaches, and to evaluate the year-to-year changes in C uptake. This study utilized 10 years of eddy-covariance data and ecosys model data from the Old Aspen (OA) and Old Jack Pine (OJP) sites in central Saskatchewan, part of the Boreal Ecosystem Research and Monitoring Sites (BERMS). According to the eddy-covariance and C stock approaches, between 1994 and 2004 the net change in C storage at OA was 15.6 ± 4.0 and 18.2 ± 8.0 Mg C ha-1, respectively. At OJP, the 10-year net change in C storage from eddy-covariance was 5.8 ± 2.0 Mg C ha-1 in comparison to 6.9 ± 1.6 Mg C ha-1 from the carbon stock approach. While both sites were sinks of C between 1994 and 2004, the greatest increase in C occurred in different components - the forest floor at OA (14.6 Mg C ha-1) and in the living vegetation at OJP (8.0 Mg C ha-1). In 2004, total ecosystem C content was greater at OA (180.6 Mg C ha-1) than OJP (78.9 Mg C ha-1), with 50% (OA) and 39% (OJP) of the C in the detritus and mineral soil pools. During the 10-year period of eddy-covariance measurements, there was a positive correlation between both annual and growing season gross ecosystem photosynthesis (GEP) and live stem C biomass increment at OA, whereas no significant relationships were found at OJP. Stem C increment accounted for 30% of total net primary productivity (NPP) at both sites, and NPP/GEP ratios were 0.36 and 0.32 at OA and OJP, respectively. Overall, this study found good agreement between eddy-covariance and biometric estimates of ecosystem C change at OA and OJP between 1994 and 2004. Over that period at OA, eddy-covariance estimates of photosynthesis captured the inter-annual variability in C uptake based on the growth of tree rings.

Global warming and climate change are closely related to the amount of CO2 in the air. Forest ecosystem plays very important role in the global carbon cycle; CO2 from the atmosphere is taken up by vegetation and stored as plant biomass. Therefore, quantifying biomass and carbon sequestration in tropical forests has a significant concern within the United Nations Framework Convention on Climate Change (UNFCC), Kyoto Protocol and Reducing Emission from Deforestation and Forest Degradation (REDD) program for the purpose of the improvement of national carbon accounting as well as for addressing the potential areas for carbon credits, basis for payment for environmental services. The aim of research is to estimate biomass and carbon stocks in tropical forests using remote sensing data for dry forest of central highlands of Vietnam. This result showed that from satellite images of the SPOT, satellites could build the land cover map, carbon map and biomass map of Yok Don National Park, Central Highlands of Vietnam. Through which also the biomass (above ground biomass and below ground biomass) of each type of forest can be calculated. For instance the biomass of the dry forest (Dry Dipterocarp Forest) is 153.49 tones x ha-1, biomass of rich forest is 343.35 tones x ha-1, biomass of medium forest is 210.34 tones x ha-1 and biomass of poor forest & scrub are 33.56 tones x ha-1. / Sự ấm lên toàn cầu và biến đổi khí hậu có liên quan chặt chẽ với tổng lượng CO2 trong không khí. Hệ sinh thái rừng có vai trò rất quan trọng trong chu trình các bon toàn cầu; khí CO2 trong khí quyển được hấp thụ bởi thảm thực vật dưới dạng sinh khối. Vì vậy, việc xác định sinh khối và carbon tích trữ trong rừng nhiệt đới đã có được sự quan tâm đáng kể trong Công ước của Liên hiệp quốc về biến đổi khí hậu (UNFCC), Nghị định thư Kyoto và Chương trình giảm phát thải từ phá rừng và suy thoái rừng (REDD) gần đây, nhằm cho mục đích cải thiện việc tính toán lượng các bon tích trữ cũng như giải quyết các vấn đề tiềm năng cho tín dụng các bon, làm cơ sở cho việc thanh toán cho các dịch vụ môi trường. Mục đích của nghiên cứu này là ước lượng sinh khối và các bon lưu trữ trong các khu rừng nhiệt đới bằng cách sử dụng dữ liệu viễn thám, mà ở nghiên cứu này là cho rừng khộp Tây Nguyên của Việt Nam. Kết quả cho thấy rằng, từ ảnh vệ tinh SPOT có thể xây dựng bản đồ lớp phủ thực vật, bản đồ các bon và bản độ sinh khối của Vườn quốc gia Yok Đôn, Tây Nguyên Việt Nam. Qua đó đã tính toán được sinh khối (bao gồm cả trên mặt đất và dưới mặt đất) như: đối với sinh khối của rừng khô cây họ dầu (Dry Dipterocarp Forest) là 153,59 tấn/ha, sinh khối rừng giàu là 343,35 tấn/ha, sinh khối rừng trung bình là 210,34 tấn/ha và sinh khối rừng nghèo&cây bụi là 33,56 tấn/ha.

After the injection of CO₂ into a subsurface formation, various storage mechanisms help immobilize the CO₂. Injection strategies that promote the buoyant movement of CO₂ during the post-injection period can increase immobilization by the mechanisms of dissolution and residual phase trapping. In this work, we argue that the heterogeneity intrinsic to sedimentary rocks gives rise to another category of trapping, which we call local capillary trapping. In a heterogeneous storage formation where capillary entry pressure of the rock is correlated with other petrophysical properties, numerous local capillary barriers exist and can trap rising CO₂ below them. The size of barriers depends on the correlation length, i.e., the characteristic size of regions having similar values of capillary entry pressure. This dissertation evaluates the dynamics of the local capillary trapping and its effectiveness to add an element of increased capacity and containment security in carbon storage in heterogeneous permeable media. The overall objective is to obtain the rigorous assessment of the amount and extent of local capillary trapping expected to occur in typical storage formations. A series of detailed numerical simulations are used to quantify the amount of local capillary trapping and to study the effect of local capillary barriers on CO₂ leakage from the storage formation. Also, a research code is developed for finding clusters of local capillary trapping from capillary entry pressure field based on the assumption that in post-injection period the viscous forces are negligible and the process is governed solely by capillary forces. The code is used to make a quantitative assessment of an upper bound for local capillary trapping capacity in heterogeneous domains using the geologic data, which is especially useful for field projects since it is very fast compared to flow simulation. The results show that capillary heterogeneity decreases the threshold capacity for non-leakable storage of CO₂. However, in cases where the injected volume is more than threshold capacity, capillary heterogeneity adds an element of security to the structural seal, regardless of how CO₂ is accumulated under the seal, either by injection or by buoyancy. In other words, ignoring heterogeneity gives the worst-case estimate of the risk. Nevertheless, during a potential leakage through failed seals, a range of CO₂ leakage amounts may occur depending on heterogeneity and the location of the leak. In geologic CO₂ storage in typical saline aquifers, the local capillary trapping can result in large volumes that are sufficiently trapped and immobilized. In fact, this behavior has significant implications for estimates of permanence of storage, for assessments of leakage rates, and for predicting ultimate consequences of leakage. / text

Wetlands have been considered throughout millenniums as valuable assets due to the ecosystem services they provide for humans. However, previous research has shown that the value of wetlands has declined over the last 150 years, in parallel to the growth of agriculture. Today, society has realized the value of ecosystem services, through increased knowledge and awareness.This study focuses on the area of Byringe, 20 km southwest of Strängnäs. The aim of this study was to identify changes of wetland areas, wetland classes and ecosystem services over time. This study compared four maps covering the area, between the years 1714 to 2013. The results show that the wetland areas have increased from their initial coverage of 6.5% up to 24.4% today. This 17.9% increase corresponds to 115.3 ha. A closer examination of this 300-year transformation showed variation among the wetland classes. Marshlands showed the largest increase of 44.3ha, followed by fen with 33.5ha and bog 7.6ha. In some areas fen had been converted to bog, which is a change in carbon storage and thus climate regulation. The lakes had developed into marshland, which has caused the disappearance of fish stocks, negatively affecting the generation of food supply. The increased marshland area has also resulted in increased carbon storage and provisioning services such as fiber material from plants and bioenergy production from trees. Furthermore, the recent transformation of agricultural land into fen has generated a loss in food production services such as crops. Instead, other services have appeared in terms of climate regulation, flood protection, increased protection against erosion, water purification and support of biodiversity.

The objectives were to analyze the effect of different cropping systems and plants in succession to corn (Zea mays L.) on carbon storage and nitrogen and the carbon and nitrogen fractions of OM in experiment Long-term driven in a Red-Yellow, and evaluate the decomposition and nutrient release to soil the shoots of plant cover, placed in bags to decompose. We used an experimental system tracks under split plot design with three replications consisting of 12 treatments involving three management of soils (plots) - (CC - conventional tillage, CM - minimum tillage, NT - no-tillage) and four plants (subplots ) - (Commercial: peanut (Arachis hypogeae), bean (Phaseolus vulgaris) cover: (Cajanus cajan) and (Crotalaria juncea). The time of implementation of zero tillage and crop succession promote changes in C stocks and N in the depths. The absence and minimization of soil disturbance in PD and CM systems resulted in higher levels of C and N in humic fractions of OM Alfissol. The PD system was the largest contributor to the release of soil nitrogen, from the decomposing plant residues. The CM system had the highest rates of decomposition of soil carbon. We conclude that the management systems NT and MT may help to improve agricultural sustainability. / Os objetivos deste trabalho foram analisar o efeito de diferentes sistemas de cultivo e plantas em sucessão ao milho doce (Zea mays L.), no estoque de C e N do solo e sobre o teor de carbono e nitrogênio das frações da MO, em experimento de longa duração conduzido em um Argissolo Vermelho-Amarelo; e avaliar a decomposição e a liberação de nutrientes para o solo pela parte aérea de plantas de cobertura, colocadas em bolsas de decomposição. Utilizou-se um sistema de faixas experimentais sob parcelas subdivididas com três repetições, compostos por 12 tratamentos que associam três manejos de solos (parcelas)- (CC cultivo convencional, CM cultivo mínimo, PD plantio direto) e quatro plantas (subparcelas)- (comerciais: amendoim (Arachis hypogeae), feijão (Phaseolus vulgaris); cobertura: guandu (Cajanus cajan) e crotalária (Crotalaria juncea). O tempo de implantação do plantio direto e a sucessão de culturas promoveram alterações nos estoques de C e N nas profundidades avaliadas. A ausência e minimização do revolvimento do solo nos sistemas CM e PD favoreceu os maiores teores de C e N nas frações húmicas da M.O do Argissolo Vermelho Amarelo. O sistema PD foi o que mais contribuiu para a liberação de nitrogênio no solo, proveniente dos restos vegetais em decomposição. O sistema CM apresentou as maiores taxas de decomposição do carbono no solo. Conclui-se que os sistemas de manejo PD e CM podem contribuir para uma melhor sustentabilidade agrícola.

Seagrasses are considered highly important CO2 sinks, with the capacity to store substantial quantities of organic carbon in the living biomass and sediments, and thereby acting as a buffer against climate change. In this thesis, I have studied carbon storage variability in temperate and tropical seagrass habitats and identified factors influencing this variation. In addition, as seagrass areas are decreasing worldwide, I have assessed effects of different anthropogenic disturbances on carbon sequestration processes. The result from this thesis showed that there was a large variation in carbon storage within and among temperate, tropical and subtropical regions. The highest organic carbon stocks were found in temperate Zostera marina meadows, which also showed a larger carbon storage variability than the subtropical and tropical seagrass habitats. The tropical and subtropical seagrass meadows had inorganic carbon pools exceeding the organic carbon accumulation, which could potentially weakens the carbon sink function. The variability in organic carbon stocks was generally strongly related to the sediment characteristics of the seagrass habitats. In Z. marina meadows, the strength of the carbon sink function was mainly driven by the settings of the local environment, which in turn indicates that depositional areas will likely have higher organic carbon stocks than more exposed meadows, while in the tropics seagrass biomass was also influencing sedimentary carbon levels. Furthermore, locations with large areas of seagrass were associated with higher carbon storage in tropical and subtropical regions, which could be related to increased accumulation of both autochthonous and allochthonous carbon. In an in situ experiment, impacts on carbon sequestration processes from two types of disturbances (with two levels of intensity) were tested by simulating reduced water quality (by shading) and high grazing pressure (through removal of shoot biomass). At high disturbance intensity, reductions in the net community production and seagrass biomass carbon were observed, which negatively affected carbon sequestration and could impact the sedimentary organic carbon stocks over time. In the treatments with simulated grazing, erosion was also seen, likely due to an increase in near-bed hydrodynamics. When experimentally testing effects of increased current flow on organic carbon suspension in Z. marina sediment, a ten-fold release of organic carbon with higher current flow velocities was measured, which resulted in an increase in the proportion of suspended organic carbon by three times in relation to other sediment particles. Therefore, periods with enhanced hydrodynamic activity could result in a removal of organic carbon and thereby likely reduce the seagrass meadows’ capacity to store carbon. The findings of this thesis add to the emerging picture that there is a large natural variability in seagrasses’ capacity to store carbon, and highlight how human-induced disturbances could negatively affect the carbon sink function in seagrass meadows. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p>