Farm Forestry New Zealand

Has New Zealand missed the boat with the members of the Abies genus?

Charlie Low, New Zealand Tree Grower August 2011.

A forester from Denmark, Ib Thulin, was appointed in charge of genetic and tree improvement research at the Forest Research Institute in the early 1950s. He imported what seed was available, but quickly realised that he would need to organise seed collections from a wide range of species. He arranged for a second forester from Denmark, Egon Larsen, to be appointed and organised Egon’s itinerary so that he went directly to America from Denmark.

Egon spent months collecting seed in the Pacific north west − Washington, Oregon and California. He collected numerous seedlots from across the natural range of a large number of forest tree species, most of them Douglas fir. He collected or often arranged for collections of seed from up to eight locations of Abies grandis, Abies concolor, Abies procera and Abies magnifica. It was a masterly and well executed job, with precise documentation and photographs as well as seed. The four species cover a wide climatic range as A. grandis is found at low elevation, A. concolor substantially higher up and the other two species even higher.

Mexican refuge

Ib was aware that Mexico had acted as a refuge for forest tree species that were driven south in the last ice age, so he went to Mexico to collect seed. The Mexican collections of Abies comprised A. religiosa and A. vejari. Abies religiosa is thought to be so named because the upper whorl of branches on the leader forms a perfect representation of the Christian cross. However its greatest distinction is that it hosts the annual migration of monarch butterflies from Canada to Mexico. There are photographs showing hundred of thousands of butterflies on a single tree.

Ib enlisted the help of John Miller, Eric Appleton and John Carruthers to raise plants from the seed and establish a series of species and provenance trials throughout New Zealand between 1957 and 1968. This article focuses on the Abies species and provenance trials which were usually adjacent to provenance trials of Douglas fir, with sitka spruce, western hemlock and other promising species nearby.

Trial layouts

Nine Abies species were tested across 19 sites, with uneven distribution of species across these sites. The species were −

• A.religiosa sacred or oyamel fir from Mexico
• A. concolor white fir
• A. grandis grand fir
• A. magnifica
• A. firma momi fir from Japan,
• A. nordmanniana Caucasian fir
• A. vejari silver fir
• A. bracteata bristlecone fir
• A. procera.

Trial layouts featured large blocks of 100 to 144 trees for each seedlot. Early growth was monitored by site inspections but the comments were universally discouraging. Growth was very slow and reports of yellowed foliage and dying trees were common. Many sites were abandoned as being unlikely to form stands by age 15. It is believed that lack of the appropriate mycorrhiza is a probable cause of the failure of many of these species.

After the universally slow start over all trial sites, the Abies species were pretty well forgotten until around age 30, when casual inspections revealed that their status had changed dramatically. What had been chlorotic trees lagging well behind Douglas fir had become much healthier than the Douglas fir and were adding a lot of volume.

This was particularly noticeable at Gwavas where the two trials were both thinned at the same time and the A. grandis had been pruned to six metres. A check on foliage retention revealed that while the Abies carried 10 years of living foliage, Douglas fir had only between two and three years of foliage. The foliage loss by Douglas fir was attributed to the swiss needlecast fungus Phaeocryptopus guaemanni, to which A. grandis appeared to be immune.

Most of these species were also disappointing in their growth and survival. There were two that showed promise, A. grandis and A. concolor. This article concentrates on the potential of these two firs.

Assessments

Four sites that appeared to be doing well were assessed for diameter at breast height in 2007. Rankleburn was included even when the site had been abandoned in 1974. The first site to be assessed was Gwavas where the A. grandis trial had been thinned to between 400 and 600 stems per hectare to correct for patchy stocking following a difficult establishment phase. The A. grandis was growing spectacularly well and A. concolor reasonably well.

Abies trial sites which were assessed
Site	Latitude	Longitude	Altitude metres	Mean temp °C	Annual rainfall mm
Long Mile	38° 09	176° 16	300	12.5	1500
Gwavas	39° 42	176° 24	500	10.9	1523
Hanmer	42° 30	172° 48	500	7.8	1326
Rankleburn	46° 00	169° 12	168	9.7	906

Assessments showed that some species had more than 2,400 living stems per hectare, but these overstocked stands did not produce the greatest volumes. Gwavas was the best of the A. grandis sites with standing volumes of around
1,500 cubic metres per hectare at age 47 and a mean annual increment of 30 cubic metres. This compares with the adjacent 1959 Douglas fir provenance trial which had an average mean annual increment of 19 cubic metres for the 20 best provenances with the best at 27 cubic metres.

All species were assessed, but some species were at a disadvantage. The A. procera, A. magnifica and A. bracteata were in decline, with dominant trees dying every year. The A. vejari had been planted among redwoods and growth was affected, although the trees were healthy. The A. firma was represented by few trees and was not in the same class as A. grandis and A. concolor. The A. nordmanniana was represented by a single New Zealand seedlot from an arboretum and appeared to have inbreeding issues.

Grand fir Abies grandis

Abies grandis seedlots in the 1959 provenance trial
Seedlot	Provenance	Latitude	Longitude	Altitude metres
FRI 56/723	Ophir, OR	42° 39'	124° 24'	130
FRI 56/724	Blue Lake, CA	40° 55'	123° 50'	650
FRI 56/725	Dehaven, CA	39° 39'	123° 45'	175
FRI 56/726	Mendocino, CA	39° 19'	123° 48'	50
FRI 54/378	Hanmer, NZ
FRI 54/457	Vancouver Island, Canada	49° 50'	125° 25'	45
S54/541	Queenstown Gardens, NZ
FRI 55/501	Camano Is, WA	48° 15'	122° 40'	150
FRI 55/502	Leaburg, OR	43° 45'	122° 30'	250

Abies grandis was planted with up to nine seedlots on 19 sites in 1959. This fir species was expected to be the best adapted and fastest growing of the various species and this was confirmed by the 2007 assessment.

The Gwavas site had been thinned to 400 stems a hectare in 1981 and this helped the trees reach diameters of over 80 cm for the best trees. Provenance differences were obscured by differences in stocking rate as 400 stems was evidently lower than the ideal stocking for a species with such good foliage health and shade tolerance. A count of green needles on some branches of edge trees showed that foliage could be retained for 10 years, while three years of foliage was the best observed on the neighbouring Douglas fir.

Mean annual increment was impressive at around 30 cubic metres per hectare each year. Current annual increment would be much higher again, as the trees got away to a very slow start and hardly grew for the first 10 years. A recent assessment of the neighbouring Douglas fir provenance trial returned a mean annual increment of 27 for the best provenance and 19 for the top 20 provenances.

The Mendocino provenance was expected to be amongst the best as it was from the mildest climate, but the extreme growth shown here would have been boosted by the high stocking of 550 stems per hectare. The second ranked provenance was rather surprisingly from Vancouver Island, which also had a higher stocking of 600 stems per hectare.

The provenance that appeared to have the worst volume was the provenance from Dehaven, but this was a result of very low stocking of 250 stems per hectare. Several provenances grew better than both of the New Zealand seedlots. The strong latitudinal trend for growth rate shown by sitka spruce or Douglas fir in New Zealand was not apparent.

Slow start

The A. grandis trial at Hanmer also started slowly, with a number of file notes documenting slow early growth. Unfortunately the Hanmer trial was not thinned, so the stocking was still very high at 1,500 to 2,000 stems a hectare. As a result there were many suppressed trees and even maximum diameters were well down on those at Gwavas. Once again the Mendocino provenance appeared to be the best at Hanmer, but there was no clear pattern of growth being influenced by latitude.

The Long Mile site was planted as 11-tree rows for demonstration purposes. It received a thinning to a good stocking between 550 and 1,200 stems per hectare. Unfortunately, no New Zealand seedlots were planted in the Long Mile, but the growth of the Mendocino provenance was outstanding.

The Rankleburn site suffered from browsing and was reduced to such a low stocking that significant Douglas fir regeneration was able to get away early in the life of the trial. It was thinned about four years before being assessed and a number of Douglas fir trees were retained in every plot.

White fir Abies concolor

Description of seedlots used in the 1959 A. concolor trial
Seedlot	Provenance	Latitude	Longitude	Altitude metres
FRI 55/507	Sierra, CA	37° 01'	119° 10'	1800
FRI 56/600	Nevada, CA	39° 15'	120° 52'	1700
FRI 56/727	Mt Hood , OR	45° 08'	121° 38'	1025
FRI 56/728	Crater Lake, OR	42° 46'	121° 59'	1575
FRI 56/729	Klamath , OR	41° 53'	122° 12'	1360
FRI 56/730	Lassen, CA	40° 07'	121° 29'	1300
FRI 56/731	Mendocino, CA	39° 44'	122° 51'	1870
FRI 56/732	Eldorado, CA	38° 44'	120° 10'	1970
FRI 56/733	Eldorado, CA	38° 38'	120° 31'	1430
FRI 56/734	Sequoia, CA	36° 07'	118° 31'	1970
S56/538	Queenstown Gardens, NZ

Abies concolor grows on sites of higher elevation than A. grandis, but can sometimes hybridise. Therefore we would expect rather slower growth rates than A. grandis on the same, relatively low elevation sites and this appeared to be the case on all sites. The trial design featured smaller 36-tree plots with more replication than the A. grandis plots. The Rankleburn site was not assessed as there had been regeneration from A. grandis, Douglas fir had been blanked into the plots and the thinning had favoured the wrong species.

One seedlot from Eldorado has growth very much better than the rest of the seedlots on all sites and fairly similar to A. grandis seedlots on the same site, even where both species have had different silviculture. It was possible that this seedlot may have contained a proportion of hybrids. Both heights and diameters were less than A. grandis, but stocking rates were high and it appeared that A. concolor could sustain much higher stocking than most species.

Conclusions

Abies grandis and A. concolor have proved to be capable of high rates of volume growth in New Zealand conditions. These species enjoy exceptional foliage health, which may make them more shade tolerant than Douglas fir. Abies grandis was capable of better volume growth rates than Douglas fir in spite of a protracted establishment phase. It would be wise to note the positive response of the trees to an application of fertiliser and duff to the A. grandis trial at Hanmer in any future establishment of A. grandis. Both species had good form, with straight stems, regular branching and few forks.

The best provenance of A. grandis was from Mendocino county in California, but the trend of increasing growth rate with more southerly latitudes that has been observed in New Zealand-grown Douglas-fir was not seen here.

The provenance of A. concolor which was the consistent the winner on all sites was seedlot from Eldorado national forest in California. The outstanding volume growth suggested that this seedlot may be a hybrid between A. concolor and A. grandis as this seedlot was collected at a relatively low elevation and may have been collected in the intermediate zone.

The trials of A. magnifica and A. procera established successfully and appeared in excellent health for several decades. However, they are now in decline, with several dominant trees dying every year, the most likely cause being some sort of root rot. As they are high altitude species, and the New Zealand trials were planted at low altitude, the most likely explanation was that they have not evolved to cope with soil fungi found on mild sites.

The foliage health of these Abies species was far superior to that of Douglas fir in adjacent stands. A future role of Abies grandis may be in mixture with Douglas fir as it is in natural forests in the Pacific northwest. The Douglas fir would establish well and draw the A. grandis up, then the A. grandis would buffer the transmission of Phaeocryptopus spores between the Douglas fir trees.

The most important role of these trials has been to identify the best seed source for any future plantings.The New Zealand seed sources are inferior, even though they have had an extra generation in which to adapt to the conditions.

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