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



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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.




Read more:
Comic explainer: forest giants house thousands of animals (so why do we keep cutting them down?)


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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How we found 112 ‘recovery reefs’ dotted through the Great Barrier Reef


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Some reefs are strong sources of coral larvae.
Peter Mumby, Author provided

Peter J Mumby, The University of Queensland

The Great Barrier Reef is better able to heal itself than we previously imagined, according to new research that identifies 112 individual reefs that can help drive the entire system towards recovery.

The back-to-back bleaching events in 2016 and 2017 that killed many corals on the Great Barrier Reef have led many researchers to ask whether and how it can recover. Conventionally, we tend to focus on what controls recovery on individual reefs – for example, whether they are fouled by seaweed or sediments.

But in our study, published in PLoS Biology, my colleagues and I stepped back to view the entire Great Barrier Reef as a whole entity and ask how it can potentially repair itself.


Read more: The Great Barrier Reef can repair itself, with a little help from science


We began by asking whether some reefs are exceptionally important for kick-starting widespread recovery after damage. To do this we set three criteria.

First, we looked for reefs that are major sources of coral larvae – the ultimate source of recovery. Every year corals engage in one of nature’s greatest spectacles, their mass reproduction during a November full moon. Fertilised eggs (larvae) travel on ocean currents for days or weeks in search of a new home.

With our partners at the CSIRO we’ve been able to model where these larvae go, and therefore the “connectivity” of the reef. By using this modelling (the Great Barrier Reef is far too large to observe this directly), we looked for reefs that strongly and consistently supply larvae to many other reefs.

Healthy reefs supply far more larvae than damaged ones, so our second criterion was that reefs should have a relatively low risk of being impacted by coral bleaching. Using satellite records of sea temperature dating back to 1985, we identified reefs that have not yet experienced the kind of temperature that causes mass coral loss. That doesn’t mean these reefs will never experience bleaching, but it does mean they have a relatively good chance of surviving at least for the foreseeable future.

Our final criterion was that reefs should supply coral larvae but not pests. Here we focused on the coral-eating crown-of-thorns starfish, whose larvae also travel on ocean currents. We know that outbreaks of these starfish tend to begin north of Cairns, and from that we can predict which reefs are most likely to become infested over time.

Fortunately, many good sources of coral larvae are relatively safe from crown-of-thorns starfish, particularly those reefs that are far offshore and bathed in oceanic water from the Coral Sea rather than the currents that flow past Cairns. Indeed, the access to deep – and often cooling – ocean water helps moderate temperature extremes in these outer reefs, which also reduces the risk of bleaching in some areas.

Using these three criteria, we pinpointed 112 reefs that are likely to be important in driving reef recovery for the wider system. They represent only 3% of the reefs of the Great Barrier Reef, but are so widely connected that their larvae can reach 47% of all the reefs within a single summer spawning season.

Unfortunately, their distribution across the reef is patchy. Relatively few are in the north (see map) so this area is relatively vulnerable.

Black dots show reefs identified as strong sources of coral larvae; grey dots show other reefs.
Hock et al., PLoS Biol.

Our study shows that reefs vary hugely, both in their exposure to damage and in their ability to contribute to the recovery of corals elsewhere. Where these patterns are pretty consistent over time – as is the case for the reefs we identified – it makes sense to factor this information into management planning.

It would be sensible to improve surveillance of these particular reefs, to check that crown-of-thorns starfish do not reach them, and to eradicate the starfish if they do.

To be clear, these are not the only reefs that should be managed. The Great Barrier Reef already has more than 30% of its area under protection from fishing, and many of its other individual reefs are important for tourism, fisheries and cultural benefits.

But the point here is that some reefs are far more important for ecosystem recovery than others. Factoring these patterns into tactical management – such as how best to respond in the aftermath of a cyclone strike – is the next step. It’s a need that has been articulated repeatedly by the Great Barrier Reef Marine Park Authority.


Read more: Coal and climate change: a death sentence for the Great Barrier Reef


Taking the long-term view, the greatest threats to the reef are rising sea temperatures and ocean acidification caused by elevated carbon dioxide levels. This is clearly a challenge for humanity and one that requires consistent policies across governments.

But local protection is vital in order to maintain the reef in the best state possible given the global environment. Actions include improvements to the quality of the water emerging from rivers, controlling crown-of-thorns starfish, and maintaining healthy fish populations.

The ConversationThis is an expensive process and resources need to be deployed as effectively as possible. Our results help target management effectively by revealing the underlying mechanisms of repair on the reef. If management can help protect and facilitate corals’ natural processes of recovery, this might go a long way towards sustaining the Great Barrier Reef in an already challenging environment.

Peter J Mumby, Chair professor, The University of Queensland

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

Recuperation


This is a post I’m putting up at all my Blogs, even though that particular Blog may be unaffected due to scheduled posting, etc. Blog posts may be down a little at the moment and that for the last week or so. I have been ill with various illnesses and complaints for the last several weeks, so I have now decided to take the next week off from most Blogging activities in an attempt to rest and recover – if I can while still actually doing my very physically demanding actual job in the real world. I hope to return to Blogging full time in about a week’s time.

Limited Posts


I have had some surgery in recent times and while everything seems to be going OK, healing well and all the rest, I have been finding some difficulty while sitting at the computer – so I have been easing off on the posts in recent times. I expect this will continue for the next couple of weeks or perhaps a bit longer than that. I don’t intend to stop posting completely, but there will be far fewer posts during this period. One or two Blogs that I have will receive no posts during this time, while one or two others will continue to receive the same number of posts throughout this period. However, it is all a bit of a daily thing as to just how many posts I upload.

So all is going well, but a bit of a break and rest is needed to ensure a full recovery. Thanks all 🙂

USA: Return of the Western Bumblebee


The link below is to an article heralding the return of the Western Bumblebee, which holds out hope for its recovery throughout its former range.

For more visit:
http://www.newsdaily.com/article/fdce1822642c89a302507345c64aa787/return-of-long-absent-bumblebee-near-seattle-stirs-scientific-buzz

Grand Cayman Blue Iguana: Recovering Well


The link below is to an article that reports on the recovery of the Grand Cayman Blue Iguana. It’s a good news story.

For more visit:
http://www.iucn.org/about/work/programmes/species/?11299/Grand-Cayman-Blue-Iguana-takes-step-back-from-extinction