Changes of tannin and nutrients during decomposition of branchlets of Casuarina equisetifolia plantation in subtropical coastal areas of China

A litterbag experiment was conducted to investigate the changes of tannins and nutrients in branchlets at different decomposition stages of Casuarina equisetifolia in southern subtropical coastal zone, China, using the colorimetric assays. The time required for the loss of half of the initial dry weight (t(50)) was 9.13 months. Total phenolics (TP), extractable condensed tannins (ECT), protein-bound condensed tannins (PBCT), total condensed tannins (TCT) and protein precipitation capacity (PPC) of branchlets litter decreased rapidly, while fibre-bound condensed tannins (FBCT) increased during decomposition. Nitrogen and phosphorus concentration of the branchlet litter both increased gradually during decay. Negative correlations between TP and nitrogen or phosphorus, as well as TCT and nitrogen or phosphorus were found. These chemical changes enhanced the current knowledge on the potential ecological role of nutrient transformation in tannins in C. equisetifolia plantations.