Metla Project 3204

Nutrient dynamics and biomass allocation in different tree species: effects of nitrogen deposition and drought

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Duration: 1997-2002   Keywords: Scots pine, carbon and nitrogen allocation, drought, fine root, nitrogen deposition, nutrient uptake, orway spruce, rhizosphere, silver birch, soil N and carbon transformations, tree species

Objectives

The aim of this research is to study the effects of nitrogen deposition and periodical drought on nutrient dynamics and carbon allocation in Picea abies (Karst.), Pinus sylvestris (L) and Betula pendula (Roth.) and on soil microbial activities.

The aim is especially to determine the response of the different tree species to drought and elevated nitrogen by studying:
a) growth dynamics and carbon allocation to below-ground and above-ground parts
b) nitrogen and nutrient uptake and allocation and the significance of internal cycle of N and nutrients
c) soil carbon and nitrogen transformations and microbial populations active in the transformations
d) allocation of carbon and nitrogen to root exudates and soil microbial population in different tree species.
In addition, the aim is to study the effect of different tree species on soil carbon and nitrogen transformations and microbial populations active in the transformations.

Results

A semi-mature Norway spruce (Picea abies, Karst) stand growing on a fertile forest soil is rather sensitive to the effects of seasonal drought in soil. The soil microflora is the most sensitive to the reduction of soil water content, but it also restores rapidly after rewetting of the soil. In addition, a short pulse of markedly increased activity can occur in the beginning of the restoration. Nitrogen deposition enhances the activity of soil microbes. Norway spruce fine roots, foliage and growth react rather rapidly to water deficiency in the soil also. Already after a few months long dry period marked negative changes can be detected in the amount and activity of tree fine roots.

If the water stress occurs during several growing seasons consecutively cumulative negative effects occur in the Norway spruce trees; the amount of fine roots, needles and the needle nutrients and tree growth decrease. The stand is not able to restore during the end of one growing season even if the soil water content would markedly increase. However, a water stress occurring during 1 to 4 consecutive growing seasons does not cause death of individual or group of trees in the stand growing on a fertile soil.

Nitrogen deposition of 10-30 kg/ha/a partly decreases the harmful effects of water deficiency in Norway spruce. The additional nitrogen enhances the restoration of the damaged parts of the trees and increases the growth of new root and needle biomass after rewetting of the soil. On the other hand the added nitrogen and drought can have negative interactions in Norway spruce by decreasing the uptake and concentration of boron in the tree needles. Similar results were obtained in greenhouse experiments in which the interactions of seasonal drought and nitrogen deposition on the nutrient and biomass dynamics of 3 to 5 year-old silver birch (Betula pendula, Roth.), Scots pine (Pinus sylvestris, L.) and Norway spruce were tested.

Project leader: Lumme, Ilari
The Finnish Forest Research Institute, Vantaa Unit, PL 18, FI-01301 VANTAA, FINLAND
Phone: +358 29 532 5448
E-mail: ilari.lumme@metla.fi

Other researchers: Hamberg, Leena (2002), Helmisaari, Heljä-Sisko, VA (1997-2001), Koskela, Merja-Leena, ES (2000), Makkonen, Kirsi, VA (1997), Nieminen, Tiina, VA (1997-98), Nokso-Koivisto, Antti (2000), Nöjd, Pekka, VA (1999), Paavolainen, Laura (1997), Priha, Outi (1998), Smolander, Aino, VA (1997-2002)


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Updated 12.06.2012
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