Saturday, September 17, 2016

Drought Streamflow

A news report a couple of weeks ago said the Ipswich River in the northeast part of Mass was at its lowest level since records began, back in the 1930s.  Meanwhile, the Boston Globe yesterday reported that half of Massachusetts is now in extreme drought (an official designation--the second worst possible), and rainfall in the Boston area is 9.5 inches below normal for the year, and 18.5 inches below normal since January, 2015.  

I have been taking photos of a bit of Salisbury Brook here in Brockton every so often this year.  Here are photos early and late in the year.  


 February 2

late February

March 11

By chance, I took no photos for more than three months, not having planned a complete chronicle.


 July 29

 
 August 5

August 13

 August 29

 Sept 3

  September 17

Water still trickles among stones it once splashed over, but the flow is only perceptible if you stop and look awhile.
 
Of course, there is regular seasonal variation in streamflow, but around here it shouldn't be too extreme: rainfall is typically pretty even throughout.  Here is a climate diagram for nearby Taunton to contrast with the current drought.  Climate diagrams* show average monthly rainfall (thicker line, millimeter scale on right) and temperature (thinner line, Celsius temperatures on left) throughout the year (tic marks at bottom).  The scales are made to line up so that when the two lines cross ("temperature higher than rainfall"), water evaporates more quickly than it is replaced by rain--producing dry conditions.  As you can see, that rarely happens around here--even though rainfall dips in summer.


*Climate Diagram World Atlas

Saturday, September 3, 2016

Chestnut

I came across this little  tan leaved branch on a trail near Ponkapoag Pond, Blue Hill Reservation.  The dead, dried leaves mark it as an American chestnut (Castanea dentata).  If you walk these trails you will meet them often; always small, they are remnants of the great chestnuts of old. 

Until a century ago, American Chestnut was a major--sometimes dominant--tree of eastern forests, reaching three feet in diameter and a hundred feet in height.  In about 1904 a new fungal disease--probably imported on Asiatic chestnut trees--appeared on American chestnuts in the New York Zoological Park, infecting and killing trees and spreading like wildfire.  Today the tree is all but extinct in its natural range, existing only as stump sprouts that the fungus kills back regularly.

The tree I saw may have died of the severe drought; it is too small to be targeted by the fungus--certainly something killed it in mid-season.  The little thing had sprouted from the base of a somewhat-larger tree (upright near center), likely killed three or four years ago by chestnut blight.

When chestnut trunks reach two or three inches in diameter the fungus enters through cracks in the bark.  The fungus girdles the trunk before creating the orange sporangia on the bark that spread the spores that reproduce it.  The trunk dies but the roots often survive to send up another sprout, however these sprouts almost never become mature enough to flower and set seed.  In a cruel irony, by hanging on these trees maintain the fungus population.  But even if the chestnuts died for good, red oak is able to host the fungus without suffering serious harm; we will likely never be rid of it. 

So these "ghost trees" have existed for a century in a sort of limbo, not completely dead nor entirely alive.  The rotted stump at the base (below) must have been dead about a century: it could not have reached that diameter after the fungus arrived in the area.  Now, after a hundred years of stubbornness, this tree might finally be dead.*  

Efforts to breed resistant trees have been underway for decades; perhaps newer recombinant DNA technology will finally bring the tree back.


  Chestnut blight fungus (Cryphonectria parasitica aka Endothia parasitica) has almost entirely wiped out mature chestnuts from their natural range.  Only stump sprouts remain.

*Or have I just noticed in the photo a new sprout with a couple of long, dark green, saw-toothed chestnut leaves between stump and shoots?

Tuesday, August 30, 2016

Tamarack



Most needles gone by late November.

 New needles just poke from buds in late March.


Needles a centimeter long in mid-May.


 Full-grown needles and pollen cones at the end of May.

I used to frequent the local Veterans Administration grounds, where kind authorities welcomed the town's youth soccer league to their lawns.  Since my kids have aged out, and since it's not on any of my neighborhood walking routes, I seldom visit these days.  But when I do, its for only one thing: tamaracks.  

Tamarack, aka larch (Larix laricina), is not technically a native, since its real home is the great boreal forest of the far north.  This gangly, awkward-looking tree is a prince in frog's skin: an important species in the coniferous forest of Canada as far north as trees grow at all--the edge of the arctic tundra.  The genus Larix is circumboreal, its eleven species occurring in northern Europe and Asia as well as North America.  Our well-grown Brockton VA tamaracks were planted, but as forest royalty in their own place, they have my respect.  

Larch is the more unusual in being deciduous--one of a small group of conifers whose soft needles turn yellow and drop in the fall just as most broad-leaves do.  I visit to watch this seasonal play, the yellowing and dropping of needles, the new suit of fresh green in late spring, and the little cones that follow.

Since I hadn't been by in over a month, I took a different highway exit home than usual so I could pay my respects.  

I was shocked to find every single tree gone.  A neat bare circle of earth marked the place each had stood.  New fence posts hinted at one likely reason they were gone, though I don't know what prompted the fence.  I stood still at the nearest circle, as at a freshly-covered grave, before bending down in a forlorn hope of finding something.  Tattered cones met my fingers, and I carefully collected three, thinking there might be a few seeds remaining, and perhaps one or two that would germinate.  

Of course, these had been mature trees that had borne cones many times, and as my eyes wandered aimless in the little wood adjacent I saw several older teenager tamaracks standing there, hands in pockets, graveyard-whistling a little and hoping not to be noticed by the humans that had taking their parents.  

The sight of these gave me hope.  Some bore cones of their own, so that if the seeds I found today don't germinate, fresher ones might.  They, too, would undoubtedly meet the chainsaw someday--all things die--but I hoped not til they had grown to be as old as their parents, and not til they had their own strapping youngsters established in some safely-neglected bit of woods.  

 All that remains of the tree photographed at top.


 Youngsters know they will live forever.