Growth Cessation and Autumn-frost Hardiness in One-year-old Picea abies Progenies from Seed Orchards and Natural Stands

One-year-old seedlings of Norway spruce [Picea abies (L.) Karst.] from seed orchards and natural stands were compared with respect to growth cessation and autumn-frost hardiness. The correlation among traits related to growth, growth cessation and frost hardiness on the same plants in two sets of environmental conditions was assessed. Total height, the degrees of shoot lignification and frost hardiness, and the timing of height growth cessation and budset were recorded at two nurseries in central and northern Sweden. Nine seed-orchard seed-lots were compared with seed from 26 natural stands originating from 56° N to 66° N in Sweden. Latitude explained 55-87% of the statistical variation among stands in the analysed traits at the central nursery and 49-84% at the northern nursery. On average, the seed-orchard progeny performed similarly to progeny from natural stands located 1-2° south of the origin of the seed-orchard clones. Reference material representing a geographical gradient was found to be a valuable aid when interpreting the results of growth cessation and frost-hardiness evaluations.     

Phenotypic Differences Between Natural and Selected Populations of Picea Abies. I. Frost Hardiness

The frost hardiness of non-juvenile Norway spruce [Picea abies (L.) Karst.] populations growing in northern Sweden (63°54' N) was monitored during 1996-1997. The investigated progenies originated from 12 natural populations and six seed orchards located between 58° N and 68° N in Sweden. Frost hardiness of needles was assessed by measuring chlorophyll fluorescence and electrolyte leakage after freezing. The loss of frost hardiness in 1-yr-old needles during spring occurred slightly earlier in populations originating north of 63°30' N than in those originating further south. Dehardening was slightly delayed in selected populations compared with natural populations of similar origin. The level of frost hardiness during autumn was higher in populations originating north of 63°30' N than in those originating south of this latitude, but there were no clear differences in frost hardiness between selected and natural populations of similar origin. The results are discussed in relation to climatic factors and inherent growth rhythms.     

No difference in frost hardiness between high and low altitude Pinus sylvestris (L.) offspring

Seedlings representing offspring from 46 Swedish natural stands of Pinus sylvestris (L.) from latitude 63° to 68° and altitude 75 to 675 m were artifically frost hardened and tested for autumn frost hardiness using artifical freeze testing in a programmable freezing chamber. A clinal variation in frost hardiness was observed over latitude. Altitude had no effect on the frost hardiness. The results are discussed in relation to the reproduction‐ and migration biology of P. sylvestris.     

Effect of maternal soil treatment on first year growth and autumn frost hardiness of Pinus sylvestris L. full‐sib families

After‐effects of maternal soil treatment, controlling for photoperiod and weather conditions, were tested in a nursery experiment with Pinus sylvestris L. seedlings. Three full‐sib crosses were replicated in 4 different soil treatment plots of a grafted experimental seed orchard (63"54'N). Weight of filled seeds, percentage of empty seeds, first year hypocotyl and epicotyl length, and autumn frost hardiness (from artificial freeze testing) were evaluated. Systematic effects from maternal soil treatment were small compared to family differences for all characters studied. However, epicotyl length of the progenies showed a positive relationship with N needle content of the mother grafts. The results also indicated an important interaction between maternal soil treatment and autumn frost hardiness of the families. It is suggested that the altered mother tree treatment could lead to a change in progeny performance, corresponding to a 1.5 degree difference in latitudinal origin of natural stand seedlings. The results demonstrate the advantages of providing the mother tree with uniform conditions in early progeny testing.     

Frost hardiness gradients in shoots and roots of picea mariana seedlings

Frost hardiness of tissues along the length of the stem and the root was investigated in first‐year black spruce (Picea mariana (Mill.) B.S.P.) seedlings. Frost hardiness of 1 cm long stem and root segments was evaluated based on Index of Injury, calculated from post‐freezing electrolyte leakage. Frost hardiness was tested approximately weekly beginning seven weeks after seedlings were transferred from an 18 to a 10 h photoperiod, both at day/night temperatures of 26°C/16°C. Trees were transferred to temperatures of 10°C day and 5°C night at a 10 h photoperiod after a further 18 days. Frost hardiness was greater at the terminal bud and least at the root tips. Although shoots were generally more frost hardy than roots, differences in hardiness along the stem and root axes were gradual, rather than abruptly differing at the shoot‐root interface. All tissues, including root tips, increased in frost hardiness after conditioning for 18 days under short photoperiods (10 h) and warm temperatures (26?C/16°C, day/night). Under cold temperatures (10°C/5°C, day/night) all tissues, excepting the root tips, tolerated — 16°C with little subsequent electrolyte leakage.     

Effects of nutritional factors on frost hardening in Larix leptolepis (Sieb & Zucc.) Gord.

A method for estimating frost hardiness in seedlings of Larix leptolepis in their first stage of acclimation is demonstrated. Cuttings of the shoot tip were frozen linearly from +2°C to ‐36°C. The viability was determined by TTC‐assay. Data were fitted to a logistic regression model, and hardiness was calculated from the fitting parameters. It was shown that hardiness is influenced by the duration of the fertilizer application period. No effect of the nutrient status of N, P or K in the shoots was found.     

Phenotypic changes in progenies of northern clones of Picea abies (L.) Karst. grown in a southern seed orchard

Results are presented from three different field trials comparing controlled crossed materials of Norway spruce from the southern seed orchard at Lyngdal (58° N) with open‐pollinated progenies from the same mother trees standing in the northern natural forest (63–66° N). The seed orchard progenies flushed consistently later in the spring, terminated leader shoot growth later in the summer, had higher frequencies of lammas shoots, were delayed in lignification during autumn, and were 15% taller at age seven years from seed. The difference between the orchard‐ and the natural stand material appeared to be permanent from age four to age seven. It is suspected that the non‐native environment in the seed orchard could affect the genotypic performance of the seed orchard progenies.     

Forest structure classes in central Finnish Lapland

Structure classes and changes in the vegetation attributable to the altitude of the terrain were studied in the Hammastunturi virgin coniferous forest area. The area is located in Finnish Lapland, approximately 250–350 km to the north of the Arctic Circle (68°15'N; 68°45'N). The following forest classes were formed on the basis of the ground vegetation and stand coverage: (1) Pine stands, with birch admixture (n=14), (2) Vaccinium‐vitis‐idaea‐type pine stands (n = 24), (3) Vaccinium myrtillus‐type pine stands (n = 17), (4) mixed stands, dominated by pine (n = 8), (5) mixed stands, dominated by spruce (n=18), (6) paludified spruce stands (n = 3) and (7) vigorously growing spruce stands (n = 6). The forest structure classes were depicted using DCA ordinates. The differences were more distinct than those between the normal forest type classifications of the same sample plots. The basal area and volume of pine decreased with increasing altitude, while the proportion of spruce on those sample plots where it was present increased. Birch was present at an equal frequency at all altitudes. The floral composition and between‐species abundance changed along with increasing altitude. The change in floral frequencies could not be designated to a specific altitude zone.     

Mating System and Pollen Contamination in a Pinus brutia Seed Orchard

Mating system parameters and pollen contamination were estimated in an 11-year-old Pinus brutia Ten. clonal seed orchard, located in Antalya, Turkey, with the aid of isozymes. Isozyme analysis was performed on both maternal (megagametophyte) and embryo tissues of seeds collected from the seed orchard and the surrounding natural stand. Fourteen loci encoding nine enzyme systems were assayed. Based on a multilocus estimator, the proportion of viable seeds originating from outcrossing (tˆ_m) in the seed orchard was found to be 0.947; the remainder (0.053) was due to selfing. We estimated that 85.7% of the orchard seed resulted from pollen contamination by trees in surrounding stands. This may be related to the young age and subsequent low pollen production of the orchard. Only 9% [i.e., 1.0−0.857 (contamination)−0.053 (selfing) = 0.090] of the orchard offspring was due to cross-pollination among clones within the orchard. Due to the high level of pollen contamination, it is estimated that genetic gain in this seed crop is less than 57% of that expected if all offspring resulted from random mating among orchard clones (i.e., no contamination).     

Higher resistance of the offspring of Scots pine trees resulting from natural regeneration in old foci of Heterobasidion annosum root rot

Abstract

Heterobasidion annosum (Fr.) Bref. is a fungal pathogen causing annosum root rot – one of the most economically important diseases in coniferous stands. The major aim of this study was to compare the resistance of the offspring of Scots pine trees (Pinus sylvestris L.) from seed orchards and the offspring of trees that were naturally reproduced in old foci of the disease. In experiments conducted in vitro, we used 960 seedlings which were grown from seeds collected from 60 trees in 6 old foci of the disease and 640 seedlings grown from seeds collected in 4 seed orchards. The offspring of trees from seed orchards after inoculation with H. annosum had nearly twofold higher mortality rate than the seedlings developed from the seeds collected in old foci of the disease. This suggests that the offspring of self-sown trees in old foci of the disease has a greater, genetically conditioned resistance to annosum root rot.     

Impact of Fertility Variation on Gene Diversity and Drift in two Clonal Seed Orchards of Teak (Tectona grandis Linn. f.)

Two 25 year old teak clonal seed orchards comprising 15 (CSO-I) and 20 clones (CSO-II), respectively, selected mostly from moist forests of Western Ghats (latitude 10° N) in southern India, were evaluated for fertility, offspring diversity, and genetic drift. The orchards differed in fertility of clones as well as flower and fruit production per ramet. Fertility was highly skewed in CSO-II, where one clone (originating from higher latitude −17° N, in Eastern Ghats of peninsular India) produced 55% of the fruits and 68% of the flowers in the orchard, in contrast to a similar contribution from four most fertile clones in CSO-I. Fertility variation, measured as `sibling coefficient' (1.7 in CSO-I and 8.3 in CSO-II), was high in CSO-II resulting in high coancestry and low effective population size (3 times lower than CSO-I) in the seed crop. In CSO-I, 58% of the clones contributed effectively to seed production compared to only 12% effective contribution resulting in eight times higher genetic drift in CSO-II. Placing limits on how much seed can be collected per clone might be useful in restricting over representation of highly reproductive clones thereby increasing genetic diversity in the seed crop.     

Within‐population variation in autumn frost hardiness and its relationship to bud‐set and height growth in Picea abies

Artificial freezing tests were performed with two sets of 12 full‐sib families of Picea abies. Each set was selected from a complete diallel cross performed within a natural population. Significant differences in autumn frost hardiness were observed between the two populations, which originate from the same altitude and longitude approximately 60 km apart. Substantial variation in frost hardiness was observed within both populations. Significant pheno‐typic correlations at the individual level were found between freezing injury and the two traits terminal bud‐set and height growth year one. However, no significant relationships were present between freezing injury and bud‐set at the family level, indicating that bud‐set cannot be used to predict autumn frost hardiness for families.     

马尾松2个世代种子园6年生家系生长的遗传变异与增益比较

【目的】研究与评价马尾松一代、二代无性系种子园的遗传增益及改良效果,指导马尾松良种选育、生产及应用。【方法】利用营建在浙江省淳安县燕山林场和福建省邵武市卫闽林场的6年生马尾松一代和二代自由授粉家系遗传测定林,分析不同世代种子园子代生长性状的遗传变异,并进行家系育种值估算及生长评价。【结果】马尾松不同世代的种子园子代生长差异很大,其树高、胸径和单株材积等生长量显著大于马尾松优良天然林分的混系子代,其中一代种子园子代各家系单株材积表型值和育种值分别大于优良天然林分混系55.78%~84.62%和40.66%~71.39%,二代其值分别大于优良天然林分混系58.96%~108.97%和42.97%~91.89%,二代种子园子代的平均生长量和遗传稳定性总体上高于一代种子园子代。树高、胸径和单株材积等主要生长性状在世代内家系间的生长差异均达极显著水平,在一代种子园子代中最优家系的树高、胸径和单株材积分别大于最差家系21.94%、30.72%和97.75%,在二代种子园子代中最优家系的树高、胸径和单株材积分别大于最差家系23.42%、29.60%和90.09%,说明种子园中对亲本材料的再选择非常重要。依据子代的单株材积育种值在两测定点的位次及其变幅大小,将38个家系分成速生型、较速生稳定型、较速生不稳定型和慢生型4类,各类所占家系数分别有23.68%、26.32%、21.05%和28.95%,其中速生型和较速生稳定型家系所对应的亲本无性系可作为新建马尾松二代无性系种子园的优良建园材料。种子园子代主要生长性状的地点×家系、区组×家系的互作效应极显著,说明各家系在不同立地环境中生长表现不一致。【结论】马尾松无性系种子园良种效益显著,二代增益大于一代。通过选择速生型和较速生稳定型家系将有助于种子园建园亲本的再选择、现有种子园的留优去劣疏伐和重建新的种子园。鉴于子代主要生长性状的基因型与环境互作使各家系在不同立地环境中生长表现不同,建议对子代生长表现突出、结实量较多的无性系进行单系采种利用。     

Seedling cold hardiness, bud set, and bud break in nine provenances of Pinus greggii Engelm.

Cold hardiness and timing of bud set and bud break are important processes that provide protection of nursery seedlings against low temperatures. Seedlings of 9 provenances of Pinus greggii from two different regions of Mexico were tested to determine cold hardiness, bud set, and bud break timing differences. Needle sections were exposed to freezing temperatures to determine an injury index of each provenance. In addition, bud set and bud break timing were recorded through the fall, winter and spring. There were significant differences in cold hardiness between seedlings from northern and southern provenances. At the maximum cold hardiness, the index of injury (LT₅₀) for northern provenances was LT₅₀ = −18 °C, compared to −12 °C for southern provenances. There was a considerable variation among the provenances in the proportion of seedlings that set terminal buds. Seedlings from northern provenances had greater proportions of seedlings that set a terminal bud than seedlings from southern provenances. There were also significant differences in the bud break timing in the following spring among the 9 provenances. Seedlings from northern provenances broke bud earlier than southern provenances. Cold hardiness, bud set, and bud break timing results may be useful to determine how far a specific seed source can be moved from its natural environment.     

Timing of cold temperature exposure affects root and shoot frost hardiness of Picea Mariana container seedlings

Seventeen‐week‐old black spruce seedlings were hardened under short daylengths and one of three short day length environments, which were either warm (24/16°C, day/night) throughout a 10 week hardening period (WW), cool (10/5°C) throughout hardening (CC), or warm for three weeks followed by seven weeks of cool temperatures (WC). Greatest root and shoot frost hardiness resulted from the exposure of seedlings to three weeks of warm followed by seven weeks of cool temperatures. Seedlings receiving warm temperatures throughout hardening increased in root and shoot frost hardiness, but to a lesser extent than seedlings exposed to cool temperatures. The frost hardiness of woody roots was generally greater than that of fine roots, but the extent of the difference in frost hardiness depended on the time since bud initiation and on the hardening treatment.     

Effects of crown-pruning on seed and pollen cone production in two lodgepole pine seed orchards in British Columbia

The effects of top pruning on subsequent seed and pollen cone production in lodgepole pine (Pinus contorta Dougl.) grafted clones in two seed orchards were evaluated. In the older orchard (14 years old), three pruning regimes were applied: an untreated control, a moderate pruning where 25% of the crown was removed and a severe pruning where 40% of the crown was removed. In the younger orchard (ten years old), only a control pruning and a severe pruning (50% of crown removed) were applied. Five-year seed cone production was lower in treated ramets compared to controls in both orchards. However, when cumulative seed cone yields were adjusted for reduced tree heights after pruning, differences were no longer significant in the older orchard. Strong clonal variation was observed in seed cone yields in both orchards. Pollen cone development was less variable among treatments in the older orchard. In the younger orchard, controls consistently produced heavier pollen crops. Pruning recommendations for similar orchards are made and results discussed for reducing the impacts of losses in seed cone yields.Deceased     

Female fertility variation in mature Pinus sylvestris clonal seed orchards

Abstract

Female fertility is the basis for the output of seeds from clonal orchards and its variation is of major interest for the economics and biology of seed orchards, especially for the efficiency and diversity of seed orchard crops. Assessments of female fertility variation in 10 mature (>15 years old) seed orchards of Scots pine (Pinus sylvestris L.) were evaluated and compared. Depending on the individual orchard, fertility variation for each clone was assessed in slightly different ways, e.g. number of strobili, cones, seeds or litre of cones per ramet. Assessments in five of the orchards were made over consecutive years. The main result was that the clonal variation in mean female fertility per surviving ramet was lower than expected from the literature; the Kang–Lindgren sibling coefficient (Ψ) within individual years averaged 1.35. The variation between ramets within clones and years was of similar magnitude as that between clones. Clone by year interactions were noticeable, but were slightly lower than the variation between as well as that within clones in individual years. There was considerable variation in the variance components between years. The limited variation in female fertility indicated that it should not be a selection criterion when selecting clones for a seed orchard. Furthermore, it will not result in large differences between clones in seed set or large reductions in gene diversity in productive Scots pine seed orchards.     

Juvenile radiata pine clonal seed orchard management in Galicia (NW Spain)

A juvenile radiata pine clonal seed orchard (Pinus radiata D. Don) in Sergude (northwestern Spain), comprising 57 clones, was evaluated for fertility, offspring diversity and genetic drift during 4 years. Flower and fruit production was used to asses clone fertility in the orchard. Fertility variation measured as “sibling coefficient” was found to be an average of 1.5, having high genetic diversity (0.99) and low coancestry (0.013). The clones varied in fertility from year to year. Effective population size in the orchard was between 35 and 40, indicating that between 60.30 and 69 %, the clones contributed effectively to seed yield. One way to improve seed yield in the orchard is by increasing the effective population size. Thinning and pruning highly reproductive clones of gibberellin application might be useful in increasing effective population size. The orchard’s parental balance showed consistent improvement over time. Cone and seed characteristics were also investigated. The results showed that significant genetic variation exists among clones for cone width and length; total, sound and empty seed number; as well as 100 seed weight. The seed orchard is still in a juvenile phase; moreover, the broad-sense heritability and variation data obtained in this study could be very valuable in the management practices of the existing radiata pine clonal seed orchard and can be also used for better planning of advanced generation of clonal seed orchards in Spain.     

Fall fertilization of Pinus resinosa seedlings: nutrient uptake, cold hardiness, and morphological development

? Fall fertilization may increase plant nutrient reserves, yet associated impacts on seedling cold hardiness are relatively unexplored.

? Bareroot red pine (Pinus resinosa Ait.) seedlings in north-central Minnesota, USA were fall fertilized at the end of the first growing season with ammonium nitrate (NH₄NO₃) at 0, 11, 22, 44, or 89 kg N ha^?1. Seedling morphology and cold hardiness [assessed by freeze induced electrolyte leakage (FIEL)] were evaluated six weeks after fertilization and following the second growing season.

? Seedling height and number of needle primordia increased with fertilizer rate for both sampling years. Seedlings fertilized with 44 and 89 kg N ha^?1 attained target height (15 cm) after the second growing season. Shoot and root N concentration increased after the first growing season in fall fertilized seedlings compared to controls. Fall fertilized seedlings had lower FIEL (i.e., increased cold hardiness) compared to controls when tested at ?40 °C after the first growing season, but no significant differences in FIEL of control and fertilized seedlings were observed after the second growing season.

? Results suggest that fall fertilization of red pine seedlings can help render desired target height in the nursery, while maintaining or increasing cold hardiness levels.

     

世界松类无性系林业发展策略和现状

本文概述了当前世界集约工业人林发达国家在松类无性系林业发展中采取的策略和研究现状，突出介绍了他们把家系林业和无性系林业结合的经验。同时针对我国近２０年来松类种子园和无性繁殖技术的现状，提出了我国松类良种化工作的发展方向。