preprints.org > biology > ecology > doi: 10.20944/preprints201909.0177.v1

Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Version 1 : Received: 15 September 2019 / Approved: 17 September 2019 / Online: 17 September 2019 (03:48:02 CEST)

1) Background: We analyzed the size structure, richness and diversity in eight permanent forest plots in the upper limit of the great Amazon basin located in the Ecuadorian parts of Cordilleras del Cóndor and Cutucú. Our hypothesis was that not all the forests of the eastern mountain ranges are homogeneous in characteristics, but rather present differences in their structure, richness and floristic diversity. In order to test this, our main objective was to classify the types of forests based on characteristics in diametric structure and species composition of the Amazonian forests of the eastern cordilleras in southern Ecuador, and also to determine the influence of critical edaphic-environmental and geomorphological factors. 2) Methods: Eight one-hectare permanent plots were installed in homogeneous and well-conserved forest stands. Four plots were located in the province of Zamora Chinchipe and four in the province of Morona Santiago. We identified and measured all trees> 10 cm at diameter breast height. For each plot, soil samples were taken, along with environmental and slope data. The multidimensional non-metric adjusted scaling (NMDS) was used to evaluate changes in climatic and geomorphological gradients. The relationship between the composition of the species at the plot level and the edaphoclimatic variables was tested using a canonical correspondence analysis (CCA). Finally, we modeled the change in species diversity (Fisher's alpha) in relation to the climatic gradients, altitudinal and geomorphological using a GLMM. 3) Results: Overall, we identified 517 species belonging to 76 families. We determined the existence of two different types of forest, the first one named Terra Firme, characterized by the presence of a larger number of species and individuals per plot, compared to the second type of forest, called Tepuy or Sandstones forest. Species richness was negatively correlated with soil phosphorus content and pH, mean annual temperature, annual precipitation and altitude. The CCA analysis showed differences in the species composition between the Terra Firme and Sandstone forests. The climatic seasonality and the concentration of cations in the soil influence the diversity of the Amazon forest communities of the southeastern cordilleras. The forests of Terra Firme, which are settled in more stable and nutrient-rich climatic areas, were more diverse. Sandstone forests are poor in nutrients and develop in areas with stronger seasonality

alpha diversity; canonical correspondence; NMDS; Sandstones Forests; Terra firme Forests

BIOLOGY, Ecology