Base Cation Leaching From the Canopy of a Rubber (Hevea brasiliensis Willd. Muell-Arg) Plantation at Ikenne, South West Nigeria

Base cations are essential to the sustainability of forest ecosystems. They are important for neutralizing the acidifying effects of atmospheric deposition. There is the need for in-depth understanding of base cation depletion and leaching from forest canopy. This is important particularly due to the increasing acidification and anthropogenic influences that alter biogeochemistry of the ecosystems. Availability and leaching of base cations (Ca2+, Na+, P, and K+) from the tree canopies were examined in two rubber (Hevea brasiliensis Willd. Muell-Arg) stands (40- and 15-year-old) in southwestern part of Nigeria. The chemical composition of throughfall in the area was dominated by calcium. Concentrations of Ca2+, Na+, P, and K+ were relatively high throughout the sampling periods. Significant differences (P < 0.05) were observed between precipitation and throughfall in concentrations of nutrient elements, and the enrichment occurred within the rubber plantation for all the nutrient elements. Ca2+ is mainly from precipitation , while over 70% of total K and total Mg were probably leach from canopy. Total annual nutrient returns via throughfall for the 15-year-old stand were 28.39, 4.49, 38.9, and 3.54 kg ha year -1 for Ca2+, Mg2+, K+ and Na+ respectively, while that of the 40-year-old stand were 22.7, 3.64, 36.3, and 3.17 kg ha year -1 for Ca2+, Mg2+, K+ and Na+ respectively.