Vegetation dispersal
Most plants have the capacity to disperse throughout the landscape either as vegetative propagules or as seeds. This movement is an important factor for both the replenishment of propagule banks and promoting diverse aquatic plant communities.
There is limited information on the dispersal mechanisms for individual plant species (i.e. physical characteristics, buoyancy) which can influence where they will be deposited, and how flow regimes and hydrological connectivity (e.g. physical barriers) can impede dispersal of these plant propagules. These factors can significantly impact the distribution of aquatic and riparian plants.
Background
The movement of propagules within the landscape is an important factor in both the replenishment of dormant propagule banks and in the diversity of extant aquatic communities (Morris 2012; Nilsson et al. 2010). Changes in flow regimes, or hydrological connectivity, are therefore likely to significantly impact the distribution of aquatic and riparian plants (Merritt, Nilsson & Jansson 2010). Changed connectivity may occur through the disconnection of components of the landscape caused by changes in flow regime, construction of barriers that physically impede dispersal, and the physical removal of riparian plants.
Research globally has indicated that provision of pathways for the dispersal of seeds and propagules is important in the restoration and rehabilitation of wetlands (Bischoff, Warthemann & Klotz 2009), but there is limited information on the dispersal of seeds and propagules by water in Australian landscapes (Capon et al. 2009; Groves et al. 2009).
Long-term monitoring programs throughout the southern connected basin have identified more than 700 floodplain and wetland plant species. Most plants have the capacity to disperse either as vegetative propagules or as seeds. However, there is limited information on dispersal mechanisms for individual plants and their capacity to disperse throughout the landscape. The physical characteristics of seeds will determine whether they float or sink, which is likely to influence where they are likely to be deposited.
Throughout the Murray–Darling Basin, management agencies are watering wetlands via artificial connection pathways (i.e. pumps), which may favour the dispersal of some groups of plants over others (Jansson et al. 2000). Understanding the way in which managed flow regimes and infrastructure alter or facilitate the movement of aquatic and riparian plant species will be key to managing for dispersal.
By understanding how and when individual plant species or groups of species move throughout the landscape, and which species are likely to or predominantly move by water, managers will be able to better target species of interest, and better understand the likely outcomes of a particular watering event.
Objectives
The objectives of this research theme are to:
- determine the physical characteristics of seeds that facilitate dispersal (e.g. Buoyancy)
- understand the spatial and temporal movement patterns of wetland and riparian vegetation.
Intermediate objectives
- determine the physical characteristics of seeds that facilitate dispersal
- the physical characteristics of seeds will determine the distance that they drift in the water column and whether they drift on the surface or lower in the water column. Knowledge of seed morphology will enable predictions on which seeds are likely to persist in the drift and how infrastructure will influence drift
- understand the spatial and temporal movement patterns of wetland and riparian vegetation
- this component seeks to understand how the delivery of water through infrastructure modifies the movement of propagules between different components of the riverine-floodplain landscape.
Management implications
Protect and restore water-dependent ecosystems
The maintenance of lateral connectivity is recognised as being important in the protection and restoration of aquatic ecosystems. The MMCP Collaboration aims to provide managers with the tools to make informed decisions on how the operation of infrastructure (pumps/regulators) to restore lateral connectivity between rivers and wetlands will lead to changes in vegetation community by either selecting for or against seeds with specific traits.
Ensure that water-dependent ecosystems are resilient to climate change and other risks and threats
The MMCP Collaboration will provide water resource managers with the knowledge on how best to manipulate water regimes to maintain ecosystem function (including native seed dispersal), and protect water-dependent ecosystems as the demand for water resources increases under climate change scenarios.