MCR Monthly Newsletter

October 2025

September 22 was the Autumnal equinox, and it marks the end of summer. On that day, the amount of daylight and darkness were equal. Now it is Autumn, and the nights are longer than the daylight hours. It’s that shortening length of day that is the primary trigger for trees to change the color of their leaves in the fall.

With the longer cooler nights the trees cut back on the production of chlorophyll (the green pigment) in leaves. However, green tree leaves do need the green pigment, chlorophyll, for photosynthesis to convert sunlight into energy, but the pigment itself doesn’t absorb green light; instead, it reflects it, which is why we see the leaves as green. The reason leaves don’t simply use the most abundant or most energetic light is due to chlorophyll’s molecular structure, which evolved to balance light absorption and prevent potentially damaging excess energy, making stability more important than maximum efficiency for plants. 

In the fall season with shorter daylight hours, this reduction of the chlorophyll in the leaves provides the opportunity for other pigments in the leaves to no longer be over-powered by the dominant green pigment.  So yellow and orange pigments (carotenoids) and the red pigment (anthocyanin) can become visible in leaves.  For example, sugar maple trees turn a brilliant red in the fall because of the now visible anthocyanin (red pigment) is still in the leaves. Now the forest Merrill Creek Reservoir is ablaze with magnificent colors!

Eventually, practically all the leaves will fall off the deciduous trees (trees that shed leaves). Trees lose the leaves in winter to conserve water, which when the ground is frozen is difficult to absorb. So, the tree must conserve as much water as possible until spring.

Evergreen trees (conifers) are uniquely adapted for the cold and do not shed their leaves (needles) which have a waxy coating to retain water. An exception to this adaptation for conifers is the Tamarac tree, a rare deciduous conifer.  At MCR, European Tamarac trees can be seen in the Boat Ramp parking areas and along Fox Farm Road.

Many of our animals like bears and deer are bulking up on acorns (mast) to gain fat to last them through the winter.  Gray squirrels and chipmunks that don’t truly hibernate are storing (cashing) acorns and other nuts and seeds underground and in hollow logs to get them through until spring.

Migrating birds make important pit stops here at Merrill Creek to rest or fuel up with food. And migrating Monarch butterflies pass through Merrill Creek on their way to Mexico. In the past MCR had 2 Monarch butterflies tagged (cellophane wing tags) and documented that they made it 2,080 miles to Mexico!

I hope you get out and enjoy the brisk weather and beautiful fall coloration within the project.

And Happy Halloween,

Ranger Rich