136
~100 potted seedlings from each stand. Once seedlings had entered their first
dormant period (June 15), their height (h 0 ) from the collar to the top of the most
distal bud of the main axis (A1) and their diameter (d 0 ) at the base of the most distal
bud were recorded. In the second year growing period, the cumulative length of the
main axis was measured, six times along 172 days, finishing when the plants had
reached asymptotic growth (December 12). With those data, individual growth
curves were fitted using a sigmoidal equation (Boltzmann model), and traits were
calculated as before t 10 , t 90 , Dur, and the maximum growth rate grmax (mm.day
−1
).
Budburst phenology of the main axis terminal bud (BB) was registered at the second
and third growing seasons (considering four phenophases). Day of the year until
phenophase 3 (at least one leaf is unfolded and spreading) was registered.
Architectural traits were recorded during the second growing period: dominance
(dom 1 ) of the main axis and delayed (dlb) and/or immediate (ilb) lateral branching
of second-order branches (A2). A whole-plant size and form characterization was
performed when plants were 6 years old, by obtaining the total height (h6), number
of co-dominant axes (nAx) (which was also used to calculate the dominance of the
main axis: (dom6)), length of the largest co-dominant axis (lAx), total number of
secondary branches (nA2br), and length of the largest branch (lBr) carried by the
largest co- dominant axis. With these measures, two continuous traits were
constructed: branchiness (Br = nA2br/(lAx)/10) and slenderness (Sl = lAx/(lBr/
nAx)). Together with h6, Br and Sl describe plant architecture within a continuum
from shrubby, multi-stemmed to slender, single-stem growth forms.
The majority of the variables of phenology, growth rhythm, and architecture
traits showed significantly different means between stands H and L. Although the
individual age-age correlations for height (h 0 , h 6 ) and dominance (dom 1 , dom 6 ) of
the main axis were not significant, the plants from stand H were on average consistently shorter and had lower dominance of the main axis. Besides, they had a later
budburst phenology and growth initiation, i.e., an average temporal lag of 6 days,
similar to the findings of Premoli et al. (2007), and were more branched and less
slender than plants from stand L.
From the whole-plant analysis, three archetypes representing the juvenile growth
form were retained: archetype 1 represents plants that were small and typically
formed by several (2 to 4) co-dominant axes, relatively dense in lateral branches. On
the other hand, archetype 3 reflects large single-stemmed, slender plants, with low
branchiness. Archetype 2 represents highly branched plants, which, although in
general had one main stem, was short (Fig. 5.6). The frequency of plants resembling
each archetype (according to their nearest Euclidean distance) was not independent
of the provenance stand. Within the group of plants from stand H, 74.5% were phenotypically closer to archetype 1, 15.5% to archetype 3, and 10% to archetype 2. In
stand L, the proportions of plants resembling archetypes 1 and 3 were similar
(48.7% and 50%), while those closer to archetype 2 were only 1.3%.
The juvenile growth habit of N. pumilio differed between the lower and higher
extremes of a 360 m elevation gradient. This should be attributed to genetic determination and not solely to plastic responses to varying environmental constraints
imposed by altitude. The significant temporal lag of ca. 6 days in budburst phenology
C. Soliani et al.
~100 potted seedlings from each stand. Once seedlings had entered their first
dormant period (June 15), their height (h 0 ) from the collar to the top of the most
distal bud of the main axis (A1) and their diameter (d 0 ) at the base of the most distal
bud were recorded. In the second year growing period, the cumulative length of the
main axis was measured, six times along 172 days, finishing when the plants had
reached asymptotic growth (December 12). With those data, individual growth
curves were fitted using a sigmoidal equation (Boltzmann model), and traits were
calculated as before t 10 , t 90 , Dur, and the maximum growth rate grmax (mm.day
−1
).
Budburst phenology of the main axis terminal bud (BB) was registered at the second
and third growing seasons (considering four phenophases). Day of the year until
phenophase 3 (at least one leaf is unfolded and spreading) was registered.
Architectural traits were recorded during the second growing period: dominance
(dom 1 ) of the main axis and delayed (dlb) and/or immediate (ilb) lateral branching
of second-order branches (A2). A whole-plant size and form characterization was
performed when plants were 6 years old, by obtaining the total height (h6), number
of co-dominant axes (nAx) (which was also used to calculate the dominance of the
main axis: (dom6)), length of the largest co-dominant axis (lAx), total number of
secondary branches (nA2br), and length of the largest branch (lBr) carried by the
largest co- dominant axis. With these measures, two continuous traits were
constructed: branchiness (Br = nA2br/(lAx)/10) and slenderness (Sl = lAx/(lBr/
nAx)). Together with h6, Br and Sl describe plant architecture within a continuum
from shrubby, multi-stemmed to slender, single-stem growth forms.
The majority of the variables of phenology, growth rhythm, and architecture
traits showed significantly different means between stands H and L. Although the
individual age-age correlations for height (h 0 , h 6 ) and dominance (dom 1 , dom 6 ) of
the main axis were not significant, the plants from stand H were on average consistently shorter and had lower dominance of the main axis. Besides, they had a later
budburst phenology and growth initiation, i.e., an average temporal lag of 6 days,
similar to the findings of Premoli et al. (2007), and were more branched and less
slender than plants from stand L.
From the whole-plant analysis, three archetypes representing the juvenile growth
form were retained: archetype 1 represents plants that were small and typically
formed by several (2 to 4) co-dominant axes, relatively dense in lateral branches. On
the other hand, archetype 3 reflects large single-stemmed, slender plants, with low
branchiness. Archetype 2 represents highly branched plants, which, although in
general had one main stem, was short (Fig. 5.6). The frequency of plants resembling
each archetype (according to their nearest Euclidean distance) was not independent
of the provenance stand. Within the group of plants from stand H, 74.5% were phenotypically closer to archetype 1, 15.5% to archetype 3, and 10% to archetype 2. In
stand L, the proportions of plants resembling archetypes 1 and 3 were similar
(48.7% and 50%), while those closer to archetype 2 were only 1.3%.
The juvenile growth habit of N. pumilio differed between the lower and higher
extremes of a 360 m elevation gradient. This should be attributed to genetic determination and not solely to plastic responses to varying environmental constraints
imposed by altitude. The significant temporal lag of ca. 6 days in budburst phenology
C. Soliani et al.