A comparison of litterfall and element fluxes in even aged Norway spruce, sitka spruce and beech stands in Denmark

Litterfall was investigated in three even-aged Norway spruce (Picea abies), sitka spruce (Picea sitchensis) and beech (Fagus sylvatica) stands on a nu trient poor-soil in Southern Denmark. Dry weights and N, P, K, S, Mg, Ca, N a, Al, and Fe concentrations and fluxes were examined in litterfall fractio ns. Foliage litter amounted to 90% of total litterfall. The tree stands sho wed a similar mean annual litterfall. In the spruce stands, annual litterfa ll was correlated negatively with the current year increment and positively with the previous year increment. Annual litterfall in beech was constant during the 6 study years whereas Norway spruce and sitka spruce showed larg e fluctuations between years caused by drought, spruce aphid infestations a nd probably sea salt stress. Norway spruce responded with a long lasting el evated needle loss. Sitka spruce responded to infestations with premature n eedle loss during short periods. The presence of a large syrphid (Coccinell idae) population was important in regulating aphid (Elatobium abietinum) po pulation density. The between-year variation in element concentrations of l itterfall was small whereas variations during the year were large. Interspe cific levels were recognized: Norway spruce>beech>sitka spruce. High concen trations in Norway spruce were ascribed to a combination of drought, sea sa lt stress and elevated transpiration. In sitka spruce, aphid infestations r educed the litterfall N content. Sitka spruce showed the smallest amount of base cation fluxes with litterfall. In contrast, spruce and beech exhibite d even litterfall element fluxes. Litterfall studies revealed reduced vital ity in the non-native spruce stands and underlined the perception of a heal thy stand of native beech. (C) 1999 Elsevier Science B.V. All rights reserv ed.