POLLEN ANALYSIS - terminology

Transcription

1 Pollen Analysis

2 POLLEN ANALYSIS

3 POLLEN ANALYSIS - terminology Pollen (Linnaeus, 1751). The microgametophyte of seed plants, developed from the microspore. Spore. A general term for the usually microscopic, unicellular, asexual or sexual reproductive units of cryptogams and fungi. Pollen analysis (Von Post, 1916). The study of assemblages of dispersed palynomorphs such as those isolated from samples of peat.

4 POLLEN ANALYSIS - terminology Palynology (Hyde and Williams, 1944). The study of pollen grains and spores and of other biological materials that can be studied by means of palynological techniques. Aeropalynology. The study of palynomorphs found in the atmosphere. Melissopalynology. The study of pollen grains collected by bees, and/or found in honey.

5 POLLEN ANALYSIS - terminology Sporopollenin. The name given to the acetolysis resistant biopolymers which make up most of the material of the exine.

6 POLLEN ANALYSIS - principles Pollen and spores are produced by plants in abundance. Most of these fall to the ground Pollen and spores are preserved in anaerobic environments (lakes, bogs, ocean floor) Pollen and spores in the atmosphere are mixed resulting in uniform pollen rain over a given area

7 POLLEN ANALYSIS - principles The proportion of each pollen type in the pollen rain depends upon the abundance of the parent plant the dispersal properties of the pollen producing plant

8 POLLEN ANALYSIS - principles Pollen is identifiable at various taxonomic levels Example Poaceae Casuarina Pilgerodendron-type Stellaria undiff. Description Family id certain but lower categories indistinguishable Genus certain but lower categories indistinguishable One pollen type present, three or more plant taxa considered equally likely alternatives Genus id certain, one or more other morphological types within the genus distinguishable and treated separately.

9 POLLEN ANALYSIS - principles When a sample of pollen from sediment of a known age is examined, the result is an index of the vegetation surrounding the site of deposition at that point in space and time Pollen type Poaceae Casuarina Eucalyptus Eleocharis undiff. Total Sum Count %

10 POLLEN ANALYSIS - principles When pollen spectra are obtained from several samples through a sequence of sediment, they provide a picture of vegetation changes through the period of time represented by the sediment. Depth cm C ages (yr BP) Tibito? Olgaboli? PRIMARY FOREST SECONDARY FOREST GRASSLAND Nothofagus Castanopsis Ascarina Pandanus Trema Macaranga Casuarina Gramineae ± ± ±

11 POLLEN ANALYSIS - principles When two or more series of pollen spectra are obtained from several separate sediment sequences, it is possible to compare changes in vegetation through time at different places. Casuarina 2ka 2ka 1ka 1ka 0.6ka Baliem Telefomin h h hh h Tari Adoption of Casuarina agroforestry in highlands of New Guinea Age (10 yr B.P.) 2 0 Kainantu Nurenk

12 POLLEN ANALYSIS - methods Addition of exotic Conc. estimates (Lycopodium tablets) Hot acid (HCl).. 2. Removes calcareous fraction Hot Alkali + sieving.. 3. Removes humic acids Pyrophosphate.4. Deflocculant to remove clays Fine sieving..5. Remove particles smaller than pollen (<7µm) Gravity separation.. 6. Remove mineral fragments (density 1.88) HF 7. Removes silica and silicates Acetolysis 8. Removes polysaccharides (cellulose) Staining 9. Increases contract of sculpture on pollen Glycerol jelly Silicone oil Glycerol..10. Mounting medium

13 Pollen Morphology

14 POLLEN MORPHOLOGY Shape (3D) Glossary of Pollen and Spore Terminology [ Polar View Equatorial View Texture Echinate Reticulate

15 POLLEN MORPHOLOGY - terminology Pollen Colpus - An elongated, aperture with a length/breadth ratio greater than 2 Porate - A circular or elliptic aperture with a length/breadth ratio less than 2

16 POLLEN MORPHOLOGY - terminology Dicolpate, dicolporate, diporate Tricolpate, tricolporate, triporate

17 POLLEN MORPHOLOGY - terminology Syncolp(or)ate Bisaccate Tetrad Polyad

18 POLLEN MORPHOLOGY - terminology Spores Monolete Trilete The Australasian Pollen and Spore Atlas

19 Case Study

20 Pilgerodendron uviferum in southern Chile Pilgerodendron uviferum (D. Don) Florín, Ciprés de las Guaitecas Family: Cupressaceae Long-lived conifer (over 500 years) endemic to southern Chile and adjacent portions of Argentina Distribution ranges from 39 30' S to 55 30' S Chile SANTIAGO Argentina

21 Pilgerodendron uviferum in southern Chile Pilgerodendron uviferum (D. Don) Florín, Ciprés de las Guaitecas Found under a high precipitation regime on poorly drained and acidic soils

22 Lake Survey in the Chonos Archipelago Taitao Peninsula W 74 0 W 73 0 W Isla Guafo MELINKA 44 0 S 44 0 S Northern A + Melimoyu + F + I 45 0 S Chonos Archipelago + Mentolat Cay Maca PUERTO AGUIRRE 45 0 S Southern T + PUERTO AYSEN Hudson 46 0 S 46 0 S Taitao Peninsula Cabo Raper 47 0 S 76 0 W SURVEYED LAKES 75 0 W 74 0 W 73 0 W 47 0 S

23 Deglaciation in the Chonos Archipelago Taitao Peninsula 17ka 14ka 0-1% 2-5% 6-10% 11-20% 21+% Pilg. pollen %

24 Geographic and temporal extent of Pilgerodendron decline Age cal yr BP Trees & Shrubs Herbs Ferns Pilgerodendron (%) Pilgerodendron 2-1 (pollen grains/cm /yr ) 11-7ka 0-1% 1000 FACIL % % % % Pilg. pollen % 16000

25 Geographic and temporal extent of Pilgerodendron decline Age cal yr BP Trees & Shrubs STIBNITE Herbs Ferns Pilgerodendron (%) Pilgerodendron 2-1 (p ollen grains/cm /yr ) ka 0-1% 2-5% % % % Pilg. pollen %

26 What caused the Pilgerodendron uviferum decline? Hypotheses: 1. Interspecific competition 2. Individualistic response to climate change 3. Fire disturbance 4. Progressive changes in soil conditions 5. Impact of volcanic ash fall 6. Appearance of a pathogen Following methodological falsification approach of MacDonald (1993) Review of Palaeobotany and Palynology Vol. 79.

27 What caused the Pilgerodendron uviferum decline? Hypothesis 1: Interspecific competition Competition between established and invading plant species may have caused declines in individual species. Pollen influx data shows changes in dominance of other tree species are not associated with Pilgerodendron decline. Interspecific competition not the cause of Pilgerodendron decline. Noth Pilg Podo Wein Tepu Podo Tepu Wein Noth Pilg STIBNITE Years BP (x1000) FACIL Years BP (x1000) Pollen grains/cm 2 /yr Pollen grains/cm 2 /yr

28 What caused the Pilgerodendron uviferum decline? Hypothesis 2: Individualistic response to climate change Large scale aridity in early and late Holocene may have been unsuitable for Pilgerodendron survival. Age cal yr BP 1000 Trees & Shrubs FACIL Herbs Ferns Pilgerodendron uviferum-type Trees & Shrubs STIBNITE Herbs Ferns Pilgerodendron uviferum-type Chrononzones Antarctica Regional aridity not evident in early Holocene and regionally arid period between ~ cal BP predates Pilgerodendron decline. Climate change not cause of Pilgerodendron decline Holocene Younger Dryas Allerod Older Dryas Bolling ACR

29 What caused the Pilgerodendron uviferum decline? Hypothesis 3: Fire disturbance Fire associated with changes in climate variability or anthropogenic activity may have resulted in decline in Pilgerodendron. Age cal yr BP Pilgerodendron (%) Pilgerodendron (%) STIBNITE 4000 Changes in Pilgerodendron are not contemporaneous with changing charcoal concentrations FACIL Fire disturbance not the cause of Pilgerodendron decline

30 What caused the Pilgerodendron uviferum decline? Hypothesis 4: Progressive changes in soil conditions Changes in soil conditions associated with erosion or leaching may have resulted in Pilgerodendron decline STIBNITE Age cal yr BP Al (mg/g) Ti (mg/g) K (mg/g) Pilgerodendron (%) Geochemical analysis of allogenic elements in lake sediments shows that soil erosion decreased and soil waterlogging increased at the time of the Pilgerodendron decline Changes in soil conditions favourable to Pilgerodendron, therefore not responsible for decline

31 What caused the Pilgerodendron uviferum decline? Hypothesis 5: Impact of volcanic ash fall Impact of volcanic ash fall may have resulted in Pilgerodendron death. Age cal yr BP Pilgerodendron (%) Pilgerodendron 2-1 (p ollen grains/cm /yr ) Pilgerodendron (%) Pilgerodendron 2-1 (p ollen grains/cm /yr ) 1000 HW HW cal yr BP ash fall at occurs immediately before the decline in Pilgerodendron on the Taitao Peninsula. Other ash falls do not result in declines HW 5 HW 4 HW ash fall not exclusively the cause of Pilgerodendron decline HW 2 HW 1

32 What caused the Pilgerodendron uviferum decline? Hypothesis 6: Appearance of a pathogen Pathogens have been linked to sudden and rapid (<100 yr) decline in Hemlock (Tsuga) in North America and Elm (Ulmus) in Europe during the Holocene. There is a rapid ( yr) decrease in Pilgerodendron pollen influx in the late Holocene Taitao Peninsula but slower ( yr ) in the early Holocene Chonos Archipelago. Pathogen likely cause of late Holocene decline in the south but not clear in the early Holocene. Oprasa Facil Stibnite Six Minutes Six Minutes Stibnite Oprasa Facil Late Holocene decline Years BP (x1000) Early Holocene decline Years BP (x1000) Pollen grains/cm 2 /yr Pollen grains/cm 2 /yr

33 Conclusions Regionally, the pollen assemblages show no consistent response patterns to any one driver of the Pilgerodendron decline pathogen most likely cause. Pilgerodendron uviferum shows high sensitivity to environmental change and ability to re-establish after population crash forests still recovering from late Holcoene decline in Taitao Peninsula. Highlights difficulty in determining whether vegetation changes were caused by a combination of processes such as climate change, volcanic activity, or internal community dynamics.