Forest soil recovery following disturbance

Friday 28 Jun 2019

 
- Australian National University’s Elle Bowd led a research team that collected 729 soil cores from 81 sites in the mountain ash forests of southeast Australia. The sampling sites had been subjected to nine different types of disturbances, from wildfires to clearcutting and post-fire salvage logging, at different frequencies in the past.
- The team used the soil samples to look at 22 different soil measures, including key soil nutrients like nitrate, organic carbon, phosphorus, potassium, and sulfur, and how they’d been impacted by disturbances that occurred 8, 34, 78, and 167 years ago.
- Bowd said the team’s findings show that forest soils recover from disturbances slowly over many years — up to 80 years following a wildfire and as many as 30 years after logging, much longer than previously thought.


According to Elle Bowd, a researcher with Australian National University’s Fenner School of Environment and Society, there have been very few studies about the long-term impacts of disturbances like wildfires and logging on forest soils.

Based on what research has been done, we know that post-fire ash can inject large amounts of nutrients that plants need for growth, like phosphorus and nitrogen, into forest soils immediately after a fire. “But [we] know little about what happens 8 or 34 years after logging or 8 to 167 years after a bush fire to soils, despite their ongoing functional roles,” Bowd told Mongabay.

To fill this gap in our understanding of how long it takes forest soils to recover from disturbance, Bowd led a research team that collected 729 soil cores from 81 sites in the mountain ash forests of southeast Australia. The sampling sites had been subjected to nine different types of disturbances, from wildfires to clearcutting and post-fire salvage logging, at different frequencies in the past. The team used the soil samples to look at 22 different soil measures, including key soil nutrients like nitrate, organic carbon, phosphorus, potassium, and sulfur, and how they’d been impacted by disturbances that occurred 8, 34, 78, and 167 years ago.

By comparing the results to measures taken from sites that hadn’t been disturbed in the past 167 years, the researchers were able to gain insights into how disturbance histories influence forest soils. The results of the study are detailed in a paper published in the journal Nature Geoscience.

Bowd said the team’s findings show that forest soils recover from disturbances slowly over many years — up to 80 years following a wildfire and as many as 30 years after logging, much longer than previously thought. In other words, both natural and human disturbances can have long-lasting effects on forest soils, potentially impacting plant communities and ecosystem health for decades.

During high-intensity forest fires, soil temperatures can top 500 degrees Celsius (932 degrees Fahrenheit), which leads to the loss of soil nutrients, Bowd explained. Meanwhile, logging exposes the forest floor, compacts soils, and alters soil structure in ways that can also reduce vital soil nutrients. And these declines grow more severe as forests experience instances of fire and logging repeatedly without having sufficient time between disturbances to fully recover.

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Photo: Victoria’s Mountain Ash forests in Australia. Photo Credit: Tabitha Boyer, ANU

Source: news.mongabay.com

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