Live eastern oyster (Crassostrea virginica) reefs have declined by 62.6% in Mosquito Lagoon (ML) along the eastern Florida coast since 1943. While this species creates reefs by successive generations of oysters recruiting to conspecific shells, C. virginica can also attach to non-reef substrates including mangrove roots and armoring (e.g., seawalls), which may help counteract reef habitat loss. In recent decades, warmer winters have enabled red (Rhizophora mangle) and black (Avicennia germinans) mangrove expansion in subtropical salt marshes and temperate estuaries where oyster reefs occur. Additionally, 11.8% of ML's shorelines have been armored as of 2018. These non-reef substrates add potential surface area and a 3-D substrate for oyster settlement. Aerial imagery from 1984 to 2021 was used to track extent (ha) changes in mangroves, oyster reefs, and hard armoring. Mangrove extent increased 859.2%, hard-armoring extent decreased 56.3%, and live oyster reef area decreased 55.3% (rate: -0.86 ha/yr). Additionally, 83 oyster reefs were 100% converted into mangrove islands, resulting in a 654.6% increase in the number of new conversions between 1984 and 2021. To determine if oyster abundances on non-reef substrates are comparable to live oyster reefs, oyster characteristics were compared between substrate types using field surveys to collect metrics (live densities, shell heights, canopy heights). Mean densities and canopy heights (± S.E.) were highest on concrete/metal seawalls (481.8 ± 113.0 oysters m2 and 678.4 ± 408.6 mm, respectively). Mean shell heights (± S.E.) were largest on oyster reefs (52.0 ± 2.2 mm) and within black mangrove pneumatophores on oyster reefs (41.3 ± 10.0 mm). Between 1984 and 2021, oyster reefs lost 291.0 oysters/ha versus non-reef habitats, which added an average (± S.E.) of 104.7 ± 78.2 oysters/ha. These findings suggest mangrove roots and armoring support oyster reef-level populations by providing 3-D attachment space and partially offset oyster losses on reefs.

Submitted by Edisangela Bastos (edisangela@ufpa.br) on 2017-01-26T12:31:23Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Tese_RiquezaAbundanciaGalhas.pdf: 1731686 bytes, checksum: 8a75371df36ba2f7144781dcf3edef86 (MD5) / Approved for entry into archive by Edisangela Bastos (edisangela@ufpa.br) on 2017-01-26T12:31:57Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Tese_RiquezaAbundanciaGalhas.pdf: 1731686 bytes, checksum: 8a75371df36ba2f7144781dcf3edef86 (MD5) / Made available in DSpace on 2017-01-26T12:31:57Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Tese_RiquezaAbundanciaGalhas.pdf: 1731686 bytes, checksum: 8a75371df36ba2f7144781dcf3edef86 (MD5) Previous issue date: 2011 / IIEB - Instituto Internacional de Educação do Brasil / FAPESPA - Fundação Amazônia de Amparo a Estudos e Pesquisas / A maioria dos estudos sobre herbivoria em ecossistemas de manguezal tem focalizado primariamente nos herbívoros mastigadores, a despeito da relativa riqueza de herbívoros endofíticos, principalmente indutores de galhas e minadores. Das 29 espécies de artrópodos indutores de galhas, associados a manguezais, sete espécies já foram formalmente descritas a partir de espécies de Avicennia L. (Acanthaceae). Este gênero é formado por dez espécies e possui distribuição pantropical. A. germinans (L.) Stearn é a principal espécie hospedeira de artrópodos indutores de galhas no manguezal da península de Ajuruteua em Bragança, Pará. Em um primeiro levantamento de galhadores nesta região, foram identificados 14 morfotipos de galhas (sete destes pertencentes à família Cecidomyiidae: Insecta: Diptera). Em função do elevado número de morfotipos de galhas identificados colonizando A. germinans, esta espécie foi apontada como uma superhospedeira de organismos indutores de galhas. A incidência de galhas sobre as espécies arbóreas (A. germinans, L. racemosa e R.mangle) típicas dos manguezais da península de Ajuruteua, foi investigada. Os espécimes de A. germinans foram avaliados quanto à infestação por galhas tanto sob condições normais de salinidade quanto sob estresse salino. O trabalho de campo foi realizado em quatro sítios de trabalho: Furo do Taici, Km17, Bosque Anão de A. germinans e Furo do Café. Um total de 1.575 folhas foi examinado, sendo 525 para cada uma das espécies de mangue registradas nessa área. A. germinans apresentou 2.221 galhas, com incidência de 1,4 galhas por folha. O Bosque Anão de A. germinans foi o que apresentou o mais alto valor de salinidade. A alta salinidade verificada nesta área implicou em baixo desenvolvimento das plantas (nanismo), diminuição da área foliar e aumento da esclerofilia, características estas que parecem favorecer a infestação por herbívoros galhadores. A riqueza e abundância de galhadores também foram avaliadas em quatro estádios ontogenéticos de Avicennia germinans. A arquitetura das plantas se constitui em um dos fatores determinantes na associação entre os insetos indutores de galha e suas respectivas plantas hospedeiras. Partindo desse pressuposto, testou-se a “hipótese da arquitetura da planta” que prediz uma correlação positiva entre a riqueza de espécie de galhadores e a complexidade estrutural das plantas, como resultado de um processo de sucessão ontogenética. Para a análise da complexidade estrutural dessa espécie de mangue, as seguintes variáveis foram utilizadas: altura, número total de folhas e número total de folhas galhadas, as quais foram correlacionadas com a riqueza e a abundância de galhas. Os estádios de desenvolvimento para A. germinans foram determinados de acordo com a altura dos indivíduos: 1 o estádio (8 a 30 cm; n=31); 2 o estádio (31 a 60 cm; n=13); 3 o estádio (61 a 150 cm; n=09) e 4 o estádio (151 a 300 cm; n=10). Um total de 63 indivíduos e 7.608 folhas foi analisado. As características estruturais da planta foram positivamente e significativamente correlacionadas com a abundância e riqueza de galhas nos quatro estádios de desenvolvimento. Os resultados para Avicennia germinans mostram que esse tipo de herbivoria começa nos estádios iniciais do desenvolvimento do indivíduo, isto é, ainda na fase de plântula, e refletem o fato de que as plantas de maior porte disponibilizam maior quantidade de recursos para os insetos indutores de galha. Assim, um aumento na altura e no número de total de folhas implicou em um aumento de área per se e em maior visibilidade favorecendo o acesso à utilização de A. germinans pelos herbívoros ocorrentes no manguezal, e isso inclui a assembléia de artrópodos indutores de galhas.

The global effort to rehabilitate and restore destroyed mangrove forests is unable to keep up with the high mangrove deforestation rates which exceed the average pace of global deforestation by three to five times. Our knowledge of the underlying processes of mangrove forest regeneration is too limited in order to find suitable techniques for the restoration of degraded mangrove areas. The general objective of my dissertation was to improve mangrove restoration by understanding regeneration processes and local plant-plant interaction in a regenerating Avicennia germinans forest. The study was conducted in a high-shore mangrove forest area on the Ajuruteua peninsula, State of Para, Northern Brazil. The dwarf forest consisting of shrub-like trees is recovering from a stand-replacing event caused by a road construction in 1974 which interrupted the tidal inundation of the study area. Consequently, infrequent inundation and high porewater salinity limit tree growth and canopy closure. All trees and seedlings were stem-mapped in six 20 m x 20 m plots which were located along a tree density gradient. Moreover, height, crown extent, basal stem diameter of trees were measured. The area of herbaceous ground vegetation and wood debris were mapped as well. The mapped spatial distribution of trees, seedlings and covariates was studied using point pattern analysis and point process models, such as Gibbs and Thomas point process, in order to infer underlying ecological processes, such as seed dispersal, seedling establishment, tree recruitment and tree interaction. In the first study (chapter 2), I analyzed the influence of abiotic and biotic factors on the seedling establishment and tree recruitment of A. germinans during the recolonization of severely degraded mangrove sites using point process modeling. Most seedlings established adjacent to adult trees especially under their crown cover. Moreover, seedling density was higher within patches of the herbaceous salt-marsh plants Blutaparon portulacoides and Sesuvium portulacastrum than in uncovered areas. The higher density of recruited A. germinans trees in herb patches indicated that ground vegetation did not negatively influence tree development of A. germinans. In addition, tree recruitment occurred in clusters. Coarse wood debris had no apparent effect on either life stage. These results confirm that salt-marsh vegetation acts as the starting point for mangrove recolonization and indicate that the positive interaction among trees accelerates forest regeneration. In the second study (chapter 3), I analyzed how intraspecific interaction among A. germinans trees determines their growth and size under harsh environmental conditions. Interaction among a higher number of neighboring trees was positively related to the development of a focal tree. However, tree height, internode length and basal stem diameter were only positively associated in low-density forest stands (1.2 trees m-2) and not in forest stands of higher tree density (2.7 trees m-2). These results indicated a shift from facilitation, i.e. a positive effect of tree interaction, towards a balance between facilitation and competition. In the third study (chapter 4), I used point process modeling and the individual-based model mesoFON to disentangle the impact of regeneration and interaction processes on the spatial distribution of seedlings and trees. In this infrequently inundated area, propagules of A. germinans are only dispersed at a maximum distance of 3 m from their parent tree. Furthermore, there is no evidence that the following seedling establishment is influenced by trees. I was able to differentiate positive and negative tree interactions simulated by the mangrove model mesoFON regardless of dispersal processes based on static tree size information using the mark-correlation function. The results of this dissertation suggest that mangrove forest regeneration in degraded areas is a result of facilitative and not competitive interactions among mangrove trees, seedling and herbaceous vegetation. This has important implications for the restoration of degraded mangrove forest. Degraded mangrove areas are usually restored by planting a high number of evenly spaced seedlings. However, high costs constrain this approach to small areas. Assisting natural regeneration could be a less costly alternative. Herbaceous vegetation plays a crucial role in forest recolonization by entrapping propagules and possibly ameliorating harsh environmental conditions. So far only competition among mangrove trees has been considered during restoration. However, facilitative tree interactions could be utilized by planting seedling clusters in order to assist natural regeneration instead of planting seedlings evenly-spaced over large areas. This dissertation also showed that point pattern analysis and point process modeling can enable forest ecologists to describe the spatial distribution of trees as well as to infer underlying ecological processes.

Dans un cadre stratigraphique revu le remplissage miocène du bassin molassique rhodano-provençal (BMRP) a été découper en 10 séquences de dépôt (IIIrd). Trois grandes phases d'érosion fluviatile ont été caractérisées : entre l'Aquitanien et le Burdigalien inférieur et entre le Burdigalien terminal et le Langhien puis à la base du Tortonien. Les transgressions marines miocènes du BMRP sont contrôlées par l'existence de ces réseaux fluviatiles successifs. Un modèle séquentiel haute fréquence du remplissage par des carbonates bioclastiques de faciès « foramol » du premier complexe de vallées incisées est proposé. Ces réseaux miocènes qui alimentent la plate-forme et le talus du golfe du Lion permettent de mieux comprendre comment l'ouverture du Golfe du Lion, son ralentissement puis son arrêt interagissent avec le raccourcissement alpin. Les vallées aquitano-burdigaliennes sont généralement superposées et emboîtées dans les dépôts oligo-aquitaniens. Ils sont en relation direct avec l'héritage morphostructural de ce bassin d'avant-pays et signent une déformation régionale de grande longueur d'onde rapportée à une remise en compression à la base du Miocène. Les réseaux suivant en quasi-conformité avec les structures pyrénéo-provençales sont en relation avec l'activation des plis et des chevauchements et signent une déformation plicative de plus courte longueur d'onde associée pour le réseau du Burdigalien terminal à un soulèvement régional. Leur superposition souligne la pérennité d'un contrôle tectonique. Leur déboîtement est la conséquence de l'activation des plis et des chevauchements provoquant la migration des dépôts-centres et des réseaux successifs de vallées dont cette déformation amplifie le creusement.

Le besoin de connaître toujours plus finement les réservoirs (pétrole/gaz, stockage du CO2, des déchets...) se heurte au problème de la résolution temporelle (stratigraphique), notamment pour les séries sédimentaires continentales. Leur géométrie dépend essentiellement de trois facteurs: les variations du niveau marin (eustatisme), la tectonique et le climat. Cette étude vise à comprendre leur rôle respectif dans l'architecture des dépôts continentaux miocènes (~13,5-23 Ma) du bassin de Digne, dont la stratigraphie est bien établie. L'analyse séquentielle des dépôts nous a permis de distinguer une zone Nord où sept séquences de 3e ordre sont enregistrées, et une zone Sud où la tectonique locale en a fait disparaître deux. La tectonique régionale a joué sur l'amplitude et l'âge des séquences en regard des correspondances établies avec la charte eustatique. Ses effets traduisent le déplacement des dépôtcentres au cours du remplissage du bassin. L'influence du climat a joué à différentes échelles de temps. A celle de l'Optimum Climatique du Miocène (14,6-16,5 Ma), caractérisé par trois phénomènes globaux (l'excursion isotopique du 13C - Monterey Event; un maximum transgressif; le développement maximal de la mangrove à Avicennia). A celle des cycles de 3e ordre du Langhien-Serravallien, dont l'origine climato-eustatique est attestée par la comparaison du découpage séquentiel avec l'analyse pollinique. A l'échelle des cycles de Milankovitch, dont ceux d'excentricité ont été observés dans les incursions marines, les cycles de précession et d'obliquité ayant été reconnus dans la distribution et le développement des paléosols, par comparaison directe avec le signal d'insolation.

The global effort to rehabilitate and restore destroyed mangrove forests is unable to keep up with the high mangrove deforestation rates which exceed the average pace of global deforestation by three to five times. Our knowledge of the underlying processes of mangrove forest regeneration is too limited in order to find suitable techniques for the restoration of degraded mangrove areas. The general objective of my dissertation was to improve mangrove restoration by understanding regeneration processes and local plant-plant interaction in a regenerating Avicennia germinans forest. The study was conducted in a high-shore mangrove forest area on the Ajuruteua peninsula, State of Para, Northern Brazil. The dwarf forest consisting of shrub-like trees is recovering from a stand-replacing event caused by a road construction in 1974 which interrupted the tidal inundation of the study area. Consequently, infrequent inundation and high porewater salinity limit tree growth and canopy closure. All trees and seedlings were stem-mapped in six 20 m x 20 m plots which were located along a tree density gradient. Moreover, height, crown extent, basal stem diameter of trees were measured. The area of herbaceous ground vegetation and wood debris were mapped as well. The mapped spatial distribution of trees, seedlings and covariates was studied using point pattern analysis and point process models, such as Gibbs and Thomas point process, in order to infer underlying ecological processes, such as seed dispersal, seedling establishment, tree recruitment and tree interaction. In the first study (chapter 2), I analyzed the influence of abiotic and biotic factors on the seedling establishment and tree recruitment of A. germinans during the recolonization of severely degraded mangrove sites using point process modeling. Most seedlings established adjacent to adult trees especially under their crown cover. Moreover, seedling density was higher within patches of the herbaceous salt-marsh plants Blutaparon portulacoides and Sesuvium portulacastrum than in uncovered areas. The higher density of recruited A. germinans trees in herb patches indicated that ground vegetation did not negatively influence tree development of A. germinans. In addition, tree recruitment occurred in clusters. Coarse wood debris had no apparent effect on either life stage. These results confirm that salt-marsh vegetation acts as the starting point for mangrove recolonization and indicate that the positive interaction among trees accelerates forest regeneration. In the second study (chapter 3), I analyzed how intraspecific interaction among A. germinans trees determines their growth and size under harsh environmental conditions. Interaction among a higher number of neighboring trees was positively related to the development of a focal tree. However, tree height, internode length and basal stem diameter were only positively associated in low-density forest stands (1.2 trees m-2) and not in forest stands of higher tree density (2.7 trees m-2). These results indicated a shift from facilitation, i.e. a positive effect of tree interaction, towards a balance between facilitation and competition. In the third study (chapter 4), I used point process modeling and the individual-based model mesoFON to disentangle the impact of regeneration and interaction processes on the spatial distribution of seedlings and trees. In this infrequently inundated area, propagules of A. germinans are only dispersed at a maximum distance of 3 m from their parent tree. Furthermore, there is no evidence that the following seedling establishment is influenced by trees. I was able to differentiate positive and negative tree interactions simulated by the mangrove model mesoFON regardless of dispersal processes based on static tree size information using the mark-correlation function. The results of this dissertation suggest that mangrove forest regeneration in degraded areas is a result of facilitative and not competitive interactions among mangrove trees, seedling and herbaceous vegetation. This has important implications for the restoration of degraded mangrove forest. Degraded mangrove areas are usually restored by planting a high number of evenly spaced seedlings. However, high costs constrain this approach to small areas. Assisting natural regeneration could be a less costly alternative. Herbaceous vegetation plays a crucial role in forest recolonization by entrapping propagules and possibly ameliorating harsh environmental conditions. So far only competition among mangrove trees has been considered during restoration. However, facilitative tree interactions could be utilized by planting seedling clusters in order to assist natural regeneration instead of planting seedlings evenly-spaced over large areas. This dissertation also showed that point pattern analysis and point process modeling can enable forest ecologists to describe the spatial distribution of trees as well as to infer underlying ecological processes.