Fine-root biomass and necromass in limed and fertilized Norway spruce ( Picea abies (L.) Karst.) stands

Abstract

Fine-root biomass, biomass production and necromass were studied using soil cores and ingrowth cores in Finland and Sweden in four Picea abies stands repeatedly limed and fertilized with N, and PK separately and in combination. The fine-root biomass was smaller than control, though not always significantly, in those plots that had received lime (Ca, NCa, PKCa) or PK alone. These plots also had a large fine-root necromass. The lower fine-root biomass values in the PK-, Ca-, PKCa- and NCa-plots may have been caused by smaller fine-root production and greater mortality since in these plots the ingrowth of fine roots was also the smallest, and the proportion of dead fine roots in the soil cores and in the ingrowth cores highest. The negative effect of fertilizers with lime or PK alone, and PKCa on the stem volume growth may be related to the smaller fine-root biomass and, especially, fine root growth. Those plots that had received nitrogen alone, or together with PK had similar or larger fine-root biomass than control, except in the Heinola experiment which was situated on a fertile soil type in southern Finland. The larger biomass values were caused by higher fine-root production since the ingrowth of fine roots was also greatest in these plots. The results suggest that the differences in the above-ground growth between stands of varying nutritional treatment on the same site may be related to the correspondent differences in the fine-root biomass, and especially, fine-root growth.