Use of a numerical method in determining affinities between some deep sandy soils

Geoderma -- Elsevier Publishing Company, Amsterdam Printed in The Netherlands

USE OF A NUMERICAL METHOD IN DETERMINING AFFINITIES BETWEEN SOME D E E P SANDY SOILS

J. S. RUSSELL and A. W. MOORE Division of Tropical Pastures, C.S.I.R.O., St. Lucia, Queensland (Australia); Division of So~Is, C.S.I.I~O., St. Lucia, Queensland (Australia) {Received August 26, 1966) SUMMARY The application of c o m p u t e r - b a s e d n u m e r i c a l methods and Adansonian concepts shows c o n s i d e r a b l e p r o m i s e in the grouping of c e r t a i n soil units into groups o r s e t s . In this p a p e r r e l a t i o n s h i p s between 43 s i t e s with deep sandy soils s a m p l e d f r o m southern A u s t r a l i a have been d e t e r m i n e d using all v a r i a n t field and l a b o r a t o r y ~lata a v a i l a b l e for the s u r f a c e l a y e r . Information on 28 variant c h a r a c t e r s was available for the soil s u r face l a y e r ( 0 - 8 cm) at t h e s e s i t e s . - T h e qualitative and s e m i - q u a n t i t a t i v e date was ranked and, with the quantitative data, was then standardized (zero mean, unit variance). P r o d u c t - m o m e n t c o r r e l a t i o n coefficients were d e t e r mined between each p a i r o£ soils and a s i m i l a r i t y m a t r i x f o r m e d . Grouping was c a r r i e d out using a flexible s o r t i n g procedure. Additional s t a t i s t i c a l a n a l y s e s of s u b s u r f a c e c h a r a c t e r s and an i n v e r s e a n a l y s i s showing r e l a t i o n ships between c h a r a c t e r s were also c a r r i e d out. F o u r main groups w e r e delineated and these show a geographical patt e r n indicating that the c h a r a c t e r p a t t e r n s on which the affinities a r e based a r e a s s o c i a t e d l a r g e l y with geographical location. Two main c h a r a c t e r c l u s t e r s w e r e found, the f i r s t comprising c h r o m a (wet and dry), iron, exchangeable potassium, manganese, pH and phosphorus; and the second phosphorus, nitrogen, cation exchange capacity, exchangeable calcium, exchangeable magnesium and value (wet and dry). The f i r s t c l u s t e r a p p e a r s to be a s s o c i a t e d with e i t h e r p a r e n t m a t e r i a l or climate, the ~econd with soil organic m a t t e r . The fact that phosphorus i s included in both c l u s t e r s e m p h a s i z e s the important r o l e of S i s element in these soils. Only a v e r y b r o a d relationship existed between vegetation and groups of s i t e s delineated on the b a s i s of soil c h a r a c t e r s . INTRODUCTION The advent of c o m p u t e r s has encouraged the development of m l m e r i c a l methods for the grouping of l a r g e bodies of data into groups o r s e t s and t h e r e has been much i n t e r e s t in the application of t h e s e teclmiques to v a r i o u s fields of biology (Sokal and Sneath, 19~?). TheoreticaLly, the application of some of t h e s e methods to c e r t a i n a s p e c t s of soil and soil-plant r e l a Geoderma, 1, 1967

47

tionships a p p e a r s p r o m i s i n g but in p r a c t i c e difficulties a r i s e . Some of these difficulties a r e due to the anisotropy of s o m e soil bodies (Moore and Russell, 1966). Where anisotropy is not a problem, n u m e r i c a l methods can be applied readily, as has been done for s o i l - d e r i v e d m a t e r i a l s such a s clay m i n e r a l s (Rayner, 1965) and soil m i c r o o r g a n i s m s (Brisbane and Rovira, 1961). Only a few n u m e r i c a l studies on soil bodies "per se" bays been published (e.g. Rayner, 1966; S a r k a r e t a l . , 1966), yet t h e r e a p p e a r to be many situations where n u m e r i c a l methods could be applied profitably. One of these is the grouping of sands. L a r g e a r e a s of deep sandy soils o c c u r in e a s t e r n South A u s t r a l i a in the region bounded by the R i v e r Murray, the coastline and the South A u s t r a l i a --Victoria border. A n u m b e r of land use p r o b l e m s have been encountered on these soils, including t r a c e element deficiencies in plants (Tiver, 1958), animal d i s o r d e r s (Marston et al., 1938), p a s t u r e e s t a b l i s h m e n t dgficulties (Trumble e t a l . , 1938; T i v e r , 1960), and wind erosion in the d r i e r a r e a s (Herriot, 1950). Northcote (1960) classified the deep sands of this region into three main c a t e g o r i e s : (1) sand s o i l s of minimal development (Section designatlor~ Ucl), (2) leached sand soils (Uc2), and (3) sand s o i l s with weak horizon formation (UcS). Soils of the f i r s t category were located mainly n e a r the coast and included c a l c a r e o u s a s well as siliceous sands, those of the s~cond category w e r e situated in the c e n t r a l and southern p a r t of the regior, and those of the third category o c c u r r e d in the n o r t h e r n part. Considering the soil fertility p r o b l e m s of these soils, p a r t i c u l a r l y in relation to t r a c e element content, it is d e s i r a b l e that affinities between m e m b e r s of this broad range of soils be adequately defined. However, mear.ingful gr~mping of these soils on field observation is difficult. The s o i l s have no texture or s t r u c t u r e profile. Profile differentiation is often minimal and of the usual descriptive field c h a r a c t e r i s t i c s only colour shows any r.~a|or variation. To obtain additional information on these soils samplos were taken from virgin sites over a wide geographic a r e a and a l a r g e amount of m o r phological, chemical, and spectrographic data was accumulated. However, p r i o r to the development of c o m p u t e r - b a s e d n u m e r i c a l raethods, these data could not be evaluated a,~ a whole even though information on individual soils or individual p r o p e r t i e s was of value. T h i s paper r e p o r t s the use of ~ n u m e r i c a l method p r o g r a m m e d for a digital c~mputer to define relationsl~2ps between surface s a m p l e s using all variant field and l a b ~ r a t c r y data available. METHODS

During 1958, deep sandy soils (more than 90 cm se ld) at 43 s i t e s were sampled in e a s t e r n South Australia~ The annual rainfall i~:~this region v a r i e s from 25 cm (10 inches) in the north to more t h : a '/5 cm (30 inches) in the south. Mean annual t e m p e r a t u r e s d e c r e a s e from I'I°C (62°F) in the north to 14°C (57°F) in the south. Vegetation supported by these sands v a r i e s in form and s p e c i e s and, from north to south, includes m a l l e e (various Eucalyptus species, 4 - 1 0 m high, with a discontinuous shrub layer), low heath (dense a s s e m b l a g e s of heath-like sclerophyllous shrubs ,and u n d e r s b r u b s l e s s than 1 m high) and tall s c l e r o p h y n o u s f o r e s t (various Eucalyptus species 48

Geoderma, 1, 1967

f r o m 5 to o v e r 15 m high, with a w e l l developed l a y e r of s h r u b s ) (Wood, 1937~ C r o c k e r , 1944; C o a l d r a k e , 1951). At e a c h s o i l s a m p l i n g s i t e taxa p r e s e n t within a r a d i u s of a p p r o x i m a t e l y 15 m w e r e r e c o r d e d . A t a l l s i t e s a 0 - 8 c m ( 0 - 3 i n c h e s ) l a y e r w a s s a m p l e d f r o m a s o i l pit. S a m p l i n g a t l o w e r d e p t h s w a s r e l a t e d to a p p a r e n t p r o f i l e d i f f e r e n t i a t i o n ( b a s e d m a i n l y on colour) and not a t p r e d e t e r m i n e d d e p t h s . Soil s a m p l e s w e r e a i r dried and passed through a 2-ram stainless steel sieve. Textures a n d M u n s e l l c o l o u r d e s c r i p t i o n s of s a m p l e s in wet and d r y condition w e r e d e t e r m i n e d . C h e m i c a l a n a l y s e s f o r total nitrogen, t o t a l p h o s p h o r u s , c a t i o n exc~hange c a p a c i t y , e x c h a n g e a b l e c a t i o n s (calcium, m a g n e s i u m , p o t a s s i u m and sodium) and s o l u b l e c a t i o n s ( c a l c i u m , m a g n e s i u m , p o t a s s i u m and sodium) in the s a t u r a t i o n e x t r a c t ( R i c h a r d s , 1954) w e r e c a r r i e d out on the s u r f a c e s a m I d e s . Soil r e a c t i o n w a s m e a s u r e d u s i n g a 1:5 s o i l : w a t e r s u s p e n s i o n and s p e c t r o g r a p h i c a n a l y s e s for c o p p e r , zinc, m a n g a n e s e , boron, m o l y b d e n u m , coba:~t, iron, a l u m i n i u m and m a g n e s i u m w e r e c a r r i e d out on all s a m p l e s using a Baird 3-m grating spectrograph. TABLE I Means 1 and standard deviations of quantitative characters for 43 deep sandy soils Depth (cm)

Character

Mean

Values from 0 - 8 cm horizons pH Total nitz~)gen (%) Total phosphorus (p.p.m.) Exchange capacity (me/100 g) Exchangeable Ca (me/100 g) w Mg (me/100 g)

6.2 0.032 10 2.62 2.03 0.48

0.6 0.011 7 1.06 0.74 0.24

0.6 0.016 26 1.78 1.17 0.48

0.08 0.08

0.04 0.04

0.07

28.6 0. 035

0.08 2 5 0. 044 0.014 0.004 0.022 2.4 52 22 0.8 2.0 53 24 1.0 2.0 43 20

" "

K ( m e / 1 0 0 g) Na (me/100 g)

Saturation percentage Soluble Ca (me/100 g) Mg ( m e / 1 0 0 g)

0. 021

" K (me/100 g) " Na (me/100 g) Copper (p.p.m.) Manganese (p.p.m.) Boron (p.p.m.)

0. 009 0. 032 2.5 8 20

2.5 0.019 0. 011 0.004 0.0i6 1.2 7 10

Values from depth functions pH Copper (p.p.m.) Manganese (p.p.m.) Boron (p.p.m.) pH Copper (p.p.ni.) Manganese (p.p.m.) Boron (p.p.m.)

6.1 2.5 8 24 6.2 2.5 5 24

0.8 1.1 7 12 1.0 1.1 5 11

"

30

60

Standard deviation -+

1 Geometric means reported for characters other than pH, saturation percentage and soluble K (no transform) and soluble M~ ~md Na (square root transform). Gcoderma, 1, 1957

49

TABLE II Ra"ges for qualitative and semi-quanUtative characters for z.3 deep ~andy soils Depth

Character

Range

(era) Values from 0-8 cm horizons

4

Munsell col(mr (dry) Hue

Value Chroma Munsell colour (wet) Hue

Valu= C!,toma Col~It (p.p.m.) Iron (%) Aluminium (%) Magnesium ('~)

2. 5YR--7.5Y 4--6

0--6 2.5YR--7.5Y

3--5 0-4 <0. 5--2
Values from depth functions 30

Mu~,sellcol(mr (dry) Hue

Value Chroma Cobalt (p.p.m.) Iron (°/~) Alumtnium (%) Magnesium (%) 60

2. 5YR--7.5Y 5--9

0-6 <0. 5-1.1 <0. 5-2 <1--5 <1--2. 5

Munsell col(mr (wet) Hue

2. 5YR--7. 5Y

Value Chroma Cobalt (p.p.m.) Iron (%) Aluminium (%) Magnesium (%)

4--7 1--8 <0. 5--2 <0. 5--2 <1--5 <:~--2. §

F o r the s u r f a c e s a m p l e s information w a s available f o r 31 different c h a r a c t e r s . Means and s t a n d a r d deviations for m o s t quantitative c h a r a c t e r s a r e shown in Table I and r a n g e s for qualitative and s e m i - q u a n t i t a t i v e c h a r a c t e r s a r e shown in Table II. The range for hue (Munsell c o l o u r notation) was 2.5YR to 7.5Y and for n u m e r i c a l a n a l y s i s the values w e r e r a n k e d f r o m 1 to 7. Value and c h r o m a data w e r e used as r e c o r d e d . Some of the s e m i - q u a n t i tative t r a c e e l e m e n t data, e.g., iron, cobalt, a l u m i n i u m and m a g n e s i u m , v,e r e also ranked. Some of the o r i g i n a l data w e r e not used in the n u m e r i c a l a n a l y s i s b e c a u s e of i n v a r i a n c e within the s o i l s s . ~ ; e d . All t e x t u r e s w e r e d e s c r i b e d a s sand and, b e c a u s e of the i n s e n ~ i u v i t v of the s p e c t r o g r a p h i c a n a lyUcal method for zinc and molybdenum, all v~lues for t h e s e s a m p l e s w e r e r e c o r d e d only as < 25 p.p.m, and < 1 p.p.m, r e s p e c t i v e l y . Inclusion of these t h r e e i n v a r i a n t c h a r a c t e r s would not assi st m d e t e r m i n i n g affinities within this group of s~oils since a non-probabilist~c coefficient was used. Values for e a c h c h a r a c t e r used w e r e s~andardize~ (zero mean, unit w r i a n c e ) to 50

Geoderma, 1. 1967

reprove dimensions. A 43 x 28 (soil bodies x c h a r a c t e r s ) m a t r i x of sl=mdard vari~.tes was thus obtained f o r the s u r f a c e samples. In applying n u m e r i c a l a n a l y s i s to a s e t of data a n u m b e r of subjective d e c i s i o n s have to be made including the choice of coefficient of s i m i l a r i t y to be used. A l a r g e n u m b e r of coefficients have been u s e d (Sokal and Sneath, 1963, pp. 125-153) but f o r quantitative data c o r r e l a t i o n coefficient (productmoment) o r m e a s u r e ~ of distance (e.g., Euclidean distance and a v e r a g e d i s tance) a r e commonly used. The f o r m e r r e l a t e s to d i f f e r e n c e s in the p a t t e r n of c h a r a c t e r s found bstween two units (soil s a m p l e s in this instance) while the l a t t e r r e l a t e to differences in the magnitude of c h a r a c t e r s . If two units a r e identical aH coefficients of s i m i l a r i t y will have a value of 100% (or z e r o distance). As d e p a r t u r e f r o m identity o c c u r s , d i f f e r e n t coefficients will tend to indicate different d e g r e e s of s i m i l a r i t y . In this study pattern ("shape") was c o n s i d e r e d to be m o r e s~J.table than magnitude ("size") in d e t e r m i n i n g affinities between units. Thus c o r r e l a t i o n coefficients w e r e calculated for each p a i r of s a m p l e s on the b a s i s of 28 c h a r a c t e r s and a s i m i l a r i t y m a t r i x formed. Clustering was c a r r i e d out using the flexibie s o r t i n g p r o c e d u r e of Lance and Williams (1966) developed f o r the C.S.I.R.O. Control Data 3600 computer. This method involves a h i e r a r c h i c a l s t r a t e g y whereby the d e s i r e d intensity of c l u s t e r i n g can be produced by variation of a single p a r a m e t e r (~) in t h e i r g e n e r a l i z e d l i n e a r function. Grouping i s a g g l o m e r a t i v e and relationships can be Shown in a dendrogram. An i n v e r s e a n a l y s i s of the s u r f a c e sample data f o r the 43 s i t e s was a l s o c a r r i e d out to produce a m a t r i x of c o r r e l a t i o n coefficients showing r e l a t i o n s h i p s between c h a r a c t e r s . Data for most c h a r a c t e r s showed a skewed distribatlon. T h e s e data w e r e n o r m a l i z e d by the u s e of square root or logarithmic t r a n s f o r m a t i o n s . F o r the s u b - s u r f a c e horizons information was available on 11 variant c h a r a c t e r s sampled at various d,..pths. Depth functions w e r e drawn graphically for each of t h e s e c h a r a c t e r s and values were e s t i m a t e d by interp(,~ ~ i o n f o r two depths, viz. 30 and 60 cm. Means and standard deviations for qua .titative c h a r a c t e r s and r a n g e s f o r qualitative and s e m i - q u a n t i t a t i v e c h a r a c t e r s at these depths a r e a l s o shown in T a b l e I and H.

RESULTS The s i m i l a r i t y m a t r i x of c o r r e l a t i o n coefficients obtained using 43 s u r f a c e s a m p l e s and 28 c h a r a c t e r s i s shown in Fig. 1. C o r r e l a t i o n coefficient in the n o r m a l a n a l y s i s is used as a s i m i l a r i t y coefficient and values of --1.0, 0. 0 and + 1 . 0 c o r r e s p o n d to 0, 50 and 100% s i m i l a r i t y . The actual range of values in this p a r t i c u l a r c a s e v a r i e d f r o m --0. 768 to +0. 824 (similarity coefficient range of 12 to 91%). In the s i m i l a r i t y m a t r i x (Fig. 1) the s i t e s have been a r r a n g e d according to the d e n d r o g r a m produced by the sorting p r o c e d u r e used. The r e l a t i o n s h i p s between the 43 s i t e s as d e t e r m i n e d by the flexible sorting p r o c e d u r e (~ = - 0 . 25) a r e shown in a d e n d r o g r a m (Fig. 2). It is obvious that t h e s e s i t e s can be c o n s i d e r e d as constituting ~roups ranging in number from 1 (all sites), to 43 (individual sites). F o u r groups (I-IV) containing 8, 14, 10 and 11 s i t e s r e s p e c t i v e l y a r e used in subsequent d i s Geoderma, 1, 1967

51

5imJlarit-y coefficient (%)

Group I

27 25 24 3~ 33 32 28

mloo

]

[]

gO-gO

~ ] 70-79 EEl 6 0 - 6 9

Group rr

43 361 38 3O

Site No

4 31 37 lg 3 22 1 2 21 20 5

Group ~lI

I

6 23 7

Group ;g'

8 10 11 14 12 9 13 18 15

]

.~.1 .I .Z.!

I: rn 26 27 252434 3332 28352943 3 6 4 0 38 3g 41 30 4 31 31742 tg 3 22 1 2 2120 ~ 6 23 7 8 10 11 14 12 9 13 18 15 17 16 SRe NO

Fig. 1. Similarity matrix for 43 soil bodies ( 0 - 8 cm l a y e r s of deep sands). cussion in this paper. The geographic location of the individual s i t e s and their group membership i s shown in Fig. 3. It should be emphasized that while retattonships o e t w e e n sites have been determined by the sorting procedure used, the number of groups delineated i s subjective. Thus if five groups were required s i t e s 4, ~9, 32 and 37 would be separated from group H, while if three groups w e r e required groups II and HI would be combined. Mean values were calculated for s o m e of the individual characters of the soil bodies in the four groups (Table HI and IV). When distributions are skewed geometric rather than arithmetic means were reported. Since the data 52

Geoderma, 1, 1967

f o r the s u r f a c e s o i l s w e r e used to f o r m the groups, conventional a n a l y s i s of v a r i a n c e cannot be applied to the~l. However, subsoil data w e r e independent of the n u m e r i c a l a n a l y s i s and w e r e analyzed s t a t i s t i c a l l y , probability l e v e l s for significant d i f f e r e n c e s between various subsoil c h a r a c t e r s of the groups being shown in Table HI and IV.

I

'

'

I

|

L -I

Site

26272524343332a83~29433640~413043137,4219 !

!

!

322 !

!

221205623

7 8 101114129 1318151714~ I

i

Fig. 2. D e n d r o g r a m showing r e l a t i o n s h i p s between soil bodies using flexible sorting p r o c e d u r e (~ = --0.25).

The m a t r i x f o r the i n v e r s e a n a l y s i s of 17 p r o p e r t i e s f o r 43 s i t e s is shown in Fig. 4. The c o r r e l a t i o n coefficient in this i n s t a n c e i s used in it~ usual s t a t i s t i c a l s e n s e and the significance of values can be found readily. Only values which a r e significant at P < 0.01 a r e shown in this matrix. C h a r a c t e r s have been o r d e r e d to indicate r e l a t i o n s h i p s between them. Geoderma, 1, 1967

53

34

25O

!

33

~35

0

028

,,oO%

*"

021

.4

020

16"S

! 0~,

\

\/

\ "-~!

Key 0 Group I - ~ Group tr

i

E] Group ]]I

!.63

I

I i

18 Group ~g'

I

/ -.--- Annuat rainfalt 1OO hyets (cm) v. Raitways

9,

i i

I

N

~,

L..

Fig. 3. Geographical distribution of samp~in~ sites. Affinities between surface ( 0 - 8 cm) soil l a y e r s a r e irrJicated by symbols. 54

Geoderma, 1, 1967

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55

TABLE HI Group means I for certain quantitative characters Characters

Statisticxt significance 2

Depth Group (cm) I (8 sites)

H (14 sites)

HI

IV

(10 sites)

(11 sites)

P level,

Total nitrogen (%) Total phosphorus (p.p.m.)

4 4

0.031 35

0.029 13

0.028 3

0.042 11

---

Cation exchange capacity (me/lOOg) Exchangeable Ca (me/100 g) Exchangeabl? Mg (me/100 g) Exchangeable K (me/100 g) Exchangeable Na (me/100 g) pH

4

3.99

1.94

1.87

3.88

--

4

2.76

1.64

1, 77

2.42

--

4

0.91

0.34

0.32

0.67

--

4

O. 18

0.08

0.05

0.07

--

4

0.10

0.06

0.07

0.12

--

4 30 60

6.9 7.1 7.5

6.1 6.1 6.2

6.3 5. 8 6.0

5.8 5. 5 5.4

-O. 01 0.01

4 30

4.4 3.0

3,2 3.3

1.9 2.2

1.7 1.7

-0.05

60

2.8

3.9

2.1

1.5

0.05

4 30

114 35

73 9.4

1.8 4. 4

4.2 3. 5

-0.10

60 4 30 60

19 19 14 16

9.1 11 17 19

4.4 24 29 25

1.3 40 46 43

0.05 9.01 0.01

Copper (p.p.m.) Manganese (p.p.m.)

Boron (p.p.m.)

Ranking and differences 3

I > I~ rri, IV; II ~> IV I ), H, HI, IV; rl ~> IV II, I ~ IV II, I > IV; II > I l I I ;> H, HI, IV; II ~> HI, IV I>IV IV > II, 1; ~I ;> I

IV ) ;11, If, I

1 Geometric means are reported for all characters except pH. 2 Conventional analysis of variance not applicable to surface horizon since data have been used to form groups. Subsurface data analyzed using logarithmic transform. 3 Indicated differences based on P = 0.05 with the exception of manganese at 30 cm.

DISCUSSION T h e r e s u l t s show t h a t an A d a n s o n i a n a p p r o a c h (i.e., all a v a i l a b l e i n f o r mation used) combined w i t h a n u m e r i c a l m e t h o d p r o g r a m m e d f o r a digital c o m p u t e r can be applied to a n u m b e r of soil b o d i e s to obtain g r o u p s . T h e s e g r o u p s a r e b a s e d on o v e r a l l s i m i l a r i t y o r affinity and a r e titus " n a t u r a l " g r o u p i n g s a s defined by Sokal and Sheath (1963), i .e ., they c o n t a i n t h e m a x i mum a m o u n t of i n f o r m a t i o n p o s s i b l e . T h i s a p p r o a c h h a s i n d i c a t e d r e l a t i o n ships w h i c h a r e not obvious f r o m p e r u s a l of t h e r a w d a t a and h a s p r o v i d e d a basis for data reduction. T h e g r o u p s show a g e o g r a p h i c a l p a t t e r n s u g g e s t i n g G ~ t t h e c h a r a c t e r p a t t e r n s on which the a f f i n i t i e s a r e b a s e d a r e a s s o c i a t e d l a r g e l y with geo56

Geoderma, 1, 1967

TABLE IV Group means for Munsell colour p a r a m e t e r s Munsell

Depth Groups

colour

(cm)

notation

I (8 sites)

II (14 sites)

In (I0 sites)

IV (II sites)

7.5YR

7.5YR

10YR

2.5Y

2.~ 35 3.8

2.5 3.7 2.1

4.0 4.1 1.7

4.6 3.1 0.7

10YR

10YR

10YR

2.5YR

3.6 4.9 5.5

3.8 5.6 2.4

3.8 5.8 2.2

4.6 5.3 0.8

10YR

5YR

10YR

2. 5Y

3.5 5.6 5.0

3.1 6.7 3.2

4.1 G. 6 2.5

4.8 6.3 1.4

7.5YR

7.5YR

10YR

10YR

2.6 4.6 5.5

3.2 5.4 4.1

4.0 5.6 3.6

4.2 5.4 2.0

Least significant difference 1 (P = O. 05)

Colour (we0 Hue (MunseH (notation (rank value Value Chroma Colour (dry) Hue (Munsell (notation (rank value Value Chroma Colour (dry) Hue (MunseH (notation (rank value Value Chroma

30

Colour (wet) Hue (Munsen (notation (rank value Value Chroma

60

m

m

1.1 0.8 1.0

1.0 0.7 1.1

1 Conventional analysis of variance not applicable to surface horizon since data have been v s,.d to form groups.

graphical location. Group I s i t e s o c c u r in the northern p a r t of the region (Murray Mallee) and a r e in the 2 5 - 3 8 cm ( i 0 - 1 5 inches) r a i n f a l l zone. Group H and HI s i t e s (with ,'wo exceptions) occur in ~ e c e n t r a l p a r t of the r e g i o n (Upper South East), the f o r m e r in the e a s t and north, the latte~ in the west and souti~ RainiaU in this a r e a i s f r o m 38 to 50 cm (15-20 inches) annually. Group IV s i t e s a r e in the southern p a r t of the r e g i o n (Lower SouthEast) where mean annual r a i n f a l l i s g r e a t e r than 50 cm (20 inches) at a l l sites. J u s t as groupings o! s i t e s can be made on the b a s i s of c h a r a c t e r s , it i s a l s o possible to obtain c l u s t e r s of c h a r a c t e r s on the b a s i s of sites. The i n v e r s e a n a l y s i s (Fig. 4) shows that, f o r the c h a r a c t e r s used, there a r e two main c l u s t e r s and s e v e r a t o t h e r s which show few significant c o r r e l a t i o n s with other m e a s u r e d c h a r a c t e r s . The two main c l u s t e r s beth contain phosp h o r u s which p r o v i d e s a connecting link and shows m o r e significant c o r r e lations than any o t h e r c h a r a c t e r . Geoderma. 1, 1967

57

The f i r s t c h a r a c t e r c l u s t e r contains copper, c h r o m a (wet and dry), iron, exchangeable potassium, manganese, pH and phospho~Js. T h e s e c h a r a c t e r s a r e positively and significantly related to each other, with few exceptions, and they f o r m a c o m p a r a t i v e l y compact c l u s t e r . The highest c o r r e l a t i o n s a r e between wet and dry c h r o m a and between phosphorus and manganese. Other highly significant c o r r e l a t i o n s a r e betwee~ c h r o m a (wet and dry) and iron, manganese and pH respectively, and between copper and manganese. In examining the r e l a t i o n s h i p s between the surface horizons of the soil groups it is found that f o r aH these c h a r a c t e r s group I has higher values than groups If, HI and IV (Table HI). F o r some of these p r o p e r t i e s the diff e r e n c e s p e r s i s t down ~ e profile, e.g., pH, manganese and iron, but in the case of copper t h e r e a r e some differences in the trend with depth. This group of c h a r a c t e r s may be a s s o c i a t e d with e i t h e r a parent m a t e r i a l or a climatic factor. It is possible that there is s o m e relation to rainfall and the intensity of leaching. Thus under the low r a i n f a l l conditions these c h a r a c t e r s a r e at a maximum. With i n c r e a s i n g r a i n i a l l leaching of e l e m e n t s such as copper and manganese a p p e a r s to occur and t h e r e is a reduction in chroma. The second c h a r a c t e r c l u s t e r ~ n t a i n s phosphorus, nitrogen, cation exchange capacity, exchangeable calcium and magnesium, and value (wet and dry). The c o r r e l a t i o n s between these p r o p e r t i e s a r e generally higher tb~n those found in the firs~ c h a r a c t e r cluster. The highest c o r r e l a t i o n s a r e found between cation exchange capacity and nit,-ogen, exchangeable calcium, exchangeable magnesium and value (dry) respectively. The negative c o r r e l a t i o n between the f i r s t five c h a r a c t e r s in this c l u s t e r and value (wet and dry) a r i s e s f r o m the ranking of value from 1 (black) to 8 (white) in the Munsell notation. Reversal of ranking would r e s u l t in positive c o r r e l a t i o n s . The important role of phosphorus in these soils d e s e r v e s some comment. Only trace amounts :~i total phosphorus were found in the surface soil s a m p l e s from some site~. Similar values in the range of 1 to 10p.p.m. phosphorus have been recorded previously in soils from the southern portion of the region (Taylor, 193~; Coaldrake~ 1951). Phosphorus levels in the soil groups a r e in the o r d e r I > H ~ IV ~ III. Thus the lowest phosphorus levels are found in one group of the central region which has rainfall i n t e r m e d i a t e between groups I and IV. P t ~ s p h o r u s follows the trend shown by the charact e r s in the f i r s t c l u s t e r in th~,t the values for group I a r e higher than those for the remaining groups. On the other hand, phosphorus also tends to follow nitrogen in that values for group IV a r e h i g h e r than those for group HI. Thus it might be expected that in the soils at group I sites much of the phosphorus is in m i n e r a l f o r m s w h e r e a s at the sites of group IV it is mainly in organic forms. F o r the c,~aracters in the second c l u s t e r , levels in groups II and HI c o u t r a s t with those in groups I and IV. It is noteworthy that higher rainfall at the s;ites in groups II and HI as c o m p a r e d with the sites f r o m group I has not r e s u l t e d in a higher soil nitrogen content. Exchangeable calcium and m a g n e s i u m tend to follow the trend of nitrogen and organic m a t t e r and inc r e a s e at the sites of group IV as compared with groups H and HI even ~hough the intensity of leaching is increased. Exchangeable sodium also exhibit,~ t~his trend but exchangeable p o t a s s i u m does not. The h i g h e r levels of nitrogen, calcium and magnesium at group IV s i t e s suggest that there is a g r e a t e r ammal r e t u r n of organic m a t t e r at these sites r e s u l t i n g in higher ~oil ~evels. The c h a r a c t e r s in the second c l u s t e r a r e obviously related to 58

Geoderma, 1, 1957

that copper deficiency may also o c c u r on these soils. The c o r r e l a t i o n between c h r o m a and copper content points to the possibility of the f o r m e r c h a r a c t e r being u s e d a s an indication of copper level on these soils. Boron deficiency has not been shown on deep sandy soils in this region. It should be noted, howevvr, that the soils of group IV r a v e r e l a t i v e l y high boron contents and it is in t h i s region that m o s t r e s e a r c h has been c a r r i e d out. On the o t h e r har, J the s o i l s of Grcr~p H have low boron contents and the p o s s i bility of boron deficiency on ~ e s e soils should not be overlooked. The t e a - ' sons for the r e l a t i v e l y high boron content of the soils of group IV a r e o b s c u r e but the observed a s s o c i a t i o n of boron and organic carbon in sediments (Eagar and Spears, 1966) s u g g e s t s a possible relationship with organic m a t t e r . Manganese showed the g r e a t e s t r a n g e of any of the t r a c e elements d e t e r mined, varying f r o m l e s s than 1 to 400 p.p.m. The soils f r o m group I showed much higher m a n g a n e s e contents than those from the r e m a i n i n g groups. The insensitivity of the analytical method f o r cobalt, molybdenum and zinc does not allow any m o r e than broad! g e n e r a l i z a t i o n s to 1~¢ made concerning these elements. Cobalt l e v e l s were low and ranged from l e s s than 0.5 to 2 p.p.m., with the lowest values o c c u r r i n g in groups II and IV. Molybdenum and z~nc values were l e s s than 1 p.p.m, and l e s s than 25 p.p.m, respectively for all soils. Information on the vegetation s u r r o u n d i n g each site was recorded. F l o r i s t i c composition (nomenclature as in Black, 1957) is shown (Table V) in relation to the groups f o r m e d on the b a s i s of soil c h a r a c t e r s . It can be seen that sites f o r m i n g two of the groups (I and IV) have no taxa in common. However, s i t e s f r o m groups I, H and HI and from groups H, HI and IV have common taxa. N o single taxon was p r e s e n t at all sites of one group cnly and yet was r e s t r i c t e d to this group, although Pter~lium aquilinum approached this situation ~ being r e s t r i c t e d to group IV sites Jonly and being r e c o r d e d at 9 of the 11 sites in this group. The r i c h n e s s of the vegetation as indicated by the n u m b e r of taxa p r e s e n t was l e s s for the sites in groups I and IV than for the sites in groups H and HI. None of the commonly recognized heath s p e c i e s was p r e s e n t at the s i t e s of group I but th£re appears to be no general r e l a tionship between heath vegetation and the soil p r o p e r t i e s measured. Thus heath vegetation, with all species le~s than 1 m in height, was recorded at 7 sites: t h r e e in group II and two in ~ach of groups HI and IV. It is evident that a n u m e r i c a l method can be used to obtain groupings of soil bodies on the b a s i s of field anti laboratory m e a s u r e m e n t s (characters) and also to obtain groupings of these m e a s u r e m e n t s on the basis of soil bodies. However, as L a m b e r t and Dale (1964) h~ve pointed out, investigations of this nature provide a b a s i s for the erection of hypotheses, the testing of which r e q u i r e s the collecticn of m o r e data. Alternatively, in some instance~ previously postulated hypotheses could be tested. In e i t h e r case, n u m e r i c a l analysis only r e v e a l s i n t r i n s i c r e l a t i o n s h i p s already p r e s e n t in the data under examination. F r o m this it follows that studies of this type must be i t e r a t i v e in nature and the function of the initial survey is to establish a broad pattern. In this initial study four main groups of deep sandy soils have been defined in this region. Two of these groups (I and IV) a r e d i s c r e t e in r e l a tion to many soil c h a r a c t e r s and vegetation. The other groups (H and HI) show a tendency to overlap in some soil c h a r a c t e r s and vegetation. Of the soil c h a r a c t e r s studied the r e l a t i o n s h i p of colour to a n u m b e r of other 60

Geoderma, I, !967

organic m a t t e r level. The inclusion of p h o s p h o r u s in tb.is c l u s t e r s u g g e s t s tnat the lov¢er organic m a t t e r content for group H and IlI s i t e s (annual r a i n fail 3 8 - 5 0 cm) c o m p a r e d with group I s i t e s (annual rainfall 2 5 - 3 8 cm) may be due to the lower levels of phosphorus found in the f o r m e r g r o u p s . Cobalt, boron and exchangeable sodium show few significant c o r r e l a tions with o t h e r c h a r a c t e r s , i.e. the p a t t e r n of o c c u r r e n c e of t h e s e c h a r a c t e r s is r e l a t i v e l y independent of o t h e r c h a r a c t e r s m e a s u r e d . Boron Jalues a r e h i g h e s t in group IV s i t e s and in this r e s p e c t the t r e n d is s i m i l a r to nitrogen although o v e r a l l the two c h a r a c t e r s a r e net significantly r e l a t e d . The only significant c o r r e l a t i o n of t h i s e l e m e n t is with value (wet). Cobalt shows a positive significant c o r r e l a t i o n with iron. Exchangeable sodium shows sig-' nificant but low c o r r e l a t i o n s with cation exchange capacity and exchangeable calcium and m a g n e s i u m . The r e m a i n i n g c h a r a c t e r s u s e d to f o r m the groups show few or no significant c o r r e l a t i o n s with o t h e r c h a r a c t e r s and w e r e consequently not included in Fig. 4. Of t h e s e c h a r a c t e r s hue, shows a significant negative c o r r e l a t i o n with chroma, and s a t u r a t i o n p e r c e n t a g e a significant positive c o r r e l a t i o n with total n i t r o g e n . "Whilst soluble cations show s o m e significant c o r r e l a t i o n with each o t h e r they w e r e not significantly r e l a t e d to other characters. T r e n d s of c h a r a c t e r s in r e l a t i o n to depth v a r y . Thus at the s i t e s of group I pH i n c r e a s e s with depth, t h e r e is little change at the s i t e s of groups II and HI, and pH d e c r e a s e s with depth at the s i t e s of group IV. Copper levels d e c r e a s e with depth at the group I s i t e s and i n c r e a s e with depth at the group II sites, while t h e r e is little change for g r o u p s III and IV. T h e r e is a tendency for m a n g a n e s e values to d e c r e a s e with depth at s i t e s from g r o u p s I and IV and i n c r e a s e at s i t e s f r o m groups II and III. However, in spite of differences between g r o u p s in the t r e n d of c e r t a i n c h a r a c t e r s with i n c r e a s i n g depth, the o v e r a l l p a t t e r n for m e a s u r e d c h a r a c t e r s in the s u b - s u r f a c e h o r i z o n s i s s i m i l a r to that found in the s u r f a c e . Two s i t e s included in group II did not fit into the geographic pattern. The soil f r o m site 19 was a c a l c a r e o u s sand w h e r e a s all other s o i l s w e r e siliceous. The soil was included in group II but it was the last individual site to f o r m p a r t of a group. The soil f r o m s i t e 35 is in the g e n e r a l geographic region a s s o c i a t e d with group I but h a s lower values for many c h a r a c t e r s than have soils at s i t e s of that group. In this study c o r r e l a t i o n coefficient h a s been the index u s e d to d e t e r mine affinity between the u n i t s involved. T h i s coefficient may be c o n s i d e r e d a p a t t e r n coefficient as opposed to a magnitude coefficient. N e v e r t h e l e s s the groups f o r m e d on the b a s i s of this coefficient, and thus of s i m i l a r i t y of pattern, a l s o show s i m i l a r i t i e s in magnitude a s f a r as the individual c h a r a c t e r s a r e c o n c e r n e d . This s u g g e s t s that for t h e s e p a r t i c u l a r soil b o d i e s t h e r e is a r e l a t i o n s h i p between p a t t e r n and magnitude. Whether such a r e l a t i o n s h i p is likely to exist for soil bodies g e n e r a l l y i s not known. The study has e m p h a s i z e d the low content of some of the t r a c e e l e m e n t s i m p o r t a n t for plant growth which a r e found in these soils. T h i s is p a r t i c u l a r l y so for copper, and d e f i c i e n c i e s for plant growth have been r e c o r d e d in soils which a p p e a r s i m i l a r to those of g r o u p s llI and IV (Tiver, 1956). The a n a l y s e s show that the s o i l s in these groups have a lower m e a n copper content than the soils of g r o u p s I and II. N e v e r t h e l e s s the o c c u r r e n c e of some s o i l s in the n o r t h e r n p a r t of the region with low copper contents s u g g e s t s Gcoderma, 1, 1967

59

TABLE V Species or g e n e r a r e c o r d e d at each siteX _

_

~

~

Taxon

Site ~~...

Group I 26

27

25 ,.

CheeI

Casuarina muelle~ian~ Miq. Callitris spp. Baeckea botzriz (Schlect.)F.v.M. Melaleuca spp. Eucalyptus incras,~ata Labill. Acacia spp. Hibbertia sp. Baecleea crassifoUa LindL Casuarina pusilla lVlackltn Lepidosperma sp. Astroloma sp. Adenanthos termitwlis R. B r . Leptospermum m y~ sinoides

,

X 0 0

Myoporum platycarpum R. B r . Eucalyptus leptophylle F.~.M. Triodia irritans R. B r . Leptospermum coriac~um (F.v.M.) O X

O O

X O

Scl'decht

Casuarina sp. Eucalyptus diversifolia Bonpl. Isopegon ceratophyllus R. Br. Leuccpegon costatus F.v.M. Ban#sia ornata F.v.M. Xanthorrhoea australis It. B r . Eucalyptus baxteri (Benth.) Maiden et Blakeley

Banksia marginata C a r . Eucalyptus fasciculosa F.v.M. ~leridium aquilinum (L). Kuhn

Leptospermum juniperinum Sm. Casuar/na striata Macklin Eucalyptus viminaUs Labill. Total 2

4

Maximum heigh,* of vegetatlon(m)

9

5

5

Mean annual rainfall (cm)

28

30

28

5

i X = o c c u r s at 50~ o r m o r e of sites within a g 2 Includes taxa f o r which only one oco'~rrence

:h site1 Group I

26

27

25

24

,,

X 0 0

33

34

X 0

X

X

0

0

0

0

X

32

X

28

,

0 0 X

X 0

0

0 X 0

X

X

X

0 X

5

5

4

3

5

4

0

X 0

4

$

9

5

5

6

5

8

5

4

28

30

28

30

28

30

33

36

4tes wl~hin a group; 0 - o c c u r s a t l e s s ! , ocr'~rrence ~

r e c o r d e d ~n o v e r a l l s u

Group 1I

35

29

43

36

0 0 0

38

39

0

41

30

4

31

0 0

0 0

0 0

40

0

~) 0

0 0

0

0 X 0 0 0 X

X 0 0 X

X

X

X

0

0

0 0 X

X

X 0 0

X 0

0 0 O

X 0

X

~

X

X

X

O O X X

0 O

O X X

X X

O X X

X X

X X

0 0

0

G

7

6

8

7

7

8

8

7

3

8

6

2

5

2

4

3

1

4

5

1

1

30

38

38

43

43

46

43

43

43

46

43

than G0% of s i t e s within a group. ~ey.

Group HI 41

30

4

0 X

X

0

0 0 X

31

37

42

0 O

0

0 0 0

19

X

3

0

0 0 0

0 X

X

I

0 0

0 0

X

22

0 0

X

0 0

X

0 X

0

X

X X

X X

0 0 X X

0 0 X X

X

0

0

X

0

X X

X X

O O

8

7

3

8

8

7

7

7

§

8

4

5

I

I

O

§

4

9

I

I

43

43

46

43

43

43

64

46

46

4:

Group ]]5 3

22

1

2

21

20

0

0 0

5

6

25

7

0 0 0

0

0 0

0 0 X

0 X

0

0 X 0

X

X

0

X

0 X

X X

X X

0 X 0

X X

X X

X

X X

X X

X

X 0

X 0

X

0

X X

X X X 0 0

7

5

8

5

5

6

6

6

4

10

9

1

1

5

2

3

8

8

3

8

46

46

43

43

46

48

46

48

46

51

pp. 61-66

Group IV 8

10

11

14

12

9

13

18

X

X

0

0

15

17

16

0 0 X

0 X

0 X

X

X

X

0 0

X 0

X

X

X

X

X

0

X

X O O

X

X

X

X

X

O O

O

O

O

3

5

8

5

2

3

5

3

3

3

2

8

9

6

9

9

9

l

1

12

13

9

51

56

61

74

71

56

71

74

81

79

76

c h a r a c t e r s i s of i n t e r e s t . B o t h c h r o m a a n d v a l u e would a p p e a r to h a v e p r e d i c t i v e v a l u e in t h e s e s o i l s , t h e f o r m e r in r e l a t i o n to c o p p e r , e x c h a n g e a b l e p o t a s s i u m , m a n g a n e s e and pH a n d t h e l a t t e r in r e l a t i o n to e x c h a n g e c a p a c i t y an¢~ e x c h a n g e a b l e c a l c i u m a n d m a g n e s i u m .

ACKNOWLEDGEMENTS

T h e d a t a u s e d in t h i s p a p e r w a s o b t a i n e d w h i l e one of u s ( J . S . R . ) w a s e m p l o y e d by the South A u s t r a l i a n D e p a r t m e n t of A g r i c u l t u r e . T h e a s s i s t a n c e of M r . N. S. T i v e r in the s e l e c t i o n of s i t e s , t h e s a m p l i n g of s o i l s , and t h e i d e n t i f i c a t i o n of p l a n t s is g r a t e f u l l y a c k n o w l e d g e d . M o s t of the w e t c h e m i c a l a n a l y s e s w e r e c a r r i e d o u t by t h e South A u s t r a l i a n D e p a r t m e n t of C h e m i s t r y . T h e s p e c t r o g r a p h i c a n a l y s e s w e r e m a d e by t h e A u s t r a l i a n M i n e r a l D e v e l o p m e n t L a b o r a t o r i e s , A d e l a i d e , South A u s t r a l i a . T h e a u t h o r s w i s h to a c k n o w l e d g e t h e p e r s o n a l i n t e r e s t t a k e n by D r s . G. N. L a n c e and W. T. W i l l i a m s , C o m p u t i n g R e s e a r c h S e c t i o n , C . S . I . R . O . , in t h e a p p l i c a t i o n of g r o u p i n g p r o c e d u r e s to s o i l d a t a .

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