Woody plants in dry sands : life history traits and population dynamics

Abstract

Inland dune ecosystems are harsh environment for long-lived woody plants because of poor water and nutrient availability and frequent sand. As a result, long-lived woody plants have a high risk of being killed by sand movement or a long period of drought and this may occur even before they reach reproductive size. As dunes become more fixed, the increased coverage of annual plants with shallow root systems and the formation of microbiotic crusts reduces water percolation to deeper soil. Woody plants which typically possess deep rooting systems may then suffer from water shortage. Finally, growth of woody plants may be strongly impeded by herbivores (browsers) which can remove a large share of a plant’s seasonal growth in these habitats. Thus, long-lived woody species can only maintain populations in such a dune environment if they possess particular life history strategies that enable to overcome these stresses. In this thesis, I studied the demography of three dominant shrubs in Mu Us Sandland, in Inner Mongolia, China, to investigate how woody plants manage to colonize (semi-) mobile sand dunes, to maintain populations across different dune fixations stages and to cope with grazing activities of large herbivores. I analyzed the differences in life history traits and demographic adaptations of my study species and discuss these differences in relation to the ecology of woody plants in dune ecosystems in general. I also evaluate the advantage of using Integral Projection Models (IPMs), the type of models used in this thesis. Finally, I briefly discuss the implications of my findings for practical population management in inland dune ecosystems.