Monday, September 27, 2010

Sensory explorations on Norm's Island

On these gorgeous fall days (and even on the colder, rainy ones), our Center staff is outdoors with students engaging in hands-on explorations to learn about native plants, insects, birds, and other wildlife. Our educational programs emphasize direct observation and inquiry as a way to learn about the natural world. One of the elementary students' favorite activities is Meet A Tree in which they are blindfolded and must use their other four senses to "meet" a cottonwood tree. Each student is brought by a partner to a tree, and given an opportunity to feel the tree, smell it, listen to it (as this student from Newman ES is doing by knocking on the bark), and if they so choose, to taste the tree. Upon returning to the circle, each students' blindfold is taken off and they must go find "their" tree. In describing how they found their tree, the students refer to an amazing diversity of clues. Some of these include remembering whether the sun was on their face or back, remembering the placement of branches, the slope of a hill they walked up, and even seeing a wet mark where they did lick their tree. It is a challenge to rely on and trust a partner to lead them through the forest, and this in itself is a valuable learning experience. Humans are very reliant on our sense of sight to navigate the world, followed closely by hearing. We use our sense of sight in almost everything we do from reading to walking to eating. The Meet a Tree exercise helps students to tune into their other senses, and to use these to become increasingly aware of the world around them.

During this activity the students also learn about cottonwood natural history as we explore the riparian ecosystem (riparian land is that which is found near water). We have two kinds of cottonwood trees on Norm's Island: narrowleaf and plains cottonwood. They are easily identifiable by their leaves which differ significantly in size and shape. Narrowleaf trees have long, lance-like leaves, whereas the plains trees have large, spade-shaped leaves. Both types of cottonwood trees thrive in riparian areas, and therefore are a sign of a moist area. If you are traveling across the plains of eastern Montana and see a line of cottonwood trees in the distance, it is a sure indication that there is a creek ahead. Riparian areas are used by 85% of the animal species in Montana at some point in the year, and therefore provide critically important habitat.

Cottonwood trees are dioecious, meaning that each tree is either male or female. Flowering and pollination coincide with springtime peaks in riverine flows. Cottonwood seeds are borne by fluffy, cotton-like hairs and can be dispersed long distance by both wind and water. Seed dispersal usually occurs as river levels are falling, and therefore seeds have an increased probability of landing in favorable moist microsites along the river channel. The soil must stay moist throughout the early stages of seedling establishment. This reliance on a moist growing site explains why it is often said that cottonwood trees need flooding to spread to new areas. Rising and falling river levels create the ideal growing sites for young cottonwoods. Cottonwood seedlings and saplings can not tolerate drought, but they can tolerate inundation by water and silt. They are truly well-adapted to living in the riparian ecosystem.

Next time you are out for a walk along a river, observe the cottonwoods and see if you can identify whether they are narrow-leaf or plains cottonwoods. Observe too their thick, grey bark which helps to protect them from fire. Do you see any cavities (holes) in the tree that animals might be living in? What do your senses tell you about these trees?

Wednesday, September 22, 2010

Autumnal Equinox

Today is the Autumnal Equinox, the day when the sun crosses the equator from north to south, officially bringing us longer nights and shorter days. On the equinox, as the name implies, the length of our day and night is nearly equal. The equinox marks the official first day of fall. The harvest moon, the full moon closest to the autumnal equinox, will be gracing the night skies tomorrow, September 23rd. Historically, the light from the full moon at this time of year gave farmers extra time in the fields to gather their harvest; crops such as corn, squash, pumpkins, and beans are ready for gathering.
As students of phenology, our Audubon Naturalist in the Schools classes have been observing the changes in the seasons during recent visits to the Center. In the mornings we have discovered the grass wet with dew. This is a result of colder night temperatures; cold air cannot hold as much moisture as warm air. As the temperature drops over night, the water condenses and is deposited on the ground as dew.
We have also observed the yellowing of the cottonwood leaves and the reddish hue that many of the local shrubs such as wood's rose and golden current have acquired. This change in leaf color is triggered by the shortening of the days. Chlorophyll gives leaves their green color in summer, and is essential for photosynthesis, the chemical reaction that enables plants to produce their own food using the energy of the sun to convert carbon dioxide and water into sugars. The chlorophyll masks other pigments that are also present in the leaves. As the length of the night increases in autumn, chlorophyll production slows down and then stops, and eventually all the chlorophyll is destroyed. This reveals the yellow, orange, and red pigments that paint the landscape in such beautiful hues during autumn.
Many changes are taking place in nature during this truly spectacular time of year. Animals are preparing for the colder months to come by caching (storing) food, putting on extra fat reserves, and by migrating away to warmer climes. We have heard numerous flocks of geese overhead during the past few weeks, and the students have observed that it is quieter in the woods lately; many bird species have already left for the south. Keep your eyes, ears, and nose tuned to nature, and share your phenological observations here.