Fertilization experiments in Douglas fir plantations on sites degraded by former litter gathering in the upper palatinate | Düngungsversuche zum Anbau von Douglasien auf durch frühere Streunutzung degradierten Standorten in der Oberpfalz
1997
Rehfuess, K.E.
On dystric cambisols derived from granite and phyllite and on a dystric gleysol (stagnosol) derived from deeply weathered cretacious sediments in the Upper Palatinate, which were all heavily degraded by former litter gathering, 3 fertilization experiments were established with Douglas fir planted after clearcut of the previous poor pine stands. The aim of the trials was to find out whether the nutrient déficiences to be expected on these adverse sites can be overcome by dressings of commercial fertilizers and whether vigorously growing stands of Douglas fir can be established by this procedure in spite of the unfavorable subcontinental climatic conditions.On all 3 sites the young Douglas fir trees without any cover crop suffered from heavy attack of beetles, Phomopsis peudotsugae, frost desiccation, needle cast caused by frost shocks or fungi infestation and were in addition damaged by hailstorms, leading to considerable plant losses. All plantations initially exhibited symptoms of severe magnesium deficiency, but Mg nutrition gradually improved even on the control plots with the increase in age and the development of the root systems. Application of Mg as part of the N fertilizers or as Mg-sulfate had only little influence. The extreme N deficiency of Douglas firs on all sites was removed by fertilization with N only temporarily in the year of application, but this effect did not last for a longer period. The supply with potassium, phosphorus and trace elements was adequate.From these results the following recommendations for the conversion of poor pine stands into well-growing mixed stands involving Douglas fir are derived: Liming with ground dolomite 5–20 years in advance of the introduction of Douglas fir under the close canopy of pine, combined with the early establishment of shade-tolerant deciduous species; thinning and subsequent planting of Douglas fir under a loose shelter of old pine trees.
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