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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.


ŠUMARSKI LIST 1-2/1966 str. 41     <-- 41 -->        PDF

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




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. 38     <-- 38 -->        PDF

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.




ŠUMARSKI LIST 1-2/1966 str. 37     <-- 37 -->        PDF

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.




ŠUMARSKI LIST 1-2/1966 str. 36     <-- 36 -->        PDF

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




ŠUMARSKI LIST 1-2/1966 str. 35     <-- 35 -->        PDF

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




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.




ŠUMARSKI LIST 1-2/1966 str. 30     <-- 30 -->        PDF

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.




ŠUMARSKI LIST 1-2/1966 str. 29     <-- 29 -->        PDF

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




ŠUMARSKI LIST 1-2/1966 str. 28     <-- 28 -->        PDF

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




ŠUMARSKI LIST 1-2/1966 str. 27     <-- 27 -->        PDF

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.




ŠUMARSKI LIST 1-2/1966 str. 26     <-- 26 -->        PDF

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.




ŠUMARSKI LIST 1-2/1966 str. 25     <-- 25 -->        PDF

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. 24     <-- 24 -->        PDF

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. 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.


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