STAND MANAGEMENT COOPERATIVE
Articles of Interest
German Soil and Forest Nutrition Scientist Visiting the CFR to Conduct
Research on SMC Installations
From February to August 1999, Dr. Joerg Prietzel, Assistant Professor at the Faculty of Forestry of the University of Munich (Germany), is working at the College of Forestry of the University of Washington as a Visiting Scholar to conduct research at selected SMC installations.
In 1990, Dr. Prietzel received his M.Sc. degree in hydrology and soil
science at the University of Freiburg (Germany), having worked on the
effects of MgSO4 and ammonium sulfate fertilization on aluminum cycling
in Black Forest Norway spruce ecosystems on acid soils. 
Since
then, he has been working on the effects of anthropogenic sulfur emissions
on soil chemistry, nutrient cycling, and forest nutrition of various European
and North American sites. Submitting a thesis dealing with that research,
he received his Ph.D. in Forest Sciences in 1993 from the University of
Munich. Another key issue of his research is studying the effects of liming
and N fertilization on soil chemistry, tree nutrition, and forest growth
in degraded German Scotts pine ecosystems.
Since 1994, Dr. Prietzel has held a tenure position as Assistant Professor for Soil Science and Forest Nutrition at the Faculty of Forestry of the University of Munich.
During his half-year stay at the UW, Dr. Prietzel has been collaborating with Rob Harrison on a research project dealing with a key issue of the SMC-funded “carryover-effect” project. Together with the CFR graduate student Gage Wagoner he is carrying out N mineralization studies on 6 former RFNRP installations located all around the Puget Sound. Each site is forested with Douglas-fir. Each consists of a control plot and an adjacent plot that had been repeatedly fertilized with urea (in total 800 to 1000 lb/ac N) 15 to 30 years ago. The primary aim of Dr. Prietzel’s research is to investigate, whether the improved growth of second generation Douglas fir seedlings that has been observed on the fertilized plots, is due to an improved supply with nitrogen liberated by humus mineralization.
In spite of the fact that the applied urea-N has been consumed by plants or soil microorganisms long ago, most (but not all) of the fertilized plots exhibit an improved N status of the soil: The C/N ratio of the forest floor is narrower than that of the respective control plots, and, much more important, the N mineralization rates are far higher. This general pattern holds true for 4 out of the 6 studied sites; for the two remaining sites, there is substantial evidence that the control plots showed a better a priori N status than the respective fertilized plots. More details on the results of these studies will be given in the SMC Newsletter.