PHYTOLITHS AND CUTICLES:
Cells of plant epidermis, either siliceous (phytoliths) or lignified (cuticles).
Developed at Colorado State Univ., Fort Collins, as range-management technique. Used
to determine the diet of livestock.
PALEOSCATOLOGY: has been used to study the diet of extinct animals through the dung
preserved in arid Southwestern saves (Hansen, 1978; Ackersten et al, 1988).
Methods: blender, screening
stomata: control gas exchange
trichomes (leaf hairs)
cork cells (provide leaf support)
silica cells (support, discourage foliavolres)
- Modern grazing animals in the lower Grand Canyon (cattle, burrows, bighorn sheep)
have diets similar to that of the extinct ground sloth (Long, Hansen and Martin, 1974)
- Extinct mammoths depended heavily on wet-ground grasses for their diet, based
on cuticle analysis by Terry Foppe (unpubl.) of the dung preserved in Bechan Cave
in Glen Canyon.
PHYTOLITH ASSEMBLAGE = f(P,D,R,I)
Silica is deposited in the secondary plant wall of some plants, particularly grasses and
occasionally in wood. Phytoliths most abundant in grasslands and steppes.
large fragments move short distances (fragile)
small fragments (silt sized) may be distributed by wind.
Resistant to oxidation, but the silica can be dissolved by ground-water movement
Many plants don't produce phytoliths: only a partial indication of plants in area
Non-related species produce the same types : "dumbbells, saddles, bowls, boats, bottoms"
Some Taxonomic categories can be recognized: panicoid, festucoid, chloroid
A few forms are diagnostic to species level: e.g., maize
- oxidize sample (boil in H2O2)
- wet sieve (phytoliths silt size)
- flotation (tetrabromoethane, ZnBr2) phytoliths have specific gravity of 1.5-2.3, quartz 2.65
- Thick accumulations of ash in an iron-age archeol. site -- abundant wheat phytoliths.
Liebowitz and Folk (1980) believe that straw was used to produce fires intense
enough to smelt iron.
- Relative amounts of festucoid (C3, cold-indicating) vs. panicoid (C4, warm-loving) grasses
in loesses indicate progressive development of midwest grassland (Carbone, 1977).
- High phytolith concentration during cold periods in deep-sea cores of the mid-Atlantic
indicate grassland vs. woodland, increased aridity in the northern Africa. (Parmente and Folger, 1974)
- Phytoliths of wet-ground grasses are larger, increased abundance in loesses could
indicate greater moisture (Yeck, 1969).
- Unique phytoliths (cross-bodies) indicate 4450 yr B.P. corn cultivation in Ecuador
- Does NOT reflect vegetation patterns in Mediterranean (Bremond et al., 2004)
- Radiocarbon dating of (carbon contained in) phytoliths (Piperno and Stothert, 2003)