Interesting article on tree roots : DURHAM, N.C. -- Taking advantage of a unique labyrinth of Texas caves festooned with tree roots, Duke University biologists have given trees the most exacting root-to-twig physical of their circulatory system yet. The scientists' findings reveal the impressive adaptive engineering of deep-rooted trees in adjusting the size and structure of their piping, or xylem, to maximize water uptake, maintain their integrity and avoid flow-blocking embolisms. In particular, the findings reveal how the deepest roots develop the largest conduits in order to draw deep water most efficiently. The scientists' technique of studying tree roots in place offers a far more realistic look at how trees manage their water circulation than researchers have had before. The approach is like studying the plumbing of a house by carefully tracing its pipes, valves and faucets. In contrast, the usual approach -- drilling core samples and separating tree root samples for study -- is like taking a wrecking ball to the house and sifting through the debris to understand the plumbing system. The researchers, led by biologist Robert Jackson, published their findings in the September 2004 issue of the journal "New Phytologist." Lead author on the paper was Andrew McElrone, formerly of Duke and now at St. Joseph's University in Philadelphia. Other co-authors on the paper were William Pockman of the University of New Mexico and Jordi Martez Vilalta of the University of Edinburgh in the United Kingdom. Jackson is a professor of environmental sciences and biology in the Nicholas School of the Environment and Earth Sciences and a professor in the Department of Biology at Duke. The scientists' work was supported by the National Science Foundation, the Mellon Foundation and the U. S. Department of Agriculture. In their study, the researchers took advantage of the fact that a well-mapped system of limestone caves runs beneath the Edwards Plateau in central Texas. Thrusting into those caves from above are the roots of trees, some of which reach depths of 60 feet. The Texas state government is interested in understanding the effects of such trees on water uptake because the Edwards aquifer supplies a large area of central Texas with drinking water, including the city of San Antonio. The water supply from this aquifer has been affected by the change in the landscape above from a savanna to forest, due to grazing and human prevention of natural wild fires over the last 150 years. In their experiments, Jackson and his colleagues descended into the caves and sampled roots of four tree species -- a juniper, an evergreen oak, a deciduous oak and the deciduous gum bumelia, which is also known as the chittamwood. "The evergreen oak we studied is the dominant oak on the Edwards Plateau," said Jackson. "Because it needs a lot of water to maintain its year-round foliage, it has the deepest roots, going some 60 to 75 feet into the bedrock to find water." In their studies, the researchers did genetic fingerprinting on both the roots and above ground trees to match the roots to specific trees. The fingerprinting is the same technique used in criminal forensics. They then measured the diameters and wall thicknesses of the water-conducting root xylems. And in laboratory experiments, they determined how vulnerable specific sections of root were to "cavitation," in which mechanical stress or drought induces bubbles that block water flow. The researchers found that trees adjust their root anatomy very effectively to work in different environments. Shallow roots and especially stems have thicker walls and smaller interior diameters because they must support the tree more, and because they experience more drying and temperature extremes that cause cavitation. Deeper roots, more protected from such demands, can have larger diameters and thinner walls to maximize the conduit size and enhance water flow. "The data are interesting because they show that the same individual plant can adjust its anatomy and physiology to maximize water transport deep underground where the plant is less likely to experience drought or freezing conditions which cause cavitation," said Jackson. "The surprise was the extent to which individual trees can make these developmental changes," he said. "There has long been data showing that roots tend to have larger conduits than shoots. But there has not been an analysis like this looking across the gradient of differences within the same plant. And nobody has analyzed roots that go as deep as these," said Jackson. According to Jackson, such insights will improve theoretical models of water transport within trees. "If you're building a model of water transport and you don't take into account these differences among roots, you could severely underestimate the importance of those deep roots," he said. "Their biomass isn't that great, but they are extremely efficient in transporting water." In further studies, Jackson and his colleagues are installing instruments on trees to measure their water flow in real time to determine the dynamic effects of the anatomy they have discovered. "These studies will allow us to ask what proportion of the water in trees comes from different depths and how that proportion changes during drought conditions," said Jackson. "Ultimately, the question behind this work is how much of the water balance of the Edwards Plateau is driven by the vegetation. And for that question, we need more than static physiological measurements. We're already teaming up with hydrologists and geologists in the region to find the answer." -------------------------------------------------------------------------------- Adapted from materials provided by Duke University.

Actually, designing a swale or even a rain garden is a good idea for many gardens, even quite small ones. And it really doesn't make too much difference with the dryness - or not - of the climate. Unless already existing as a low lying, water accumulating area (i.e. a bog or swamp, perhaps only seasonally), a swale will simply catch and retain rainfall and allow it to be gradually absorbed into the soil. Among the reasons for this is to avoid seasonal flooding of the landscape, to reabsorb pollutants that are present in storm run-off before they can reach streams and groundwater or simply to retain and re-use infrequent rainfall. In your case, the latter seems most appropriate although when it does rain in SoCal, that rain can come fast and furious, so the other two reasons may be equally as valid as well, at least on a now-and-again basis. A swale is just a low lying area......when rainfall does occur, the water will flow to the lowest point, the swale, so it does need to be constructed to be lower than current grade. If any slope to the yard at all, the swale should be located at the low point. If not, you need to grade your new "lasagna" planting to slope away from the structure and toward to the designated swale site. And you will need to excavate the swale to some degree, depending on the thickness you can manage with your lasagna method. I doubt constructing swales was devised with a lasagna method of bed construction in mind. It does involve some work to do it correctly. Grading and directing water runoff to the correct area is critical. And you want something that slows water penetration yet provides good drainage at the bottom of the swale, not just soil - coarse sand and river rocks or coarse drainage gravel are common. And yes, this is much more of a landscape design issue than just a soil question ;-) Do some research online to see how to construct an effective swale. Even check out rain garden sites - they are a wealth of information for this sort of activity if for a slightly different purpose. One other thing you may want to do is investigate dry stream beds as a landscape feature. Not only do these make an attractive focal point to a drought tolerant garden, they will help to direct any rainwater runoff (even irrigation run-off) to the appropriate swale location where it can be dissipated evenly through the soil profile. Where moisture accumulates surrounding the swale and along its sides is where you can locate more thirsty plants. If you don't already have a landscape designer, you might want to consider hiring one. They could be a huge help in the layout, design and construction of this kind of feature, as well as offering suitable planting suggestions.

It holds up fairly well if I trim the stalks that fall over once in awhile during the winter. When it starts looking worse than good in late winter I set fire to the clumps that are out in the open. They burn right down to the crown and sprout in the Spring like n Burning is more fun than whacking the stalks down and disposing of them. Sometimes after cutting the stalks down I spread them out and cover with woodchips. I got the idea of burning them from the grass seed farmers in eastern Washington and Idaho. The burned fields produce more seeds the following year than the unpruned fields. There are no seed heads on the above picture because the clumps are in partial shade. They're not all that attractive anyway. othing happened. The clumps spread slowly. I have four as large as the one shown. In the picture below, the 'Giganteus' will be the first to go as I edit this over planted, confused area. Mike

Thanks for that tip, David! I googled sod webworms, and found a site or two that explained/described them and had some suggestions for how to identify if you have them: http://www.uri.edu/ce/factsheets/sheets/sodwebworm.html. I first went around and looked closely at the grass/soil, but could not find the signs they said to look for. I then did the soapy water test, but didn't see any of the caterpillars (larvae) come to the surface. I did see one adult moth, but they say that doesn't necessarily mean you have the caterpillars as the moths will fly quite some distance. I then took my hand spade/fork and chopped into some various areas to look under the grass about an inch or so, to see if I saw any grubs, caterpillars, etc. that could be the cause. But only found some ants and earwigs. I don't think either of those could cause damage to the lawn. So I am still at a loss, but will continue to look for any signs of the webworms or grubs. Or I may try to find some of the biological bacteria the sites talk about for killing the larvae and treat it anyway. The sites also mention types of grasses that are more resistant to the webworms (types of ryegrass and fescue). So possibly overseeding this fall with these or other hardier grass(like the Reveille blend that Amester mentioned, or others in the thread you linked to David) may be an answer. I am interested in the EZ Wet and Field Magic that Bob_In_Colorado has posted about and may try some of that - for a smaller sized area, though, as this much lawn area has proven to me to be too expensive to maintain (both with $$ on water, and time!).