RESEARCH REPORTS Fruit Had Fallen

Australian Weeds Vol. 2(4) Winter 1983 127 generally successful; less than 2"70 of shoots sampled eitheT carTied a ny Howers or showed ev id ence that ripe RESEARCH REPORTS fruit had fallen. Even in this minority of shoots, losses did not exceed 20"70, so eTTOTS due to fruit loss or incomplete fruit se t were negligible compaTed with the very hi gh natural variation among shoots. The numbeT of immatuTe fTuit formed was treated as fTuit production. FaT each shoot the following data were collected: diameteT of the stem at 20 em from the ground; two diameteTs of the canopy outline, at right-angles Fruit production by two species of privet, to one a notheT, from which the aTea of Ligustrum sinense Lour. and L. lucidum W.T.Ait., the canopy was calculated as an elli pse in Sydney wi th the two measured diameters; the height of the canopy at its highest point; an estimate of the percentage M. Westoby, J. Dalby and L. Adams-Acton projective foliage coveT (Specht, 1970) School of Biological Sciences, Macquarie Un iversity. North Ryde, due to other plants aT shoots, of any New South Wales 2113 species, over the shoot in question; an estimate of the numbers of fruit carried on the stem. This could not be made by complete census since the numbeTs Summary which Buchanan (1978) showed was fTequently exceeded 10' per shoot. readily eaten by biTds and dispersed up Fruit production by Chinese privet The estimate was made in the field by I (Ligustrum sinense) and large· leaved to km. This report quantities the fruit counting fruit numbers on sample production of both pTivet species as a privet (L. lucidum) was studied at 58 lengths of about 20 cm of fruiting function of some aspects of plant size sites in urban bushland in the northern bTanch and extTapolating the numbeT and illumination of the canopy at a suburbs of Sydney in 1978, and again peT unit length to the whole bTanch. number of sites in the nOTthern sub at eight of the sites for L. sinense in At 35 sites samples of soil from the uTbs of Sydney. 1979. L. sinense averaged 1300 fruits sUTface 5 em were coll ected; Ligustrum m" of canopy and the less widely dis· spp. have many roots in the sUTface tributed L. lucidum averaged 400 m·'. Methods soil. A feTtility index was obtained for Fruit production in both species was .... Both Ligustrum species fTequently these samples by bioassay. A tomato duced with increasing shade. Fruit pro sucker from the base, and multi seedlinr was grown in each of two Tep duction per unit area of canopy was shooted individuals are often mOTe licates of each soil in 10 em pots in the glasshouse. AfteT 18 days fTom emer less for smaller diameter than for larger common than those of tTee form. It is diameter shoots in L. sinense but was commonly not possible to tell which gence tops and roots were harvested not related to shoot diameter in L. Iuci shoots are part of a given clone, so we and dTied, a nd the Tela tive growth rate (g g" day") from emeTgence to haTvest dum. In both species there was great used the shoot ratheT than the genetic variation in fruit production between individual as the unit of study. The was used as an index of fertilit y. shoots of similar sizes, Bnd also con shoot was defined as a plant aT part of siderable variation in fruit production a plant which had a single stem at Results between sites, which was not correlated 20 em fTom the ground. with soil fertility as measured by a A total of 58 sites weTe visited once Differences between species crude bioassay. Sites with high L. sin each between 29 ApTil a nd 10 July, Ligustrum sinense was more common ense fruit production in 1979 were not 1978 at various locations in the north wi thin the aTea than L. lucidum. At 20 the same as those with high production ern suburbs of Sydney. At each site 10 sites L. sinense was the only species in 19~8. to 30 shoots of each privet species present, while L. lucidum occurred present were examined. In addition, 141 alone at only one site; both species were shoots were examined along road pTesent at 37 sites, generall y with Introduction verges or in private gardens, making a L. sinense being much mOTe a bundant The privets Ligustrum sinense Lour. total of 363 shoots of L. lucidum and than L. lu cidum. Both species weTe and Ligustrum lucidum W.T. Ail. are 1127 of L. sinense. At each site shoots found on remaTkably vaTied soil s, among the more important urban were chosen to Tepresent a Ta nge of Tanging from neaTly pure sands weeds of the Sydney area (Bradley and sizes, but were not selected in any other through friable loa ms to nearly pUTe Bradley, 1967). They are abundant both way. In May and June 1979 eight of the clays, a nd there was no diffeTence be in gardens and in urban bushland, sites studied during 1978 (aTbitrarily tween the species in the fertilit y index forming very dense stands a nd appaT chosen) weTe Tevisited and 20 shoots of of sites wheTe they occuTred (L. sillellse ently excluding native species. Both L. sinense examined at each to com 0.187 ± 0.058 vs. L. lucidum 0. 185 ± local authorities and amateuT bush pare fruit production in consecutive 0.061; t = 0.11, df = 60, P>0.5). protection organizations now make yeaTS. The average properties of the effoTts to contTol them. Adamson In both years we aimed to sample sampled shoots of both species over a ll (1977) suggested that a factoT con shoots while they caTried immatuTe si tes a re summaTized in Table I. It tributing to theiT success and Tapid fruit, afteT fruit set but befoTe fTuit should be noted that these stems we Te spread is a heavy production of fruit, ripened and fell aT was eaten. This was not a fully randomized sample wi th re- 128 Australian Weeds Vd . 2(4) Winter 1983 Tablel Average properties of sampled shoots of Liguslrum lucidum and .05). The data suggest that for L. sin L. sinense in bushland in northern Sydney ense the response takes the form of de pressed fruit yield in the smallest stems Species (Figure I). Characteristic L. lucidum L. sinense Fruit production per unit canopy Meon S.E. Mean S.E. area was reduced gradually and pro gressivelyas percentage cover over the total fruit numbers per shoot 2300 360 2800 340 canopy (broadly speaking, the degree fruit numbers per square metre of canopy· 400 45 1300 130 stem diameter (cm at 20 em)· 9.9 0.30 3.4 0,07 of shading) increased (Figure 2); full 1 canopy area (m ). 5.7 0.25 2.4 0.09 cover reduced fruit production by canopy height (m)* 4.6 0.07 2.7 0.04 50"7. to 70% compared with full light percentage cover over canopy· 33 1.5 42 0.95 in both species. Since smaller shoots were generally Significant difference between species is indicated by • (P<.OOI). more shaded, the apparent effect of shade might actually have been an effect of shoot size or vice versa. An spect to size. However, far more small dum, with the result that average pro analysis of covariance of these factors stems were left unsampled for L. sin duction per stem was similar in the two (Table 2) showed that shoot size and ense than for L. lucidum. The tendency species. shading explained substantially differ of L. lucidum to have larger stem dia ent parts of the variance in fruit pro meter, canopy area and height is there duction per square metre for L. sin fore certainly real, while the tendency Factors affecting fruit production per unit canopy area ense, but for L. lucidum the weak cor of L. sinense to be slightly more shaded relation of fruit production per unit than L. lucidum may have been a pro Fruit production per unit canopy area canopy area with stem diameter ap duct of its generally smaller size. Ligus was positively correlated with stem dia pears to have been a side-effect of the meter in L. sinense (r 12 .08, P < Irum sinense produced more fruit per = lesser shading of larger shoots . unit area of canopy than did L. luci- .01), and in L. lucidum (r12 = .133, P< Differences between sites and years There was substantial variation be tween sites in mean fruit production per unit canopy area, both in 1978 and in 1979. This variation was not cor related with the fertility index of the sites (r2 = .09, n = 27 for L. luci dum, r' = .01, n = 34 for L. sinense), nor with any other feature of the sites 12 6 that we observed. The sites with heavy 2400 fruit production were not the same for the two species. When L.' sinense was resampled at 8 sites in 1979, there was no tendency for the same sites to have 2000 25 the highest fruit production per square metre of canopy in both years (F, = 1.75, df = 7, 251, P > O.lO). For these reasons we believe the variation be 1600 tween sites was largely due to the varia tion between individual stems. This 39 variation was- very largt; as is common 44 0 of fruit production (Harper, 1977); for 1200 both species about 5 % of the shoots t sampled accounted for about 60% of the total fruit production observed.

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