DIGITALNA ARHIVA ŠUMARSKOG LISTA
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| ŠUMARSKI LIST 1-2/1966 str. 23 <-- 23 --> PDF |
THE SELECTION OF PLUS TREES IN SWEDEN (Invited paper) by ENAR ANDERSSON* The Royal College of Forestry and The Co-ordination Committee on Forest Tree Breeding and Genetics, Stockholm 50, Sweden. The aim in forest tree breeding (irrespective of which of the more or less advanced forms is applied) may be stated to be: 1) to identify, or 2) to produce artificially superior genotypes of forest trees for use in practical forestry. As is well known, the variable genotypical constitution of cross-fertilized trees can readily be demonstrated by means of vegetative propagation, and, in certain species, by subjecting the trees to endogamy. These are two out of a series of methods which, combined with suitable statistical assessments, can help us to identify the genotype behind the phenotype. A better understanding of the composition of the genetic variation (participating in a complex expression or character), and of the breeding value of outbreeding trees, can be obtained with progenies from complete and incomplete diallel crosses, laid out in well- designed and repeated experiments. On the basis of such crosses and tests, estimates can be made of genetic variability, both general and specific combining ability, environmental effects, and genotype-environmental interactions for different cross-combinations of selected trees within, and between, populations, provenances, and, possibly, species. Although a reliable test of the breeding value of trees and populations must be based on progeny testing, this method is very expensive and time- consuming. In all forest tree breeding programmes, the number of trees and tests must be restricted, at least during the initial stage, to cover only outstandingly good phenotypes with valuable properties from an economic point of view, what are known as plus trees. PHENOTYPE AND GENOTYPE Thus, artificial selection has a special goal, viz. to select the basic material for forest tree seed orchards, and for further selection and breeding, or for collection or raising of forest tree reproductive material. Selection, directed by man, of domestic animals and cultivated plants was practised long before Mendelian laws of inheritance were discovered. In spite of this, it seems that artificial selection, also in the form of mass selection, has led to significant * The section on wood basic denstity has been written by Dr. Börje Ericson, The Royal College of Forestry, Sweden. |
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progress. In many cases there is a great difference between a number of cultivated forms and their wild ancestors. When selection concerns quantitative or continuously varying characters, mass selection can, under certain conditions, lead to substantial improvement, provided that these characters are inherited without manifesting dominance and overdominance in heterozygous loci, without epistasis between genes or different loci, and where environmental influence is only slight. On the above-mentioned assumptions, the response to selection, or the selection gain for sexually propagated plants, can be expected to be a product of the selection differential and the fraction of the total genetic variability of the phenotypic variability. More generally, the selection gains are a product of the selection differential (expressed either in absolute units of measurement or in units of standard deviation of the normal curve, see Falconer, 1960, and Williams, 1964), and the additive portion of the total genetic variability in relation to the phenotypic variability (see also Matthews , 1963 p. 107). Non-additive gene actions, such as dominance and epistatic interactions, and those between the effects of the genes and the environment, are responsible for a number of errors in the estimation of heritability, and can, under several circumstances, reduce the response to selection (see, e.g. Mather , 1955, and L e r n e r, 1958). Consequently, when quantitative characters are more or less controlled by genie interactions that deviate from simple additive effects, the phenotype may prove an unreliable indicator of the genotype. For instance, the dominance relations can only rarely be separated phenotypically. Moreover, one of the most important points is, to divide the phenotypic variance into its main component parts: the genotypic portion and the environmental fraction. As is well known, the magnitude of the nongenetic component is very large in forest tree populations, and particularly in uneven- aged forest and in forests growing under widely varying environmental conditions (see, e.g. Kiellander , 1956). Consequently, environmental influences must never be underestimated, but, at the same time, they are extremely difficult to assess and determine even in very well designed and conducted progeny trials in a natural environment. Despite the fact that the response to mass selection may vary in respect of different characters and in different tree species and populations, the forest tree populations contain a large reservoir, which is of additive genetic origin, and which will bring about improvement by selection. These variations in response occur because the relations between genotype and phenotype are weakened through complex environmental effects, and also on account of the weakening of the relations between the additive genetic fraction and the total genotypic portion of the phenotype due to non-additive gene interactions. Furthermore, natural selection has more or less efected the sorting out genotypes of forest tree species as cultivars, adapted to local ecological conditions, which are of great value to the breeder. Outbreeding species and populations always vary around the optimum, however, and, therefore, fitness can never be as high as in inbreeders. To summarize: 1) selection has led to great improvements in our domesticated animals and plants, 2) though selection cannot produce new genes, it can isolate cultivars or groups of individuals that are carriers of the desired |
| ŠUMARSKI LIST 1-2/1966 str. 34 <-- 34 --> PDF |
simultaneously. Selection is further complicated by negative genetic correlations between two or more characteristics. Hence, a system of points for the volume production of a plus tree at constant stand density, and for branching habit (with the possible exception of branch angle) is applied only as a guide, in order to determine (for each tree species and character, and within each REGRESSION LINE BASIC DENSITY ON ANNUAL RING WIDTH OSOOi Basic density Q/cm3 O^oa 112 Yo OL.00 0 i65 = 100 % 0 300 U mm Annual nnQ width Plus tree suQQcsted n ChccU trees from the same stand Fig. 6. provenance region) a level of rejection i.e. for the probable inferior half of the proposed plus trees (see publications on the method of independent culling levels, such as those by Smith, 1936, Hazel and Lush, 1942, Hazel, 1943, Rasmuson, 1964, and Stern and Hattemer, 1964). Probably a more reliable evaluation of each complex character, and primarily of the |
| ŠUMARSKI LIST 1-2/1966 str. 42 <-- 42 --> PDF |
mar samt klassificering av skogsfrö. (Directives for the inventory of seed stands and elite trees suitable for seed collection and classification of forest seeds.) — Stockholm. National board of private forestry, Sweden, (Kungl. Skogsstyrelsen) 1950: Anvisningar angaende frötäkt och handel med skogsodlingsmaterial. (Directions for seed collecting and trading in forest seed and plants.) — Stockholm. Nils son, B., 1956: Kvalitets- och produktionsförhallanden i ett klonförsök av tall. (The quallity and quantity production in a clone experiment of Scots pine.) — Sv. Skogsv. fören. Tidskr., 54:61—74. N i 1 s s o n, B., 1958: Om sambandet mellan moderträd och avkomma hos tall och gran. (On the relation between mother trees and their progenies in Scots pine and Norway spruce.) — Ibid. 56: 55—68. N y 1 i n d e r, P., 1958 a: Synpunkter pa produktionens kvalitet. (Studies on wood quality production.) — Skogen, 45: 100—102. N y 1 i n d e r, P., 1958 b: Synpunkter pa produktionens kvalitet II. (Studies on wood quality production II.) — Ibid. 45: 714—718. N y 1 i n d e r, P., 1959: Synpunkter pa produktionens kvalitet III. (Studies on wood quality production III.) — Ibid. 46: 54—57. Ply m Forshell , W., 1963: Genetics in forest practise in Sweden. — Unasylva 1964, 18: 119—129. Rasmuson , M.. 1964: Combined selection for two bristle characters in Drosophila. — Hereditas, 51: 231—256. Smith , H. F., 1936: A discriminant function for plant selection. — Ann. Eugen, 7: 240—250. Stern , K., 1960: Plusbäume und Samenplantagen. — Frankfurt a. M. Stern , K., 1961: Preliminary estimates of the genetic structure of two sympatric populations of birches as determined by random effects and natural selection. —. Proc. Ninth Northeast. For. Tree Impr. Conf., Syracuse, 25—31. Stern , K., 1963: Population genetics as a basis for selection. — Unasylva 1964, 18: 21—29. Stern , K., 1964: Herkunftsversuche für Zwecke der Forstpflanzenzüchtung, erläutert am Beispiel zweier Modellversuche. — Der Züchter, 34: 181—219. Stern, K. and Hattemer, H. H., 1964: Problems involved in some models of seleciton in forest tree breeding. — Silvae Genetica, 13: 27—32. Syrac h Larsen , C, 1947: Estimation of the genotype in forest trees. — Kg], Vet. — og Landbohöjskoles Arsskr. Copenhagen. T o d a, R., 1963: Mass selection and heritability studies in forest tree breeding. — FAO, Proc. World Cons. For. Gen. Tree Impr., I: 2a/2 i-iv, 1—7. Williams , W., 1964: Genetical principles and plant breeding. — Oxford. Zobel , B., 1963: Breeding for wood properties in forest trees. — Unasylva 1964, 18: 89—103. |
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D uf field, J. W., 1955: Selecting plus trees for our seed orchards. — Ind. For. Assoc, Oregon. Ehr en berg, C, Eklundh, 1963: Genetic variation in progeny tests of Scots pine (Pinus silvestris L.). — Stud. For. Suec, 10: 1—135. Ehrenberg, C, Gustafsso n, A., Plym Forshell, C, and Simak. M., 1955: Seed quality and the principles of forest genetics. — Hereditas, 41: 291—366. E r i c s o n, B., 1959: A mercury immersion method for determining the wood density of increment core sections. — Rapp. Avd. Skogsprod., Skogsforskn. inst., 1. Stockholm. E r i c s o n, B., 1960 a: Latewood percentage, density and volumetric shrinkage in wood of Picea abies (L.) Karst, f. virgata Jacq. A comparison with Picea abies. — Ibid. 2. Eric s on, B., 1960 b: Studies of the genetical wood density variation in Scots pine and Norway spruce. — Ibid. 4. E r i c s o n, B, 1961: Skogsträdsförädling med sikte pa ökat massautbyte. Nagra prelimmara forskningsresultat. (Forest tree breeding with a view to raising the yield of pulp. Some preliminary results.) — Medd. Skogsforskn. inst., Stockholm, Šer. Uppsatser, 81. Reprint from Tek. -Vetenskaplig Forskn., 32: 194—203. ^ Falconer , D. S., 1960: Quantitative genetics. — Edinburgh, London. Gustafss o n, A., 1949: Conifer seed plantations: their structure and genetical principles. — Proc. Ill World For. Cong., Helsingfors, 117—119. G u s t a f s s o n, A., 1962: Genetik och vaxtförädling i skogsbrukets tjänst. (Genetics and plant breeding as applied to Swedish forestry.) -— Sv. Skogsv. fören. Tidskr., 60: 111—150. (With an English summary.) Hazel, L. N., 1943: The genelic basis for constructing selection indexes. — Genetics, 28: 476—490. Hazel. L. N. and Lush, J. L., 1942: The efficiency of three methods of selection. — Jour. Hered., 33: 393—399. Hinkelmann , K., 1960: Kreuzungspläne zur Selektionszüchtung bei Waldbäumcn Silvae Genetica, 9: 121—133. Jensen , H., 1934: The establishment of forest tree seed orchards at Ramlösa 1941— 1954. — Acta Horti Gotoburgensis, 19: 157—192. J o h n s s o n, H., 1964. Forest tree breeding by selection. Clonal seed orchards — seedling seed orchards, progenj´ tests. — Silvae Genetica, 13: 41—49. John s son, H., 1965: Miljöns och genotypens inflytande pa tallens växtform i experimentell belysning. (Environmental and genetical influences on the growth form of Scots pine in experimental plantations.) — Foren. Skogsträdsförädl. Arsb., 1964, 115—125. Kemp thorn e, O. and Cur now, R. N., 1961: The partial diallel cross. — Biometrics, 17: 229—250. K i e 11 a n d e r, C. L., 1956: Über eine spättreibende Rasse von Picea Abies in Schweden und eine Schwierigkeit bei der Plusbaumauswahl. — Z. Forstgenetik 5181— 185. Lerner , I. M., 1958: The genetic basis of selection. — New York, London. Le Roy, H. L., 1960: Statistische Methoden der Populationsgenetik. — Basel, Stutt gart. Lindquist , B., 1948: Genetics in Swedish forestry practice — Stockholm. M a t h e r, K., 1955: Response to selection: Synthesis. — Cold Spring Harbor Symposia Quant Biol., 20: 158—165. Ma t thews , J. D., 1955: Tree seed orchards. — For. Comm. Res. Branch Paper, 18 London. Matthews , J. D., 1958: La selection et la classification des arbres en genetique forestiere. — Jour. For. Suisse, 8—9: 478—494. Matthews , J. D., 1963: Seed production and seed certification. — Unasylva, 1964, 18: 104—118. National board of private forestry, Sweden, (Kungl. Skogsstyrelsen) 1945: Anvisningar för inventering av för frötäkt lämpliga bestand och elitstam 39 |
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Volume Qua itv Total Tree ipecies Previous tree National Control card for plus trees score score score number number Province Parish Name of landowner FS ranger private forest district / ranger district Management unit Locality Latitude Longitude Elevation, m. Quantity of suitable scions-Quality of scions2 Method of stand establishment Seed investigations Grafted Cone production lncluced In clone tests at Included in seed orchard at Check trees The plus Age at breast height tree No 1 No 2 No 3 No 4 Mean Height actual´ Height at the age of the Volume factors plus tree DBH o.b. in mm. actual Double bark thickness in mm. DBH u.b. in mm. actual DBH u.b. in mm. at the age of the plus tree 1Height to crown Volume dm3 u.b. V, V, Volume score (-.,´ — 1) 10 Tree selected by Percent Cheek trees The plus from baise Quality factors of Crown No ´ | No 2 NO 3 ] No 4 Mean tree Circumference in mm. Circumference in mm. 1 Circumference in mm. upper d´iam. Crown radius1 Crown radius1 Length of branches´ 75 Length of branches1 50 Branch angle degrees 75 Branch angle degrees 50 Branch thickness in mm. 75 Branch thickness in mm. 50 No. of branches per whorl 75 No. of branches per whorl Height to the first dead branch1 Height of plate bark1 Crown shape Basic density Seed yield and seed quality Quality score Notes: — i Measured in meters to one decimal place. - Is very poor; 2, poor; 3, fair; 4, good; 5, very good. Miscellaneous information: Composition of stand: percent pine, percent spruce, percent birch, stocking; ground vegetation. Phenotype checked The Co-ordination Committee for Forest Tree Breeding and Genetics Signed: Control card for plus trees included in seed orchard and clone tests. Fig. 8. |
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Total Cub. Qual. Tree Previous National Control card for plus trees certif. selected selected species tree number certif. certif. number Province Pai´ish Name of landowner F3 ranger private forest Ad´dress of landowner district ranger district Management unit Locality Latitude Longitude Elevation, m. Quantity of suitable scions2 Quality of scions2 Method of stand establishment Seed investigations Grafted Cone production Included in clone tests at Included in progeny tests at Check trees The selected tree No 1 No 3 Age at breast height Height actual1 Height at the age of the selected tree´ DBH o.b. in mm. actual Double bark thickness in mm. DBH u b. in nam. actual DBIT u.b. in mm. at the age of the selected tree Height to crown1 Branch thickness2 Tree selected by Reason for selection Crown shape Branch angle degree Type of branching (spruce) (average of whorls 3 and 4) Stem form Basic density score Clearing ability stocking Notes: — * Measured in meters to one decimal place. 2 i, very poor; 2,poor; 3, fair; 4, good; 5, very good. 3 i; very fine branches; 2, fine branches; 3, moderately fine branches; 4, normal branches; 5, moderately coarse branches; 6, coarse branches; 7, very coarse branches. Miscellaneous information: Composition of stand1: percent pine, percent spruce, percent birch, ground vegetation. Phenotype controlled The Co-ordination Committee for Forest Tree Breeding and Genetics Signed: Fig. 7. |
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expensive and requires large areas, and consequently, it is applied in Sweden only in one or two seed orchards of each tree species. However, it enables, experimental results for a complete diallel crossing pattern to be compared subsequently with the corresponding results from different partial diallel mating designs (see Hinkelmann, 1960, Kempthorne and C u r n o w, 1961, and Ster n 1964 among other authors). When choosing crossing systems and experimental field designs for the partitioning of the genetic variance in each progeny test, the plus tree composition of the orchards must be considered, i.e. whether the clones represent different populations, provenances or even different species (see Stern , 1964). Several partial diallel mating desingns, where n clones are crossed with m testers, have been applied in Sweden. On the other hand, hitherto we have not used mating designs such as top cross, where all the clones included in a seed orchard are crossed with a common tester, and polycross, where all clones are crossed with a mixture of pollens from a number of clones. Until now, a design with four male parent trees or common testers has been employed in a set of seed orchards. In this, all the remaining n-4 clones are crossed with the four selected testers. The test trees are crossed in turn with four either clones. In other cases, either K e m p- thorn e and Curnow´ s (1961) mating design, or other partial diallel cross systems have been tried out; these enable, inter alia, analyses of the general and specific combining efects of the plus trees to be made, both within and between populations and provenances, when combined with useful and higly efficient experimental field designs. The degree of combining ability of the plus trees is, naturally, of extreme importance for the composition of polyclonal seed orchards (which must be based on cross-pollination of the clones with high general combining ability), and for the composition of biclonal seed orchards (which, in turn, must be based on crosses between two very richly flowering clones with high specific combining ability). In. addition, these two clones must flower at the same time, and preferably show self-incompatibility. Scaling of the plus and the check trees is done in accordance with specially prepared instructions. In addition to the prescribed scaling and collection of increment cores, reports are made on stand history, stand density, ground vegetation, mixture of tree species, growing area of the plus trees in m~. topography, and soil type. Moreover, in phenotype control the following data are recorded: the number of stumps near to the plus and check frees, the diameter of the twickest stumps in relation to mean diameter, at stump height, of the thickest standing trees, and the occurence and size of open spaces or gaps in the stand near to the plus and check trees. Fig. 7 and 8 show the registration of plus trees. Fig. 7 show a control card used for all selected trees; and Fig. 8 a control card for plus trees included in many seed orchards and clone tests. CHOICE OF STANDS FOR PLUS TREES SELECTION Many theoretical and practical problems arise in connection with plus tree selection. One important question is, which types of stand should we choose for our plus tree selection? and: Is the selection effect or the selection gain affected to a significant extent, if these stands are sparsely stocked, normally stocked, well stocked, or overstocked? The answer to these questions must |
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whole complex of characters, could be made by means of covariance and multivariate analyses of phenotypical data collected from plus trees and from a number of surrounding or adjacent sample trees, especially if the relative economic value of each character was known, and the economic weights of all traits were taken into account. A further step towards improving the selection effect and there by the gain of selection, would be to construct indexes (of the typo suggested by Smith, 1936, Hazel and Lush, 1942, and Hazel, 1943) for a number of base populations of each species. For the compilation of such indexes the following data must also be known: Heritabilty (narrow sense) of each tree character as well as, the genetic correlations between these characters in different selection models (see Ster n and Hattemer , 1964), and under different environmental conditions (see, e.g. T o d a, 1963, Le Roy, 1960, Stern, 1961 and 1963, and Zobel, 1963). There is no doubt that selection indexes of this type are needed (cf. Ander s son, 1963 and 1965, Ply m Forshell , 1963); but as long as information is lacking on the requisite genetic parameters of the populations, and on the relative economic values of the characters to be selected, it is not possible to construct the type of seelction indexes, for e.g. Scots pine and Norway spruce, which has been described by, e.g. Smit h (1936), and Haze l (1943). Theoretically, the selection index method is more effective than the method of independent culling levels; but in Drosophil a it has been found that the reverse order of merit may occur for index selection and independent culling, when the characters are controlled by pleiotropic genes (see Rasmuson , 1964). If, phenotype control has been hitherto, the primary control of plus trees, then clone tests (see Syrac h Larsen , 1947) and one-parent progeny tests are other forms of the control of single trees. In the Swedish programme for testing plus trees, such experiments have been carried out also on both conifers and decidous trees. The clonal trials have been made for various purposes: 1) to obtam useful preliminary information on trees that have either been included in seed orchards already, or have not, i.e. information on stem straightness, stem form, growth rate, branch habit, resistance to diseases of a parasitic nature, variations in technical properties of wood, hardiness, and relations between the phenotype of original trees and the corresponding clones; 2) to study the interactions between clones and different environments in different localities, e.g. in respect of varying quantities of fertilizer; and to study the relations between spacing and the quality development of the clones, and between spacing and clonal flowering; 3) to study intensity of clonal flowering, flowering time, seed production and seed quality in different environments (e.g. in north, central, and south Sweden); 4) to study the influence of various root-stocks on the flowering and growth of the clones; 5) to study the development of primary grafts in relation to secondary grafts; and 6) to study the development and flowering of the grafts when scions have been taken from different parts of the tree crown. The one-parent tests are of some interest for studying general combining ability, variation in quality factors and parasitic attacks, ect, within a population, and especially when the plus trees are pollinated by a large number of trees; but these tests are far from being accurate. The most important control of plus trees must occur in controlled progeny tests. This method involves artificial crossing. The ideal case is that, when all clones in a seed orchards are crossed diallelly. The method, however, is very |
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is applied. This represents a yield of 50 per cent of the dry weight of the wood. For example, with an export price of 600 Swedish crowns per ton of pulp, we can estimate the value of the wood in one case at 96 crowns, and in the other HEIGHT CURVE FOR PLUS TREES OF SCOTS PINE INCLUDED IN THE SEED ORCHARD Na1 IN NORTHERN SWEDEN. 2^1 Mean height of the plus and check trees in m. 23 22 21 20 19 18 / s 17-I 16 15-1 14 13-1 12 11 PLUS TREES 10 CHECK TREES y,´/ ^ 80 120 160 200 240 280 yea rs The age of the plus and check trees at breast height. Fig. 3. |
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1958 a and b and 1959). A genotypic variation in, among other things, branch thickness and branch angle, and in the number of branches per whorl in clones of Scots pine, has been demonstrated by Nylsso n (1956), and in branch angle and growth rate, by Arnborg and Hadders (1957). Points are assigned also for the number of branches per whorl. This character seems to Tabic 2 CLASSES USf.D HHI KtLATIVE BASIC WOOD DENSITY´ Density class Score Percent Extremely high 115.5 . 1« Very high 107. 5-111.´« a.i Hleh io% 5-107.U . i Ave rage 96.5-103.<« 0 Low 92. 5-96.1« -i Very low 88. 5-92.1« -2.5 Extremely low 88.1« - I« 1 Relative basic wood density =s density observed for »lus trees In oer cent of density calculated on the basis Bf mean annual ring´ width tor « number of sample trees of the same trep species at the same latitude anil altitude. be dependent on genetic factors to a higher degree than is the thickness of the branches. With regard to branch angles (see Table 1) in Scots pine, the heritability values, for this character in ten-year-old progenies, which were estimated in two field experiments (Eklundh Ehrenberg, 1963) in Sweden, varied between 14 and 96 per cent. There are, however, wide variations in heritability estimates of this character between experiments and even between branch whorls. Johnsso n (1965) has shown in clonal experiments on Scots pine in various environments, that the branch angle is quite strictly controlled genetically. He even found that the genotype »is the sole determinant of the branch angle«. »The proposed plus trees of Scots pine and Norway spruce were investigated, as previously stated, with regard to basic density, which gives the dry substance content of the wood in g per cm3 or in kg per m3 of raw wood. The basic density varies within wide limits. In the stand, the standard deviation for the trees is between 7—8 per cent. The mean standard deviation for Scots pine and Norway spruce for the whole Sweden is about 10 per cent of the mean basic density (see Eriscon , 1961, Table 2). In one and the same stand we can find, in certain cases, one stem with a mean basic density of 320 kg/m:!f, and another stem with a basic density of 480 kg/m3f, when the mean basic density of the stems in the stand is 400: kg/m3f. From the wood of the stem first mentioned we can obtain 160 kg dry pulp per m3f of raw wood; from the other stem the corresponding figure is 240 kg when the same cocking process |
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By check trees are meant the four largest dominant trees of the same species and age as that of the plus trees, which have grown under apparently similar ecological conditions in the neighbourhood of the plus tree, (usually up to a distance of 25—50 m or more from the plus tree). In stands of uneven age, these differences in age between the plus trees and the check trees exceeded 10 years only in exceptional cases. Only healthy trees and those free from stem defects have been approved as plus trees. In accordance with a proposal by Dr. Börje Häggström of the State Forest Service, Sweden, a point scoring system is used for evaluating plus trees with regard to volume production (including the influence of stem form on volume), and branching habit (see Table 1). A similar point scoring system as that used for branch thickness has been applied for basic wood density (see Table 2). The volume is estimated under bark. The volume of the check trees is adjusted to the stage of development corresponding to the age of the plus trees. The volume score is obtained from the ratio of the volume of the plus trees to the mean volume of the check trees. Every tenth part in excess of the value 1.0 is counted as one volume point. Growth in both height and diameter are greatly dependent upon environment. In relation to one another, however, growth in diameter is still more dependent upon environment than is growth in height (see, e.g. N i 1 s so n, 1958). Therefore, when selecting plus tree, there is good reason for putting a premium on the highest trees with the stem form, at least when the volume production of the plus trees is the same (see Fig. 3—5). Tabic . CLASSES USED »´UH ORANCH THICKNESS AWD DKANCH ANGLE Branch thickness Branch angle Class Score Class Score Very thick branches - ´I 50° -2 Thick branches - 2.5 50 to 60° - 1 Moderately thick branches -I 60 to 70° 0 Normal branches 0 70 to 80° « 1 Moderately thin branches « t 80 to 90° . 2 Thin branches 2.5 Very thin branches . k 1 Used for Scots pine only. NOTE: The score is reduced by I or 2 points if the nuuHx-r of branches per whorl Is abnormally large. The scores for branch habit (see Table 1) are recorded when inspecting the trees during the phenotype control. The branch thickness is assessed in relation to the age of the trees, the stem diameter, the length of branches, and the needle mass of the tree, as well as variation in stand density and site quality. This relations between these characteristics are very complex (see Nylinder , 26 |
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In the inventories, trees were selected as plus trees of Scots pine and Norway spruce, which, in a strikingly positive way, diverged from so-called check trees in a number of important characters (such as basic wood density, growth rate, stem form and branch habit) and from the average of the stand. NATIONAL BOUNDARY COUNTY tumenum — — 0Lß«LL Of lATtTVOE TREt-UMIT — — 300M.»». ÄA-t ZO*« BCUNCWSIY — » yr s * * * sve. NOVEMBER w Fig. 2. |
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spruce seed. In this part of the country, with regard to Scots pine, and especially to Norway spruce, there are long intervals between good flowering years, and still longer intervals between the years when the seed ripens. SEED ORCHARD ZONES /*_* FOR PINE l^^mm WW1 ?S®4v«Ä ´W&ZWK w&JT&t* ft ft ft -MX MöRtE * uTitw S35Nt BOUNÖA&Y300M. AS. SCA-i. S »M . A8.5EA-L S.V.6. 23.IV 19«0 Fig. 1. |
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genes, and 3) selection can be effective in changing the genetic constitution of a population or of a group of individuals, if the genetic differences of the group arc expressed in phenotypes. CONTROL AND REGISTRATION OF PLUS TREES In Sweden, during recent decades the supply of forest tree seed has been especially actualized (see, e.g. two publications by the National Board of Private Forestry, 1945 and 1950, L i n d q u i s t, 1948, Jensen, 1954, A r n b o r g, 1960, Arnborg & Johnsson, 1963, and Plym Forshell, 1963). Knowledge of the biological aspects of heredity has increased. There is general agreement that, from the point of view of heredity the best possible seed material should be used for forest reproduction. Consequently, a national programme for the production of forest seed in plantations has been worked out (Johnsson , Andersson and Stefansson, 1950, and Andersson, 1958 and 1960). The country has been divided into 16 zones — or climate area (Fig. 1) for Scots pine, and 10 for Norway spruce (Fig. 2). For each climate area, forest seed will be produced by tree species in specially laid out clonal seed orchards and, in certain cases in north Sweden, in seedling seed orchards (Andersson , 1965). As a rule, each polyclonal seed orchard contains 30 to 60 plus trees, which are vegetatively propagated by grafting. Great demands are made in respect of these plus trees. They must be markedly superior to other comparable trees in the stand in question, with regard to a number of valuable characters from an economic point of view, such as: resistance to diseases and unfavourable environmental factors, wood quality, growth rate, stem form, branching habit, good seed production capacity, and high seed germination ability, especially at altitudes above 300 m in northern Sweden (see, e.g. Andersson , 1948, 1958, 1960, 1962, and 1963, Lind qui s t, 1948, Ericson, 1959. 1960 a and b, and 1961, and B j ö r k m a n, 1963). In order, among other things, to obtain the requisite material for breeding and plantation work intensive and comprehensive selection has been carried out for several years and is being continued in certain regions or provenance areas. The plus trees selected are carefully measured and assessed in respect of wood specific gravity, growth rate, stem form, and branch characters — a so-called phenotype control (see e.g. Plym Forshell , 1963). In this connection, all the selected trees in the entire country are assessed by the same person. The best phenotypic trees in each area are selected for direct or indirect inclusion (after evaluating the average value of the trees as female parent trees, when mated at random, by (one parent) progeny tests, or after observing the reaction of the genotypes by clonal tests) in different types of seed orchards (Gustafsso n, 1949, Stern, 1960, and Johnsson , 1964). The selected plus trees are registered centrally. Thus, the seed orchards can be regarded as a means of improving the material for seeding and planting through breeding, as well as an attempt to rationalize forest seed production. Both the genetical constitution of the seed (see, e.g. Eklund h Ehrenberg , 1963) and its physiological characters (Ehrenberg, Gustafsso n, Plym Forshell and Si mak 1955, and Gustafsson , 1962) can be improved by breeding. The question of seed is particularly precarious in the extremely high altitudes in the north of Sweden (Andersson , 1965). The unfavourable climatic conditions in these high altitudes has always made it more difficult to obtain Scots pine and Norway |
| ŠUMARSKI LIST 1-2/1966 str. 40 <-- 40 --> PDF |
za debljinu grana upotrebljava se i za ocjenu specifične težine drva (Tabela 2). Bodovanje volumena dobije se iz odnosa drvna masa plus stabla prema prosjeku drvne mase komparativnih stabala. Svaki deseti dio viška od 1.0 drvne mase stabla boduje se jednim bodom. Budući da na promjer debla više utječu faktori okoline nego visina stabla, kod odabiranja i ocjene daje se posebni prid na najviša stabla koja imaju najbolji oblik debla kada je produkcija mase plus stabala ista. (Slika 3—5). Debljina grana procjenjuje se u odnosu na starost stabla, promjer debla, dužinu grana, količinu iglica na stablu kao i na gustoću sastojine te bonitet staništa. Boduje se i broj grana u pršljenu koje obilježje je izgleda pod većom genetskom kontrolom nego debljina grana. U vezi s kutom insercije grana istraživanja su pokazala kod običnog bora da se vrijednost heritabilnosti kreće između 14 i 96 posto. Nominalna specifična težina drva običnog bora i obične smrče varira unutar širokih granica. Na osnovi toga dobitak na drvnoj tvari može biti i do 5C°/o. Kolebanja nominalne specifične težine uzrokovana su u velikoj mjeri promjenama faktora okoline. Izgleda da je najvažniji faktor okoline obrast sastojine koji se indirektno može mjeriti širinom godova. Slijedeći važan vanjski faktor ie temperatura. Slika 6 prikazuje izmjerene nominalne specifične težine predloženih plus stabala U pravilu odabiru se za plus stabla samo ona kojih odnosna nominalna specifična težina prelazi 100. Kod izbora plus stabala sve veća pažnja pridaje se kapacitetu produkcije sjemena i kvaliteti sjemena. Ocjena izvjesnih kompleksnih karakteristika ie teška i nesigurna, a to je naročito slučaj kada se odabiranje s obzirom na različita svojstva vrši istovremeno. Odabiranje je nadalje komplicirano uslijed negativnih genetskih korelacija između dvije ili više karakteristika. Otuda je sistem bodovania s obzirom na produkciju drvne mase i izgled grana primjenjivan samo kao putokaz kako bi se odredio stupnj odbacivanja. Možda se pouzdanija ocjena svakog kompleksnog svojstva, a primarno kao cjelina kompleksnih svojstava, može dobiti od kovarijance i multivarijantnih analiza fenotipskih podataka dobivenih od plus stabala te od izvjesnog broja susjednih stabala. Daljnji korak prema poboljšanju utjecaia selekcije i uspjehu selekcije je izrada indeksa za izvjestan broj osnovnih populacija unutar svake vrsto. Drugi način kontrole pojedinačnih stabala su klonski testovi i testovi jedan roditelj — potomstvo. Najvažnija kontrola plus stabala je testiranje potomstva. Kod izbora sastojina za selekciju plus stabala treba se koncentrirati na sjemenske sastojine ili na područja predviđena za proizvodnju sjemena koja se sastoje od plus sastojina i skoro plus sastojina kao i na sredniodobne sastojine koje su u odnosu na starost i stanište dobro razvijene te pokazuju naročito dobar vanjski izgled. Slike 7 i 8 prikazuju unošenje u popis plus stabala. REFERENCES A n d e r s s o n, E., 1948: The association of forest tree breeding. The branch station at Brunsberg, Sweden. — Sv. Papperstidn., 51:13—18, 33—37, and 61—63. Anderss o n, E. 1958: Den skogliga froodlingsverksamheten i Norrland. (The work with forest tree seed orchards in Norrland.) — Norrl. Skogsv. förb. Tidskr., 135—161. Ander s son, E., 1960: Fröplantager i skogsforukets tjänst. (Seed orchards in Swe dish forestry.) — K. Skogs- o. Lantbr Akad. Tidskr., 99:65—87. (With an Englisn summary.) Andersson , 1962: Die Fichtenzüchtung in Schweden. — Sv. Papperstidn, 65:44—55. Andersson , E., 1963: Seed stands and seed orchards in the breeding of conifers. — FAO, Proc. World Cons. For. Gen. Tree Impr., II: 8/1 i-vii, 1—18. Andersson , E., 1965: Cone and seed studies in Norway spruce (Picea abies) (LI Karst.). — Stud. For. Suec, 23:1—214, and Appendix Tables I — XL I. Arnborg , T., 1960: Tree breeding in Swedish forestry. — Stockholm. Arnborg , T. and H a d d e r s, G., 1957: Studies of some forestry qualities in clones of Pinus silvestris. — Acta Horti Gotoburgensis, XXI: 125—157. Arnborg, T. and Johnsson, H., 1963: The Swedish forest tree breeding association. — Uppsala. Bj ör km an, E., 1963: Breeding for resistance to disease in forest trees. — Unasylva 1964, 18: 71—81. :in |
| ŠUMARSKI LIST 1-2/1966 str. 39 <-- 39 --> PDF |
depend upon which tree characters, and on, how many traits we are simultaneosly selecting for. Plus trees — plus in respect of one or two desirable properties — can be found in any type of stand. If we wish to find uninfected trees in stands where infection is rife, we may perhaps have to seek out affected stands regardless of location, crown density, and site (see D u f f i e 1 d, 1955). If we desire to select plus trees which are plus, e.g. in growth rate and other characters influenced by competition, this selection can most readily be made in stands where the trees have the best opportunity of revealing their inherent constitution, i.e. in sparsely to normally stocked stands on good sites. The effect of competition is, quite naturally, particularly strong in overstocked stands. Consequently, because of competition, the expected gain from plus tree selection, can either be low or quite insignificant in even-aged stands also. In addition to these aspects of the choise of stands, plus tree selection should be concentrated on seed stands or seed production areas (see Matthews , 1955, 1958 and 1963) which consist of plus stands and almost plus stands, and on middle-aged stands which, in relation to age, site and climatic conditions, are well-developed and show particularly good morphological features. KRATKI SADRŽAJ SELEKCIJA PLUS STABALA U ŠVEDSKOJ Cilj oplemenjivanja šumskog drveća je identificiranje i umjetna proizvodnja superiornih genotipova šumskog drveća za praktično korišćenje u šumarstvu. Umjetna selekcija ima specijalnu svrhu da odabere osnovni materijal za sjemenske plantažo te za dalju selekciju i oplemenjivanje ili za sabiranje odnosno uzgoj reproduktivnog materijala. Selekcijska dobit ;e produkt selekcijskog diferencijala i aditivnog dijela totalne genetske varijabilnosti u odnosu na fenotipsku varijabilnost. Važno je da se fenotipska varijabdnost rastavi na njezine glavne komponente: genotipsku komponentu i komponentu okoline. Populacije šumskog drveća i pored drugih faktora predstavljaju i veliki rezervoar aditivnih genetskih faktora koji će donijeti poboljšanje putem selekcije. Na osnovi toga zaključuje se: 1. selekcija je dovela do velikog poboljšanja naših domaćih životinja i biljaka; 2. putem selekcije ne mogu se proizvesti novi geni, već se mogu izolirati kultivari ili grupe individua koji su nosioci željenih gena; 3. seickcija može biti uspješna ako mijenjamo genetsku konstituciju populacije ili grupe individua tako da su genetske razlike grupe izražene fenotipski. Švedska je podijeljena u IG zona ili klimatskih područja (SI. 1) za obični bor, a u 10 područja za običnu smrču (SI. 2). Za svako klimatsko područje šumsko sjeme će se proizvoditi putem klonskih sjemenskih plantaža, a u nekim slučajevima na sjeveru Švedske putem sjemenskih plataža uzgojenih iz sjemena. Veliki se zahtjevi postavliaju na plus stabla. Ona moraju biti superiornija od drugih komparativnih stabala u sastojini i to u odnosu na brojne važne ekonomske osobine kao što su: otpornost na bolesti i nepoželjne faktore okoline, kvalitet drveta, brzinu rasta, oblik debla, izgled grana, dobru sposobnost plodonošenja i visoka klijavost sjemena naročito za sjeverna područja iznad 300 m nadmorske visine. Ocjenjivanje stabala vrši jedna osoba. Kod inventarizacije stabala selekcionirana plus siabla predstavljaju ona stabla koja u pozitivnom smislu odstupaju od komparativnih stabala u važnim karakteristikama, a isto tako i od prosjeka sastojine. Pod komparativnim stablima podrazumijevaju se 4 najveća dominantna stabla iste vrste i iste starosti kao i plus stablo koja rastu pod jednakim ekološkim uvjetima u susjedstvu plus stabla. U prebornim šumama razlika u starosti između plus stabala i komparativnih stabala prelazi 10 godina samo u iznimnim slučajevima. Za ocjenu produkcije mase i izgleda grana upotrebljava se sistem bodovanja (Tabela 1). Sličan sistem bodovanja kao |
| ŠUMARSKI LIST 1-2/1966 str. 33 <-- 33 --> PDF |
candidate« and from a number of check trees have been plotted, over the mean width of the annual rings of the wood samples. In this case, the proposed plus tree has a substantially higher basic density than the mean basic density for sample trees in the same habitats of given latitude and height above sea level; wood samples also indicate that the basic density of the plus tree is greater than the annual ring width would suggest. Measurement of the check trees has several purposes. These measurements, with those for the plus trees, form the basis for the calculation of the regression functions. In addition, they are a means of checking that the function is valid for the habitat in question; and they make it possible to determine whether the basic density of the proposed plus tree has changed, as a result of thinning, fertilization, and other changes in the environment of the stand, in the same way as that of the check trees. In order to make such a historical review possible, the wood samples, which are composed of cores, have been divided into sections consisting of ten annual rings, beginning from the outside. The mean width of the annual rings and the basic density are determined, for each section of the core, with the instrument described by E r i c s o n, 1959. The percentage ratio between the observed basic density, and that calculated by means of the regression function is termed the relative basic density (see Ericson , 1960 b and Fig. 6 in this report). The basic density has been determined for a number of plus trees and for grafts from these trees. Despite the fact that the grafts were grown under a different temperature climate than were the original trees, and that the mean width of their annual rings varied widely, the relative basic density of the original trees and grafts are in good agreement with each other, (see Ericson , I960 b, Fig. 7, 9, and 13). Consequently, we can expect a high degree of heritability in respect to relative basic density. Routine investigations of the basic density, of all the proposed plus trees are now carried out. The measurements are processed by means of a computer. As a rule only tree whose relative basic density exceeds 100, are approved as plus trees. Relative basic densities down to about 95 per cent are tolerated exceptionally, if in other important economic properties a tree is eminently superior to other plus trees. Several plus trees have already been found whose relative basic density is over 115; and what is perhaps equally important: several proposed plus trees with a relative basic density of 85 per cent or less have been detected and their inclusion in clonal seed orchards has been forbidden.« Another property of plus trees that has attracted more and more attention is their seed production capacity and seed quality. Climatic tolerance during the course of meiosis, seed setting, and seed development, is especially desirable in the extreme high altitudes of northern Sweden. Only a low per cent of the Norway spruce have, in these climatic regions, a good fitness or adaptability with regard to seed germination capacity and seed production. These properties vary widely. Consequently, the generative adaption of the trees to the climatic conditions of their habitats plays an important role in certain areas. Repeated observations on individual plus trees during a succession of seed years can furnish, useful information on characters such as seed quality, seed yield, and repeatability of these traits (see Anderss o n, 1965). The evaluation or assessment of certain complex characters is both difficult and uncertain, this is especially so, when several characters are being selected |
| ŠUMARSKI LIST 1-2/1966 str. 32 <-- 32 --> PDF |
from previous wood investigations, or on the basis of wood samples from a large number of proposed plus trees, together with chech trees which were to be assessed. The measured basic density of the wood from the »plus-tree HEIGHT CURVE FOR PLUS TREES OFNORWAY SPRUCE INCLUDED IN THE SEED ORCHARD Na52 IN SOUTHERN SWEDEN. 34i Mean height of the plus and check trees in m. 33 32 31 30H 29 28 27 26\ 25 24 23 22 21 PLUS TREES 20 CHECK TREES K´<_ //50 60 70 80 90 100 years The age of the plus and check trees at breast height. Fig. 5. |
| ŠUMARSKI LIST 1-2/1966 str. 31 <-- 31 --> PDF |
at 144 crowns per m3f of raw wocd. The diference of 48 crowns per m3f is only slightly reduced when felling and other costs are taken into account. Basic density plays an important role also in the quality of saw-logs. Moreover, the stand, which is to produce saw timber, yields pulpwood when it is young. Pulpwood is obtainded from the upper part of the stem of timber trees; and the waste from sawing is used in the production of pulp. Consequently, we must also consider the production of timber from the point of view of pulp. Variations in basic density are caused to a great extent by variations in environment; and these environmental differences can be considerable even in a small stand. The most important environmental factor seems to be stand density, a rough estimate of which can be obtained indirectly by measuring the width of the annual rings of the tree. The next most important environmental factor appears to be the temperature, which for Swedish habitats is quite well defined if the latitude and height above sea level of the site is known. Figure 6 shows how, in principle, the assessment of the basic density of the proposed plus trees is made. By means of regression function the mean basic density is calculated which can be expected for different widths of the annual ring in wood samples from habitats at a certain latitude and height above sea level. The regression functions have been calculated for material HEIGHT CURVE FOR PLUS TREES OF NORWAY SPRUCE INCLUDED IN THE SEED ORCHARD No31 IN CENTRAL SWEDEN 31 !Mean height of the plus and check trees in m. 30 29 28 27 26 25 24 23 22 21 PLUS TREES CHECK. TREES 20 X **´/ 80 90 100 110 120 130 W0 150 years The age of the plus and check trees at breast height. Fig. 4. |