Download This is an example of a short, informative title

Phytolith Analysis: Pits, Wells and associated Slumps from the Roman Town of Silchester
Sarah Elliott
Methodology
Introduction
Two detailed phytolith studies have been carried out by AFESS
(Archaeological, Forensic and Environmental Scientific Services) at the
University of Reading. The primary study was carried out on a series of
pits and slumps spanning both Period 1; c. AD 40/50-c.AD 70/80 and
Period 2; c.AD 70/80-c. AD 125/150 of Roman occupation. The second
study was carried out on an Iron Age well and its associated slumps.
Phytoliths survive and are stable in a pH range of 3-9 (Harvey and Fuller
2005). Phytoliths form within a plant in a number of different locations,
conforming to cell shape or intercellular spaces (Rovner 1983).
Phytoliths can be identified to specific parts of plants; stems, leaves or
husks. Differential parts are not represented from macro-botanical
remains. Identifying plant parts allow inferences to be made relating to
crop processing, particularly by identifying crop-processing waste
(Harvey and Fuller 2005). Phytolith deposition is archaeologically
important due to preservational properties and representation of plant
use/exploitation in the immediate area within a wide range of contexts
(Rovner 1983). Phytoliths make an important contribution to the
archaeological record because other plant remains often only survive
once charred. Monocotyledons (monocots) and dictoyledons (dicots)
can both be identified by their phytolith assemblages. Monocotyledons
are a group of plants, which include grasses, whose seed has the
embryo of one flowering leaf, whereas dictoyledons (woody types such
as shrubs and trees) have the embryos of two flowering leaves (Jenkins
and Rosen 2007). Any given species of grass produces a wide array of
morphologically distinct types (Rovner 1983).
Thirteen samples were taken from a range of four pits and slumps from
the Roman occupation and ten samples were taken at intervals
throughout Iron Age well [8328] and its associated slumps. The Iron
Age well was excavated after material had slumped into it for a number
of years. The well itself was sealed by the Roman road and possibly an
Iron Age structure. Five samples originate from the slumps lying on and
falling into the well, the other five samples are sampled from the layers
within the well shaft itself. Phytolith analysis was employed to examine
whether phytoliths survived in these contexts and to determine what
they could tell us about the paleoenvironment, the presence of cereals
and crop processing.
Photomicrographs
of conjoined
smooth long cells
from the stems and
leaves of
monocotyledons.
The key principle is to try to separate the phytoliths from the sand, silt ,
clay and organic matter. This is done following a protocol by Rosen
(1992). This involves sieving, carbonate removal, clay removal, organic
matter removal, phytolith separation and mounting . The slides would
then be ready for counting (minimum of 200 phytoliths per slide),
identification and quantification..
Photomicrograph showing Tritium (Wheat) husk
(below) and Photomicrographs showing Hordeum
(Barley) husk (right)
Key Results
Iron Age Well
All ten samples contained phytoliths from both monocotyledons and
dictoyledons although phytoliths produced by trees and shrubs were not
common in the assemblages. The landscape around the site would
therefore have contained both grasses and shrubs/trees. The trend
reflects a high dominance of monocot phytoliths representing over
ninety percent of the total assemblage in all samples. All ten samples
contain phytoliths from the leaves and stems of monocots, represented
both with single cells (smooth and sinuate long cells) and multi-cells
(conjoined smooth and sinuate long cells) in. All ten samples also
contain single celled phytoliths from the husks of monocots (dendritic
long cells).
Four of the ten samples contained husk multi-cells that can be positively
identified to genus level (Tritium, Hordeum, Avena, Aegilops and
Phragmites). Phytoliths produced by Cyperaceae were present in low
numbers in seven of the ten samples. All samples contained rondels
indicating the presence of pooid grasses, eight out of ten samples
contained bilobes while nine out of ten samples contained polylobes
both suggesting the presence of panicoid C4 grasses. The family
pooideae include cereal grains; Hordeum, Lolium, Avena and Tritium
(Twiss, 1992).
All ten samples contained some phytoliths which had darkened centres.
Some archaeologists argue that these darkened phytoliths (occluded
carbon) provide evidence of fire histories (Parr, 2006) and that direct
contact with fire induces darkening (charring) of phytoliths (Piperno,
1988, Kealhofer, 2003).
Roman Pits
Photomicrographs
of Husk multi-cells
from Tritium
(Wheat)
All samples have a dominance of monocots over dicots. Therefore the
samples were comprised of mostly phytoliths produced from grasses and
sedges. All of samples contain single celled phytoliths from the
leaves/stems (smooth and sinuate long cells) and the husks (dendritic
long cells) and the majority of the samples contained multi-cells from
both the leaves/stems and husks.
Ten of the thirteen samples contained multi-cells from cereals. The
samples contain wheat and barley. The two samples that definitely
contain both wheat and barley come from the same pit [8876]. Small
percentages of phytoliths from sedges were found in all of the samples
Two of the samples from the pits contained reeds although in very low
concentrations. The other samples do show some phytoliths that
compare favourably with phytoliths produced by reeds but these
samples are cot confirmed by the presence of reed multicelled
phytoliths. Nine of the thirteen samples contained darkened phytoliths
indicating some direct contact with fire.
Discussion
Iron Age Well
Overall, all samples exhibit a dominance of grasses (>90%) over shrubs
and trees (<10%). This indicates an open landscape mainly consisting of
grassland species. The presence of some phytoliths from woody taxa
(dicots) in all samples indicates that woodland vegetation may have
grown locally in the surrounding landscape during the Iron Age.
All samples contained more single and multi-celled phytoliths
originating from the leaves and stems of monocotyledons (grasses)
rather than from the husks. However, single cells from the husks are
present in all ten samples and eight of the ten samples contain multicelled phytoliths from the husks. All the samples that do contain
increased evidence for husk remains could represent samples which
contain evidence for crop processing. These samples contain large
amounts of leaf/stem cells which could be evidence of waste material
from crop processing. They also contain increased husk remains which
could be evidence for winnowing or de-husking the cereals (Harvey and
Fuller 2005). There are a number of phytoliths identified to genus level.
Some of these can provide us with information about the range of crops
present in the Iron Age, while others can provide information relating to
the surrounding Iron Age environment. Triticum, Hordeum and Avena
were all identified from multi-celled phytoliths. Cyperaceae and
Phragmites were present in some of the samples also. Both Cyperaceae
and Phragmites are associated with wetland environments. They can
grow in damp ground or standing water. Members of the Cyperaceae
family are often associated with poor soil conditions. Phragmites could be
used as building material such as thatching or as furnishings such as
mats, baskets and bedding. Aegilops was found in two of the samples.
Aegilops are often referred to as agricultural weeds or an agricultural
contaminant and are found growing alongside or amongst cereals,
specifically Tritium.
Rondels dominate the assemblage over bilobes and polylobes for all ten
samples. Different types of grasses can co-exist; one is usually dominant
over the other. A variety of local environmental conditions are indicated
by the presence of pooid and panicoid grasses in the phytolith
assemblage. Pooid grasses dominate the assemblage indicating the
presence of perhaps largely open, wet and moist conditions in the
surrounding environs with pockets of slightly drier ground, as indicated
by the presence of panicoid phytoliths.
Roman Pits
The assemblages from the Roman pits and associated slumps also
contained a dominance of monocots over dicots again indicating an
open landscape mainly consisting of grassland species. Woodland
vegetation may have grown locally in the surrounding landscape.
All samples contained leaves, stems and husks from grasses, indicating
possible on site processing and deposition. One sample (<3306>) has a
dominance of husks over stems/leaves (in both single and multi cells),
indicating the possible preferential selection of floral parts. Both pooid
and panicoid grasses would have been present in the surrounding
environment, this indicated by the short celled phytolith assemblage and
the small amounts of saddles indicates some chloridoid grasses.
One grass husk which was unidentifiable was unusual. Normally the short
cells in a multi-cell silicify first, and the dendritics silicify last (silicify=fully
form). This grass husk shows the dendritics to have silicified and the short
cells have not, indicating some possible change in environmental factors
(for example increased or decreased water).
Upper photomicrograph showing a
bilobe short celled phytolith and
Lower photomicrograph showing a
rondel short celled phytolith
Conclusions
Iron Age Well
This phytolith assessment demonstrates that the preservation of the
phytoliths from the Iron Age deposits in well [8328] is more than
sufficient to provide evidence for environmental proxies, crop
processing and cereal identification. The results indicate an
environment dominated by open grassland (monocotyledons) growing
in a moist and wet environmnet (C3 pooid grasses) with peripheral
woodland (dicotyledons). Reduced amounts of C4 panicoid grasses
were also present. Triticum (Wheat), Hordeum (barley), Avena (oat),
Phragmites (reeds), Cyperaceae (sedges) and Aeiglops (goatgrasses)
were identified from the ten samples. There is evidence for crop
processing from the differential plant parts found in many of the
contexts, the leaf/stem waste remains and the remains from winnowing
or the de-husking process. There is some evidence of burning from the
presence of occluded carbon phytoliths.
Roman Pits
The contexts sampled during period 1 and period 2 of Roman
occupation indicate a dominance of monocots (grasses and sedges)
over dicots (shrubs and trees). Ten of the samples contained the
presence of cereals identified by multicelled phytoliths, the cereals
present being wheat and barley. Other identifiable plants were sedges
and reeds, although the reeds were only present in low numbers. This
suggests a small area of wetland or standing water nearby where the
reeds were growing and possibly being used on site as a commodity
perhaps for bedding, basketry or fuel for a fire or hearth. The presence of
both pooid and panicoid grasses indicate the presence of cereals and an
assemblage of associated weeds. Many of the samples contain some
phytoliths which have come into contact with fire. This is apparent due
to their darkened centres. The most interesting feature is pit [8876],
which is a rubbish pit. It contains the highest amount of cereals, with
even proportions of leaf/stem cells to husk cells as well as the highest
amount of burning. Overall most samples have phytoliths from
stems/leaves and husks. This indicates that the whole plant is being
brought onto site for further crop processing.
References
1.
Ball, T.B., Gardner, J.S., Brotherson, J.D. 1996. Identifying phytoliths produced by the inflorescence bracts of three
species of wheat (Triticum monococcum L., T. dicoccon schrank., and T. aestivum L.) using computer-assisted image
and statistical analyses. Journal of Archaeological Science 23: 619–632
2.
Harvey, E.L and Fuller, D.Q. 2005. Investigating Crop Processing Using Phytolith Analysis: the Example of Rice and
Millets. Journal of Archaeological Science 32: 739-752.
3.
Rosen, A.M. 1992. Preliminary Identification of silica skeletons from Near Eastern Archaeological sites: An
anatomical approach , in G. Rapp and S.C. Mulholland (eds), Phytolith systematics: 129-147. New York: Plenum
Press
4.
Rosen, A.M. 1992. Preliminary Identification of Silica Skeletons from Near Eastern Archaeological Sites: An
Anatomical Approach, in G, Rapp (Jr) and S.C, Mulholland (eds), Phytolith Systematics. Emerging Issues: 129-147.
New York: Plenum Press.
5.
TWISS, P.G. 1992. Predicted World Distribution of C3 and C4 Grass Phytoliths, in G. Rapp (Jr) and S.C. Mulholland
(eds), Phytolith Systematics. Emerging Issues: 113-128. New York: Plenum Press.
Photomicrographs
showing burnt
phytoliths
6.
TWISS, P.C. 2001. A Curmudgeon’s view of grass phytolithology, in J.D. Meunier and F. Colin (eds.), Phytoliths:
Applications in Earth Sciences and Human History: 7-25. Lisse: A.A. Balkema Publishers.