Decomposition of tree root litter in a climatic transect of coniferous forests in northern Europe: A synthesis

The purpose of this study was to understand the variation in root litter ma ss-loss rates in a climatic transect across a large region ranging from the Arctic Circle (66 degrees N) in Scandinavia to Berlin (52 degrees N) in no rth-east Germany, dominated by coniferous monocultural forests. To investig ate the combined influence of litter quality and climate, data were used fr om 37 sites and plots at which root litters of three coniferous species (Pi nus sylvestris, Pinus contorta and Picea abies) had been incubated. In spit e of the considerable climatic differences among sites, there were no stron g relationships between any climatic variable and the 1st-yr mass loss (ran ge 17.0-40.9%). For the 1st-yr mass loss, the average annual temperature wa s the most rate-regulating factor for all litter combined, with a value for R-adj(2) of 0.186. Substrate quality also had an influence. Thus, for the whole region lignin concentration was significant, with a value for R-adj(2 ) of 0.142. For the separated groups of pine and spruce stands the value fo r r(2) increased but the factor average temperature still dominated and for pine the R-adj(2) reached a value of 0.346. Over the region N concentratio n in the fresh pine root litter was significant (R-adj(2) = 0.232). For the root litter of P. abies the average temperature in duly was the strongest rate-regulating climatic factor, with a value for R-adj(2) of 0.381. A comb ination of temperature in July and the initial P concentration in the litte r gave an R-adj(2) value of 0.713 for P. abies litter, thus explaining abou t 71% of the variation.