Vergleich unterschiedlicher Anbaumethoden von Energieholzplantagen

Abstract

At three study sites in Northwestern Germany different methods of planting and managing short rotation coppices on former arable land were tested.One study site (Gütersloh) was divided into former arable land, which was ploughed and harrowed before planting, and into former grassland, at which the planting rows were treated with herbicides and ploughed. In spring 2007 cuttings of poplar hybrids Max 4 (P. nigra x P. maximowiczii), NE 42 (P. maximowiczii x P. trichocarpa), cuttings of the willow Turbo (Salix viminalis) and two year old bare rooted plants of Populus tremula and Robinia pseudoacacia were planted at the former grassland. At the former arable land two to three year old bare rooted plants of Acer pseudoplatanus, Sorbus aucuparia, Alnus glutinosa and Tilia cordata were also planted. Three methods of vegetation management (control, mowing, competitive replacement) and four methods of applying soil additives (control, hydrogel, mycorrhizae, hydrogel/mycorrhizae) were tested.The second study site (Hamerstorf) was planted in 2006 with cuttings of the poplar hybrids Androscoggin (P. maximowiczii x P. trichocarpa), Max 4 (P. nigra x P. maximowiczii), NE 42 (P. maximowiczii x P. trichocarpa) and Weser 6 (P. trichocarpa). Before planting the former fallow ground was prepared in three different ways (ploughing/harrowing, ploughing, herbicides). The third study site (Unterlüß) had been managed as a wildlife food plot before planting the poplar cuttings Max 2 (P. nigra x P. maximowiczii), Max 3 (P. nigra x P. maximowiczii), NE 42 (P. maximowiczii x P. trichocarpa) and Weser 6 (P. trichocarpa) in 2008. One part of the poplar cuttings was treated with mycorrhizae before planting.In 2007 and 2008 the survival as well as the growth of the young trees was measured and the species composition as well as the biomass of the ground vegetation was assessed. Additionally the nutritional supply of the trees, the element outflow in the leakage water and the suction power was determined.The aim of this thesis was to make recommendations for the planting and management of a short rotation coppices based on the data determined. The results showed that no management of vegetation is necessary when the biomass production of the ground vegetation is low and the tree species were adapted. Especially willow had an almost 100 % survival rate. With the exception of Alnus glutinosa the rooted plants had also satisfying survival and growth rates. Mowing between the planting rows had a positive effect on survival and growth only in exceptional cases. Sowing buckwheat and clover as competitive species was not qualified as vegetation management. It reduced the biomass of the natural vegetation, but was itself a too high competition in nutrition and water. The biomass of ground vegetation was most influenced by the preparation of soil. Results clarified that only preparing the planting rows was not as effective as the preparation of the whole planting ground. The prepared planting rows became overgrown by the ground vegetation very fast, which reduced the survival of the trees, especially of the poplar cuttings. The more intensive the ground preparation was, the higher was the survival and growth of the young poplar. The chemical preparation with herbicides was not necessary for an adequate suppression of the weed. The negative effect of a mechanical preparation was a high nitrate leakage caused by the higher mineralisation. The mechanical treatment increased the nitrate leakage exponentially. Not treating the soil within the rotation cycle let the nitrate leakage sink under the legal limit so that it was constantly lower than the nitrate leakage of annually cultivated agricultural land.The soil additives hydrogel and mycorrhizae effected the survival and growth of specific trees. Especially on dry study sites hydrogel increased the survival and growth of trees in former studies. At the climatic more moderate study site hydrogel increased the vitality of specific tree species, but it had no effect at the survival and growth of the trees. The mycorrhization of the trees increased the nutritional supply and growth of some specific tree species.