Nutrient ecology, vegetation and biomass of two South-Greenlandic birch forest sites

Two semi-dry birch forest sites were studied in Narssarssuaq (hemiarctic, subcontinental) and in Qingua-dalen (hemiarctic, suboceanic). The height of the scrub is only 1.3-2.8 m. A heavy podsolic soil prevails with thick moss-litter-humus and iron-rich horizons. The biomass of litter and dead material is high (1595 g/m2). Deschampsia flexuosa prevails in the field layer. Twenty site types were distinguished in the vegetation transect across the Qingua-dalen. Mesic and moist types are dominant on the north exposed slope without any vertical differences which are more clear on the opposite side of the valley. The Ca content in the soil is high. particularly at Narssarssuaq (5-10 times higher than for K and Mg). The somewhat increased Na content in the humus layer at Narssarssuaq may be caused by minerals in the sea spray at this site which is relatively close to the fjord. Loss on ignition and total N in the humus layer are approx. low at both sites. probably because of considerable mixing with the mineral soil. Both the Ca and the N content in the plants are higher at Narssarssuaq than in those from Qingua-dalen. and are, generally, also higher than on oligotrophic subalpine/subarctic (northern oroboreal) birch forest sites of Fennoscandia. The high Na content in the sea spray at Narssarssuaq is reflected in a high content of Na in the birch bark and in Cladina lichens. "Total'' sums of sugars (glucose+fructose+sucrose) in all parts of birch determined were higher in Qinguadalen than at Narssarssuaq except in older twigs and roots. Starch contents, generally show the same tendency, due to higher temperature (south exposed slope) and higher net assimilation. There were no differences in the contents of "total" carbohydrate (total sugar + starch) in other species between the two study sites.