MOLLOY: A NEW SCIENTIFIC RESERVE ON THE CANTERBURY PLAINS BANKSIDE - A NEW SCIENTIFIC RESERVE ON THE CANTERBURY PLAINS 47 B. P. J. MOLLOY Botany Division. D.S.l.R., Christchurch SUMMARY: Current surveys, encouraged by the Ne\ Zealand Ecological Society, are showing that a surprising number of native communities still survive on the Canterbury Plains. though in modified form. In 1969 a small area of scrub and grassland with undisturbed soils near Bankside was secured for a scientific reserve - the first of its kind on the Plains. A brief description is given. LOCATIO N Bankside Reserve - a fenced rectangular block of about seven acres - lies between the Selwyn and Rakaia Rivers, and about four miles south- east of Bankside (Fig. I). A "paper" road, Kny- vett Road, forms its eastern boundary and pro- vides legal access from Heslerton Road. Other boundaries ad join farmland held under one title. The altitude is 220 feet above mean sea level. FIGURE 1. Locality map GEOLOGY AND TOPOGRAPHY The reserve is underlain by greywacke fan gravels of the Springston Formation, at one time thought to be of glacial origin (Suggate, 1958), but now interpreted "as an aggradation deposit consequent upon rising Postglacial sea level." (Suggate, 1963). This fan or floodplain, formed mainly by the Rakaia and Selwyn rivers, lies between the younger Postglacial gravels and the older late glacial gravels of the Burnham Forma- tion. The surface of the flood plain, which corres- ponds in age with the Halkett Surface overlying Springston gravels in the Waimakariri sector, has a characteristic, braided channel relief; sand ridges and low, stable sand-dunes, old abandoned stream channels, stony ridges and flattish stony plains are all represented. The reserve includes a section of one of the tallest sand-dunes, a prominent stream channel. and various stony plains and ridges, thus repre- senting a fair cross-section of the local land sur- face. An old established water-race passes through the south-east corner providing an artificial habitat of further interest. SOILS AND CLIMATE Ward et al. (1964) describe the soils. climate and agriculture of this region in detail. Briefly. soils are mapped as Eyre very stony sandy loams (8c) with many small areas of dune soils: (it should be noted, however, that on Sheet 1, Ward et al. (1964), the map unit covering the area including the reserve is incorrectly labelled 8a- Eyre stony silt loam). Within the reserve the Eyre shallow loams and stony loams are confined to stony plains and ridges; whereas the deeper, fine sandy loams of the stable sand-dunes belong to the Paparua series (E. J. B. Cutler, pers. comm.). The work of Cox and Mead (1963). supported by radiocarbon dates, suggests that these soils developed on a surface between 3,000 and 6,000 years old. The free-draining Eyre soils are especially drought-prone and very low in nutrients. Paparu~ soils. on the other hand, retain soil moisture better and generally have a higher content of nutrients (Table I). However, the most importap~ ,ingle factor limiting plant growth on both soils is inado- quate moisture during critical periods.
Transcript
MOLLOY: A NEW SCIENTIFIC RESERVE ON THE CANTERBURY PLAINS
BANKSIDE - A NEW SCIENTIFIC RESERVE ON THE
CANTERBURY PLAINS
47
B. P. J. MOLLOY
Botany Division. D.S.l.R., Christchurch
SUMMARY: Current surveys, encouraged by the Ne\ Zealand Ecological Society, areshowing that a surprising number of native communities still survive on the Canterbury Plains.though in modified form. In 1969 a small area of scrub and grassland with undisturbed soilsnear Bankside was secured for a scientific reserve - the first of its kind on the Plains. A briefdescription is given.
LOCATIO N
Bankside Reserve - a fenced rectangular blockof about seven acres - lies between the Selwynand Rakaia Rivers, and about four miles south-east of Bankside (Fig. I). A "paper" road, Kny-vett Road, forms its eastern boundary and pro-vides legal access from Heslerton Road. Otherboundaries ad join farmland held under one title.The altitude is 220 feet above mean sea level.
FIGURE 1. Locality map
GEOLOGY AND TOPOGRAPHY
The reserve is underlain by greywacke fangravels of the Springston Formation, at one timethought to be of glacial origin (Suggate, 1958),but now interpreted "as an aggradation depositconsequent upon rising Postglacial sea level."(Suggate, 1963). This fan or floodplain, formedmainly by the Rakaia and Selwyn rivers, liesbetween the younger Postglacial gravels and theolder late glacial gravels of the Burnham Forma-tion.
The surface of the flood plain, which corres-ponds in age with the Halkett Surface overlyingSpringston gravels in the Waimakariri sector, hasa characteristic, braided channel relief; sand ridgesand low, stable sand-dunes, old abandoned streamchannels, stony ridges and flattish stony plainsare all represented.The reserve includes a section of one of the
tallest sand-dunes, a prominent stream channel.and various stony plains and ridges, thus repre-senting a fair cross-section of the local land sur-face. An old established water-race passes throughthe south-east corner providing an artificial habitatof further interest.
SOILS AND CLIMATE
Ward et al. (1964) describe the soils. climateand agriculture of this region in detail. Briefly.soils are mapped as Eyre very stony sandy loams(8c) with many small areas of dune soils: (itshould be noted, however, that on Sheet 1, Wardet al. (1964), the map unit covering the areaincluding the reserve is incorrectly labelled 8a-Eyre stony silt loam). Within the reserve the Eyreshallow loams and stony loams are confined tostony plains and ridges; whereas the deeper, finesandy loams of the stable sand-dunes belong tothe Paparua series (E. J. B. Cutler, pers. comm.).The work of Cox and Mead (1963). supported
by radiocarbon dates, suggests that these soilsdeveloped on a surface between 3,000 and 6,000years old.The free-draining Eyre soils are especially
drought-prone and very low in nutrients. Paparu~soils. on the other hand, retain soil moisture betterand generally have a higher content of nutrients(Table I). However, the most importap~ ,inglefactor limiting plant growth on both soils is inado-quate moisture during critical periods.
.18 PROCEEDINGS OF THE NEW ZEALAND ECOLOGICAL SOCIETY, VOL. 17, 1970
TABLE I. Chemistry of Eyre-Paparua soils (con-densed from Ward et al. 1964)
The reserve lies within the subhumid climaticzone and is subject to drying - north~west winds.frequent frosts and summer drought. Althoughfairly evenly distributed. annual rainfall is notlikely to exceed an average of 26in.
HISTORY
This area, like most of the Canterbury Plains,was modified by fire in Polynesian times and wasprobably affected by earlier, natural fires (Coxand Mead, 1963; Molloy, 1968). Subsoils containsubfossil charcoal of kanuka (Leptospermum eri-coides) which indicates that this soil complex wasdominated by kanuka scrub. By applying thechronology established eltewhere (Cox and Mead,1963), it can be assumed that this occurred at least1.000 years ago, and probably throughout Post-glacial times.Scrub and grassland covered the region durjng
the early part of European settlement, with grass-land dominating. This is well documented onBlack Map 51, "North Bank of Rakaia", signedby H. Cridland 1863-65, and deposited in theChristchurch files of the New Zealand Depart-ment of Lands and Survey. Good remnants sur-vive today despite modification by periodic burn-ing and grazing during the last century or rncre.Ward et al. (1964) record patches of matagouri(Discaria foumatou), manuka, tussock and dan-thonia in their soil survey of this region.Hitherto, the native scrub and grassland of
the Canterbury Plains have been poorly docu-mented. Early botanical writers such as Haast,Armstrong. Cockayne. and Wall concluded thatit had all disappeared or was strongly modified.Their accounts are largely reconstructions bas~don a few early records, modified remnams andriverbed successions. The last three writers men-tion patches of scrub in various places on thePlains without actually describing them. Cock-ayne's discussion of "South Island manuka shrub-land" of the "North-eastern' 'and "Eastern" dis-tricts, in fact, provides an approximate descrip-
tion of kanuka scrub at Bankside (Cockayne.1928, p. 193).Contemporary botanists have largely neglected
the Plains, though Connor and MacRae (1968)have described a phase of Nowdanthonia clavatagrassland, an induced community, at Te Pirita onthe high Plains.Until it was subdivided and sold in 1968, this
land had always been used as grazing for drysheep. Originally it was part of Run 108, "HesIer-ton", one of the early Canterbury runs, which wastaken up in 1853 and covered nearly 20,000 acres(Acland, 1946). Like many runs on the Plains"Heslerton" was subdivided into smaller holdingsduring the 1870s and I880s. But the farming pat-tern did not change significantly. Holdings werestill relatively large with individual paddocks con-taining 200-650 acresThe present owners of the surrounding farm-
land are developing the remaining "native coun-try" rapidly, erecting new subdivision fences,yards and buildings, and cultivating or overdrill-ing large tracts of grassland and scrub.
VEGETATION
Four communities are found in the area withtransitions, in places abrupt, in others gradual,depending on site tolerance or degree of modifica-tion. or both. The reserve includes oil four andalthough it does not match the very best examplesof some, it is nevertheless, the best compromiseunder the circumstances. The following brief des-cription applies to the communities in the areaas a whole.
Kanuka scrub
This community consists of small, isolatedclumps and large patches several acres jn area,chiefly on Eyre soils (Fig. 2). It is dominated byreddish and green forms of kanuka of mixed ageand density, ranging from scattered seedlingsthrough plants 2-4 ft. tall. to occasional shrubs12-15 ft. tall. It has regenerated freely after per..iodic fires; the last about 15-20 years ago and oneabout 40 years ago. These estimates are approxi-mate only and based on a few ring counts. Othershrubs are rare. Cyathodes juniperina and anoccasional, sEppressed plant of manuka (Lepto-spermum scoparium) are present. Both haveprobably decreased in numbers with burning andgrazing, and, with manuka, "blight" Eriococcusspp. as well.
MOLLOY: A NEW SCIENTIFIC RESERVE ON THE CANTERBURY PLAINS
In the least disturbed patches the ground layeris rich in bryophytes, lichens and the Jarger fungi.At the base of large kanuka shrubs are deepcushions of Hypnum cupressiforme. Kanukaseems to be spreading into both grassland com-munities judging by the number of seedlings andyoung plants throughout.
FIGURE2. Danthonia grassland in foregroundmerging into short-tussock grassland and kanukascrub. An oblique view across the reserve from
near the gate.
Slwrt-tussock grassland
This community is restricted entirely to Paparuasoils and is the characteristic vegetation of stablesand-dunes and abandoned channels with deep,fine sediments (Figs. 2 and 3). It is dominated byfescue tussock (Festuca novae-zelandiae) andcontains many other herbaceous plants and num-erous seedlings of Carmichaelia. As a closed com-munity it resembles the kind of grassland usuallyfound on pastoral run country at higher altitudes.Here and there an occasional plant of mata-
gouri, heavily browsed native broom (Carmichael-ia robusta and probably C. violacea), or a smallclump of kanuka, break the apparent uniformityof this grassland. A feature of the community isthe extremely patchy distribution of many species.
Danthonia grassland
Several phases of turf grassland dominated bydanthonia (Notodanthonia clavata), with scat-tered shrubs of native broom and matagouri arealso conspicuous (Figs. 2 and 3). The latter arefrom 1-3 ft. tall, appear to be even-aged (about40 years) and lack vigour. No seedling matagouriwere found.
49
FIGURE3. Danthonia grassland merging into short-tussock grassland with patches of kanuka. South-ern end oj re!)'erve;looking towards Banks Penin-
,ula, view slighlly to right of Figure 2.
Waler-race community
This artificial community consists of both nativeand adventive species, ranging from submergedaquatics to normal terrestrial species favoured bythe increased soil moisture. Such water-races area feature of the Canterbury Plains and heip toextend the distribution of otherwise restrictedspecies.
FLORA
A list of speCies is appended. For the vascula.plants it is reasonably complete, but further studieswill undoubtedly extend the list of bryophytesand lichens. Fungi have not been surveyed.
Features of this list are:
(1) the surprisingly large number of nativespeCies; 76 speCies representing 60 gen-era.
(2) among these, the number that are rardy,or perhaps never previously, found onthe Canterbury Plains, e.g. Iphigenianovae~zelandiae, CarmichlJelia monrai,Raoulia subsericea, Scirpus caIigenis,Stackhousia minima.
(3) the relatively low number and propor-tion of adventive species: all widespreadin tussock grasslands, except the 16species restricted to the water~race.
Native plants recorded outside the reserve butnot seen within are indicated on the list, in allnine speCies. It is possible that some may appearin future years, but it would be worthwhile to
-SD- Cora brevicllimis- SD- C.colcnwi---w C. inversat---W C. virgata--D- Carmichaelia mOI/roiKSD- C. robusla-SD- C. violacea('l)-S-- Ce/rnisia gracilellia agg.---W Cel/tel/a IIlIifiora-SD- Cerastillm holosteoides"--D- Cirsillm vulgare*--[)- Colohunthus hrcl'h'epall/s"l
50 PROCEEDINGS OF THE NEW ZEALAND ECOLOGICAL SOCIETY, VOL. 17, 1970
transplant examples of these species into specifiedplots within the reserve before they completelydisappear through further land development.
Voucher specimens of all species are b6ngcollected for the Botany Division herbarium.
FAUNA
At one time rabbits (Oryctolagus cuniculus)and hares (Lepus europaeus) were abundant inthis area and contributed to the modification of thevegetation. At present their numbers are lowand under control.
The common mouse (Mus musculus) and atleast one species of skink (Leiolopisma) havebeen seen in the reserve. The fol1owing birds fre~quent the area: fantail (Rhipidura fuliginosa),harrier (Circus approximans), skylark (Alaudaarvensis), starling ( Sturnus vulgarh;) and hedgesparrow (Prunella ff1odularis). At least one speciesof finch nests in the short kanuka.
DISCUSSION
The Bankside Reserve is of particular interestsince it appears to be the last substantial remnantof primitive scrub and grassland on surfaces ofits precise age group on the Canterbury Plains.It is a relic in the strict sense and one in dangerof destruction by encroaching land development.The Eyre-Paparua soil complex alone covers260,000 acres in the South Island, of which240,000 acres occur in Canterbury. The uncul-tivated site at Bankside thus provides a basicreference for one of the Plain's largest soil groups,together with its soil fiora and fauna.
Reserves of this nature are comparatively newand no doubt many problems of managemcnt willarise. For example. experience has shown that thestructure and composition of these communitiesmay change once burning ceases and grazinganimals are excluded. If the existing commrmitiesare to be maintained, it may be desirable to intro-duce a policy of infrequent grazing and, perhaps,controlled burning to parts of the reserve.How~ever, providing no new disturbance arises, theyshould remain indefinitely and provide a fullrecord of Postglacial soil development und ahistory of the vegetation.
ACKNOWLEDGMENTS
I am grateful to the following persons who have visitedthe Bankside Reserve with me and helped in many ways:Drs L. B. Moore and P. Wardle. Messrs H. E. Connorand t. W. Rawson. Mrs M. J. A. "Bulfin, 11iss R. Mason.Miss B. H. Macmillan, all of Botany Division, D.S.I.R.;Dr G. T. Daly and Mr E. J. B. Cutler, Lincoln College;Mr D. W. Ivcs, Soil Bureau, D.S.l.R. Botany Divisionstaf1:' assisted \",'ith the identification of plant material.Figure I was drawn by Mrs B. McCulloch.
REFERENCES
AClAND, L G. D. 1946. The early Callterbury rllll.~.(Revised edition.) Whitcombe and Tombs Ltd.,Christchurch.
C02KAYNE,L. 1928 The vegetation of New Zealand. InDie vegetation del' Erde XIV. Engelman, Leipzig.(2nd Edition.)
CONNOR,H. E., and MACRAE,A. H. 1968. Montane andsubalpine tussock grasslands in Canterbury. In Thenatural history of Cal/terbury. (G. A. Knox Edit.)A. H. and A. W. Reed, Wellington.
Cox, J. E., and MEAD,C. B. 1963. Soil evidence relatingto post~glacial climate on the Canterbury Plains.Proc. N. Z. Ewl. Soc. 10: 28-38.
MOLLOY,B. P. J. 1968. Recent history of the vegetation.In The 11tItural history of Canterbury. (G. A. KnoxEdit.) A. H. and A. W. Reed, Wellington.
SUGGATE.R. P. 1958: Late quaternary deposits of theChristchurch metropolitan area. N.Z. J. Geol.Geophys. 1: 103-122.
SUGGHE, R. P. 1963. The fan surfaces of the centralCanterbury Plain. N.Z. J. Geo/. Geophys. 6: 281-287.
WARD,W. T.; HARRIS,C. 5., and ScHAPPER,H. P. 1964.Soils and agriculture of Ellesmere County Canter~bury, New Zealand. N.2. Soil Bill'. Bull. 21.
KSO- N otodmuhOlda cIavata R. ecklo/lii var. sublillearis--S-- o phioglo.'iSIlI1l coriaceum R. genicll/ata-S-- Oreomyrrhis rigida R. /ciodea var. cOlldellsata.-SO- Oxulis comicu/ata Romalil/a sp.
