SummaryDifferent trends have been demonstrated in the changes in composition taking place in sub‐samples of the same ash litter placed in nylon hair‐nets on neighbouring sites with mull and moder‐type humus forms. Similar trends have been shown to occur for oak litter and ash litter placed on the same moder site. The percentage nitrogen content of ash litter on the mull site remains virtually constant during the first 7 months of decomposition whereas on the moder site the content increases steadily for both ash litter and oak litter. The nitrogen content of oak litter is increased by considerable addition from outside. Possible sources of this additional nitrogen are considered. Extraction with hot water of litter at different stages of decomposition shows that the initially large water‐soluble fraction, which is poor in nitrogen, is leached out more quickly from ash than from oak