New Zealand JOl/rnal of Botany, 1978, Vol. 16: 413-5. 413

A note on pollen dispersal in Canterbury, New Zealand

N. T. MOAR and J. V. MYERS

Botany Division, DSIR, Private Bag, Christchurch, New Zealand

(Received 4 May 1978)

Myers (1973) discussed the dispersal of NotllO­fagus pollen on the basis of a pollen trapping pro­gramme at Bankside and Eyrewell Scientific Reserves in central Canterbury. These reserves are 60 km and 14 km, respectively, east of the nearest Nothofagus forest which grows on the ranges at the western edge of the Canterbury Plains (see fig. I, Myers 1973). Bankside Reserve is dominated by scrub of Lepto­sperrnl/rn ericoides and grassland of Festllca novae­zelandiae and Notodanthonia clavata (Molloy 1970). There are three major plant communities in the Eyre­well Reserve - low forest of L. ericoides, shrub land of the same species with L. scoparillrn and Porna­derris phylicifolia var. ericifolia and grassland similar to that at Bankside (Molloy & Ives 1972).

Myers used impact and Tauber traps and al­though his trapping programme was incomplete he was able to show that Nothofaglls pollen frequencies were generally higher at Eyrewell than at Bankside where values of < 10% were usual. However, at Bankside the highest frequency (21 % of total pollen counted) came from a lichen taken from the top bar of an old farm gate and a similar value (18%) was obtained from the Tauber pollen trap on 17 Novem­ber 1971.

The trapping programme was continued, not without interruption, into 1974. This note extends earlier observations on Nothofagus pollen dispersal in Canterbury and comments briefly on other pollen types represented in the pollen rain.

At Eyrewell low NotllOfaglis pollen frequencies in 1972-73 are followed by much higher values in the following season (Fig. 1). The 1973-74 record is incomplete, but the beginning and end of the main pollen shed are clearly indicated. The high values for 1973-74 correspond to earlier results for Nothofagus in Canterbury (Licitis 1953). This peak is not evident at Bankside although the rising curve for the impact trap in October 1973 suggests that its absence may result because of an unforseen break in the trapping programme. In any event the Bankside record for 1972~73 reflects to a lesser degree the trend evident for that season at Eyrewell.

The difference between the two flowering seasons at Eyrewell is striking. Botany Division, DSIR, records show that NotllOfaglls flowered well during 1973-74 and that species in the genera Aciphylla, Chionochloa, Cordy line, and PllOrrniurn also flowered abundantly at that time. These last four plants flowered poorly during 1972-73 and although there are no special records for NotllOfagus it is inferred that it followed the same trend.

These observations are supported by data on Nothofagl/s seed production from the Craigieburn Range and at Mt Thomas. Total seedfall in 1973 was negligible, it was many times better in 1974, but the best year in recent times was 1971 for which season pollen records are lacking (J. Wardle 1974, pers. comm.; Table 1). The seedfall for 1972 was better than in 1973 and this may be reflected by the higher values recorded by Myers (1973) at Bankside for spring 1971. Similar trends from other South Island sites are reported by Franklin (1977).

Poole ([955) notes that heavy flowering of Nothofagl/s is usually preceded by a hot and often dry summer. According to weather summaries pro­vided by the Meteorological Office at Harewood, the summers of 1971 and 1973 were warmer and drier than usual and the summer of 1972 was cool and dry. This pattern seems to correlate with the rela­tively good flowering seasons of 1971-72 and 1973-74 and the poor season of 1972-73. A similar pattern is recorded for the 1951 season when a warmer than average summer preceded heavy flower­ing in many South Island districts (Poole 1955). However, this pattern is not a constant one and our data do not establish a formal correlation between climate and pollen production.

PoIlen dispersal itself is affected by other factors such as wind, rain, topography and distance from pollen source. The differences between Bankside and Eyrewell may be attributed to some of these. Eyre­well is nearer the pollen source than Bankside and the wind regime at these sites is different; both are influenced by westerly winds, but Bankside is also affected by easterlies although not necessarily to the

414 New Zealand Journal of Botany 16, 1978

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Fig. 1 Data relating to pollen trapped at Bankside and Eyrewell. The broken line represents data from the impact trap, the solid line from the Tauber trap. Low pollen counts arc! indicated by arrows and the rare occur­rences of Pomllderris and Acacia pollen are indicated by the small circles.

Moar & Myers-Pollen dispersal

Table 1 Total seedfall at stations in the Craigie burn Range and at Mt Thomas, Canterbury. Data from J. A. Wardle (1974, pers. comm.).

TOTAL SEEDFALL Craigieburn Range Mt Thomas

Year I 340 m a.s.!. 1036 m a.s.!. 500 m a.s.!.

lY71 1972 1973 1974

23038 661

36 8565

18614 298

42 5258

15458 90

826 1 67J

same extent as Christchurch. Licitis (1953) suggested that fallo'Jt in Christchurch of Nothofagus pollen from the foothills occurred when north-west winds carrying pollen met coastal easterlies. More regular sampling combined with a close study of daily weather patterns is needed to resolve this question.

The record for other pollen types, e.g., Pinus and Cllpressus (Fig. 1), shows similar differences between sites to those noted for Nothofaglls. Thus in the spring of 1972 Pinus pollen was well represented at Bankside, but not at Eyrewell, whereas high fre­quencies were recorded at both sites the following (1973) spring. Myers (1973) noted a similar differ­ence and commented that scarcity of Pinus pollen at the Eyrewell station was unexpected because the pollen traps were only 200 m west of pines in the Eyrewell ~tate Forest. The prevalence of strong westerly winds during the sampling period was offered as an explanation for this and according to New Zealand Meteorological Service (1973) records winds were more variable the following year.

The pollen curves for Cllpressus and Gramineae at both stations conform to the pattern established by Clark (1951) and Licitis (1953) for other parts of New Zealand. Licitis does not record Lepto­spermum pollen from her Christchurch station, which contrasts with results from Bankside and Eyrewell where high frequencies record the main flowering period of L. ericoides in early summer. Leptospermum i~ insect-pollinated and pollen dispersal by wind is not likely to occur over any great distance.

The difference in results between Tauber and impact traps (Myers 1973) is not always consistent, 1S shown by the frequencies for Cupressus pollen, although highest values are generally recorded for the impact trap. In some cases very high values are recorded from the Tauber trap, e.g., Leptospermum 79% total pollen, 23 January 1974 at Eyrewell and 80% total pollen, 9 February 1974 at Bankside. On both these days insect remains were found in the trap and it is possible that the insects had been work­ing Leptospermum before being trapped and this may account for the high values.

415

Only three Pomaderris pollen grains were re­corded at Eyrewell (Fig. 1) which does not reflect the role of Pomaderris in the reserve where it is recorded as abundant in the shrubland vegetation (Monoy & Ives 1972). Similarly the few records of Acacia pollen at Bankside give no indication that numbers of Acacia plants grow within 2 km of the reserve.

ACKNOWLEDGMENTS

The cO-lJperation of the Commissioner of Lands, Department of Lands and Survey, in providing access to the reserves, permission from Dr J. Wardle, Forest Research Institute, for use of unpublished data re­lating to seed. fan, and comf!1ent by Dr P .. Wardle, Botany DiviSIOn, on flowenng patterns IS much appreciated.

REFERENCES

CLARK HELEN E. 1951: An atmospheric pollen sur­v~y of four centres in the North Island, New Zealand, 1949-50. N.Z. Journal Science and Technology 33B: 73-91.

FRANKLIN, D. A. 1977: Beech seedfalls in some South Island lowland forests. Beech Research News No.5: 9-13.

LICITlS, RASMA 1953: Air-borne poll~n and spores sampled at five New Zealand statIons, 1951-52. N.Z. Journal Science and Technology 34B: 289-316.

MOLLOY, B. P. 1. 1970: Banksid.e-a new scientific reserve on the Canterbury PlaInS. Proceedings of the New Zealand Ecological Society No. 17: 47-51.

MOLLOY, B. P. J.; IVES, D. W. 1972: Biological reserves of New Zealand I. Eyrewell Scientific Reserve, Canterbury. N.Z. Journal of Botany 10: 673-700.

MYERS, J. V. 1973: A note on the dispersal of NotllO­fagus pollen in Canterbury, New Zealand. Ibid. /1: 311-6.

NEW ZEALAND METEOROLOGICAL SERVICE. Observa­tions for 1973. New Zealand Meteorolo/:ical Ser­vice Miscellaneous Publicatiolls 109. 108pp.

POOLE, A. L. 1955: Recent southern beech flowerin~ seasons. New Zealand Journal of Forestry 7(2): 880-9.

WARDLE, J. A. 1974: The life history of mountain beech (Nothofagus solandri var. elinortioides). Proceedings of the New Zealalld Ecological Society 21: 21-6.