Decomposition of litter from common woody species of kauri (Agathis australisSalisb.) forest in northern New Zealand

Rates of weight loss and release of Na, K, Ca, Mg and P were investigated for common components of kauri forest litterfall in experiments using mesh bags. Weight loss over both 3 and 12 months was maximal for broadleaf mesophyllous species such as Melicytus ramiflorus and minimal for gymnosperms (e.g. Phyllocladus trichomanoides) and sclerophyllous broadleaf species (e.g. Knightia excelsa). Tree fern and palm frond material, common in these forests, was also slow to decompose, being grouped with the gymnosperm and sclerophyllous species. The order of release of nutrients from decomposing litter was P < Mg ∼ Ca < Na ∼ K. This order varied somewhat with species and litter type. Sodium and K are lost rapidly regardless of the rate of weight loss while Mg and Ca tend to follow the weight loss trend more closely. Loss of weight and nutrients was faster for freshly picked green leaves than for senesced leaves. Agathis australis litter, which may represent up to 50% of total litterfall, loses both weight and nutrients more slowly than broadleaf mesophyll species.