Can a Forest Die? Timeframe to Recover After a Blaze

[ORF]

Summary: If a forest is scorched, after a while it will regrow(wont it?); but if it is periodically burnt to ashes, could it eventually die? (as a ecosystem) What is the time-scales in order to recover a forest after a blaze?

Hello,

If a forest is scorched, after a while it will regrow (wont it?); but if it is periodically burnt to ashes, could it eventually die? (as a ecosystem) What is the time-scales in order to recover a forest after a blaze?

Thank you for your time.

Regards,
orf

<Mentor move to Biology & Medicine>

 

[jim mcnamara]

Short answer --- Periodic fires are good; required for many communities.

Read about succession - It is a term that defines the repeating life cycles of a of a series of groups of 'meta-organisms' called communities: i.e., early sucessional communities depend on massive disturbances like floods, landslides, and fires. No fires for hundreds of year means the dormant seed populations of early successional communities dwindle. Meaning: periodic massive disturbances are required.
https://en.wikipedia.org/wiki/Ecological_succession
This is the reason why fire suppression in USDA managed forests has been devastating and ongoing. Overgrowth, super massive fires, and extensive property damage.

There are pine species that require fires to release seeds from the cone: Jack pine serotinous cones for example. Serotinous means cones that have hard resin that prevents seed shedding. It requires high temperatures to break the hardened goo and release the seeds.
See the video about why pines love fire: https://wildfiretoday.com/2016/02/11/ted-ed-video/

 

[Nik_2213]

You could also look at the consequences of Mt. St. Helens' eruption.

One proviso: If eco-system has sufficiently changed, such there are eg no mega-herbivores spreading nuts / seeds etc in their dung, some mature tree types you had may be the last of their kind in that area, and will not appear in 'succession' re-growth...
:-(

 

[jim mcnamara]

@Nik_2213 - re: your proviso --- assuming no buried seed populations. Fire and even thin lava flows do not eradicate them. Massive violent waters flows move them to new environments.

Also see https://web.stanford.edu/group/stanfordbirds/text/essays/Island_Biogeography.html
(which is bird oriented). Think of birds as propagules. This is how allopatric species move into new environments and then evolve relatively unaffected by external gene flow.

This video of Mt St Helens shows what you mean, but note lots of larger species of plants.

 

[pinball1970]

Short answer --- Periodic fires are good; required for many communities.

Read about succession - It is a term that defines the repeating life cycles of a of a series of groups of 'meta-organisms' called communities: i.e., early sucessional communities depend on massive disturbances like floods, landslides, and fires. No fires for hundreds of year means the dormant seed populations of early successional communities dwindle. Meaning: periodic massive disturbances are required.
https://en.wikipedia.org/wiki/Ecological_succession
This is the reason why fire suppression in USDA managed forests has been devastating and ongoing. Overgrowth, super massive fires, and extensive property damage.

There are pine species that require fires to release seeds from the cone: Jack pine serotinous cones for example. Serotinous means cones that have hard resin that prevents seed shedding. It requires high temperatures to break the hardened goo and release the seeds.
See the video about why pines love fire: https://wildfiretoday.com/2016/02/11/ted-ed-video/

This is crazy, I never would have imagined an organism would have evolved with fire as a factor!
I suppose if the fires are regular enough over a long period that satisfies the criteria for evolutionary change then it makes sense

 

[jim mcnamara]

https://en.wikipedia.org/wiki/Pinus_ponderosa Ponderosa pine has bark that withstands ground fires, the bark smells like vanilla, FWIW.

This constant clearing (every n years a ground fire burns through), clears out competing species as saplings, giving the pine saplings an edge. Sometimes this backfires and you get a dogtooth stand (stunted very old, very closely spaced, tree "blob") . A "normal" 10cm DBH ponderosa is circa 10 years old, dogtooth pines can be 40+ years old, same size diameter. The trees in the stand are severely stressed and do not reproduce. With decreased mortality compared to "standalone" individuals. In managed forests thinning is required to increase productivity. Technical paper on thinning:
https://www.fs.fed.us/psw/publications/zhang/psw_2013_zhang002.pdf
PS: the dogtooth thing got worse because of the USDA and Dept of Interior had a complete burn restriction on Federal lands atarting about 1934. Now they have prescribed burns. Took 'em a while to get the message.

One of the graphs represents data (see Stand Density Index (SDI)) from areas with dogtooth stands. Because of all the buzzwords and abbreviations, perhaps this paper is not the best, merely the only recent one I could find. Google search-fu failure ...

 

[Tom.G]

Here is a time lapse covering 37 years of recovery in 1 minute, not great but interesting.


My wife and I visited Mt. St. Helens about a year after eruption. The Rangers at the Information Center there noted that small burrowing mammals (ground squirrel types) were contributing to regrowth by spreading seeds.

Somewhere, we have a few rolls worth of 35mm slides we shot from an overflight in a chartered plane. The most obvious feature from the air was the fractal network of rain drainage channels forming a few new rivers.

More on-subject, the California Redwood forest is in an area that has been subject to wildfires over millenia. The bark on Redwoods is several inches thick and quite light-weight, supposedly evolved to protect the tree from the frequent fires.

Cheers,
Tom

 

[Rive]

A different point of view: a forest is not always the actual stable, 'natural' state of an area. Either due human intervention, change in fauna or change in climate it might be considered just a 'remnant'. In such case a fire can easily give the killing blow.