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New Mexico State University

Trees that can take the heat

[Coye Balok ]
Measuring for success: Graduate student Coye Balok measures leaf area to identify shade trees that can thrive under New Mexico's drought conditions.

In New Mexico, landscape trees don't exactly have it made in the shade. Sunny, dry conditions make it hard for some trees to survive, limiting homeowners' options.

"Many people want to know what type of shade tree to plant in their yards," says Rolston St. Hilaire, an NMSU landscape design researcher. "Currently, we have a limited palette of shade trees for southern New Mexico."

St. Hilaire is trying to identify shade trees that can best handle moderate drought conditions, which can be caused by more than lack of water. Trees growing in pots or in the city surrounded by lots of concrete also have trouble surviving.

In an initial greenhouse study, St. Hilaire worked with graduate student Coye Balok to identify drought-tolerant trees that could thrive for years to come. They tested seven trees: golden rain tree, Arizona ash and five different types of native oak.

Balok took measurements for four months, watering the trees and allowing them to lose half of their water to simulate drought.

"I had to come in between 4 and 5 a.m. to take water potential measurements from each leaf from each tree of each species," he says. "So I would have to take a predawn measurement and then I would come in the same day between 10:30 and 11 and take a midday water potential measurement, showing us how well the leaf rehydrates in the span of one day."

The leaves can tell a lot about which trees can weather New Mexico's weather. Typically, thicker, waxier and hairier leaves mean less water loss. Leaves with lots of hairs-called trichomes-feel velvety.

In addition, the number and size of the leaves' pores-known as stomates-play a role in water regulation.

To analyze these leaf characteristics, Balok and St. Hilaire studied scanning electron and light microscope images of the seven species.

Results from the greenhouse and microscope work showed that even though the commonly used Arizona ash is the most velvety, it may not be the best choice for New Mexican landscapes. The tree showed signs of transpiring or losing water quicker than the other species.

On the other hand, the researchers say the golden rain tree may be a good bet, because it seems to adjust well to drought conditions.

In general, the oaks were better at regulating water loss. The Texas red oak had the highest ratio of root growth to top growth, which is an important trait for tolerating drought. And with lots of trichomes and stomates, the Chinkapin oak also did well in controlling water loss.

Before making any final recommendations, St. Hilaire plans to test the species that did best in the greenhouse in an outdoor study to gauge how well the trees respond to southern New Mexico's sunlight and soil characteristics.

A third stage of the study would be to develop water-use recommendations for the trees that best tolerate drought.

Siccing native grasses on arid lands

[Master gardeners]
Great grasses: Master gardeners Carole Jasler (left) and Carolyn Lindberg and former Bernalillo County horticulture agent Carol Cammack make a selection of little bluestem grass for xeriscaping.

Businessman Blake Curtis thinks NMSU's Agricultural Science Center at Los Lunas is just short of God's gift to grass growers of the Southwest.

Clovis-based Curtis and Curtis Inc. grows and sells some 30 varieties of native grasses, about half of which are new varieties developed at the center and released for public and commercial use.

"The Los Lunas center is constantly coming up with new varieties that allow us to put grasses in places that either never had grass before, or in places where planters always found it extremely difficult to grow grass," Curtis says. "About 50 to 60 percent of all my sales now come from native grass varieties that the NMSU center has tested and developed."

Scientists at the center, in operation since 1957, are currently studying about 40 different native grass varieties. These varieties allow growers to cultivate grass on some of the most arid lands, paving the way for a wide range of uses, including reclamation and conservation efforts, improved pasture land for grazing, and landscaping and yard work where planters want to conserve water.

"Water issues are perhaps our top priority," says center superintendent Mike English. "Water quality and quantity is on everybody's mind, so we develop grass species that use a lot less water like buffalograss or blue grama."

Before year-end, the center plans to release cane bluestem, a low-water use native grass that, in addition to reclamation and landscaping purposes, can be used for pasture lands.

"The cane bluestem is great for rangeland reclamation because the livestock really love it," English says. "It seems to be almost like candy for the cattle. It's got real potential."

Apart from water conservation, new grass varieties also have sound environmental benefits, says Ramona Garner, an agronomist with the U.S. Department of Agriculture's New Mexico Plant Materials Center, located at the Los Lunas center.

"Runoff is always a big issue in terms of water quality," Garner says. "Some of the grasses we develop can be used as buffer strips around crop fields, which help to filter out pesticides so that they don't go into the water system."

Researchers at the center also are developing bunch grasses that can be used by farmers as windbreaks to protect their crops from gusting winds. Giant sacaton which has the potential to grow 6 to 8 feet tall, is one such grass.

"It's perfect for windbreaking," Garner says. "It's not a tree, so farmers can mow it down and it will still grow back the following year."

The center releases new grass varieties through the New Mexico Crop Improvement Association to certified growers like Blake Curtis, who in turn cultivate the new varieties and sell them wholesale to retailers and consumers of large amounts of seed, such as transportation and highway departments.

"The center continues to develop products that have a wide variety of uses, and they're very much in demand on the market," Curtis says.

Searching for genes related to drought-resistance

[Trejo-Calzada ]
Making copies: Graduate student Ricardo Trejo-Calzada uses a thermocycler (below) to amplify or make many copies of plant genes associated with drought.

Researchers are picking up the pace in Mary O'Connell's molecular genetics laboratory at NMSU as they search for genes that play a role in how plants respond to drought.

During the last decade, the researchers could study only one gene at a time. Now with a new technology called microarray analysis, they can consider thousands of genes at once.

"This technology has primarily been used in medical applications to study the molecular basis of disease," O'Connell says. "We're planning to test how well it works to solve agricultural and environmental problems in plants."

The researchers are collaborating on the project with scientists at Los Alamos National Laboratory (LANL).

"Drought is the most common and severe limitation to plant productivity," O'Connell says.

As plants evolve in arid and semiarid regions, they make physical, physiological and biochemical adaptations in order to survive. O'Connell wants to find out what's happening at the underlying genetic level that creates those adaptations.

"This information can be used to improve crop plant productivity in semiarid areas or to monitor biodiversity in plant populations in the wild," O'Connell says.

Drought-resistant plants may be expressing different genes than their non-stressed relatives, or they may express the same genes in different ways, such as turning them on in varying amounts or turning them on earlier or later in the plant's development, she explains.

[thermocycler]

Researchers in O'Connell's lab are gathering genes from the leaves and roots of chile and drought-resistant forage grasses, clovers and tepary beans, crops native to the Southwest. They are amplifying or making many copies of these genes for use in the microarray analyses. Rich Richins, a science specialist in the lab, has been instrumental in accelerating the rate at which these genes can be gathered and amplified.

The LANL scientists, led by Robert Cary, will then use their technological expertise with microarray analysis to look at the expression of thousands of these genes at once. This will help O'Connell identify which genes related to drought-stress deserve further study.

When so many genes are considered at once, O'Connell says there is the possibility of less accurate results. But so far, results from the new technology are backing up the findings from the more traditional, one-gene-at-a-time approach.

O'Connell also is cataloging genes related to how other legumes, grasses and vegetables respond to drought. These catalogs are known as DNA libraries. She says each gene is like a book in the library. When the researchers amplify the genes, they are essentially making copies of the books for future study.

In a related project, O'Connell is looking for overlaps in the genes plants express in response to drought stress and diseases. Specifically, she is studying the intersection of the genes related to drought and Phytophthora root rot in chile plants. This information could help improve crop management practices.

Bird watch keeps an eye on grassland species

[black-throated sparrow ]
Black-throated sparrow

NMSU ornithologist Martha Desmond is putting grassland birds like the Baird's sparrow and the Sprague's pipit on the spot. She wants to find out why their populations are declining in the United States.

Desmond says much of the desert grasslands have disappeared as more shrubs and humans move in. "Grassland birds have a difficult time because their habitat has been altered," she says. "They're now forced to exist in a different system than the one they evolved in. The challenges they face are habitat loss, alteration and fragmentation. Remaining small habitat patches are insufficient and increase the risk of predation, because it's easier for predators to search small patches."

Most grassland birds breed in the northern United States and Canada and winter in the southwestern United States and Mexico. Desmond's research is related to grassland birds that winter in Mexico.

Little is known about migratory behavior or important migratory and wintering habitats for grassland birds. "This area of study was really wide open," she says.

Desmond's research compares the distribution of grassland birds from winter to winter. "You'll see different patterns in different species," she says. "Some species are found in a lot of different types of habitats or habitats in different levels of condition."

Desmond is trying to find out if these species are dispersing widely or staying in the exact same spot. "If they're staying in certain spots, why are those spots so attractive to the birds?"

To find the answers, Desmond works in the birds' wintering grounds, capturing and banding them. "This helps us know if they return to the same site year after year, winter after winter, or do they go to other sites?"

Desmond conducts her research in several areas around Chihuahua, including private ranches and field stations belonging to the Universidad Autonoma de Chihuahua.

The research, in its third year, is showing that some birds do return to the same wintering spots. Some return to the exact spot and others return to the same area, but not the exact spot. "There are certain species that will stay in the exact spot," she says. "We think these birds may actually hold territories during the winter months. That's something we never realized."

But Desmond adds that these are usually exceptions to the rule. "By and large, grassland birds are quite nomadic, and we're banding a whole new group of birds every year. You'll catch them once, and you'll never see them again."