Wednesday, April 29, 2009

Wild weather affects wildflowers in the West

As I write this we are ending yet another snowstorm/winter advisory here in the northern Rockies region. This is a good time to consider how weather influences when plants come out in the spring. It has been a cool spring so far which is great news for skiers, and if this continues it will be a welcome relief from many years of drought and fires up here. Buttercups are the harbinger of spring and generally flower a few days after the soil thaws in the spring. This spring our first Project BudBurst observations of Buttercups were on March 17th, just a few days later than our historical average, but weeks late compared to recent years (e.g. March 7th in 2007). Just before this latest snowstorm Western serviceberry (Amelanchier alnifolia) was in full bloom. Serviceberry started blooming on April 23rd this year, within a day of its historical average. Last year by contrast serviceberry was quite late (first Project BudBurst observation of May 2nd).

It is not unusual that some species may be a bit late while others may be a bit early in a given year. Variability in when plants come out in spring is often explained by changes in temperature during the season. For example while we have had a lot of cold spells that led to the first wildflowers being late, just last weekend we had a stretch of 4 days with temperatures close to 70 or even 80 degrees, after which dozens of species of plants sent out new leaves above the ground. So it depends on when a plant normally flowers in the spring and the weather immediately before that time as to how late or early it might be in a given year (in our region it is usually the previous 10 days or so that is critical). This makes plant watching in the mountains of the West always interesting – every year, or maybe every week it is a little different!

For a total contrast consider Southern California. While it has been a bit cooler than normal this year as in the rest of the country what is most important for early wildflowers are the winter rains. So despite recent dry months there was enough moisture left from epic rainstorms in December (the famous “pineapple express”) to provide lush green growth and wildflowers covering hillslopes in early March. In San Diego I saw natural areas that were effected by the wildfires in 2007 now carpeted with pastel colors of orange, purple, and red, mostly from California poppy (Eschscholzia californica), tall phacelia, and lupines. By early April the poppies were beginning to fade but many other native annuals and perennials were beginning to bloom such as colorful bush monkey flowers (Mimulus aurantiacus).

These unusual cool wet springs are important times to see how nature can adapt to these wild swings in weather. In dry environments like grasslands, for example, these are often one of the few times that many plants provide a large crop of fruits and new seedlings. In a local grassy mountain slope I have been observing over the years for example you generally find a whole range of wildflowers which only flower during these kinds of years. This year for example we saw a white variety of the common shooting star (Dodecatheon conjugans) for the first time since 2003. This is another reason why we need years of observations to better understand these places.

The contrast in what is happening across country this year (compare these observations with those from Chicago in last week’s blog) as well as the wild variation from year to year shows why it will be so important for scientists to have data from programs like Project BudBurst to help sort things out. Check out our live maps to see how spring is unfolding across the country, and how it compares to what you are seeing in your area. I am sure more surprises await us, as the year progresses…

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