On a few small acres in the hill country of central Texas, we live by watching, feeling, and waiting. Together, we come to know by loving and love best when we care enough to understand. Our Loves: limestone, leaf-vein, scales, feathers, friends, and all their shifting reflections in the waters of a small Creek.
Here is a great comparison photo below. I never knew that snow-on-the-mountain changed the white edges of its leaves and bracts during the period when its flowers are developing. The first photo of two blog entries ago shows the plant as the first flowers were blooming, and the one below displays the full-bloom stage of the leaves. Such a change obviously augments any of the flower's attempts to draw the attention of pollinating insects.
What might be a carpenter bee (Xylocopa) on snow-on-the-mountain (Euphorbia marginata)
When things out at the Creek get just too hot for us to work at anything productive (we hit 112 degrees yesterday), we take to the purely useless. Like stone-balancing.
I really didn't think that the Creek would still be wet this deep into the hot drought, but water continues to seep up into the upper stretch of the stream, and if not exactly working a brisk flow, it at least is able to keep up enough of a presence to sustain the usual Creek life.
The Pond continues creeping northward, away from us, now at a distance of about seventy-five feet from the original water-meter. I don't know, but this comes to about an eight-inch step per day, and down about four or five feet in actual elevation fall.
(The water-meter stick is hidden in the dry grasses bottom left.)
Last Sunday morning, a few of us met at the Creek to haul off scrap metal, drink cold tea, or walk slowly along the remains of the stream.
A kind couple had approached me while I was working the ambulance a few days ago, and they asked if I had any work for them, cutting weeds, hauling off junk, etc. I told them to meet me at the Creek Sunday. So for half a day in the sweltering loveliness of a little canyon, the two of them loaded their pickup full of old metal filing cabinets, electric wire, broken grills, and defunct yard-art. I hope they were able to exchange it for a worthwhile sum.
Some of Harlin's photos from that Sunday morning. :
Sesbania herbacea
Switchgrass
Widow Skimmer (Libellula luctuosa)
[The male Widow Skimmer differs from the female in that he shows the broad white patches mid-wing, as seen here above. Dragon flies have been placed with the taxonomic order Odanata, a group of insects that lived during the Carboniferous period, a time when the rocks of this Creek property were forming and some 100 million years earlier than the dinosaurs.]
Some faces.
"Third Rail"
And more from the drought. The cedar elms of the county seem to be taking it the hardest. These from up on Whitman's Rough next to the road.
These luscious plants don't appear to have been affected by the drought except positively and in an ironic sense: they managed to have lived next to some helpless blackberry plants that require every-third-day watering by the sad gardener. If it weren't for the drought, there'd be little chance such a beautiful plant would be so tall and stout.
Imagine a continuous train of water molecules extending from the tips of root hairs all the way up a tree's internal system of hollow columns through the trunk, limbs, and twigs to the undersides of leaves where one after another molecule of water is allowed to evaporate from tiny openings called stomata. Interrupt this train at the leaf, and the whole train all the way down to the root hairs stops. When a tree battles for life during a drought, the odds of winning are greatly decreased if temperatures are high. So in these hot and dry times, the trees attempt to reduce the rate of water evaporation through transpiration by closing the pores in their leaves. But when they do this, they cannot bring in necessary carbon dioxide and end up dying a death of carbon starvation. It's the carbon dioxide that provides one of the necessary ingredients to photosynthesis. One recent report showed that drought-stricken trees (pinon pine trees, specifically in this study) died at a rate 28% faster if they were also subjected to temperatures 7 degrees higher than normal. Depending on the source, July in the Austin area averages a temperature of 84.3, but this July the average was about 5 degrees higher at 89.7 degrees. Beating the average by 5 degrees over the span of a month is a big deal. We set a heat record for the month of July. Combine that with the driest twelve-month period on record, and the stage is set for brown-out here on Whitman's Rough. The leaves wilt because of loss of turgor pressure in the leaf's blade and petiole, but they lose water from more than just the stomata pores on the underside of the leaves. It's probably safe to say that many of the trees up on the hillside have long since initiated stomatal control, so now they are losing water directly through the leaf surface, the twigs' lenticels, the stems, and the roots. Now we are to the point with some of the trees that if we were to receive rains from off a passing hurricane, many of the leaves' stomata will never open again, meaning that food production within the plant will be delayed or denied permanently. All the parts of the plant that contribute to its photosynthetic ability (chloroplasts, for example) may themselves be damaged and then take too long to recover before the tree dies of starvation. Tiny roots just beneath the ground surface die and then the plant couldn't suck up moisture if you poured barrels of water on it. As a thriving plant draws up moisture, it carries nutrients along with the water. So shutting off the water supply also shuts off the nutrient supply. Some trees shed their leaves in a last ditch effort to save the plant and will grow new, if somewhat stunted, leaves when the drought ends. Others lose the leaves and die. But even if they live, next year's growth will be retarded by this year's drought. Cambial growth slows when water supplies run low, and it's this year's cambial growth that helps set the limits of next year's growth potential.
Temperature sensitivity of drought-induced tree mortality portends increased regional die-off under global-change-type drought
Large-scale biogeographical shifts in vegetation are predicted in response to the altered precipitation and temperature regimes associated with global climate change. Vegetation shifts have profound ecological impacts and are an important climate-ecosystem feedback through their alteration of carbon, water, and energy exchanges of the land surface. Of particular concern is the potential for warmer temperatures to compound the effects of increasingly severe droughts by triggering widespread vegetation shifts via woody plant mortality. The sensitivity of tree mortality to temperature is dependent on which of 2 non-mutually-exclusive mechanisms predominates—temperature-sensitive carbon starvation in response to a period of protracted water stress or temperature-insensitive sudden hydraulic failure under extreme water stress (cavitation). Here we show that experimentally induced warmer temperatures (≈4 °C) shortened the time to drought-induced mortality in Pinus edulis (piñon shortened pine) trees by nearly a third, with temperature-dependent differences in cumulative respiration costs implicating carbon starvation as the primary mechanism of mortality. Extrapolating this temperature effect to the historic frequency of water deficit in the southwestern United States predicts a 5-fold increase in the frequency of regional-scale tree die-off events for this species due to temperature alone. Projected increases in drought frequency due to changes in precipitation and increases in stress from biotic agents (e.g., bark beetles) would further exacerbate mortality. Our results demonstrate the mechanism by which warmer temperatures have exacerbated recent regional die-off events and background mortality rates. Because of pervasive projected increases in temperature, our results portend widespread increases in the extent and frequency of vegetation die-off.
Fresh green cuttings of Celtis laevigata and Smilax about to be taken to
Mr. Lyda's starving sheep up the county road from the Creek
Filling up with water to haul up Whitman's Rough
in an effort to save a few cedar elms
Mr. Rollins' Hog Shed at this stage of the renovation
So, here we are at the top of Whitman's Rough in the morning, looking through some cedar elms and other trees dying in this Drought.
And here at the Cedar Elm Field just after you pass through the front gate. Again, the sign of Drought here is the tall grasses--spring 2010 grasses, that is. Last year we had lush rains to make grow tall grasses. But after they went dormant during the winter, they remained. None took their place.
And a view alongside the lower Boulders at the bottom of Whitman's Rough. I could stand and look for a long time at these massive stones formed in the warm waters of three hundred million years ago during the Pennsylvanian Epoch. The Boulders slide slowly downward within the fault of this small canyon, their gentle weight giving way to acidic rains, fern root, lichen, and the scratch of small claws in the night.
Here the limestone has given way to a trickle of water only a memory these days.
This has always been one of my favorite trees. The early settlers of this area used the wood of mature gum bumelias for making the handles of axes and such because of its fine strength. The children of these pioneers chewed the sap that oozed from cuts in the bark. People have called it Black Haw, Woolybucket, Chittamwood, False Buckthorn, Gum Bully, Gum Elastic, Gum Woolybucket, Woolybucket Bumelia, Wooly Buckthorn, Ironwood, and Coma.
Drying one's naked body by the wind is one of those things I'll miss when I'm dead. Last Sunday morning I hurried out to the Creek to get in a couple hours of concrete work, shoring up the flood-exposed northeast corner of the Hog Shed's slab. I finished four bags of concrete mix and had worked myself to a sweaty lather of salt, dirt, and cement lime. Afterwards, I showered under the Oak with a cool hose full of Pond water. My body dried by wind there in the dappled shade. Many, many things are good to me, but few that are much better than the feeling of drying skin up against a wind driven up a small canyon. The turkey vultures and black buzzards were at it again. I could hear them croaking up above the boulders on Whitman's Rough while I watched others flying about in front of me, over the Stone Field. I know they benefit by thermal updrafts created within this Canyon, but I still don't know why they find the place so attractive. I've never seen them feeding. I've never seen even the smallest bit of carrion lying about. But here they are, day after day, circling away and spending hours upon hours perched in the trees and on the boulders where they leave behind a surface painted white by their calcareous feces.
The creek still flows. About as much as a leaky faucet. The Creek's water begins a hundred or so yards south of the Pond, weakly bubbling up among thick-growing water willow, pennywort, rabbit's foot grass, and algae. From there, the Creek silently trickles from one small pool to the next, finally dripping into our main Pool. I love it, though. I love every smell, every dried skin of algae draping sun-bleached stones, every mud-crack beside the shrunken Pond and Creek. Like an aged lover, this thirsty little canyon remains as sweet to me as she was to me in our springtime. So, we are officially in the worst one-year drought the state of Texas has ever seen. This from College Station:
Preliminary reports from the National Climatic Data Center indicate that July 2011 was the warmest month ever recorded statewide for Texas, with data going back to 1895, Nielsen-Gammon reports [the Texas State Climatologist and professor of atmospheric sciences at Texas A&M University]. The average temperature of 87.2 degrees broke the previous record of 86.5 degrees set in 1998. The June average temperature of 85.2 was a record for that month and now ranks fifth warmest overall.
Rainfall totals were also unusually light across the state. The July monthly total of 0.72 inches ranks third driest, surpassed by the 0.69 inches recorded in both 1980 and 2000. This is the fifth consecutive month in which precipitation totals were among the 10 driest for that month, says the Texas A&M professor.
Among the other rainfall records set this month: least year-to-date precipitation (6.53 inches; historical average 16.03 inches; previous record 9.36 inches in 1917); driest consecutive 8, 9 and 10 months on record (7.25 inches 8.35 inches, and 9.17 inches respectively); and driest 12 months ending in July (15.16 inches, previous record 16.46 inches in 1925).
“These statistics rank the current drought as the most severe one-year drought ever for Texas,” Nielsen-Gammon explains. “Never before has so little rain been recorded prior to and during the primary growing season for crops, plants and warm-season grasses.”
Texas would need more than 4.5 inches of rain in the next two months to avoid breaking the 1956 record for driest 12 consecutive months, he adds. . . .
“The climate division that covers west-central Texas has received only 3.32 inches of rainfall since Nov.1,” says Nielsen-Gammon. “That’s less than 21 percent of the historical average and less than half of the previous record, set in 1956. Add in the record heat, and it’s just devastating.”
And now we heard yesterday that there's a fifty-fifty chance of a return to the La Nina weather phenomenon later in the year.
Below is a view from the south end of the Pond where our pathetic little water gauge that was originally sunk into five or so inches of water now stands a fair distance from the retreating waters. Last week we swam in the Pond, and it remains as refreshing as ever, actually. The deep Spring still chills the water up around the spot on the west side where limestone dips down steeply.
In the photo one can just make out another water gauge placed at the shore last Sunday morning. I extended the black plastic water pipe and electric cable another fifty feet since the submersible pump had ceased to be submersed. (For a comparison, see the pictures from last March.)
How a Pond Travels North with the Summer Drought
Here we show a lovely drought-yellow in a Chinaberry tree (Melia azedarach).
Such droughts are hard on some insects and beneficial to others. Mosquitoes and ants take it hard. And when dry conditions intensify, the antilions (Myrmeleon sp.) benefit to the extent that their inverted cones used as pit-fall traps become more effective.
Antlion ( Myrmeleon sp.) Traps Under The Oak
The antlion larvae begin construction of the pit by crawling backwards in a circle, lifting up the dry sand onto its back, then moving the sand to the top of its head with a front leg, where it finally flips away the sand with a series of quick snaps. Eventually the circling works downward, creating in the process a pit whose walls remain about as steep as is possible. This angle is referred to as the critical angle of repose, and for all granular materials such as rice, gravel, snow, ash, coffee beans, or sand, it's the steepest angle at which such things can be piled up. But it works in reverse as well. Some materials cave in or avalanche easier than others, depending on their density, the surface area of the individual pieces, and what's referred to as their coefficient of friction. Finely pulverized alluvial sands in a central Texas drought behave differently than spent coffee grounds or piled human bodies.
So when the pit is completed, the antlion buries itself at the bottom with its hollow-tubed jaws pointed upwards. Then when the sad prey--ants, beetles, spiders, or whatever--fall into the trap, they are often prevented from escaping because of the avalanche-prone walls of their new-found hell. Some will climb up and out to live another few short and miserable insect hours. The rest may make it half way up the slippery slope, only to come sliding back down while the antlion flips sand out of the bottom of the hole, thus weakening the walls of the cone. When the antlion is through sucking the innards out of the prey, it tosses the desiccated body back up. Because it is able to draw out the wet guts of the ant or the beetle, this wonderful creature doesn't need to sip water from a creek or rain puddle, so a record drought may mean good times for the antlion.
Myrmeleon (with 158 species)is the only genus of antlion in the United States that builds these sort of pit-fall traps. Somewhere around 2000 species of antlion inhabit this globe. Here in the South, they sometimes are called doodlebugs for their winding trails left in the sand as the larval form seeks out a place to design its famously inverted cone. It's the adult stage that flies about in the evenings, resembling our damsel and dragon flies. And most noteworthy as far as topics of meditation go, the antlion larvae lack an anus. For the duration of the larval stage the insect stores up its . . . metabolic waste, waiting for the end of the pupal stage to poop. Insects are interesting, but to our knowledge, the antlion is the only insect lacking an anus. Meditation time over.
In the eastern parts of Asia, this insect goes by the name of "ant demon" and its trap as "ant-hell." In Japanese, the word ari-jigoku (for the antlion's trap) also refers to a situation into which a person "falls" without hope of rescue. And yes, it's the Cherokee word for antlion that is yahoola. Below is a short scene involving a small beetle narrowly escaping the grasp of the antlion on the morning of August 4 under The Oak:
Antlion, its Trap, and How a Beetle Lived to See Another Day
But two turtles were not as fortunate as that beetle. These remains were found just upstream from the Pool and on the east side of the Creek.
I don't know what the odds are of finding two up-turned turtle carapaces within ten feet of one another, but the sight was a sad one. I crossed the Creek and sat for half an hour on the shady west bank just above them.
Below we have a unique plant among plants, the Sesbania herbacea, sometimes known as Hemp Sesbania, Bigpod Sesbania, Peaweed, Coffeeweed, Peatree, Danglepod, Colorado River hemp, or Indigo-weed. I think (it should go without too much parenthetical interruption that everything I identify out here at The Creek may turn out to be something of a different order). At first, I thought it might be another rattlebush (Sesbania drummondii) when it was young and still knee-high. But now it has quickly proven to be its own, reaching now at least head-height. The main stem is a glabrous green that will, I am told, completely die back next winter. The "hemp" in some of its common names refers to the strong fibers within its main stem. The fiber has been used to make fishing nets and was used extensively by Native Americans.
Bigpod Sesbania (Sesbania herbacea)
Native to these Southern United States, Sesbania tends to grow in moist areas, like ours does here along the receding shoreline of the Pond and among the stones and sand of the creekside.
