Wetland vegetation monitoring, 2000/2001 (Salinity Action Plan)

This report represents the vegetation component of a project designed to provide ongoing monitoring of wetland salinity and biological resources in wetlands of the agricultural zone of south-west Western Australia. Maintenance of wetland biological diversity in the agricultural zone is one of the major objectives of the Salinity Action Plan. Due to their low position in the landscape, wetlands are the habitat most affected by salinisation

Salinity Action Plan : wetland vegetation monitoring, 1997/1998

This report represents the vegetation component of a project designed to provide on-going monitoring of wetland salinity and biological resources in wetlands of the agricultural zone of south-west Western Australia. Maintenance of wetland biological diversity in the agricultural zone is one of the major objectives of the Salinity Action Plan. Due to their low position in the landscape, wetlands are the habitat most affected by salinisation..

Wetland vegetation monitoring, 1998 survey: Gnangara wetlands

Water regimes, both groundwater and surface water components dil\u27ectly effect distribution, health and species composition of wetland fringing vegetation. In the area of the northern Swan Coastal Plain overlying the Gnangara groundwater mound, wetland water levels and therefore the vegetation can be intimately connected to underlying groundwater levels. The Water Corporation (formerly Water Authority of Western Australia) has been drawing water from the Gnangara mound for domestic water supply for a number of years. The main objective of this study is to monitor the changes in the vegetation fringing these wetlands and to determine if this is related to changes in groundwater or other factors affecting the lakes. Wetlands of specific interest in 1998, because of breached guidelines for groundwater drawdown through abstraction, have been summarized in detail in this report. These wetlands include Lakes Joondalup, Jandabup, Mariginup and Nowergup. Raw data from the 1998 survey for the other wetlands monitored in 1997, as well as the wetlands mentioned above, are presented in Appendix 1..

Salinity Action Plan : wetland vegetation monitoring, 1998/1999

This report represents the vegetation component of a project designed to provide on-going monitoring of wetland salinity and biological resources in wetlands of the agricultural zone of south-west Western Australia. Maintenance of wetland biological diversity in the agricultural zone is one of the major objectives of the Salinity Action Plan. Due to their low position in the landscape, wetlands are the habitat most affected by salinisation..

Wetland vegetation monitoring, 1999/2000 (Salinity Action Plan)

This report represents the vegetation component of a project designed to provide on-going monitoring of wetland salinity and biological resources in wetlands of the agricultural zone of south-west Western Australia. Maintenance of wetland biological diversity in the agricultural zone is one of the major objectives of the Salinity Action Plan. Due to their low position in the landscape, wetlands are the habitat most affected by salinisation

Long-term changes in vigour and distribution of Banksia and Melaleuca overstorey species on the Swan Coastal Plain

Long-term changes in vigour and distribution of the dominant Banksia (5 species) and Melaleuca (1 species) overstorey species were examined within four vegetation transects overlying the Gnangara Groundwater Mound, a superficial unconfined shallow aquifer on the northern Swan Coastal Plain, Western Australia. All transects were positioned along topographical gradients and monitored over a 20-30 year period. The two co-dominant overstorey species (Banksia attenuata and B. menziesii) inhabited a range of topographical positions within the landscape, from dune crest to low lying areas, with only B. attenuata increasing its distribution (moving further downslope) within the transects over time. Both species displayed a reduction in vigour, as indicated by foliage condition, during the monitored period. Species commonly inhabiting low-lying winter-wet areas (e.g. Banksia littoralis, Melaleuca preissiana) showed the greatest loss of tree vigour in response to declining groundwater levels, with B. littoralis replaced by the more drought tolerant B. prionotes. M. preissiana populations were overall more resilient to altered groundwater regimes, responding over a much greater time period (many decades) than B. littoralis (<10 years). Overall, changes in species distribution and vigour were primarily caused by long-term declines in groundwater levels resulting from the cumulative effects of abstraction and below average annual rainfall (low groundwater recharge). Long-term distribution trends and overall observed reductions in population vigour within the transects may be a function of the species’ dependency on groundwater to fulfil its water requirements. This may explain declining vigour and tree numbers of B. ilicifolia on the Gnangara Groundwater Mound, as this species is considered an important indicator of significant long- and short-term reductions in groundwater levels

Myrtaceous shrub species respond to long-term decreasing groundwater levels on the Gnangara Groundwater Mound, northern Swan Coastal Plain

Analysis of four vegetation transects that were established on the Bassendean Dune System, northern Swan Coastal Plain classified 42 native plant species into four ‘habitat’ groups based on their preferred soil moisture regimes (Havel 1968). Using adult abundance and distribution data from three of these transects and an additional transect established in 1976, we investigated the various ecological responses of myrtaceous shrub species representing the four habitat groups to long-term (20-30 yr) decreasing groundwater and soil moisture levels. Myrtaceous shrubs were chosen for analysis because of their widespread occurrence and diversity on the Swan Coastal Plain, and because Myrtaceae is the only plant family to be represented in all four of Havel’s habitat categories. Myrtaceous species ‘tolerant of excessive wetness’ (Astartea fascicularis, Hypocalymma angustifolium, Pericalymma ellipticum, Regelia ciliata) are all shallow rooted (rooting depth < 1m), occur in winter-wet depressions, and displayed the greatest reduction in population size in response to decreasing groundwater levels. Species cateogorised as displaying ‘maximum development on dry sites’ (Eremaea pauciflora, Melaleuca scabra, Scholtzia involucrata) commonly occurred on the upper and mid-slopes of the transects, are deeper-rooted and varied in their population response to long-term declines in water availability. All three species probably rely to some extent on accessing soil moisture at depth (2-6 m) during summer drought. The scenario was similar for species ‘optimum on moist sites’ (M. seriata) and for species ‘without clear-cut site preferences’ (Calytrix flavescens). In the context of Havel’s four habitat categories, whether a particular habitat preference is ‘wet’ or ‘dry’ refers to availability of soil moisture, although to what soil depth and moisture levels are uncertain. Habitat preferences, based on soil moisture availability, may have no relevance to a species preferred groundwater regime and hence response to decreasing groundwater levels. A species’ groundwater requirements during periods of drought are dependent on their position in the landscape, summer groundwater depth and the species rooting depth

Disentangling the complexity of groundwater dependent social-ecological systems

Groundwater resources are part of larger social-ecological systems. In this chapter, we review the various dimensions of these complex systems in order to uncover the diversity of elements at stake in the evolution of an aquifer and the loci for possible actions to control its dynamics. Two case studies illustrate how the state of an aquifer is embedded in a web of biophysical and sociopolitical processes. We propose here a holistic view through an IGM-scape that describes the various possible pathways of evolution for a groundwater related social-ecological system. Then we describe the elements of this IGM-scape starting with physical entities and processes, including relations with surface water and quality issues. Interactions with society bring an additional layer of considerations, including decisions on groundwater abstraction, land use changes and even energy related choices. Finally we point out the policy levers for groundwater management and their possible consequences for an aquifer, taking into account the complexity of pathways opened by these levers

Passive clearing of native vegetation: Livestock damage to remnant jarrah (Eucalyptus marginata) woodlands in Western Australia

In south-western Australia, areas of native forest and woodland on farmland left after agricultural clearing (remnants) have in recent times been subject to chronic disturbance by grazing livestock. We analysed adjacent grazed and ungrazed sites to assess the effects of grazing disturbance on the scleropyhll woodland community. Species richness and diversity were reduced in heavily-grazed sites and floristic dissimilarity between grazed and ungrazed sites was high. In the heavily-grazed sites, exotic species were 46% to 48% of the species recorded. Frequency and cover of native perennial species was significantly reduced in the heavily-grazed sites and in a lightly-grazed site. There was a significant increase in the frequency and cover of exotic annual grasses and herbs in the heavily grazed sites. Other life form groups such as geophytes, native perennial grasses and native annuals were not significantly affected by livestock grazing. Grazing also resulted in a significant increase in surface soil compaction and water repellency as well as concentration of soil N and P. Size-class distribution of the overstorey indicated that no recruitment had taken place for many years and, although germination of overstorey species occurred each year, no seedlings survived at the heavily grazed sites. In these sclerophyll woodlands, grazing has altered plant community structure, from a understorey dominated by perennial shrubs to one dominated by exotic annual grasses and forbs. Resilience of native perennial species is dependent on reproductive strategy, life form and morphology, life history and palatiblity. Annual exotic species are favoured by increases in soil nutrients and disturbance, reduction in competition and an ability to withstand a high level of disturbance