Biological proxies

Biological proxies

Plants as indicators of terrestrial environments

Tissue/organs:Support --> wood (tree rings)

Photosynthetic --> leaf anatomy (stomata)

Reproductive --> pollen, (cones) seeds

Detritus --> charcoal

Dendroclimatology:basics

• Plants are responsive to variations in the ambient physical environment;

• Response is expressed by variations in growth, reproductive effort, etc.;

• Growth response is recorded in woody (nontropical) trees by variations in the thickness of annual rings;

• The environmental stimuli can be revealed by analyzing ring widths of living or fossil trees from sensitive sites.

Environment - site interactions

temperature-sensitive

annual ringsbark

drought-sensitive

complacent

Tree rings as proxies

Measuringtree ringwidths

Tree ring records, N. Eurasia (AD 0 - 2000)

Spatial patterns:

the megadrought of 1863 in

the USA

Reconstructing fire history from scars

and wounds

Fire history sites, SW USA

Constructing regional

fire histories

Tree rings and volcanismdust veil

‘frost ring’

e.g. LaMarche and Hirschboeck, 1984, Nature 307, 121-126

narrow/frost rings recorderuptions in spring/summer only?

Hemispheric analysesof tree ring density reveal

annual and spatial variations in climate

[Northern hemisphere; AD 1815-1817]

“The year without a summer”

Eruption ofTambora continues

Palynology: pollen proxies

• Plants produce morphologically distinctive pollen grains.

• Pollen “rain” is representative of the local plant community (apart from non-anemophilous spp.).

• Pollen grains are extremely resistant to decay in anoxic conditions (e.g. lake sediments, peat bogs, wetland soils).

• Pre-existing plant communities can be reconstructed by sampling fossil assemblages in these sedimentaryarchives.

• Palaeoclimates can be derived from the ecological ranges of the constituent species.

Pollen morphology I

Pollen morphology II

Pollen typesPinus

Tsuga

Poaceae

Achillea

Tsuga occidentalis range limits % isopolls

Species range, pollen rain and environment

-20 -10 0 10 20 30

Temperature (°C)

Ann.Jan.

July

Precipitation (mm)

Ann.Jan.

July

1 10 100 1000 10000

Relative pollen %

and summer

temperature (Yukon)

Pollen capture by lakes

EXTRA-LOCAL(20 TO SEVERAL

HUNDREDMETRES

FROM LAKE)

LOCAL(<20 METRES FROM LAKE)

0 100 200 300 1000

REGIONAL(UP TO SEVERAL HUNDREDKILOMETRES FROM LAKE)

LAKE DIAMETER (M)

% T

OTA

L P

OLLEN

100

0

Pollen representation (‘R-value’: Inuvik area)

“Over” “Equal” “Under”

alder 11.8 juniper 1.0 spruce 0.5sage 5.0 willow 0.6 larch 0.2grass 3.4 poplar 0.6 heaths 0.1birch 3.0sedge 2.2 R = 1;

pollen production =species abundance in vegetation

Pine pollen percentage vs. influx (Rogers Lake, Connecticut)

0

2000

4000

6000

8000

10000

12000

14000

Rad

iocarb

on

yrs

BP

% of total Influx (‘000 grains/cm2/yr)

0 20 40 60 0 10 20

L

ate

H

olo

cen

e G

lacia

l

Pine needles(regionalpattern)

Plant macrofossilsas proxies

Stomatal patterns

Monocots (linear) Dicots (random)

Stomatal density and [CO2]

Reconstructed atmospheric CO2

levels from 300 Ma to PD

Charcoal influx

(mm2 cm-2 yr-1), Lake

Francis, Abitibi, Québec

http://www.consecol.or

g/vol2/iss2/art6

Local fires

Regional fires(background)

Insect proxies (e.g. Coleoptera [beetles])

1. Fossil extraction (washing [solvents include kerosene] & sieving). 2. Taxon ID: morphology, microsculpture & genitalia (X100)

head capsule

pronotum

elytra(singular=

elytron)

Beetles in UK

“Devensian”

deposits (=OIS 2/3)

A-C = thermophil

es

D-G = tundra /alpines

H = cosmopolit

anspecies

(after Coope)

barren = full glacial

Modern ranges of cold-tolerant beetles from UK Devensian deposits

Modern ranges of thermophile beetles from UK Devensian deposits

Devensian exotica(periglacial deposits)

“interglacial refuge”

Terr

est

rial sh

elly

invert

ebra

tes

Terrestrial vertebrates

Alan Griffiths; discoverer of

fossil bear bones, QCI, from ~15 ka BP

(map of LateGlacial

vertebrate fossil finds)

Photos: Vancouver Sun

Packrat middens

Neotoma cinerea

fossil extractionsampling a midden

midden site (Colorado)

Packrat middens:sample

sites

(BC)

Pinus edulis:distribution records in US SW from packrat middens