Abstract Air temperatures in high-latitude regions are anticipated to rise by several degrees by the end of the century and result in substantial northward shifts of species. These changes will likely affect the source and sink dynamics of greenhouse gases and possibly lead to a net carbon release from high-latitude soils to the atmosphere. However, regional differences in carbon cycling depend highly on the vegetation community composition, which may be controlled by the abundance of herbivores. I investigated whether mammalian herbivores, mainly reindeer and rodents, alter ecosystem carbon storage through their impacts on vegetation and on dominant plant functional traits. I combined observations of recent changes in ecosystem carbon with experimental field manipulations of both herbivory and climate change and measured carbon storage in vegetation and soil, the uptake and release of carbon dioxide, microbial activity and compared these to plant community composition. Results of my PhD thesis show that under ambient conditions, the impacts of herbivory on both above- and belowground carbon storage ranged from positive to negative. Herbivory altered dominant plant functional traits and these were fairly good predictors of the changes in soil carbon. When combined with experimental warming, herbivory continued to exert control on the dominant plant functional traits but the strong effects of warming on ecosystem carbon storage mostly concealed the impact of herbivory. Interestingly, herbivory–nutrient interactions that were not linked to dominant functional traits determined the consequences of warming on soil carbon. Taken together, I show clear and site-specific impacts of herbivores on vegetation and ecosystem carbon storage and the processes that govern them. Therefore, I suggest that an improved understanding of the role of herbivory in the global carbon cycle could improve estimations of global carbon–climate feedbacks. / Tiivistelmä Vuosisadan loppuun mennessä arktisten alueiden lämpötilan odotetaan nousevan usealla asteella ja johtavan lajien siirtymiseen yhä pohjoisemmaksi. Nämä muutokset todennäköisesti muuttavat pohjoisten ekosysteemien kykyä vapauttaa ja sitoa ilmakehän hiiltä ja saattavat johtaa siihen, että yhä enemmän hiiltä vapautuu tundramailta ilmakehään. Kuitenkin paikallisesti hiilenkierto on riippuvainen kasviyhteisöstä ja erityisesti kasvien funktionaalisista ominaisuuksista. Väitöskirjassani tutkin, voivatko herbivorit, pääasiassa porot sekä jyrsijät, muokata hiilenkiertoa muuttamalla kasvillisuutta. Tutkimuksissani seurasin kuinka alueen laidunnushistoria on muokannut hiilivarastoja ja hiilenkiertoa tällä hetkellä ja pyrin arvioimaan herbivorien vaikutusta lämpenevässä ilmastossa kokeiden avulla, joissa manipuloidaan sekä herbivoriaa että lämpötilaa tai ravinteiden saatavuutta. Tulokseni perustuvat arvioihin hiilen varastoista, hiilidioksidin vapautumisesta ja sitoutumisesta sekä mikrobien aktiivisuudesta, joita vertaan kasviyhteisöön. Tulokseni osoittavat, että herbivoria voi joko lisätä tai vähentää ekosysteemin hiilivarastoja sekä maan päällä että maan alla. Muutokset hiilivarastoissa selittyivät varsin hyvin herbivorien tuottamilla kasvillisuusmuutoksilla ja valtalajien funktionaalisilla ominaisuuksilla. Herbivoria muokkasi kasviyhteisöä myös kokeellisen lämmityksen yhteydessä, mutta lämmityksen välittömät vaikutukset hiilivarastoihin peittivät suureksi osaksi alleen herbivorian vaikutukset. Kuitenkin herbivorian ja lannoituksen kasvillisuusmuutoksista riippumattomat yhdysvaikutukset määrittivät lämpenemisen seuraukset maan hiileen. Kaiken kaikkiaan, tutkimukseni osoittaa, että herbivorit voivat paikkakohtaisesti muokata kasvillisuutta, ekosysteemin hiilivarastoja sekä hiilenkierron prosesseja. Näiden tulosten myötä ehdotan, että parempi ymmärrys herbivorian vaikutuksista maailmanlaajuisesti voisi parantaa nykyisiä ennusteita siitä, kuinka ilmaston lämpeneminen muuttaa hiilenkiertoa.

Satellite geodesy plays an important role in earth observation. This dissertation presents three applications of satellite geodesy in environmental and climate change. Three satellite geodesy techniques are used: high-precision Global Positioning System (GPS), the Gravity Recovery and Climate Experiment (GRACE) and Interferometric Synthetic Aperture Radar (InSAR). In the first study, I use coastal uplift observed by GPS to study the annual changes in mass loss of the Greenland ice sheet. The data show both spatial and temporal variations of coastal ice mass loss and suggest that a combination of warm atmospheric and oceanic condition drove these variations. In the second study, I use GRACE monthly gravity change estimates to constrain recent freshwater flux from Greenland. The data show that Arctic freshwater flux started to increase rapidly in the mid-late 1990s, coincident with a decrease in the formation of dense Labrador Sea Water, a key component of the deep southward return flow od the Atlantic Meridional Overturning Circulation (AMOC). Recent freshening of the polar oceans may be reducing formation of Labrador Sea Water and hence may be weakening the AMOC. In the third study, I use InSAR to monitor ground deformation caused by CO2 injection at an enhanced oil recovery site in west Texas. Carbon capture and storage can reduce CO2 emitted from power plants, and is a promising way to mitigate anthropogenic warming. From 2007 to 2011, ~24 million tons of CO2 were sequestered in this field, causing up to 10 MPa pressure buildup in a reservoir at depth, and surface uplift up to 10 cm. This study suggests that surface displacement observed by InSAR is a cost-effective way to estimate reservoir pressure change and monitor the fate of injected fluids at waste disposal and CO2 injection sites.

Forests in developing countries have the potential to contribute to global efforts to mitigate climate change, promote biodiversity and support the livelihoods of rural, local people. Approximately one-fourth of such forests are under the control of local communities, which primarily manage forests for subsistence and to meet their livelihood needs. The trend of bottom-up community control is increasing through the adoption of decentralization reforms over the last 40 years. In contrast, the United Nations has introduced the top-down program, Reducing Emissions from Deforestation and Forest Degradation (REDD+) for the conservation and enhancement of forest carbon and the sustainable management of forest in developing countries. REDD+ incentivizes forest-managing communities to sequester carbon and reduce emissions. REDD+ has created hope for managing forests to mitigate climate change and has created fear that the new initiative may not be effective and may not ensure continuing forest-managing community benefits. However, little research has been conducted to answer these concerns. By taking nationally representative data from Nepalese community-managed forests (“forest commons"), I bring insights into whether and how these forests can contribute to REDD+ initiatives, particularly as they relate to carbon sequestration, biodiversity, equity in benefit sharing and collective action. My results indicated the highly variable carbon and biodiversity in the forest plots across the country, depicting the availability of space for additional growth in carbon storage and biodiversity conservation. My results also reflect the complex and varied relationships of carbon with different indices of biodiversity at the national level, across geographic and topographic regions, and in forests with varying canopy covers. Weak positive relationships between carbon sequestration and biodiversity conservation indicate the possibility of synergies between carbon-forestry and biodiversity conservation. I also found that the formal community forestry program (CFP) has clearly positive impacts on biodiversity conservation and household-level equity in benefit sharing and a negative impact on carbon sequestration at the national level. However, disaggregated results of impacts of CFP on biodiversity, carbon and equity across geography, topography, forest quality and social groups display mixed results i.e., either positive or negative or neutral. I also identified that different drivers of collective action have different (i.e., positive, neutral, and negative) associations with carbon sequestration, which either supports or challenges established knowledge. In aggregate, my research indicates the potential of contribution by forest commons, and specially the CFP, to global environmental initiatives such as REDD+. It suggests that targeted, dedicated policies and programs to increase carbon sequestration, biodiversity conservation and foster equity and collective actions are critical. In addition, my results also contribute to the growing literature on socio-ecological implications of forest commons that demonstrated the need of interdisciplinary research to understand human-nature relationships in the changing context.

Indiana University-Purdue University Indianapolis (IUPUI) / The shale and mudstone directly superjacent to Desmoinesian coal seams of southern Indiana (Springfield, Houchin Creek, Survant, and Seelyville coals) were initially deposited under marine waters and are shown to exhibit high concentrations of organic carbon, sulfur and redox-sensitive metals (Mo, V, Ni, Fe, and U) that were sequestered during times of benthic anoxia and intermittent to sustained euxinia (anoxic and sulfidic). Strata upsection display geochemical signatures that indicate increasingly oxic and nearshore sedimentation that mirrors cyclothemic sequence stratigraphic trends Carbon source, nearshore and offshore proximity, freshwater and marine influence, and redox conditions of the epeiric sea overlying southern Indiana during the Late Middle Pennsylvanian were identified and tracked throughout the deposition of four drill cores of the Petersburg, Linton and Staunton Formations. Carbon, nitrogen, and sulfur data (total organic carbon [TOC], total nitrogen [TN], and total sulfur [TS]); paleoredox proxies ([Mo/Al], [V/Al], [Th/U], [Fetot/Al]); organic carbon isotopes (δ13Corg); and detrital influx concentrations (Zr) were all used in conjunction with lithological and paleontological interpretations to better understand the mode of deposition in this unique midcontinent ancient epeiric sea. Geochemical results when combined with lithologic and paleontologic interpretations reveal a dynamic environmental system where water column geochemistry varies with the influence of variable magnitudes of epeiric seawater flooding on the extensive peatlands of equatorial Late Middle Pennsylvanian southern Indiana.

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För klimatet spelar skogen en viktig roll eftersom den binder in koldioxid från atmosfären. Genom fotosyntes binds kolet in i biomassan och när organiskt material bryts ned bidrar det till kolinlagringar i marken. Idag finns det många studier om skogens kolinlagringar, men de undersöker endast nettoinbindningen av kolet i skogen och få studier visar hur mycket kol som totalt är inlagrat i en skog. Det finns inga studier om hur det ser ut i Sverige och det finns få studier som visar på skillnaden i kolinlagring mellan en produktionsskog och en urskog. I den här litteraturstudien presenterar jag hur mycket kol som är inbundet i den svenska skogen och hur det skiljer sig mellan produktionsskog och urskog. Genom att applicera data från en studie som undersökte hur mycket kol som är inbundet i skogen i Kanada på den svenska skogen kom jag fram till att det finns totalt mellan 5 413 och 6 798 miljoner ton kol inlagrat i den svenska skogen, men mer kol skulle kunna lagras. Medelåldern för när träd slutavverkas är i Sverige 101 år. Jag kom fram till att det lagras in ungefär 53 till 75 ton mer kol per hektar i en skog som är äldre än 140 år än i en skog som är mellan 101 och 120 år. Resultatet visar att det binds in mer kol i en urskog än i en produktionsskog och att det är viktigt att bevara de urskogar som idag finns för att kunna möta de klimatproblem vi står inför. / For the climate, the forest plays an important role because it binds carbon dioxide from the atmosphere. Through photosynthesis, carbon is bound into the biomass and degradable organic material contributes to carbon storage in the soil. There are many studies on the forest carbon deposits, but they only examine the net binding of carbon, and few studies show how much carbon is stored in total. There are no studies on what carbon storage looks like in Sweden and few studies that show the difference in carbon storage between production forests and old-growth forests. In this literature study, I present how much carbon is bound in Swedish forests and how it differs between production forest and old-growth forest. By applying data from a study that examined how much carbon is bound in Canadian forests on Swedish forests, I concluded that there is a total of between 5 413 and 6 798 million tonnes of carbon stored in Swedish forests, but more carbon could be stored. In Sweden, the average age for when trees are felled is 101 years. I concluded that approximately between 53 and 75 tonnes more carbon per hectare is stored in a forest that is older than 140 years than in a forest that is between 101 and 120 years. The results show that more carbon is bound in an old-growth forest than in a production forest and that it is important to preserve the old-growth forests to reduce the climate problems we face.