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Ecological Responses to Late-glacial Climate Changes in Northern and Western Norway

Ecological Responses to Late-glacial Climate Changes in Northern and Western Norway. Hilary H. Birks Steve Brooks Ingelinn Aarnes Maarten Blaauw. Bergen. London. Bergen. Belfast. INQUA 2011.

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Ecological Responses to Late-glacial Climate Changes in Northern and Western Norway

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  1. Ecological Responses to Late-glacial Climate Changes in Northern and Western Norway Hilary H. Birks Steve Brooks Ingelinn Aarnes Maarten Blaauw Bergen London Bergen Belfast INQUA 2011

  2. There were rapid climate changes in the late-glacial (Allerød and Younger Dryas) and in the early Holocene in western Norway • How do species and vegetation respond? Ecological processes • There is a small South-North climate gradient in Norway today; ameliorated by Gulf Stream • Did the gradient operate during the late-glacial and early Holocene? • Was the gradient different from that of today? • Howdid these differences affect vegetation development? Fact Fact • Temperature was reconstructed from fossil Chironomid data from same cores as the plant data. Independent climate record. • Use plant macrofossil concentration data; local dispersal and good taxonomic resolution give evidence of local vegetation. Concentrations are independent of each other. • Compare species and vegetation changes to temperature changes. Method

  3. Sites: south to north transect Northernmost birch woodland Jansvatnet Arctic tree-line 11.1oC 71oN 330 km Lusvatnet 11oC 69oN 890 km YD cirque Kråkenes Steep valley with cliffs at head. Sparse birch woodland 12.6oC 62oN

  4. Kråkenes 62oN macrofossil diagram; selected taxa Pioneer, Allerød, Younger Dryas OC Numbers in 100 cm3 sediment

  5. Earliest pioneers Immigration of new species after ~100 years 13320 7-8 ~100 yr

  6. Salix herbacea dominance Stability of snowy mid-alpine vegetation for 535 years 12745 Rapid demise of pioneers (competition) 8 535 yr 13280 8

  7. Allerød - Younger Dryas Younger Dryas Breakup of vegetation cover in ca. 10 years Expansion of open ground high alpines 12745 4 1oC in 10 yr 6 9 Allerød 13280

  8. Younger Dryas 11515 7 205 Increase in productivity 1oC in 205 yr 11720 High-alpine vegetation Stability for 1240 years 1240 yr 5-6 Unstable high-alpine landscape with glacier 12745 10-20 yr Younger Dryas

  9. Younger Dryas - Holocene Extinctions due to rapid temperature rise Holocene Local extinctions of sensitive Arctic-alpines 9 11400 1oC in ~55 yr 115 yr 7 11515

  10. Early Holocene Expansions 10700 gone 10 815 yr Increased competition 560 yr Grassland and dwarf-shrub heath development 11.5 decline 11260 10 1oC in 180 yr 9 255 yr 1oC in ~55 yr Holocene 7 11515 Expansion. Warmth tolerant, little competition

  11. Birch woodland Immigration,Competition,Stability 1000s years 12 Holocene 10840 675 11.5 420 1oC in ~130 yr 11260 10 1oC in ~130 yr dwarf shrub heath. Immigration, CompetitionStability 420 years 7 grasslands, wetlands, tall ferns.Immigration, SuccessionCompetition 11515 Younger Dryas

  12. PeriodTemp Rateofchange length yr PlantresponseVegetation oC yr per 1oC E Hol ~11 - 12 +/- 0 1000sImmigration, Expansion of Birch woodland 675 yr after YD-H Competition; Stability Birch woodland E Hol 10->11.5 190 yr 300Immigration, Expansion of Dwarf-shrub heath (Empetrum) and tall fern Stability (+Salix) dominance E Hol 7->10 140 yr 255 Decline of remaining alpines; ExtinctionImmigrationof grassland and flush species, tall ferns (145 yr after YD-H), and Grassland, wetland, tall ferns dwarf shrubs (255 yr after YD-H) Succession, Competition YD - Hol 7->9 75 yr 10-115 Extinctions of warmth intolerant alpines (over 10-115 yr). Expansionsof warmth tolerant alpines S. herbacea + alpine herb grassland YD 5-6 0 1240StabilityHigh-alpine open vegetation AL – YD 6->4 10 yr 10 Rapiddecline of Salix over 10 yr; Vegetation break-up Expansion of alpine herbs High-alpine vegetation Allerød 8 0 575 StabilityStable S. herbacea snowbed vegetation 60 S. herbacea increase over 60 yr S. herbacea dominance Competition Deglac. 8 0 60 SuccessionOpen alpine herbs; immigration Salix herbacea Deglac. 8 0 ~100 Immigrationby pioneers Open alpine herbs

  13. Lusvatnet 69oN Allerød Younger Dryas 9 11520 7 11650 930 yr 7 More arid 8-10 12450 6 High-Arctic taxa of open, arid habitats 12900 7-8 Pioneers. Taxa of open, dry, unstable ground and some snowbeds 7 1050 yr 6

  14. Lusvatnet Early Holocene Birch woodland with ferns and herbs ImmigrationStability 12 10520 Dwarf shrub heath/ferns Persisting Arctic- alpines 1000 yr 11.5 10 Dramatic decline in Arctic-Alpines 9.5 11520 7

  15. Jansvatnet 71oN Late glacial Dwarf-shrub heath devel. Increased oceanicity 10750 900 Hol Rapid response threshold 10 1oC in ~100 yr 11650 9 4-8 Warming (lake), no terrestrial response 1oC in ~75 yr 300 Sparse pioneer vegetation – very arid 4 YD 12400 1oC in ~40 yr 7 No macros; lake turbid (YD) 12760 6-8 Sparse pioneer vegetation - arid AL

  16. Jansvatnet Holocene Stability Birch at tree-line; increased windiness 10-11.5 Tipping point 9350 12 Birch woodland + ferns and dwarf shrubs (1550 yr) 750 yr 10100 12 Dwarf shrub heath 650 yr Increasing oceanicity 10750 900 yr 11

  17. Comparison of temperatures and rates; AL-YD Jansvatnet 330 km Lusvatnet 890 km Climatic boundary Kråkenes AL gradient stronger than today YD north-south contrast - aridity

  18. Comparison of temperatures and rates YD, Holocene

  19. Comparison of Vegetation

  20. Drivers of vegetation changes are Temperature and Precipitation (affected by sea-ice cover) • The absolute climate values, the changes, and the balances between them determine vegetation development through: ImmigrationExpansionCompetition Extinction • Under constant climate conditions, vegetation may show: Succession ImmigrationCompetition Stability Emerging pattern Small gradient, as today Increasing aridity

  21. warm wet Temperature Precipitation cold dry Immigration Go Arrive Stay Extinction Evolution Competition Succession T i m e

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