Stormwater bioretention cells (BRCs) are a variety of green stormwater infrastructure with the potential to restore pre-urban water balance, provided they can be tailored to infiltrate and evapotranspire (i.e., harvest) urban runoff in proportions consistent with pre-urban hydrologic conditions. This paper evaluates their capacity to do so, focusing on evapotranspirative harvest, which is relatively understudied, and the capacity of CSR (Competitve, Stress-tolerant, and Ruderal) functional type to serve as an overarching framework characterizing the water use strategy of BRC plants. The goal is to determine if harvest (and therefore the ratio of urban runoff infiltrated to harvested; the I:H ratio) might be fine-tuned to meet pre-urban values in BRCs through informed manipulation of plant community composition. This study focuses on 3 critical plant water use traits, the turgor loss point, the point of incipient water stress, and maximum stomatal conductance. A global plant traits meta-analysis identified degree of plant competitiveness and stress tolerance as significant determinants of all three water use traits, with stem type (woody vs herbaceous) also being significant, but only for turgor loss point. Based on these results, six water use scenarios appropriate for plants with different CSR type/stem type combinations were developed. BRC plants spanning the range of CSR types necessary to actionize these scenarios were determined to be available in eight major climate zones of the coterminous US, suggesting that regulating plant water use in BRCs using CSR is likely feasible. Hydraulic simulations (Hydrus 1D) were conducted for each scenario in all eight climate zones and revealed significant differences in evapotranspirative harvest and I:H ratios in simulated BRCs. Competitive woody plants had the highest evapotranspiration and lowest I:H ratios; 1.5-1.8 times more evapotranspiration and a 1.6-2 times lower I:H ratio than stress tolerant herbaceous plants, on average, across climate zones. Despite these significant differences, no simulated BRC in any climate zone was capable of reproducing pre-urban I:H ratios, regardless of plant type. More water was infiltrated than harvested in all scenarios and climates with the inverse being true for all pre-urban conditions. This suggests that absent additional sources of harvest (e.g., use of BRC water for nonpotable purposes such as toilet flushing and outdoor irrigation, or adoption of novel BRC designs that promote lateral exfiltration, stimulating "extra" evapotranspiration from nearby landscapes), BRCs will be unable to restore pre-urban water balance on their own. If true, then using BRCs in combination with other green technologies (particularly those biased towards harvest), may be the best path forward for balancing urban water budgets. / Master of Science / Stormwater bioretention cells (BRCs) are a variety of green infrastructure designed to manage urban stormwater flows that can dramatically reduce the amount of stormwater that is rapidly (and unnaturally) conveyed from paved surfaces to ecosystems. Their ability to recreate natural flow conditions is dependent on them balancing rates of infiltration – slowly filtering water down to the water table – and evapotranspiration – letting plants capture and transpire water. This paper evaluates the extent to which different plant functional types (competitive, stress tolerant, and ruderal (weedy)) can be used to regulate this balance, bringing urban hydrologic conditions closer to pre-urban ones. Competitiveness and stress tolerance were found to significantly influence plant water use traits, as was plant stem type (woody vs herbaceous) to a lesser extent (i.e., managing water budgets using CSR functional type is theoretically possible). Published BRC vegetation guidelines in 8 major US climate zones were found to include both competitive and stress tolerant species (i.e., the range of functional types required to regulate BRC water balance exists, suggesting it is feasible). Finally, hydraulic simulations conducted under six plant water use scenarios (reflecting different CSR types and stem types) revealed significant differences in the ratio of water infiltrated to evapotranspired by BRCs (i.e., changing plant functional types can meaningfully influence BRC water balance). This said, the magnitude of this effect may be insufficient to return urban catchments to a pre-urban state. All BRCs infiltrated too much water in our simulations suggesting that absent additional sources of harvest (for instance., use of BRC water for nonpotable purposes such as toilet flushing or outdoor irrigation), BRCs will be unable to restore pre-urban water balance on their own. If true, then using BRCs in combination with other green technologies (particularly those biased towards harvest), may be the best path forward for balancing urban water budgets.

Orientador: Rafael Silva Oliveira / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-27T10:25:03Z (GMT). No. of bitstreams: 1 Muller_CarolineSignori_M.pdf: 1389363 bytes, checksum: 90f312d9e875f306ba1ded4eb5ff7c45 (MD5) Previous issue date: 2015 / Resumo: Diversos modelos climáticos predizem mudanças no regime hídrico e secas extremas nos mais variados ecossistemas, dentre esses, as florestas tropicais nebulares (FTNs), que são apontadas como ambientes sensíveis às mudanças no clima. Nas FTNs a frequência e intensidade de neblina são determinantes na composição da vegetação. As predições são de que o aquecimento terrestre causará um deslocamento da área atual de ocorrência de neblina para altitudes maiores, acima da maioria das FTNs do mundo. Com diminuição da neblina nesses ambientes é provável que ocorra um aumento da evapotranspiração e estresse hídrico da vegetação, podendo haver mortalidade das plantas. Em nosso estudo investigamos as relações hídricas de duas coníferas que ocorrem em FTNs A. angustifolia e P. lambertii, além disso avaliamos se o ponto de perda de turgor (?tlp) é um bom preditor de mortalidade para essas espécies. Para compreendermos os efeitos da neblina no status hídrico de A. angustifolia avaliamos duas populações em altitudes diferentes, sendo elas, montanha (1950 m) e vale (1500 m). Os indivíduos localizados na montanha mantiveram potenciais hídricos menos negativos do que os localizados no vale, durante todo o período de monitoramento. Conduzimos um experimento em casa de vegetação para avaliar a resistência a seca de A. angustifolia e P. lambertii. Também avaliamos a importância da absorção de água da neblina pelas folhas (AAF) e do aporte hídrico diretamente no solo na recuperação do status hídrico dessas espécies depois de submetidas à secas em que seu potencial hídrico foliar (?Folha) chegou ao ponto de perda de turgor (?tlp). As duas espécies apresentaram diferentes estratégias de manutenção do status hídrico, A. angustifolia foi mais resistente à seca, sobrevivendo por até 17 semanas de seca P. lambertii sobreviveu a 12 semanas de seca, no entanto, esta espécie apresentou maior capacidade de manutenção do ?Folha quando a única fonte de água foi à neblina. O ?tlp foi um bom preditor de mortalidade para essas duas espécies / Abstract: Several climate models predict changes in the water regime and extreme droughts in a wide variety of ecosystems. Among these ecosystems, there are the tropical montane cloud forests (TMCFs), pointed as sensitive environments to climate changes. Frequency and intensity of fog are crucial to the composition of vegetation in TMCFs. Predictions are that global warming will cause a shift in fog occurrence from the current area to higher altitudes, above most TMCFs in the world. With the fog decrease in these areas it is likely to occur an increase in the evapotranspiration and water stress of the vegetation, which may result in plant mortality. In this research we look into water relations of two conifers that occur in TMCFs, A. angustifolia and P. lambertii. Furthermore, it is evaluated if the turgor loss point (?tlp) is a good mortality predictor for these two species. To comprehend the fog effects in A. angustifolia's water status we evaluate two populations in different altitudes: mountain (1950m) and valley (1500m). Individuals located in the mountain kept water potentials less negative than the ones located in the valley throughout the monitoring period. An experiment was conducted in greenhouse to evaluate the resistance to drought of A. angustifolia and P. lambertii. Were also evaluated the importance of fog water uptake by leaves (LWU) and of water input directly into the ground in the water status recovery of the species after being subjected to drought in which their leaf water potential (?Leaf) reached the turgor loss point (?tlp). Both species presented different strategies of water status maintenance. A. angustifolia was more resistant to drought, surviving for up to 17 weeks of it, while P. lambertii survived for 12. However, P. lambertii showed higher capacity of ?Leaf maintenance when the only source of water was fog. Turgor loss point was a good mortality predictor for these two species / Mestrado / Biologia Vegetal / Mestra em Biologia Vegetal

La faible représentation de la biodiversité dans les modèles de végétation a longtemps été un obstacle à la compréhension et à la projection des processus écosystémiques. La forte biodiversité des forêts tropicales, leur rôle clé dans les cycles biogéochimiques globaux, ainsi que leur vulnérabilité aux perturbations anthropiques directes et indirectes, amplifient les difficultés et enjeux de ces questions de recherche. En particulier, l'augmentation prédite de la fréquence et de l'intensité des sécheresses pourrait impacter la structure et composition floristique de ces forêts, comme dors et déjà observé au cours d'expériences naturelles et artificielles. Cette thèse explore ces questions de recherche à travers deux approches complémentaires, de modélisation et de mesures écophysiologiques. Dans le premier chapitre, je décris un simulateur de croissance forestière individu-centré et spatialement-explicite, TROLL, qui intègre les progrès récents en physiologie des plantes. Les processus sont paramétrés à l'aide de traits fonctionnels espèce-spécifiques, pour une forêt tropicale amazonienne. Une régénération forestière est simulée, et validée par des observations faites en Guyane française. La sensibilité du modèle à plusieurs paramètres globaux clés est évaluée. Enfin, l'influence de la variation de la richesse et composition spécifiques sur les propriétés écosystémiques est explorée. La réponse des forêts tropicales à la sécheresse est mal connue, empêchant la représentation pertinente des processus en jeu dans les modèles de végétation. Les chapitres 2 à 5 de cette thèse ont ainsi pour but de documenter la tolérance à la sécheresse et sa diversité dans une forêt amazonienne. Une méthode récente et rapide de détermination d'un trait de tolérance des feuilles à la sécheresse, le potentiel hydrique des feuilles au point de perte de turgescence (ptlp), est validée et utilisée, permettant de quantifier pour la première fois un tel trait de tolérance à la sécheresse dans une forêt amazonienne à l'échelle de la communauté. Ce jeu de données permet l'exploration des déterminants de la tolérance à la sécheresse des feuilles, à travers les espèces d'arbres, les tailles des individus, les stades de succession, les expositions à la lumière, ainsi que les lianes. La variabilité de ptlp observée suggère une large diversité de réponses à la sécheresse au sein des communautés de plantes amazoniennes. Ceci est confirmé par le suivi direct du flux de sève au cours d'une saison sèche sur divers arbres de canopée. Enfin, je discute les implications de ces résultats pour le développement des futurs modèles de végétation. / A great part of uncertainties in our current understanding and projections of the carbon cycle lies in the vegetation compartment. The problem of biodiversity representation in vegetation models has long been an impediment to a detailed understanding of ecosystem processes. The high biodiversity of tropical forests, their disproportionate role in global biogeochemical cycles, together with their vulnerability to direct and indirect anthropogenic perturbations, amplify the relevance of this research challenge. In particular, the predicted increase in drought intensity and frequency in the tropics may impact forest structure and composition, as already observed in natural and artificial experiments. This thesis explores how new advances in modelling and ecophysiology should help improve our understanding of these processes in the future. In the first chapter, I describe an individual-based and spatially-explicit forest growth simulator, TROLL, that integrates recent advances in plant physiology. Processes are linked to species-specific functional traits parameterized for an Amazonian tropical rainforest. This model is used to simulate a forest regeneration, which is validated against observations in French Guiana. Model sensitivity is assessed for a number of key global parameters. Finally, we test the influence of varying the species richness and composition on ecosystem properties. Tropical forest response to drought is not well understood, and this hampers attempts to model these processes. In chapters 2 to 5 I aimed at documenting drought-tolerance and its diversity in an Amazonian forest. A rapid method of determination of a leaf drought tolerance trait, the leaf water potential at turgor loss point (ptlp), was validated and applied to a range of plant species. We established the first community-wide assessment of drought tolerance in an Amazonian forest. These results inform on the drivers and determinants of leaf drought tolerance, across tree species and lianas, tree size, successional stages, light exposition, and seasons. Variability in ptlp among species indicates the potential for a range of species responses to drought within Amazonian forest communities. This is further confirmed by direct monitoring of whole-plant water use on diverse canopy trees during a marked dry season. Finally, I discuss the implications of these results to increase the dialogue between the vegetation modeling community and ecology, to enhance model's predictive ability, and to inform policy choices.

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