DUNBAR: SOWING NATIVE TUSSOCK SPECIES IN HIGH ALTITUDE VEGETATION TRIALS 25

SOWING NATIVE TUSSOCK SPECIES IN HIGH

ALTITUDE REVEGETATION TRIALS

G. A. DUNBAR

Tussock Grasslands and Mountain Lands lnstitute, Lincoln College, Canterbury

SUMMARY: Although a cover of grasses and legumes may be established on exposedmountain subsoils through seeding and the use of a complete fertiliser, this cover is not likelyto last for more than a few years without the application of more fertiliser. Native tussockspecies once established in the protection of other low-growing species might persist andprovide stability over a longer period.This paper describes the early results achieved on two sites in the Canterbury mountains,

through sowing seed of four tussock species under five cover treatments. Sowing of seed ofNotodanthonia setifolia produced very few seedlings but blue tussock, hard tussock and Gilvertussock gave reasonable results. Highest emergence was recorded under the least cover on thecontrol plots, and there was, in general, an inverse relationship between cover treatmentdensity and emergence of tussock seedlings. Survival of tussc<~k seedlings over the first eighteenmonths from sowing was, hQwever, in direct positive proportion to the amount of cover present.Growth of tussock seedlings was slow at both trial sites. Tiller numbers tended to be greatest

in pIe.ts with least competition from cover species. Tussocks remaining amongst cover afterthe first winter tended to decrease in size and vigour over the second growing season.

INTRODUCTION

Investigations into the possibility of revegetat-ing exposed subsoils and screes in mountain areasfirst became a major part of the work of the Tus-sock Grasslands and Mountain Lands Institutein 1965. Pilot trials laid down at three sites in theCanterbury high country in that year tested theeffect of a complete fertiliser mixture on establish-ment and growth of 10 herbaceous species, includ-ing one native grass. This work was followed in1966 by field trials at 10 high altitude sitesthroughout the South Island and by glasshouse pottrials on subsoils from these 10 sites, all designedto determine what nutrients were needed as addi-lives 10 promote satisfactory establishment andgrowth of grasses and clovers. (Tussock Grass-lands and Mountain Lands Institute 1967.) Someof the difficulties associated with the establishmentand maintenance of a protective cover at highaltitude have been discussed by O'Connor andLambrechtsen (1967), O'Connor (1967), andHolloway (1969).Although good establishment and growth of

grasses was obtained in the Institute's trials in1965, work of the above authors had indicatedIhat vigour could decline markedly after 2~3 yearsif no more fertiliser was applied. In Ihe 1965 trialssome planls of native tussock species had estab-lished as volunteers and grown well in the fertil-ised plots. This suggested the possibility that suchspecies. which were slow-growing inilially but

which might be more persistent in Jaw-fertilitysoils, could be included for long-term effect insowings of quick-growing exotic species.In October 1967, trials were laid down at two

eroded mountain sites to study the establishment,growth and survival of four native tussock specieswhen sown with other herbaceous species. Seedof Pinus contorta was sown in addition to thenative species but these resuIts are not includedin this paper.

FIGURE I. The trial site near the summit ofPorter's Pro's, Canterbury, on a west-facing slope

of 27 degrees at 3,200 ft. altitude.

26 PROCEEDINGS OF THE NEW ZEALAND ECOLOGICAL SOCIETY, VOL. 17, 1970

TRIAL SITES

(a) Porter'" Puss

Situation - Near the summit of Porter's Passat 3.200 ft. above sea level. Map referenceNLM.S. 1, Sheet S74, 224855,Slope and Aspect - Slope 27", on west aspect

but exposed to north-west and southerly winds.Soil - Severely eroded, strongly leached high

country yellow-brown earth, belonging to theKaikouran soil set. Surface material consists of amixture of subsoil and fine greywacke fragments.the present depth varying from 2-6 in. over shat-tered greywacke rock. The depth of soil removalin mid-slope has possibly been as much as 18 in.Soil test figures for calcium, potassium. phos-phorus and magnesium are low to very low, andthe pH is 5.3.Vegetation - Vegetation in the vicinity is dom~

inated by Chionochloa fluvescens and C. rigida, inassociation with Dracophyllum acerosum.Climate - Climate in the Porter's Pass and

Foggy Peak Ridge area has been described indetail by Molloy (1963). He interpreted the cli-mate of Foggy Peak Ridge as relatively cool andmoist but stated that the region is subjected per-iodically to the effects of severe winds. He con-cluded that the mean annual rainfall for sites hemeasured is probably about 100 Col. (approx.39 in.). There is a strong funnelling effect ofnorth~west and south-west winds through Porter'sPass. During the winter of 1968 exceptionallyheavy snow covered the area.

FIGURE2. The Craigieburn site is a gently-slopingbut windswept saddle at 3.350 ft, on the fringe of

Ihe Craigieburn Range.

(b) Craigieburn

Situation - On the eastern flank of the Craigie-burn Range at an altitude of 3,250 ft. above sealevel and adjacent to Bridge Hill. Map referenceNZ.M.S. I, Sheet S66, 194026.

Slope and Aspect - Slope 8', with slight south-west aspect but exposed to westerly winds.

Soil - Exposed subsoil with development of anerosion pavement. The original soil waS a stronglyleached high country yellow-brown earth tenta-tively correlated with the Cass soil set. Estimateddepth of soil removal is 12-15 in.. with some re-sorting of material on the slope. Soil test figuresfor calcium. potassium, phosphorus and magnes-ium are low to very low, and the pH is 5A.

Vegetation - On surrounding areas there ismuch Cassiniu with occasional Chionochloarigida. The low ground cover is mainly brown top(Agrostis tenuis), but blue tussock (Poa colensoi),hard tussock (Festuca novae-ze!andiae) and someNotodanthonia seti/olia are present.

Clinwte - Morris (1965) gave results of cli-mate investigations in the Craigieburn Range andincluded figures for Nursery Hill Station which isapproximately half a mile from the trial site. Forthe three years 1961-63 inclusive, precipitationat Nursery Hill was 59.5, 62.6 and 58.7 in, respec-tively. The three-year average mean monthly tem-perature for this station ranged from 35'F. inJuly to 58'F. in January. The mean frost-freeperiod per year during the same period was 115days.

MATERIALS AND METHODS

(a) Cover treatments

Five cover treatments with four replicates weresown at each site, at Porter's Pass on 20 October1967 and at Craigieburn on 25 October 1967.Treatments were:-

1. No seeding2. Inoculated "Huia" white clover (Trifol-ium repens)

3. Chewings fescue (Festuca rubra ssp. com~mutata)

4. Browntop (Agrostis tenuis)5. Massey Basyn Yorkshire fog (Holcus

lunatus)

Seeding of each cover species was at a ratecalculated to give one viable seed per square inchof ground surface.

LABORATORY

SPECIES SEED ORIGINS GERM INATION

Mountain Clarence River head-danthonia waters 1967 52-96% (1)Blue tussock Clarence River head-

waters 1967 '

62% (2)Hard tussock Lincoln] 966, "

original seed fromMackenzie plain 95%

Silver tussock Near Lake Lyndon1967 87%

Urea 208 Ib./acre

Superphosphate 4 cwL/acre

Magnesium sulphate I cwL/acrePotassium sulphate 1 cwL/acre

,

,

DUNBAR: SOWING NATIVE TUSSOCK SPECIES IN HIGH ALTITUDE VEGETATION TRIALS 27

(b) Tussock species

Twenty seeds of each of four native tussockspecies were sown within each cover treatmentplot using a planting frame technique for place-ment as described by Cullen (1965). There werethen within each plot a total of 80 seeds of four

tussock species, 400 seeds within each replicateand 1,600 seeds within each site. Seeds of each ofthe native species were examined on glass over abright light before sowing in an attempt to ensurethat only whole seeds were sown.

FIGURE 3. The wooden frame used for tussocksowing and for relocating seedlings in position on

one of the control plots.

The species sown were mountain danthonia(Notodanthonia setifolia (Hook. f.) Zotov)*, bluetussock (Poa colensoi Hook, f.), hard tussock(Festuca novae-zelandiae (Hack) Ckn.), andsilver tussock (Poa laevis R. Br.). The origins ofthe seed and the laboratory germination at timeof sowing are shown in Table 1.

'" Plant nomenclature according to Standard commollnames for weeds in New Zealand, N.Z. Weed and PestControl Society, Wellington, 1969.

TABLE 1. Tussock seed origins and germination attime at sowing.

Note: (I) The total germination and rate of germiI1a-tion of different samples of mountain dan-thonia varied markedly with different testconditions, but the possible causes of thisvariation cannot be discussed in this paper.

(2) Blue tussock seed from Clarence was usedfor Porter's Pass sowings. At Craigieburn theblue tussock seed was from a 1965 MackenzieCounty collection, the germination of whichwas unknown at the time of sowing.

(c) Fertiliser

Fertiliser was applied to all plots. Plots withthe three grass species and the "no seeding" orcontrol plots received a dressing of the followingmixture:-

On clover plots urea was omitted from thismixture and sodium molybdate, at 4 oz. per acre,was added.

FertiHser and cover treatment seedings werebroadcast onto the ground after the tussock seedshad been planted just beneath the soil surface.

At Porter's Pass records of tussock seedlingswere taken in December 1967, May 1968, Septem-ber 1968 and April 1969. The September 1968 andApril 1969 records included measurements ofseedling height and tiller numb"rs. At Craigieburnthe counts and measurements were made in May1968 and May 1969.

No.emerged % of sown % of viable

Blue tussock 141 35 57Hard tussock 220 54 58Silver tussock 211 53 59

Bluetussock 70.5 62.5 44.4 58.5 48.4 57Hardtussock 65.3 64.5 54.0 51.3 53.9 58Silvertussock. 70.2 70.2 43.5 67.4 44.9 59

Blue Hard Silver AllCOVEK tussock tussock tussock specIes

Control 8.75 12.50 !2.50 33.75Clover 7.75 12.25 12.50 32.50Fescue 7.25 9.75 12.00 29.00Browntop 6.00 10.25 8.00 24.25Fog 5.50 10.25 7.75 23.50

N.S. N.S. LSD3.50 LSD8.41

(5%) (1%)LSD5.99

(5%)

28 PROCEEDINGS OF THE NEW ZEALAND ECOLOGICAL SOCIETY, VOL. ]7, 1970

RESULTS

EMERGENCE AND SURVIVAL OF TUSSOCK SEEDLINGS

(a) Porter's Pass

Emergence - Emergence of seedlings of Noto-danthonia setifolia was disappointingly poor con-sidering the good germinations obtained in thelaboratory tests. Only 3% emerged in the firstseason compared with laboratory germinationsranging from 52-96%. Therefore, in the acconntwhich follows, results from seedings of blue tus-sock, hard tussock and silver tussock only willbe given.

TABLE2.Emergence of tussock seedlings -Porter'sPass.

Table 2 shows that there was a low emergenceof blue tussock as a percentage of seed sown. Italso shows that when allowance is made for lowerviability of the seed, emergence is similar to thatof other species.

Table 3 compares the emergence of these threetussock species under each of the five cover treat-ments, when an adjustment has been made forviability.

TABLE3. Emergence of tussock seedlings as a per-centage of viable seed - Porter's Pass.

COVER TREATMENT

White Y'shire Chewings Brown-Control clover fog fescue top Mean

There were no significant differences in emer-gences of these three species when compared inthis way. However, there were some large differ-ences in emergence within each tussock speciesarising from different cover treatments. This isapparent in Table 3, but is shown in absolutevalues in Table 4, where mean numbers of seed-lings per plot are given.

TABLE4. Numbers of tussock seedlings emergingper plot - Porter's Pass.

The differences in seedling numbers amongstcover treatments is most marked in the means forthe all-species grouping. Analysis of varianceshowed-that emergence under browntop and fogfor this group was significantly lower (at the 1%Jevel) than fOr control. Emergences under whiteclover and chewingsfescue were not significantlydifferent from control.

Although the same general trend was apparentfor the individual tussock species, there wasgreater variation in numbers. amongst the plotsand only with silver tussock were the differencessignificant. Here, as for the all-species grouping,emergence under browntop and fog was signifi-cantly lower than for control.

Because, estimates or measurements of groundcover obtained from the various cover treatmentswere not complete before the first winter, it is notpossible to relate the figures for tussock emergencedirectly to the ground cover achieved during thefirst growing season. Some indication of the rela-tive covers may be obtained from the records inthe spring of 1968, 10 months after sowing. Thesegive the number of hits out of 100 measurementswhich struck cover vegetation in each plot. Meanvalues for the four replicates of each treatmentin September 1968, were: control, 4; white clover,6; chewings fescue, 44; browntop, 59; Yorkshirefog, 46.

Survival - The tussock seedlings were countedin December 1967 and in May 1968 to give figuresfor total emergence as shown in Table 4. Therewere some deaths between December and Mayand the numbers of deaths were deducted fromtotal emergence to give survival figures for autumn1968. Further counts of seedlings made in Sep-

Total Autumn Spring AutumnCOVER emergence 1968 1968 1969Control 33.7 23.2 14.5 8.5Clover 32.5 23.0 15.0 7.7

Fescue 29.0 16.5 13.5 8.7

Browntop 24.2 14.7 14.0 12.2

Fog 23.5 16.0 13.7 10.2LSD8.41 LSD6.99 N.S. N.S.

(1%) (1%)5.99 4.99

(5%) (5%)

Emergence Survival % % Hits1967-68 1969 survival cover 1969

Control 33.7 8.5 25.2 4Clover 32.5 7.7 23.7 6Fescue 29.0 8.7 30.0 40Fog 23.5 10.2 43.4 41Browntop 24.2 12.2 49.8 54

Blue Hard Silver Alltussock tussock tussock tussock

Control 5.5 10.5 9.2 25.2Clover 5.2 10.5 9.0 24.7Fescue 6.0 8.0 6.2 20.2Fog 3.7 5.0 4.5 13.2Browntop 2.2 6.7 3.0 12.0

The details of the mean number of seedlingslost per plot for each species and cover combina-tion are given in Table 7. This shows that thetrends in losses were similar for each tussockspecies, but, again, the individual plot figures weretoo variable for satisfactory statistical interpreta-tion.

The figures in Table 6 show a strong relation-ship between the percentage of hits on cover (orthe percentage of hits on bare ground) and thenumb"r of tussock seedlings lost from each treat-ment. The correlation coefficient calculated forthe percentage bare ground on each of the 20plots and the percentage survival of all tussockgave a figure of r= -0.608 which is significantat the 1% level.

,Over the trial as a whole the survival rates to

the autumn of 1969, expressed as a percentageof emergence, were: blue tussock 35.5%, hardtussock 25.9% and silver tussock 39.3%. If sur-vival is expressed as a p~rcentage of viable seedsown then the figures are 20.2%, 15% and 23.3%respectively.

(b) Craigieburn

Emergence - The exceptionally heavy snow of16 and 17 November 1967 which was followed byvery rapid thaw caused severe surface wash andrill erosion on the Craigieburn site approximatelythree weeks after sowing. A rill approximately6 in. deep and 8-12 in. wide developed throughoutthe length of two of the four replicates and, withaccompanying surface washing of soil, effectivelydestroyed any chance of obtaining results fromone half of the trial. Such severity of erosion ona relatively gentle slope W) was surpnsmg.Results on the other two replicates were almostcertainly affected by surface wash, but counts for

DUNBAR: SOWING NATIVE TUSSOCK SPECIES IN HIGH ALTITUDE VEGETATION TRIALS 29

tember 1968 and April 1969 showed the changesin proportions of seedlings surviving in the fivecover treatments (Table 5).

TABLE5. Tussock seedling at successive countings-- Porter's Pass (mean number per plot, all species

grouped).

This table shows clearly the trend downwardin numbers of tussock seedlings in all treatmentsand, in particular, the very marked fall in numbersin the control and white clover plots.

The effect of the relative changes in seedlingnumbers under different cover crops is shown inanalysis of variance of each seedling count. Thus.as discussed earlier, total emergence during thefirst growing season was significantly lower underYorkshire fog and brown top than under the con-trol. This same relationship persisted in the countsfor survival made in late autumn. but with theaddition that tussock numbers under chewings fes-cue were then also significantly lower than forcontrol.

However, by the spring of 1968 this differencehad been lost and by the autumn of 1969 thetrend was for highest persistence under the densestcover (Table 6).

TABLE6. Tussock emergence and survival in rela-tion to cover treatment - Porter's Pass (mean per

plot. all species grouped).

There were very wide differences in mean per-centage survival as shown in Table 6, but verylarge variations occurred amongst figures for

individual plots, and there were no statisticallysignificant differences.

TABLE 7. Seedling tussock losses-Porter's Pass- from emergence 1968 to autumn 1969 (mean

number per plot).

No. emerged %of sown % of viableBlue tussock 28 14.0 -Hard lussock 54 27.0 28.4Silver tu ssock 67 33.5 37.6

Blue Hard Silver AllCOVER lussock tussock tussock tussockControl 6.0 7.5 8.0 21.5Clover 2.5 5.5 9.0 17.0Fescue 2.0 4.5 6.5 13.0Browntop 1.5 6.5 6.0 14.0Fo~ 2.0 3.0 4.0 9.0c

N.S.

Control Clover Fescue Fa" Browntopc52.0 40.0 64.0 72.5 82.5

Emergence Survival % % Cover1968 1969 Survival 1969

Control 21.5 21.0 97.7 54Clover 17.0 ]3.0 76.5 41Fescue 13.0 11.5 88.5 54Browntop ]4.4 13.5 96.4 85FoO" 9.0 8.0 88.9 59c

30 PROCEEDINGS OF THE NEW ZEALAND ECOLOGICAL SOCIETY, VOL. 17, 1970

emergence and for survival were made in theautumn of 1968 and the autumn of 1969. Totalemergence for these two replicates is shown inTable 8.

TABI.E8. Emergence of seedlings at CraiRieburn.

Notodant/Zonia setifolia has been omitted fromthe detailed results as emergence was again verylow, with only eight seedlings emerging from 100seeds. The seed of blue tussock was from a differ-ent source and was older than the seed used atPorter's Pass. Because of an oversight it was nottested for germination until 20 monlhs after theCraigieburn sowing and the seed was then fouryears old. The mean germination was ]4%.Although the viability at time of sowing cannotbe determined, it is not likely to have exceeded the62% recorded for the recently-harvested seed usedat Porter's Pass. However, it was almost certainlymore than the 14% recorded in ]969.For hard tussock and silver tussock, emergence

rated 49% and 64%, respectively, of that recordedat Porter's Pass. Because of the destruction of tworepHcates. low emergence in the remainder anduncertainty about the viahility of blue tussock, noattempt has been made to test differences amongsttussock species within cover crops. The numbersof tussock seedlings emerging per plot, withinspecies and cover categories are shown in Table 9.

TABI.E 9. Numbers of tussock seedlings emergingper plot - Craigieburn.

Despite the small number of samples availablethese fi~ures do show a trend in relation to covertreatment similar to that recorded at Porter's Pass(Table 4). For the all-tussock grouping, highestemergence was recorded under control and ]owestunder Yorkshire fog. An analysis of variance forrecords for all-tussock failed to show any signifi.cant difference arising from cover treatment.

Survival- Previous trials at the Craigieburnsite had shown that brown top was an aggressiveinvader when fertiliser was applied to bare sub-soil. This was borne out by results in controlplots which were given the fertiliser mixture, butno cover seeding. By the autumn of 1968, sevenmonths after seeding, records of percentage hitson cover vegetation as a mean of two plots wereas follows:

The control plot had more cover than all treat-ments at Porter's Pass except brown top. Hits onbrowntop comprised 47 out of the 52 on controlplots, 13 of the 40 on clover plots and 26 of the64 on chewings fescue plots. The growth of brown-top undoubtedly had a stabilising effect and sev-erely limited the value of the control for compar-ing survival. There was, in fact, very little mortal-ity in tussock seedlings between emergence andthe autumn of 1969, as is illustrated by figures inTable 10.

TABLE10. Tw;sack emergence and survival in rela~

tian to cover treatment - Craigieburn (mean perplol for all species)

The much higher survival than shown in Table6 for Porter's Pass may be attributed to the bettercover and gentler slope. Although the initial fig-ures for emergence were considerably lower thanat Porter's Pass, the numbers per plot at the endof the period were better for all treatments exceptYorkshire fog.

There was very little difference in survivalsamongst the individual tussock species. Thus, forthe trial as a whole, survival as a percentage ofemergence was: blue tussock 96, hard tussock 89and silver tussock 88. Survival of hard tussockand silver tussock seedlings as a percentage of theviable seed sown was slightly better than atPorter's Pass. 25 and 33 compared with 15 and 23.

TABLE 11. Number of tillers on young tussocks.

Blue Hard Silvertussock tussock tussock

COVER (a) (b) (a) (b) (a) (b)

Browntop 6.2 5.5 2.7 3.4 3.2 4.0Fou 8.2 10.2 3.4 3.2 3.9 5.4"Fescue 6.1 6.0 4.2 4.8 4.1 5.6Clover 6.5 11.3 4.2 5.6 6.0 4.0Control 13.5 9.4 6.7 6.8 8.6 8.9Mean 8.6 9.2 4.1 5.0 5.2 5.6

(a) Porter's Pass, September 1968.(b) Craigieburn, May 1968.

DUNBAR: SOWING NATIVE TUSSOCK SPECIES IN HIGH ALTITUDE VEGETATION TRIALS

GROWTH OF SEEDLINGS

In the early autumn of ]968, erosion below thefence at Porter's Pass allowed hares to enter theplot and graze much of the cover vegetation andsome of the seedling tussocks. This grazingaffected the records Df seedling heights made in

the spring of 1968 but did not affect the recordsfor titler numbers, There was no grazing atCraigieburn.At Porter's Pass, II months after sowing, the

mean heights of plants were, blue tussock, 3.27cm., hard tussock, 5.36 cm. and silver tussock,5.81 cm. At Craigieburn, seven months after sow-ing, the mean heights were, 4.03 cm., 6.32 cm.and 6.27 cm. respectively. Moister soil conditionscoupled with the absence of grazing could accountfor the greater size of the Craigieburn plants.

Tiller counts made at the same time also showeda trend for larger tussocks at Craigieburn (TableII).

At Porter's Pass the ranking of tiller numbersfrom greatest number for blue tussock to smallestnumber for hard tussock was maintained underall cover treatments except chewings fescue. Therewas a markedly larger number of tillers in thecontrol or no cover treatment than in the grassand clover treatments. This may be attributedprincipally to the lack of competition for fertilisernitrogen from cover species. There was also littlecompetition with tussock seedlings in the cloverplots because of poor clover establishment (6%cover, 1969) but there, in the absence of fertilisernitrogen. tussock tiller numbers were similar tothose in the grass plots.Mean numbers of tillers for each tussock species

for the whole trial were slightly larger at Craigie-burn than at Porter's Pass, but they were not

31

consistently so in relation to cover treatment. Incommon with the Porter's Pass results, the rank-ing order for tiller numbers was from blue tussockgreatest to hard tussock least for all cover treat-ments except one. The invasion of the clover andthe control plots by brown top at Craigieburn

appears to have lessened the beneficial effect ontitler numbers which was present in the absenceof competition at Porter's Pass.

.

By the autumn of 1969 measurements showedthat there were only slight changes in the heightsand tiller numbers of most tussock seedlings. AtPorter's Pass, the mean tiller numbers for blue,hard and silver tussocks respectively were, 8.8,4.1, and 6.1, compared with 8.6, 4.1 and 5.2 in theprevious spring. By contrast the figures for meannumber of tillers for tussocks in the control plotshad risen substantially for all three species, from13.5 to ]6.5 for blue tussock, 6.7 to 13.4 for hardtussock and from 8.6 to 15.1 for silver tussock.This was not, however, an indication of growthin all seedlings but was a reflection of the highnatural culling of the smaller seedlings in theunprotected ground.

In May] 969 at Craigieburn too, the meannumber of tillers had decreased. from 9.2 to 7.1for blue tussock, 5.0 to 4.6 for hard tussock and5.6 to 4.8 for silver tussock. On the clover andcontrol plots the presence of much browntop coverhad prevented frost heaving of the smaller tus-socks and as a consequence figures for meantiller numbers on these plots showed only a slightdownward trend compared with the large increaseat Porter's Pass.

CONCLUSIONS

The results of these trials were somewhat dis-appointing, particularly in the low seedling num-bers, which were caused in part by storm damage.Increased replication could have helped to over-come this.

There seem to be no major differences aml'ngstthe three tussock species in their ability to germ-inate and emerge in the field. On the other hand,the poor emergence of Notodanthonia setifolia isworth further investigation.

Emergence of the tussocks was influencedapparently by the density of the other plant cover

32 PROCEEDINGS OF THE NEW ZEALAND ECOLOGICAL SOCIETY, VOL. 17, ]970

establishing at the same time, Tussock emergencegenerally decreased with increasing amounts ofother plant cover.

The percentage of seedling tussocks survivingthe action of frost-heaving and subsequent desic-cation was also closely linked with the success ofestablishment of the cover species. Thus, survivalvaried inversely with the amount of bare groundin each plot. Although results did not enable firmconclusions to be drawn on the relative abilitiesof the tussock species to survive, there were indi-cations that hard tussock seedlings were less ablein this respect than blue or silver tussock.

Growth of the tussocks was very slow, evenwith fertiliser. Less competition for nutrients fromcover species on control plots was ret1ecled ingreater tillering in tussocks, but against this in-crease in size must be balanced the lower survivalrate on unprotected soil.

Most tussocks decreased in size dudng thesecond growing season. It is possible that althoughtussock seedlings establish under these conditions,they may not survive for long without additionalfertiliser or with nitrogen from legumes. However,if there is merit in attempting to re-establish a

many-layered vegetation, then the inclusion oftussock seeds in the mixture provides some hopeof achieving this.

REFERENCES

CULLEN, N. A. 1965. Techniques used in establishmentstudies on unimproved grasslands. N.Z. Agric. 5ci.I (I): 25.

O'CONNOR, K. F., and LAMBRECHTSEN, N. C. 1967. Someecological aspects of revegetation of eroded Kai-kouran soil at Black Birch Range, Mar1bofCo~gh.Proc. NZ. Ecol. Soc. 14: 1-7.

O'CoNNOR, K. F. 1967. Engineering with grass: 1. Coun-teracting soil frost. Soil and Water 4 (1): 3-6.

HOLLOWAY,J. T. 1969. The role of the Protection Fores~try Branch, Forest Research Institute, in the highcountry. Rev. Tussock Grasslds Mount. Lands Inst.16: 33-44.

MOLLOY,B. P. J. 1963. Soil genesis and plant successionin the subalpine and alpine zones of Torlesse Range,Canterbury, New Zealand. N.Z. J. Bot. 1: 137-148.

MORRIS,J. Y. 1965. Climate investigations in the Craigie-burn Range, New Z~aland. N.Z. J, Sci. 8: 556-582.

TUSSOCK GRASSLANDS AND MOUNTAIN LANDS INSTITUTE,1967, 7th Ann. Rept., Lincoln College, Christchurch.