Method notes, Exp II, “Genes vs. Species”
Jason Fridley and Phil Grime, Fall-Winter 2004 plus Fall
2005 update
See also details in Excel Design Spreadsheet.
Planting
Eight genotypes were selected for each of eight species, derived from
planted material that had been continually propagated at
Genotypes were planted during a three-week period from mid-November to
early-December 2004 by JDF and JPG, one genotype at a time and one species at a
time. All individuals of Festuca were planted
first, followed by Koeleria, Helictotrichon,
Carex caryophyllea, C. flacca, C. panicea, Campanula,
and Succisa. Individuals were prepared by
splitting apart separate tussocks, potted genets, or spreading clumps (Succisa), and clipping above and belowground tissues to a
standard biomass within species (typically 6-8 cm above- and
belowground). Roots were wetted prior to planting. After planting,
boxes were kept constantly moist and warm by heating cables (thermostat set to
10 C) and overhead plasting sheeting (briefly) to
encourage root and shoot growth.
Sixty-four individuals were planted in each box in an equally spaced 8 x
8 grid. For the 8 species x 8 genotype treatment, planting positions were
determined randomly and each genotype was represented once in each box.
For the 8 spp/4 genotype and 4spp/8genotype treatments, each genotype was
planted twice and replicate compositions were planted on each side of the box
with respect to crevice location, but within a box side planting positions were
random. For the 6 other treatments, genotypes were represented by 4, 8,
16, 32, or 64 individuals and replicate compositions were planted in each
quadrant of the box, but randomly within quadrants.
Soils
All soils were removed from the field, nearby the Buxton Climate Change
Laboratory in Harpur Hill, Derbyshire. Two
locations were chosen to match the rendzina and podzol soil types occurring in or near the Cressbrookdale location. The more calcicolous
vegetation above the rendzina soil was chosen about
halfway down the slope of a limestone dale at Buxton, while the podzol (acid) soil was chosen from an area near the top of an
adjacent dale with more calcifuge vegetation (Vaccinium, Arrhenathrum?). Rendzina was removed (turf vegetation down to bedrock,
20-30 cm deep), placed in plastic bags on site, hauled up with a wench system
(acknowledgement: Andrew Askew!), and transported back to Tapton.
The soil was then dried a bit in greenhouses, mixed in a cement mixer and mixed
further by hand to remove major rocks, root tussocks and large rhizomes, but
was otherwise unamended (and was noticeably rich in
earthworms). Podzol was removed and treated in
much the same way but the immediate surface turf was not bagged (soil depth
40-50 cm); few macrofauna were apparent.
Crevice soil (see below) was filled with a separately-removed rendzina, from the same location as the fresh rendzina but removed and stored as living turves at Tapton for __ years
(8?). Turves were allowed to dry out before
soil was removed from roots with a pick, mixed in a wheelbarrow and placed down
the PVC pipes by hand.
Crevices were assembled on boxes with soil already present. To the
fill the box with soil, first the bottom 5 cm over the whole box was filled
with fresh rendzina. Boxes were filled all at
once with soil batches in aliquots. On top of this 5 cm rendzina layer, boxes were further filled with a 5 cm deep
checkerboard layout of fresh rendzina and podzol, separated with a cardboard divider (initially) to
facilitate sharp soil boundaries. The checkerboard layer divided each box
into 4 quadrants and each soil type went into diagonal patches; for each box,
the orientation of the patches with respect to the plot layout AND the crevice
location was randomly determined. Total soil depth (on non-crevice/rock
side) was 10 cm initially and settled to 8-9 cm.
Box construction
Boxes (experimental unit) were constructed from tannalized
timber with inner dimensions 55 x 55 x 12 cm. Slats over the bottom left
2 cm wide gaps and were covered with water permeable nylon mesh to facilitate
drainage. Box soil structure was varied by allowing each
Plot layout
Fifty-four boxes were arranged along two rows of scaffolding containing
6 randomized blocks of 9 treatments. Boxes were protected from herbivory and animal disturbance by mesh fencing.
[Treatments and box layout are detailed in excel sheet.]
Treatment Compositions
Species diversity treatments were chosen to be specific subsets of an
eight species mixture: all 8 species; Fo,
Km, Hp, Cc; and Festuca only. Festuca ovina is one of the most
widespread and abundant species in many types of British grassland including
the limestone grassland at Cressbrookdale, is highly
resistant to drought and grazing, and occurs on a wide range of soil
types. The other two species composition treatments represent increasing
complexity from the Festuca monoculture: first two
other very common tussock grasses and the clonal
sedge Cc, followed by common subdominant components at Cressbrookdale,
two forbs and two other sedges.
Genotypes of each of these species were chosen based on the 5-year
results of their performance in the synthesized communities of Booth and Grime
(2003). Chosen genotypes represented a gradient of high to low abundance
in 16-genotype treatments of the Booth and Grime experiment. In the case
of Cc and Cr, biotypes that were not verified as unique genotypes by Whitlock
were excluded. In the case of Succisa,
genotypes were chosen largely on the basis of available stock material.
In contrast to species composition, genotype composition for each
treatment was chosen randomly, with the following constraints:
|
Species |
Genotypes / sp |
How GD compositions
assembled |
|
1 |
1 |
Each of the 8 Festuca genotypes put in one box (here replication = 8) |
|
4 |
1 |
Randomly select 6 of the 8
genotypes of each species, then randomly seed each into a replicate |
|
8 |
1 |
Randomly select 6 of the 8
genotypes of each species, then randomly seed each into a replicate |
|
1 |
4 |
Each of the 8 genotypes of
Festuca represented 3 times over 6 reps, otherwise
random |
|
4 |
4 |
Each of the 8 genotypes of
4 species represented 3 times over 6 reps, otherwise random |
|
8 |
4 |
Each of the 8 genotypes of
8 species represented 3 times over 6 reps, otherwise random |
|
1 |
8 |
Exact replicates of
8-genotype mix (here only 4 replicates) |
|
4 |
8 |
Exact replicates of
8-genotype mix |
|
8 |
8 |
Exact replicates of
8-genotype mix |
Maintenance
27 May
5 Oct 05 15 dead individuals replaced,
including:
Campanula not replaced, due to difficulty
determining whether actually “dead”. Likely that most individuals will return in the spring.
First simulated grazing at
2.5 cm height applied on 13 July 2005, coinciding with Mark Bilton’s
third census and Chris Bennett and Elizabeth Richell’s
recording of reproductive and vegetative vigor with Fo. Second
clipping performed 28 Sept – Oct 4 2005.
All clippings saved for weighing by quadrant, and individuals of four
species (Hp, Km, Cp, Cf)
harvested by individual. Other four
species either have little biomass above cut (Sp, Cr, Cc) or have already been
measured once (Fo).