Native provenances of Pinus radiata in New Zealand: performance and potential.

Provenance testing of Pinus radiata in New Zealand has run in parallel with an intensive breeding programme that exploited local 'land-race' stocks. The species was long known to occur at three places on the Californian mainland coast, AAo Nuevo (Lat. 37"N), Monterey (36.5') and Cambria (35S4), but has since proved to include the pines of Guadalupe Island (297 and Cedros Island (28') off the Baja California Peninsula. Very limited provenance testing began in the 1950s, with comprehensive testing on a few sites in the mid-1960s, followed in 1980 by a countrywide series on 23 sites involving just the Californian mainland provenances. Different profiles of site adaptation among provenances have emerged. AAo Nuevo and Monterey are the best adapted overall to New Zealand conditions, but Aiio Nuevo is much less adapted to P-deficient clays, yet better adapted to cold, snow-hazard sites. Cambria is susceptible to needle-casts, shoot dieback, and frost and snow damage, but has toleratedpoor soils. Guadalupe, while showing some adaptational problems and slower growth as a pure strain, has very straight stems and 10% higher corewood density, and has given very promising hybrids with local stock. Cedros, as a pure strain, is much slower growing with severe adaptational problems, although hybrids have grown well. Local stocks are evidently 'mixtures' that have originated mainly from AAo Nuevo (50-75%), the balance from Monterey. To start the breeding with local stocks proved right, but native-provenance material still promises to make valuable contributions. In particular, Monterey material may boost edaphic tolerances, and Guadalupe hybrids may have a significant place. Introduction Pinus radiata breeding in New Zealand began on the twopronged assumption that provenance variation would be unimportant and that local 'land-race' stocks would suffice as a genetic base, although a very limited provenance trial was planted on two sites in 1955 (Shelbourne et al., 1979). Early provenance trial results in Australia (Fielding, 1961), while showing some provenance variation, endorsed the use of local stocks. Bannister (1959), however, stressed that the species was actually more widely distributed than previously thought, since it included the pines of Guadalupe Island and possibly those of Cedros Island as well. Thus it comprised no fewer than four and possibly five discrete natural populations (provenances) among which there were some marked differences. He postulated that by importing and intercrossing fresh material for future breeding purposes tree breeders could enhance adaptation to local conditions, give greater scope for long-term genetic gains, and confer additional flexibility should utilisation needs change in the future. Accordingly, Bannister (1 963) instigated a large provenanceprogeny trial (Burdon and Bannister, 1973; Burdon etaL., 1992b), which was planted in 1964, -5 and -7 on two contrasting sites in Kaingaroa Forest. This contained 50 seed-parent progenies from each of the five native populations, Aiio Nuevo (Lat. 37"N), Monterey (36.5") and Cambria (35.57, on the Californian mainland coast, and Guadalupe Island (29" and Cedros Island (28" off the 1 New Zealand Forest Research Institute, Private Bag 3020, Rotorua. Baja California Peninsula. The inclusion of Cedros material as P. radiata has been vindicated (Burdon, 1992), although its slower growth posed major experimental problems (Burdon et al., 1992b). This experiment, called the "Genetic Survey", thus sampled almost the full natural range of the species, and was designed to evaluate the genetic variability at the levels of populations, localities within populations, and individual trees. Also included were similar samples from two New Zealand populations (Kaingaroa and Nelson) that were thought to typify local 'land-race' stocks. Spare planting stock was used for three small trials designed purely to compare provenances at three other sites, Gwavas (Hawke's Bay foothills), Santoft (Manawatu sand dunes) and Golden Downs (Moutere gravels) (Shelboume et al., 1979). At the same time, and since then, some inter-provenance hybrids were planted in tests, especially hybrids of the two island provenances with New Zealand material. From the trials planted in the 1960s came a clear picture of the Californian origins of the particular local stocks, predominantly Aiio Nuevo (much the smallest of the Califomian mainland populations) with the balance being Monterey. Thus the representation of the natural range of the species, within those Kaingaroa and Nelson stocks, was very incomplete and unbalanced. There were also indications that the under-represented Monterey provenance had some better soil tolerances, which was consistent with the existence of some infertile sites at Monterey, and with the presence of strong tree-to-tree variation in local stock in soil tolerances (Burdon, 1971, 1976). While the other populations showed considerable adaptive limitations as pure strains (Burdon, 1992), some of the inter-provenance hybrids were very promising, notably those involving Guadalupe and local stock. It was decided to mount a further seed collecting expedition in California to allow far more thorough provenance testing of P. radiata in New Zealand, and to augment the available native-population gene resources. In 1978 a joint Australia-New Zealand expedition took place (Eldridge, 1978). New Zealand's involvement was confined to the Califomian mainland stands of P. radiata, and from that New Zealand obtained unpedigreed seedlots from various locations within the native stands. The collection was used to establish countrywide provenance trials and some larger blocks of gene-resource plantings. This paper is concerned primarily with summarising results from those trials and discussing the future implications of them and the results from other trials of native-provenance material for New Zealand forestry. It is planned to publish the results elsewhere in much more technical detail. Material and Methods The 1978 collection produced seedlots from a total of 13 localities which were believed to represent ecological subdivisions of the populations (four, six and three at AAo Nuevo, Monterey and Cambria respectively). On average, such seedlots represented bulked seed from 40 trees (range 22-70) in a locality, each locality having been grid sampled as far as was practicable. Three regional land-race stocks, 'Kaingaroa', 'Nelson' and 'Southland', were chosen to provide New Zealand controls, these being very . predominantly from select-tree seed collections within supposedly unimproved stands. Of these, the Kaingaroa and Southland