Archive for the ‘trees’ Category
deciduous and evergreen: pourquoi?
star magnolia (Magnolia stellata) – I think. Thank you, internet
It’s now more or less officially spring, and leafless trees are blossoming, like the one across the lane from my new home, as pictured. So I’m wondering how they have the energy, and more broadly, why do some trees lose their leaves seasonally, and others not? I’m no expert on trees, and I hope, before this piece is finished, to identify this one, but at least I know it’s deciduous, I think.
I also want to know how this deciduous and evergreen dichotomy relates to photosynthesis, as surely it does. So, of course, I must look it up. Surprisingly, Oliver Morton’s Eating the Sun makes no mention of the evergreen-deciduous thing, but then I likely wouldn’t comprehend his explanation…
But here’s a photosynthesis formula that I can more or less comprehend:
6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂
Which can be roughly translated as: six lots of carbon dioxide (from the air) plus an equivalent lot of water (from the soil), plus solar energy, makes glucose, and starch. The starch, the carbohydrate, is stored in the roots, trunk and branches. Deciduous trees shed their leaves in autumn, and enter a period of dormancy – reduced metabolism, which slows or stops growth. Presumably energy is expended, though, in the production of blossoms. It’s a risk worth taking, however, because blossoms exposed to the open air can be seen and more easily approached by pollinators and can have their seeds blown by the wind.
I’m guessing that evergreen trees are mostly located in dense forests, which tend to create their own microclimates, less susceptible to seasonal change. And they’re more of a thing in the tropics, where the weather’s always – tropical, more or less. And the leaves of evergreens tend to be thicker and spinier. Ms AI tells me this:
Evergreen tree leaves—whether needle-like or broad—are uniquely adapted with thick, waxy outer layers and robust cellular structures that minimise water loss and resist freezing. Instead of shedding all foliage at once, these trees retain functional, chlorophyll-containing leaves year-round, slowly replacing them individually over several seasons.
I’m hopelessly ignorant about tree and plant types but I’ve found a website that will freely inform me (or try to) of the identity of any tree or plant I present to them via a photo I’ve taken. Instant learning! I’m quite excited.
Apparently some individual tree leaves can live for over twenty years, and these leaves ‘tend to be tougher and thicker, and more expensive to build’, according to a Macquarrie Uni article, referenced below. Other interesting facts are that ‘conifers and other evergreen trees make longer-living leaves the closer they are to the poles’, and ‘deciduous trees do the opposite. Their longest-lasting leaves are found at the tropics’. It’s all about maximising carbon absorption. If you’re an evergreen conifer in poor soil and facing a long harsh winter you’ll need to make a long-term investment in your leaves, but if you’re a deciduous maple you’re best to create new leaves quick-smart that will capture the summer sunlight before dropping in autumn, and that means investing in fast-growing, cheap but flimsy leaves. I’m more or less paraphrasing here.
So I’ll make this piece a short one, but I’ll be taking more photos in the neighbourhood and trying to learn more about blossoms and soil and climate and photosynthesis for future posts and my own delectation. I’m feeling Spring in my step!
References
A Tree Blooms Without Photosynthesis (Leaves)? The Science Behind Spring Blossoms