Download Delineation of breeding zones – Picea abies in Norway as an example

Delineation of breeding zones – Picea abies in Norway as an example
Tore Skrøppa
Norwegian Forest and Landscape institute
Background information
Norway spruce (Picea abies) is a young species in Norway and started its introduction into
the Norwegian landscape approximately 2500 years ago. Its present natural occurrence is in
south-eastern Norway from sea level and up to 1000 m, and in Central and North Norway,
north to lat. 67, at decreasing altitudes in the north. Outside this area the species has been
planted both in western Norway and north of its natural boundary in northern Norway.
Genetic information characterizing adaptation to the climatic conditions is available
from provenance, progeny and clonal trials. Measurements have in particular been made of
annual growth rhythm traits: the timing and duration of the annual growth period, frost
hardiness development in the autumn and dehardening in the spring, and the occurrence of
climatic damage under field conditions. All studies demonstrate a clinal variation in growth
rhythm traits in natural populations from the south to the north and from low to high altitudes.
The southern and lowland populations have the longest duration of the growth season, and as
a consequence, the highest growth potential. They also have the latest development of autumn
frost hardiness. The only well-known characterisations of the adaptive process of spruce
populations are the responses to temperature and photoperiod. Within natural populations, a
large genetic variation is present, also for traits that show clinal variation at the provenance
level and in populations at the geographic margin of the species. In addition, a number of
studies have shown that Norway spruce can adjust the performance in adaptive traits by a
rapid and likely epigenetic mechanism, through a kind of a long-term memory of temperature
sum and photoperiod during seed production.
Seed orchards were in the 1960s and 1970s established from plus-tree selections in
natural forests and are now being renewed with tested materials. Now selection and testing of
a second generation of parents has begun. In the revised breeding strategy the proposed
breeding objectives are to improve climatic adaptation, growth and quality, without
decreasing the genetic variation in future forests. The bred material should give a higher
survival and be possible to use over a larger area then material from natural stands. The bred
material should also be robust to future climatic changes. The increased growth should
contribute to mitigate the effect of CO2 from the atmosphere. Breeding should not decrease,
preferably increase, wood density, improve form stability and reduce the frequencies of
defects that cause reduced value production.
Earlier most reproductive material of Norway spruce was of the category source
indentified, collected in natural stands and characterized by its region of provenance (Figure
1). Transfers should not be made more than 200 km north or south and less than 300 m in
altitude.
Breeding and deployment zones
In a revised breeding strategy Norway is divided into eight breeding zones (Table 1) based on,
latitude, altitude, and known climatic gradients, both for administrative reasons and optimal
use of adapted reproductive materials from the seed orchards. Breeding efforts and objectives
differ between zones depending on whether there are specific issues in the wood production
that have to be focused and also on the importance of forestry in the region. In each zone the
breeding population is divided into one or more sub-populations each containing 50 unrelated
individuals. Breeding zone G0 will contain one sub-population with individuals selected from
more southern provenances adapted to climatic conditions corresponding to a 2º C increase in
mean annual temperature in deployment zone G2 and G4. The other zones will contain subpopulations with individuals from a limited geographic area within the zone. Hence, the
populations should then be adapted to the present climate in the zone, but may also be ranked
according to climatic gradients within the zone. They should provide the basic material for
reproductive material from seed orchards that could be used in a wide area, but also be
flexible for transfer if climate change. All individuals in the sub-populations should be tested
in progeny tests planted at several sites. The importance of traits in selection will vary among
zones, but will generally characterise annual growth rhythm, height growth and wood quality
traits. The timing of flushing in spring is a key trait in regions where spring frosts frequently
occur and early flushing will be avoided. The recommendations for the deployment of
reproductive material should be revised as more fields test information become available.
It is important to note that breeding and deployment zones are different and that there
can be several deployment zones within each breeding zone. The deployment zones are
defined by the adaptive properties of the seedlings from each seed orchard which have to be
tested. Their performance will to some extent be influenced by the seed orchard locality due
to both pollen contamination from surrounding forests and by epigenetic effects caused by the
climatic conditions at the seed orchard site.
Table 1. Breeding zones and regions of deployment for Norway spruce in Norway. In each
breeding zone there is one or more sub-populations each containing 50 unrelated individuals
from a limited geographic area within the zone.
Breeding zone
Region of deployment
Altitude
G0
Same as G1 and G4 with a 2º C
increase in mean annual temperature
Interior south-eastern Norway
Lat. 58º - 62º N
Interior south-eastern Norway
Lat. 58º - 62º N
Interior south-eastern Norway
Lat. 58º - 62 ºN
Western Norway
Lat. 58º - 62 ºN
Central and northern Norway
Lat. 62º - 66º30‘N
Central and northern Norway
Lat. 62º - 66º30‘ N
Northern Norway
Lat. 66º30’ - 70ºN
0 – 250 m
G1
G2
G3
G4
G5
G6
G7
Number of subpopulations
0 – 350 m
1
5
350 – 650 m
4
650 – 950 m
4
0 – 350 m
2
0 – 250 m
3
250 – 550 m
3
0 – 250 m
1
Figure 1. Map of Norway with the seven breeding zones G1 – G7 based on materials from
native Norway spruce populations. The breeding zone G0 is based on materials from more
southern provenances outside Norway. Each breeding zone contains several regions of
provenance or seed collection regions which are delineated by red border lines.