SCOTS PINE NEEDLE SURFACES ON RADIAL TRANSECTS ACROSS THE NORTH BOREAL AREA OF FINNISH LAPLAND AND THE KOLA-PENINSULA OF RUSSIA

To gain an understanding of the characteristics of the needle surfaces of naturally regenerated Scots pine (Pinus sylvestris L.) and their g eographical distribution, eight physicochemical variables were investi gated within the north boreal forest area. The visibly undamaged needl es were collected in autumn 1990 from 114 plots (3-5 pines per plot) a long radial transects from the Monchegorsk and Nikel smelters, emittin g SO2 and heavy metals, on the Kola Peninsula, Russia, to Finnish Lapl and. The needles were examined by scanning electron microscopy (SEM) a nd measured for surface wettability using the droplet contact angle (D CA) method Significant geographical south-north and west-east patterns could be observed in needle surface characteristics, correlating with emissions from the smelters and to climate. Despite the slightly high er initial DCAs (61.4-87.6 degrees) towards the north, the pine needle surfaces of the northernmost transects exhibited higher annual needle wettability change (ANWC) and wax erosion rate (AWER), expressed as t he reduction in DCAs and epistomatal wax tube distribution (WTD) durin g one year, respectively, but a lon er occurrence of particles and fun gal hyphae than those of more southern transects. The higher ANWC was related to higher atmospheric SO2 concentration, and to the lower long -term temperature sum, but not clearly to annual precipitation. In the Monchegorsk smelter area, the current needles exhibited, on average, a 15% higher WTD and seven degree larger DCA, resulting in more hydrop hobic needle surfaces than in Finnish Lapland, but during their first year, both the AWER and ANWC, were greatly increased. In Finnish Lapla nd. 30%, of all the epistomatal wax tubes disappeared from the needle surface during the first year, the value being 70% for the pines locat ed 8 km from the smelter. The mineral composition of the particles dep osited on the needle surfaces mirrored that of the minerals being prod uced by the smelters (e.g. FexSx, CuFeS2, NixSx, FexOx). Stomatal dens ities were in the range of 71.1-141.7 stomata mm(-2). The lower densit ies of stomata on needles close to the smelters correlated with reduce d number of needle age classes of the pines, higher dry weights, highe r pollutant accumulation and lower Mn and Zn concentrations in the nee dles. The AWER and ANWC were able to indicate the most seriously deter iorated needle surfaces on a regional scale, e.g. including the surrou ndings of both smelters, although the plot-specific relationships betw een 'needle surface variables' and 'pollution variables' were generall y weak. The present study showed that the exposure of pine needles to the combined effects of ambient pollutants and harsh climate led to a deterioration in the physicochemical characteristics of the epicuticul ar wax, which may have serious ecophysiological consequences in the lo ng term. Copyright (C) 1996 Elsevier Science Ltd