Dry

    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.) 

   

Purple bindweed/Sharp-pod bindweed/Tie Vine (Ipomoea cordatotriloba)   

Honey bees (Apis) scavenging for water among wet and muddy stones.

     And a couple images of the progress on the Creek house.

Hillside Starvation

Snow-on-the-mountain  (Euphorbia marginata)

     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

1. Henry D. Adams^a,^b,¹, 
2. Maite Guardiola-Claramonte^a,^c,
3. Greg A. Barron-Gafford^a,^b, 
4. Juan Camilo Villegas^a,^d,^e,
5. David D. Breshears^a,^b,^d,^f, 
6. Chris B. Zou^g, 
7. Peter A. Troch^a,^c and
8. Travis E. Huxman^a,^b,^f

Abstract

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

February 13, 2011

The Lion, the Screw, and the Green Dewberry

Off to climb Whitman's Rough (the boulder slope behind the home-site) in search of more signs of a mountain lion.  Two days ago while running a chain saw through the brush to make a traversing trail up to the top, I found a fallen juniper log with what appeared to have several dumps of cougar scat drying nicely.  And not far away from the log, what would typically provide suitable den space.

I really don't know if this is cougar scat or that of a coyote-dog prone to using a

balance beam for a toilet. But whose ever it is, they are sharing it with a raccoon.

  Usually cougar scat is the same size as a dog's or coyote's but possesses distinctly rounded ends and is divided into fairly clear segments, each about one inch in diameter.  The rounded ends were not quite so evident on these specimen.

(This is one special blog, that measures the scat for its dear reader.)

This den-like room among the boulders sits about forty feet north of the scat log.

Inside.

Spring green from the back porch of a mountain lion (of course).

All sorts of waiting places for a mountain lion up in the limestone boulders of 
Whitman's Rough.

If there's a cougar, this would be its trail across Whitman's Rough.

Project: replace all the loose screws on the Hog Shop roof.

So, we need to move into this Hog Shop at some date. But the details to take care of until that time appear endless.  And we have had plenty of help, so no complaints there.  I just drive over to our local and relatively small hardware store, tell the paunchy old man with the Boston accent or the skinny old man in the baggy shorts what my project is, and they take me by the hand and we go aisle to aisle finding the right size of PVC connectors or hex screws or Romex cable.  It's a much more rewarding experience than driving over to our huge store with the motto: "You Can Do It -- Fine, Then Do It."

New-green lighting up the ridge beyond the creek.

One of the first blackberry blossoms from the plants we set next to the orchard.

A shaded little thing growing next to the front gate.  Looks like a geranium or one among the Mallow family (Malvacae).  Perhaps a Rock Rose.  It's a name worth owning, anyhow.

And over near the pond and among the stones, the wild dewberries have dropped their white blossoms and have begun to grow small green berries, ripe for the picking in another month and a half or so.

Harlin's capture of a drought-stricken dewberry fruit (above) and flower (below) alongside the trail leading up the west side of The Pond. 

Last weekend we enjoyed a Saturday with the Hansons and Millers eating more than we had a right to under the Live Oak. And on Sunday, the Little Lady and I donned our dorky snorkel gear and swam with the perch, black bass, and carp among diatomaceous scum and otherwise clear, cold Creek waters.

Here is a start to a plant list of species identified so far, thanks to the work of Harlin.  He and I would both agree that we are seeing more than what's listed here, but those additions will have to wait for another day.  And hopefully, mundane tasks involving hex screws and burn piles will have their end, and I will be able to spend much of  the remainder of my small days filling out Harlin's list with endless descriptions and anecdotes.

Genus	species	English	Family
Juniperus	ashei	Ashe Juniper	Cupressaceae
Pellaea	ovata	Zigzag cliffbrake	Polypodiaceae
Juglans		Walnut	Juglandaceae
Quercus		Live Oak	Fagaceae
Siphonoglossa	pilosella	Tube Tongue	Acanthaceae
Rhus	toxicodendron	Poison Ivy	Anacardiaceae
Calyptocarpus	vialis	Lawn flower	Asteraceae
Amblyolepis		Huisache Daisy	Asteraceae
Chaptala		Silver Puff	Asteraceae
Sonchus		Sow Thistle	Asteraceae
Hymenoxys	scaposa	Bitterweed	Asteraceae
Xanthium	strumarium	Cocklebur	Asteraceae
Berberis	trifoliata	Agarita	Berberidacaea
Onosmodium	bejariense	Flase Gromwell	Boraginaceae
Opuntia		Pickly Pear	Cactaceae
Opuniea		Pencil Cactus	Cactaceae
Tradescantia	gigantea	Giant Spiderwort	Commelinaceae
Convolvulus		Bindweed	Convolvulaceae
Capsella	bursa-pastoris	Sheperd's Purse	Cruciferae
Cucurbita	foetidissima	Stinking Gourd	Cucurbitaceae
Croton		Bush Croton	Euphorbiaceae
Tragia		Noseburn	Euphorbiaceae
Sophora	secundiflora	Texas Mountain Laurel	Fabiaceae
Melilotus		Clover	Fabiaceae
Lupinus		Bluebonnet	Fabaceae
Sesbania	drummondii	Rattlebush	Fabaceae
Prosopis	glandulosa	Mesquite	Fabaceae
Phaecelia	congesta	Blue Curls	Hydrophllaceae
Cisyrinchium	ensigerum	Blue-eyed Grass	Iridaceae
Salvia	farinacea	Mealy sage	Lamiaceae
Lamium	amplexicaule	Henbit	Lamiaceae
Smilax	bona-nox	Greenbriar	Liliaceae
Alium		Wild Garlic	Liliaceae
Nothoscordium	bivalve	Crow Poison	Liliaceae
Wissadula	holosericea	Velvetleaf Mallow	Malvaceae
Colubrina (?)	texensis	Hog Plum	Rhamnaceae
Plantanus	occidentalis	American Sycamore	Plantanaceae
Phlox		Phlox	Polemoniaceae
Oxalis		Wood Sorrel	Oxalidaceae
Oenothera	laciniata	Cutleaf Evening Primrose	Onagraceae
Ungnadia	speciosa	Mexican Buckeye	Sapindaceae
Mimulus	glabrata	Monkey Flower	Scrophulaceae
Veronica	anagallis-aquatica	Water Speedwell	Scrophulaceae
Celtis	laevigata	Hackberry	Ulmaceae
Ulmus		Elm	Ulmaceae
Verbena		Vervain	Verbenaceae
Cissus	incisa	Cow Itch	Vitaceae

The following four photographs come compliments of Harlin.  Indebtedness knows no depths.

Shepherd's Purse

 Tradescantia-gigantica

Bindweed

Smilax

The universe may be large.  There may even be other universes.  But the endlessness of an unwalked, unexplored, unseen universe will never be as vast to me as a few acres of spring-born creek, stonefield, meadow, limestone  boulder-fall, and juniper thicket.  The thought of rounding a bend in the trail and facing a mountain lion excites me to the marrow, but it would satisfy me no more than a trembling last-year's sweetbrier leaf, tenuous in the early April wind.