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

Abstract

Litterfall was investigated in three even-aged Norway spruce ( Picea abies), sitka spruce ( Picea sitchensis) and beech ( Fagus sylvatica) stands on a nutrient poor-soil in Southern Denmark. Dry weights and N, P, K, S, Mg, Ca, Na, Al, and Fe concentrations and fluxes were examined in litterfall fractions. Foliage litter amounted to 90% of total litterfall. The tree stands showed a similar mean annual litterfall. In the spruce stands, annual litterfall 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 large fluctuations between years caused by drought, spruce aphid infestations and probably sea salt stress. Norway spruce responded with a long lasting elevated needle loss. Sitka spruce responded to infestations with premature needle loss during short periods. The presence of a large syrphid (Coccinellidae) population was important in regulating aphid ( Elatobium abietinum) population density. The between-year variation in element concentrations of litterfall was small whereas variations during the year were large. Interspecific levels were recognized: Norway spruce>beech>sitka spruce. High concentrations in Norway spruce were ascribed to a combination of drought, sea salt stress and elevated transpiration. In sitka spruce, aphid infestations reduced the litterfall N content. Sitka spruce showed the smallest amount of base cation fluxes with litterfall. In contrast, spruce and beech exhibited even litterfall element fluxes. Litterfall studies revealed reduced vitality in the non-native spruce stands and underlined the perception of a healthy stand of native beech.