They also change over time; for example; in response to disturbance (by clearing; fire; logging or grazing); or to the climate and weather (e.g. floods; drought and extreme heat or cold).

Also; environmental variables; such as climate (and the ecological community s response to them); fluctuate or change over time.

Climate change is a potential threat across the distribution of Poplar Box Grassy Woodland.

In addition to directly threatening species that cannot adapt; climate change can alter resource availability and the competitive relationships between species; plus can exacerbate existing threats such as habitat loss; fire; dieback and invasive species.

Climate change Climate change poses a serious long term threat to terrestrial and aquatic ecosystems with the potential to change ecology of these environments through changes to species composition and function (Dunlop et al. 2012).

DECCW (2010a 2010b) projected climate change effects to 2050 for the New England; North West and Western regions of NSW.

These predicted changes to climate are likely to impact upon the ecological community and result in issues such as loss of resilience to degradation and fragmentation structural and compositional changes of the herbaceous ground layer o changed C3 C4 ratios e.g. summer growing or C4 grasses; such as kangaroo grass; redgrass or the weed African lovegrass (Eragrostis curvula); are likely to replace the winter growing or year long green or C3 grasses; such as speargrasses and wallaby grasses in the ecological community’s southern extent o replacement of perennial grasses with annual species o reduced pasture production and increasing grazing pressure from livestock; eastern grey kangaroos and other macropods and exotic herbivores. predominance of exotic plant species and reduced native forb diversity altered fire frequency; increased intensity and spread high rainfall areas under increased pressure for cropping and cascading changes in ecological interactions.

Other threats; such as rural tree dieback and the potential impacts from climate change may also contribute to loss of integrity over time.

The cover of understorey shrubs may increase with distance from watercourses; in lower fire frequencies and lower soil fertility (Clarke and Knox 2002 Graham et al. 2014 Shelly pers comm. 2014).

Fire intensity; frequency; seasonality and patchiness in addition to grazing by domestic stock and pest animals; influence vegetation composition and structure as well as the success of weeds.

Criterion 4 Reduction in community integrity Substantial clearing; severe fragmentation; weed invasion; inappropriate fire and grazing; and associated changes to vegetation structure and loss of faunal components have substantially reduced the integrity of the ecological community.

The removal of standing and fallen hollow bearing trees for timber; altered fire regimes; and grazing of domestic livestock are likely to have long term effects on remaining tree health.

However; drought coupled with overgrazing and weeds has dramatically altered fuel loads and fire regimes.

Graham et al. 2015 notes that fire frequency varies greatly across the full extent of Poplar Box woodland.

Estimates of fire frequency range from almost annually in the higher rainfall areas of northern Queensland; down to 1 10; 1 25 and 1 50 years in the southern NSW extent of the woodland; particularly in semi arid regions.

Different fuel loads have been attributed to high rainfall and fire frequency with native perennial grass species producing higher fuel loads than annual species; and invasive species such as buffel grass producing very high fuel loads.

Fire frequency; seasonality; height and intensity of fires can affect species dominance in the ecological community.

Invasive grasses with high biomass; such as buffel grass and Rhodes grass (Chloris gayana) can cause changes in fire regimes through a positive feed back cycle known as the grass fire cycle.

Fire promoting grasses also have the potential to alter the nutrient cycle and carbon cycling processes within remnant grassy woodland ecosystems (Rossiter et al. 2003).

The frequency of very high or extreme fire risk days could also increase.

Over much of the region where the ecological community occurs; hasher fire weather; increased intensity of extreme rainfall events; and an increase in the proportion of time spent in drought under a high emission scenario is also projected (Ekstrom et al. 2015).

It is also likely to interact with other threats; such as changed fire regimes and weed invasion.

With the reduction in fire frequency related to excessive grazing pressures following European settlement in the 19th and mid 20th century; there has been a rapid increase in the density of unpalatable native shrubs (woody regrowth) within the range of the ecological community (Noble et al. 2007).

Shrub encroachment into the ecological community may be a response to naturally or artificially induced processes such as fluctuating hydrology; altered nutrients; loss of apex predators or altered fire regimes.

Conclusion Substantial clearing; severe fragmentation; weed invasion; inappropriate fire and grazing; pasture improvement and other threats causing changes to vegetation structure and loss of faunal components have severely reduced the integrity of the ecological community.

However; drought coupled with overgrazing and weeds has dramatically altered fuel loads and fire regimes.

In addition; impacts from drought and preferential grazing may impact on the understorey structure of grassy woodlands (Harrington 1991).

Factors implicated in the dieback of Eucalyptus populnea include Water stress; notably from drought and falling water tables; which can increase foliage nitrogen levels and increase salinity.

Over much of the region where the ecological community occurs; hasher fire weather; increased intensity of extreme rainfall events; and an increase in the proportion of time spent in drought under a high emission scenario is also projected (Ekstrom et al. 2015).