VOL, 19, NO. 3 SPRING 1989

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Volume 19, Number 3 Spring 1989

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Research BriefsBrain Maps Probe Learning Problems ... Conservation TillageMethods Can Save Both Soil and Money ... Bowhead Whales andOil... How Does Cocaine Kill?

When Friends CompetePsychological research indicates that it is difficult for two peopleto maintain a close relationship such as a friendship or a marriagewhen they both want to perform well in the same area.

Death on the HillAt the Coweeta Hydrologic Laboratory in North Carolina, ecolo-gists are studying the effects of a prolonged drought on a forestecosystem.

ViewpointA University of Georgia ecologist suggests an alternative tocurrent development practices that are bringing destruction to theAmazon rain forest.

A Glowing Sign of Genes at WorkA special low-light video system developed by a University ofGeorgia biochemist plays a key role in a new technique usingbioluminescence as a marker of gene expression.

COVERIllustration by Donald A. Smith. Story on page 8.

PHOTOSPage 4, Dr. George Hynd; page 6, Dr. Emmett Shotts; pages 11-14, Walker Montgomery;pages 15-17, Dr. Carl Jordan; page 17 and page 19, Dr. John Wampler; page 18, NancyBennett. Back cover: Walker Montgomery.

RESEARCH REPORTER is published three times a year by the University of Georgia'sOffice of the Vice President for Research, in cooperation with the Office of PublicInformation. Articles may be reprinted upon request. For additional information aboutany articles or research projects, contact the Editor, Research Reporter, 603 GraduateStudies Building, University of Georgia, Athens, GA 30602; 404-542-5932.

Sigrid Sanders, Editor, Linda Smillie, Publications Coordinator, Charles O. Johnson, ArtDirector/Designer; Lauretta Hannon, Production Assistant.

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Brain Maps

Probe Learning

Problems

Colorful brain maps generatedby a computer may eventuallygive learning disabled children

some help when they can profit from itmost: before they sit down in class.

In the Center for Clinical and Devel-opmental Neuropsychology at the Uni-versity of Georgia, researchers are using aspecially developed computer systemcalled the Brain Atlas to conduct researchon patterns of brain activity in childrenwith learning problems. Their goal is todevelop a way to identify learn-ing disabled children before theyenter school.

Educational psychologist anddirector of the center GeorgeHynd explains that learning dis-abilities often don't surface untilchildren are required to sit stilland focus on projects such asreading. "Often a disability is inan area where a young child canavoid or perhaps even compen-sate for it," Hynd says. "But theeducational system puts an em-phasis on language abilities andon the ability to sit still. A prob-lem in these areas—such as read-ing disabilities like dyslexia orattention deficit disorder withhyperactivity—often becomesmanifested in the school envi-ronment."

When these children startschool, they suddenly find them-selves unable to learn, and theybecome labeled as slow or defi-cient.

According to Hynd, presentpsychological testing proceduresfor children do not always iden-tify learning disabilities accu-rately, and they are not able to

distinguish between problems broughtabout by social or emotional factors andproblems with a neurological cause. Hebelieves that brain mapping techniqueswill be able to pinpoint problems moreaccurately.

"When children do poorly on a psy-chological test, we often don't know ifit's because of uneven cognitive devel-opment or because of a neurologicaldeficit," he says. For example, the childwho can't sit still or can't pay attentionor constantly disrupts class may havemore than an emotional problem. "It ispossible that classroom problems mayhave a neurological basis," Hynd says."Our equipment helps to assess atten-tional and perceptual processes."

In a normal child (top), a brain map shows a symmetrical waveof brain activity in the central region of the brain. In a child withdyslexia (bottom), a brain map shows an asymmetric wave ofbrain electrical activity and a reduced amplitude. Each mapreflects an average event-related potential (ERP).

The child being tested wears a capcontaining electrodes that measure brainactivity. It's kind to the child wearing it;no needles invade the scalp. The electri-cal activity is transmitted through thecap to the testing equipment and intothe computer.

A monitor on the wall flickers in achanging checkerboard pattern. As thechild watches, it changes 200 timesduring the test; every change triggersbrain activity, which is recorded by thecomputer. The same sort of stimulationfor auditory testing uses a series ofclicks, or tone bursts.

As the information is collected, apicture of the brain as if seen fromabove the head starts to form on the

computer screen. The colorson the brain map show patternsof brain activity.

"The research is basic andattempts to find out how eachchild we're testing functions inrelation to normal children,"Hynd explains. The studiesinclude children with normallearning development as wellas children with severelearning disabilities, behav-ioral problems, epilepsy,psychiatric disorders, andchildren who have sufferedbrain damage from accidentsor disease. Neuropsychologicaltests are also administered tohelp analyze and interpret thedata collected in the brainmaps.

"Our ultimate goal is tohelp children with neurologicalproblems function in an educa-tional environment, either inthe mainstream or in specialeducation situations," Hyndsays. If these children can beidentified early, he says, theywill have a much better chanceto succeed in school.

—Elinor Ruark

4 The University of Georgia

Death on the Hill

By Sheila Roberson

| o a casual ob-I server, a 200-year-old oak inthe middle of

the"forest might not show anysign of stress. It looks tall andstrong and impervious to theravages of weather. But adrought can do more damagethan we see. The tree cansuffer in ways that may notbe apparent for many years tocome.

The drought of 1985-88took a toll on trees through-out the Southeast, accordingto UGA ecologist WayneSwank, and the long dry spellcontinued into early 1989. Inthe Coweeta Basin, a forestedregion that stretches over5600 acres in the mountainsof southwestern NorthCarolina, Swank and otherscientists are studying theeffects of the prolongeddrought on a forest ecosys-tem.

The Coweeta HydrologicLaboratory was establishedby the U.S. Forest Service in1934 as a study area in whichto evaluate the impact offorestry practices on theregion's water supply.Research has focused on theimpact of practices such asforest cutting and logging onthe quantity, timing, andquality of streamflow.

For the past 20 years,scientists from the University

of Georgia's Institute ofEcology have also used thisarea for ecological research,in collaboration with scien-tists from the Forest Service.Continuous funding from theForest Service and theNational Science Foundation(NSF) has supported thecooperative research, and theCoweeta site is now one of17 NSF Long-Term Ecologi-cal Research centers.

Swank, who is Forest

Service project leader atCoweeta and an adjunctprofessor of botany at theUniversity of Georgia,emphasizes the benefits ofthis interdisciplinary researchfor both science and society.

"The long-term recordsand studies accumulated atCoweeta provide a uniqueopportunity to evaluate majornatural disturbances andcompare them with man'sdisturbances," he says. "Thisknowledge could lead to

modifications of managementactivities and advancedplanning that may lessen thedeleterious impacts of naturalevents on forest resources inthe future."

Jack Waide, a researchecologist with the ForestService, explains that thereare at least two differentways to look at a drought.The most obvious effect islow levels of streamflow. Butfrom a biologist's point ofview, he says, the effects of adrought are more specificallydefined as an unusualdeparture from the normalavailability of water. Forinstance, the level of water ina stream rises and fallsdramatically in a normalyear, and an insect that livesin the stream copes withthese expected seasonalfluctuations. But if water isreduced at time when itshould be high, it canseriously disrupt the normalbiological functions of theinsect.

"This departure fromnormalcy is important from abiological standpoint inreference to life cycles oftrees and to forest animalsthat may be impacted by adrought," says Waide.

Scientists at the CoweetaHydrologic Laboratory havebeen collecting information

Research Reporter 11

Lloyd Swift, a research meteorologist with the U.S. Forest Service,collects information about rainfall and other weather patterns at theCoweeta Hydrologic Laboratory. Below average rainfall began in late1985 and continued almost without interruption into early 1989.

about the prolonged droughtfrom a number of different in-dicators in the ecosystem.They have documented lowrainfall amounts beginning in1985 and lasting, with somevariation, through the earlymonths of 1989; lowstreamflow rates for the sameperiod; a reduction in soilmoisture that is affectingspecies of moisture-lovingtrees; an increase in theacidity of rainwater; thedeaths of many older oaktrees; and an increased inci-dence of trees dying becauseof disease and insect attacks.

The scientists point outthat although many of theirstudies have resulted in im-mediate answers about theeffects of drought, otherstudies may take years tocomplete.

Records of streamflowrates and volumes havebeen maintained in the

Coweeta region for morethan 50 years by

collecting informationfrom instruments on weirsthat have been installed in

streams.

12 The University of Georgia

Rainfall

The current drought in theSoutheast is the worst onrecord for the last 50 years,according to Swank.

"We know that we've hadworse droughts (more than 50years ago)," adds LloydSwift, a research meteorolo-gist with the Forest Service,"but this one is consideredmore severe because morepeople are affected by it."

Records from the Biologi-cal Station at Highlands,N.C., near the Coweeta area,show that the area has experi-enced several droughts in the

past, notably one in the late1920s that preceded the DustBowl years in the AmericanMidwest, and another low-rain period that lasted for fouryears in the 1840s.

Records of rainfall at theCoweeta Laboratory showbelow-average rainfall begin-ning in late 1985 and continu-ing almost without interrup-tion into early 1989, with atotal rainfall deficit of 72inches in the region over thepast four years. The mostsevere rainfall shortage wasrecorded during the first ninemonths of 1986. Statistically,a shortage of that severity isexpected to occur in theCoweeta area only once every250 years, Swift says.

Streamflow

Although records ofrainfall are important,streamflow measurements areprobably the best overallreflection of a drought'sseverity, Swift says. Rainfallthat comes in the middle of adry period might seem toindicate a break in thedrought, he explains, but ifenough water does not getinto the streams, droughtconditions will continue toexist.

Records of streamflowrates and volumes have beenmaintained in the CoweetaLaboratory region for morethan 50 years, and these

records are a valuable aid inanalyzing the severity of thecurrent drought. Measure-ments are taken at regularintervals by instruments onweirs that have been installedin numerous streams in thewatershed.

In 1986, very lowstreamflow rates reflected thesevere rainfall deficit.Because the ground becameso dry during this period,Waide says, their dataindicate that the smallamounts of rain that did fallwere not able to wet thesubsurface soil and reach thestreams.

The reduction instreamflow has a direct effecton aquatic habitat—and alsoon the species of trees thatnormally grow along streams.One reason the forest issuffering as much as it isfrom the current drought,Waide says, is that severalyears of abundant water inthe streams and soil precededthis dry period, encouragingthe spread of the kinds oftrees that need plenty ofwater.

"If you have a tree, suchas a yellow poplar, that nor-mally grows on a moist sitealong a stream, and then themoist area expands during awet year, some of the youngof that tree will spread to thenew site," he explains.

"Essentially this is whatwe have experienced at

A Fish Story

Strange as it may seem, some kinds offish seem to flourish in a drought.

Studies at the Coweeta Hydro-logic Laboratory have indicated that fishpopulations in Coweeta Creek actually in-creased during the worst of the droughtperiod in 1986. "I know this result iscounterintuitive, but there's a good reasonfor it," explains Gary Grossman, an associ-ate professor in the' School of Forest Re-sources at the University of Georgia, whowas in the middle of a long-term study offish populations in the Coweeta area whenthe drought struck.

"We found that survivorship of youngfish increased, because during the droughtperiod there was very little winter flood-ing," Grossman says. "In years of normalrainfall, winter floods usually cause largelosses in fish populations. But becausemore young fish survived during thedrought, we documented an overallincrease in the fish population in our studyarea."

When he began a project to study theimportance of environmental factors onfish populations in Coweeta Creek in 1982,Grossman expected to record fish re-sponses to the normal seasonal fluctuationsin streamflow.

"We wanted to find out if the abun-dance of fish in the Coweeta streams iscontrolled more through biological interac-tions, such as competition for food andspace, or by winter floods that suppress thepopulation enough so that competitiveinteractions are unimportant," he explains."Because of the drought, we've been ableto study this question, and also to look atwhat happens when there are no winterfloods. We've actually been very fortunateto be able to collect data before, during,and after a major drought."

Another observation made during thedrought was that two species of minnowsmoved upstream to live. Grossman believesthe move was probably caused by areduction in the velocity of water in thestream.

"There are a number of factors that cancontribute to the movement of fish popula-tions," he says, "but the first ones we lookat are usually stream velocity and watertemperature.

"We noted that the water temperaturein the stream changed only one degreecentigrade during the drought, but thevelocity seemed to decrease. We think thesetwo species moved upstream because of thereduced velocity. It will be interesting to seeif they move back downstream after thedrought."

Grossman obtained his data on habitatselection mainly through direct observationof fish in the stream. At each study site, thepresence of various fish species was notedperiodically, along with the numbers of fishin each species. The exact location of eachfish was recorded, including its depth in thewater and distance from the creek bottom.Measurements also recorded the velocity,temperature, and depth of the water.

The information about fish populationscollected during the drought will be helpfulto forest managers, Grossman says, but hestresses that more study is needed on fishpopulations in Southeastern streams todetermine the long-term effects of bothnatural Bnd human disturbances.

—SR

Many hours of direct observation by aresearcher have gathered detailed informationabout where fish occur in Coweeta streams. Theinformation contributes to one part of acomprehensive study offish ecology in the area.

Coweeta: an expansion tonew areas of trees that growfast and require highly moistsoil conditions. Over theyears, there has been agradual change in the forestcomposition as these mois-ture-loving trees creep up theslopes."

The blight that killedchestnut trees during the1930s also helped themoisture-loving trees expandtheir territory by opening newareas for them to fill. But inthe current drought, many ofthese moisture-loving treesare suffering badly as themoist areas around streamssteadily become smaller.

Water Chemistry

For the past 20 years,scientists at Coweeta havemeasured the chemistry of therainfall and the chemistry ofwater in streams, and theyhave documented some pro-nounced changes during thedrought years.

During 1986, the concen-tration of hydrogen ions inthe rainfall was twice as highas the long-term average forthe Coweeta region, andmuch higher than the re-corded concentration for anyperiod in the past 20 years.What this means is that therainfall was unusually acidic,with the pH averaging 3.85during the 1986 growingseason and 4.0 for the entireyear—compared with a long-term average pH of 4.45.

In addition to greateracidity, the rainfall in 1986also carried a higher thannormal concentration ofchemicals, Waide says.Chemicals normally accumu-late in the atmosphere and arepicked up and dissolved byrain as it falls through the air,he explains. During adrought, the concentration ofchemicals increases becausethere is less rain in which todissolve them.

The water in streams hasshown a similar increase inthe concentration of chemi-

Research Reporter 13

cals, but there has been noclear change in its acidity.

Scientists do not yet knowwhat effect the increasedacidity and higher concentra-tion of chemicals in rainfallwill have on the plants,animals, and soil that makeup the forest ecosystem.

"A plant that is partiallydependent on atmosphericchemistry for nutrients mightfind the increased nutrientsadvantageous," says Swift."The fact that the concen-tration of nutrients and acidscoming in from the atmos-phere is greater is normallyconstrued as being bad—butthat might not necessarily bethe case."

Death on the Hill

But the drought alreadyhas taken its toll. Aerialsurveys of the Coweeta Basinin 1988 show many treesturning brown and otherscompletely bare of leaves inthe middle of the summer.Barry Clinton, a UGAgraduate student in forestecology, says that his studieshave shown a measurableimpact on forest compositionby the drought, especiallythrough a reduction in thenumber of dominant oaks.

"Most of the trees thathave died are the older,dominant oaks," he says."Scarlet, black, and northernred oaks seem to be especiallyvulnerable to dry weather,while white oaks are moreresistant."

Clinton is not concernedfor the long-term health of theforest, but he points out thattrees lost during the droughtmay not be replaced by thesame kind of vegetation. Insome areas, other tree speciessuch as red maple and yellowpoplar are expected toflourish. But in areas wherethe forest floor is alreadycovered with rhododendronand mountain laurel, theseunderstory thickets may allowtoo little light and other

Jack Waide, a research ecologist with the U.S. Forest Service, examinescore samples to analyze rates of tree growth. There are indications thattrees have been growing more slowly throughout the Southeast duringthe past two decades.

resources for new treeseedlings to grow.

"Our oak trees are notendangered, and neither areour hardwood forests,"Clinton states. "Tree mortalityis a natural part of our forestecocystem." However, hecontinues, the composition ofthe forest will almost cer-tainly be affected for manyyears.

Disease and Insects

When trees are stressed bylack of water, they becomeincreasingly susceptible todisease and to insect infesta-tion; these drought effects canlead to the death of substan-tial numbers of trees. A rootfungus in hardwood trees anda beetle that attacks pinetrees, for example, both havecaused more damage in theCoweeta Region during therecent dry years than in yearsof normal rainfall.

Clinton's studies haveshown a high correlationbetween elevated infectionsof a root fungus calledarmillaria and trees that havedied since the drought began.

"The trees that have diedhave been exposed to thefungus for all of their lives,"he says. "It appears that the

drought weakens them to thepoint where the fungusbecomes more prevalent, andeventually it kills them."

Over the last 30 years,pine trees in the mountainridgetop forests have beensubjected to several Southernpine beetle epidemics. Now,says Swift, another epidemicis underway in the region.When a pine beetle drills ahole in the stem of a healthypine tree, he explains, the treesecretes pitch that pushesthrough the hole and preventsthe beetle from invading thetree. But when pines aremoisture-stressed, they arenot able to make enough pitchto repel the beetle.

"Our expectation is thatwe will continue to experi-ence considerable losses ofSouthern pines all overGeorgia and the Southeastover the next year," saysSwift. "This will mean amajor loss of forest resourcesand a major economic loss tothe region."

Reduced Growth

Trees that live through adrought and survive attacksby disease and insects maystill suffer in serious ways,such as reduced rates of

growth. Tree-ring measure-ments on core samples fromover 30 years of research atCoweeta make it possible forscientists to easily identifyyears of normal growth andyears of slow growth.

There are indications thattrees have been growing moreslowly in recent years, Waidesays; however, it is not yetclear that the drought is theonly reason. It is likely thatother factors are involvedalso.

The USDA Forest ServiceSoutheastern Forest Experi-ment Station has documenteda declining growth rate intrees in the Southeast thatbegan about two decades ago,and drought may be one ofseveral factors contributing tothis decline. "The obviousquestion is whether airpollution and acid rain arecausing the decline alongwith other environmentalfactors," Waide points out.

"Drought is a naturalevent," he continues. "It is asignal in the environment thattriggers certain kinds of re-sponses, but sometimes itseffects are very subtle. Wemay not detect these changesfor twenty years or more. Ifdrought does have a majoreffect on mortality and on theexpansion of new individuals,we may not observe all of thelong-term impacts on theforest for perhaps fifty years."

Waide and his colleaguesat Coweeta consider it tooearly to know for sure howthe current drought will affecttree growth. They point outthat the climate naturallyvaries over long periods oftime, and forest species haveevolved mechanisms to dealwith this variability.

"We are still in the processof analyzing and integratingthe immediate, knownimpacts of the drought onforest resources," Swankconcludes. "At the same time,we are initiating and continu-ing studies to evaluate thelonger-term consequences ofthis unusual event." If

14 The University of Georgia