The peat soils of the Auckland Islands

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The peat soils of the AucklandIslandsM. L. Leamy a & L. C. Blakemore aa N.Z. Soil Bureau , Alexandra and WellingtonPublished online: 12 Jan 2012.

To cite this article: M. L. Leamy & L. C. Blakemore (1960) The peat soils of theAuckland Islands, New Zealand Journal of Agricultural Research, 3:3, 526-546, DOI:10.1080/00288233.1960.10426636

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526 NEW ZEALAND JOURNAL OF AGRICULTURAL RESEARCH (JUNE

THE PEAT SOILS OF THE AUCKLAND ISLANDS

By M. L. LEAMY and L. C. BLAKEMORE, N.Z. Soil Bureau, Alexandraand Wellington.

(Received for publication, 11 March 1960)

Summary

This paper contains a description of the peat soils on part of theAuckland Islands which lie in the South Pacific Ocean approximately~WO' miles south of New Zealand. Peat forms a blanket over the surfaceof the Islands and is the parent material of most of the soils. In thearea examined in detail the average thickness of the peat blanket wasapproximately 6 feet. A fossil soil horizon in the peat was dated by theradiocarbon method as 6290 ± 110 years before present. This istentatively correhted with the post-glacial thermal maximum periodany by applying the chronology established elsewhere for this period it isconcluded that the blanket peats of the Auckland Islands beganaccumulating at least 40DO years ago. A thickness of from 2 to6 feet of blanket peat has been built up in this time. The peat blanketis discussed with regard to origin and development, decompositIOn,movement and erosion, the underlying mineral material, animalcontributors and chemistry.

INTRODUCTION

The Auckland Islands consist of one large and five smaller islandsand lie between 500 26' and 50 0 56' S. latitude and 165 0 52' and1660 22' E. longitude. The main island covers 179 sq. miles. AdamsIsland, the second largest, 31t sq. miles in area, lies to the south and isseparated from the main island by Carnley Harbour. The total areaof land covered by the group is 220 sq. miles (Fig. 1).

The islands are composed largely of basic volcanic rocks whichwere erupted from two main vents, one near Disappointment Islandand the other at Carnley Harbour (Falla 1948). Marine erosion onthe wind-swept west coast is rapid and in some places the western coastline has been cut back almost to the east-west divide. The east coastof the main island, with its drowned indented shoreline providing aseries of fine harbours, stands in striking contrast to the high steep cliffson the west.

The climate is not rigorous, but high humidity, persistent lowcloud obscuring the sun, and frequent high winds give it a subantarcticcharacter (Falla 1948). Most of the surface of the islands, even steepslopes, is covered with a blanket of deep peat. This peat blanket wasstudied by a pedologist who was included in an expedition whichtravelled to the Auckland Islands on HMNZS Tui in November1954. A map of the islands showing the route taken by the Tui is shownin Fig. 1. The expedition spent only 8 days on the Islands. Detailedpedological observations were confined to the immediate vicinity ofRanui Cove, and, more particularly, the area between the camp and theLookout, a wartime coast-watching station situated on a plateau 180 ftabove sea level and about half a mile north-west of the camp (Figs. 1, 2).

NZ. J. agric. ReS. 3: 526-546

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Physiography

Most of the 220 square miles of land surface of the AucklandIslands is covered with peat. During the eight days spent on theislands the only peat-free areas observed were rock outcrops andapproximately 20 acres of sandhills behind Sandy Bay on EnderbyIsland. The rock outcrops, which appeared to be lava flows, giverise to small screes. Apart from these screes no obvious erosion scarswere observed on any of the islands, although the hummocky surfaceof the peat on hilly and steep slopes might indicate a downhill movement. In the vieinity of Port Ross, between Ranui Cove and TuckerPoint, the peat-covered surface terminates abruptly in cliffs up to 15 fthigh, but there seems to be a tendency for the peat to flow over theedge of the low cliffs and to produce an even slope down to the water'sedge.

The main island is drained by small streams, most of which flowin broad V-shaped gullies. The water in the streams flowing intoRanui Cove is stained dark brown by dissolved organic matter andappears to carry little material in suspension.

Vegetation

The plant associations growing on the peat may be divided intothree broad groups.

Fig. 3.~A section of the track to the Lookout, Ranui Cove. Tussock(D. antarctica) in the foreground, scrub (mainly Dracophyllumand Suttonia) in the middle background and rata forest in

the far background.

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1. Southern rata (Metrosideros umbellata) forest occurs In abelt around the coast, extending about a quarter of a mile inland.On exposed sites trees are stunted and deformed but in shelteredplaces individual trees attain a height of up to 30 ft. (Fig. 3). Underrata forest the ground is covered with a close mat of moss, liverwortsand lichens, which makes a very slippery surface (Fig. 5). Isolatedpatches up to 2 in. thick of dead rata leaves lie on the surface. Associatedtrees and shrubs include several species of Coprosma, the haumakoroa(Nothopanax simplex), the inaka (Dracophyllum longifolium) , andSuttonia divaricata (Cockayne 1927).

Fig. 4.-Dense vegetation conslstmg of mainly Suttonia, Dracophyllum,and rata in the vicinity of Ranui Cove.

2. Above the forest line there is a dense vegetation of rata andscrub in which Suttonia divaricata is dominant. It is associatedwith stunted rata, inaka, and several species of coprosma (Fig. 4).

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532 NEW ZEALAND JOURNAL OF AGR1CULTURAL RESEARCH (JUNE

Fig. 5.-Section through the top horizons of profile 4. Note the mossliverwort-lichen mat on the surface.

3. A mixed association of tussock grassland, consisting mainlyof the large tussock (Danthonia antarctica) and various herbaceousplants, is dominant at higher altitudes. Its lower limit varies fromabout 300 ft above sea level in the north to about 100 ft above sealevel in the south (Fig. 6). In the north, patches of D. antarctica andthe subantarctic poa (Poa litorosa) occur interspersed among the rataforest and scrub associations at altitudes lower than 300 ft.

In detail this vegetation pattern is a mosaic. Thus althoughthe plateau upon which the Lookout is situated lies within the ratascrub zone, it supports an association consisting mainly of Oreoboluspectinatus and Gaimardia ciliata, with some stunted rata and tussock(D. antarctica) (Moar 1958 p.452).

The PeatIn order to study the relationship between the peat blanket and

topography, a transect was selected (Fig. 2) which traversed a variety

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19(0) LEAMY AND BLAKEMORE-PEAT SOILS 533

of slopes from the Lookout plateau to the lowland approximately 100 ftbelow. Eight sites were examined, and the observations are summarisedin Fig. 2. The section along this transect line shows that a layer ofpeat with an average thickness of approximately 6 ft overlies rock onall slopes. Depths recorded by Moar show appreciable thickening ofthe peat to about 23 ft on the flat platcau top (site 1) and to about15 ft in a depression on the lowland below (site 7).

Fig. 6.-Adams Island from Carnley Harbour. The rata and scrub atlow levels give way to tussock with increasing altitude.

Full profile descriptions at sites 3, 4, 5, 6, and 8 are given inAppendix 1. These sites were also sampled for chcmical analyses andthe results are given in Table 2.

In all profiles studied in detail some mineral material lay betweenthe peat and the underlying rock (see also Moar 1958 pp. 458-9). Atsite 3 there was i to 1 in. of very dark grey peaty loam at 71 in. At site4 the peat was slightly loamy at 66 in.; at 72 in. there were dark brownto brown patches of peaty loam which merged with increasing depth intodark brown to very dark brown peaty loam. At site 5 a 12-in. layerof very dark brown loamy peat was identified at 40 in. At site 8,lOin. of brown to dark brown silt loam was found under 36 in. ofpeat. This mineral horizon is distinct both in colour and texturefrom the overlying peat and lies immediately beneath a horizon ofstrongly decomposed black peat which differs markedly in colour anddegree of decomposition from the peat higher in the profile (Fig. 7).

A striking feature of all the profiles examined was their unexpecteddryness. Four pits were dug on slopes of 1°,43°, 6°, and 17° and wereleft open for periods of up to 24 hours. Ground water did not run

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Fig. 7.-Peat and underlying mineral soil exposed in a small cliff.The declivity of the cliff has been reduced by peat sliding overthe edge--the white line marks the top of the cliff. The stonesimbedded in the peat to the right of the spade are thoughtto have been deposited there by waves during storms.

into any of them. Two feet of water collected in the bottom of onepit that was left open overnight, but heavy rain fell during the nightand the pit was in a position to collect surface run-off. Furthermore,water disappears quite rapidly from the surface after rain. Eighthours after a period of heavy rain which lasted for 24 hours, the surfaceunder rata and scrub was in the same condition as it had been beforethe rain i.e. moist and slippery but not wet-no pools of water layon the ground.

In every profile described in detail the degree of decomposition ofthe peat in the major horizons was estimated according to a field scale(D1-DlO) following that used by von Post (1937) and based on anestimation of the amount of organic colloids present. Nowhere was therefound a state of decomposition greater than D6, i.e. strongly decomposed.

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Profiles 5 and 8 were the only two in which rock was exposed beneaththe peat and in both cases the lowest organic horizon of reddish-blackto black peat was determined as D6.

DISCUSSION

Origin and Development

The dominance of peat formation throughout the AucklandIslands under various plant communities and on a wide range of slopessuggests a climatic cause.

Rainfall is high and temperatures are low, the estimated meanannual rainfall over the group being 70-75 in. and the mean annualtemperature 46°F. The high mean relative humidity (87%) andthe high mean cloud cover (8.9), allied to the low atmospherictemperatures, must result in a low rate of evaporation from the soil.On Chatham Island Wright (1959) suggested that salts blown inlandfrom the sea had assisted peat development through retardation ofplant decomposition. This suggestion may equally well apply to theAuckland Islands where large amounts of cyclic salt would be expectedin the rainfall.

Aston (1909) concluded from his observations on their moisturestatus that the soils of the Auckland Islands, considering that theyreceive a daily or almost hourly rainfall, are naturally well drained.The following observations support this conclusion:

(a) the relative dryness of the top horizons.

(b) the distinct change in the depth of the peat and in the natureof its vegetative cover on sites that are naturally poorly drained.Two such localities were observed (Fig. 2, sites 1 and 7).In both these places features such as depressed margins andraised centres suggest raised bogs or convex basin peats (Moar1958, p. 459). At both these sites the vegetation consists of anassociation of tussock grassland and herbaceous plants.

(c) the relatively rapid disappearance of surface water from theground after rain (p.533).

Apart from the higher parts of some raised bogs, intrazonal peatdeposits are invariably slow draining.

Climate would thus appear to be the dominant factor in peatformation in the Auckland Islands, blanket peat being the zonal soilof the region. Variations are due mainly to the intrazonal influenceof topography which may produce a local accumulation of groundwater and a consequent thickening of the peat blanket.

Decamposition

Field observation on the peat soils of the Auckland Islands suggestthat they are not, in general, strongly decomposed. The moderatelylow D numbers, which are a measure of the organic colloidal materialpresent, and the fact that in most horizons there are recognisableplant remains, provide the main field evidence for this conclusion.Chemical evidence is not so conclusive. All the horizons analysed have

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very high values for cation-exchange capacities (112 to 233 me.%),probably indicating strong decomposition. However, this is by nomeans certainly established on the basis of these figures alone, for theredoes seem to be a correlation between strong acidity and high cationexchange capacity. In intrazonal peats of the North Island of NewZealand, strongly acid peats generally have higher cation-exchangecapacity and lower base-saturation figures than less acid peats. TheAuckland Island peats are extremely acid (pH range 3.7 to 4.6) andhave low base-saturation figures (440/0 to 19%).

All the profiles examined in detail were developing under apparentlypredominantly aerobic conditions with humification probably thedominant process of decomposition. The high C IN ratios (46-68)for all samples, except 6638 A-D which are discussed later, suggestthat if humification is an active process it is not very effective, possiblybecause the parent material of these peat soils is supplied by predominantlywoody plants and probably contains a high proportion of substanceswhich are relatively resistant to decomposition. Furthermore, it ispossible that in profiles occupying well-drained positions (e.g. profiles3, 4, and 6) eluviation and subsequent downslope flushing have removeda considerable amount of the colloidal products of humification, leavingresistant residues which have relatively high C/N ratios and relativelylow D numbers.

It seems probable that anaerobic conditions exist in the lowerhorizons of profiles 1 and 7 which are situated on small raised bogs.The vegetation, structure, and position in the landscape of these raisedbogs suggest an abnormal accumulation of ground water. The slowingdown of decomposition because of anaerobic conditions has led to arelative increase in accumulation and a consequent thickening of thepeat blanket in these localities.

Marked profile differentiation was seen in two profiles (Nos. 5and 8). In profile 5 a reddish black horizon of strongly decomposed,friable, greasy peat with a high C/N ratio (59) and a very high cationexchange capacity (233 me. %) occurs at approximately 2 ft below thesurface. The upper horizons are very weakly to moderately decomposedand have slightly lower cation-exchange capacities (112, 191 me. %)although there is little difference in C IN ratios (58, 46). In profile8 the lowest peat horizon about 2 ft below the surface consists ofblack, soapy, -strongly decomposed peat with a relatively low C/Nratio. The upper horizons of this profile also have low C/N ratios,the reasons for which are discussed later. This lowest peat horizonin profile 8 has been dated by radiocarbon method at 6290 -+- 110years before present (Messrs Fergusson and Rafter, pers. comm.). Thisindicates that the marked profile differentiation in these two profiles iscaused by the presence of a fossil soil buried by 2 to 3 ft of more recentpeat. The peat in the fossil soil horizons is strongly decomposed becauseit is older than the overlying peat and because, in all probability, itwas formed under a warmer climate. Profiles 3, 4 and 6 show littleprofile differentiation apart from colour changes.

Movement and ErosionAston (1909) observed evidence of bog slides on the Auckland

Islands and noted seveml fresh scars, particularly around Carnley

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Harbour, which he attributed to this form of erosion. No recognisablescars were seen during the 1954 expedition, but the following evidenceindicates that the peat does move down slope:

(a) the steep slope on which the section was located at theObservation Spot, Port Ross, is broken by several undulations.The largest of these takes the form of a depression with a distinctmound at the outside edge (see profiles 5 and 6, Figure 2).There is an appreciable thinning of the peat in the depressionbehind the mound, and a thickening on the mound itself. Thisfeature may have been caused by a small peat slide checkedperhaps by a dense growth of forest. There appeared to be.no thinning of the peat on the steep slope behind the depressionand in fact shallow profiles were recorded only immediatelybehind the mound. If the peat is constantly moving downslope the scar caused by this peat slide on the steep slopeimmediately behind the depression could have been healedfrom the slopes above and only on the gentle slope of thedepression behind the mound are the effects of the slide stillnoticeable.

(b) In many places along the stretch of coast between Ranui Coveand Tucker Point the peat almost completely covers the faceof a low cliff (Fig. 7) .

It is apparent from (a) that in addition to slow flow the peatblanket is subject to rapid slides. These appear to take place onsteep slopes where the slow down-slope movement of the peat isimpeded by vegetation. The peat builds up behind the obstructionuntil the increasing weight overcomes the barrier and a small landslide occurs. Thus slow movement of peat down-slope, acceleratedoccasionally by a rapid slide, is the major process of erosion operatingon these soils.

It would seem that two processes are affecting the surface levelof the peat. Creep and slides are lowering the surface; and densevegetation and slow decomposition are adding to the peat deposits. Thelatter process is more effective than the former with the result that thepeat deposits and the land surface in general are building up at thepresent time.

Nowhere in the Auckland Islands was any evidence seen thatwould indicate the degeneration of the peat by the natural developmentof cracks or channels, and consequent erosion, as has been observed onsome Northern Hemisphere blanket peats (Fraser 1933).

Underlying Mineral Material

In all the profiles described in which rock was reached, a horizonwith high mineral content was encountered immediately above therock. As described in Appendix 1, the mineral horizon ranges froma few inches of black loamy peat to lOin. of brown to dark brownsilt loam. This material may possibly be derived from the weatheringof rock outcrops in the uplands and carried down in the peat. However, the fine texture of the material and the well defined nature ofthe horizon does not support this view. In the high-moor peats of

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Macquarie Island, which are from 3 to 5 ft thick, mineral matter occursboth evenly distributed throughout the peat and also as a distinct,sharply defined horizon. The evenly distributed material is consideredto be derived from landslips (Law and Burstall 1956).

Alternatively, it is possible that this mineral material is beingweathered at present from the basalt underlying the peat, but the datingof the peat horizon immediately above the 10 in. of silt loam in profile8 at 6290 -+- 110 years suggests that these two horizons represent afossil soil, and that the silt loam was weathered from the basalt beforethe accumulation of the present blanket peat. Such a soil woulddevelop under warmer conditions than at present prevail in the AucklandIslands. The date of 6290 -+- 110 years suggests a correlation with thepost-glacial thermal maximum period which has been dated by Horberg(1954, quoted by Stevens 1956, p.227) as 7000 to 4000 years ago.The date obtained from the Auckland Islands may not mark theclose of the thermal maximum because the sample site was an estimated5 ft above sea level and Stevens (1956, p.227) concluded that thehighest sea level attained during the thermal maximum in the HuttValley district was 10 ft above present-day mean sea level, which hetentatively dated as about 4000 years ago. It seems strange that theAuckland Island fossil soil has remained so well preserved if indeed ithas been inundated by a rise of sea level, but in view of the dates obtainedin other parts of the world for the close of the thermal maximum period,this possibility cannot be excluded. By applying the date establishedoverseas for the close of the thermal maximum it would appear thatthe blanket peats of the Auckland Islands are at least 4000 years old.

On the evidence of profiles 5 and 8, where the fossil soil wasdefinitely identified, between 2 and 3 ft of blanket peat have accumulatedin this time, but in profiles 3 and 4, where peaty loam textures are theonly indication of a fossil soil, the evidence suggests that a blanket ofpeat 5 to 6 ft thick has been formed in the present cycle.

Animal Contributors

The Auckland Islands abound in sea lions and oceanic birds suchas penguins, shags, and petrels (Falla 1948, p.142). Many of thesecreatures make periodic contact with the soil either by burrowing intoit, settling temporarily on it or travelling across it, and some of thechemical features of profile 8 and the profile sampled on CampbellIsland provide an interesting example of the effect animal life canhave on soil formation.

The total nitrogen values of samples from these two profiles arevery high and they display lower carbon-to-nitrogen ratios than dothe others. In New Zealand, ratios of 50-60 are usual for acid peats(see Soil Set 110, p.214, N.Z. Soil Bureau Bull. n.s. 5) and comparedwith these the ratios for samples 6638 A-D and 6644 A-C are low for acidpeats and may not express exactly the degree of decomposition. Theymay be partly influenced by an influx of nitrogen from animals and thisview is supported by the following observations:

(a) The samples having lower C IN ratios were taken from nearthe sea where modification by birds and seals could well occur,

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(b) Several soil samples analysed previously, and known to havebeen altered by animal life, have shown similarly low C INratios. Examples are shown in Table 3 and it may be seenfrom these results that:

Sample No. 2976A from Bream Island had a pH of 3.5,a C/N ratio of 13 and contained free nitrate.Sample No. S.B. 6668, a sample collected by Dr Falla fromthe bottom of a petrel's burrow on Ocean Island, AucklandIslands had a pH of 3.3 and while the organic carboncontent was very high, the C/N ratio was kept low (13)by a very high nitrogen content.Sample Nos. S.B. 6663 A, B, C, D, collected by Mr W. T.Ward from Stephens Island, had a top-soil C/N ratio of 11,dropping to 5 further down the profile.

(c) High citric-soluble-phosphorus figures were obtained from thesoils in Table 3 and may be regarded as resulting from animalexcreta. The lower horizons of the soils from site 8 and fromCampbell Island are also higher in phosphorus than are othersamples in Table 2. The mineral horizons of these two profilescontain extremely high contents of citric-soluble phosphorusand it may be that most of the phosphorus from the animalshas passed through the peat to be held by the underlyingmineral material. On the other hand, the extremely highfigures may be due to the naturally high phosphorus content ofthe basaltic parent material of these mineral horizons.

(d) Potassium figures are higher in the lower horizons of profile 8than in those of profile 5 which is to be expected if animalexcreta have been added to the former. The exchangeablepotassium figures in the samples quoted in Table 3 are also high,especially in relation to the other bases present.

Chemistry

Analyses of profiles 8, 5, 6, 3, 4, a sample of calcareous sand fromEnderby Island, and also of a soil sampled at Campbell Islandare shown in Table 2.

With the exception of samples 6638D, 6641, 6644B and 6644C(which are minel'al soils) the samples analysed are peats which havesimilar losses on ignition and which are all extremely acid.

The cation-exchange capacities of the organic layers are all veryhigh and vary considerably. The cation-exchange capacities of themineral horizons 6638D and 6644C are also very high and this isprobably due to the decomposed basalt parent material which can havehigh ion-exchange properties without being strongly weathered, ashas been found by Dr L. D. Swindale (pers. comm.) for soils derivedfrom basalt in Central Otago, N.Z.

Samples 6638 and 6639 were analysed both for exchangeable basesand for bases in the ash. They were chosen for more detailed analysesbecause they afforded interesting comparisons between a coastal profile(Profile 8-6638) and a profile from a higher altitude and further fromthe sea (Profile 5-6639). As well as the probable differences due to

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animal activity, there may be differences caused by degree of exposure tocyclic salt. The results indeed show a marked difference in sodiumfigures-those for the coastal profile being much higher than those forthe inland profile. However, the rise for magnesium, which is usuallyassociated with cyclic salt effect, is not apparent and is possibly beingmasked either by return of magnesium from vegetation or by mixing ofthe peat with the underlying olivine basalt.

It is interesting to note that the increase in calcium and magnesiumin the more strongly decomposed horizon of profile 5 (6639C) is notacompanied by an increase of potassium. The potassium content of thetop horizon is high and it would seem that this due either to leachingof the older material or to a faster uptake and return of this element bythe vegetation.

CONCLUSIONS

In this study, the peats of the Auckland Islands have been treatedas soils rather than as accumulations of plant remains, in the belief thatpedological techniques can add to the understanding of peat deposits.The main conclusions are:

( 1) That blanket peat is the zonal soil of this region.

(2) That the thickness of the peat blanket is approximately constanton all angles of slope from 1° to 43°, with the exception ofpoorly drained flat surfaces or depressions where the development of intrazonal peats produces an appreciable thickeningof the blanket.

(3) That the main processes operating in the zonal soils areaccumulation, aerobic decomposition, and possibly eluviation.

(4) That accumulation of blanket peat is opposed by only weakerosive forces, which is resulting in the land surface of theAuckland Islands being slowly built up.

(5) That the present peat-forming period dates from the closeof the post-glacial thermal maximum period.

(6) That the activities of animals such as birds and seals have considerably affected the chemistry of some coastal soils.

ACKNOWLEDGMENTS

The authors wish to acknowledge the help of the following:Mr N. T. Moar, Botany Division, DSIR, who supplied some of themeasurements of peat depths and also identified many plants.

Officers of the N.Z. Meteorological Service who supplied dataon the climate of the Islands.

Officers and men of HMNZS Tui who provided transport andassistance in the field.

REFERENCES

Aston, B. C. 1909: The Soils and Soil Formers of the SubantarcticIslands. In C. Chilton (Ed.) "The Subantarctic Islands ofNew Zealand". Vol. 2 pp. 745-77. Government Printer,Wellington, N.Z,

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Cockayne, L. 1927: New Zealand Plants and their Story. N.Z. Boardof Science and Art, Manual No.6.

Falla, R. A. 1948: The Outlying Islands of New Zealand. N.z. Ceogr.4(2): 127-54.

Fraser, G. K. 1933: Studies of Certain Scottish Moorlands in Relationto Tree Growth. For. Comm., Lond. Bull. 15.

Horberg, L. 1954: Rocky Mountain and Continental PleistoceneDeposits in the Waterton Region, Alberta. Ceol. Soc. Amer.Bull. 65: 1093-1150'.

Law, P. G.; Burstall, T. 1956: Macquarie Island. Aust. Nat. Antarct.Res. ExPed. Inter. ReP. 14.

Moar, N. T. -1958: Contributions to the Quaternary History of theNew Zealand Flora: 1. Auckland Island Peat Studies. N.Z.].Sci. 1: 449-65.

N.Z. Soil Bureau 1954: General Survey of the Soils of North Island,New Zealand. N.Z. Soil Bur. Bull. n.s. 5.

Stevens, G. R. 1956: Stratigraphy of the Hutt Valley, New Zealand.N.Z. ]. Sci. Tech. B38: 201-35.

von Post, L. 1937: The Geographical Survey of Irish Bogs. Irish Nat.]. 6: 211.

Wright, A. C. S. 1959: Soils of Chatham Island (Rekohu). N.Z.Soil Bur. Bull. 19.

APPENDIX I-DETAILED PROFILE DESCRIPTIONS

Profile 3

Location:Height:Slope:Aspect:Vegeta tion :

Profile:i-I in.

3i in.

8 in.

19 in.

Profile 4

Location:Height:Slope:Aspect:Vegetation:

Profile:2 Ill.

6 Ill.

11 yards NNE of Observation Spot, Ranui Cove.184 ft. above sea level.1,0.NNE.Rata (Metrosideros umbellata)-4 to 5 ft high, stunted;Dracophyllum longifolium-2 to 3 ft high; tussock (Danthoniaantarctica) ; lichen and moss, liverwort.

dark reddish brown (5YR 2/2) peat; D3; plant remains predominantly mosses, liverworts and lichens, many rata roots(living); the surface is covered with a mat of liverwort, moss,and lichen; when this peat is squeezed a little turbid brown waterappears; clear wavy boundary;dark reddish brown (5YR 2/2) peat; D3; plant remains finematted roots and tussock leaves, many rata roots (living);clear smooth boundary;very dusky red (2.5YR 2/2) peat; D3; plant remains rootsand twigs of woody plants (probably rata) and some tussockleaves; gradual irregular boundary;very dusky red (2.5YR 2/2) peat; D2; plant remains largepieces of woody plants black throughout and some tussockleaves.At 5 to 6 ft the peat becomes black (5YR 2/1) and so drythat no moisture was extracted by hand pressure. No recognisable plant remains. At 6 ft the basalt was reached. Thereappears to be "bout! to 1 in. of mineral soil above the rockvery dark grey (5YR 3/1) peaty loam.

About 30' yd NNE of Observation Spot. Ranui Cove.166 ft above sea level.43°NNEMo&~, liverworts, and lichens, Dracophyllum longifolium, Hebeelliptica, Suttonia divaricata, Uncinia sp., rata (M. umbellata).

reddish black (lOR 2/1) peat; D3; abundant roots, plantremains moss, liverwort, dracophyllum; abrupt smooth boundary;very dusky red (2.5YR 2/2) peat; D3; abundant rootsincluding large rata roots; plant remains small roots, medium

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'2.7 m.

30'-36 m.

Profile 5


Profile:4 m.

21 m.

15 in.

12 m.

on

Profile 6


Profile:8 m.

39 m.

on 40 m.

Profile 8

Location:

Height:Slope:Aspect:Vegetation:

roots, and some small woody twigs, friable; diffuse wavyboundary;very dusky red (2.5YR 2/2) peat; D4; many roots; plantremains rata roots and twigs; there are some firm, fibrous, shinywhen broken, veined remains which may be rata leaves; firm;clear smooth boundary;dark reddish brown (5YR 2/2) friable peat; D4; few tomany roots, plant remains woody twigs and roots.At 66 in. the peat is slightly loamy. At 72 in. spots of darkbrown to brown mineral material of peaty loam texture appear.Between 72 and 80 in. this becomes a dark brown to very darkbrown greasy peaty loam. Basalt at 85 in.

About 75 yd NNE of Observation Spot, Ranui Cove.150- ft above sea level.6'°.NNE.Liverworts, moss, Suttonia divaricata, Nothopanax simplex,rata (M. umbellata) , Dracophyllum longifolium.

reddish black (lOR 2/1) peat, fibrous; D3; abundant roots;plant remains sedge-like le:lVes, rata leaves, small roots;very dusky red (2.5YR 2/2) firm peat; D5; many roots;plant remains woody twigs and roots (probably rata) alsosedge-like leaves; large round patches (up to 9 in. in diameter)of a dark reddish brown (2.5YR 3/4) colour throughout thishorizon seem slightly less decomposed (D4); clear smoothboundary;reddish black (10R 2/1) friable greasy peat; D6; few roots;woody branches or twigs the only recognisable plant remains;lighter patches of a very dusky red (lOR 2/2) colour which arefirmer than the matrix, but are more diffuse and less welldefined than those of the above horizon; peat silty at the baseof this horizon;very dark brown ( 10'YR 2/2) greasy loamy peat, massive,sticky, non plastic, contains carbonaceous material includingrecognisable twigs and branches; a discontinous brown (1 OYR4/3) band at the top of this horizon.weathered basalt.

About 90' yd NNE of Observation Spot, Ranui Cove.154 ft above sea level.17°.NNE.Ratel (M. umbellata) , Suttonia divaricata, Dracophyllumlongifolium, moss, lichen.

reddish brown (5YR 2/2) friable peat; D4-5; abundant roots;plant remains small woody twigs and roots;very dusky red (2.5YR 2/2) firm fibrous peat; D4; manyroots; plant remains mostly large red woody fragments (rata);reddish black (lOR 2/1) soft non-fibrous peat containing fewroots and medium and large woody fragments.

At the head of the first bay NNW of Ranui Cove. Profileexposed in cliff section.About 5 ft above sea level.12°.N to NE.Uncinia sp. (a sedge), tussock (D. antarctica) , Hebe elliptica,rata, Dracophyllum longifolium, small ferns, Poa litorosa, moss,and liverworts.

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Profile:2 m.

i- In.

9 m.

17 m.

9 m.

10 m.

on

dead twigs, leaves and bark of dracophyllum tussock, hebeand rata;dark reddish brown (5YR 212) matted roots of small plantsprobably liverworts and moss; clear wavy boundary;very dusky red (2.5YR 2/2) peat; D4; many living roots;plant remains small roots, tussock stems and leaves, woody twigs(probably hebe) -sometimes lighter coloured patches areassociated with the woody material; clear smooth boundary;reddish black (l'OR 2/1) peat; D3; abundant living roots; plantremains a few dead roots unidentified; weakly developed fineand very fine granular structure; abrupt wavy boundary;black (5YR 2/1) peat, slightly silty at the base of the horizon,soapy; D6; abundant live roots; plant remains twigs and smallbranches almost completely carbonised, many small lumps ofcarbon present; irregular smooth boundary; 629'0 ± 110 yearsB.P. by C14 determination (Messrs Fergusson and Rafter,pers. comm.)brown to dark brown (7.5YR 4/2 to 3/2) silt loam; firm;mas~ive with a suggestion of a weak fine granular structure;many dark streaks of carbon mark root channels; manyliving roots; few distinct fine light yellow, greyish greenand red brown spots mark less weathered patches; betweenthis horizon and the one above is a compact layer of hardenedbrown silt loam which breaks out in lumps;dark olive grey and dark reddish brown (5Y 3/2 and 2.5YR3/4) weathered rock (fine grained olivine basalt).

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Documents

The peat soils of the Auckland Islands