Tuesday, September 30, 2014

Make your own Solar Calendar

I've long been interested, in a general way, in the movements of the sun through the seasons.  The sun reaches its highest point each day at "solar noon."  And this high point gets higher and higher in the sky each winter and spring until it reaches its highest point at the summer solstice (usually June 21-22), then descends gradually towards its lowest point at the winter solstice around December 21-22. 

Since the sun's axis is tilted 23½ degrees, here in Massachusetts (latitude 42 degrees) the sun reaches a high of 71½ degrees above the horizon at the beginning of summer, but only 24½ degrees at the beginning of winter.  At the equinoxes (beginning of spring or fall), the noonday sun would be at 90-42=48 degrees. 
Along with this comes the lengthening and then shortening of the daylight hours.  The solstices, and the equinoxes midway between them, provide the defined beginnings of the four seasons; while the daylengths, together with the changing angle of the noonday sun, give our hemisphere more or less solar heat energy, providing us our seasonal weather.

There are lots of solar calendars in the world.  This is one of the better-known ones.

Ancient solar calendars like Stonehenge give these movements of the sun a mystical air that excites many people into spiritual experiences.  I used to impute to these New Age types a longing for intense spirituality that they never found in the staid worship of their parents, and which traditional worship they'd rebelled from anyway.  Such stuff.  At the same time, I felt condescension toward those ancients who worshiped thus.

But in the second episode of the new Cosmos,Neill Degrasse Tyson explained it in a way that made perfect sense to me.  Ancient people depended for their survival on knowing the time of year when prey animals migrated and food plants came into season, and, with the advent of agriculture, even more the dates when the killing frost would be safely past.  These calendars were intensely practical--even crucial to their survival.  And the idea that the stars governed their fates an entirely logical extension of the same practical experience.

For my part, my interest is also sometimes just as practical: my little vegetable garden is strategically placed for the longest full sun in late spring and early summer.   My tomatoes, cucumbers, zucchini, sage and rosemary enjoy over five hours of full sun at the summer solstice, but now at the autumnal equinox (September 23) receive less than four hours, since much of the day high trees block the lowering sun.  Lover of tomato sandwiches (on toast with mayo, salt & pepper, and a liberal sprinkling of dill weed) that I am, I check the times of sun and shadow whenever the sky is clear and I am home at the right moments.  (I count about two more tomato sandwich lunches for my wife and I from the last tomatoes that will ripen before the light fails.)

A few weeks ago I finally decided to act on the impulse to make a solar calendar of my own.  Such an enterprise takes a fair amount of thinking.  What to observe?  Several things change through the seasons: the greatest height of the sun, the times of sunrise and sunset, and the direction of sunrise and sunset.  (The sun rises directly east and sets directly west only on the equinoxes; toward summer it rises and sets northerly, and towards winter it rises and sets more southerly.)  Even the time of local noon varies through the year for a combination of reasons.  

I first thought to try to fix the direction of sunrise and sunset at the solstices and equinoxes, but the trees of my neighborhood make that impossible even from an upstairs window.  In fact, there is not a single broad, straight, east-west street I could use to even approach witnessing sunrise or sunset at the equinoxes.  Next I thought of a straight, vertical rod to made a gnomon for a sort of seasonal sundial.  I like the idea of having a sundial or calendar large enough that you can actually watch the motion of the shadow in real time.  The trouble is, the taller the gnomon, the less distinct its shadow.  (I once had my 7th grade science classes make a sundial using the school's flagpole for the gnomon; it was less than satisfactory, since the top of the flagpole made almost no shadow at all.)  I still think the idea of a moderate-sized gnomon a good one, but it would take a yard with a lot of open sky, and any simple pole would very easily go out of adjustment and become useless.

I also failed miserably at finding local noon experimentally: theoretically, it is the time that the sun is highest in the sky, and therefore casts the shortest shadow on a level surface, but in practice the shadow is too indistinct to measure and the differences in its length too slight.  If I had a clear horizon, and had a sextant and were good at using it, I could probably nail the time of solar noon to less than a minute (this is routine in traditional navigation aboard ship), but I have none of these.  Fortunately, NOAA's solar calculator comes to the rescue.

Last weekend I hit on the perfect plan for a practical solar calendar of my own: looking around outdoors near solar noon, I found a place where the edge of a gutter cast a pretty reasonable shadow on the side of the house a little distance away.  I waited with ruler and Sharpie in hand until it was exactly solar noon, and marked the fuzzy shadow as best I could on the siding.  If I make marks regularly--especially at the solstices and equinoxes--I will be able at a glance to know two things: first, whether it is before or after solar noon on that particular day; second, where we are in the march of seasons.  Since the shadow falls about six feet  up the wall, there will be plenty of room for the shadow to go higher (as the noonday sun drops towards the winter solstice), and lower (sun rising towards summer solstice).  It should work perfectly--at least as long as the gutters don't go out of alignment.  --and as long as my long-suffering wife doesn't object too strenuously to Sharpie on the white siding!

Gnomon: the corner of the gutter.  It's shadow falls at noon on the side of another part of the house.
  The red mark is labeled "AE +4," i.e. Autumnal Equinox +4 days.  (Not exactly Stonehenge, but it's mine!)

Saturday, September 27, 2014

Last Saturday of the Summer on Nippenicket

I'd wanted to go paddling the past several weekends, but wind dissuaded me.  I don't mind a little wind in the course of getting places, but I wanted a relaxing paddle, camera in hand, stopping to drift from time to time.  I was also leery of the pond level: it has been so dry for so long.  I can't imagine risking a jetski in such skinny water--you'd be at high risk of damaging something.  (Not that that wouldn't be without compensations for the rest of us.)  As it is, when I paddled into the pond last Saturday, I came across shoal water where by rights no shoal water should be.  (On one low spit I counted 92 Canada geese and few mallards.)

I did not go far, nor stay out even two hours, but I did get to explore a tiny island I'd never dared land on before: when the pond is higher, the island looks like muddy swamp with emergent vegetation, where every step would sink you at least ankle-deep.  But now it was plain that most of the bottom thereabouts was sand or cobbles, so I eagerly set out to explore the little place end to end, and all the way around.

Island ahead.  Nifty clouds above.  (Why do the clouds do that?)

Musketaquid, my skin-on-frame kayak.

First surprise ashore, among the grounded white waterlily leaves, was this tiny flower with no apparent leaves.  That was a puzzle: how would it absorb light?  My Newcomb's Wildflower Guide keyed it out as a familiar bladderwort--normally a floating plant, but now stranded by dropping water-level with its tiny leaves probably half-buried in the mud.  (Bladderwort has it's own surprises: it is actively insectivorous, capturing swimming critters in tiny traps.)

I thought this an odd place to find so majestic a forest tree as white ash.  
But, just like we don't choose relatives, a tree doesn't choose its landing place.

 Most of the island's trees are tupelo.  I haven't seen a tupelo (Nyssa sylvatica), aka sweetgum,
in years, so it was nice to get reacquainted.

 This vine is new to me.  Probably climbing hempweed, Mikania scandens.

Whole lotta turnin' goin' on: 
I'd thought the color I was seeing in the neighborhood was the result of drought, but here we have
 tupelo, royal fern, red maple, and water willow all in fall color, but with plenty of water.

One more surprise: I was Not Alone.  Look a bit like racoon tracks,
but not big enough, I think.  Whatever it was had to swim to get there.

A last look before leaving the island.


Tuesday, September 9, 2014

Mighty Oaks from Acorns Grow

Once every few days or week I log into Nature's Notebook (NN) to continue my contribution to citizen science.  NN is a long-term project of the National Phenology Network, in which ordinary citizens track seasonal changes in plants and animals nationwide, to provide data to scientists interested in, for example, the rate at which climate is changing, and how living things are adapting--or not.  Most of the half-dozen or so species I track in my neighborhood are trees, and big trees, at that.  So I am mildly frustrated to come to the following questions on the data sheet: Do you see pollen release?  Do you see fruits?  Do you see ripe fruits?  The fact is I seldom see any of these, mainly because they are too too far away up in the tree's canopy.

A thunderstorm last night finally wetted the dusty ground here and might perk up the wilted leaves for a day, but it had another helpful side effect: it knocked down a few twigs from a majestic but inaccessible red oak on the other side of my block. Finally I got a look at something I seldom see: baby acorns.  

Branchlet of red oak (Quercus rubra).  The developing acorns are invisibly small here, 
but you can make them out in the photo below.

Here are three or four acorns in the axils of the leaves, while buds (for comparison) are at the tip of the twig.

When I first saw these on a fallen twig a few weeks ago, I first thought they were deformed buds.  I had to stare at them awhile and finally decided they must be acorns. 

 The previous photo, cropped.  At the tip of each acorn, you can just make out 
the three curly stigmas left over from the female oak flower.

The acorns are curiously small so late in the season, until you realize they will not finish maturing until next summer.  

Red oak belongs to the group of oaks that takes two years to mature its acorns.  Called the "red oak group," these oaks have leaves with pointed, bristle-tipped lobes.  Around here, they include scarlet oaks and black oaks as well as red.  

Scarlet oak (Quercus coccinea).  Another tree, pin oak, has similar leaves 
("more hole than leaf"), but lives in wetlands.

Black oak (Quercus velutina) has a leaf with fewer and broader lobes than red oak,
and is less deeply-cut than scarlet oak.

The acorns of red oak are broad faces wearing berets.  
The acorns of the red oak group mature the second year, so these came from last year's flowers.

Acorns of white oak have thinner faces wearing  knit caps.  They mature the same year, and are sweeter and more readily edible than acorns of red oak, etc. 

Saturday, September 6, 2014

Dry, Dry, Dry

Even the woods are suffering.

The ground has been dust for a month, except for the rare shower that just wet the surface to taunt the trees.  Although the vegetable garden is sensitive to even two weeks without rain, it's a little unusual to see wild plants wilt.  Ordinarily, plants wilt only in the heat of direct sun, recovering in the shade.  But this morning many plants--herbs, and even shrubs--were wilted before the sun had risen on them.  They were not able to recover even overnight.  Around the neighborhood, some sugar maple trees have been turning prematurely, and white oaks and white ashes have been losing a lot of leaves still green. 

 Heart-leaved aster.

Gray dogwood makes most of the shrub layer in my tiny wood.
It is really hurting.

The foxgrapes are ripe and smell good, but the leaves are wilted.

People are often clueless.  I am often greeted with "isn't this great weather!" and the like.  With lowering brows I mutter about the cries of distress from plants, dampening people's moods if not the ground. 

Last legs: little more than half the plants still alive, and most of those failing.
We may get a few more tomatoes, but I try not to set my heart on it..

I can't exactly blame the drought for the condition of our little vegetable garden: we have rain barrels under some of the downspouts, and even a brief shower will give us a few dozen gallons for watering.  And to keep the tomatoes coming (LOVE tomato sandwiches and salads) we have several times resorted to watering from the mains.  I have been watering at least once--and often two two or three times--a week.  No: my brown thumb is more likely to blame for the state of the garden.

But the trees in particular have me worried.  I went through near panic a week ago at the leaf loss by our majestic seventy-foot white ash--perhaps our best tree.  I was half-convinced it was under attack by the Emerald Ash Borer.  This alien invasive insect, introduced in Michigan and spreading nearly nationwide, threatens ash trees everywhere--it is considered the most destructive insect pest in the country right now.  It was first reported in western Massachusetts two years ago and is bearing down on eastern Mass.  Only the fact that a number of ash trees in the neighborhood began losing leaves almost simultaneously finally convinced me that drought was to blame, and that we had a little longer to wait for the insect onslaught.

The big ash is losing green leaves, but more are dying in the crown.
This was more than a week ago.

 By the way, you can't trust the weather records on rainfall--especially when it comes to the highly-local showers and thunderstorms of summer.  The same town can be have flooding at one end and be barely wetted at the other.  Instead I have a couple of straight-sided, flat-bottomed coffee mugs around the garden.  At least two or three is wise, so you can catch local variation, the effects of trees and buildings and wind.

As I look back at my journal, I see we had about two-and-a-half inches of rain back on July 4, and then about 3/4 inch on July 16 and another 3/4 on about August 16.*  There has been nothing over an eighth of an inch every couple of weeks since then, and no very substantial rain in over two months.*  *Edit. (Oops--forgot the 3/4 in mid-Aug.)

It's worth mentioning that plants are adapted to water stress: if the water pressure in a leaf drops, special openings called stomata close, reducing further water loss.   A plant with closed stomata is "holding its breath," since it cannot do photosynthesis very well if CO2 and O2 can't get in and out.  But wilt shows that a plant has lost water in spite of having closed stomata--it is a sign of more prolonged stress.

As I write this, we are sorta promised  showers and thundershowers late this afternoon.  I've heard that too many times before to take it too seriously, but maybe if I go walk the dogs on the pond shore that will attract rain...   

Gotta go see.

My son walks the dogs where there once was water.

The green algae coating tells you where the sand is still  at least damp.  
I have not seen the pond so low in the four or five years I've been watching it.

  PS: Walked at pond, watched sky clear, and heard storms were passing north of Boston (we are south).  On the other hand, I hear thunder now as 8pm nears.

PPS: We DID get some rain--a few minutes of downpour, anyway--and lots of lightning and thunder.  On impulse I grabbed camera and tripod and set them up facing a patch of open sky.  I hit the video button, then ran for the house, getting in the back door just at the biggest flash and most ear-splitting crack.  I vowed not to make fun of my wife's fear of lightning ever again.  The rain stopped in maybe ten minutes, and thunder died to a distant grumble in maybe ten minutes more.  Total in the gauge: only 1/4 inch.  At least the rain barrels got it.

The entire storm in 15 minutes.  (Most of the excitement is in the first few.)  The funny-looking thing that becomes visible in the middle foreground is my tiny cabin sailboat, Surprise.