Understanding of the diverse aspects affecting the regeneration ecology of species is crucial to make decisions regarding management and conservation strategies, especially in highly fragile and threatened ecosystem as the Neotropical savanna (cerrado) formations. Available knowledge of regeneration ecology of cerrado species is too limited to attain optimal or suitable management actions. The objectives of the present study were: i) analysis of the characteristic parameters of the anemochorous seed dispersal of study species Q. grandiflora, (ii) determine the spatial distribution of tree species Q. grandiflora for growth stages (seedlings to juveniles) and interrelations between the stages, and (iii) determining variables of the spatial distribution of recruitment of tree species A. tomentosum.
The present study was conducted in the cerrado Aguara Ñu of the Mbaracayú Nature Forest Reserve located in the northeast of Paraguay. The cerrado Aguara Ñu is part of the Mbaracayú Biosphere Reserve and represents one of the most important ecoregions in the world, the cerrado ecosystem. The cerrado biome encompasses areas from northeastern to southwestern Brazil, eastern Bolivia, and northern Paraguay. It is characterized by the presence of high plant and animal biodiversity and also high endemism (Myers et al., 2000). Tree species Q. grandiflora and A. tomentosum are typical species of the cerrado formation.
Based on the selected investigated regeneration cycle stages of study tree species Q. grandiflora and A. tomentosum, the present thesis describes the spatial analysis of recruitment of both study species and the anemochorous diaspore dispersal of tree species Q. grandiflora. The purpose of the present investigation is to address regeneration aspects not attained so far as certain seed dispersal aspects, such as seed densities and distances from conspecific adult trees and spatial arrangements of seedlings of species A. tomentosum. Results of the present study aim to contribute to existing information and at the same time provide new knowledge on ecological aspects so far not investigated.
Research results on seed dispersal of tree species Q. grandiflora revealed that dispersal can be modeled by inverse modelling considering isotropy and lognormal density function presenting mean dispersal distances of 10.69 to 62.48 m. Estimations of the fruit production of a seed tree yielded a total 50671 to 70632 (DBH = 70 cm). Results of spatial arrangement of seedlings and juveniles revealed a significant distance effect to conspecific adult trees. Moreover, results also showed: (i) highest densities or intensities (m2) of seedlings (heights <50 cm) close to the conspecific adult trees and (ii) a shift of intensity of seedlings with increase of growth stage or size for tree species Q. grandiflora. Additionally, seedlings (up to 200 cm height) of study species Q. grandiflora indicated gradual decreasing clumping patterns and juveniles (200 – 500 cm height) presented clumping patterns.
Modelling results of spatial patterns of seedlings (heights ≤ 200 cm) of study tree species A. tomentosum revealed aggregation patterns. Moreover, shade effect resulted to be a statistical significant factor for the establishment of seedlings of tree species A. tomentosum (p-value = 0.0266), whereas distance effect to seed tree resulted not significant (p-value= 0.4936).
Considering the findings of seed dispersal and spatial patterns analysis of tree species Q. grandiflora and A. tomentosum some management aspects to be attained for conservation purposes are avoiding fragmentation of the ecosystem, management of the spatial and time fire frequency and maintain minimum amount of seed trees per unit area in order to guarantee successful recruitment.:1. Introduction 1
References 8
2. Materials and Methods 13
2.1 Characterization of the cerrado biome 13
2.2 Description of the study area and study sites 15
2.3 Characterization of the study tree species 23
2.3.1 Qualea grandiflora (Mart.) 23
2.3.2 Aspidosperma tomentosum (Mart.) 24
2.4 Principles and selection criteria 25
2.5 Data collection 26
2.5.1 Seed dispersal 26
2.5.2 Spatial patterns of plants 27
2.6 Data analysis 28
2.6.1 Statistical analysis of data 28
2.6.2 General statistical procedures of data analysis 30
2.6.3 Spatial point process analysis – Inverse modelling and spatial point patterns 31
2.6.4 Spatial point patterns analysis procedure 33
2.6.4.1 Descriptive statistics in spatial point patterns 36
2.6.4.1.1 Distance effect of seedlings from seed trees (rhohat function) 36
2.6.4.1.2 Pair correlation function (pcf) 36
2.6.4.2 Point process modelling 38
References 43
3. Seed dispersal of Qualea grandiflora (Mart.) 49
3.1 Introduction 49
3.2 Methodology 51
3.2.1 Data collection and seed trap design 51
3.2.1 Data analysis – inverse modelling 53
3.3 Results 58
3.3.1 Seed density 58
3.3.2 Inverse modelling results – seed production, dispersal and distances 60
3.3.2.1 Isotropic modelling 61
3.3.2.2 Anisotropic modelling 63
3.3.2.3 Statistical comparison isotropy vs. anisotropy 66
3.4 Discussion 67
3.4.1 Applied methodology for seed dispersal – trap design and inverse modelling 67
3.4.2 Seed dispersal modelling 69
3.5 Conclusion 74
References 75
4. Spatial analysis of Qualea grandiflora (Mart.) 80
4.1 Introduction 80
4.2 Methodology 82
4.2.1 Data collection – Field sampling 82
4.2.2 Data analysis 85
4.2.2.1 Spatial point pattern – Explorative analysis 85
4.2.2.2 Point process modelling (Poisson and Gibbs models) 87
4.2.3 Results 89
4.2.3.1 Spatial distribution of individuals of study species 89
4.2.3.2 Modelling distance effect of recruitment to adult trees 95
4.2.4 Discussion 102
4.2.4.1 Applied methodology for spatial analysis of study species 102
4.2.4.2 Spatial arrangement of study species 103
4.2.5 Conclusion 109
References 109
5. Spatial analysis of Aspidosperma tomentosum (Mart.)115
5.1 Introduction 115
5.2 Methodology 117
5.2.1 Data collection – Field sampling 117
5.2.2 Data analysis 120
5.2.2.1 Spatial point pattern – Explorative analysis 120
5.2.2.2 Point process modelling – Replicated point patterns 120
5.3 Results 123
5.3.1 Spatial distribution of natural regeneration of study species 123
5.3.2 Modelling shade and distance to seed tree effect on natural regeneration of study species 130
5.4 Discussion 133
5.4.1 Applied methodology for data collection and analysis 133
5.4.2 Spatial distribution of natural regeneration of study species 134
5.5 Conclusion 139
References 140
5. Concluding discussion and summary 146
6.1 Regeneration ecology of Qualea grandiflora and Aspidosperma tomentosum 146
6.1.1 Inferences on relation of seed dispersal and spatial distribution of recruitment of Qualea grandiflora 146
6.1.2 Inferences on spatial patterns of recruitment of Aspidoserma tomentosum 149
6.2 Management implications for Qualea grandiflora Aspidosperma tomentosum 150
6.3 Future research 153
6.4 Concluding summary 154
References 155
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:33167 |
| Date | 14 February 2019 |
| Creators | Da Ponte Canova, Giovanna |
| Contributors | Wagner, Sven, Berger, Uta, Pivello, Vania, Technische Universität Dresden |
| Publisher | Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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