Dispersal and Destruction of Seed in Central North Island Podocarp Forests

48 McNEIL: MAN, DEER AND VEGETATION IN MICHIGAN New Zealand has a similar history of log- REFERENCES ging, followed by the plough or fire, or similar disturbances. In addition, since all the BAIRD, ''Y., 1954. This is our Michigan. Federated ungulates have been introduced in a short Publications, Battle Creek, Mich. time, biologically speaking, the native plants BALD, F. C., 1954. Michigan in four centuries. Harper are generally ill-adapted to maintain them- Bros., N.Y. selves under heavy browsing pressure. An JENKINS, D. M., 1961. Michigan's deer industry. Mich. inevitable imbalance between animal numbers Cons. 30: 17-21. and the amount of available food has resulted. The eventual status of deer in New Zealand JENKINS, D. R., and BAHTLETT,1. H., 1959. Michigan may be much the same as in Michigan: (1) whitetails, Game Div., Dept. Cons., Lansing. browsing pressure by ungulates will continue MICHIGAN DEPARTMENT OF CONSERVATION, 1960. strong for some time, resulting in changes in Twentieth biennial report, 1959-1960. Mich. Dept. species composition of various plant communi- Cons., Lansing. ties; (2) continued control measures will PERRY, O. H., 1899. Hunting expeditions of Oliver reduce deer numbers and inevitably an altered Hazard Perry of Cleveland, verbatim from his flora and fauna will evolve (some native diaries. Marion Press, Jamaica, N.Y. species probably becoming rare or extinct); RYEL, L. A., and FAY, L. D., 1962. Deer biological data (3) eventually a balance between plant and 1961-62. Report No. 2387. Game Div., Mich. Dept. animal numbers (probably artificially de- Cons. pressed by shooting) will occur; (4) political VERME, L. J., 1962. Mortality of white-tailed deer fawns and social problems will continue to play an in relation to nutrition. In Proc. 1st Nat. White- important role in natural resource manage- tailed Deer Diseasf! Symposium, Univ. of Georgia, ment. Athens, Georgia: 17-28,37-38. DISPERSAL AND DESTRUCTION OF SEED IN CENTRAL NORTH ISLAND PODOCARP FORESTS A. E. BEVERIDGE Forest Research Institute, Rotorua INTRODUCTION Seed dispersal and destruction have been Over the past six years studies have been studied by observing the feeding habits of birds carried out, mainly in dense podocarp stands and by examining seed and droppings on the of Pureora and Pouakani Forests, to gather ground, on collection sheets, and in seed traps, information about the periodicity, abundance, some of the latter being rodent and bird proof. and soundness of seed crops, the animals that Seed has also been fed to captive rats and disperse or destroy seed, and how they do so. insects. Recently the populations of rodents The ultimate objective is to find out what part in different forest types have been studied by each bird, rodent or insect plays in assisting systematic trapping with break-back traps or limiting regeneration of timber species. baited with peanut butter. In January 1962, at Pureora, P. C. Bull of the Animal Ecology Division, D.S.I.R., demon- METHODS strated that mist nets can be used in native Seed crops were assessed subjectively until forest to capture birds so that their role as seed 1961, when pairs of seed traps were placed dispersers can be studied. beneath crowns of permanent seed trees of rinlu (Vacrydium cupressinum), totara (Podocarpus RESULTS totara), kahikatea (Podocarpus dacrydioides), SEED CROPS AS A FOOD SUPPLY mira (Podocarpus jerrugineus) and matai Podocarps (Podocarpus spicatus). Since 1961, the num- There is a marked periodicity in fruiting ber of sound and defective seeds collected in amongst some podocarp species but no regular the traps has been counted annually. interval between good seed crops has been BEVERIDGE: DISPERSAL AND DISPOSAL OF PODOCARP SEED 49 observed (f.linds and Reid iM;;\. In any year, n1pen)ng oj seed crops one or several species may fruit well in a par- At Pureora Forest, the earliest ripe fruit is ticular locality, or there may be few sound found in December on second-growth species seed of any species in the forest interior. In such as fivefinger and fuchsia. Wineberry and Pureora Forest, seed-crop ratings have been the first tawa berries ripen in February. Ripe recorded as follows for the past 10 years: rimu seed with fleshy receptacles is available rimu: good crops in 1954 and 1958; fair crop in 1962; from mid March to May when the bulk of the kahikatea: good crops in 1955, 1960 and 1963; fair kahikatea, miro and totara crop ripens. Most CfOp in 1958; of the shrub-hardwood species fruit from March totara: light crops annually; to June but berries of some species such as mira and tawa (Beilschmiedia tawa): annual crops supplejack (Rhipogonum scandens), Coprosma fluctuating in quantity; robusta, broadleaf (Griselinia littoralis) and matai: no good seed crops, only a few seed on horopito (Pseudowintera spp.) may be avail- occasional trees from 1953 to 1962; fair CfOp in able throughout the winter. 1963; The hard-coated seeds of miro have taken hinau (Elaeocarpus dentatm) and rewarewa {Knightia at least three years to germinate in the F.R.I. excelsa}: good crops annually. nursery and some matai seeds have taken two Total yields of seed have been estimated for years (D. S. Preest pers. comm.). In forest, mature trees with deep, vigorous crowns con- seed of these species may remain dormant on sidered to have a heavy crop. Estimates for the ground for two or more years. Kahikatea individual trees in Pureora Forest, based on seed and most of the rimu and totara seed seed collections, are: dmu, 40 lb. ripe seed and germinates in the late spring and summer rcceptacles yielding 4 lb. of clean, sound seed after seed fall. (200,000); miro, 100 lb. ripe berries (32,000); SEED DISPERSAL BY BIRDS kahikatea, 1,800 lb. ri e seed and receptacles At Pureora there is a marked concentration yielding 300 lb. 0F clean, sound seed of fruit-eating birds during a good podocarp (4,500,000). In calm weather, comparatively fruiting season. The most active dispersers of few seeds of rimu, kahikatea or totara fall with podocarp seed are New Zealand pigeons the ripe receptacles still attached as many seeds (Hemiphaga novaeseelandiae), tuis (Prost he- and receptacles are eaten in the crowns of the madera novaeseelandiae) and bellbirds trees. (Anthornis melanura). These birds swallow Production and ripening of seed of the bath fleshy receptacles and seed of podocarps podocarp species may vary considerably in the but digest only the pulp, the seeds passing ~ame forest, even within areas of similar forest intact through the digestive tract. All three type, aspect, and altitude. The quantity and species eat the succulent fruits of a wide range quality of seed borne by individual trees in of shrub hardwoods. White-eyes (Zosterops any locality also varies greatly so that very lateralis) are the most common birds in the intensive sampling would be required to regrowth of logged forest at Pureora where they reliably estimate seed fall per acre. feed extensively on succulent fruits such as those of wineberry; they also swallow whole Shrub-hardwood species less succulent berries such as those of lance- wood (Pseudopanax crassifolium) and five- These appear to produce seed annually bul finger. the quantity varies according to forest type. During the fruiting season, pigeon droppings Species such as mahoe (Melicytus ramiflorus), may consist entirely of podocarp seed plus pate (Schefflera digitata) and fivefinger fibrous parts of the fruit. Large droppings (Neopanax arboreum) are present in dense attributed to pigeons have contained up to 100 podocarp forest but bear little seed except in kahikatea seeds or 12 matai seeds. Miro and large canopy gaps; in these forests, podocarp tawa seeds cleaned of pulp are dropped con- seed is the main food source for seed-eating tinually by pigeons feeding in fruiting trees; birds, rodents, and insects. When such forest thus mira seedlings are commonly found is clear felled, the regrowth consists mainly beneath tawa trees. After feeding, pigeons of berry-producing shrubs such as fuchsia may perch in nearby emergent trees of any (Fuchsia excorticata) and wineberTY (A risto- species, and large droppings found beneath telia serrata). these trees are probably from perching birds. 50 ANIMAL MODIFICATION OF NATIVE VEGETATION Large kamahi (Weinmannia racemosa) in seed. The gut of a thrush (Turdus ericetorum) patches of low shrub hardwoods are frequently shot at the forest edge in May contained sound associated with groups of podocarp seedlings. kahikatea seed. Seeds found in pigeon droppings are always In a preliminary trial with mist nets set sound. up at the margin of Pouakani Forest, 22 birds were caught, including five white-eyes, five In 1960, an exceptionally heavy crop of blackbirds (Turdus merula) and two thrushes. kahikatea seed at Pureora afforded the oppor- Some of the fruit-eating birds had been feeding tunity to observe mass dispersal of seed from on tutu (Coriaria arborea), fuchsia, and virgin forest into adjacent cutover forest. Tuis Muehlenbeckia australis, and seedlings of all gathered in hundreds where kahikatea was these species were grown from seed contained dominant over 10 acres of a large block of in droppings of birds caged for a short period dense podocarp forest. There were also smaller before release. That 178 fuchsia seedlings numbers of bellbirds and pigeons. Residual were grown from the contents of a single trees in adjacent cutover forest were constantly dropping shows the importance of the black- visited by tuis in particular, and logs and bird as a seed distributor. stumps in the open to a distance of several Evidence of effective seed dispersal by birds chains from the forest edge were sprinkled over the past 50 years was obtained by a 2t% with sound kahikatea seed deposited by flying sampling of 160 acres of fire-induced second birds.

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