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Flood plains are an important component of the riverine landscape providing a range of ecosystem goods and services. In dryland environments, flood plains are a refuge for a wide variety of plant and animal species. Flood plain features often appear to display relatively coarse gradients of structure with distance from the main river channel in res...
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Context 1
... Under "average" climatic conditions only 24% of rainfall is converted to runoff from the catchment area above Wagga Wagga, while downstream the rainfall runoff coefficient is less than 2% ( Khan et al. 2004). Annual discharges range from 251 000 ML to 6 610 000 ML, for 1937-2005 at Maude Weir, located in the lower reaches of the catchment (Fig. 2). 1937 1939 1941 1943 1945 1947 1949 1951 1953 1955 1957 1959 1961 1963 1965 1967 1969 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 Year Discharge (ML year The Murrumbidgee River is a highly regulated system with 14 large dams and eight low level weirs on its main channel or tributary ...
Citations
... Factors responsible for the loss and degradation of wetlands include diversions and damming of river flows causing disconnection of floodplain wetlands, cattle grazing and trampling, eutrophication, and the practices of filing, dyking and draining (Brinson and Malvárez 2002;Finlayson et al. 2005;Zedler and Kercher 2005;Dudgeon et al. 2006). Water resource development, i.e. river regulation and extraction of water for irrigation and other purposes, and other agricultural activities are two of the major drivers of wetland degradation and loss with changes to the frequency, extent and duration of flooding and drying common outcomes from these activities (Armstrong et al. 2009;Shilpakar and Thoms 2009;Leblanc et al. 2012). Alterations to the natural flooding regime have been observed to change wetland plant community composition and the ability of aquatic plants to recover following rewetting (Brock et al. 2003;Nielsen et al. 2013;Wassens et al. 2017). ...
The occurrence and distribution of aquatic macrophytes within a wetland depends on the hydrological requirements of each species and the hydrological conditions. The aims of this study were to: (1) determine relationships between germination of Eleocharis acuta and Eleocharis sphacelata and hydrological regime, (2) determine the buoyancy of the seeds of E. acuta and E. sphacelata and hence their ability to disperse by hydrochory and (3) determine whether E. acuta and E. sphacelata exhibit dormancy. The seeds of E. acuta and E. sphacelata both germinated best on soil-soaked and when inundated for 80 days (to a depth of 5 cm). No seeds of either species germinated under rainfall conditions. Viability testing following the experiment showed that some seeds of both species remained ungerminated and viable following soaking, inundation and rainfall conditions for 90 days, demonstrating that E. acuta and E. sphacelata exhibit dormancy. At least 50% of E. acuta seeds floated for 32 days, while 50% of E. sphacelata seeds remained floating for at least 39 days. These germination and dispersal characteristics define where and when these Eleocharis species establish related to temporal and spatial hydrological variability.
... Yanga National Park (YNP), located in the lower reaches of the Murrumbidgee River in South East Australia (Fig. 1), comprises relatively well-preserved areas of floodplain vegetation and wetlands (Shilpakar and Thoms 2009). The YNP extends between 34°20 0 and 34°51 0 S and 143°30 0 -143°55 0 E covering an area of about 750 km 2 . ...
... Variability in the natural wetting and drying regime of the Yanga floodplain supports a complex mosaic of 13 vegetation communities (Shilpakar and Thoms 2009). The most extensive are river red gum (Eucalyptus camaldulensis) forests and woodlands, which cover more than 20,000 ha the Yanga floodplain. ...
ContextFloodplains are complex adaptive ecosystems that provide an array of ecosystem services. Despite the growing focus on resilience as a fundamental feature of floodplain ecosystems, and as an aim in floodplain management, few studies have quantified the resilience of floodplain landscapes over meaningful timescales.Objectives
This study examines the resilience of floodplain vegetation communities over medium (decadal) and long term (multi-decadal) times scales through an analysis of the spatial organisation of different vegetation communities. The floodplain vegetation landscape is conceived as having two basins of attraction represented by; (1). Natural vegetation, which incorporates two domains of flood dependent (FD) and non-flood dependent (NFD) vegetation communities; and, (2). Cleared vegetation (CL).Methods
We examine change in the spatial organisation of vegetation communities on the Yanga floodplain, located on the Murrumbidgee River, Australia, over a forty-year period (1965–2005). Detailed vegetation community maps, constructed from orthorectified aerial photographs for the years 1965, 1973, 1997 and 2005, were used.ResultsSubstantial changes in the extent and spatial configuration of vegetation communities occurred over the 40-year period. Many changes were bidirectional transitions between FD and NFD vegetation communities, representing transitions in response to variations in flood frequency. However, the predominant unidirectional transition of the FD and NFD vegetation communities were to CL.Conclusions
The dynamic character of the Yanga Floodplain vegetation landscape is shown by 91 detectable transitions among vegetation community types. Despite large areas of the floodplain vegetation landscape having undergone persistent community change, some areas of the floodplain display resilience over the 40-year period. This suggests floodplain vegetation communities are well adapted to substantial changes in environmental conditions as a result of episodic flooding and drying. However, large net changes and an increase in CL, which did not revert back to previous vegetation community types, suggest a transition to a different basin of attraction, and a loss of system resilience.
... Worldwide, the patterns of flow in rivers have been, and continues to be, affected by water resource development (Grill et al., 2015;Haddeland et al., 2014;Nilsson, Reidy, Dynesius, & Revenga, 2005). These changes disrupt the natural flood regime of rivers and their floodplains (Ward & Stanford, 1995), changing the frequency, extent, and duration of floodplain inundation (Kingsford, 2000b;Shilpakar & Thoms, 2009). Water resource development has led to a decline in the ecological condition of floodplains globally, with floodplain vegetation communities changing in structure and composition as a result (e.g., Bunn & Arthington, 2002;Stevens, Schmidt, Ayers, & Brown, 1995). ...
Floodplains and their associated wetlands are important features of semiarid and arid landscapes, providing habitat and refugia for native species as well as contributing to human needs for freshwater. Globally, floodplain habitats are some of the most modified ecological communities because of water resource development and land‐use changes. However, the hydrological changes that have occurred in highly variable semiarid and arid systems are rarely quantified in a way that helps us understand the consequences for different floodplain habitat types. This study investigated changes in floodplain‐river connectivity that have occurred because of water resource development on four floodplain habitat types in the Lachlan River Catchment, Australia: (a) temporary floodplain lakes, (b) intermittent river red gum (Eucalyptus camaldulensis) swamps, (c) intermittent black box (Eucalyptus largiflorens) swamps, and (d) terminal wetlands (wetlands along distributary creeks). Changes to floodplain‐river connectivity characteristics were calculated using their commence to fill thresholds and flow scenarios derived from a river hydrology model, enabling comparison of long‐term data sets (120 years) encompassing a range of climate conditions. Connection regime metrics have changed significantly in all floodplain habitats except intermittent black box swamps. Temporary floodplain lakes have experienced the greatest reduction in number of connection events (60% reduction), followed by intermittent river red gum swamps (55% reduction). Intermittent black box swamps and terminal wetlands have experienced the least change in number of connection events (35% reduction). The nature of the change in connection suggests a change in vegetation communities will occur in response to long‐term hydrological change.
... Water resource development disrupts the natural flood regime of rivers and associated flood plains (Ward and Stanford 1995), changes the lateral connectivity of flood plain-river systems (Thoms 2003) and reduces the frequency, extent and duration of flood plain inundation (Kingsford 2000;Shilpakar and Thoms 2009). Flow peaks, and consequently durations of inundation, have been reduced in most rivers across the Murray-Darling Basin by river regulation and extraction of water for irrigation and other purposes (Driver et al. 2004a;Armstrong et al. 2009;Leblanc et al. 2012). ...
... Water resource development has changed the hydrological regimes of flood plain ecosystems in the Murray-Darling Basin (Kingsford 2000;Driver et al. 2004a). Changes in flood regimes can cause plant species and vegetation communities to contract or expand on flood plains according to their inundation requirements (Shilpakar and Thoms 2009;Thomas et al. 2012;Roberts et al. 2016). ...
The distribution of plants on flood plains depends on the hydrological regime on the flood plain and the hydrological requirements of the plants. The aims of the present study were to: (1) determine the relationships between germination of tangled lignum (Duma florulenta) and nitre goosefoot (Chenopodium nitrariaceum) and hydrological regime; (2) determine the buoyancy of the seeds of the two species, and hence the ability of the seeds to disperse by water; and (3) inform environmental flow requirements for the two species. Seeds of tangled lignum germinated best on soaked soil and on soil inundated for 20 days. Seeds of nitre goosefoot germinated best on soil inundated for 5 days and on soaked soil. The majority of tangled lignum seeds floated for at least 7 days. The majority of nitre goosefoot seeds sank within 7 days. The results of the present study are consistent with the observed distributions of the species on flood plains. Tangled lignum requires ∼20 days of flooding and wet soils following flood recession for optimal germination. Nitre goosefoot requires a few days of flooding and wet soils following flood recession for optimal germination. The inundation requirements for germination of tangled lignum and nitre goosefoot should be considered in the management of environmental flows.
