BOTANY DIVISION DSIR
REPORT FLOWERING CURRANT (Ribes sanguineum) SHRUBLANOS IN THE LOWER WAITAKI VALLEY, SOUTH CANTERBURY P.A. WILLIAMS BOTANY DIVISION, DSIR MAY 1983 ,Flowering currant ( Ribe~ sanguineum)
$hrublands in the lower Waitaki Valley, South Canterbury
P.A. Williams .Botany Division, DSIR, Lincoln New Zealand \
,AB STRACT
Flowering currant (Ribes sanguineum) is classified a noxious plant in Waitaki County, South Canterbury. On the north bank of the Waitaki river it forms scrub- grasslands wi th the spi ny shrub matagouri (Discaric:_
!_oumatou) and species of Coprosma,particularly on shady hillslopes and gullies . The stem diameters of flowering currant and matagouri were measured and the ages were determined from ring counts. There is a close positive relationship between stem diameter and age for f l owering currant. Seedlings are rare away from the protection of existing shrubs and most establish beneath matagouri bushes. Flowering currant can spread by suckering and layering but this is mostly prevented by
sheep and r abbit grazing. Sixty five percent of flowering currant bushes are older than 10 years, many are older than 20 years and the
oldest is 36 years. The apparent spread of flowering currant in
recent years has resulted mostly from t he slow expansion of bushes
suppressing matagouri which·has a much slower growth rate. The
flowering currant stands are self-perpetuating, but they are being slo1:-1ly
i nvaded by wind--dispersed adventive trees.
Key words : Ribe sanguineu~ , Disc.aria toumatou, shrub populations,
scrub, invasion, noxious pl ants , Waitaki valley, Canterbury,
New Zeal and INTRODUCTION
<;:.. from garden cultivation, grows spo-i;;,~ically in grassland, scrub and forest margins throughout eastern South Island. In Canterbury it is found in sites similar to those of its native western United States (Abrams, 194"•;
Hitchcock and Cronquist 1973) - along creeks, in damp situations and in higher rainfall localities (Healy 1969). Dingwall (1962) and Leonard
(1962) suggested flowering currant was spreading and they warned that it could become a serious weed if left unchecked. However, it had not become so fifteen years later, when the distribution of 13 scrubwe<=ds was recorded on South Island agricultural and pastoral land by means of a postal questionnaire to land ow11ers (Bascand and Jowett 1981,\'\82). More recently, flowering currant was classified as a noxious plant in Waitaki county,
South Canterbury, because it was considered to be spreading, especially on the north bank of the Waitaki river. !- I studied this flowering cucrant '" 11 "infestation , the associated vegetation, and the age structure and rate of spread of flowering currant to determine whether it ·was threatening pastoral land in the. lower Waitaki.
STUDY .AREA
The main area of flowering current (hereafter-termed currant) on the north side of the lower Waitaki valley, 10 km east o:E Kurow (Fig. 1). Here
the valley floor at c. 150 m above sea level, adjoins the adjacent grey-:vack\;'., hill country via a steep fault scarp with talus cones and fans. Streams
draining through the fault scarp form steep to very steep gullies. The
soils are predominantly yellow-grey-earths and related steepland soils (N.Z. Soil Bureau 1968). The mean annual erature is c. 10.5°C on the valley
floor (N. Z. l!eteorological Servi er" 1978) with hot summers and cold winters - The me.an annual rainfall of 514 mm is distributed evenly
throughout the year (N.Z. Neteorological Service 1979).
The hill country in the study area is used for extensive grazing,
but large areas are covered with a mosaic of matagouri (Discar~'":. touma
scrub and shrublands. These have varying proportions of other native
shrubs, mainly Coprosma p-ropinqu.::~, and the adventive shrubs brier O~osa
rubig_::~~~~) and gooseberry (Ripes uva·-crispa). Currant is ir:iportan,t over an
area of Lf. 8 km2 on the scarp and the lower gullies, between Station Peak
and Meyer (N.Z.H.S. 1 S.127). Damp gullies have a few remaining native
trees of broadleaf ·------Griselinia ------littoralis) and kowhai (Sophora ------"-----microphylla),
but the main tree is now elder (~ambucu~ nigra). Sheep are the main grazing
animal but rabbits (Oryctolagus cun:i_cu~us)are abundant, and keep the ground
bare in places.
Currant also grows in similar vegetation over a much smaller area
in the adjacent Waiho River catchment, but this area was not studied
closely.
:METHODS
Six stands were selected with densities of currant ranging from
scattered bushes amongst other shrubs,.to those with a dense canopy of
cur rant bushes., Plots 2 m wide and from 15 m to 40 m in
length depending on the shrub density, were laid out across the slope and
measurements made of aspect and slope. The perceritage cover of woody
plants in the canopy was estimated. The frequency of shrub seedlings and bare-ground was recorded from
5, m2 subplots. The length of the main stem of all woody plants ·was measured by extending a sliding rule (Will:\.2:113 in press) 1-1p into the canopy parallel to the main stem and :Lndepemlent of the slope of the ground. The largest stem of every currant bush rooted within the plots, and of several matagouri busheE>, was then cut at about 8 cm above ground level and cross--sectional d:i.sks taken for counting growth rings. In addirion, twelve currant bushes were sampled s~nilarly at the limits of the colony. both upslope towards Mt Meyer (Fig. 1) and on the scarp adjacent to the valley floor. Species o~ Ribes generally have well defined
growth rings (Stern et al. 1970) and currant bushes in eastern South Island are similarly distinct.
Aerial photographs taken in 1966 were used to compare scrub patterns with these of the present day.
RESUI"TS
l_lO>.'S CO'.,;lpOSl• ·ti' Oil O.f' vo0ot·1t-i 0,1 • ., 1 T Table 1 S ·· .v_ t'ne -·- - the· ~c,~ c ~. , , ·witn stanc.s arrangeu
in order of increasing age (Table 2). Native shrubs are important in all
but the oldest stands (5,6), but even here, decaying stumps of matagour.i lay
beneath the currant bushes. Isolated currant bushes invariably grow in the
protection of nati.ve shn1bs, parti.cularly rnat1:cgourL Currant bushes are
generally taller than the asaociated species, except elder (Table 1).
F'~::;i~· 2 Stands with dense currant ( 2 : m ), including some at least 20 years "· old, a-r:e generally on shady faces. The oldest currant found, ubush O",
was 36 years old and grew in a moist gully 0.8 km north of the homestead.
CFig ... 1).. Patches of sparse, young curra~t ( o~t ) grow in the 101?1er
valleys mostly on sunny north-rv<~st facing slopes (Stand 1). Towards the heads of the streams, above c. 300 m, currant becomes almost con fined to gullies and toe slopes, although one shrub nine years old was found on a steep sunny face at 520 m.
There is a considerable range in the age of the currant bushes , in all s t ands exce.pt stand 1 (Table 2). Ov erall, 65 percent of bushes are older than 10 years , and . the ir mean is 13 ± 6 . The 12 i solated bushes including "bush 0 11 had a similar mean of 17 ± 9. The s even matagouri bushes growing amongst the currant wer e between 20 years and 83 years , with a mean of 52 ± 23. Bushes only 1.3 tall ranged from 20 to 75 years .
Isolated currant s eedlings up to 1 rn t a ll are occas i onally found in shady situations, some distance fro~ adult bushes and usually in the shelter of native shrubs. Cur!:ant seedlings are rare on sunny f a ces , even amongst adult bushes (S tand 1, Table 1), but they can be found in old stands in shady situations . In stand.6 for examp l e , a few seedlings were present in canopy openings for med by fallen currant branches .
There appeared to be no consistent relationship between the age of the currant bushes and their position in the clump , even in the oldest stands.
Currant bushes less than 10 years of age u sually have several main stems which grow vertically for about 1.5 m before arching over. New shoots arise from these stems and grow vertically until they too, arch over. This growth habit can result i n a mass of old stems growing at 20° - 40° to t he slope of the ground. From the outs ide of a currant stand , the young shoo t s appear as many sma ll bushes , which belie the l ow density and age of t he bushes . These arching branches rarely take root however, and substantial expansion by layering wa s observed only in "bush O". This had a n overall canopy diame ter of 6 . 8 m which included a horizontal branch 3.6 m long and 23 years old at the junction with the main s t em. This branch had
sets of vertical shoots arising from t wo rooted points 1 . 2 m apart . The mid-section of the horizontal branch beyond the distal rooted point of the branch was nine years old. These observations show that adventitious roots were not formed until about 13 years after the bush established and that no new rooting poin ts have formed for nine years.
Adventitious shoots arising close to the ground may give rise to new
individuals close to the parent bush once the connecting stem has decajed .
This cc.cues particularly on mo i. st sites with unstable soil to cover
the interconnecting stem (Stand 3) . Bushes that have grown in this way become indistinguishable from those established from seed .
Expansion of the currant patch by this means is rare because young shoots at.
or near ground level are heavily bro':.Jsed by sheep and rabbits . The
boundaries of most currant patches are therefore hedged where they are
adjacent to grassland.
The growth rate of currant appears to be f airly uniform, irrespective
of site, for about half the variation in bush height is explained by a
linear relationship with age :
y (height , m) = 1.28 + 0 . 08 x(years); r = 0 . 71; p < 0. 1.
The relationship with stem diameter is much closer , with about 90 percent
of the variation being explained: y (diameter, mm) 4 . 38 + 2. 41 x (years) ;
r = 0.84; p < 0.01 .
These equations are not derived from a r andom sample of all currant
bu~hes in the area, but there is no reason to suggest they would be
substantially different had this been so. They apply only to lower
Waitaki currant stands though , for its diameter growth can be twice
as fast on yellow-brown- earths in the \faiho rive r catchment, e.g. 72 mm ·
in seven yeacs (personal observation). DISCUSSION AND CONCLUSIONS
It appears that currant does not invad<:; open grassland grazed by sheep and rabbits. Currant seedlings and young plants are restricted to existing shrublands and isol ated bushes, particularly of matagouri. Matagouri may grow rapidly on youthful fer t ile sites
(Daly 1969 ), but on ol der, l ess f ertile s oi l s under low sheep grazing pressure, matagouri populations have low growth rates, high annual
s urvival rates and continuing recnlitment which contribute to stable
populations (Primack 1978). This stability has been disturbed in the
study area by the est ablishment of currant. The apparent increase in
currant i n the last 10 years or so has been l argely the resul t of
currant bushes over-t opping the matagouri . The l atter has a much
slower and highly variable growth rate in t he study area .
Pa t cl.es of currant fu·rthest away from the likeJ.y original source of
the homestead are as old , or ol der than those nearby , so there h as been
no r ecent expansion of the range of currant in the vicil1i.ty . However,
t he presence of even scattered seedlings and young bushes away from
t he main currant stands (e . g. stand 1) suggests curr ant will continue to
slowly spread and coalesce, at the expense of r.ratagouri and other
native shrubs. New bushes of currant occasionally arise via vegetative
reproduction but sheep ancl rabbits prevent this contributL:1g s:LgniEicantly
to the spread of curr:oi.nt into surrounding gras,->land . The presence
of seedlings and young plants in canopy gaps cause currant bushes suggests currant pdtches will be self- perpetuating while the present l and use continues. The clumping of plants rounJ the base of vegetation used by perching birds has be.en widely reported (e . g . Debusscht:' et _01 . 1982) . The cause of the pattetn can be more complex than the bird· ' defecations simply determining the position in which the plaot propagules germinate. gerrai11ate,. Favourable mic:roclimates near the base of trees (e.g. Gleadow 1981) and lack of competition from herbs, whid1 has been shown to inhibit the spread of brier (1'1olloy 1963) and Pirn!~~ contor~.0:. (Benecke 1967), may a1so be involved. The most import2nt factor in the spread of currant in the lower Waitaki appears to be the protection from grazing offered by the spiny matagouri, as Cockayne and The establishment, survival and growth of currant: would be quite different where it is not grazed. Ribes seeds may remain dormant for many years and require dne fairly long cold period to break dornancy (Schopmeyer 1974). This helps to explain the dens~ stands of currant that may appear after woodlots are felled. Currant can be a hindrance to newly established trees in these circumstances. These factors should be considered before planting currant near plantations for amenity or to provide food for honey bees. Adventive woody shrubs are of ten suppressed by taller native species (e.g. Druce 1957, Williams in press). No evi.dence for this trend, such as seedlings of broadleaf, was seen in the currant stands. On the other hand, saplings of syc21nore (~~~~ and larch (L8:_~ix dec~:dua) pro trucle above the currant in places. .Any taller vegetation that may succeed the currant will. pro'uably be composed of these and other ·wind-dispersed trees. ACirnOWLEDGEMENTS I thank Nr R. Blick for showing me the currant stands, l:-lr R. W. Cameron for providing accommodation, Nr R.P. Buxton for technical assistance and Niss A. Hodgins for drafting Fig. 1. Abrams, Leroy 1944. Illnstrated Flora of the Pacific States Vol IL Stanford University PreBs, C2lifornia. 635 pp. Bascand, L.D., Jowett, G.H. 1981. Scrubweed cover of South Isl2.nd agric.ultural and pastoral land. New Zealand Journal of 1982. Scrubweecl cov2r of South Island agriculture and pastoral land 2. Plant distribution and managerial problem status. New Zealand Journal of Benecke, U. 196 7: The ·weed potential of lodge.pole pine. Tussock Grasslands and Mountainlands Institute. Review 13: 36-L;3. Cockayne, L. 1928. Monograph on the New Zealand Beech Forests II. Daly, G.T. 1969: The biology of matagouri. of the New ZeaLmd ·weed Pest Control Conference: 195-200. Debussche, M.; Escarre, J.; Lepart, J.L. 1982: Ornithochory and plant succession in Mediterranean abandoned orchards. 255-266. Dingwall, A.R. 1962: The weeds of Canterbury. 15th Ne·w Zealand Weed an Druce, A.P. 1957: Botanical survey of an expe.riE1e.ntal .catchment, Taita, ----·------Research bulletin 2Lf. 1-81. of Central Victoria. II Dispersal, germination and establishment. Australian Journal of 30: 185-98. Healy, A.J. 1969: The adventive flora in Canterbury. In Knox, G.A. 11 (Ed.) "The Natural History of Canterbury • A.H. and A.W. Reed, Wellington. Pp 261-333. 2. 11itcJ1coclt2) C.L .. ; Cror1qt1ist, As 1973: flora of tl1e Pacif:Le 1'1ortJn-12st .. University of Washington, Seattle.. 730 P?· Leonard, W.F. 1962: Problems of scrub control. of the 1'1'·'oll - oy , .LIP • P • J • 19'J-t '-T'· • S,._,,,,.et' - 'o-L-i· ,_c:>~- "- - a "iD:orous~ ~ woody- weed of South Island tussock grassland. New Zealand Journal of 105--8. New Zealand :Meteorological Service 1978: Temperature normals 19Lfl-1970. Service Miscellaneous Publica 149: 1-22. ·~------·---- 1979: Rainfall parameters for stations in New Zealand and the Pacific Islands. New Zealand Service Hiscellaneous Publication 163. New Zealand Soil Bureau 1968: Soils of New Zealand. Part l. (1). -----.Soil Bureau______,___ __ Bulletin .., ___ ~~~-,.._~_,_,,_,,:,.,,,.._._.- __26 ~~ Primack, R.B. 1978: Effects of grazing on indigenous shrubs in tussock grassland at Cass, Canterbury, New Zealand. Schopmeyer, C.S. 1974. Seeds of woody plants in the United States. Agriculture Handbook No. 450. Forest Service, U.S. Department of Agriculture, Washington. Stern, Willimn L.; Sweitzer, Edward H.; Phipps, Robert E. 1970. Comparative anatomy and systematics of woody Saxifragaceae. Ribes. In (Ed) N.K.P. Robson, D.F. Cutler, H. Gregory. 11 New Research in Plant Anatomy". pp215-237. Williams, P.A. In Press. Secondary vegetation succession on the Port Hills, Banks Peninsula, Canterbury. New Zealand Journal of -10- frorn E:Lx: of f:ron Stz~n1cl lJo ~ 1 "c:. 3 L4. 5 6 J:,J_ ti t1td.e (m) 2Lf5 230 "i98 290 300 I.i~i..:m1 element Back: ~roe r:L'oe }Jack~ ':Poe slope slope 0 270 ·120 270 170 1 r, hO Lfo 25 .::; 20 co·ve:c of fiJ\ 1 1 1. 2 ± 0.2 \ . I 1 ~) 1 1 1 • .J + 0.7 (6) 1 1 0.5 "'!- 0,2 ( Uj0\ 3 2 2 1 1.2 ± o.s ( ) 1 1 1 1 1. 1 + 0.5 C1 ·r) ( 1 2 1 Lf 5 2. Lr -f· o.8 \ } 1 1 1 2 ·1 1 b 1 1 1 .).., . 0 + 0 . )··' (I,\ ··: '1/ 2 2 1 2 1 1 3 B:rce 3 3 CL. Cover%= 1, 1-5; 2, 20;- 3, ?1 ·-9- Plot Area -1 6-10 W-15 1 21-25 26-JO No. ( ) 'l 0.9 1 2 1-~0 2.2 3 3 2 3 30 3,0 1 7 1 1+ 1-fO 2.2 2 3 s )0 2.3 2 2 6 60 4.5 2 2 2 2 %of total 10 25 20 10 4 \ /r-~ '-) ",_ / \.-j _,,..,. I \ .-- \ bush "o' J '"'\ ...... \ I I / \. /' ' '- / Meyer 8 '. 800m &o 0 -, '- - Key soo _,/ \ __... Strea.ms ' -...... 3• Contours (m) O km '1 ; ... Homesteads ' \ Stands \ Fig.1 Location of the study area in the lower Waitaki valley. For an explanation of bush ffO \1 see the text.