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III. Characteristics of Growth and Climatic Tolerance

III. Characteristics of Growth and Climatic Tolerance

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312



M. RAUPACH



mean height

at 9A.M.



i



60



50



f



5

mean diameter,:\



4



3 c

0

2 .c



c



............*



E o



JFMAMJ JASOND



I



JFMAMJJ ASOND



FIG.4. Annual growing pattern of Pinus radiata at Mount Burr, South Australia,

together with data for soil temperature measured at a depth of 3 inches at 9.00 A.M.,

rainfall, and potential evapotranspiration calculated using Thomthwaite's formula

(Pawsey, 1984; Ruiter, 1984).



winter are also found in California. On the other hand, Will (1964)

observed that in New Zealand the tree grew for almost the whole year.

This difference is probably due to climate (see under Section 111, C ) .

FOR FOREST

USE

C. CLIMATIC

LIMITATIONS



The range of latitudes for plantings of P . radiatu is 32" to 46", and

mainly about 37", the northern Hemisphere having fewer forests. The

tree flourishes in Mediterranean and warm temperate climates (see Fig.

S), It has been very successful in New Zealand, where day length rather

than soil or air temperature is said to limit the growth during winter

(Will, 1962).

MilIett ( 1944) at Stromlo, Australia, concluded that among climatic

phenomena, rainfall as a single factor was most important in determining

growth. Prescott and Lane Poole (1947), while pointing out that annual

rainfall of 30 inches or more was desirable, quoted excellent results from

areas of winter rainfall receiving 22 to 25 inches annually (see also

Kessell and Stoate, 1938). Prescott and Lane Poole concluded that the

seasonal distribution of rainfall was important, a well-distributed rainfall being undesirable. Experience in New Zealand has shown that this

is not quite correct. It is true, however, that hot damp summer conditions

are not favorable since they encourage fungal attack, but in spite of this,



Pinus radiata

Country



Place



U.S.A



Santa



37'N



Colifornio



Crur



12PW



USA.

California



New

Zealond



South

Africa



Position



Altitude

Maximum and

and

Minimum temperature

Days of Frost and Distribution

Distribution

in.

OF.

Sea level



6



JASONDJFMAMJ



J



D



J



a JFMAMJJASOND



J



J



D



J



J



D



Point

35'40"

Piedros

Bloncos 121'27'W



Rotorua



Tokai



38'09's

176"15'E



340s

I8015'E



931ft.

34



Sea level

not avail.



6



JFMAMJJASOND



Chile



South

Australia



313



FORESTS



Concepcion



Mt. Burr



36-50's

73'03'W



37033's

140'24'E



Sea level

not ovoil.



-....



4



210 ft.

JFMAMJJAEOND



J



J



0



FIG. 5. Monthly rainfall and mean monthly maximum and minimum temperatures at locations in different countries in which Pinus rudiutu is grown, with some

data on the number of days of frost per year. (After Scott, 1960.)



a certain amount of summer rain, or at least fog or moist conditions, is

necessary.

In giving the climatic limitations of the species for Argentina, Golfari

(1959) quoted an absolute minimum temperature of -7°C. ( 19°F.).

Pryor (1947) found that damage was caused by low temperatures, frost,

hail, and particularly snow. On the other hand, high temperatures and

drought brought on needle cast and damage to the leaders. The range

of climatic conditions for the growth of P. radiata is thus wide, but

danger of damage from such influences as moisture stress, fungal attack,

or insect activity may increase with deviations from the climatic patterns

shown in Fig. 5.



314



M. RAUPACH



IV.



Soil Factors Restricting Growth



Previous to 1918, the view was held in Australia and elsewhere that

the demands of P . rudiutu could be satisfied by all soils down to the very

poorest. This mistaken idea was responsible for the establishment of

plantations on infertile soils in which growth was either extremely

unsatisfactory or a complete failure. While modern fertilizer practice has

enabled a reasonable forest to be grown on some of these sites, many

problem areas remain where close proximity to timber markets would

make even a modest growth rate an economic success. Soil factors which

restrict growth are those which appear to give a poorer rate of growth

than expected from the terrestrial climate.

The rate of growth of a forest can be expressed mathematically as a

function of many factors. Often some of the factors used are themselves

mutually related. Because of this, even though partial regression procedures which in effect hold other factors constant, may isolate a significant

association between one particular factor and growth, as yet no causal

relationship can be inferred. This is because there still exists a possibility

that the significant factor may be further related to an underlying causal

factor which may not have been examined or even measured. To be certain that a significant association is causal, independent evidence is necessary. Sometimes such independent evidence may come from carefully

controlled experiments; in other cases it may be quite obvious. This

argument does not detract from the use of correlation techniques, but it

points to the caution necessary when interpreting the results of

regressions.

A. LIMITEDVOLUMEOF EXPLOITABLE

SOIL

The volume of soil which is available for root exploration may be

limited by physical or chemical factors.



I . Soil Depth and Stones

P . radiata is frequently planted over a rolling landscape with better

results on the lower sites and valley bottoms than on the higher areas.

There are many reasons for such differences; among these are dissimilarities in genesis which generally make the valley soils more fertile and

greater in profile depth. Of these how important is the depth of the soil

profile? Probably it is important only insofar as it provides ( 1 ) a nutrient

and moisture source of sufficient magnitude and capacity to supply the

demands of good growth and ( 2 ) a secure anchorage against windthrow.

Glasshouse work meeting these conditions can give trees of 6 feet or

more in height in quite small containers.



Pinus radiata



FORESTS



315



In Argentina, Vidal (1961) has reported poor results on soils less

than 18 inches deep, and in South Australia and Argentina a comparison

of soils defined by soil surveys has shown that the growth of P. radiuta

is poorer where the soils are shallow or have impenetrable horizons of

hardpan or concretionary material (Beckmann, 1964; Barrett and Garbosky, 19.60). However, in California trees as high as 60 to 70 feet are

found with as little as 6 inches of surface soil on weathering granite

rubble (Scott, 1960), but roots would penetrate into the parent material

and growth would be very slow.

Jackson (1965) has presented a table for the allocation of different

species to sites at Hawke’s Bay, New Zealand, taking into account rainfall, soil type, and profile depth. On red loams, a rainfall of 35 inches

per annum and a soil depth of 2% feet are required for P. rudiatu. It

would be desirable to examine the relationship between mean annual

increment, depth to the least permeable horizon, and rainfall for P.

radiata in a similar way to Jackson’s study for slash pine ( P . elliottii

Engelm.).

Little is available on the rooting habits of P. radiuta. In California

roots penetrate only to depths of about 2 feet even in good soil, but far

deeper penetrations in clay soils (Bowen, 1964; Raupach, 1967) and in

sands have been found in South Australia. Windthrow is common for

this species on poorly structured shallow soils.

The volume of exploitable soil is sometimes limited severely by stones.

For example as much as 70 percent by weight of some lateritic podzolic

soils supporting P. radiata in South and Western Australia are retained

by a 2-mm. sieve. This is considered further in Section V, D below,



2. Chemical Barriers

The soil water regime will be discussed under Section IV, B, but

reduced conditions and high salt content in localized zones of soil give

rise to barriers which are more chemical than physical. Depressed growth

has been reported on sites with poorly drained heavy clay (e.g., Laughton, 1937; Weston, 1958), root development probably being restricted to

the non-clay layer. Solonetz soils have also been observed to be uncertain sites (Woods, 1955); here the salt content of the clay layer below

the sandy A horizon may be toxic under particular seasonal conditions.

Although clay layers have been said to restrict growth, high quality

trees are commonly observed in parts of Australia where the clay content

is 60 to 90 percent, whereas in Argentina Barrett and Garbosky (1960)

reported an upper limit of about 40 percent in the B-horizon. Clearly a

number of other soil properties should be considered along with clay

content in defining growth limits.



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