La végétation aquatique submergée (VAS) est une composante essentielle qui structure les écosystèmes aquatiques continentaux. Elle soutient plusieurs fonctions et services écosystémiques, dont le soutien d’habitats pour la faune, la stabilisation du rivage, le maintien d’une eau claire et la régulation des cycles des nutriments. Cependant, la VAS est soumise aux activités humaines qui modifient leur habitat, altère leur quantité et menacent le maintien de ces services. L’objectif de cette thèse est de mieux comprendre comment les quantités de la VAS répond aux variations environnementales et quels sont les effets de ces modifications sur les fonctions et services qu’elle soutient. Cet objectif est abordé de différents angles d’attaque et à différentes échelles spatiales et temporelles. Tout d’abord, une nouvelle méthode permettant des économies de temps et d’argent pour mesurer la biomasse de la VAS est proposée. À l’aide de deux modèles de calibration, la méthode combine trois techniques existantes couramment utilisées pour estimer la biomasse de la VAS : le prélèvement de biomasse dans des quadrats en plongée, le prélèvement à l’aide d’un râteau manié depuis la surface et l’échosondage à partir d’une embarcation. Cette approche offre l’avantage de limiter l’utilisation risquée et fastidieuse du quadrat avec plongeur, mais fournissant la mesure de biomasse la plus fiable. La première calibration avec le quadrat permet d’utiliser le râteau et corrige son biais, alors que la deuxième calibration entre râteau et échosondage convertit les valeurs mesurées par cette dernière en biomasse. L’utilisation de l’échosondage permet ainsi d’estimer plus rapidement la biomasse à grande échelle. La méthode est validée à partir de données d’échosondage qui sont confrontées avec des biomasses par quadrat, démontrant la robustesse de l’approche. Ensuite, les variations climatiques interannuelles et leurs effets sur la rétention de l’azote ont été évalués pendant six étés dans un herbier aquatique à la confluence de deux tributaires agricoles avec le fleuve Saint-Laurent. Des budgets d’azote journalier ont été estimés par la différence entre les concentrations modélisées de nitrate dans les tributaires et les concentrations sortantes de l’herbier mesurées par une sonde à haute fréquence. La rétention totale a été partitionnée en assimilation autotrophe et en dénitrification à partir de la variation diurne en nitrate. Les budgets ont été confrontés à un indice de biomasse de VAS, la pente de la surface du niveau de l’eau, qui a révélé un portrait détaillé de l’évolution de la biomasse au cours de la saison de croissance. Les résultats montrent que la rétention est influencée par les variations de niveau de l’eau, de température, de biomasse de la VAS et d’apports en nitrate. De hauts taux de consommation de nitrate sont rapportés, parmi les plus élevés mesurés en rivière, avec une biomasse accrue de plantes accrue favorisant l’élimination permanente par la dénitrification. Enfin, une synthèse sur les tendances, les facteurs globaux déterminant les quantité de VAS dans les lacs ainsi que comment les quantité y ont été mesurées est présentée. La compilation a été effectuée à l’aide d’une recherche par mot clés réalisée sur une base de données bibliographiques. La synthèse montre un portrait dynamique dans le temps et dans l’espace des quantités de VAS. Bien que les déclins de quantités soient prédominants, plusieurs séries temporelles récentes indiquent une récupération de la VAS, patrons qui varient selon les régions et les activités humaines. Les usages dans les bassins versants liés à l’eutrophisation sont associés aux déclins, particulièrement en Asie, alors que les augmentations sont surtout associées à la gestion de la VAS en Europe. Les tendances plus variables en Amérique du Nord sont associées à l’arrivée d’espèces envahissantes. Cette thèse innove en fournissant une nouvelle méthode qui facilite la mesure de la biomasse de la VAS à grande échelle. Elle contribue également aux connaissances sur la VAS et le cycle de l’azote en grande rivière en caractérisant la variation de la rétention de nitrate et en soulignant leur important rôle comme site de transformation dans ces écosystèmes. Finalement, elle contribue à la biogéographie de la VAS continentale dans les lacs, indique des lacunes de connaissance, souligne les développements méthodologiques souhaitables et informe sur l’influence de facteurs expliquant la variation de la VAS qui seront utiles pour sa gestion future. Ces informations seront profitables au maintien des fonctions et services soutenus par la VAS et à son utilisation comme une solution fournie par la nature face aux changements globaux. / Submerged aquatic vegetation (SAV) is an essential component that structures inland waters. SAV sustains numerous ecosystem services and functions, such as providing habitat for fauna, stabilizing shoreline, maintaining clear water and regulating nutrient cycles. However, SAV is submitted to human activities that modify their habitat, alter their quantities and threaten the ecosystem services they may provide. The objective of this thesis is to better understand how SAV quantities responds to environmental variations, and what are the effect of these modifications on the functions and services they sustain. This objective is approached in different ways and at various spatial and temporal scales. First, a new cost-effective method to measure SAV biomass is proposed. The method combines three existing techniques by means of two calibration models. This approach has the advantage of reducing the hazardous and cumbersome use of quadrats with divers, whilst providing the most accurate biomass measure. The first calibration with the quadrat allows for the application of the rake and corrects for its bias, while the second calibration between rake and echosounding converts the values measured by the latter into biomass. The use of echosounding thus allows for the estimation of biomass more rapidly at larger scale. The method is validated from echosounding data that are compared to quadrat biomasses, demonstrating the robustness of the approach. Second, interannual climate variation and their effect on nitrogen retention were evaluated during six summers in a SAV meadow at the confluence zone of two agricultural tributaries with the Saint Lawrence River. Daily nitrogen budgets were estimated as the difference between modelled nitrate concentration in the tributaries and concentration outflowing the SAV meadow measured with a high frequency sensor. Total retention was partitioned into autotrophic assimilation and denitrification from the diel nitrate variation. The budgets were compared to an indicator of SAV biomass, the slope of water level surface, which provided a detailed portrait of biomass changes throughout the growing season. The results show that retention is influenced by variation in water levels, temperature, SAV biomass and nitrate inputs. Among the highest nitrate uptake rates are reported compared to previous measurements in inland waters, with plant biomass favoring permanent removal through denitrification. Third, a synthesis on trends and drivers of SAV quantities in lakes, as well as on how it was measured is presented. The compilation was conducted from a keyword search on a bibliographic database. The synthesis shows a dynamic depiction in space and time of SAV quantities. Although decreasing quantities are predominant, many recent time series indicate SAV recovery, and these patterns vary with regions and human activities. Direct activities in watersheds leading to eutrophication are associated with decreases, particularly in Asia, while increases are more associated with SAV management in Europe. Trends are more variable in North America due to invasive species. This thesis innovates by providing a new method facilitating SAV biomass measurement at large scale. The thesis also contributes to knowledge on SAV and on nitrogen cycling in large rivers by characterizing the variation in nitrate retention. Finally, the thesis contributes to inland SAV biogeography, identifies knowledge gaps, indicates desirable methodological developments and informs on drivers of SAV that could inform its future management. This information will be beneficial for the preservation of the ecosystem services and functions provided by SAV and its use as a nature-based solution against global changes.

Tesis por compendio / [ES] Los servicios ecosistémicos de montaña han adquirido importancia entre los científicos, los administradores y los encargados de formular políticas de todo el mundo; sin embargo, las actividades humanas están amenazando su conservación, en particular los cambios en el uso del suelo debido al aumento de la urbanización, la expansión agrícola y la deforestación. La Puna Altoandina es un ecosistema montañoso representativo que enfrenta estos serios y crecientes desafíos. La Puna Altoandina, cuyos principales socioecosistemas consisten en pastizales naturales, matorrales y zonas agrícolas, puede proporcionar múltiples servicios ecosistémicos influenciados por el tipo de cobertura terrestre y sus dinámicas. En este contexto, se han explorado las dinámicas entre los usos representativos de la superficie terrestre y su potencial para proporcionar servicios ecosistémicos en la Puna húmeda Altoandina a lo largo del tiempo. Asimismo, se ha completado un análisis espacio-temporal que describe cómo diferentes patrones de 6 dinámicas de cambio del uso del suelo impactan en la provisión de 7 servicios ecosistémicos durante un período de 13 años (de 2000 a 2013), y en el territorio de 25 provincias. Además, con el fin de mejorar la gestión de los servicios ecosistémicos, abordamos los efectos de aplicar dos análisis "clúster" (estáticos y dinámicos) para evaluar los conjuntos de servicios ecosistémicos en cuatro escalas de observación diferentes (dos ámbitos administrativos y dos tamaños de pixel geográfico: 0.25 y 9 km2). En general, este estudio proporciona un enfoque para facilitar la incorporación de los servicios ecosistémicos a múltiples escalas que permite una interpretación fácil del desarrollo de la región y que puede contribuir a mejorar las acciones para la gestión del uso del suelo y las decisiones de política ambiental. / [CA] Els serveis ecosistèmics muntanya han adquirit importància entre els científics, els administradors i els encarregats de formular polítiques de tot el món; no obstant això, les activitats humanes estan amenaçant la seua conservació, en particular els canvis en l'ús del sòl a causa de l'augment de la urbanització, l'expansió agrícola i la desforestació. La Puna Altoandina és un ecosistema muntanyenc representatiu que enfronta aquests seriosos i creixents desafiaments. La Puna Altoandina que els seus principals soci-ecosistemes consisteixen en pasturatges naturals, matolls i zones agrícoles, pot proporcionar múltiples serveis ecosistèmics influenciats per les diferents categories de cobertura terrestre y els seus dinàmiques. En aquest context, s'han explorat les dinàmiques entre els usos representatius de la superfície terrestre i el seu potencial per a proporcionar serveis ecosistèmics en la Puna humida Altoandina al llarg del temps. Així mateix, s'ha completat una anàlisi espai-temporal que descriu com diferents patrons de 6 dinàmiques de canvi de l'ús del sòl impacten en la provisió de 7 serveis ecosistèmics durant un període de 13 anys (de 2000 a 2013), i en el territori de 25 províncies. A més, amb la finalitat de millorar la gestió dels serveis ecosistèmics, abordem els efectes d'aplicar dues anàlisis "clúster" (estàtics i dinàmics) per a avaluar els conjunts de serveis ecosistèmics en quatre escales d'observació diferents (dos àmbits administratius i dues grandàries de píxel geogràfic: 0.25 y 9 km2). En general, aquest estudi proporciona un enfocament per a facilitar la incorporació dels serveis ecosistèmics a múltiples escales que permet una interpretació fàcil del desenvolupament de la regió i que pot contribuir a millorar les accions per la gestió de l'ús del sòl i les decisions de política ambiental. / [EN] Mountain ecosystem services have gained relevance among scientists, managers, and policy-makers worldwide; but, human activities are threatening its conservation, particularly land changes due to increased urbanization, agricultural expansion and deforestation. The high-Andean Puna is a representative mountain ecosystem that is facing these serious and growing challenges. The high-Andean Puna, whose main socialecosystems consist of natural grassland, shrubland and agricultural areas, can provide multiple regulating ecosystem services influenced by the land cover/use type and their dynamics. In this context, we explored the dynamics between the representative land-cover classes and its potential to provide ecosystem services in the high-Andean moist Puna over time. We completed a spatiotemporal analysis that describes how different patterns of 6 landchange dynamics impact on the supply of 7 ecosystem services over a period of 13 years (from 2000 to 2013), and across 25 provinces. Moreover, in order to improve the management of ecosystem services, we addressed the effects of applying two cluster analyses (static and dynamic) for assessing bundles of ecosystem services across four different scales of observation (two administrative boundaries and two sizes of grids: 0.25 and 9 km2). Overall, this study provides an approach to facilitate the incorporation of ES at multiple scales allowing an easy interpretation of the region development that can contribute to land management actions and policy decisions. / Madrigal Martínez, S. (2021). Land-change dynamics and ecosystem services using expert-based assessment and GIS: methodological implications for improving decision-making [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/172369 / Compendio

Biological invasions provide a unique opportunity to study the mechanisms that regulate community composition and ecosystem function. Invasive species that are also ecosystem engineers can substantially alter physical features in an environment, and this can lead to cascading effects on the biological community. Aquatic-terrestrial interface ecosystems are excellent systems to study the interactions among invasive ecosystem engineers, physical features, and biological communities, because interactions among vegetation, sediment, and fluids within biophysical feedbacks create and modify distinct physical features. Further, these systems provide important ecosystem services including coastal protection afforded by their natural features. In this dissertation, I investigate the interactions and feedbacks among sand-binding beach grass species (a native, Elymus mollis (Trin.), and two non-natives, Ammophila arenaria (L.) Link and A. breviligulata Fernald), sediment supply, and dune shape along the U.S. Pacific Northwest coast. Dunes dominated by A. arenaria tend to be taller and narrower compared to the shorter, wider dunes dominated by A. breviligulata. These patterns suggest an ecological control on dune shape, and thus, coastal vulnerability to overtopping waves. I investigate the causes and consequences of these patterns with experiments, field observations, and modeling. Specifically, I investigate the relative roles of vegetation and sediment supply in shaping coastal dunes over inter-annual and multi-decadal time scales (Chapter 2), characterize a biophysical feedback between beach grass species growth habit and sediment supply (Chapter 3), uncover the mechanisms leading to beach grass coexistence and whether A. breviligulata can invade and dominate new sections of coastline (Chapter 4), and examine the non-target effects resulting from management actions that remove Ammophila for the recovery of the threatened Western Snowy plover (Charadrius alexandrinus nivosus) (Chapter 5). I found that vegetation and sediment supply play important roles in dune shape changes across inter-annual and multi-decadal time scales (Chapter 2). I determined that a biophysical feedback between the beach grass growth habits and sediment supply results in species-specific differences in sand capture ability, and thus, is a likely explanation for differences in dune shape (Chapter 3). I found that all three beach grass species can coexist across different sediment deposition rates, and that this coexistence is largely mediated by positive direct and indirect species interactions. I further determined that A. breviligulata is capable of invading and dominating the beach grass community in regions where it is currently absent (Chapter 4). Combined, these findings indicate that A. breviligulata is an inferior dune building species as compared to A. arenaria, and suggest that in combination with sediment supply gradients, these species differences ultimately lead to differences in dune shape. Potential further invasions of A. breviligulata into southern regions of the Pacific Northwest may diminish the coastal protection ability of dunes currently dominated by A. arenaria, but this effect could be moderated by the predicted near co-dominance of A. arenaria in these lower sediment supply conditions. Finally, I found that the techniques used to remove Ammophila for plover recovery have unintended consequences for the native and endemic dune plant communities, and disrupt the natural disturbance regime of shifting sand. A whole-ecosystem restoration focus would be an improvement over the target-species approach, as it would promote the return of the natural disturbance regime, which in turn, would help recover the native biological community. The findings from this dissertation research provide a robust knowledge base that can guide further investigations of biological and physical changes to the coastal dunes, can help improve the management of dune ecosystem services and the restoration of native communities, and can help anticipate the impacts of future beach grass invasions and climate change induced changes to the coast. / Graduation date: 2012 / Access restricted to the OSU Community at author's request from Sept. 22, 2011 - March 22, 2012

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Increasingly unpredictable, extreme and erratic rainfall with higher temperatures threatens to undermine the adaptive capacity of food systems and ecological resilience of smallholder landscapes. Despite growing concern, land managers still lack quantitative techniques to collect empirical data about the potential impact of climatic variability and change. This thesis aims to assess how ecosystem services and function and how this links with biodiversity and human wellbeing in smallholder agro-ecosystems in a changing climate. To this end, rather than relying on scenarios or probabilistic modelling, space was used as a proxy for time to compare states in disparate climatic conditions. Furthermore, an integrated methodological framework to assess ecosystem services at the field and landscape level was developed and operationalised, the results of which can be modelled with measures of wellbeing. Various multidisciplinary analytical tools were utilised, including ecological and socio-economic surveys, biological assessments, participatory open enquiry, and documenting ethnobotanical knowledge. The study was located within monsoon rice farms in the Terai Plains of Nepal, and dry season vegetable farms in Northern Ghana. Sites were selected that are climatically and culturally diverse to enable comparative analysis, with application to broad areas of adaptive planning. The linkages that bring about biophysical and human changes are complex and operate through social, political, economic and demographic drivers, making attribution extremely challenging. Nevertheless, it was demonstrated that within hotter and drier conditions in Ghana long-tongued pollinators and granivores, important for decomposition processes and pollination services, are more abundant in farms. Results further indicated that in cooler and drier conditions in Nepal, the taxonomic diversity of indigenous and close relative plant species growing in and around farms, important for the provisioning of ecosystem services, decreases. All other things equal, in both Nepal and Ghana findings indicate that overall human wellbeing may be adversely effected in hotter conditions, with a potentially significantly lower yields, fewer months of the year in which food is available, higher exposure to natural hazards and crop loss, unemployment, and psychological anxiety. Yet, surveys indicate smallholders continue to maintain a fair diversity of species in and around farms, which may allow them to secure basic necessities from provisioning ecosystem services. Moreover, farmers may employ adaptive strategies such as pooling labour and food sharing more frequently, and may have greater access to communication, technology, and infrastructure. Novel methodological and empirical contributions of this research offer predictive insights that could inform innovations in climate-smart agricultural practice and planning.