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The vertical distribution of N and K uptake in relation to root distribution and root uptake capacity in mature Quercus robur , Fagus sylvatica and Picea abies stands

Göransson, Hans ; Ingerslev, Morten ; Wallander, Håkan

In: Plant and Soil, 2008, vol. 306, no. 1-2, p. 129-137

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    Titre
    • The vertical distribution of N and K uptake in relation to root distribution and root uptake capacity in mature Quercus robur , Fagus sylvatica and Picea abies stands
    Auteur
    • Göransson, Hans. Institute of Integrative Biology, ETH, Universitätstrasse 16, CHN 8092, Zürich, Switzerland
    • Ingerslev, Morten. Danish Forest Landscape Research institute, Hoersholm Kongevej 11, 2970, Hoersholm, Denmark
    • Wallander, Håkan. Department of Microbial Ecology, Lund University, Ecology Building, SE-223 64, Lund, Sweden
    Type de document
    • Postprint
    Identifiant OAI-PMH
    • oai:doc.rero.ch:319478
    Summary
    We have measured the uptake capacity of nitrogen (N) and potassium (K) from different soil depths by injecting 15N and caesium (Cs; as an analogue to K) at 5 and 50cm soil depth and analysing the recovery of these markers in foliage and buds. The study was performed in monocultures of 40-year-old pedunculate oak (Quercus robur), European beech (Fagus sylvatica) and Norway spruce (Picea abies (L.) Karst.) located at an experimental site in Palsgård, Denmark. The markers were injected as a solution through plastic tubes around 20 trees of each species at either 5 or 50cm soil depth in June 2003. After 65days foliage and buds were harvested and the concentrations of 15N and Cs analysed. The recovery of 15N in the foliage and buds tended to be higher from 5 than 50cm soil depth in oak whereas they where similar in spruce and beech after compensation for differences in immobilization of 15N in the soil. In oak more Cs was recovered from 5 than from 50cm soil depth whereas in beech and spruce no difference could be detected. Out of the three investigated tree species, oak was found to have the lowest capacity to take up Cs at 50cm soil depth compared to 5cm soil depth also after compensating for differences in discrimination against Cs by the roots. The uptake capacity from 50cm soil depth compared with 5cm was higher than expected from the root distribution except for K in oak, which can probably be explained by a considerable overlap of the uptake zones around the roots and mycorrhizal hyphae in the topsoil. The study also shows that fine roots at different soil depths with different physiological properties can influence the nutrient uptake of trees. Estimates of fine root distribution alone may thus not reflect the nutrient uptake capacity of trees with sufficient accuracy. Our study shows that deep-rooted trees such as oak may have lower nutrient uptake capacity at deeper soil layers than more shallow-rooted trees such as spruce, as we found no evidence that deep-rooted trees obtained proportionally more nutrients from deeper soil layers. This has implications for models of nutrient cycling in forest ecosystems that use the distribution of roots as the sole criterion for predicting uptake of nutrients from different soil depths