What is Dendroclimatology? What can students do? Andreas J. Kirchhefer Tromsø, Norway

Transcription

1 What is Dendroclimatology? What can students do? Andreas J. Kirchhefer Tromsø, Norway

2 What is dendroclimatology? The tree as a weather station Aims: Understanding the trees responses to climate Reconstructing climate Understanding modern climate Simple basic steps, but increasingly sophisticated methods

3 Principals and concepts of dendrochronology Prerequisit: An annual ring Limiting factors & ecological amplitude Crossdating Aggregate tree growth model Standardisation Autocorrelation Replication Site selection Uniformitarianism

4 Tree rings Seasonal climate with one dormant season Too cold Too dry Challenging: mediterranean climates Extremely difficult: tropical climate

5 Wood structure: conifers

6 Wood structure: conifers

7 Wood structure: conifers

8 Wood structure: broadleaved trees

9 Wood structure: broadleaved trees

10 Wood structure Think three-dimensional! Auxin model of tree growth => Partial missing rings

11 Limiting factors - Liebig s Law of the Minimum - Droughts

12 Cross-dating

13 Dendrochronology Dating of wood by means of tree-rings

14 3 yrs 8 yrs Living pines >68 yrs

15 Dead pines Snag: AD 9-46 Down wood: AD 984-8

16 Tree-ring series n = trees year AD

17 Brennskogtjern, 3 m

18 Aggregate model of tree growth Ring width is function of Age related growth trend Climate Endogeneous disturbance (within stand) Exogeneous disturbance (from outside) error

19 tree-ring index ring width (mm) RESIDUAL STANDARD raw values Standardisation removing age trend single core 8 9 year

20 tree-ring index ring width (mm) RESIDUAL STANDARD raw values Autocorrelation single core 8 9 year

21 tree-ring index ring width (mm) RESIDUAL STANDARD raw values Replication single core multiple cores chronology year

22 Site selection

23 Uniformitarianism The present is the key to the past ring-width index - Forfjord-Dividalen mean year AD

24 Dendroclimatology Stabile chronology Climate data Climate-response analysis Calibration / verification Reconstruction

25 North Cape Tromsø sites Narvik Rovaniemi

26 year AD tree-ring index Sa Sb S S3 S4 S5a S5b S6a S6b S7a tree-ring index Standard chronologies S7b S7c S8 S9a S9b S9c tree-ring index

27 ring index - - S-PC R-PC Regional standard chronologies ring index ring index - - S-COA R-COA - - ring index ring index - - S-ALP R-ALP coast - - ring index inland ring index - - S-INL R-INL - - ring index year AD 9 95 year AD

28 General growth response (PC) correlations.8 correlation coefficient From standard chronologies From residual chronologies correlations autocorrelation -.6 a s o n d J F M A Ma Js Jo An d J F9 M8 A7 M6 J5 J4 A3 months months years autocorrelation response functionresponse function regression coefficient a 7s 6o 5n 4d 3J F M A Ma Js Jo An d J F M A M J J A years months months

29 z-scores Tree-growth from July temperatures - R-PC from T7 hi (895-99), standard chronologies R adj = 4.6 % (47.3 %) 9 95 z-scores - - S-PC from T7 R-PC from T7 hi R adj adj 45.5 (44.3 %) = 4.6 % (47.3 %) z-scores - - S-PC S-PC (++3) from T7 T7 R adj adj 55. (55.7 %) = 45.5 % (44.3 %) z-scores - - S-PC (++3) T7 (t-4, t-3, t, t+) S-PC (++3) T7 R adj adj 69.8 (75. %) = 55. % (55.7 %) s 9 95 S-PC (++3) T7 (t-4, t-3, t, t+)

30 -.8 correlation coeff. r Coast - June Coast - July Coast - August.8 A mid-th century response shift ving Correlations rth Norway, the coastal and inland region NN Inland - June - June Coast 95 - June NN Inland - July - July 93 Coast 95 - July97 99 Last year of 3-yr windows Temperature Precipitation NN Inland - August - August 93 Coast 95 - August Inland - June Inland - July Inland - August.8

31 Multiproxy dendroclimatology Ring width Early- and latewood width Latewood density Stabile isotopes Cell morphology Other high-resolution climate archives: Ice cores, speleotems, sediments Corals, molluscs

32 Growth responses: - temperature (left) - precipitation (mid) - cloud cover (right) Andenes Tromsø Forfjorddalen Svolvær/Skrova Glomfjord mult. regr. coeff. mult. regr. coeff. mult. regr. coeff temp prec cloud RW FMAMJ J A FMAMJ J A FMAMJ J A MXD FMAMJ J A FMAMJ J A FMAMJ J A d3c FMAMJ J A FMAMJ J A FMAMJ J A

33 3 JA-temperatures from RW 3 JA-temperatures from d 3 C z-scores - z-scores JA-temperatures from MXD 3 JA-cloudiness from d 3 C z-scores - z-scores

34 Calibration statistics RE: Reduction of Error, CE: Coefficient of Efficiency Target <= predictor (model) Calibration n r R adj Verification RE CE JA temp <= RW (t-,t,t+) JA temp <= RW (t-,t,t+) JA temp <= MXD (t) JA temp <= 3 C (t,t+,t+) JA cloudiness <= 3 C (t,t+)

35 July-August climate from tree-rings.9 Fig. 4: July-August climate since AD A) Temperatures from RW, MXD and d3c z-scores z-scores z-scores z-scores B) Temperatures (RW, MXD) vs.. near-ground solar radiation (d3c) sunshine temp.

36 Synoptic dendroclimatology Large-scale networks Atmospheric circulation Teleconnections CRU TS3 Forfjord 3-proxy JA temp.

37 What can students do? - basics - Where do we find tree-rings? How do they look? Tree species, circumference, height, state? Site geology, slope aspect, soil moisture, vegetation type - what influences tree growth? Preparation: Tree-ring counts On discs or cores How old is the tree (vs. DBH & height, stand structure)?

38 What can students do? - basics () - Tree-ring patterns on discs From pith to bark Concentric? Growth discontinuities? Young conifers branch whirl count & height increment vs. TR

39 What can students do? - ring widths - Single-year analysis: skeleton plotting exteme rings, abrupt changes particular characteristics: frost rings, resin ducts Cross-dating (pointer years) Comparison with climate

40 What can students do? - ring widths () - Ring-width series: Measuring (measuring scale, scan, digital photography depending on RW) Cross-dating and chronology Dealing with age trends Comparison with climate Reconstruction excercise?

41 What can students do? - dating excercises - Stumps? Recently died trees? Buildings?