Environmental Factors Influencing Species Richness Expression in Grasslands of the Colombian Orinoquia

Abstract

The relationships between environmental characteristics and species richness in the grasslands of the Colombian Orinoquia are presented and analyzed using an ordinal logistic regression model. Ordinal and scale covariates were included, and their bivariate significance was assessed using Spearman's rho and Kendall's Tau-b. The covariates that showed statistical significance with the weighted richness thresholds (WRT) and defined the model were the soil depth and the soil moisture regime, both of which had positive correlations. In contrast, the percentage of bare soil and the monthly minimum temperature showed negative correlations. This contribution highlights the relevance of articulating and combining the floristic and phytosociological characterization of grassland vegetation to advance the predictive studies aimed at defining and understanding the potential divergent relationships between the vegetation and the basic attributes of the natural environment, along with their implications for conservation.

Keywords: cumulative probability ordinal and binary regressions; flora and vegetation of the Colombian Orinoquia; neotropical savannas; predictive richness models.

Figure 1

Physiography in grasslands and meadows of the alliances: (a) Paspalion carinato—pectinati in High plain; (b) Steinchismo laxae—Andropogonion bicornis in Alluvial plain; (c) Rhynchosporo barbatae—Andropogonion virgarti in Alluvial plain; (d) Axonopodo aurei-Trachypogonion spicati in High plain; (e) Paspalo pectinati—Axonopodion aurei in High plain; (f) Andropogono virgati—Axonopodion ancepitis in Alluvial plain; (g) Hyptio brachiatae—Trachypogonion spicati in High plain; (h) Bowdichio virgilioidis—Curatellion americanae in High plain.

Figure 1

Physiography in grasslands and meadows of the alliances: (a) Paspalion carinato—pectinati in High plain; (b) Steinchismo laxae—Andropogonion bicornis in Alluvial plain; (c) Rhynchosporo barbatae—Andropogonion virgarti in Alluvial plain; (d) Axonopodo aurei-Trachypogonion spicati in High plain; (e) Paspalo pectinati—Axonopodion aurei in High plain; (f) Andropogono virgati—Axonopodion ancepitis in Alluvial plain; (g) Hyptio brachiatae—Trachypogonion spicati in High plain; (h) Bowdichio virgilioidis—Curatellion americanae in High plain.