The importance of the coarse soil fraction in acid forest soils for tree nutrition

Summary:

Recent findings show that the coarse soil fraction (> 2mm) in forest ecosystems is far more important for nutrient-cycling than was formerly suspected. Research in the Southern Black Forest (Germany) showed that soils formed in crystalline rocks have a high potential of short to middle term available nutrients in the coarse soil fraction (HEISNER et al. 2004).

The link between the pool of available nutrients in stones and the nutrient cycle of trees are probably nutrient adsorbing fungal mats, as is shown by the plentiful abundance of fungal hypha and scleroties found in sceletonparticles of acid forest soils. Results from microscopic research support the hypothesis of a specific nutrient uptake by fungal microflora through the opening of micro-compartments of stones and ascertaining the longterm use of this nutrient pool.

We would like to obtain the first direct prove that with the help of mycorrhiza trees have direct entrance to nutrient pools of the coarse soil fraction, which samples in space/time of the colonization of hypha of the coarse soil will unravel. We propose two approaches:

1) In minicosms with controlled nutrient in- and outputs Picea abies seedlings inoculated with mycorrhiza will be grown on coarse soil without K and/or Mg addition other than from the coarse soil. This approach will prove whether the coarse soil fraction can contribute to forest nutrition.

2) Coarse soil with a high nutrient potential will be deposited in acid forest soils with extreme low basesaturation in hypha-permeable meshbags and the colonization of fungal hypha will be obtained through micropedologic and biologic methods already developed in an earlier project.

The proposed research project will revise the present view of chemical forest soil science that is entirely based upon the fine earth fraction.

Duration: 31.12.2005 - 31.12.2008