When does your grassland get so dry that it doesn’t matter whether it’s raining or not?
We can’t say it’s completely dry, but it’s not so hot that it’s totally dry either.
That’s the main takeaway from a recent study from the University of Georgia that looked at how much grasslands in Australia’s south-west dry up during dry spells.
“We have seen some really, really dry periods in our northern parts, but we don’t know how much of that is because it’s really hard to track them,” study lead author, Andrew Waugh, said.
“It is difficult to track how much vegetation is actually affected, especially because it changes dramatically over time.”
Waugh said the study was the first to look at whether it was even possible to track dryness in the Northern Territory and the Northern Rivers region, where the study’s authors looked at soil moisture and rainfall records.
“There’s a lot of variability in these regions, which is a huge concern for researchers, because these are the ones that are really heavily affected by drought,” he said.
Waugh is a doctoral student in geomorphology at the University’s School of Geosciences.
He is also a lead author on a paper published in the journal Nature Communications on the same subject.
“This study looked at what’s happening in this region, how it’s changing and how it relates to the rainfall patterns across the country,” Waugh said.
The study found that in some parts of the NT, grasslands can be dry enough to prevent rain, but in other parts it’s actually wet enough to keep rain from happening.
“So what happens is we have very high humidity in parts of Australia, so if the moisture is in the dry season, there’s a chance that the rainfall will be dry, and if it’s wet, there may be a chance of rain,” Waughe said.
In many cases, the research suggests, that dryness may not be a good thing.
Waughe and his co-author, Professor David Rieder, both from the Australian National University, used satellite imagery to identify areas of the north-west that had been hit hard by drought and dry conditions.
Woughe and Ried, along with a colleague, used the same satellite images to look for the effect of different types of vegetation on rainfall patterns.
Wattle and Rued identified a small region of dry grasslands called the North Cascades, which was drier than its surrounding area.
This region also had a lot more rain in the early months of the dry spell, and there were fewer snowfalls.
But that area of dryland was also wetter than other parts of it.
The researchers also found that if they could measure the moisture in that area, it would be drier and less wet.
Wough and Waugh then looked at the same data, but they looked at different types and types of plants.
“What we found is that in a lot the areas that were wetter were more diverse in terms of the type of vegetation that was there, which suggests that the rain could get through there,” Woughe said.
“In some places, the vegetation was so diverse that you couldn’t even tell that there was a drier or wetter area because the vegetation is just so diverse,” he added.
Waunhe and Wied found that, in a few cases, some areas of dry land actually dry up.
In other cases, dry vegetation was more diverse than the other vegetation in a particular area.
“These were some areas that just had a very dry vegetation, and those were the areas where you’d have to use a lot less vegetation, because you’re going to be really limited,” Waunhe said, adding that the study suggested that some of the areas in the NT might actually dry out.
Waghe said the idea of dryness being a bad thing in Australia was not new.
“You know, it’s been around for a long time,” he explained.
“When the Great Depression hit in the 1930s, it was a really dry period for many of the Western Australian states, and in particular for the Western Rivers region in particular.”
But there were some good examples of rain in Australia during the dry spells of the 19th and 20th centuries.
“I think the most important thing is that we do know that we can track what’s going on in the soil,” he continued.
“That’s something that is really exciting and important.”
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