Sonoran Desert Fire Regimes

[chumley]

In the past few years, Tonto NF has put almost zero effort into extinguishing fires that burn in their jurisdiction*, but they made this pfancy video showing that they're at least looking at what happens after they let it burn.

*except for keeping it from burning over onto private property where apparently there are "values" at risk.



tldr: the Sonoran Desert as we knew it is gone forever

[toddak]

Sounds like human-introduced, non-native species like buffelgrass and fountain grass are the bottom line problem, hard to see how that can ever be reversed. So yeah, gone forever is probably right.

[chumley]

@toddak
Well the video says as much. The invasive species are here to stay. And where fire used to be a rare occurrence in the low desert (they snuck in a 200-500 year estimate), it is now expected to occur in cycles of less than 30 years. Which will eliminate saguaros since it takes that long before it reproduces. And as a ladder for severe fire to feed into chaparral and ponderosa those ecosystems are at existential risk here too.

But there's not enough rainfall to transform the lowlands into a grassland ... so what is it then? A "desert grassland"? (perhaps just a "desert wasteland")

The discussion of riparian areas was of interest to me. It indicated that they may recover if there's still enough moisture in the soil. But it didn't discuss how the loss of 100-year old large shady sycamores and cottonwoods would accelerate the loss of moisture in those areas. Very few new shade trees will be able to grow to maturity along a creek if there's a fire and a flood every 30 years.

[nonot]

@chumley
Many Forests burn every 30 years or less and there's still plenty of trees that grow there. Maybe we'll figure out that more frequent fires of low intensity in the desert will help saguaros and cottonwoods to grow? It seems in general the more grass you have the more frequent you seem to want to have fires. Or perhaps prickly pear will grow to dominate as it seems more fire-hardy than the saguaros. Perhaps more research required...

[The_Dude]

One thing to keep in mind is that human intervention can reverse some of the damage. Diversity will be reduced, no doubt about that, but a thriving native plant trade will keep many of the iconic species alive. Saguaros are well represented, as with many trees and shrubs. If we can pull our collective heads out of the sand, mitigation can happen. My nursery grew hundreds of thousands of Ponderosa seedlings to help replant the rim following major fire events there too. Not saying we don't have a problem, but solutions can be had.

[azbackpackr]

@The_Dude
Indeed, and in fact, Natural Restorations, a non-profit, has a replanting event coming up on Feb 19: http://www.naturalrestorations.org/new-events-1

[eru]

There's different levels of intensity with fires as @nonot alluded to.

Non fire adapted environments like the low desert are a situation I don't have any real answers for, but all shade bearing trees gone in all riparian areas etc seem highly unlikely to me. I suppose as the climate gets more erratic, droughts will create conditions favorable to that once grass fed fires hit them - that seems to be what happened in the lower part of Oak Spring Canyon. Creating firebreaks to at least limit fires might be helpful, though that also negatively impacts insect movement and runoff. I'm not sure how you get rid of all the grass and that's the core issue in terms of the biome changing, fires or otherwise.

Managed/controlled burns when things are wetter could help clear out fuel, which would help keep riparian areas more resilient for when a fire does catch in a drier period. It seems like there will either be grassland type fires ripping through things regularly (idiots or not), and the non-native fuel would grow back fast enough that it'd be a bit of an impossible task however.

I had more here, but it's better suited for another thread so I'm moving it over.