© 1997 Heron Publishing—Victoria, Canada
Responses of Picea, Pinus and Pseudotsuga roots to heterogeneous nutrient distribution in soil
Eckhard George (1), Bettina Seith (1), Christoph Schaeffer (2) and Horst Marschner (1)
1. Institute of Plant Nutrition, Hohenheim University, 70593 Stuttgart, Germany / 2. Physiological Ecology of Plants, Botanical Institute, University of Tübingen, 72076 Tübingen, Germany / Received November 27, 1995
Summary
The spatial distribution of plant-available mineral nutrients in forest soils is often highly heterogeneous. To test the hypothesis
that local nutrient enrichment of soil leads to increased root proliferation in the nutrient-rich soil zone, we studied the
effects of nutrient enrichment on the growth and nutrient concentrations of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) roots. Three-year-old seedlings were grown for 9 months in split-root containers filled with nutrient-poor forest
mineral soil, with one side supplemented with additional mineral nutrients. Root dry weight and root length in Scots pine
and Norway spruce were increased in the nutrient-supplemented soil compared with the nonsupplemented side, whereas root growth
in Douglas-fir was unaffected by nutrient enrichment. Of the three species examined, Norway spruce exhibited the highest root
and shoot growth and the highest nutrient demand. Specific root length (m g–1) and the number of root tips per unit root length were not affected by local nutrient addition in any of the species. Despite
increased root growth in Norway spruce and Scots pine in nutrient-supplemented soil, their root systems contained similar
nutrient concentrations on both sides of the split-root container. Thus, coniferous trees may respond to local nutrient supply
by increased root proliferation, but the response varies depending on the species, and may only occur when trees are nutrient
deficient. As a response to local nutrient enrichment, increases in root dry matter or root length may be better indicators
of pre-existing nutrient deficiencies in conifers than increases in root nutrient concentrations.
Keywords:
Douglas-fir, local nutrient supply, Norway spruce, nutrient concentrations, root growth, root morphology, Scots pine.
