things off, typically resulting in less-than-optimal colors. In addition, strong winds
can physically remove the leaves from trees, ending any fall color. Put these fac-
tors together, and you’ll understand how fall colors can vary from year to year.
Warming global temperatures have recently delayed the onset of the autumn
transition in most regions. One study indicated that this delay has approached two
weeks over the past 40 years. One problem is that the fall cue of cooling tempera-
tures is being separated from the cue of lengthening nights, which has remained
the same. This likely produces stress for trees. In spring, we’ve seen a problem
with an early start to the growing season because of overall warming temperatures,
making plants more susceptible to killing freeze events, which still occur. A simi-
lar effect could occur in fall: If leaf change is delayed by warmth, a freeze event
could negatively impact the process.
Another concern would be the increase in severe weather events. Droughts,
heavy rains, hurricanes, and wildfires can do immense damage to tree populations.
In time, we may even see tree species change. Already we’ve seen some species
migrating poleward. This could certainly affect fall colors.
If you want to know about fall leaf conditions in your area, call the United
States Forest Service Fall Color hotline (1-800-354-4595), or check its website,
http://www.fs.fed.us/fallcolors. The Foliage Network (www.FoliageNetwork.com) keeps
track of leaf colors in the Midwestern and Eastern portions of the country. The
National Phenology Network (www.USANPN.org) keeps track of fall leaf changes,
as well as other seasonal vegetation changes. There’s even a fall foliage prediction
map produced by the folks at SmokyMountains.com (www.SmokyMountains.com/
Fall-Foliage-Map). They use historical data on weather and past foliage peaks,
in conjunction with more current observations, to generate a nationwide forecast.
They do add a proviso that predictions can be thrown off by extreme weather
events, such as heavy rainfall.
If you live where leaves change with the seasons, consider yourself lucky. The
complex hues of fall are some of the most brilliant wonders nature offers.For 30-plus years, Ed Brotak taught thousands of college students about weather, and
helped many of them pursue careers in meteorology. He lives in Asheville, North Carolina,
with his wife and daughters.ADO
BE^ S
TOCK
/SN
EHI
T
GO GREEN!
GO ORGANIC!
GO MIGHTY MAC
®!
Phone: 800-348-1117
Fax: 610-495-5951
[email protected]
http://www.mackissic.comCircle #11; see card pg 65Circle #16; see card pg 65