N. Z. E C 0 LOG I C A L SO C lET Y ~ 7 The Ecology of Tussock Grasslands Chairman: Prof. T. W. Walker . The Plants of Tussock Grassland Miss L. B. Moore One fifth of New Zealand carries tussock some other ferns). Amongst smaller grasses or bunch grass vegetation related to the so- only one (Danthonia exigua) is a real twitch. called steppesof the world (1). Tall-tussock Creepers root along the soil surface mostly grassland has long been distinguished from in damper spots (Hydrocotyle, Mentha, Ner- low-tussock grassland, but further subdivi- tera, Mazus, Cotula, Pratia spp.) but species sion awaits basic field work. Failing a classi- of Acaena and Raoulia of this growth form fication of vegetation types a plant capability extend into drier places. The Raoulias grow survey reviews the restricted range of slowly and live very long though some, e.g. growth forms present. the scabweedR. lutescens, are acutely sensi- Indigenous plants of the primitive grass- tive to shading. land are predominantly long-lived, ever- Root system and water requirements have green, mostly spot-bound, poor in seeding been little studied. Comparatively shallow and/or seedlings,'and with restricted regen- roots are recorded in Poa caespitosa which eration from either above-ground buds or is particularly successful in moist, shallow subterranean perennating organs. Many, soils with good granulation and aeration. like the tussock grasses,consist of loose-knit Danthonia flaveseens, Celmisia spectabilis, potentially independent parts that theoretic- and Festuca novlhe-zelandiaeall have longer ally need never reach senility; it is not at roots (2 metres or more), but while the all unusual for a tussock to live 20 years or Danthonia, with crown partly buried, is more. Growth is slow. Fescuesin the Wai- extremely hard to dislodge, fans of the fes- makariri doubling their number of leaves in cue often come away easily, partly because three years (2) contrast strongly with rye- of insect damage. grass in which "vigorous tillers can increase Studies of seed production and seedling in numbers by 70-100% per week, given ade- vigour in tus-sockgrasses (Dunbar, Sewell, quate light" (3). Size is no guide to age- Connor) are largely unpublished. The tall starved tussocks have remained 2in. high Danthonias have "seed years"; profuse flow- with 6-8 leaves for ten years. Such long- ering following burning (6) 'cf. prairie lived plants influence the underlying soil, grasses in Wisconsin (7) perhaps results affecting temperature and frost action (4) from greater temperature changes at more and also water relations. exposed growing tips. Little is known of Accompanying plants are often long-lived extent and effect of grazing of seed,of seed [e.g. Dracophyllum longifolium 110 years dispersal,and of soil penetration mechan- old (5)] and annuals and biennials are few. isms. Few seedlings succeedin bare soil be- Summer-green perennials include thth decid- tween tussock clumps in badly depleted areas uous shrubs Discaria toumatou and fuchsia. and the reasons are being sought (8). Of less woody things that die to ground The more palatable native plants like ani- level in autumn some sprout in spring in the seeds and speargrasses have decreased, but same place (e.g. Chrysobactron hookeri, there is much to be learned about the graz- orchids, gentians, forms of Craspedia, Epilo- ing of shrubs. Tussocks are mostly eaten bium spp.); others have extensive under- only as young growth or in times of dearth, ground runners and spread vegetatively, but big uussooussocksare cropped by horses binding soil and shingle (many ededges,the and cattle (and N otornis) and deer may se- half-buried Muehlenbeckia axillaris, the lect between strains. Sedges provide much dwarf Coriarias, Urtica aspera, bracken and fodder in seepageareas, and Hercus is study- 8 N.Z. EC0LOGICAL S0C I ETY ing winter sheep use of native grasses in provide some forage, 'have efficient seed dis- west Otago. Slow growth hinders recovery persal and germination and sprout vigor- after defoliation. After 'spring 'burning on ously after damage, briar often from roots Maungatua Mark (5) records elimination distant from the main plant. Pinus mur- of snowtussock under 'heavy, and survival rayana, a tree that throws good seedlings under light, grazing; less palatable shrubs when still young, is spreading. (Cassinia and Hebe spp.) increased. Fire and grazing generally alter the growth form Good management maintains low-growing spectrum, favouring plants with better pro- palatable plants between protecting tussocks tected buds, the less palatable, the lower- but under higher rainfalls scrub is a serious growing, widely-rooting and mat-forming problem. In drier parts exotic annuals and species, and those with efficient seed disper- biennials and low-growing natives are the sal and seedling vigour. main cover, suggesting that we would have much more desert if exotic plants had not Exotic plants include a host of free-seed- come in along with exotic animals. Though ing and fast-germinating annuals and bien- snow-tussocks occupy some relatively low- nials not yet fully distributed through the lying and easy-contoured land the steeper tall country. Amongst introduced grasses cocks- tussocks die, unless scrub invades, more soil foot approaches tussock form, sweet vernal of introduced plants and there, as the snow- and yorkshire fog make a close sward, and tussoks die, unless scrub invades, more soil turf-forming indigenous Danthonias have in- is exposed to erosion, with spectacular, creased greatly; browntop (affecting water costly and apparently irreversible results. runoff) and Poa pratensis are of the twitchy habit previously little represented. These To sum up, the total area of tussock grass- grasses are palatable at some stage, pro- land, offering a huge variety of growing con- duce plenty of good seed, and fill available ditions, is occupied by plants with a limited ground under higher rainfalls. The most but largely undetermined range of response important new creeping plant, white clover, to climate and utilization. A primary need has reached damp gullies remote in fescue is a stocktaking and subdivision into eco- tussock grassland. Sheep's 'sorrel with tough logical units correlated with the potential- extensive roots to several feet deep, well ities and limitations of the plants present, protected buds, and free seeding is even leading to a definition of those niches for more widespread; it is a good soil binder, which no suitable species are at hand. As tolerates grazing, resists frost and drought, long as tussock grassland is to be retained and prepares bare ground for invasion by it must be remembered that, because its yorkshire fog. Hypochaeris radicata, also dominants are perennials with very long far-ranging, is eaten seasonally (9) and lives, it has many of the characteristics of a should be nutritious (10). Flatweeds of the forest and few of those of a short rotation genus Hieracium will certainly spread fur- pasture. Like a forest, it is the product of ther ,and are grazed in hard places (11). a long slow development, and like a forest it The deciduous shrubs briar and gooseberry is much easier to destroy than to rebuild. REFERENCES (1) ALLAN. H. H., 1946: N.Z. Geo.gr. 2, 1. (2) SEWELL, T. G., 1952: Proc. N.Z. Grassl. Ass. 130. (3) MITCHELL, K. J., 1954: N.Z. J. Sci. Tech. A 36, 206. (4) GRADWELL, M. W., 1954: Ibid. B 36, 240. (5) MARK, A. F., 1954. M.Sc. Thesis, Otago Univ. (6) BARKER, A. P. 1953: N.Z. D.S.I.R. Bull. 107. (7) DIX, R. L., BUTLER, J. E., 1954: J. Range Manag. 7, 265. (8) SIMPSON, M. J. A., MOORE, L. B., 1955: N.Z.J. Sci. Tech. A 37, 93. (9) BOYCE, W. R., 1939; M.Sc. Thesis, Cant. Univ. Coli. (10) CooP, I. E., DARLING, M., ANDERSON, G. M., 1953: N.Z.J. Sei. Tech. A. 34, 517. (11) KERR, C. J., 1950: S. Cant. Catchment Board 1-34..