MAY-JUN JAN -MAY

NO. l8 TREE

GROWTH AND RAINFALL CLOCK

₃₉ Table _19,as stated heretofore,showsahighercorrelationfor 1898- 1941 than for 1850-1897. Thisis true forall month-intervals except for March-April which has lower correlations _ingroups_{4, 7,}and 9 for1898- 1941. Apparently

March-

Aprilrainfallhadgreaterinfluence ontreegrowth duringtheearlierperiod than duringthelater.

Group

5 did not

conform

exceptintheratio ofopposedtrends.

An

exami- nation of thetemperaturerecordsreadily availablegivestable 21.

Obviously, a thermochemical or thermophysiological approach to temperature problemsvia directexperimental evidenceinconjunction

40

SMITHSONIAN MISCELLANEOUS

COLLECTIONS VOL. Ill

April-May

rainfall for the period 1898-1941 overthat of 1850-1897.

Again, figure 6, showing the charted correlations of group ₇ with Santa

Fe

rainfallfor 1850- 1897,

shows

theemphasisto beonspring rainfall. Theserelationshipsemphasizethe multiple nature of growth factorsandthecomplexityof theproblemsinvolved.

Beforethe contrastsbetweenthe periods 1850-1897

and

1898-1941 aresummarized, mention should be

made

of

two

points, one having to do with the incidence of opposed trends

and

the other with cumulative variations. First, the incidence of opposed trends

was

calculated foreachlo-year interval for several of thegroups against the various rainfall intervals. In the case of groups 7, 10, and 11

compared

with

March-

July rainfall the incidence of opposed trends shows a general decline

from

early to recent years.

The same

is

Table21.

—

SantaFe temperatures

1874-1897 1898-1930 1910-1930

March

Average 39-9 394 39-0

Maximum

51.4 50.5 50.1

Minimum

28.0 28.4 27.9

April

Average 47-4 46-75 46-5

Maximum

60.0 58.45 58.2

Minimum 34.76 35.1 34.8

Majf

Average 56.5 55-1 55-5

Maximum

69.4 67.2 67.7

Minimum 43.5 43.0 43.3

true, in fact, for all rainfall intervals except that for March-April in which the incidence increases

from

₁₈₅₀ to 1941, thus agreeing withthe decrease oftree growth-rainfall correlation. Second, figure 7 gives the plotted cumulative variations of Santa

Fe

March-July rainfall

and

certain treegroups.

Groups

5

and

11

and

groups 4 and¹⁰ were each combined intoone graph becausethe separategraphs very nearly coincided. If groups 4 and 5

had

been omitted there

would

have been nochange.

The

graphsillustrate theclose correspondence betweenthe variations of Santa

Fe

rainfall

and

the variations oftree growthas representedby group 1 1 whichcontains thetrees

from

the wettersites.

The

various tables have brought out the contrasts between the periods 1850-1897

and

1898- 1941.

These may now

be

summarized

in respectto March-Julyrainfall atSanta Fe. In so far as data are

i8 TREE

GROWTH AND _RAINFALL — CLOCK

₄₁

available,therainfallrecords of Albuquerque and Las Vegascorrob- orate theresultsobtainedbythe use of Santa

Fe

rainfall.

For

therainfall of the period 1898-1941, against the period 1850- 1897:

amount

of rainfallincreased; andaverage variation, average departure,and averagedeparturefrom

mean

variation decreased.

Cumulative Tree Growth and Rainfall Percent Variations

IN

Hundreds (Ratio Scale')

Groups 4, ¹⁰

850 1870 1890 1910 1930 950

Fig. 7.—Cumulativevariations of treegrowth and ^{rainfall. Trees ingroups} 5 and ii were from wetsitesandthoseingroups 4and 10^chiefly fromdry sites.

For

group 11 contrasted in the same manner: averagevariation, average departure, and average ^departure

from mean

^{variation de-} creased;andcorrelation withrainfall increasedto an extentcompa- rable to that with

Chacon

^rainfall considering the

much

greater distance.

42

SMITHSONIAN MISCELLANEOUS

COLLECTIONS VOL. Ill

For

group lo contrasted in the

same manner

: averagevariation, averagedeparture,average departure

from mean

variation,andcorre- lationwithrainfall increased.

For

group7 contrastedⁱⁿthe

same manner

: averagevariationand average departure increased;average departure

from mean

variation decreased very slightly; correlation with rainfall increased; and internalagreementof the trends

among

the severaltreesincreased.

For

group ₇ (restricted) contrasted inthe

same manner:

average variation,averagedeparture,and averagedeparture

from mean

vari- ationdecreased.

The

substance of theabove

summary

isthat the characteristics of group II,

made up

of wet-sitetrees,

and

group₇ (restricted) agree withthoseofrainfallwhereas

most

of the characteristics ofgroup 10

and

group7 disagree except for correlationwithrainfall. Also,intra- correlationonthe

wood

rises inqualityzvith greaterrainfall.

Obviously,these findings

must

betranslated into a

method whereby

study of the

wood

alone can be

made

to reveal changes in rainfall.

Two

of thetrees

from

the driersites (in group10) for

some

reason reacted oppositelyincomparison withtheremainderof the collection

and when

combinedintogroup₇(alltrees) overbalancedthe influence of theremainder save for the one characteristic, average departure

from mean

variation. Itisclear inrespectto the

Holman

Passtrees that agreement of variation

among

the trees rises with increased rainfall.

Such

increase in rainfall

would

be expected to lessen the variation ofrainfallwithin short distancesonthe

ground

asitaffects

growth and

.thus permit greateragreement

among

thetrees. Thisis well

shown

by table 2 especially

among

groups. Reasoning

from

a knowledgeofrainfallcharacteristicsone canexpectaveragevariation todecreasewithincrease of rainfall.

Therefore, inregardtoa studyof the

wood

alone for evidence of rainfallchanges, the

Holman

Passcollection suggests the use of the following methods: (i) the

amount

of agreement in directional variation,including correlationandtrend parallelism,

among

thetrees themselves_{; (2)} the changein averagevariation, average departure,

and

averagedeparture

from mean

variation

among growth

layersof trees

grown

underconditions,orinazone, at leastasmoistas those

forgroup II or forgroup₇ (restricted).