BIOMASS STUDIES IN SEMINATURAL ECOSYSTEMS INFLUENCED BY SCYTHING AT THE SOLENDET NATURE-RESERVE, CENTRAL NORWAY .3. TALL HERB BIRCH FOREST

Investigations of the above- and belowground biomass on permanent plot s in a tall herb birch forest community (Lactucion alpinae alliance) w ere carried out in 1993 and 1994. The results show that the total biom ass decreases with increasing scything frequency (not scythed since 19 50 - scythed biennially- scythed annually) from about 10-13 000 kg.ha( -1) to about 3-5000 kg.ha(-1). The ratio of aboveground to belowground biomass also decreases from about 0.8 to about 0.4-0.6. The total num ber of shoots shows the opposite tendency and increases with increasin g scything frequency. The species composition changes from a community dominated by tall herbs as Aconitum septentrionale, Geranium sylvatic um and Angelica archangelica to a more grass-dominated community (e.g. Agrostis capillaris, Deschampsia flexuosa). There are also considerab le differences in biomass and number of shoots between the two years. This may partly be due to a methodological bias and partly to fluctuat ions in climatic conditions.