July 14, 2016
My spouse said, “What’s that noise? Is it rain?”
It was a fair question. If you didn’t know, the Northeastern US is experiencing a drought. It isn’t severe as what the west is experiencing, but, for a single year and in at least one place, it is reaching a record “level” [deficit]. Fifty years after the worst drought in the Northeastern US since quality data was being recorded, we are experiencing summer.
A couple of colleagues have independently said that I seem a bit too excited about the drought and its ecological impacts, of which there are a few pieces of ecological evidence so far. As someone who has never experienced a serious drought in their adult life, and only studied it from the rings of trees, I am excited to see one play out in the forest. For the farmers or their farms and orchards? No, not too happy for them. They have a challenging profession. But, one colleague has joined in the fun, sending me updates of a streamflow gauge in western Massachusetts. With a second colleague, we share radar images of storms and report to each other if it has rained.
Let’s first talk about the rain.
It has been pretty phenomenal tracking the precipitation forecasts, the radar as the storms pass, and what we actually experience. This year, the rain always seems about 5 days away and often does not get closer. When it does get closer, the chance of rain is often dropped like it did this week:
July 13, 2016 forecast – see July 14 forecast; note next day of rain 6 days away.
July 14, 2016 forecast – see how the chance of rain dropped for the 14th and the chance dropped slightly for the 19th? That is our summer so far.
Alternatively, we will get some distant rumblings and not much else, like we did last week in Keene Valley, NY (distant thunder clap followed by 10 drops of rain and then Sun) or a couple weeks ago in Sudbury, MA (wild, tall, dark clouds to the south moving our way dropping about 17 drops of rain:
Dynamic Clouds over Puffer Pond that released 17 drops of rain, July 1, 2016.
Or, several days like this morning when the rain arrives, we get a nice, 15 minute spritzing that wets part of the road:
Spritzed Street, July 14, 2016
Your experiences may vary, but the drought maps, streamflow gauges, and plants say it is dry, either severely so or streamflow that for the last two days in western Mass has been the lowest level in 100 years, lower than in 1966.
Wachusett Mountain, June 27, 2016
The evidence of drought on plants so far is nothing too dramatic. Understory herbs and shrubs are showing signs of wilt or autumnal color on thin soils [above]. This week I noticed paper birches along Route 2 in central Mass with yellow leaves. And, the tulip-poplar (Liriodendron tulipifera) at the end of my street is starting to create yellow leaves. Signs of autumn means that a plant’s ability to retain all of its foliage is being compromised. They are stressed and, in some ways, combating that stress.
The rest of the forest is still amazingly green. Maybe green is too strong of a word. It seems like two years or more of drought leads to increased mortality (Berdanier and Clark, 2016). That is, a single year [and so far half of the growing season] stresses trees, but does not put them over the edge. Further, many trees up here have determinate growth. Trees with determinate are primarily living off of their “efforts” and the climate of last year [and a bit beyond]. It has been dry here since the heavy snows of 2015, but this year is a significant drought. Last June, for example, was wet [more below]. So, for example, the maple in front of Shaler Hall has long leaders, full foliage, and quite green.
So far, it has been fun to see central Mass be the Bermuda Triangle of Rain and Clouds – they get gobbled up if they dare pass over our dear commonwealth.
— Dave Epstein (@growingwisdom) July 14, 2016
Now, rain, insects, disease, and leaf dynamics, The Good, The Bad, The Ugly.
I’ve already blogged about the pine needle disease that cropped up this year in central MA. One of the triggers of the browning and early shedding of white pine needles is above average May, June, or July rain in the prior year. June 2015 was wet. Thus the trigger of what looks like declining pine trees was rain. So, the good news of this year’s drought? If the pines can shrug off the needle disease complex, this year’s drought will allow them a “normal” needle year next year. I think I heard the pines saying, “Buck up. Next year ought to be better.”
Of course, the downside of this year’s drought – besides the fact that if plants do not get much water they do not grow so well – is that the drought is a factor of this year’s gypsy moth defoliation of trees in eastern Mass.
It was interesting. Early in the Summer of 2015, my Google Alert was picking up signs of a gypsy moth outbreak. Then, it stopped. Then, the alert picked up an article that indicated that the rains of June “killed off” the outbreak.
This year, after a brilliantly green spring, groups of oaks and other trees along 495 here in MA were suddenly leafless. Over the next week I and others at the Harvard Forest witnessed it near my house, northeast of Boston, and on the way to the Cape. It looked like this:
Defoliated oaks in eastern Mass, July 2016. Note the shadows of trees cast on the road, like roads in the winter. Photos [thankfully] by my better half while I drove.
I reached out to UMASS Extension to see if what we were seeing was gypsy moth. Tawny Simisky confirmed that it likely was and that eastern Mass was experiencing a decent outbreak. She also indicated that “the fungus, Entomophaga maimaiga, which kills gypsy moth caterpillars, does much better when it is wet,” further confirming the climate-leaf dynamics in Connecticut of 2015.
So, what we’ve learned so far is that last year’s wet June contributed to some leafless pines and this year’s drought has contributed to some leafless hardwoods. These are the strikes and gutters in ecology. The dynamics. Honestly, I can hardly wait to see how the rest of this year and next year play out.