Amounts of litter fall in some pine forests in a European transect, in particular Scots pine

Pine litter fall data, mainly needle litter, were available for 64 plots in a transect from the Arctic Circle in Fennoscandia (41 plots) to southern S pain (22 further plots in continental Europe) and one in the American Midwe st). Data originated from a total of eight pine species. Regressions were c alculated mainly for needle litter fall and to some extent for total litter fall. We obtained a highly significant linear relationship for needle litt er fall and latitude (R-adj(2) = 0.285; n = 58; P < 0.001) when using needl e litter fall data from all pine species. Combining sites in the boreal and Atlantic climates gave an R-adj(2) of 0.732 with n = 45 (P < 0.001). A mul tiple linear relationship using stand age, latitude and basal area was high ly significant and gave an R-adj(2) value of 0.412 (n = 54; P < 0.001). For the amount of Scots pine needle litter in Fennoscandia, the best simple li near relationships were obtained with site index (H 100) (R-adj(2) = 0.349) , latitude (R-adj(2) = 0.331) and basal area (R-adj(2) = 0.324) as predicto r variables, whereas the regressions on altitude and stand age were signifi cant only with P < 0.01. An X-2 function for stand age improved the relatio nship with age to R-adj(2) = 0.243. Multiple regression relationships for F ennoscandia between needle litter fall and latitude plus basal area and tha t to latitude plus basal area plus age were highly significant (R-adj(2) = 0.605 and 0.661, respectively, with n = 41). In a stepwise procedure using data from the same sites, combinations of the factors latitude, site index, basal area and stand age could explain as much as 78 % of the needle litte r fall. For total litter fall as measured by the same method as needle litt er we related data from 32 sites to that of needle litter fall and obtained highly significant relationships indicating that needle litter fall may be used as an index for total litter fall. (C) 1999 Inra/Editions scientifiqu es et medicales Elsevier SAS.