Dulamsuren, Choimaa , Hauck, Markus , Muehlenberg, Michael .
Insect and small mammal herbivores limit tree growth in northern Mongolian steppe.
NATURAL versus anthropogenic causes of the inhibition of tree growth on meadow steppes occurring on sunlit southern slopes as treeless outposts within the northern Mongolian mountain taiga were investigated in a case study carried out in the western Khentey Mountains. Sowing and planting experiments with Mongolia's most common tree species, Larix sibirica, did not result in the successful establishment of any tree during one vegetation period. Only 0.1 % of the seeds germinated four weeks after sowing in spring. All seedlings died within further three weeks due to drought and heat. About 40 % of seeds in open meadow steppe and 65 % in meadow steppe along the forest edge were not retrieved in the soil three months after sowing suggesting that granivory significantly reduces the seed reservoir. Two-year old seedlings of L. sibirica suffered from drought as well as from feeding by larvae of gypsy moth (Lymantria dispar) and by grasshoppers and rodents. At the end of the vegetation period two thirds of the seedlings died due to insect and small mammal herbivory and one third due to drought-related damage. Herbivores attacked larch seedlings more rapidly on the open meadow steppe than at the forest edge. Larvae of gypsy moth preferably fed seedlings, which were irrigated every second day, whereas no preference for irrigated or non-irrigated trees was observed with grasshoppers and rodents. The results suggest that drought and high temperature at the soil-air interface combined with high grazing pressure by insects and small mammals are crucial for inhibiting tree encroachment on the steppe slopes of the western Khentey Mountains. Other factors, like grazing by large herbivores (which were excluded from the sample plots by fencing), wildfires or logging might also be effective at inhibiting the establishment of trees, but are not essential to explain the lack of forest.
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Website on the project and Ch. Dulamsuren's publications
1 - University of Goettingen, Center of Nature Conservation, Von-Siebold-Strasse 1, Goettingen, 37075, Germany
2 - University of Goettingen, Albrecht von Haller Institute of Plant Sciences, Untere Karspuele 2, Goettingen, 37073, Germany
Presentation Type: Poster:Posters for Sections
Location: Auditorium/Bell Memorial Union
Date: Tuesday, August 1st, 2006
Time: 12:30 PM