Abstract:
The southeastern Ecuadorian Andes belong to the tropical eastern Andes and represent one of the global centers of vascular plant diversity. They are one of the most biodiverse regions on earth. Despite the immense value and importance of the ecosystems existing here, we must confront the endangerment of these largely unexplored habitats. Additionally, palaeoenvironmental studies are rarely implemented, even though past processes play a major role in the development of ecosystems and biodiversity. In the present study, we carry out an investigation of late Quaternary vegetation, climate and fire dynamics in order to gain a deeper understanding of past environmental changes in the Podocarpus National Park (PNP) region in the southeastern Andes of Ecuador. The results contribute essential background information for conservation strategies in the PNP area and provide a further step towards a better assessment of the ecosystem’s responses to future global change. Palynological and multi-proxy analyses of three sediment records are used to reconstruct past vegetation dynamics and to reveal the influencing factors. The combination of several available pollen records and the establishment of a rule of thumb for vertical shifts of the upper forest line (UFL) facilitated the first regional environmental reconstruction and visualization for an area of the PNP since the last glacial maximum (LGM). The implementation of multivariate data analysis of modern pollen data further extends our knowledge of the representation of vegetation patterns in pollen data. Additionally, comparisons between plant diversity and palynological richness (pollen and spore diversity) provide initial insights into how pollen diversity data reflects vegetation diversity in a highly diverse area. The analysis of the record from Laguna Campana, located west of the PNP, yields a detailed environmental reconstruction for the study site over the past ca. 500 years and reveals continuous anthropogenic impact, which affected local vegetation development and biodiversity. Two pollen records from the Cerro Toledo area in the southern PNP reach back ca. 20,000 years ago and the analysis of these pollen records indicates changes in vegetation distribution and composition primarily due to past climate dynamics. The regional environmental reconstruction shows that during the LGM the UFL was located several hundred meters lower than its current level and that páramo vegetation widely dominated the landscape of the study region due to cold and wet climatic conditions. Rising temperatures since late glacial times led to a gradual shift of forest upslope. The results of this study clearly show that overall similarities between sites contrast with local differences in late Quaternary environmental history in the northern Andes and even within the study region. The high variety is caused by the complex and heterogeneous Andean habitats as well as by site-specific relevance and interactions of natural and anthropogenic factors determining vegetation patterns and developments. Modern pollen data analysis shows that vegetation patterns are generally well reflected by pollen deposition data, which contributes to the interpretative basis of the fossil pollen records. Finally, this study suggests that palynological richness as a measure for vegetation diversity in the research area is complex, and future investigations on this topic are necessary to elaborate on the preliminary results obtained so far. 3
