Edaphic correlates of tree species diversity, composition, and distribution in an eastern arc biodiversity hotspot, Tanzania

This study explored the edaphic correlates of tree species diversity, composition and distribution in the Amani Nature Reserve (ANR) and Udzungwa Mountains (UMF). Using canonical correspondence analysis, different ecological gradients explained plant community patterns. In ANR, species richness decreased significantly with pH (r = -0.383, p = 0.03; r = -0.422, p = 0.016) at 0-15 cm and 30-45 cm depth respectively and percentage coarse silt at 30 cm (r = -0.416, p = 0.018). Further, species richness and diversity increased along a gradient of percentage organic carbon (r = 0.35 and r = 0.22) respectively and decreased with bulk density (r = -0.24 and -0.29 at 15 and 30 cm respectively) in UMF. There was pronounced variation in edaphic correlates of tree community patterns between sites. Soil pH was the strongest edaphic correlate of species composition and distribution in ANR while percentage organic carbon was a strong edaphic correlate in UMF. Stronger effects by soil pH indicate the influence of soil chemical properties in the study sites. Variation in the influence of edaphic correlates to tree community patterns between the two sites suggests a need for site-specific assessment of edaphic properties.