Forest soil needs decades or centuries to recover from fires and logging



File 20190121 100288 15v1q9i.jpg?ixlib=rb 1.1

David Blair, Author provided

Elle Bowd, Australian National University and David Lindenmayer, Australian National University

The 2009 Black Saturday fires burned 437,000 hectares of Victoria, including tens of thousands of hectares of Mountain Ash forest.

As we approach the tenth anniversary of these fires, we are reminded of their legacy by the thousands of tall Mountain ash “skeletons” still standing across the landscape. Most of them are scattered amid a mosaic of regenerating forest, including areas regrowing after logging.




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But while we can track the obvious visible destruction of fire and logging, we know very little about what’s happening beneath the ground.

In a new study published in Nature Geoscience, we investigated how forest soils were impacted by fire and logging. To our surprise, we found it can take up to 80 years for soils to recover.

Logging among the charred remains of Mountain ash after the 2009 fires.
David Blair, Author provided

Decades of damage

Soils have crucial roles in forests. They are the basis for almost all terrestrial life and influence plant growth and survival, communities of beneficial fungi and bacteria, and cycles of key nutrients (including storing massive amounts of carbon).

To test the influence of severe and intensive disturbances like fire and logging, we compared key soil measures (such as the nutrients that plants need for growth) in forests with different histories. This included old forests that have been undisturbed since the 1850s, forests burned by major fires in 1939, 1983 and 2009, forests that were clearfell-logged in the 1980s or 2009-10, or salvage-logged in 2009-10 after being burned in the Black Saturday fires.

We found major impacts on forest soils, with pronounced reductions of key soil nutrients like available phosphorus and nitrate.

A shock finding was how long these impacts lasted: at least 80 years after fire, and at least 30 years after clearfell logging (which removes all vegetation in an area using heavy machinery).

However, the effects of disturbance on soils may persist for much longer than 80 years. During a fire, soil temperatures can exceed 500℃, which can result in soil nutrient loss and long-lasting structural changes to the soil.

We found the frequency of fires was also a key factor. For instance, forests that have burned twice since 1850 had significantly lower measures of organic carbon, available phosphorus, sulfur and nitrate, relative to forests that had been burned once.

Sites subject to clearfell logging also had significantly lower levels of organic carbon, nitrate and available phosphorus, relative to unlogged areas. Clearfell logging involves removing all commercially valuable trees from a site – most of which are used to make paper. The debris remaining after logging (tree heads, lateral branches, understorey trees) is then burned and the cut site is aerially sewn with Mountain Ash seed to start the process of regeneration.

Fire is important to natural growth cycles in our forests, but it changes the soil composition.
David Lindenmayer, Author provided

Logging compounds the damage

The impacts of logging on forest soils differs from that of fire because of the high-intensity combination of clearing the forest with machinery and post-logging “slash” burning of debris left on the ground. This can expose the forest floor, compact the soil, deplete soil nutrients, and release large amounts of carbon dioxide into the atmosphere.

Predicted future increases in the number, frequency, intensity and extent of fires in Mountain Ash forests, coupled with ongoing logging, will likely result in further declines in soil nutrients in the long term. These kinds of effects on soils matter in Mountain Ash forests because 98.8% of the forest have already been burned or logged and are 80 years old or younger.

To maintain the vital roles that soils play in ecosystems, such as carbon storage and supporting plant growth, land managers must consider the repercussions of current and future disturbances on forest soils when planning how to use or protect land. Indeed, a critical part of long-term sustainable forest management must be to create more undisturbed areas, to conserve soil conditions.




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Specifically, clearfell logging should be limited wherever possible, especially in areas that have been subject to previous fire and logging.

Ecologically vital, large old trees in Mountain Ash forests may take over a century to recover from fire or logging. Our new findings indicate that forest soils may take a similar amount of time to recover.The Conversation

Elle Bowd, PhD scholar, Australian National University and David Lindenmayer, Professor, The Fenner School of Environment and Society, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Banning fishing has helped parts of the Great Barrier Reef recover from damage


Camille Mellin, Australian Institute of Marine Science; Aaron MacNeil, Australian Institute of Marine Science, and Julian Caley, Australian Institute of Marine Science

The world’s coral reefs face unprecedented threats. Their survival depends on how well they can cope with a long list of pressures including fishing, storms, coral bleaching, outbreaks of coral predators and reduced water quality. Together, these disturbances have caused the Great Barrier Reef to lose half of its coral cover since 1985.

One often-used way of protecting marine ecosystems is to close parts of the ocean to fishing, in no-take marine reserves. From research, we know that by reducing fishing you end up with more and bigger fish (and other harvested species such as lobsters).

But other benefits of protection might be more surprising. In a new study, we show that no-take reserves helped the Great Barrier Reef’s corals to resist a range of disturbances, such as bleaching, disease and crown-of-thorns starfish, and to recover more quickly from damage.

More exposure, but better protection

Our study used observations between 1993 and 2013 of 34 types of coral and invertebrates and 215 fish species on 46 reefs spread across the Great Barrier Reef. Among the 46 study reefs, 26 were open to fishing and 20 were in no-take marine reserves.

During the study period, several occurrences of coral bleaching, coral disease, storms and outbreaks of crown-of-thorns starfish were recorded.

The total number of disturbances affecting our study reefs increased in recent years (2010-12), mostly due to severe storms affecting the central and southern sections of the Great Barrier Reef. Among our study reefs, those located inside no-take marine reserves were more exposed to disturbance than those outside no-take marine reserves.

Our study showed that, inside no-take marine reserves, the impact of disturbance was reduced by 38% for fish and by 25% for corals compared with unprotected reefs. This means that no-take marine reserves benefit not only fish but entire reef communities, including corals, and might help to slow down the rapid degradation of coral reefs.

Damaged coral reef around Lizard Island a few days after cyclone Ita.
Photo by Tom Bridge, http://www.tethys-images.com

Faster recovery

In addition to greater resistance, reef organisms recovered more quickly from disturbance inside no-take marine reserves. After each disturbance, we measured the time that both coral and fish communities took to return to their pre-disturbance state.

We found coral communities took the longest to recover after crown-of-thorns starfish outbreaks. Outside no-take marine reserves, it took on average nine years for these communities to recover. It took just over six years inside no-take marine reserves.

Although there is more work to be done, one reason that reefs inside no-take zones are able to cope better with disturbances is that they preserve and promote a wider range of important ecological functions. Where fishing reduces the numbers of some species outside protected areas, some of these functions could be lost.

Coral reef showing signs of recovery.
Photo copyright Tom Bridge/www.tethys-images.com

Knowledge for conservation

Marine reserves (including no-take zones) currently cover 3.4% of the world’s ocean, which is still well below the 10% target for 2020 recommended by the Convention on Biological Diversity. The slow progress towards this target is partly due to the perceived high costs of protection compared to true ecological benefits, which can be difficult to gauge. While some surprising benefits are beginning to be revealed in studies like ours, such benefits remain little understood.

Our results help to fill that gap by showing that no-take marine reserves can boost both the resistance and recovery of reef communities following disturbance. In ecology, resistance plus recovery equals resilience.

Our work suggests that the net benefit of no-take marine reserves is much greater than previously thought. No-take marine reserves host not only more and bigger fishes, but more resilient communities that might decline at slower rates.

These results reinforce the idea that no-take marine reserves should be widely implemented and supported as a means of maintaining the integrity of coral reefs globally.

Our conclusions also demonstrate that we need long-term monitoring programs which provide a unique opportunity to assess the sustained benefits of protection.

The Conversation

Camille Mellin, Research Scientist, Australian Institute of Marine Science; Aaron MacNeil, Senior Research Scientist, Australian Institute of Marine Science, and Julian Caley, Senior Principal Research Scientist, Australian Institute of Marine Science

This article was originally published on The Conversation. Read the original article.

The Southwest’s forests may never recover from megafires


Grist

If you doubt that climate change is transforming the American landscape, go to Santa Fe, N.M. Sweltering temperatures there have broken records this summer, and a seemingly permanent orange haze of smoke hangs in the air from multiple wildfires.

Take a ride into the mountains and you’ll see one blackened ridge after another where burns in the past few years have ravaged the national forest. Again, this year, fires in New Mexico and neighboring states of Colorado and Arizona are destroying wilderness areas.

Fire danger is expected to remain abnormally high for the rest of the summer throughout much of the Intermountain West. But “abnormal” fire risks have become the new normal [PDF].

The tragic deaths of 19 firefighters in the Yarnell fire near Prescott, Ariz., last month shows just how dangerous these highly unpredictable wind-driven wildfires can be.

The last 10 years have seen more than 60 megafires over…

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Uluru: Not On


A little while back I posted about a planned trip to Uluru in the near future – sadly I have had to cancel the trip because I am concerned about my run of poor health. I have basically been sick since November last year and had pneumonia 4 times during this time. So the trip will be postponed for a year to ensure I recover fully.