~~~· FOREST RESEARCH INSTITUTE

!NN511NCF FRI BULLETIN No. 124 FORESTRY

INTRODUCED FOREST TREES IN NEW ZEALAND: RECOGNITION, ROLE, AND SEED SOURCE

10. Ponderosa and Jeffrey pines Pinus ponderosa P. Lawson et Lawson Pinus jeffreyi Grev. et Balf.

R.D. BURDON, J.T. MILLER and F.B. KNOWLES This FRI Bulletin series was compiled for people with an interest in the introduced trees of New Zealand, such as foresters, farm foresters, nurserymen, and students. It includes: l. PirlUs nigraArn.-European black pine 2. Pinus contorta Loudon-contorta pine 3. The larches-Larix decidua Miller, Larix kaempferi (Lambert) Carr., Larix x eurolepis A. Henry 4. Pinus mugo Turra-dwarf mountain pine; Pinus uncinata Mirbel-mountain pine 5. Pinus attenuata Lemmon-knobcone pine 6. The spruces-Picea sitchensis (Bong.) Carriere, Picea abies (L.) Karsten, ornamental spruces 7. The silver firs-Abies spp. 8. Pinus pinaster Aiton-maritime pine 9. 111e cypresses-Cupressus spp.; Chamaecyparis spp. FRI BULLETIN No. 124

INTRODUCED FOREST TREES IN NEW ZEALAND: RECOGNITION, ROLE, AND SEED SOURCE

10. PONDEROSA AND JEFFREY PINES Pinus ponderosa P. Lawson et Lawson Pinus jeffreyi Grev. et Balf.

R.D. Burdon, J.T. Miller and F.B. Knowles

MINISTRY OF FORESTRY, FOREST RESEARCH INSTITUTE, PRIVATE BAG 3020, ROTORUA, NEW ZEALAND

1991 THE AUTHORS

Rowland Burdon (B.Sc. B.A. (For.), Ph. D.) and John Miller (B.Sc.(For.)) are scientists working with the Genetics and Tree Improvement section of the Forest Research Institute, Rototrua. Barbara Knowles (B.Sc.) is a scientist working in the FRI herbarium.

ISSN 0111-8129 ODC: 174.7 PiT1Us ponderosa (931): 232 Shelterbelt of Pinus ponderosa aged 28 years in the MacKenzie country near Mt. Cook CONTENTS

Abstract 1

Introduction and Histo:ry Histo:ry in New Zealand 1 Natural Distribution 2 Provenance Variation 2 New Zealand Provenance Trials 4 Pests and Diseases 8

Recognition Pinus ponderosa P. Lawson et Lawson -ponderosa pine 9 Pinusje.ffreyi Grev. et Balf. - Jeffrey pine 10

Role of the Species Present Extent 11 Growth and Yield 14 Wood Properties and Uses 15 Regeneration 17 Siting 17 Silviculture 18 The Future Role of the Species 19

Seed Source 21

Seed Users' Guide A Collection and Extraction of Seed 21 B. Nurse:ry Practice 22 C. Recommended Seed Sources 22

References and Further Reading 22

Acknowledgements 23 ABSTRACT

This booklet, the tenth in the Bulletin No. 124 series, provides an account of Pinus ponderosa and Pinus je.ffreyi in New Zealand. It covers their introduction and history, variation, and recognition, and their performance and role as exotic forest species. Information is also provided on the location and quality of current local seed sources, and on collection and handling of seed.

KEYWORDS: Pinus ponderosa, Pinusje.ffreyi, exotic species, New Zealand, taxonomy, provenances, seed sources.

INTRODUCTION AND HISTORY

Pinus ponderosa is native to western North America where it was formerly one of the most widespread and highly valued species of the virgin forests, and today is still an important component of second-growth forest. Pinus je.ffreyi has a more restricted natural range than P. ponderosa, being found only in California and adjoining states; where their ranges overlap the two species occur in mixed stands. Pinus je.ffreyi closely resembles P. ponderosa in appearance and wood properties and for a long time was regarded as a variety of this species.

Of the two species, only P. ponderosa has been planted widely within New Zealand. For over 30 years it ranked second only toP. radiata in planted area; since the 1960s, however, its role has declined dramatically. These species are now of interest for planting only in the South Island, in areas where there is a semi-continental climate (i.e. cold winters and dry hot summers) - principally inland areas of Canterbury and Otago.

History in New Zealand

Pinus ponderosa was first introduced to New Zealand by T.H. Potts in 1865. He brought in at least two forms to Lyttelton, one under the name Pinus benthamiana. In 1868 both these forms were recorded at Hutt, near Wellington (Weston, 1957). J.B.A. Acland, who founded the Mt. Peel sheep station, imported P. ponderosa from England, and planted it in the 1860s. It was also planted at Albury, South Canterbury, in 1869. Repeated seed importations have since been made, including a number by Sir James Hector, Director of the Geological Survey, which were widely distributed during the 1870s. The ease of establishment and hardiness of P. ponderosa resulted in its widespread use in scattered shelterbelts and woodlots in the central South Island where it still features prominently. In 1890, it was planted in Raincliff Forest, South Canterbury, and from 1891 in Selwyn Plantation Board areas. Before World War I, it was planted in State Forests at Naseby and elsewhere, but the main plantings, of about 27,000 ha, were made by the State Forest Service during the 1920s and 1930s from fresh seed importations. In 1955, the total area of P. ponderosa stood at nearly 40,000 ha, 80% of which was concentrated in the Volcanic Plateau of the central North Island. Despite early recognition of provenance variation in P. ponderosa, over 90% of the plantings made during the 1920s to the 1940s consisted of inferior, or even grossly inappropriate provenances. This resulted from a policy of giving preference to imports from Commonwealth countries, the Canadian Forest Service being the principal supplier of P. ponderosa seed during this time.

In the mid-1960s the fungus Dothistromapini, which causes needle blight in many pine species, arrived in New Zealand, and P. ponderosa was one of the species most severely 2 affected. Subsequently, research carried out in the late 1960s and early 1970s showed conclusively that, with appropriate establishment and nursery techniques, the faster-growing P. radiata could be established on most of the difficult growing sites previously relegated to P. ponderosa. Since then the tendency has been to rapidly utilise the main areas of P. ponderosa and replant with P. radiata.

Pfnus jeifreyi was first recorded in New Zealand growing near Wellington in 1865 (Ludlam 1868). Subsequently, several seed importations were made, including at least one by Hector, but only small, widely scattered plantings resulted, for example those at Raincliff Forest (1890), and at Waiotapu, Hanmer and Naseby State Forests (1901-1910). About 20 ha of P. jeifreyi were planted in the 1960s at Naseby and Ranklebum State Forests, using locally collected seed, but the species has never been planted on a large scale.

Natural Distribution

Pfnus ponderosa is one of the most widely distributed Pfnus species in North America. As shown in Figure 1, in the west its range extends from just north of the Mexican border (Lat. 33° N) to southem British Columbia (Lat. 51 o N) ; and in the east from the Dakotas into Nebraska (where it reaches Long. 99° W), south to Colorado and New Mexico (to Lat. 33° N). The more southerly 'var. arizontca' is now treated as a separate species, P. artzontca. Within the general boundaries of its distribution, P. ponderosa tends to have a discontinuous occurrence, particularly in the southem part of its range. It is absent from a large arid area east of the San Bemardino Mountains, the Sierra Nevada and the Southem Cascades.

Within the vast geographic range of P. ponderosa, there is great environmental diversity. The species is found at altitudes ranging from less than 300 m in the Coast Ranges, to over 2750 m in the Sierra Nevada, and to around 3300 m in the southem Rocky Mountain areas, tending to be at higher altitudes in the lower latitudes. It grows on a wide variety of soil types, including soils of igneous, metamorphic and sedimentary origin, but is generally absent from serpentine areas. Precipitation (as rain and snow) varies considerably within the species' natural range. In the west, it is up to 1700 mm or more and tends to fall mainly in winter. In the east it is generally less (sometimes as low as 300 mm) but is more evenly distributed through the year. Winter snowpack occurs at higher altitudes. Under relatively low precipitation P. ponderosa often occurs as pure stands, otherwise it tends to be associated with several other species, notably westem larch (La.rix occidentalis) and Douglas fir (Pseudotsuga menziesiO. A fire-induced parkland stand structure clearly helps the species to remain healthy on dry sites.

Pfnus jeifreyi has a much more restricted range than P. ponderosa. It extends across the Sierra Nevada in Califomia with scattered populations in the Coast Range of Califomia and southwestem Oregon, and also occurs in the higher mountains of southem California and northem Baja Califomia, Mexico. The natural range is bounded roughly by latitudes 29° N and 43° N in the southeast, and by longitudes 117° Wand 124° Win the northwest (Fig. 1).

Although the two species overlap considerably in the Sierra Nevada, P.jeifreyi tends to occur at higher altitudes (to 3100 m) and to extend slightly further east than P. ponderosa. In the Coast Range it tends to be concentrated on serpentine soils.

Provenance Variation

Pfnus ponderosa shows extreme variation between populations This variability has led to the recognition of at least two varieties, and of races within varieties. Additionally, within races, there is continuous (or 'clinal') variation with altitude and latitude. 3

I I I

I Alberta I Saskatchewan I Manitoba I

Nevada

' ' '\ ' '\ " '\ ---_I_----- ' ' ~ I> '\ .. 1___ _9Js.l'!b<;ma '\ .\ I I , 1 I I I I New 1 I ., Mexico • ~, : Texas

-)< PINUS JEFFR EYI

•X ISOLATED OCCURRENCES Chihuah ua P. PONDEROSA + P. JEFFR EYI I I • KILOMETRES (" \ 0 200 400 600 800 I

Fig. 1- Natural distribution of Pinus ponderosa P. Lawson et Lawson and Pinusje.ffreyi Grev. et Balf. (based on Critchfield and Little, 1966, but following Read, 1980, regarding the southern limit of P. ponderosa in Arizona and New Mexico). 4

Two well-defined varieties are recognised; P. ponderosa var. ponderosa and P. ponderosa var. scopulorum.

1. Pinus ponderosa var. ponderosa (the common variety, Figures 2,3 and 4). The following racial subdivisions are generally recognised within this variety: (a) The 'Pacific', or 'Califomian' race: Occurring from southem California through the Sierra Nevada and Coast Ranges to about the crest of the Cascades, at least as far north as southem Washington. Distinguished by vivid green foliage, generally dense crowns and a sturdy appearance. Overall, this race contains the fastest growing trees. (b 'North Plateau' race: Occurring from east of the crest of the Cascades, northwards into British Columbia and eastwards into westem Montana. Distinguished from the Pacific race by its greyer foliage, shorter needles, lighter branches, less dense crowns and generally purplish immature cones. It tends to have more slender stems than the Pacific race, although it may show relatively greater butt taper. It is also more drought tolerant than the Californian race.

East of the crest of the Cascades in southem Oregon and the extreme north of Califomia there is an apparent transition zone between the two races of P. ponderosa var. ponderosa.

2. Pinus ponderosa var. scopulorum (the Rocky Mountain variety, Fig. 5). Centred in the Rocky Mountains, this variety occupies an area extending from central Montana in the north, to eastem Nevada in the west, Arizona, New Mexico and westem Texas in the south, and central Kansas in the east. It generally has sparse crowns, and short, tightly tufted foliage, with needles often in twos. This variety includes several different races, all of which are slow growing .

So-called 'P. washoensis' almost certainly belongs within the species P. ponderosa. It is found at high altitudes, mainly in the northeastem Sierra Nevada, with scattered occur­ rences further north.

Pinusjejfreyi contains at least two races (see Fig. 12). (a) The 'Sierra Nevada' race: Occurring mainly in the Sierra Nevada ranges, extending southwards at least to latitude 34° N; and concentrated at high altitudes. The crowns are often sparse and the race is distinguished by dark greyish and slightly tufted foliage. The butt tends to show little taper near the ground and the bark is dark grey and finely fissured.

(b) The 'Coast Range' race: Occurring in the Coast Ranges north of San Francisco on serpentine soils and often at low altitudes. The race can be distinguished by markedly paler greyish-green foliage, and the tendency of needles to be longer, with a more pronounced 'chimney brush' set. In this race the butt tends to taper more in young trees and the bark tends to be paler with relatively prominent vertical fissuring. This race of P.jejfreyi appears to hybridise readily with P. ponderosa.

Both these races have long been present in New Zealand.

New Zealand Provenance Trials

Differences between seedlots of P. ponderosa were noted very early, and the first provenance trial to be fully recorded was planted in 1929, when 13 provenances covering the main geographic forms within P. ponderosa were established in Kaingaroa Forest. In this trial the fastest growing provenances were those of the Pacific race from low altitudes in California, while provenances of var. scopulorum were the slowest. 5

Fig. 2-Pinus ponderosa aged 5 years, showing Fig. 3 - Pinus ponderosa showing contrast in sturdy fonn and characteristic set of foliage. habit between races. Pacific race (left) and North Plateau race (right).

Fig. 4-Pinus ponderosa at Hanmer forest, Canterbury, showing typical straight stems and narrow spire-like crowns. 6

Fig. 5 - Pinus ponderosa var. scopulorum.

Later, in 1960-61, a series of provenance trials was established at 17 sites throughout the country. However, none of the South Island sites were above 500m altitude. In all, the trials involved 55 provenances from the western half of the range of P. ponderosa (but almost entirely from Lat. 37° northwards) and seven provenances of P.jeifreyL The trials were assessed for survival and height at all sites in 1967, 6--7 years after planting. Although provenance rankings for height differed among sites, two provenances of the Pacific race of P. ponderosa (from south-west Oregon at altitudes of about 300 m) outgrew most of the others at the majority of sites. It was also confirmed that North Plateau provenances were well adapted to

Fig. 6-Pinus ponderosa Oeft) and Fig. 7 - Pinus ponderosa Oeft) and P. jeffreyi (Sierra Nevada race) P. jeffreyi (right), Tara Hills Pro­ (right) in Hanmer Provenance Trial (trees aged 25 years). Pinus venance trial. Note greyer green jeffreyi shows slower growth, more cylindrical butt form and greyer foliage and slower growth of P. bark with finer fissuring. jeffreyi. 7 sites having a semi-continental type of climate (dry summers/cold winters) characteristic of much of the central South Island. At many of the sites, growth of trees in the P. ponderosa trials over the next few years was poor compared with that of other species, and serious infection by Dothistroma needle blight (assessed at two North Island sites in 1973 and 1974 respectively) was a prominent feature. By 1974, trials throughout the North Island and the warmer, moister parts of the South Island had accordingly been abandoned leaving only those at Hanmer (in North Canterbury), Tara Hills (in the Mackenzie Basin), and Earnscleugh (in Central Otago). plus a collection at the FRI arboretum at Rotorua. In 1976 the Tara Hills trial was assessed for height and diameter. Then, in 1984, all three remaining trials were assessed for height, tree form and wood properties, and the Rotorua collection was assessed for height and diameter.

The results of these later assessments confirmed the generally good growth rates of the Pacific group of provenances (Table 1). This was most evident at the moist sites, Hanmer and Rotorua, where the low-altitude/low-latitude provenances made faster height growth

Table 1- Comparative growth of P. ponderosa and P. je.[freyi provenances at age 22-24 years

Species /race Hanmer Tara Hills Rotorua (500m asl (300m asl (300m asl annual precipitation annual precipitation annual precipitation approx. 1200 mm) approx. 400 mm) approx. 1450 mm)

Height (m) Mean (Range) No. of Mean (Range) No. of Mean (Range) No. of provenances provenances provenances P. ponderosa North Plateau 13.2 (12.2-14.6) 18 10.3 (9.6-11.3) 7 10.8 (8.6-13.1) 5 (and transition) Pacific 14.8 (12.8-16.8) 27 9.8 (8.7-10.8) 27 14.4 (11.5-17.3) 21 N.Z. control (Naseby) 14.4 1 9.6 1 (Queens town) 16.0 1

P. je.[freyi Coast Range 14.0 1 9.2 1 9.7 1 Sierra Nevada 10.5 (10.4-10.6) 3 8.4 (8.2-8.7) 3 4.7 (4.1-5.9) 3

Diameter (mm) Mean (Range) Mean (Range) Mean (Range)

P. ponderosa North Plateau 254 (228-288) 211 (197-229) 157 (111-188) (and transition) Pacific 316 (275-351) 237 (218-263) 278 (170-356) N.Z. Control (Naseby) 293 257 (Queens town) 346

P. je.tfreyi Coast Range 237 187 143 Sierra Nevada 218 (204-230) 221 (21~223) 92 (76-106) 8

than the high-altitude, high-latitude provenances. In addition, the Pacific provenances tended to have greater diameters for a given height, and hence greater individual-tree volumes.

Also confirmed was the early promise of the Northern Plateau provenances at the dry, semi-continental Tara Hills site. Not only had they shown much better initial survival there than the Pacific race, but they also averaged about 5% taller. Material assigned to P. washoensts was too slow growing to be of interest.

The P. je.ffreyl seedlots were always amongst the slowest growing, although they fared relatively better at Tara Hills than elsewhere (Figures 6 and 7).

Wood density in P. ponderosa varied among the provenances but tended to be slightly higher in North Plateau material than in the Pacific race. Pinus je.ffreyi showed slightly higher density than the Pacific race of P. ponderosa..

Pests and Diseases

Both species, but especially P. ponderosa, are highly susceptible to Dothistroma needle blight. Neither species shows adult resistance. This effectively precludes their use over a wide range of New Zealand sites. Unfortunately, the most susceptible group of provenances (the Pacific race of P. ponderosa) includes those that are the most productive. However, within the Pacific race, provenances from the Coast Ranges are the least affected and these do include some of the fastest growing. Provenances of the North Plateau race are generally less severely attacked than those of the Pacific race, and generally P.je.ffreyi is less affected than P. ponderosa by Dothtstroma. Trees attacked by Dothtstroma also become susceptible to attack by the root-rot fungi, Annillaria spp. Diplodia ptnea, a fungus associated with die­ back of leaders and laterals (Fig 8), can cause significant malformation in P. ponderosa, often showing up after drought on shallow or gravelly soils. Paradoxically, it is probably triggered by warm humid weather. Spec­ tacular dieback can occur when Diplodia attacks wounds caused by hailstorms. When dieback occurs, faster-growing provenances of P. ponderosa tend to be more severely affected than slower growing ones. Pinus je.ffreyl appears to show much less dieback than P. ponderosa.

In the past, the main insect damage recorded was mortality from attack by the wood wasp Sirex noctilio, but this was usually confined to older, very crowded stands.

Various other fungal pathogens and insect pests have occurred periodically but are generally unimportant.

While young, Pinus ponderosa is very palatable to browsing animals such as Fig. 8 - Pinus ponderosa showing dieback due to rabbits, deer and goats, so good animal con­ attack by Diplodia. trol is needed for establishment. Possums 9 may chew and strip bark in the crowns, and rtngbarking can lead to death of leaders. Severe damage to P. ponderosa stands by possums has been reported in the past in Canterbury.

Pirl.Us je.ffreyi is not known to be specifically prone to any pests or diseases. It looks more thrifty, however, when growing on semi-continental sites.

Although vulnerable to crown fires, P. ponderosa and P.je.ffreyi. especially older stands, are generally more resistant to ground fires than many other pines,

RECOGNITION

Pinus ponderosa P. Laws on et Laws on - ponderosa pine Habit: A tall tree, growing up to 55 m high in New Zealand, and up to at least 70 m in its native habitat; with breast height diameters up to 160 cm in New Zealand, sometimes much larger in native stands. When young it is narrow and conic. Although the shape becomes more variable with age, it usually retains a distinctive spire-like habit, with a narrow crown and straight upright stem (Fig. 9), until very old. The crown may vary considerably in density and colour but the 'chimney-brush' set of the foliage, which is often densely tufted near the ends of the branchlets, is usually distinctive (Figures 3, 14). Old, open-grown trees often have a few big lower branches which give them an irregular crown. Severe exposure may make the crown asymmetric but usually without causing much lean or stem sweep. Until the trees are quite old (around 25-30 m tall) the lower bole generally has a pronounced taper, but older trees develop cylindrical butts.

Bark: At first pale purplish grey, later becoming reddish or brownish grey. The bark is thick in quite small trees, with diffuse, fairly finely grained fissures and irregular flakes. As trees get older the pattern of fissuring becomes simpler and the bark becomes very distinctive in appearance with thick, large, smooth somewhat rectangular plates, reddish brown or reddish pink to orange-yellow in colour

Foliage: Needles (Fig. 16) usually occur in groups of three (sometimes in twos or fives). They are usually 10-25 cm (occasionally to 36 cm) long, 1-2 mm wide, varying considerably in length and width according to race. Colour ranges from light vivid green to yellowish green or fairly dark greyish green, again depending mainly on race. Needles are more or less crowded on the shoot, usually spreading but sometimes pointing forwards, more or less rigid, and sharply pointed at the tip. Leaf sheaths are yellowish or reddish brown at first, later becoming very dark coloured; persistent, c. 2-3.5 cm long at first, becoming very much shorter. Needles persist for 3 or 4 years.

Branchlets: Green or yellowish brown at first, becoming dark shining brown; thick; covered with conspicuous leaf bases.

Winter buds: Cylindric to conic, pointed, usually reddish brown, slightly to very resinous (Fig. 17). resin more evident in younger trees. Scales partly free, especially near base, or all closely pressed, fringed with dark-coloured hairs.

Cones: Solitary or in clusters of usually 3-5 near the ends of branches, without stalks or with very short stalks, ovoid to sub-cylindrical, usually 8-14 cm long (occasionally 6-18 cm long), 3.5-5 cm wide when closed, more or less symmetrical, slightly curved (Fig. 21). Colour of young unripe cones varies from green through reddish to deep purple depending mainly on origin (Fig. 20). generally green in California, and in the Rocky Mountains and purple in the North Plateau race but intermediate in western Oregon; light reddish brown when 10 mature, weathering to grey-brown. Scales often much darker in colour on the lower surface. Exposed part of the scale transversely ridged, each scale with a sharp, usually outward pointing prickle (Fig. 23) making cones unpleasant to handle without gloves. Relatively soft and light when dry. Opening and shedding seed in late summer to autumn (Februa:ry-March in New Zealand), generally falling in the next 4 months, often leaving a few basal scales attached to the branch resulting in a hollow at the base of the shed cone (Fig. 22).

Seed: Oval, 6-9 mm long, 5-6 mm broad, usually reddish or blackish brown, often mottled, wing usually 1. 5-3 cm long, pale with darker transverse lines (striations) (Fig. 24).

Pinusje.ffreyi Grev. et Balf.- Jeffrey pine Habit: A tall tree up to 40 m high in New Zealand, but reaching at least 60 m in its native habitat; breast height diameters up to 150 cm in New Zealand, but often greater in natural stands. In general habit it is very similar toP. ponderosa with a straight trunk and narrow, often spire-like crown (Fig. 10). Trees of Sierra Nevada origin tend to have sparser crowns with slightly more tufted foliage and a more cylindrical butt than those from the Coast Ranges.

Bark: In young trees smooth and pale grey, easily differentiated from the brownish, roughish bark of young P. ponderosa. In older trees varying markedly according to origin (Fig. 12). In trees of Coast Range origin it closely resembles P. ponderosa, being brownish grey to red­ brown, fissured and irregularly flaked. In the Sierra Nevada race it is darker grey, rough, and has a much finer pattern of fissuring (Fig. 7).

Foliage: Needles usually in groups of three (sometimes two to five) 11-26 cm long, 1.5-2.2 mm wide, usually bluish to greyish green, straight, stiff but flexible (Fig. 16), sometimes twisted, with a tufted arrangement on the ends of the branchlets (Fig. 15). Basal sheath persistent, dark grey-brown.

Branchlets: Stout, greyish at first, usually with a bluish white (glaucous) bloom in the first year or two, (Fig. 19) becoming grey-brown.

Winter buds: Cylindric, yellowish to reddish brown (Fig. 18), non-resinous (in contrast to P. ponderosa which has resinous buds) or occasionally slightly resinous, scales closely pressed at the bud tips, often free in the middle, fringed with whitish hairs.

Cones: Short-stalked or nearly stalkless, almost symmetrical to slightly asymmetrical, conical­ ovoid to sub-cylindrical, 13-30 cm long, 8-18 cm wide when mature (Fig. 21), dark purplish brown in the first year, becoming pale brown when mature. Scales transversely ridged, each with a small sharp spine, usually reflexed (Fig. 23). thus the cone is not prickly to handle. Opening and shedding seed as soon as fully ripe, generally falling during the next few months. Cones relatively soft and light when dry. As with P. ponderosa, when cones are shed or picked a few scales often remain on the branch leaving a hollow in the cone base.

Seeds: Ovoid, 10-15 mm long, 7-8 mm wide, wing up to 3 cm long (Fig. 25).

Distinguishing features: Features distinguishing P.jeifreyt and P. ponderosa are summarised in Table 2. Cones, where present, usually afford the clearest distinction; being generally smaller and prickly to handle in P. ponderosa, and much less or not at all prickly in P. jeifreyL Otherwise, resinous buds in P. ponderosa and non-resinous buds in P. jeifreyi are usually diagnostic. In young trees the colour of twigs, greyish to whitish in P. jeifreyi and brownish in P. ponderosa, is a valuable clue, particularly at times of the year when winter 11 buds are not formed. A distinction also exists in the colour of the surfaces freshly exposed by flaking of bark. In P. ponderosa it is a palish yellow, and in P.jeffreyt, a rich, reddish pink (Fig. 13). Chemical analysis of turpentine is conclusive.

TABLE 2 - Summary of differences between P. ponderosa and P. je.ffreyi P. ponderosa P.jeffreyi

Leaves Variable, but often quite Tending to be grey-green vivid green Bark Brownish and roughish Smooth and pale grey in young trees in young trees Branchlets Green or yellow-brown in first Whitish bloom in first 2 years. 2 years. Winter resting buds Resinous Non-resinous Female cones Smaller (6-18 cm long) with Larger (13-30 cm long) with sharp prickles usually many more scales, prickles pointing outwards, usually pointing backwards, prickly to handle not prickly to handle. Seeds 6-9mmlong 10-15 mm long Turpentine Mixed monoterpenes n-heptane

These two species can generally be distinguished from other pines by the combination of narrow regular crowns, sparse tufted foliage set near branchlet ends and deciduous cones.

ROLE OF THE SPECIES

Present Extent Currently, ponderosa pine occupies over 5000 ha in New Zealand, nearly all on land previously administered by the New Zealand Forest Service. As at 1st April 1990, the NZ Forestry Corporation owned a total of 4880 ha of P. ponderosa, some of which had been underplanted with Douglas fir. Of that area, 3700 ha was in the North Island, the largest plantings being 1760 ha on the Kaingaroa Plateau and 1600 ha at Karioi. A further 1180 ha was scattered among the Corporation's South Island forests, principally in West Otago and Southland, but with 210 ha at Naseby. Ledgard and Belton (1985) report a further 248 ha in the Canterbury high country, excluding the Hanmer and Culverden basins. N.J. Ledgard (pers. comm.) also reports a further 30 ha of P. ponderosa in the Otago high country. Almost all these plantings are over 25 years old.

As at 1st April 1990 the NZ Forestry Corporation owned 22 ha of Jeffrey pine in pure stands, at Naseby and Rankleburn Forests.

The total area planted in P. ponderosa is likely to decrease in future as stands are clearfelled and replanted with more profitable species. About 400 ha of P. ponderosa were felled in 1989/90, mostly in the central North Island. From sales of seedlings, it is estimated that planting of P. ponderosa is currently proceeding at a rate of about 20-25 ha/ annum. (Around 30,000-40,000 seedlings are sold annually, mainly to farmers for use as shelter). 12

Fig. 9- Open-grown P. ponderosa. showing very tall Fig. 10- Old tree of P.jeffreyi (centre) straight stem maintained in an exposed situation. showing somewhat more irregular crown than is typical for the species.

Fig. 11 - Typical bark of a Fig. 12.-Pinusjeffreyi bark showing variation between races. mature tree of P. ponderosa. Note in Sierra Nevada form (left) the finer pattern of fissuring and an extreme case of its relatively cylindrical butt form. The Coast Range form (right) is more like P. ponderosa with a coarser pattern of f"lssuring and appreciable butt flare.

Fig. 13 - Freshly exposed inner surfaces of bark flakes of P. ponderosa (left- yellow) and P. jeffreyi (right-pink) showing colour contrast. Fig. 14 -Foliage of P. ponderosa. Fig. 15-Foliage of P.jeffreyi. 13

Fig. 16 - Needles of P. pon­ Fig. 17 - Winter bud of P. pon- Fig. 18-Winter bud of P.je.ffreyi. derosa (above) and P. je.ffreyi derosa. (below).

'"' ~\.. \ •.~il.i -. '1·'. / .· ... ! 1.)1~,,~(' :·/ \ : '"" 'w:;-~,.· .. /! '. \ \ "~~·· I . -;/ ' ! ~\, 1\: ~ • ':''>Li~ / ' I \ I ' \ ''l• ! ,,.I· I I ,' I I · \ \1 '\ 11 ·• ~~ I \·. ··' ~ \1 ~-· '~···• I .\ ·~' ..... , ' I I ~~\ \ \\. \\.. \• ... -.· : ~..~~· •.. ~ ..... 1~.. _;,' >i . I. / . I '~ •'\.. , . .· • I , ' ~ \' \~ t ' . f.:.J!. I / ~ • \-41 .1,1. I '\" f'~.-li-~'.... ' : ~ I \:-. \.,I .. ',,1, ·,_~). ' Fig. 19 -Young branch­ Fig. 20 - Immature cones of P. Fig. 21 - Mature cones of P. pon­ let of P.je.ffreyi showing ponderosa showing colour con­ derosa (top) and P. je.ffreyi (bottom). typical glaucous bloom. trast between races (Californian, left, and North Plateau, right).

Fig. 22 - Shed cone of P. ponderosa Ueft). Hollow in base Fig. 23 - Cone scales of P. results from scales remaining attached to branch (right). ponderosa (top) and P. Je.ffreyi (bottom). Note darker lower surface and outward pointing prickle in P. ponderosa. refl.exed prickle in P. je.ffreyi.

Fig. 24 - Seed of Fig. 25 - Seed of P. ponderosa. P. je.ffreyi. 14

Growth and Yield

In both P. ponderosa and P.jeifreyt early height growth tends to be slow, particularly on harder sites. Later on, growth accelerates considerably and can be maintained for many years. In the fastest growing provenances of P. ponderosa at Hanmer and Rotorua, annual height increments of about 90 cm have been observed over an age range of 6-23 years, while near Wairapukao Headquarters in Kaingaroa Forest annual height increments in the fastest-growing provenances have exceeded 1 m between ages 3 and 12 years.

The growth and yield information for P. ponderosa (Table 3, p. 15) comes mainly from poorly tended stands planted at relatively moist, low- to mid-altitude sites and often with unsuitable provenances. Such stands, therefore, give a picture of P. ponderosa production which, though representative of stands currently being felled and converted to other species, is essentially historical. When clearfelled at age 50 years, typically neglected stands of Pacific-race P. ponderosa planted in State forest in the early 1900s had reached mean heights of 32-33 m and mean diameters of 33-38 cm. Total yields from these stands ranged from 600 to 700 m 3 /hectare. Overall, between ages 20 and 50 years and under the conditions stated in Table 3, P. ponderosa generally fell behind P. radiata by about 50% in height, 40% in diameter, 60% in basal area and 75% in volume per hectare.

It is still not quite clear whether growth rates of P. ponderosa will be sustained in the higher altitudes of the central South Island, but indications are that conditions for growth may be more favourable than in the North Island. Volume production of P. ponderosa stands in central Canterbury, at altitudes ranging from 450-750 m a.s.l. has been analysed in some detail by N.J. Ledgard and M.C. Belton. Mean annual increment (m.a.i.) tended to peak at around age 45-50, and reached values as high as 30 m 3 /ha/year. Among the stands studied, peak m.a.i. was related far more closely to precipitation than to other site variables, the highest value being where annual precipitation exceeded 1200 mm (Fig. 26). At precipitation levels below 800 mm per year, the maximum mean annual increment (peak m .a.i.) was approximately 300Al less than for radiata pine, about equal to that of Douglas fir, 10% greater than for Corsican pine and 20% greater than for European larch. At higher levels of precipitation (800-1400 mm) similar relationships were maintained except that Douglas fir tended to produce up to 20% more in mean volume increment than ponderosa pine.

-1: 40 Gl E ...Gl 30 u 1: >...... 20 Gl --('Cl E .r: ::::J M-- E 10 0 >

0 '--.:----'---L-_.L_----"'--_J._-_J 400 800 1200 1600

Rainfall (mm/yr)

Fig. 26 - Stand productivity (peak m.a.i.) for P. ponderosa in the Canterbury high country, Fig. 27 - Inside a fine stand of P. ponderosa in relation to average annual precipitation at Raincliff Forest (tree age, 73 years; (from Ledgard and Belton, 1985). average height, 43 m; average d.b.h., 81 cm). 15

TABLE 3 - Growth and productivity in P. ponderosa and P. radiata, compared at a selection of similar State Forest sites 111

Location Species Age Stocking MIHI2) MIDIS) BA Vol (yrs) (stems/ha) (m) (cm) (m2 /ha) (m3 /ha)

Kaingaroa Forest P.pond. 23 500 6 15 4 8 P. rad. 23 550 32 41 60 581

P.pond. 40 300 25 42 32 273 P. rad. 40 300 48 70 80 1169

P.pond. 50 300 30 45 35 350 P. rad. 50 300 52 80 98 1570

Karioi Forest P.pond. 23 500 12 29 23 97 P. rad. 23 400 31 53 65 652

P.pond. 40 500 21 41 49 344 P. rad. 40 600 44 65 117 1605

P.pond. 50 450 27 47 43 334 P. rad. 50 400 50 63 91 1418

Southland P.pond. 20 1,000 11 22 26 94 P. rad. 20 1,300 24 39 81 639

P.pond. 41 300 25 46 42 338 P. rad. 41 300 40 58 62 820

P.pond. 51 550 29 48 71 684 P. rad. 51 550 49 70 103 1730

(1) Ex Permanent Sample Plot database on MOF /VAX network. (2) MTH (mean top height) =The mean height of the tallest 100 trees/hectare (3) MTD (mean top diameter) = The mean of the 100 trees of greatest diameter /hectare

Wood properties and Uses Both P. ponderosa and P.je.ffreyi produce similar pale, smooth-grained wood (Fig. 28). The sapwood is pale yellowish white, but the heartwood (which is slow to form, amounting to as little as 5% by volume at age 45 years) is often deep pinkish or red-brown (Fig. 29) and contains up to 25% resin. The basic density of P. ponderosa wood tends to be about 5- 10% lower than that of P. radiata. The most relevant comparisons come from the survey of Canterbury high country stands made by Ledgard and Belton (1985) in which breast-height wood density averaged about 350 kg/m3 for P. ponderosa and and 380 kg/m3 for P. radiata. The mechanical properties of clear P. ponderosa timber vary in step with wood density. in a similar way to those of P. radiata, so that strength properties and hardness are inherently lower than for radiata pine. The strength of sawn pieces may also be further reduced by tight clustering of knots owing to the 'uninodal' branching characteristic of ponderosa pine.

Values for basic wood properties derived from stands at a range of low- to mid-altitude State Forest sites are compared with corresponding figures for P. radiata in Table 4 ( p.17).

The low wood density of P. ponderosa and P. je.ffreyi virtually rules them out for structural uses. Neither is approved for framing timber in the New Zealand building standards. However, the softness of P. ponderosa timber is regarded as an advantage for end-uses 16 where machine nailing or stapling is employed, e.g .. in pallet manufacture. In the United States, P. ponderosa is an esteemed finishing timber, commanding high prices for clear­ cutting grades, despite low densities similar to those observed in New Zealand (densities are not critical for finishing grades or mouldings). It machines, paints and varnishes excellently.

New Zealand sawmillers have been rather reluctant in the past to accept P. ponderosa. This attitude seems to result largely from the varied nature of material coming out of stands of mixed provenance. Such stands have featured enormous differences in log size, and have contained very coarse trees with heavy branches giving rise to knot checks in the dry timber. Also, prominent nodal swellings have often made the logs difficult to gang-saw. With some young trees of North Plateau race. pronounced butt taper in otherwise slender trees caused sawing difificulties and poor conversions. These were followed by seasoning problems. In particular, longitudinal shrinkage of corewood tended to cause distortion during drying.

The sapwood of Pfnus ponderosa is slightly less permeable than that of either P. radiata or P. nigra and it is more difficult to obtain an even distribution of preservatives when treating roundwood of P. ponderosa for posts or poles. Although it dries easily it has a high green moisture content initially and is also especially prone to sapstain. Nevertheless, the round produce has gained a good reputation in the districts where it has been used.

Pinus ponderosa has been used for kraft pulping and thermomechanical pulping in New Zealand with no serious problems, although it is not favoured for purely mechanical pulping. In recent years the resource of P. ponderosa in the central North Island has largely been utilised for pulp, prior to replanting sites with P. radiata.

For both the thermomechanical and chemithermomechanical processes P. ponderosa requires a similar energy input to P. radiata slabwood to reach a given freeness. Pinus

Fig. 28 - Centre-sawn P. ponderosa aged 30 years. Fig. 29 - Pinus ponderosa disc showing Note clustering of knots and average internode characteristically small core of highly length of 87 cm. resinous heartwood. 17

TABLE 4 - Comparison of wood properties of New Zealand-grown Plnus ponderosaUl and P. radiata!2)

Species Density (kg/m3) Shrinkage to Modulus Modulus Maximum Hardness Basic Air-dry Green air dry(%} of Rupture of Elasticity Crushing (kN)!3) Volume Tangen- Radial Long!- (MP a) (GPa) (MP a) tial tudinal Green Dry Green Dry Green Dry Green Dry

P.radiata 420 500 955 7.0 4.7 2.2 0.1 40 90 5.8 9.0 16 38 2.5 4.2

P. ponderosa 400 480 980 8.3 5.1 2.8 0.3 34 71 4.4 6.9 14 33 1.4 2.1

(1) Average age 40 years from a range of State forest sites throughout New Zealand (2) Mean values typifYing 35-year-old trees (3) MPa = megapascals GPa = glgapascals kN =kilonewtons ponderosa pulps produced by either process have considerably less long fibre than their equivalent radiata pine slabwood pulps which results in lower pulp strength properties. The optical properties of P. ponderosa pulp are as good or better than those of P. radiata, P. ponderosa pulp having very good light-scattering properties.

Pinusje.ffreyi would appear to be suitable for basically the same uses asP. ponderosa.

For shelterbelts, both species have the advantages of hardiness, drought tolerance, narrow crowns, and good resistance to exposure. For amenity planting, the narrow sym­ metrical crowns, straight stems and the large size to which P. ponderosa in particular can grow (Fig. 27), are very attractive features. Characteristically P. ponderosa and P. je.ffreyi continue to remain straight and do not readily lose their symmetry, even when subjected to strong prevailing winds (see Fig. 9). However, P. ponderosa shelterbelts can develop a wider spread than P. nigra shelterbelts of comparable age (N.J. Ledgard pers. comm.).

Regeneration

While P. ponderosa spreads to some extent by natural regeneration, it does so less aggressively than P. nigra, P. contorta, P. sylvestris, P. pinaster, Larix spp., or occasionally, Pseudotsuga menziesii. and long-distance colonisation seems to be rare. Pinusje.ffreyi appears to spread even less readily, very likely because of its much heavier seed. Both species are highly palatable to browsing animals which may restrict spreading. They also tend to be late seeders, especially in moist climates-see Seed Users Guide, (A), p. 21.

Siting

Since the 1960s the acute susceptibility of P. ponderosa and P. je.ffreyi to Dothistroma needle blight has imposed considerable restrictions on where they can be grown. At one time they could be sited throughout most of New Zealand, being used on the colder sites and poorer soils above 600 m in the North Island and 350 m in the South Island. The best remaining sites for these species today are the relatively dry Dothistroma-free uplands of the central South Island, which experience a characteristically semi-continental type of climate. Despite its capacity for drought resistance, P. ponderosa is not recommended for thin draughty soils; yields tend to be low, and leader dieback, which may give rise to considerable malformation, is likely to occur. On the other hand, very moist soils can be tolerated, provided that they are well aerated and reasonably fertile. Both species stand up well to 18 exposure, suffering little damage from wind or snow. In New Zealand they appear to thrive to at least 800 m and in some situations to 1000 m.

Silviculture

It is perhaps surprising, in view of the extensive and sustained use of the species for afforestation in the past, that formal silvicultural schedules have not been evolved for P. ponderosa in New Zealand. Silviculturally, P. ponderosa has generally been treated in one of two ways. Many slow-growing stands have been thinned, manually or by poisoning, before being interplanted with more productive species such as Douglas fir or radiata pine. However, the majority of stands have been left unthinned (Fig. 30) or have been lightly and tardily thinned to waste, in which condition most still await clearfelling.

Pinus ponderosa is a strongly light-demanding species in which the crowns of neighbouring trees never quite touch. Extreme crowding can significantly reduce height growth. The silviculture of P. ponderosa as a pure crop poses some conundrums. On the one hand, large diameters are needed to give commercially valuable logs. On the other hand, there are problems obtaining such diameters within a reasonable time. The heavy thinnings required would severely compromise mean annual increments and give intermediate wood yields of low value. Moreover, pruning to 3-5 m, which would seem highly desirable to avoid poor timber grades in the lower stem, would be an investment which could only be recouped if subsequent dia­ meter growth was fairly rapid.

Suggestions for future silvicultural programmes probably should anticipate a role for P. ponderosa as a species largely confined to high-country wood­ lots or associated shelter plantings. Minimal tending would be a desirable feature of treatment schedules (see Table 5) in such areas.

The use of P. ponderosa in mixture with other species, such as Corsican pine (P. nigra ssp. laricio) is a possibility still to be explored in high country forestry. In this mixture, P. nigra would be planted to provide a yield in the intermediate term and as a companion species for the slower-maturing, but ultimately larger P. ponderosa, which would predominate in the final crop (Table 6). Alternatively, P. ponderosa could have an agroforestry role, with trees grown at parkland stockings in high country pastures (Fig. 31). In central South Island high country it has been recently found that pines can significantly replenish the upper soil layers with available phosphorus in areas where depletion of phosphorus Fig. 30- Interior of typical unthinned P. ponderosa likely to limit pasture growth. stand aged 39 years, 1 19

TABLE 5 - Suggested minimum tending sawlog regime for P. ponderosa for hill- and high-country woodlots (based on recommendation by N.J. Ledgard)

Year Mean tree height (m) Operation and remarks

1 Planting; 4 x 2 m; (1250 stems/ha) 1 Weed control 12 6-8 Thinning to 400 sph ~ posts 12 Pruning, to 3 m, optional (visibility and access) 25 Pruning, to 6 m, optional 50 (rainfall > 1000 mm) 26-30 Clearfell ~ sawlogs 60 (rainfall > 1000 mm) 24-26 Clearfell ~ sawlogs

Fig. 31- Fifteen year-old P. ponderosa stand planted at 900m, central Canterbury on an eroding site. Undersown lotus is thriving, presumably due to shelter and remobilisation of phosphorus from deeper soil layers. 20

TABLE 6 - Suggested management regime for P. ponderosa/P. nigra mixture (2000 stems/ha; 500 P. ponderosa, 1500 P. nigra planted at 2 x 2.5 m spacing in 1 row: 3 rows mixture)

Approx. tree ht Pruning Thinning (m) (P. ponderosa only)

6 350 to 1.5 m 8 350 to 2.5 m 10 270 to 3.7 m to 300 P. ponderosa and 700 P. nigra 13 250 to 5.0 m 17 to 250 P. ponderosa and 300 P. nigra 25 to 200 P. ponderosa

The Future Role of the Species

As a result of siting restrictions necessitated by susceptibility to Dothistroma infection the future role in New Zealand of P. ponderosa is more limited than was once visualised.

The areas within which the species may now be grown include some which receive low precipitation (less than 600 mm annually). Good survival can be expected on these difficult sites provided that competing grass can be completely controlled for the first year or two. Where feasible, some irrigation in the first year may also prove helpful. Future research may confirm provenances of the North Plateau race of P. ponderosa as the most appropriate choice for at least some of these sites. However, in the immediate future, it is probably better to rely on P. ponderosa provenances of the Pacific race. Despite its good form, P. je.ffreyi is too slow growing to have a potential role as a timber species in its own right. Although P. ponderosa is faster growing than P. je.ffreyi, a future role for it purely as a timber species is almost equally hard to justify. As a short-rotation pulpwood crop it would appear to be inferior to P. contorta, while if grown on long rotations, problems arise in respect of the poor log form and unattractive timber properties of thinnings. Low wood density would appear to rule out any demanding structural uses for the timber. Although P. ponderosa can conceivably produce internodes long enough to be attractive for clearcuttings, pruning, particularly of the first three metres of the butt log, would be needed. It is also possible that internodes will become shorter, and hence less attractive, at higher altitudes where precipitation (rain and snow), is greater. In any case, where precipitation exceeds 800 mm, Douglas fir, which has attractive timber properties, becomes markedly more productive than P. ponderosa, although it is more vulnerable to exposure and out-of-season frosts. It should also be remembered that the limits of P. radiata have undergone favourable revision on dry central South Island sites; much damage once thought to be due to frost is now attributed to boron deficiency, which can be easily corrected.

On the driest and frostiest sites the hybrid between P. attenuata and P. radiata may be preferable for its rapid early growth, but yields would inevitably be modest.

The most promising role for P. ponderosa and P. je.ffreyi may be as shelter species in the high country, for which their ultimate large dimensions, and their qualities of hardiness, windfirmness, resistance to snow damage and retention of good stem and crown form under exposure are advantageous. Low pruning is an option that could enhance wood quality of the resulting timber resource. The possible future role of P. ponderosa in pure plantations, for timber production alone, may not be so attractive economically, while management of mixtures, say with Corsican pine, would require experience. skill and attention to detail. 21

SEED SOURCE A young seed stand was planted in 1979 in Naseby Forest, using seed from Grant's Pass, Oregon. Seed of this origin gave the best all-round performance in the provenance trials that were planted in 1960-61. This stand should become the preferred seed source for P. ponderosa in New Zealand. Other sources of P. ponderosa seed are imports from low altitudes in the Oregon coast ranges, and seedlots from well-formed stands of Pacific race in the central South Island, or from the Tara Hills provenance trial. The latter produces P. ponderosa seed of a range of about 20 provenances among which both Pacific and North Plateau races are represented. It is recommended that seed collections from these be segregated according to race. It is suspected that little crossing actually occurs between the races. Pinusjeifreyi seed is also available from this trial (see Seed Users' Guide - C). Seed of P. ponderosa and P.jejfreyi is available through Proseed New Zealand Ltd. Private Bag 3020, Rotorua.

On account of their susceptibility to Dothistroma needle blight ponderosa pine and Jejfrey pine are clearly species suitable only for parts ofthe.central South Island having a semi-continental climate. The slow growth of Jejfrey pine precludes its consideration as a timber species in its own right. Ponderosa pine, thoughfaster growing, has drawbacks which arisefrom its ind![ferent timber and roundwood properties and its special needs for silviculture and management as a long-rotation species. Nevertheless, both species have enduring value for shelterbelts and amenity, and ponderosa pine at least may have limitedfuture applications as a timber species in South Island high country, either in pure stands or possibly in mixture with another species, such as Corsican pine.

SEED USERS GUIDE A. Collection and extraction of seed

P. ponderosa P. je.ffreyi

Age of first coning: 8-10 years 15 years Seed available in quantity: not before 15 years 20-25 years Pollen production: Late October to early November Cone maturation period: 14-16 months -cones ripen early February to late March depending largely on provenances Periodicity of crop: Yields fairly consistent on dry sites, good seed years every 5-8 years on wetter sites Harvesting: Climbing and branch hooks Mature cone recognition: Cones turning light brown Seed extraction: 6 hrs at 40 oc (cones will open satisfactorily in sun) No. of seeds per kg: 12000-24000 5000-8000 Storage conditions: Dry store at 4 oc Stratification: 4 weeks at 3-4 oc Expected germination: 70%+ 22

B. Nursery Practice Sow in seed beds under cover in October-November. Uncover beds promptly after seed germination is complete. Plant as 2/0 wrenched stock.

C. Recommended Seed Sources Seed Source No. Locality Year Planted Area (ha) Provenance and description

P. ponderosa CY30 Tara Hills 1961-2 1.2 Twenty vigorous (Omarama) provenances including both Pacific and North Plateau races Naseby Forest 1979 40.5 Grant's Pass, Oregon (FRI Expt S550/1) Cpts 28,29 (Seedlot H0/0/77 /06)

P. je.ffreyi CY30 Tara Hills 1961-2 0.18 Provenances 685, 686, (Omarama) 689 ('Sierra Nevada' race)

REFERENCES AND FURTHER READING

BAUMGARfNER, D.M.; LOTAN, J.L. (Editors) 1987: "Ponderosa Pine: The Species and its Management." Proceedings of a Symposium held at Spokane,Washington, September 29-0ctober 1, 1987. Washington State University Cooperative Extension, Pullman. BURDON, RD.; LOW, C.B. (in press): Performance of Pirms ponderosa and P. jeifreyi provenances in New Zealand. Canadian Journal of Forest Research 21. COOPER, C.F. 1961: The ecology offire. Scientific American 204(4): 150-160. CRITCHFIELD, W.B. 1966: Crossability and relationships of the California closed-cone pines. United States Department ofAgriculture, Forest Service, Research Paper NC-68: 36-44. CRITCHFIELD, W.B.; LITTLE, E.L., Jr 1966: Geographic distribution of the pines of the world. United States Department ofAgriculture, Forest Service, MisceUaneous Publications 991.97 p. CROZIER, E.R.; LEDGARD, N.J., 1990. Palatability ofwilding conifers and control by simulated sheep browsing. Pp 139-143 in Bassett, C; Whitehouse, L.J., Zabkiewicz, J.A. (Eds.) "Altematives to the Chemical Control of Weeds." Proceedings of an Intemational Conference, Rotorua, N.Z. July 1989. Ministry of Forestry, FRI Bulletin 155. DALLIMORE, W.; JACKSON, AB. 1976: "A handbook of Coniferae and Ginkgoaceae." 4th Edition, revised by S.G. Harrison. Edward Arnold, London, 729 p. FOWELLS, H.A. (Compiler) 1965: Silvics of Forest Trees of the United States. USDA Forest Service, Agriculture Handbook No. 271. 23

HALLER, J.R. 1962: Variation and hybridization in ponderosa and Jeffrey pines. University of California Publications in Botany 34(2): 123-166. HARRIS, J.M.; KRIPAS, S. 1959: Notes on the physical properties of ponderosa pine, monticola pine, western red cedar, and Lawson cypress grown in New Zealand. New Zealand Forest Service, FRI, NZ Forestry Research Note No. 16. LEDGARD, N.J. 1989: Protecting hill and mountatnland soils. Forestry Forwn 4:4-5. Ministry of Forestry, Wellington. LEDGARD, N.J. 1988: The spread of introduced trees in New Zealand' s rangelands-South Island high-country experience. Tussock Grasslands and Mountainlands Institute Review 44: 1-8. LEDGARD, N.J.; BAKER, G.C. 1988: Mountainland forestry: 30 years' research in the Craigieburn Range, New Zealand. Ministry of Forestry, FRI Bulletin No. 145. LEDGARD, N.J.; BELTON, M. C. 1985: Exotic trees in Canterbury high country. New Zealand Journal ofForestry Science 15(3): 298-313. LUDLAM, A 1868: On the cultivation and acclimatisation of trees and plants. Transactions of the New Zealand Institute, Vol. 1. 23 p. MIROV, N.T. 1967: "The Genus Pinus." Ronald Press, N.Y. 602 pp. MOORE, AM. 1944: Pinus ponderosa (Douglas). Comparison of various types grown experimentally in Kaingaroa Forest. New Zealand Journal of Forestry 5: 42-49. SMITH, R.H. 1977: Monoterpenes of ponderosa pine xylem resin in western United States. U.S. Dept. ofAgriculture, Forest Service Technical BuUetin No. 1532. READ, R.A 1980: Genetic variation in seedling progeny of ponderosa pine provenances. Forest Service Monographs No. 23. WANG, C.W. 1977: Genetics of ponderosa pine. United States Department of Agriculture, Forest Service, Research Paper W0-34. 24 p. WEBB, C.J.; SYKES, W.R.; GARNOCK-JONES, P.J. 1988: "Flora of New Zealand. Volume IV Naturalised Fteridiophytes, Gymnosperms, Dicotyledons." DSIR Botany Division, Christchurch. 1365 p. WELLS, 0.0. 1964: Geographic variation in ponderosa pine. I. The ecotypes and their distribution. Silvae Genetica 13: 89-103. WESTON. G .C. 1957: Exotic Forest Trees in New Zealand. New Zealand Forest Service, Bulletin No. 13.

ACKNOWLEDGEMENTS

The authors are grateful to N.J. Ledgard for information, and together with C.G.R. Chavasse, Dr. U. Benecke, C.E. Ecroyd and R.L. Knowles for helpful comments on the draft, and to Lesley Whitehouse for editorial assistance. Photographs were taken by J.H. Barran (Figures 7, 11 and 12), D. Blake (Figures 13-25, and 28), J. Johns (Frontispiece, Figures 9, 27, and 29). N. Ledgard (Figures 2, 3, 6 and 8), C.E. Ecroyd (Figures 5 and 10), H.G. Hemming (Figure 31), and D. Kershaw (Figure 4).