Establishment of Douglas fir plantations on bare ground.

Brian Swale, B.Sc. (NZ), M.A. (Forestry) (Oxon.)

What this page is about.

Mycorrhizae, or mycorrhizal roots, are important for the good health and growth of Douglas fir (D. fir) or Pseudostuga menziesii. The fungal genera which as ectomycorrhiza form good associations with D. fir include Rhizopogon, Endogone, Tuber and Hebeloma. Good forest tree nursery practice will ensure that Douglas fir seedling roots are infected with the mycorrhizal fungus that gives the best growth in the forest situation, and that nursery practice including wrenching or root pruning (seedling conditioning), seed spacing, seedling lifting, root trimming and seedling transport are all designed to ensure excellent seedling condition. On the planting site, cool-temperature seedling storage, avoidance of delay in planting, and quality planting technique allied with good site preparation will complete a quality process. Seed provenences for New Zealand sites will mostly be from coastal stands in Oregon and from California (Fort Bragg and Korbel); NZ seed stands are at Ashley and Eyrewell Forests and in the Nelson region.


This page began with the intention of making available some little-known facts and techniques in regard to the importance, selection and use of mycorrhizal fungi in getting plantations of Douglas fir off to a good start. I soon realised however that there were a host of other factors that should be mentioned as well, since ignoring them might be even more damaging to the future of a stand of trees than ignoring mycorrhiza. So I have included much other material as well.

This material and experience were gathered during 32 years' experience, mostly as a practicing graduate forester in the New Zealand Forest Service prior to its' dismemberment by the Labour Government in 1986. By 1986 the NZFS was well up a slope of increasing excellence in all sorts of ways relating to the establishment and management of productive plantations of exotic trees. Since then things have changed dramatically.

Some readers may say that they know all that follows.  That's fine, but not everybody who wants to grow D. fir does.

The conventional wisdom has not served forestry well in a number of situations; what people might perceive to be the commonsense solution is not necessarily the best solution to the challenge of getting a crop off to a good start. This applies especially to nursery practice and planting, where the practices followed have often been designed to suit the convenience of administration (seedling handling, transport and storage), or to follow the custom of practices or habits that have endured for decades (detailed planting practice), and so on. What I write below is intended to achieve the best result for the trees regardless of what the people concerned have to endure.

This web-page is being re-loaded as each bit more is added; it's under construction!

Index.

  • Seed source and provenance.*
  • Sowing and nursery culture.*
  • Mycorrhiza.*
  • Site preparation.*
  • Seedling lifting and preparation for lifting and planting.*
  • Planting technique.*
  • Weed control.*
  • References.*

Seed source and provenance.

It is likely that the precise source of D. fir seed to be used is important. In New Zealand, the trees are mostly of the coastal variety and have their origins along the west coast of the American continent from British Columbia to California. The progeny of all the different provenances in this wide range show wide variation in growth habits and wood properties when grown in New Zealand. In a series of provenance trials in 1957, 1959, 1971 and 1974, samples of D.fir seed were collected from very good looking coastal stands of D. Fir in Oregon and California and, along with seed from the best-performing existing seed sources already in use in this country the progeny were raised in one nursery under uniform conditions. The performance of all provenances was tested in growth trial plots located throughout New Zealand. From the information obtained about their height, diameter, stem straightness, and wood density, decisions were able to be made as to the best progenies for local use.

The 'best' provenances were all from low elevations, close to the coast in the fog-belt localities in northern California and southern Oregon.

Four sources of superior seed were identified (quoting from R. N. James, 1985):

  1. The "Fort Bragg" strain - of Californian ancestry, has qualities of exceptional vigour and flushes comparatively early. Seed stands now exist in Rotoehu and Golden Downs forests. (Korbel D. fir - near Fort Bragg, is also very good on sites without excessive spring wind).
  2. The "Ashley" strain. Exhibits characteristics of coastal Oregon provenances. Has intermediate flushing and is the best 'all-round' prospect for most sites. Seed stands in Ashley, Eyrewell, and Golden Downs Forests.
  3. The "Beaumont" strain. A late flushing strain suitable for planting in Southland.
  4. The "Kaingaroa" strain. The predominant type in New Zealand plantings (because Kaingaroa has so much D. fir). A dependable late-flushing strain giving maximum protection against late frosts (which Kaingaroa Forest always has many of). Growth rate leaves much to be desired, so breeding programmes incorporating this provenance have been discontinued.
None of these four commercial strains are resistant to Phaeocryptopus gaumanii needle-cast.

It was interesting that one of the best-performing seed stands was one that had already been in use for many years, Compartment 12 in Ashley Forest in Canterbury. As a result, a large seed stand of that source was established in 1982 in Eyrewell Forest; the Compartment 12 trees having become rather too tall to easily collect from.

To index.

Sowing and nursery culture.

I will not at this juncture give in precise detail all the practices I know because the soil types, climate, pathogens present , weed profile and so on are all different between forest nurseries. However, some matters of principle and practice may be applied with confidence over many sites, so are worth mentioning.

Seed must be stratified properly, and coated with an anti-fungicide to deal with damping-off fungi (unless you are going to innoculate the seed with mycorrhizal spores).
If you do not have local practice to guide you, then use the information given in Fowells and in Schopmeyer (see refs).

The mycorrhizal history of the nursery is important, and unless you know that the intended nursery soil already has the best forest (as distinct from 'nursery') mycorrhizal fungus present, you should find out what species is needed, where and how to get it the previous autumn, and be ready to apply it. For this, you probably need to plan ahea
d.

From field trials, you should be able to specify target seedling dimensions for planting stock. Published papers may give guidance. Depending on the size of weed expected to be encountered in the first year after planting, we aimed at a height of 35 - 70 cm and a root-collar diameter of around 8 - 12 mm.

Decide on the best age stock to use (2/0 = two years old, with no transplanting) In some places, seedlings are still routinely being transplanted, to produce 1/1, 2/1, or 2/2 stock. Transplanting is not only very expensive, but damages the root systems. Through precision sowing (see below), seedling transplanting can be avoided, and the seedlings will be better formed as a result.

The optimum depth of seed sowing to achieve excellent germination and survival must be worked out. We used 2 - 6 mm.

The optimum seedling spacing to achieve the target seedling height and diameter must be worked out. Every seedling must therefore have the optimum best spacing in the ground if it is to achieve its' size potential. To operate on the principle of 'average seedling spacing' is faulty reasoning, since too many of the seedlings will be spaced too closely; each seedling must have a guaranteed minimum spacing, and the more precise the spacing is, the more uniform the sizes of the seedlings will be at lifting and the better the young forest crop will be.

Optimum spacings developed in New Zealand are; rows of seedlings per bed 6 or 7; spacing between rows 15cm, (10 cm was possibly best but is impracticable, 12.5 cm might be best of all, but 15 cm was closest while still accommodating existing machinery) seed spacing within the row 7 -8 cm, depth 2 - 6 mm.

We developed a precision suction-roller seed sower that guarantees precise spacing for every seed. It is important to achieve uniform best seedling dimensions as an essential step to get good, uniformly excellent plantations, and it can be done. However, these machines are very expensive (1986 NZ dollar price about $20,000) and you would need to look at the economics pretty closely. They were invented in New Zealand specifically for tree seed sowing, and I am unaware of their being made anywhere else. There are alternatives that come reasonably close however; the Stanhay precision belt sowers do a reasonably good job for a lower cost. However, a major caution with respect to the Stanhay machines is that they must be very well maintained if they are to yield the better results thay their use can give. A poorly-maintained Stanhay does not give good results and in one season can cost the price of a new Stanhay through failed crop and consequent lost sales.

Decide on the best seed cover. We used a specific coarse grade of round greywacke grit; diameter about 5 mm.

Weed control in Douglas fir seedling beds at the stage of about two to three months after sowing is often a critical event; hand weeding is very expensive and causes many seedlings to be lost. We found that, surprisingly, low rates of atrazine, applied after sowing, gave very good control on a medium silt loam. I say surprisingly, because we found D. fir to be very sensitive to propazine and simazine, and expected atrazine to give a similar response. The specific treatment is atrazine 400 gm active ingredient per gross nursery hectare, sprayed immediately after sowing and grit covering, and followed up with irrigation on the same day.

Seedling 'conditioning' is an important process. We find that seedlings can not be grown large enough in one growing season for planting out, so must go to a second season, and then it is too easy for excessive height growth to occur. As for radiata pine, we no longer 'top' seedlings with a mower or such, but use a root trimmer which we call a wrencher. These days we use reciprocating wrenchers which sever the roots very cleanly, and encourage the development of a compact bushy root system with a high proportion of mycorrhizal roots. The result of the use of these machines is that there is reduced shock at lifting since less of the root system is removed (trimming is still needed to yield a root system for presentation to planters so that the seedlings will be planted well), and excessive height growth can be curtailed usually. Lateral root trimming with rolling-coulter front-mounted machines purpose- designed helps keep root systems more compact and results in greatly reduced damage to lateral roots at seedling lifting.

From J. C. van Dorsser 1981 (in Chavasse, 1981) are these findings on the effect of wrenching:

Conditioning by undercutting and wrenching causes physical and physiological changes in seedlings. Most of these changes have been found to be beneficial.

In radiata pine and Douglas fir the desirable changes were:

  1.   a significant reduction in height growth and diameter growth
  2.   a significant increase in the dry weight of the fibrous roots, especially the finer tertiary roots
  3.   a significant increase in the root/shoot dry weight ratio (because of the reduced root size)
  4.   a higher proportion of carbohydrates in the root system
  5.   a higher root growth potential after planting out under conditions of stress
  6.   in Douglas fir, a significantly more negative osmotic component of water potential both at full and zero turgor by between 0.2 and 0.3 MPa. This allows maintenance of a higher turgor pressure for a given water potential.
The undesirable changes were:
  1.   a lowering in the foliar nutrient content of N, P and K, particularly N
  2.   a lowering in the chlorophyll content of the foliage, causing a yellowing appearance
  3.   poor taproot development after planting in some cases, although this has not been quantified (comment - this was sorted out in later years through the understanding of the benefits of making a sharp clean cut at lifting/sorting/packing time so that a good callus forms from which root will regenerate).

To index.

Mycorrhiza.

At some stage in mid-1998 somebody asked in the alt.forestry newsgroup about mycorrhiza and D. fir. At that time I did not respond, but later realised that I do have something to contribute.

What got me going in this region of endeavour was the remark made to me in the mid-1970's (when I was responsible for the Kaingaroa Forest Nursery which produced about 20 million seedlings annually) by Jim Woodman then of Weyerheuser Forestry Research, that they had been given a specific research target with respect to the growth of freshly outplanted D. fir seedlings. Apparently the Company had a perceived problem of seedlings stagnating for a few years just after planting.

He said that they were given the goal of enabling seedlings to reach 4 feet height within 4 years of planting, and were given 4 years to achieve that. What they found was that seedlings were leaving the nursery with mycorrhizal innoculation sourced from whatever species of mycorrhizal fungus that happened to be in the nursery, and that that species usually could not survive conditions in the forest. The 'nursery' species died out in the roots and was replaced by other species; while this process was taking place, seedling growth stagnated. The researchers solved the problem by ensuring that seedlings left the nursery infected with the forest species of mycorrhizal fungus that also resulted in best tree growth.

This struck a memory chord with me since I knew that John Gilmour had found that D. fir seedlings exhibiting yellow foliage and stunted growth when planted on clay soils in Berwick forest had no mycorrhiza in/on their roots. We knew anyway that D. fir seedlings being grown in new nurseries freshly formed from agricultural land had at best patchy mycorrhizal infection, and usually too variable growth.

It was not until the early 1980's when I was responsible for Rangiora Nursery in Canterbury that I had a chance to do something about it.

Many species of fungus are capable of forming a symbiotic mycorrhizal relationship with Douglas fir. However, some species of mycorrhizal fungus enhance the growth of the trees significantly more than others do. Foresters who are responsible for establishing D.fir forests should discover what fungal species yield the best D.fir growth in their geographic area, and set about ensuring that the seedlings to be planted there have the appropriate fungus species on their roots.

Much of the scientific work; culture, identification, scientific liaison and so on was carried out by or under the direction of Dr Myra Chu-Chou, once of the NZFS Forest Research Institute at Rotorua; now retired. Her enthusiasm, expertise and willingness to be involved and help, made a huge difference to achieving a successful outcome.

What she found was that most Douglas fir seedling crops were naturally infected in nurseries by Hebeloma crustuliniforme or possibly some other Hebeloma species (but probably H. crustuliniforme).

In D. fir South Island forest stands of all ages she found Tuber sp, Endogone sp, Boletus sp., Hebeloma sp., and Rhizopogon parksii; most often by a wide margin, R. parksii. Central North Island stands sampled had almost only R. parksii. (NB; the species of Rhizopogon was originally thought to be R. vinicolor, but a visiting expert in Rhizopogon did a close analysis, and advised that the species was actually the one known as Rhizopogon parksii.)

We were then in a position to put into practice the information gleaned from Jim Woodman; to ensure that the D. fir seedlings in the nurseries were infected from the beginning by the mycorrhizal fungi that they would need throughout their forest life, and not by a fungal species that would die once the seedling left the nursery soil.

The next step was to find Douglas fir stands that were infected with Rhizopogon parksii, and gather sporocarps of that species.

Rhizopogon sporocarps are roughly spherical, the size of a walnut or less; 1-5 cm diameter, globose although soil pressure may make them angular, white on the outside at first, becoming pinkish, (pink when bruised) then vinaceous all over. The colour of the gleba is white to ochraceous becoming olivaceous. They occur under the leaf litter and do not push through it. The best time to find them in the South Island (NZ) forests is in mid-April to early May (autumn). However, in a moist spring they can apparently also be found, but we never looked then. We also found Endogone flammicorona with the Rhizopogon, the Endogone sporocarps were smaller, whitish, hard, knobbly, and when older in the forest turned first to a yellowish colour then cinnamon in colour.

Obviously, there are many methods that can be used to preserve the fruiting bodies until needed and then prepare them for use. The method which follows does work. It was found that the sporocarps could be successfully dried in a forced draught oven for 3-4 days at 25C and then kept in glass jars at room temperature for 5 months. When required for use they were cut into small pieces and ground in a blender to pass through a 1 mm sieve. In a trial the spore powder was added to water and applied to the nursery beds at the rate of 4 gm/5 litres/m2.

In a production exercise that I have data for, 20 kg of sporocarps were ground up, (having been received at the nursery as a gooey decaying mess) stirred vigorously and strained into 1200 litres of water (the strained solids being re-ground and re-irrigated through the sieve into the suspension), and the 1200 litres applied by conventional spray to 10 hectares of nursery bed. The sieve was nothing specially sophisticated either; a couple or three layers of woven polypropylene sacking.

The best time to spray the spore suspension on to the nursery beds is after the seedling cotyledons have opened and after the seedling roots have begun to branch.

An alternative method is to coat the tree seed with spores prior to sowing. The method used was to wet the seeds by soaking them in a 1:500 solution of latex:water for 1-2 minutes. The wet seeds, in lots of 250 gm were placed in plastic bags with 100 gm of ground sporocarps and were shaken until all the seeds were evenly coated with spores. The coated seeds were placed on trays and dried in a forced draught oven at 22C for 22 hours. The seeds were then sown in the normal way. Each seed was coated with about 9 x 106 spores.

Since I began this page, it has come to my attention through helpful correspondents, that the flora of mycorrhizal fungi species available to D.fir on the west coast of North America is larger than that available in New Zealand by an order of probably one to two thousand. I guess that seed imports to NZ would leave root fungi behind. So it is not surprising that NZ foresters have something to gain by paying attention to this matter. However, what surprises me more is that there is still so much to be learned about the inter-relationships between fungi and D.fir in North America. For example, Daniel Wheeler of Oregon White Truffles reported to me that one 2/2 seedling 56 cm tall planted next to a tree which had shown evidence of mycorhizal infection with a particular Rhizopogon species, grew 2.9 metres taller the next year and another 1.8 m the year following. Such rates of height increment for D. fir are extraordinary.

Some readers will notice that the research work and techniques to which this page refers are many years old, and might conclude that it's all old-hat stuff and has probably been superceded.

That's very much not the case.

In recent years and months, Dr Ian Hall and co-workers at another research agency than FRI, have taken up studies of the health and vigour of Douglas-fir in relation to mycorrhizal fungi, and have not only demonstrated that appropriate mycorrhizae are essential to good health and growth of Douglas-fir, but that mycorrhizae capable of infecting D.-fir seem to be absent from cooler southern New Zealand sites now being afforested with D.-fir. He has gone on to develop successful techniques for thorough innoculation of the container-grown seedlings being used to establish some new forests.

To read more about this from where he works, click hereand what he has authored, click here

To index.

Site preparation. To index.

Seedling lifting and preparation for lifing and planting.

One of the main reasons for requiring that seedlings achieve a certain minimum root collar diameter and height is that they need a certain volume of stem within which to store starches and sugars so as to be able to deal with what lies ahead and still have the energy to grow. Seedlings in sunlight engage in photosynthesis, and produce sugars and starches. In the dark they respire, and convert these sugars and starches into the energy they need to live. Cold does slow the respiration process, so that often nurseries use cold stores to hold lifted seedlings moist and in the dark between lifing and planting.

Seedlings often have their roots trimmed at or around the lifting stage so as to enable easier and more satisfactory planting. If the roots are severed cleanly with a sharp instrument, they are better able to develop a healing callus over the cut surface. If a callus develops, the seedling will produce new roots from the callus for feeding and anchorage. The seedling needs all the starch and sugar it can obtain in order to heal, develop new roots, and promptly resume growth after planting. The less time a seedling spends in the dark between lifing and planting, and the bigger it is, the more energy reserves it has for healing and early growth resumption.

The best procedures for seedling supply arrange that seedlings are lifted straight from the nursery beds into mini-containers that then go immediately to the planting site; just as in the 'just-in-time' components system used by many Japanese factories.

Procedures that involve factory buildings for the processing of seedlings, followed by lengthy storage periods both at the nursery and on the planting site, are counter-productive in respect of seedling healing and growth.

I still have a vivid memory of one compartment of D. fir that covered an even hill slope, that I viewed many times from the crest. The planting lines ran straight downhill. The same nursery lot of seedlings was used for planting this whole slope. As one walked along the ridgetop and passed the ends of the lines of young trees, at age 10 the trees of each individual line were fairly uniform with regard to survival and growth. There appeared to have been four men in the planting gang, because, in the same order all along the ridge, one row would have 50% survival and small trees, the next two rows would have distinctively better survival and growth, and the fourth row had nearly 100% survival and the tree height was about 300% that of the first row in the series. Clearly, each member of the planting gang had a consistent style of handling and planting the seedlings. The best mycorrhiza in the world would probably not have overcome the handicaps imposed on the trees by the worst planters in this gang.

To index.

Planting technique. To index.

Weed control. To index.

References.

  • Chavasse, C. G. R. (Collator and editor) 1981. Forest Nursery and Establishment Practice in New Zealand - FRI Symposium No. 22, 23 - 27 March 1981. pp. 591. New Zealand Forest Service. Forest Research Institute. Unpublished, no ISBN.
  • Chu-Chou, Myra. 1979. Mycorrhizal fungi of Pinus radiata in New Zealand. Soil Biol. Biochem. 11 (557 - 562)
  • Chu-Chou, Myra; and Lynette J. Grace. 1977. Mycorrhizal Study of Douglas fir. (1) Annotated Bibliography. New Zealand Forest Service, Forest Service Research Institute, Soils and Site Productivity Report No. 85, 1977 (unpublished). ODC: 181.351:174.7 Pseudotsuga menziesii (048.1) (67 entries from nine countries).
  • Chu-Chou, Myra; and Lynette J. Grace. 1977. Mycorrhizal Study of Douglas fir. (2) Fungal symbionts. New Zealand Forest Service, Forest Service Research Institute, Soils and Site Productivity Report No. 87, 1977 (unpublished). ODC: 181.351:174.7 Pseudotsuga menziesii.
  • Chu-Chou, Myra; and Lynette J. Grace. 1978. Mycorrhizal Study of Douglas fir. (3) Endogone flammicorona as a mycorrhizal symbiont in New Zealand. New Zealand Forest Service, Forest Service Research Institute, Soils and Site Productivity Report No. 92, 1978 (unpublished). ODC: 181.351:174.7 Pseudotsuga menziesii.
  • Chu-Chou, Myra; and Lynette J. Grace. 1978. Mycorrhizal Study of Douglas fir. (4) Tuber sp. as a mycorrhizal symbiont in New Zealand. New Zealand Forest Service, Forest Service Research Institute, Soils and Site Productivity Report (Internal Report No. 61) Project SP8.
  • Chu-Chou, Myra; and Lynette J. Grace. 1979. Mycorrhizal Study of Douglas fir. (5) Introduction of Rhizopogon vinicolor into Cambridge nursery. New Zealand Forest Service, Forest Service Research Institute, Soils and Site Productivity Report (Internal Report No. 67) Field experiment A681/2.
  • Chu-Chou, Myra; P. J. Knight and Lynette J. Grace. 1978. Mycorrhizal Study of Pinus radiata (3) Introduction of Specific Mycorrhizal Fungus into new nursery areas. New Zealand Forest Service, Forest Service Research Institute, Soils and Site Productivity Report No. 97, 1978 (unpublished). ODC: 181.351:174.7 Pinus radiata.
  • Fowells, H. A.; 1965. Silvics of Forest Trees of the United States. Agriculture Handbook No. 271; Division of Timber Management Research, Forest Service, U. S. Department of Agriculture, Washington D.C. No ISBN. LCCC Agr 65-273.
  • Gilmour, J. W.; 1958. Chlorosis of Douglas fir. N Z Journal of Forestry. 7: (4 - 106).
  • James, R N. 1985, Douglas fir - a technical brief. In proceedings of 'Douglas Fir Workshop - Nelson' 26 - 28 March 1985. NZ Forest Service unpublished collection of papers. pp. about 170.
  • Schopmeyer, C. S.; 1974. Seeds of Woody Plants in the United States. Agriculture Handbook No. 450; Forest Service, U. S. Department of Agriculture, Washington D.C. No ISBN. LCCC 73-600133.
  • Sinclair, W. A.; 1974. Development of Ectomycorrhizae in a Douglas-Fir nursery: I. Seasonal Characteristics. Forest Science 20-1; (51 - 63).
  • van Dorsser, J. C. 1981. Seedling Conditioning. In Chavasse 1981. pages 128 - 141.
Supplementary references

The Forest Research Institute of the once-upon-a-time NZ Forest Service has been restructured into what is called in the current jargon a 'Crown Research Institute'. Crown Research Institutes are Limited Liability Companies and have the Crown (the State) as the major shareholder, but nevertheless have to bid for research moneys from the State, and have to compete competitively for more. As a result, research findings are often kept secret (especially if they are the product of contracted research), rather than being made available through in-house reports or through published peer-reviewed papers as used to be the case. It is quite possible that Internal Reports will not be made available for perusal, so I have listed below what seem to me to be the most significant references used by Dr Myra Chou in her Internal Reports. The annotated bibliography is a bit of a problem however; it comprises only references - 67 of them! If you want these listed, please contact me.

  • Baylis, G. T. S. 1967. Experiments on the ecological significance of phytomycetous mycorrhizas. New Phytol. 66: 231 - 243.
  • Baylis, G. T. S. 1969. Synthesis of mycorrhizas in Podocarpus and Agathis with Endogone spores. Nature 221: 1267 - 1268.
  • Baylis, G. T. S. 1971. Endogonaceous mycorrhizas synthesised in Leptspermum (Myrtaceae). N.Z.J. Bot. 9: 293 - 296.
  • Cooper, K. M. 1976. A field survey of mycorrhizas in New Zealand ferns. N.Z.J. Bot. 14: 169 - 181.
  • Donald, G. M. 1975. Mycorrhizal inoculation for pines. South Afric. For. J. 92: 27 - 29.
  • Eccher, A. and Rambelli, A. 1966. The influence of mycorrhizal inoculation on the development of Pinus radiata. Pubbl. Cent. Sper. For. Roma. 9: 11 - 22.
  • Fassi, B. 1965. Ectotrophic mycorrhizae produced by Endogone lactiflua Berk. on Pinus strobus L.   Allonia 11: 7 - 15.
  • Fassi, B., and Palenzona, M. 1969. Mycorrhizal synthesis between Pinus strobus, Pseudotsuga menziesii and Endogone lactiflua. Allonia 15: 105 - 114.
  • Fassi, B., Fontana, A. 1967. Sintesi micorrizica tra Pinus strobus e Tuber maculatum 1. Micorrize e sviluppo dei semenzali nel secundo anno. Allonia 13: 177 - 186.
  • Fassi, B., Fontana, A. and Trappe, J.M. 1969. Ectomycorrhizae formed by Endogone lactiflua with species of Pinus and Pseudotsuga. Mycologia 61:412 - 414.
  • Hall, I. R. 1977. Species and mycorrhizal infections of New Zealand Endogonaceae. Trans. Brit. Mycol. Soc. 68: 341 - 356.
  • Johnson, P. N. 1977. Mycorrhizal Endogonaceae in New Zealand forest. New Phytol. 78: 161 - 170.
  • Lange, M. and Hora, F. B. 1975. Collins Guide to mushrooms and toadstools. Collins Clear-Type Press.
  • Morrison, T. M. 1956. Mycorhiza of silver beech. N.Z.J. For 7: 47 - 60.
  • Rambelli, A. 1966. Experiments in mycorrhizal inoculation of Pinus radiata. Suppl. to Annales de Institut Pasteur, Paris III: 303 - 306.
  • Rayner, M. C. 1938. The use of soil or humus inocula in nurseries and plantations. Emp. For. J. 17: 236 - 243.
  • Rinaldi, A. and Tyndalo, V. 1972. Mushrooms and other fungi. Hamyln Publishing Group Ltd.
  • Singer, R. 1962. The Agaricales in modern Taxonomy. J. Cramer Pub.
  • Smith, A. H. and Zeller, S. M. 1966. A preliminary account of the North American species of Rhizopogon. Memoirs of the New York Botanical Garden 14: 1 - 177.
  • Theodorou, C. and Bowen, G. D. 1970. Mycorrhizal responses of radiata pine in experiments with different fungi. Aust. For. 34: 183 - 191.
  • Theodorou, C. and Bowen, G. D. 1973. Inoculation of seeds and soil with basidiospores of mycorrhizal fungi. Soil Biol. Biochem. 5: 765 - 771.
  • Trappe, J. M. 1962. Fungus associates of ectotrophic mycorrhizae. Bot. Rev. 28: 538 - 606.
  • Trappe, J. M. 1964. Mycorrhizal hosts and distribution of Cenococcum graniforme. Lloydia 27: 100 - 106.
  • Trappe, J. M. 1969. Mycorrhiza-forming ascomycetes. Proc. 1st North American Conf. on Mycorrhizae, U.S.D.A., Forest Service; p. 19 - 37.
  • Trappe, J. M. and Gerdemann, J. W. 1972. Endogone flammicorona sp. nov., a distinctive segregrate from E. lactiflua. Trans. Brit. Mycol. Soc. 59: 403 - 407.
  • Trappe, J. M. and Strand, R. F. 1969. Mycorrhizal deficiency in a Douglas fir region nursery. For. Sci. 15: 381 - 389.
  • Wright, E. 1964. Mycorrhizae and survival of Douglas fir seedlings. Res. Note 50. For. Management Res. Lab. Oregon State Univ.
  • Wright, E. 1971. Mycorrhizae on Douglas fir and Ponderosa pine seedlings. Res. Bull. Ore. For. Res. Lab. No. 13.
  • Zak, B. 1971. Characterisation and classification of mycorrhizae of Douglas fir. II. Pseudotsuga menziesii and Rhizopogon vinicolor. Can. J. Bot. 49: 1079 - 1084.
To index.

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