Everything Affects Everything
When you see Herb Robert (Geranium robertianum) flowering and pussy willow buds opening in November, you know climate change is affecting life in your own back yard. How do late-blooming flowers in the fall as well as increasingly early flowering in the spring affect our ecosystem?
For one, think about the timing involved when it comes to pollination. Insects have synchronized their pollination activity to take place when their sources of pollen and nectar are available. Climate change may increase the chance of plants and pollinators becoming out of sync, with plants using up energy flowering in the fall after pollinators have disappeared, and flowering too early in the year for the insects that pollinate them. And then there are the migrating insect-eating songbirds whose return is coordinated with the presence of food on their breeding grounds…It really boils down to this: that all life is interrelated. We are all caught in an inescapable network of mutuality, tied into a single garment of destiny. Whatever affects one directly, affects us all indirectly. – Martin Luther King, Jr.
Pussy Willows Peeking Out
Nothing announces the arrival of spring more than willow flowers peeking their silver heads out of the bud scales which have surrounded and protected them all winter. What we call pussy willows are, in fact, the soft, silvery hairs that insulate the emerging spike of flowers, or catkin, within a willow flower bud. Pussy willows are dioecious, meaning there are both male plants and female plants. A male willow has only male catkins; female willows have only female catkins.
An individual willow catkin consists of all male or all female flowers. The first catkins to emerge in the spring are usually males. The hairs, or “pussies,” that emerge when willow buds first open trap the heat from the sun and help warm the center of the catkins, where the flowers’ reproductive parts are located. This trapped heat promotes the development of the pollen (or in female flowers, the ovules) of the flowers deep within the hairs. Eventually the reproductive parts of the willow flowers – the stamens and pistils – emerge, but until they do, we get to enjoy their silvery fur coats.
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White-tailed Deer Scent-Marking
Scent-marking plays an important communication role in the animal world. A variety of species use glandular secretions to convey (for some distance) messages. From beavers spreading castoreum on scent mounds to fishers leaving their scent every time their hind feet touch the ground, the woods are alive with messages often undetected by most humans. Some of these are left by White-tailed Deer, which have two primary scent-marking behaviors: antler rubbing and scrapes.
One used to associate an antler rub with the act of a buck removing drying velvet from its antlers. However, it turns out that very few rubs are made by deer removing antler velvet, a process that’s normally completed within 24 hours. Instead, most rubs are made by relatively few dominant bucks to signal their readiness to breed and to mark their territory.
All White-tailed Deer possess specialized forehead glands that become increasingly active in autumn, particularly in adult males. All bucks spread their scent by rubbing their foreheads (which contain specialized scent glands) against trees and shrubs that have smooth bark, few, if any, lower limbs and are ½” to 4” in diameter. (Older bucks also will rub trees six or more inches in diameter.) In the Northeast, Trembling Aspen, Staghorn Sumac, Red Maple, and willows are often used for this purpose.
Mature, socially high-ranking bucks exude greater amounts of the glandular secretion than do younger males or females. They begin marking their territory soon after losing velvet and continue marking until they cast their antlers in December or January. The chemical signals left at a rub site tend to suppress the aggressiveness and sex drive of young males. However, those same signals stimulate females. The amount of rubbing an individual buck does depends on the level of testosterone in his blood, which in turn is largely determined by the animal’s age and dominance status.
We may not be able to detect the chemicals on a rub, but it’s hard to miss the sight of the light-colored blazes that magically appear in the woods at this time of year. (Photo: White-tailed Deer rub on Staghorn Sumac. Thanks to Chiho Kaneko and Jeffrey Hamelman for photo op.)
Bigtooth Aspen Male Catkins
Aspens, cottonwoods, poplars – all are names for certain species of trees in the genus Populus. These trees, as well as birch, hickory, oak and willow trees, produce their flowers on spikes called catkins. Telling the catkins of these trees from one another is challenging, to say the least, yet some of NC’s readers correctly identified the catkins in the photograph as those of Bigtooth Aspen, Populus grandidentata. This tree blooms for one to two weeks in the spring and its mature male catkins open and extend to two to four inches in length. The wind, as opposed to insects, disperses the light, fluffy yellow pollen as the catkins dangle in the breeze. Some of the pollen remains intact even after the tree has shed its spent catkins onto the ground.
Because Bigtooth Aspen, and most species of Populus, are dioecious (male and female flowers develop on separate trees), there are only male flowers in this photo and beneath this tree. After fertilization, female flowers remain on the tree and form capsules which contain several small seeds embedded in tufts of fine, white hair. They will fill the air in several weeks looking like bits of floating cotton.
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More Buds
The previous “bud scale” post engaged readers to an extent that made me feel another post with additional buds to scrutinize would be welcome. Apologies to non-woody plant aficionados!
When identifying woody plants in winter, one takes advantage of everything a tree or shrub has to tell you: bud/branch arrangement (opposite/alternate), bark, silhouette and terminal buds. Buds are so revealing that they alone can immediately tell you what species you are seeking to identify. Is there one bud at the tip of each branch (willows) or multiple terminal buds (red oak)? Are there bud scales (no-witch hazel; yes- bigtooth aspen)? If so, what are their number (willows – one) and arrangement (overlapping, like shingles – red oak)? Are the buds red (striped maple), brown (witch hazel), yellow (bitternut hickory), green, or some combination of these colors? Are they pointed (bigtooth aspen) or rounded (willow)? Every species of tree has buds with a unique combination of these characteristics. Now is the time to observe them, as some will soon start to open.
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Pussy Willows Emerging
Even with sub-zero temperatures and feet of snow on the ground it is possible to find signs, such as pussy willows, that spring really is around the corner. What we call pussy willows are, in fact, the soft, silvery hairs that insulate the emerging spike of flowers, or catkin, within a willow flower bud. A willow catkin consists of all male or all female flowers. The first catkins to emerge in the spring are usually males. The hairs, or “pussies,” that emerge when willow buds first open trap the heat from the sun and help warm the center of the catkins, where the flowers’ reproductive parts are located. This trapped heat promotes the development of the pollen (or in female flowers, the ovules) of the flowers deep within the hairs. Eventually the reproductive parts of the willow flowers – the stamens and pistils – emerge, but until they do, we get to enjoy their silvery fur coats.
Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.
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