More on nursing mixtures.

  • M.L. Carey Forest Service, Sidmonton Place, Bray, Co. Wicklow, Ireland.
  • R.G. McCarthy Forest Service, Sidmonton Place, Bray, Co. Wicklow, Ireland.
  • H.G. Miller Forestry Department, University of Aberdeen, Scotland.
Keywords: Nursing mixtures, nitrogen turnover, mycorrhizal fungal flora, silviculture, Sitka spruce, Japanese larch, Larix kaempferi, Picea sitchensis, soil nutrients, thinning.


A series of experiments in Ireland and Britain has demonstrated that the growth of Sitka spruce (Picea sitchensis (Bong.) Carr) can be enhanced on poor soils by the presence of Japanese larch (Larix leptolepis Sieb.), Scots pine (Pinus sylvestris L.) and lodgepole pine (Pinus contorta). The improved growth, or so called "nurse effect", is related to greater availability of soil nitrogen and a more rapid turnover of nitrogen in mixtures compared with spruce monocultures. It becomes noticeable some 8-10 years after planting. Research results suggest that the effect is closely related to the root activity of the nurse species and substantial differences have been found in the mycorrhizal fungal flora on pure spruce compared with spruce grown in mixture with larch or pine. Mixtures are now advocated for site types such as oligotrophic peats and podsolised mineral soils where nitrogen deficiency is often a problem. Although they may be more difficult to manage than monocultures, their use is likely to greatly reduce the need for top dressing with fertiliser nitrogen and at the same time add diversity to species selection. Self-thinning mixtures of spruce and a slow growing provenance of lodgepole pine or Scots pine are suggested as an option for high production wet mineral soils where windblow is often associated with conventional thinning.
How to Cite
Carey, M., McCarthy, R., & Miller, H. (1988). More on nursing mixtures. Irish Forestry. Retrieved from