Study site and design
Our study was situated at the Niagara College Teaching Vineyard, a
16.2-ha operational vineyard situated at the Daniel J. Patterson Campus
in Niagara-on-the-Lake, Ontario, Canada (43.1522° N, 79.1652° W). The
vineyard is situated in the Niagara-on-the-Lake Regional Appellation,
which is in turn nested within the Niagara Peninsula Appellation. Soils
at the site are classified as imperfectly drained silty clays (to 40-100
cm depth) over clay loam till mixed with poorly drained lacustrine heavy
clay. The farm is under commonly employed vineyard management systems,
which includes applications of calcium nitrate and/ or muriate of potash
and/ or sulphate of potash magnesium (K-Mag; 22-10.8-22), applied
uniformly across the farm in mid-June. Liquid calcium (8-0-0-10) is also
applied as a foliar spray early in each growing season. In mid- June of
each year cover crops are planted in every second row with 65% annual
rye, 20% crimson clover and 15% eco-till radish through deep ripping,
discing and harrowing passes. At the site there is 7.26-cm diameter tile
drainage installed in every other row, and the site is not irrigated.
Our study was conducted over a 1-week period between July
1st and 7th, 2021, when vines were
in the fruit setting/ berry development phenological stage (Coombe,
1995). We selected a total of 15 individual ‘Chardonnay’ vines (“Dijon
Clone 76”) for functional trait analyses, which were distributed evenly
across five different planting rows spaced 15-20 m apart (corresponding
to an even 10 interceding planting rows). These sampling rows run
parallel to one another, and broadly follow a soil compaction gradient
that runs along a northwest to southeast orientation in the vineyard.
This gradient is related to the vineyard’s imperfectly drained soils and
hydrology. Generally, northwest areas and planting rows are well drained
by mid- to late- May. By comparison, areas and planting rows in the
southeast remain poorly drained for roughly an additional month, drying
by mid- to late-June. Since farm machinery is required for foliar
applications and cover crop plantings across the entire vineyard in mid-
June, southeast areas of the vineyard therefore experience enhanced
mechanical compaction every year in early late Spring/ early summer.
Soil bulk density was collected for each sampled vine (described below)
to a 10 cm depth, using a 1 cm diameter core borer, and varied
significantly across rows (Analysis of Variance (ANOVA)F 4, 10=5.84, p <0.001), with rows
1 through 5 expressing bulk density values of 1.36±0.12 (S.D.) g
cm-3, 1.58±0.08 g cm-3, 1.67±0.09 g
cm-3, 1.64±0.1 g cm-3, and 1.72±0.1
g cm-3, respectively.
Within each sampling row, three individual vines situated 13-15 m away
from one another were chosen for leaf trait measurements. Each of the 15
vines chosen for our study, was between 1.5-2 cm in resprout diameter
and free of any pest, pathogen, or mechanical damage. On each plant, we
selected three recently developed and fully expanded leaves that were
free of any damage or disease, and situated on the upper-most cane in
full-sun conditions. This nested study design therefore resulted in leaf
traits being measured on 45 leaves from 15 individual vines that were of
the same size, age, rootstock and pruning regimes, which were in turn
situated within five distinct sample rows.