Broedvogels in de Holmers, over prille bosontwikkeling in een Drents beekdal
Drentse vogels , Volume 25 - Issue 1 p. 2- 11
. During the past 20 years large areas of river valley in Drenthe have been changed into nature reserves in order to save vulnerable meadow vegetations that flourished up to 70 years ago. In most cases vegetation was removed every year (hay), top soils were removed and more recendy small ditches have been filled up and large areas are year round grazed with cattie. In the Holmers the top soil was removed from 2002-2004 and after that no management took place. In 2010 the area was covered with a wide variation of vegetations, ranging from 6 m high dense alder stands to areas with only a vegetation of mosses (Fig. 1 and pictures). Mapping of breeding birds revealed a large variety of bird species (Table 1) Densities and variety of species was higher in a nearby part of the river valley that is mainly grazed by catde (Halkenbroek in Table 1) and much higher than respectively 10 and 20 years ago (Appendix 1). Diversity was mainly due to the large number of habitats that is currendy available.
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