Structural and Environmental Variables Affecting Biodiversity Conservation in Agroforestry Systems in the Northern Ecuadorian Amazon
| dc.contributor.advisor | Cota-Sánchez, J. Hugo | |
| dc.contributor.advisor | Grijalva, Jorge | |
| dc.contributor.committeeMember | Lamb, Eric | |
| dc.contributor.committeeMember | Lane, Jeffrey | |
| dc.contributor.committeeMember | Sheard, John | |
| dc.contributor.committeeMember | Benson, James | |
| dc.creator | Vera Velez, Roy Roger | |
| dc.creator.orcid | 0000-0002-4716-4390 | |
| dc.date.accessioned | 2023-02-28T20:39:11Z | |
| dc.date.available | 2023-02-28T20:39:11Z | |
| dc.date.copyright | 2020 | |
| dc.date.created | 2020-11 | |
| dc.date.issued | 2020-12-03 | |
| dc.date.submitted | November 2020 | |
| dc.date.updated | 2023-02-28T20:39:12Z | |
| dc.description.abstract | The Northern Ecuadorian Amazon (NEA) is recognized as biodiversity hotspot that contains unique endemic plant species. However, unsustainable agricultural practices, such as more frequent cycles of shifting agriculture (SA), threat the NEA’s forests endurance with negative consequences for biodiversity levels and ecological functions. In this study, I examined the spatial and temporal dynamics of the diversity of native trees across various types of agroforestry systems (AFS) subjected to SA. That is, the degree of existing risk of endangerment of tree species, the rapid change in floristic composition of mature forests converted to AFS, and the recovery pace of forest communities following abandonment. Transforming mature forest communities (MFC) to different AFS leads to a decrease in alpha diversity up to 75%. AFSs preserve 56% of the beta diversity compared to MFC; at least 8% of the species are threatened and the demographic status of 92% species is unknown. MFCs seem to regain their original structure after AFS abandonment. In the second part, I investigated whether AFS reverses the effect of intensified SA in cocoa (Theobroma cacao) agrosystems. I addressed the extent to which multispecific cocoa AFSs buffer the impact of reduced fallows in SA on loss of species. Tree diversity showed a gradual decrease from low to intermediate to high intensification SA in cocoa AFS, with values of 46, 29, and 12 species richness. The absence of fallows in SA affects tree presence, leading to changes in floristic composition in 30% fewer species compared to the beta diversity in cocoa AFSs experiencing long resting phases. Nonetheless, the similar beta diversity between low and intermediate intensification levels of SA suggests a concomitant delay in forest degradation rates. Finally, I examined the extent to which beta diversity in AFS reverses the effect of shorter SA fallow periods in the soil properties of cocoa (T. cacao) agrosystems. Agroforestry systems, combined with SA, shields the negative outcome of intense land-use on the soil’s nutrients. The arboreal cover maintains the soil fertility needed for crop performance and food sustainability. The dominance of certain tree species (Vochysia leguiana, Inga edulis, Cordia alliodora) is essential to support adequate dynamic levels of nutrient cycling with more intense fallow periods, whereas some other species (Virola flexuosa, Chrysophyllum amazonicum, Ocotea bofo) have an apparent effect on soil acidity. I conclude that AFS have the potential for enhancing sustainable forest management and preservation of endangered tree species. | |
| dc.format.mimetype | application/pdf | |
| dc.identifier.uri | https://hdl.handle.net/10388/14496 | |
| dc.subject | Agroforestry | |
| dc.subject | shifting agriculture | |
| dc.subject | biodiversity | |
| dc.subject | tropical forest | |
| dc.subject | ecosystem services | |
| dc.title | Structural and Environmental Variables Affecting Biodiversity Conservation in Agroforestry Systems in the Northern Ecuadorian Amazon | |
| dc.type | Thesis | |
| dc.type.material | text | |
| thesis.degree.department | Biology | |
| thesis.degree.discipline | Biology | |
| thesis.degree.grantor | University of Saskatchewan | |
| thesis.degree.level | Doctoral | |
| thesis.degree.name | Doctor of Philosophy (Ph.D.) |