Jan 30, 2014

January is fire and water sweet spot

Green is good:

On the calendar graph below "green-colored" coding means the natural fire breaks (i.e. cypress domes, strands and marshes) are still flooded.


T
his historical calendar shows a full history of wildand drought severity in Big Cypress National Preserve.  You can clearly see how our big wildfires correspond to the biggest drought years.  Usually it isn't until April and May that deep drought has the full potential to develop in the swamp.  Current conditions are green, indicating that natural fire breaks are still flooded.

But that's not too much of a surprise, either.

January is usually a sure bet to be a perfect time for a prescribed burn.  Some Januaries we see fire breaks starting to become patchy, but rarely if at all are they completely dry so soon.


The diagram below shows a annual and monthly frequency of occurrence of drought severity in Big Cypress National Preserve, from 1991 to present.  Can you see how the orange (i.e. dry fire breaks) and red (i.e. extreme drought) categories never appear in January?  The diagram also reveals, unsurprisingly, that drought severity peaks in April and May.

But even in late spring, there's a small chance the green zone could prevail.


T
he two charts above show the long-term monthly and annual distribution of drought for Big Cypress National Preserve.  Can you see that
extreme drought is very rare in the swamp, but when it does occur we can count on it happening in April, May or June.  January, by comparison, has zero chance historically of deep drought occurring.    

The advantage to burning then is that, if the summer floods are soon to follow, the combined burn/flood sequence stands a highly desirable chance of killing back pesky wax myrtle (Snyder and Hilton, 2010).  But usually April and May are wildfire suppression season in the swamp.

That makes January a much safer bet for finding the "prescribed burning" sweet spot when desiccated vegetation and flooded fire breaks and hydric soils co-exist.

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