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 Spain (22 further plots in continental Europe) and one in the American Midwest). Data originated from a total of eight pine species. Regressions were calculated mainly for needle litter fall and to some extent for total litter fall. We obtained a highly significant linear relationship for needle litter fall and latitude (R-adj(2) = 0.285; n = 58; P < 0.001) when using needle 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 multiple linear relationship using stand age, latitude and basal area was highly 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 linear 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 predictor variables, whereas the regressions on altitude and stand age were significant only with P < 0.01. An X-2 function for stand age improved the relationship with age to R-adj(2) = 0.243. Multiple regression relationships for Fennoscandia between needle litter fall and latitude plus basal area and that 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 litter fall. For total litter fall as measured by the same method as needle litter 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 scientifiques et medicales Elsevier SAS.