Spatial Pattern Analysis of Tarenna Rwandensis (Rubiaceae), an Endemic Tree Species of Nyungwe National Park (Rwanda)

Abstract

The spatial pattern of individuals of T. rwandensis, an endemic ligneous species of Nyungwe National Park was analyzed. Individual was classified into three age-based categories: seedlings, saplings and adults to detect intraspecific interactions. Three rectangular plots of 21´9m each were made at Uwinka and each individual T. rwandensis identified was mapped using cartesian coordinates (x,y). The point pattern generated was analyzed by means of Ripley’s K function for univariate analysis and O-ring statistics for bivariate analysis to compare observed sets of values from the data.

Our study revealed that T. rwandensis doesn’t regenerate adequately; we observed a very low number of seedlings compared to other age categories. The univariate analysis of the observed individuals showed that seedlings are clumped from the scale of 0.5 m up to 4m.  Saplings and adults show contrasting spatial patterns in different plots due to competition and environmental heterogeneity. Concerning bivariate analysis, the study showed neutral interactions between adults and seedlings for all considered scales in plot 1 whereas saplings exhibit neutral interactions around adults only at the scale of 0.5 up to 1.5m. In this plot 1, we found that seedlings and saplings have clear spatial neutral interactions for the scale of 0.5 up to 2.5m scale. In plot 1, seedlings show neutral interactions around adults for all considered whereas saplings exhibit neutral interactions around adults only at the scale of 0.5 up to 1.5m. Seedlings exhibit a clear spatial neutral interaction around saplings from 0.5 up to 2.5m scale in this plot 1. In the plots 2 and 3, spatial neutral interactions have been observed between adults and saplings for all scales considered.

Key words: Spatial pattern, Tarenna rwandensis, regeneration, spatial interactions and Nyungwe National Park