Models of early destruction of Scots pine needles in the middle taiga of Eastern Fennoscandia

Decomposition of needle litter was studied in a series of three successive two-year experiments in a pine forest. The effect of the weather conditions proved to be significant only in the first two months of needle decomposition. Analysis of the dynamics of needle degradation in our experiments shows the early needle destruction process falls into three phases: fast (the first warm period, up to ~30% needle mass loss); moderate (from the onset of the first cold period to the onset of the second cold period, ~30% to ~55% total needle mass loss); slow (from the onset of the second cold period, from ~55% total needle mass loss onward). A comparison of empirical data on degradation dynamics with the asymptotic model revealed a 10-13% misfit in annual needle loss. The reason is the specific features of decomposition of certain chemical components of needles, especially lignin/AUR. An attempt was made to simulate the destruction of needles based on the decomposition patterns of their various chemical components. The resultant model and its simplified version quite accurately reflect the destruction characteristics but have some substantial limitations.