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Fall out

 

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Last rays back-lighting a vigilant osprey, the solar orb settles quickly: autumnal equinox marks (among other seasonal evolutions) the south-fleeing sun’s most rapid decline. So while thermal hysteresis—”seasonal lag”—delays the steepest drop in temperature, day-length dwindles apace. This time around, an over-wrought summer broke suddenly, disappointing delinquent beachgoers but relieving students in un-air-conditioned classrooms. For gardeners, naturalists and nature, however, a brutal drought persists.

Mean precipitation here approximates to four inches per month, varying only 10~20% throughout the year. But rainfall since the end of last winter has fallen far short of that: between a quarter and a third of normal, depending on which personal or official tabulations are credited. (Many of the most productive storms blew by just a few miles north or south of Farrar Pond, or petered out slightly west of here, so weather stations in Bedford and elsewhere have over-reported for this location. In addition, many light rainfalls indicated by weather radar evaporated on their way earthward, never even moistening the ground.)

This is not (yet) the worst persistent drought on record; that happened here in the mid-1960s. (By way of New England contrasts, it was punctuated by a severe flood in March of 1968, with extreme rainfall adding to and accelerating snow-melt. The Sudbury River overflowed not only the Farrar Pond dam, which often occurs in spring, but also the stretch of South Great Road whose elevation helped to create the pond in the first place. From Beaver Brook to well past Nashawtuc, all was awash for several days, with just the top of Lee’s Bridge visible. Sherman Bridge having earlier submerged, classes at LSRHS had to be canceled.) The present drought is somewhat more localized, and has also not yet depleted reservoirs of waters sequestered in and under the earth. With broad marshes and high hills upstream, Farrar Pond remains a pond. But plant life around it, the various creatures dependent on that vegetation, and in less critical degree the people who enjoy cultivated and natural landscapes around the pond are all suffering.

Though specifics vary widely, the loamy sand/sandy loam/silt loam glacial outwash topsoils hereabouts can hold about 1-2″ of water per foot of depth. (More than that quickly leaks out through porous sand and bank-gravel subsoils.) Organic-rich duff and humus layers may, like sponges, retain much more. But when all is been extracted by evaporation, percolation, and consumption by plants and fungi, it can be difficult to get water back down to where it is needed. Whatever dirt, leaves, etc. lie at the surface will quickly be rendered hydrophobic—water repellent—by terpenes and other oily drippings and vapors from trees and shrubs. Then whatever water does makes it down through the leafy canopy may largely run right off. (Lighter rainfalls may never penetrate at all, and be largely lost to evaporation.) This “glazing” problem becomes yet more serious when duff is blown or raked away by overzealous or ignorant landscapers. Bare ground under rhododendrons, for example, ensures needless plant damage when rains are infrequent. A puzzler: why do people who dislike brush and leaf move to a town so heavily forested and conserved?

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This foot-deep test pit was dug one day after a recent 1.2″ rainfall. Top to bottom, the soil is powdery-dry, the duff layer like tinder except for a hint of damp in the zone just below the covering leaves. (Note slightly darker areas in photo.) Per the mean-precipitation figure cited above, this condition reflects a deficit of perhaps 16″ of rainwater in the past few months.

How do plants survive? Some don’t. Many annuals and tender perennials in sunny locations have been killed outright. Since some losses occurred before seed production, there may be a noticeable change in both absolute and relative wildflower abundances next year. Worse, some of the most aggressive invasives—mugwort, e.g.—are well-adapted to this challenge, and will gain ground at the expense of more desirable native species.

Trees like pines that lack sophisticated vascular systems are less able to support themselves with what water they can find, and may sacrifice branches to survive. Some vines, like Oriental bittersweet (bad) and  trumpetvine (good, mostly)

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root both deeply and broadly, and are flowering and fruiting without apparent handicap. Rooted broadly if not so deeply, a hard-wooded sixty-year-old rhododendron shrugs off most such vicissitudes, signaling defiance with a late re-bloom:

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Smooth sumac ripens apace, decorated (or defaced) by characteristic galls,

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and the small native persimmon droops with sweetening promise:

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Others fare less well. Some seed-cones of this native cucumber magnolia have prematurely dried, split and offered unready berries to hungry birds and squirrels,

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while elsewhere on the same tree, predators could not wait for peak nutritional value:

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By contrast, whatever attacked this (likewise native) bigleaf magnolia apparently did not find the fruit to its liking:

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This moonlit hydrangea,

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previously an object of affection and sometimes even awe, would normally be showing off moist, fluffy pom-poms up to a foot long. This year, less than half that, and crinkled brown two months before their time. Older  and better-rooted,  native dogwood in background is doing much better.

Brown may be the operative color this fall. Brown dirt showing through except where lawn sprinklers run full-bore. Brown vegetation dead or gone dormant. And brown foliage: even if heavy rains come soon, some of our most palette-enriching trees and shrubs have taken the protective step of choking off leaves early to conserve water. Many have already shed heavily, the fallen adorning the floating:

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Deeply shaded, a sycamore was able to stage a relatively graceful exit:

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Note the bit of residual green. When leaves are shed prematurely, the parent plant forgoes the progressive withdrawal of various valuable materials—minerals, nutrients, complex compounds like chlorophyll—whose sequencing gives rise to the renowned play of color. This maple, in full sun, was less fortunate:

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Unable to maintain turgor pressure and osmotic lift, the highest reaches are sacrificed in favor of lower (and shaded) branches. And where brown is the color of gentle decay, black signals sudden death due to collapse of a local vascular branch, or in some cases insect attack invited by weakened defenses.

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For some species and specimens, it may take years to recoup such a loss.

Decay is growth, too, for the agents thereof. The birch bracket (or “razor strop”) fungus is a common sight in these woods, especially as birches are fast-growing, short-lived and—with their canoe-tough bark—leave persistent carcasses. This example, extruded last year, was apparently used recently as a picnic table by a squirrel with its black walnut:

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This year’s crop has not been so successful. That same rain triggered the efflorescence of fruiting bodies from numerous dead trees here. But in most cases, continuing drought nipped them in bud

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like gum bubbles frozen in mid-blow:

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This incomplete effort will never ripen to release the spores of new life: for the mycelial structure that is the main body of the fungus, a dead waste of energy and chitin.

Such sudden desiccation, or perhaps the inclement brevity of temporary reprieves from same, has other victims. This ill-starred (green?) frog

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was found as shown on egg-frying noonday pavement. Absent any obvious injury, the presumptive cause of death could be simple overheating, skin dehydration (equivalent to lung obstruction for a mammal), or perhaps both. RIP, and may better fortune embrace other refugees in their quest for safe haven.

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Prudent poikilotherms stay closer to relief, like these dwellers in, under the eaves of and beneath shading grasses around one small pond:

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With their presence, crickets are largely absent from around said pool, and where tadpoles lately teemed

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(the blurry background is an algae-tinted mass of thousands of hatched eggs), now only a few sharp-toothed and perhaps nasty-tasting bugs cruise beneath exceptionally late lily blossoms:

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(For a gustatory rather than aesthetic perspective on nymphaea, see this video.)

Arthropods often take well to dry conditions. For bumblebees and late-appearing (and very welcome) honeybees, goldenrod is a preferred feed in the run-up to winter:

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(Note pollen-laden panniers.) But bees do not make eco-ethical distinctions, and non-native buddleia is always a favorite.

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And often a last supper: frozen bumblebees on frosted buddleia is a November-morning commonplace here. Butterflies, too, favor their eponymous bush;

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tattered veterans in their final days largely disdain solidago when buddleia is available:

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These same bright, sweet and fragrant flower clusters attract smaller nectar-seekers, which in turn draw the persistent attention of a whole order (Odonata) of Jägermeisters:

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Some insects take more than the freely offered ichor of flowers. Katydids reappear annually in the giant bell of Hibiscus moscheutos, for some reason preferring the ‘Lady Baltimore’ cultivar:

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It will spend hours, apparently in rapt adoration of the calyx

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but possibly nibbling at the reddest bits:

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Whatever the sky delivers, the dance ever and always goes on,

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and each season and year, in its own way, sets the seed of the next.

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