Where have the fall colours gone?

 All last week I could barely contain my excitement: I was going to visit my parents for the weekend.  Although I love my parents dearly, it was actually fall I was looking forward to seeing.  Fall is best discovered in the country, where its smell and splendour are evident everywhere; while raking the yard, grouse hunting, pumpkin picking, and most of all – gazing at the beautiful coloured leaves.



Dramatic hobblebush leaf

Fall colour-seeking tourists, also called ‘leaf peepers’, travel from all over the country to visit my hometown area during the fall.  The huge assortment of deciduous tree types, combined with the rolling hills, perfectly displays Mother Nature’s artwork.  How lucky am I to have grown up in such an area, where I was able to take in the magic every fall from my front porch.

On the drive up last Saturday morning, I too turned into a ‘leaf peeper’; checking out the usual colour hot spots.  Upon passing R Lake – a small pond backed by a large rolling hill – my heart sunk.  The reds, oranges, and yellows were few and far between; instead browns and bare branches dominated the scenery.

As soon as I got out of the car at my parents’ house, I ran to the front yard to check out their beautiful red maple.  This tree is an attention getter.  It sits right at the corner of my parents’ lot, and could stop the traffic driving by during the fall.  Then, it normally has leaves that are fiery red, spotted with mustard yellow; a perfect backdrop to my family’s annual autumn photo.  Although many leaves were still on the tree, there were more boring browns than striking reds.

Was I just too late?  Did I miss it?  I couldn’t have.  Normally, the most intense colours weren’t on display until Thanksgiving weekend, and I was a week early.  So why were the colours so drab and the leaves shedding so early this year compared to those in the past?

Smokebush leaf, having an assortment of
beautiful colours

In the fall, leaves change colour mostly in response to changes in day length; deciduous trees are especially sensitive to the amount of daily darkness.  As the days become shorter in September and October, an abscission layer – a sheet of dry, corky cells – builds between the leaf and branch.  This layer blocks transport of materials from the leaf to tree, and vice versa.  Chlorophyll can no longer be transported to the leaves, and the leaf chlorophyll remaining is broken down by the sun.  Only pigments masked before by chlorophyll, like xanthophylls, carotenoids, and tannins – giving leaves their orange, yellow, and brown colours – remain.  As well, anthocyanins are produced inside the leaf, which are responsible for red and purple hues.  Eventually, as fall progresses and the days get shorter and shorter, the abscission layer becomes so thick that the leaves fall off. 

This year, fall day length was shorter than normal.  September and October were plagued by cloudy, windy, rainy days that reduced the amount of sun available to the trees each day.  This premature increase in the amount of daily darkness likely increased the rate of the abscission process; leaves were shed earlier than normal especially with an extra push from the wind and rain.





Drab aspen leaf covered in frost

Temperature also plays a role in the fall colour spectacular.  Cool nights and warm days lead to the most explosive hue combinations.  Along with the dreary weather, an early, harsh cold snap was also experienced this fall.  Pigments break down when exposed to cold, and anthocyanin production is inhibited; leading to drab, brown leaves evident everywhere.

So it is likely Mother Nature, herself, who sabotaged her own artistry.  Despite my disappointment in missing fall’s best attribute, my thoughts quickly shifted and I soon became excited again; bare tree branches increase visibility in the forest interior, making it prime grouse hunting time!  J

Source: http://www.usna.usda.gov/PhotoGallery/FallFoliage/ScienceFallColor.html