Abstract not available

Throughout arid and semi-arid inland Australia, many extensive floodplains occur in association with rivers which are amongst the most hydrologically variable in the world. As rainfall in these areas is characteristically low and patchy, conditions in Australia's 'dryland' floodplains fluctuate unpredictably between extended periods of drought and huge floods that transform vast areas into wetlands, often for months at a time. Vegetation in these floodplains is commonly dominated by short grass and forb associations and patches of open succulent shrubland which are attributed with high ecological and socio-economic values due to their provision of habitat to a diverse array of terrestrial and aquatic fauna and their productive native pasture growth. In temperate and tropical floodplains, a substantial number of studies have shown that plant community composition and structure is determined primarily by flow and alterations to flow in these areas, through water extraction or river regulation, have resulted in many changes to the vegetation including loss of biodiversity and mass invasions of exotic species. Despite increasing pressure for water resource development in 'dryland' regions, relatively little is known regarding the effects of highly variable flows on the vegetation dynamics of arid floodplains, particularly in Australia. This thesis addresses this knowledge gap by examining the role of flow in the vegetation dynamics of a large arid floodplain in central Australia: the Cooper Creek floodplain. The effects of flow on plant community dynamics, from an organism level to that of the landscape, are examined across a range of spatial and temporal scales. Results are presented from a two year temporal vegetation survey during which time two flood pulse events of differing sizes occurred. A large-scale spatial survey was also conducted to determine the effects of flood history on spatial variation in plant community composition and structure. The composition of the soil seed bank and its contribution to vegetation dynamics were additionally investigated through a series of germination trials. Amongst common arid floodplain plants, life history traits that enable persistence under variable hydrological conditions were also considered via several experiments aimed at determining the effects of flow on the outcomes of various life history stages including germination, growth and dispersal. Throughout the study, results are presented for plant groups that were predefined on the basis of life form, life span and taxonomic divisions within these categories. Plant community composition and structure in the Cooper Creek floodplain exhibits significant shifts both temporally, in response to flood pulse wetting and drying, and spatially, in response to flood history. Flood pulse inundation has the potential to influence each life history stage across the range of plant groups present and the outcomes of these appear to be determined by hydrological attributes such as flood pulse timing, duration and rate of drawdown. Vegetation consequently exhibits gradual zonation on a gradient of flood frequency along which plant groups occur at predictable locations depending on their life history traits and recent hydrological conditions. A substantial proportion of species display ruderal life history traits including large, persistent soil seed banks and rapid life cycles which enable escape in time from the stresses associated with flooding and drought. These species, mostly comprising annual monocots and forbs, are widespread throughout the landscape and their presence in the extant vegetation is related primarily to the time since the last flood pulse event and the hydrological attributes of this. Perennial species, particularly shrubs, do not appear to rely similarly on the soil seed bank for recruitment and their distribution in the floodplain vegetation is likely to be determined more by their ability to tolerate either flooding or drought. Overall, this study demonstrates that flow, despite its variability, has an overriding influence on vegetation dynamics in the arid floodplain of the Cooper Creek. The spatial and temporal variability of flow maintains a heterogeneous mosaic of plant communities of differing composition and structure. Given this close relationship between flow and vegetation dynamics, anthropogenic alterations to flow are likely to result in changes to the vegetation including homogenisation of plant communities across the floodplain landscape and eventual loss of biodiversity.

No description available.

Os ecossistemas de ilhas, continentais ou oceânicas, são considerados os mais sensíveis à perturbação humana. A maioria das ilhas costeiras do Brasil sofreu fortes alterações na fauna e flora silvestre. A Ilha Anchieta (Ubatuba, SP) é uma Área Protegida com um longo histórico de perturbação, tendo sido amplamente desmatada no passado e sofrido a introdução de animais. Sabe-se que a fauna possui um papel chave na composição e estrutura da comunidade vegetal, favorecendo algumas espécies e prejudicando outras. Sendo assim, a perda ou alteração dos processos de interações entre animais e plantas afetam na estrutura e composição de espécies. Este estudo analisa as interações antagônicas entre planta e animais como possíveis fatores limitantes no processo de regeneração natural em três ambientes com distintos estágios sucessionais presentes na Ilha Anchieta: campo aberto (CA) e florestas ombrófilas rala (FOR) e densa (FOD). Para isso foram testados nos três ambientes os processos pós-dispersão de sementes: a predação de sementes pós-dispersas, a germinação do banco de sementes e a herbivoria. A predação de sementes apresentou forte efeito espacial (FOD>FOR>CA) e sazonal, com maiores proporções de predação de sementes no período de escassez de alimento (estação seca). Quantitativamente o banco de sementes não representa um fator limitante, porém foi composto por uma baixa diversidade de espécies lenhosas. A capacidade de germinação do banco de sementes do solo foi similar entre os ambientes florestais apresentando menor emersão de plântulas no campo aberto, provavelmente associado ao intenso escoamento superficial no local. Adicionalmente, a mortalidade de juvenis transplantados foi de 72,27%, sendo superior nas parcelas abertas aos vertebrados para todas as espécies em todos os ambientes, demonstrando um forte efeito negativo dos herbívoros vertebrados na comunidade vegetal. Sendo assim, foram detectados distintos gargalos atuando simultaneamente na regeneração natural nos três ambientes da Ilha Anchieta, sendo necessário o estabelecimento de práticas de manejo visando minimizar os efeitos abióticos no campo aberto e floresta ombrófila rala, favorecendo as interações mutualísticas e inibindo a atividade de animais antagônicos nas florestas ombrófilas rala e densa, acelerando assim o processo de regeneração natural na Ilha Anchieta. Considerar simultaneamente os obstáculos no processo de regeneração nos auxiliará a traçar práticas de restauração e recuperação de áreas degradadas mais efetivas e viáveis economicamente. / Island ecosystems, either continental or oceanic, are considered the most sensible to anthropogenic influences. Most Brazilian coastal islands have their original fauna and flora composition altered. The Anchieta Island (southeast Brazil) is a Protected Area that suffered deforestation and introduction of alien species. It is known that the fauna plays a key role in composing and structuring the vegetal community, favoring some species and harming others. Thus, the loss or change of animal-plant interactions affects the framework and composition of species. We simultaneously analyzed the antagonistic animal-plant interactions as possible limiting factors in the natural regeneration on tree successional stages of the Anchieta Island: the old fields (OF), the early secondary forest (ESF) and old growth forest (OGF). Therefore, in each habitat we are evaluating post-dispersal seed predation processes: post-dispersal seed predation, soil seed bank, and the herbivory. We found spatial (OGF>ESF>OF) and temporal effects on seed predation, with highest rates on dry season. Quantitatively, soil seed bank did not represent a limiting factor; but qualitatively, it was composed by few woody species. Our data pointed to the absence of a viable soil seed bank in the OF, probably due to an intense runoff. The forested habitats presented similar soil bank. Moreover, the total mortality of saplings was 72.27%, being higher on the unfenced treatment for all species and in all habitats, showing a very strong negative effect of vertebrate herbivores on the vegetal community. Therefore, we are detecting distinct bottlenecks acting simultaneously in the natural regeneration process in all of the successional stages of the Anchieta Island. Our results showed that management actions are required, aiming to both minimize the abiotic effects on the old fields and in the early secondary forest and to favor the mutual interactions and inhibit the activity of antagonic animals in the old growth and early secondary forests, accelerating, this way, the natural regeneration process of the Anchieta Island. Considering simultaneously the obstacles in the regeneration process will help to define restoration and recuperation procedures of degraded areas more effective and affordable.

The most recent surveys in South Africa estimate that invasions are still increasing, despite substantial clearing efforts. Riparian systems in South Africa are particularly vulnerable to invasion by woody IAPs. This thesis addresses the restoration of alien‐invaded riparian systems, by investigating the factors that facilitate or constrain spontaneous recovery and influence the trajectories of succession. These factors include invasion history and management history, especially the use of fire. A seedling emergence approach was used to test the presence of a viable pre‐fire seedbank, and the effect of fire on the seed bank. The efficacy of some active restoration interventions was also tested, with the aim to return invasion‐resistant, indigenous vegetation with a structure and function representative of uninvaded sites. The findings of this study indicated the presence of a viable and persistent riparian soil seed bank, even after 30 years of intermtittent invasion as well as two fire cycles under invasion. It shows that the management practice of fell‐and‐burn resulted in high soil temperatures, and that this reduced the indigenous soil seed bank density, especially in the upper soil layer. Clear germination sequences and patterns of emergence over time for different species were observed during this study, with many species exhibiting delayed emergence relative to the timing of the fire event. It is proposed that manipulation of the season of fire could be used to selectively optimise the order of arrival and therefore superior recruitment of some species over others in the Eastern Cape fynbos, and thus alter the trajectories of recovery of vegetation towards a more desired state. Active restoration in the form of indigenous seed and plant additions resulted in a significantly higher indigenous cover after seven months, compared to a control (passive restoration) or restoring with grass. Indigenous cover and composition was also strongly influenced by lateral zonation, and some key guilds and species were missing or present in much lower densities compared to reference sites. Grass restoration significantly suppressed the regeneration of A. longifolia, as well as the regeneration of indigenous species. Biotic resistance can thus be achieved through restoration, and it could be a powerful tool in the management of IAPs, although the deliberate introduction of grass after clearing in fynbos also reduces biodiversity and could have unforeseen consequences to riparian function.

Orientadores: Carlos Alfredo Joly, Flavio Antonio Maës dos Santos / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-27T11:17:29Z (GMT). No. of bitstreams: 1 Vinha_Daniella_D.pdf: 19806435 bytes, checksum: af3818b4640c3acda5f09a0580ff9346 (MD5) Previous issue date: 2015 / Resumo: Estudos prévios demonstraram baixa sazonalidade na frutificação em florestas tropicais não-sazonais, o que poderia influenciar o padrão temporal e espacial da chuva de sementes e do banco de sementes. Entretanto, esses processos não são conhecidos. O objetivo desse estudo foi determinar como ocorre a regeneração natural via sementes em uma floresta tropical Montana no Parque Estadual da Serra do Mar. Foram testadas as hipóteses: (1) a sazonalidade na chuva de sementes é fraca ou ausente e esse padrão não se diferencia dentro dos modos de dispersão; (2) o banco de sementes é florísticamente relacionado com a chuva de sementes e espacialmente acoplado; (3) o banco de sementes apresenta baixa sazonalidade e esse padrão não difere dentro dos modos de dispersão. Em 2 hectares de floresta, nós registramos o total de 29959-62904 diásporos na chuva de sementes (104-106 spp.), 1029-2999 diásporos no banco de sementes da serapilheira (36-38 spp.) e 6288-7824 plântulas no banco de sementes do solo (74-82 spp.) ao longo de dois anos. Asteraceae, Urticaceae e Melastomataceae foram abundantes na chuva de sementes (63-81%), no banco de sementes da serapilheira (70-73%) e no banco de sementes do solo (77-84%). A maior riqueza de espécies foi de arbóreas na chuva de sementes (59-61%) e banco de sementes da serapilheira (72-68%), e de herbáceas no banco de sementes do solo (ca. 55%). Houve maior proporção de sementes arbóreas em todas as vias de regeneração, assim como maior riqueza de espécies zoocóricas (mais de 50%). Entretanto, a anemocoria contribuiu com a maior proporção do total de sementes no banco de sementes do solo (ca. 75%) e da chuva de sementes de uma das áreas (64%). Houve sazonalidade na chuva de sementes com um único pico na abundância (Out-Nov). Esse padrão foi reforçado pela sazonalidade na abundância e riqueza de espécies da chuva de sementes anemocórica e zoocórica, ambas ocorrendo no período de maior precipitação. A chuva de sementes influenciou a composição de espécies das sementes contidas na serapilheira e no solo. Entretanto, o acoplamento espacial entre as vias de regeneração ocorreu somente em uma das áreas. O banco de sementes não apresentou variações na composição florística e houve fraca variação temporal na densidade e riqueza de espécies, repercutindo igualmente dentro dos modos de dispersão. Esse estudo demonstrou que a chuva de sementes pode ser sazonal em condições de baixa sazonalidade ambiental, independente do modo de dispersão das sementes. A relação entre composição da chuva de sementes e das sementes contidas na serapilheira e no solo revela que essas vias são interligadas e dependentes entre si, resultando em padrões espaciais agrupados. Como resultado, a baixa variação temporal do banco de sementes não pode ser atribuída à baixa sazonalidade na chuva de sementes. O fato de não haver acúmulo de sementes no solo após o período de dispersão sugere o baixo tempo de permanência das sementes. Por outro lado, a falta de acoplamento espacial em uma das áreas sugere processos de pós-dispersão atuando na reestruturação espacial do banco de sementes / Abstract: Previous studies have demonstrated low seasonality in the fruiting phenology in aseasonal tropical forests, which could influence the spatial and temporal pattern of seed rain and seed bank. However, these processes are poorly known. The aim of this study was to determine seed natural regeneration in an Atlantic tropical Montane forest located in southeast of Brazil, Serra do Mar State Park. The hipotheses were tested: (1) seasonality of seed rain is weak or absent and this pattern is no different within the dispersal modes; (2) the floristic composition of seed bank is closely related with seed rain and there is a spatial association between them; (3) the seed bank has a low seasonality and this pattern is the same within the dispersal modes. In two hectares of forest we recorded total of 29959-62904 seeds in the seed rain (104-106 spp.), 1029-2999 seeds in the litter seed bank (36-38 spp.) and 6288-7824 seedlings in the soil seed bank (78-82 spp.) over two years. Asteraceae, Urticaceae and Melastomataceae were abundant in the seed rain (63-81%), litter seed bank (70-73%) and soil seed bank (77-84%). Trees accounted to higher species richness in the seed rain (59-61%) and litter seed bank (72-68%). Herbaceous were most important to the species richness of soil seed bank (ca. 55%). There were more of tree seeds in all regeneration modes, as well as greater zoochorous species richness (more than 50%). However, anemochory had the largest proportion of total seeds in the soil seed bank (ca. 75%) as well as one of the areas where the seed rain was sampled (64%). There was seasonality of seed rain with a single peak in abundance (Oct-Nov). This pattern was reinforced by seasonality in the anemochorous and zoochorous abundance and species richness of seed rain, both occurring in the period of greatest rainfall. Seed rain influenced the species composition of the seeds in the litter and soil. However, the spatial coupling between the regeneration modes occurred in only one area. The soil seed bank showed no changes in the floristic composition and there was a weak temporal variation in density and species richness reflecting also within in the dispersal syndromes. This study demonstrated that seasonality in seed rain can occur even in tropical forests where environmental seasonality is low, regardless of the manner in which the seeds are dispersed. The relationship between seed rain and seed bank composition (litter and soil) reveals that these pathways are interconnected and dependent on each other, resulting in clustered spatial patterns. As a result, the low temporal variation of soil seed bank can not be attributed to the low seasonality of seed rain. Since there is no seed accumulation in the soil after a period of seed dispersal, short residence time of the seed in the soil is suggested. On the other hand, the lack of spatial association between seed rain and seed bank in one of the areas suggests post-dispersal processes acting in the spatial restructuring of the seed bank / Doutorado / Biologia Vegetal / Doutor em Biologia Vegetal

Ziel des Forschungsprojektes war der Gewinn umfassender verjüngungsökologischer Kenntnisse zu den Pionierbaumarten Sandbirke (Betula pendula Roth), Salweide (Salix caprea L.) und Eberesche (Sorbus aucuparia L.) im Hinblick auf eine natürliche, eingriffsfreie Wiederbewaldung von Schadflächen (z.B. nach Sturmwurf). Die Abschätzung des Besiedlungserfolges von Schadflächen durch Pionierbaumarten ist aufgrund unzureichender verjüngungsökologischer Kenntnisse gegenwärtig noch mit großen Unsicherheiten verbunden. Die Untersuchungen fanden auf fünf 4-12 ha großen Kyrill-Sturmwurfflächen in den Hoch- und Kammlagen (750-900 m ü. NN) des Thüringer Waldes statt. Alle potenziellen Samenbäume der Pionierbaumarten wurden in den angrenzenden, geschlossenen Fichtenbeständen lokalisiert. Als Versuchsdesign wurde in Abhängigkeit der vorgefundenen Samenbaumdichten und -verteilungen ein Kreuz- bzw. Sterntransekt auf den Sturmwurfflächen etabliert. Entlang der Transektlinien wurden alle 20 m Samenfallen installiert. Als Samenfallen kamen für die Sandbirke Netztrichterfallen (0,2 m²), für die Salweide Klebfallen (0,043 m²) und für die endozoochore Ausbreitung durch frugivore Vogelar-ten Kotfallen (0,25 m²) zum Einsatz. Für die Modellierung der Samenausbreitung von Sandbirke und Salweide wurden inverse Modelle bzw. geostatistische Modelle erstellt. Zudem wurden auf einer der Sturmwurfflächen genetische Nachkommenschaftsanalysen bei Sal-weide mittels Kern-DNA-Primer durchgeführt. Die Bodensamenbankuntersuchungen fanden in jeweils drei geschlossenen Birkenbeständen, Fichten-Birken-Beständen, Fichtenbeständen mit einer einzeln eingemischten Birke und reinen Fichtenbeständen im Tharandter Wald und Thüringer Wald statt. Mittels eines 10,2 cm breiten Stechzylinders wurden 10 cm tiefe Bodenproben gewonnen. Die Lagerung der Proben fand im Kaltgewächshaus statt, wo alle 14 d die gekeimten Samen erfasst wurden. Weiterhin wurde ein Eingrabungsexperiment installiert. Dafür wurden Sandbirkensamen, Ebereschensamen und Ebereschenfrüchte in 2 cm, 5 cm und 10 cm tiefen Mineralboden vergraben und in sechsmonatigen Intervallen jeweils eine Keimprobe zum Test der verbliebenen Keimfähigkeit entnommen. Die Auswertung der Bodensamenbankuntersuchungen erfolgte mittels GLM und GLMM. Während der zweijährigen Untersuchung zur zeitlichen und räumlichen Samenausbreitung von Salix caprea auf fünf Sturmwurfflächen konnten ein schwächeres und ein stärkeres Samenjahr nachgewiesen werden. Des Weiteren erstreckte sich der Samenflugzeitraum im Frühjahr in Abhängigkeit von den klimatischen Bedingungen über 12 Wochen in 2015 und 6 Wochen in 2016. Die höchsten Samenmengen von 23-156 Samen je Falle wurden jeweils unter den Kronen von Salweiden-Samenbäumen nachgewiesen. Ab einer Entfernung von 350 m zum Samenbaum bis zur untersuchten Distanz von 870 m wurden, unabhängig von der Distanz, der Hangneigung, der Anzahl der Samen-bäume und der Windrichtung (Anisotropie), im Durchschnitt 0,6-2,1 Samen je Falle er-fasst. Die genetischen Analysen zur Nachkommenschaft ergaben, dass 29 % der untersuch-ten Verjüngungspflanzen von einem der 20 lokalisierten Elternbäume in der bewaldeten, 500 m breiten Suchzone abstammten. Die Ausbreitungsdistanzen der nachweislich am erfolgreichsten verjüngten Samenbäume betrugen dabei 550-800 m. Insgesamt zeigte die Salweidenverjüngung eine höhere Allel-Variation, als die 20 Elternbäume, was auf einen externen Genfluss und lange Samen- und Pollenausbreitungsdistanzen hinweist. Im Zuge des zweijährigen Untersuchungszeitraums zur Samenausbreitung von Betula pendula auf zwei Kyrill-Sturmwurfflächen konnten ein Mastjahr und ein Zwischenjahr nachgewiesen werden. Die Ergebnisse der inversen Modellierung mittels isotroper Mo-delle ergaben dabei flächenunabhängig Produktionsmengen für einen Samenbaum von 20 cm im Bhd von 300.000-366.000 Samen je Baum im Zwi-schenjahr 2015 und 1.430.000-1.530.000 Samen je Baum im Mastjahr 2016. Mittels räumlicher Modellierung der Samenausbreitung konnte keine Anisotropie belegt werden. Unabhängig von den beprobten Flächen und Un-tersuchungsjahren, belegen die Modellschätzungen allesamt eine isotrope Ausbreitung der Samen. Die mittleren Ausbreitungsdistanzen (MDD) beliefen sich dabei hangaufwärts auf 86-97 m und hangabwärts auf 367-380 m. Maximal ab-gelagerte Samendichten von 2.015 n m-² im Zwischenjahr und 9.557 n m-² im Mastjahr fanden sich bis 40-50 m Entfernung zum Samenbaum. Die Untersuchungen der endozoochoren Samenausbreitung auf fünf Sturmwurfflächen weisen auf eine bevorzuge Nutzung der Vogelarten von Rast- und Sitzgelegenheiten (Strukturelemente) auf Freiflächen zum Absetzen von Kot hin (2,7 Kothaufen je m²). Unter Freiflächenbedingungen - ohne Strukturelemente - ergaben sich im Mittel 0,4 Kothaufen je m². Die höchsten mittleren Kotdichten wurden unter aufra-genden Totästen (20 n m-²), umgeklappten Wurzeltellern (4,6 n m-²) und Hochstubben (3,9 n m-²) nachgewiesen. Schwach dimensionierte Verjüngungspflanzen der Sandbirke, Eberesche und Fichte, und Strukturelemente unter einem Meter Höhe wurden dagegen weitgehend für das Absetzen von Kot gemieden. Das Vermögen zum Aufbau einer Bodensamenbank durch Betula pendula und Sorbus aucuparia unterschied sich deutlich. 56-100 % der eingegrabenen Sandbirkensamen wa-ren auch nach 2,5 Jahren keimfähig, wohingegen lediglich 3-16 % der eingegrabenen Ebereschensamen ohne Fruchthülle und 0-19 % der eingegrabenen Ebereschensamen mit Fruchthülle vital waren. Die Auswertung mittels GLM prognostizierte einen kom-pletten Verlust der Keimfähigkeit nach 12 Jahren, 4,5 Jahren und 3 Jahren der Sandbirkensamen, sowie der Ebereschensamen mit und ohne Fruchthülle. Ein Einfluss der Lagerungstiefe war nur für Sandbirke nachweisbar. Die Untersuchungen der Bodensamenbank von Birke in Fichtenbeständen mit unter-schiedlichen Birkensamenbaumanteilen ergab einen straffen Zusammenhang zwischen der Anzahl von Samenquellen und den nachgewiesenen Samendichten im Boden. In den Birkenbeständen fanden sich stets die höchsten Dichten von 489-1.142 Birkensamen je m². Die Analyse unterschiedlicher Bodenschichten zeigte zudem signifikant abneh-mende Birkensamendichten mit zunehmender Bodentiefe. Die Ergebnisse der Untersuchungen zeigen, dass die Fruktifikation von Betula pendula, Salix caprea und Sorbus aucuparia durch klimatische Verhältnisse beeinflusst wird, weshalb die drei Pionierbaumarten nicht alljährlich hohe Samenmengen produzieren (Mastjahre und Zwischenjahre). Zum Ausgleich von Produktionsdefiziten in den Zwischenjahren unter-scheiden sich die Pionierbaumarten in ihrer Strategie. Dies gilt es bei der Umsetzung des Konzeptes einer natürlichen, eingriffsfreien Wiederbewaldung von Schadflächen nach Sturmwurf durch die Naturverjüngung von Pionierbaumarten zu beachten. Die einzige der drei Pionierbaumarten, die dem allgemeinen Bild einer Pionierbaumart ent-spricht, ist die Salweide. Ihr Besiedlungserfolg ist allein von den aktuellen, alljährlich variierenden, aber dennoch stets hohen Samenproduktionsmengen und den enorm weiten Aus-breitungsdistanzen (>800 m) abhängig. Hinsichtlich der Samenausbreitung haben die Him-melsrichtung, die Position der Samenbäume und die Anzahl vorhandener Samenquellen ab einer Distanz von 50 m zur Schadfläche keinen bedeutenden Einfluss auf die abgelagerten Samenmengen mehr. Die auf 86-380 m limitierte Samenausbreitung von Sandbirke wurde dagegen stark vom Geländerelief (Hangneigung), der Position der Samenbäume (Tal, Kuppe, Hanglage) und der Distanz der Samenbäume zur Sturmwurffläche beeinflusst. Zum Ausgleich der limitierten Samenausbreitung und deutlich reduzierten Samenmengen im Zwischenjahr ist Sandbirke jedoch zum Aufbau einer short-term persistenten Bodensamenbank befähigt. Den gesamten Verjüngungszyklus betrachtend entspricht die Eberesche eher einer Schluss-waldbaumart. Unter ungünstigen klimatischen Bedingungen kommt es häufig zum kompletten Ausfall der Samenproduktion. Ihr enormes Wiederbewaldungspotential von Sturmwurfflächen speist sich hauptsächlich aus dem Aufbau einer Sämlingsbank und weni-ger durch den aktuellen Samenregen oder der short-term persistenten Bodensamenbank. Die limitierte Samenausbreitung von Sandbirke und Eberesche macht eine „räumliche Optimierung“ der Samenbaumpositionen durch die Forstwirtschaft erforderlich. Aufgrund der allgegenwärtigen Omnipräsenz von Weidensamen ist dies für Salweide nicht zwingend not-wendig. Das detailreiche Wissen zur Verjüngungsökologie der untersuchten Pionierbaumar-ten ermöglicht eine gezielte waldbauliche Steuerung im Sinne des Vorhalts und der Pflege von Pionierbaumarten im Wirtschaftswald. Dies ist gegenwärtig und zukünftig vor allem von besonderer Bedeutung, da aufgrund der zu erwartenden Zunahme von Schadereignissen und deren Unvorhersehbarkeit die Fähigkeit der Wälder zur natürlichen Wiederbewaldung von Schadflächen durch Pionierbaumarten zunehmend an Interesse gewinnen wird.:Table of abbreviations III Summary IV Zusammenfassung VIII Chapter 1 – General introduction 1 1.1 Introduction 2 1.1.1 Importance and relevance of the study 2 1.1.2 Research interest - regeneration ecology 5 1.3 Aims, scope and hypotheses 9 1.4 Study outline 12 1.5 References 13 Chapter 2 – Seed dispersal capacity of Salix caprea L. assessed by seed trapping and parentage analysis 25 2.1 Abstract 26 2.2 Introduction 26 2.3 Materials and methods 29 2.3.1 Study area 29 2.3.2 Experimental design 31 2.3.3 Genetic analysis 32 2.3.4 Seed trap data analysis 33 2.3.5 Geostatistical models 34 2.4 Results 36 2.4.1 Temporal patterns of seed dispersal 37 2.4.2 Dispersal distance and spatial patterns of seed dispersal 37 2.4.3 Genetic parentage analysis 40 2.5 Discussion 42 2.5.1 Seed production and temporal patterns of seed dispersal 42 2.5.2 Dispersal distance and spatial patterns of seed dispersal 43 2.5.3 Genetic parentage analysis 45 2.6 Conclusions for silvicultural practice 46 2.7 References 48 Chapter 3 – Restrictions on natural regeneration of storm-felled spruce sites by silver birch (Betula pendula Roth) through limita-tions in fructification and seed dispersal 57 3.1 Abstract 58 3.2 Introduction 58 3.3 Materials and methods 60 3.3.1 Study area 60 3.3.2 Experimental design 63 3.3.3 Data analysis 64 3.3.4 Seed dispersal model 64 3.3.5 Simulations for practical management decisions 66 3.4 Results 66 3.4.1 Seed production 66 3.4.2 Seed dispersal and spatial patterns 68 3.5 Discussion 71 3.5.1 Seed production 71 3.5.2 Directionality 72 3.5.3 Spatial patterns and seed dispersal distances 72 3.6 Seed dispersal scenarios for silvicultural management decisions 74 3.6.1 Seed dispersal scenarios 74 3.6.2 Conclusions for silvicultural management decisions 76 3.7 References 78 Chapter 4 – The impact of structural elements on storm-felled sites on endozoochorous seed dispersal by birds – a case study 85 4.1 Abstract 86 4.2 Introduction 86 4.3 Materials and methods 88 4.3.1 Study area 88 4.3.2 Experimental design 90 4.3.3 Data analysis 91 4.4 Results 92 4.5 Discussion 95 4.6 Conclusions for silvicultural practice 97 4.7 References 98 Chapter 5 – Soil seed banks of pioneer tree species in European tempe-rate forests: a review 104 5.1 Abstract 105 5.2 Introduction 105 5.3 Methods of literature search 107 5.4 Species-specific reproductive ecology determining the potential of soil seed banks 110 5.5 Characterization and classification of soil seed banks 112 5.5.1 Soil seed bank of Betula spp. 114 5.5.2 Soil seed bank of Alnus glutinosa (L.) GAERTN. 116 5.5.3 Soil seed banks of Salix spp. and Populus tremula L. 117 5.5.4 Soil seed bank of Sorbus aucuparia L. 118 5.6 Conclusions 119 5.7 References 120 Chapter 6 – Do birch and rowan establish soil seed banks sufficient to compensate for a lack of seed rain after forest disturbance? 134 6.1 Abstract 135 6.2 Introduction 135 6.3 Materials and methods 137 6.3.1 Study areas 137 6.3.2 Data collection 139 6.3.3. Statistical analysis 140 6.4 Results 141 6.4.1 Study A - Artificial seed burial experiment 141 6.4.2 Study B - Soil core sampling in the forest 145 6.5 Discussion 147 6.5.1 Study A - Artificial seed burial experiment 147 6.5.2 Study B - Soil core sampling in the forest 149 6.6 Conclusions 151 6.7 References 152 Chapter 7 – General discussion 160 7.1 Discussion of important aspects of regeneration ability 161 7.1.1 Fructification and seed production in Salix caprea, Betula pendula and Sorbus aucuparia 165 7.1.2 Ecological processes within the regeneration cycle of Salix caprea 167 7.1.3 Ecological processes within the regeneration cycle of Betula pendula 168 7.1.4 Ecological processes within the regeneration cycle of Sorbus aucuparia 169 7.2. Conclusions for silviculture and management recommendations 172 7.3 References 175 Table of appendix i / The aim of the study was to obtain comprehensive knowledge of the regeneration ecology of the pioneer tree species silver birch (Betula pendula Roth), goat willow (Salix caprea L.) and rowan (Sorbus aucuparia L.). The findings should contribute to better management of the natural regeneration of disturbed sites (e.g., windthrown sites) by pioneer tree species. Insufficient knowledge of the regeneration ecology of pioneer tree species renders forest managers’ abilities to assess the success of regeneration of windthrown sites uncertain. The study took place in the years 2015 and 2016. The study sites were located on the slopes and mountain tops (plateaus) of the Thuringian Forest (715-900 m a.s.l.), on five windthrown open areas (4-13 ha) created by the storm ‘Kyrill’ in January 2007. All seed trees of pioneer tree species were mapped within the forested search zone around each site. This zone extended 200 m for silver birch and rowan and 500 m for goat willow. Following the mapping of these seed trees and an analysis of their spatial distribution, seed traps were placed along two or four crossing line transects, with intervals of 20 m between traps. The traps were funnel shaped net seed traps for silver birch (0.2 m²), seed traps with a sticky, non-drying glue for goat willow (0.043 m²) and dropping traps for seeds dispersed endozoochorously by frugivorous birds (0.25 m²). A phenomenological model and model-based geostatistics were used to investigate silver birch and goat willow seed dispersal. For goat willow a parentage analysis was performed at one of the study sites using nuclear-DNA-primers. The soil seed bank study was carried out in three birch stands, spruce stands with admixed birch, spruce stands with one isolated birch tree and pure spruce stands in the Tharandter Forest and in the Thuringian Forest. Soil core samples with a diameter of 10.2 cm were taken from the litter layer and the mineral soil to a depth of 10 cm. The soil samples were placed in a greenhouse and seed germination was checked every 14 days. An artificial seed burial experiment was also carried out. Silver birch seeds, rowan seeds and rowan fruits were buried in mineral soil at depths of 2 cm, 5 cm and 10 cm. At intervals of 6 months sample sets were removed from the soil and the germination capacity checked. The analysis of the soil seed banks was based on generalized linear mixed models (GLMM) and generalized linear models (GLM). The 2-year study of the temporal and spatial dispersal of seeds of Salix caprea on five Kyrill-felled areas involved one year with lower seed production and one with more bountiful seed production. The duration of the spring seed rain was about 12 weeks in 2015, and only 6 weeks in 2016 because of contrasting weather conditions. The highest seed numbers of 23-156 n per trap occurred close to the base of the seed trees. Beyond 350 m from the seed trees, up to the maximum distance in the study of 870 m, the average numbers of seeds per trap (0.6-2.1 seeds) were independent of the dispersal distance, inclination, the number of seed sources and the dispersal direction (anisotropy). Parentage analyses showed that 29% of the saplings stemmed from one of the 20 parent trees within the 500 m search zone extending from the edge of the open area. The seed dispersal distances of the most successful seed parents were between 550-800 m. The saplings revealed a higher allelic variation than the 20 parent trees, indicating external gene flow and long seed and pollen dispersal distances. During the 2-year study of Betula pendula seed dispersal on two Kyrill-felled areas there was a mast year and a non-mast year. Independent of the site, the seed production rate of a silver birch seed tree with a mean diameter at breast height (dbh) of 20 cm predicted by isotropic inverse models was approximately 300,000-366,000 seeds in 2015 and 1,430,000-1,530,000 seeds per tree in the mast year 2016. Directionality (anisotropic inverse modelling) of seed dispersal around an individual seed tree could not be confirmed. The model results revealed the isotropic model (no directionality) to be an appropriate approach for all sites and years. The mean dispersal distances (MDD) were 86 m and 97 m (uphill) and 367 m and 380 m (downhill). The maximum seed numbers occurred within 40-50 m of a seed tree, amounting to 2,015 n m-² in the non-mast year and 9,557 n m-² in the mast year. The study of endozoochorous seed dispersal on the five sites felled by the storm Kyrill showed a preference of frugivorous birds for perches and resting places (structural elements) from which to defecate onto open areas (2.7 droppings per m²). On completely open areas – with no structural elements – an average of 0.4 droppings per m² was recorded. The highest mean bird dropping density was observed under towering dead branches (20 n m-²), upturned root plates (4.6 n m-²) and high stumps (3.9 n m-²). Young, small diameter silver birch, rowan and spruce trees, and structural elements less than 1 m in height generally, were avoided by frugivorous birds as a place from which to defecate. The abilities of Betula pendula and Sorbus aucuparia to form a soil seed bank differed. Between 56-100 % of the buried silver birch seeds were still viable after 2.5 years, whereas only 3-16 % of the rowan seeds buried without pulp and 0-19 % of the rowan seeds within pulp were viable. The maximum durations of storage in the soil predicted for silver birch seeds and rowan seeds with and without pulp by GLM were 12 years, 4.5 years and 3 years. An influence of the storage depth was found for silver birch seeds only. The investigation of the soil seed banks of birch in three birch stands and nine spruce forests with different numbers of admixed birch seed trees showed a strong correlation between the number of seed sources and the seed density in the soil. The birch stands contained the highest mean densities of viable birch seeds in soil, between 489-1,142 n m-². The analysis of the different soil layers showed significantly declining birch seed densities with increasing soil depth across all sites. The results of the study showed that the fructification of Betula pendula, Salix caprea and Sorbus aucuparia is influenced by weather conditions, with the three pioneer tree species failing to produce high numbers of seeds every year (mast and non-mast years). The three species differed in their strategies to compensate for low seed production in non-mast years. This must be considered when implementing a concept for the reforestation of disturbed sites based on natural regeneration by pioneer tree species. Goat willow was the only one of the three specie studied with characteristics corresponding to the general assumptions made about pioneer tree species. The regeneration success of goat willow is dependent upon the variable but generally high annual seed production and long seed dispersal distances (> 800 m). The azimuth direction, position and number of seed trees have no meaningful influence on seed numbers at a distance of more than 50 m from the seed source. The limited mean seed dispersal distances of 86-380 m determined for silver birch were influenced by site inclination, the seed tree location (valley, slope or plateau) and the distance between the seed tree and the windthrown site. Silver birch seed shadow is also influenced by the number of seed sources. To compensate for the limited dispersal distances and the significantly lower seed production in non-mast years, silver birch is able to build up a short-term persistent soil seed bank. The regeneration cycle of rowan is more reminiscent of that of a shade-tolerant tree species. Unfavorable weather conditions often result in a complete failure to produce seeds. The enormous regeneration potential of rowan on disturbed sites stems primarily from a seedling bank, which is built up over years. The seed rain in any given year and its short-term persistent soil seed bank are of secondary importance. Forest management targeting a ‘spatial optimization’ of silver birch and rowan seed trees is necessary to ensure successful natural regeneration given the limited seed dispersal. The omnipresence of goat willow seeds renders specific spatial management measures for its establishment unnecessary. Detailed knowledge of the regeneration ecology of the studied pioneer tree species makes possible an approach to silviculture that is targeted to the conservation and revitalization of pioneer tree species in managed forests. The expected increase in the frequency of disturbances, and their unpredictability, means that the ability of forests to naturally regenerate using pioneer tree species is likely to grow in importance.:Table of abbreviations III Summary IV Zusammenfassung VIII Chapter 1 – General introduction 1 1.1 Introduction 2 1.1.1 Importance and relevance of the study 2 1.1.2 Research interest - regeneration ecology 5 1.3 Aims, scope and hypotheses 9 1.4 Study outline 12 1.5 References 13 Chapter 2 – Seed dispersal capacity of Salix caprea L. assessed by seed trapping and parentage analysis 25 2.1 Abstract 26 2.2 Introduction 26 2.3 Materials and methods 29 2.3.1 Study area 29 2.3.2 Experimental design 31 2.3.3 Genetic analysis 32 2.3.4 Seed trap data analysis 33 2.3.5 Geostatistical models 34 2.4 Results 36 2.4.1 Temporal patterns of seed dispersal 37 2.4.2 Dispersal distance and spatial patterns of seed dispersal 37 2.4.3 Genetic parentage analysis 40 2.5 Discussion 42 2.5.1 Seed production and temporal patterns of seed dispersal 42 2.5.2 Dispersal distance and spatial patterns of seed dispersal 43 2.5.3 Genetic parentage analysis 45 2.6 Conclusions for silvicultural practice 46 2.7 References 48 Chapter 3 – Restrictions on natural regeneration of storm-felled spruce sites by silver birch (Betula pendula Roth) through limita-tions in fructification and seed dispersal 57 3.1 Abstract 58 3.2 Introduction 58 3.3 Materials and methods 60 3.3.1 Study area 60 3.3.2 Experimental design 63 3.3.3 Data analysis 64 3.3.4 Seed dispersal model 64 3.3.5 Simulations for practical management decisions 66 3.4 Results 66 3.4.1 Seed production 66 3.4.2 Seed dispersal and spatial patterns 68 3.5 Discussion 71 3.5.1 Seed production 71 3.5.2 Directionality 72 3.5.3 Spatial patterns and seed dispersal distances 72 3.6 Seed dispersal scenarios for silvicultural management decisions 74 3.6.1 Seed dispersal scenarios 74 3.6.2 Conclusions for silvicultural management decisions 76 3.7 References 78 Chapter 4 – The impact of structural elements on storm-felled sites on endozoochorous seed dispersal by birds – a case study 85 4.1 Abstract 86 4.2 Introduction 86 4.3 Materials and methods 88 4.3.1 Study area 88 4.3.2 Experimental design 90 4.3.3 Data analysis 91 4.4 Results 92 4.5 Discussion 95 4.6 Conclusions for silvicultural practice 97 4.7 References 98 Chapter 5 – Soil seed banks of pioneer tree species in European tempe-rate forests: a review 104 5.1 Abstract 105 5.2 Introduction 105 5.3 Methods of literature search 107 5.4 Species-specific reproductive ecology determining the potential of soil seed banks 110 5.5 Characterization and classification of soil seed banks 112 5.5.1 Soil seed bank of Betula spp. 114 5.5.2 Soil seed bank of Alnus glutinosa (L.) GAERTN. 116 5.5.3 Soil seed banks of Salix spp. and Populus tremula L. 117 5.5.4 Soil seed bank of Sorbus aucuparia L. 118 5.6 Conclusions 119 5.7 References 120 Chapter 6 – Do birch and rowan establish soil seed banks sufficient to compensate for a lack of seed rain after forest disturbance? 134 6.1 Abstract 135 6.2 Introduction 135 6.3 Materials and methods 137 6.3.1 Study areas 137 6.3.2 Data collection 139 6.3.3. Statistical analysis 140 6.4 Results 141 6.4.1 Study A - Artificial seed burial experiment 141 6.4.2 Study B - Soil core sampling in the forest 145 6.5 Discussion 147 6.5.1 Study A - Artificial seed burial experiment 147 6.5.2 Study B - Soil core sampling in the forest 149 6.6 Conclusions 151 6.7 References 152 Chapter 7 – General discussion 160 7.1 Discussion of important aspects of regeneration ability 161 7.1.1 Fructification and seed production in Salix caprea, Betula pendula and Sorbus aucuparia 165 7.1.2 Ecological processes within the regeneration cycle of Salix caprea 167 7.1.3 Ecological processes within the regeneration cycle of Betula pendula 168 7.1.4 Ecological processes within the regeneration cycle of Sorbus aucuparia 169 7.2. Conclusions for silviculture and management recommendations 172 7.3 References 175 Table of appendix i

Aphthona spp. flea beetles were released in the Little Missouri National Grasslands (LMNG) in western North Dakota in 1999 to control leafy spurge (Euphorbia esula L.). The changes in soil seed bank composition and leafy spurge density were evaluated on two ecological sites five (2004) and ten years (2009) after Aphthona spp. release to monitor the effectiveness of the insects on weed control and associated change in plant communities. In 2009, leafy spurge stem density averaged 2 and 9 stems m-2 in the loamy overflow and loamy sites, respectively, compared to 110 and 78 stems m-2, respectively, in 1999 and 7 and 10 stems m-2, respectively, in 2004. Leafy spurge constituted nearly 67% of the loamy overflow seed bank in 1999 compared to 17% in 2004 and 2% in 2009. In the loamy seedbank, the weed represented nearly 70% in 1999 compared to approximately 11% in 2004 and 15% in 2009. As leafy spurge was reduced, native species diversity and seed count increased ten years following Aphthona spp. release. High-seral species represented 17% of the loamy overflow seedbank in 2009, an increase from 5% in 1999. However, Kentucky bluegrass, a non-target weedy species, increased over 250% in the loamy overflow seedbank from 2004 to 2009. The reestablishment of native plant species has often been slow in areas where leafy spurge was controlled using Aphthona spp. A bioassay was completed to evaluate native grass establishment when grown in soil from Aphthona spp. release and non-release sites throughout North Dakota. Native grass production was not affected when grown in soil collected from established Aphthona spp. sites (1.5 g per pot) compared to soil without insects (1.6 g per pot). The cause of reduced native grass production in sites with Aphthono spp. previously observed is unknown but may have been due to a chemical inhibition caused by the insects within the soil that no longer exists. The native warm-season switchgrass (Ponicum virgotum L.) may be an alternative to corn for efficient biofuel production; however, control of cool-season grassy weeds has been a problem in switchgrass production. Various herbicides were evaluated for smooth bromegrass (Bromus inermis Leyss.) and quackgrass [Elymus repens (L.) Gould] control in an established switchgrass stand near Streeter, ND and a weed-infested field in Fargo, ND. Switchgrass yield was higher than the control 14 mo after treatment (MAT) when aminocyclopyrachlor or sulfometuron were applied early in the growing season, but no treatment provided satisfactory long-term grassy weed control. Herbicides were reevaluated at increased rates for smooth bromegrass or quackgrass control in Fargo. Sulfometuron provided 99% smooth bromegrass control when applied at 280 g ha-1 in the fall but injured other grass and forb species as well. Sulfometuron would likely be injurious to switchgrass and could not be used for biofuel production. Aminocyclopyrachlor did not injure other grass species but only reduced smooth bromegrass control by 76% when applied at 280 g ha-1 in the fall. No treatment provided satisfactory long-term quackgrass control.

The decline of floodplain vegetation along the Lower River Murray, South Australia, has evoked recommendations for ‘environmental flows’ to restore and maintain the health of the ecosystem. To assist managers to maximize benefits from environmental flows, this thesis considers the significance of water for germination and recruitment in key floodplain plant species. Three dominant species are considered, including two trees, river red gum (Eucalyptus camaldulensis) and black box (E. largiflorens), and an understorey shrub, tangled lignum (Muehlenbeckia florulenta). The soil seed bank was dominated by terrestrial annual native plants. Among 1400 seedlings, a single river red gum was found, and no black box or lignum, suggesting that these species do not contribute to the persistent soil seed bank and rely instead on aerial seed banks (serotiny). Sampling of the soil seed bank was continued to determine when seed fall might coincide with appropriate soil moisture conditions. Responses of the soil seed bank to varied water regimes were compared to determine requirements for seedling survival. The results indicated that species richness, rapidity of response and survival time were all promoted by sustained soil moisture. Stands of eucalypts in various states of health (from very stressed to very healthy) were monitored to identify seasonal patterns in bud crops, flowering, fresh leaves and volumes of seed released from the aerial seed bank. Distinct seasonal phenological patterns were apparent, and suggested alternating flowering among individual trees (biennial for red gum, bi-annual for black box), producing an annual peak in summer. Peak seed rain occurred in summer (December–March) in healthy trees for both red gum and black box, with light seed rain continuing throughout the year. Seed fall from stressed trees was much reduced. Stressed trees responded after a second watering event, with much more varied and extended annual seed fall patterns. Lignum showed a spring peak in flowering and seed production. There was a prolific response of flowering and seeding to rainfall, but few seedlings survived. Vigorous vegetative growth occurred in existing plants in response to rainfall and watering but no new cloned plants were found during the study. An investigation of chromosomes as a potential tool to appraise the balance between sexual and asexual reproduction in lignum proved inconclusive, although a previous report of octoploidy in lignum was confirmed. Seeds from all three species and lignum cuttings were tested for their responses to varied watering regimes, based on combinations of simulated rain and flood conditions. The optimal soil moisture for continued growth and survival in all seeds and cuttings was 10 25%, with moisture values <10% causing wilting and death. The results also suggested that red gum and black box seeds which germinate in water under flooded conditions need to be stranded onto moist soil at the water’s edge within 10 days, for the seedling to continue to grow. It was also concluded that germination on rain-moistened soil is a key supplementary mechanism for recruitment, particularly between irregular flood events. For greatest benefit, the timing of environmental flows should complement any seasonal rainfall and irregular flooding that may occur. Extension of suitable soil moisture conditions (10-25%) for as long as possible after >5 mm rainfall, or after over-bank flows, would increase chances for survival of seedlings. December is the most likely month for maximal benefit from watering in the Lower Murray Valley, for germination and recruitment, based on regional rainfall and flooding patterns. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1344528 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2008

No description available.