Applications of Dendrochronology in Agroforestry and ... · Our laboratory ... The analyses of...
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Our laboratory primarily focuses on the following aspects: 1) Assessment of climate growth relationships and evaluation of the effect of a changing climate on tree growth, agroforestry systems and forest development 2) Using tree ring data for proxy reconstruction of past climate conditions beyond the period where instrumental records are available, proxy evidence of past variation in the El Nino/ Southern Oscillation and other large-scale atmospheric circulations 3) The analyses of radial growth increment and stable isotopes at the inter-annual and intra-annual scale together with tree physiological parameters to better understand the ecological relationships between tree growth, climate and site conditions 4) Determining cambial dynamics, carbon allocation patterns and changes in wood anatomy, and hydraulic conductivity at different spatial and temporal resolutions 5) Changes in river flow, source of water and hydrological fluctuations in relaton to climate change 6) The study of past and present changes in wild fire by dating the fire scars left in tree rings to determine the frequency of fire occurrences Intra-annual stable carbon isotope (δ 13 C) study related to a labeling experiment to illustrate differences in temporal pattern of recent carbon allocation to wood structure of two functional types of trees. A proportion of labeled δ 13 C is stored in reserves of wood parenchyma and/or needles for up to three years in the late successional conifer species Podocarpus falcatus. In contrast, the pioneer broad-leaf tree (Croton macrostachyus) shows a high turnover and a carry-over effect of δ 13 C that is only detectable in the subsequent year. This shows the consequences of forest disturbance in carbon turn over (Krepkowski et al. 2013 New Phytologist). Conclusions The results highlight the potential of tree ring width and stable isotopes for reconstructing past climates and extreme events, determining water use efficiency and water sources and evaluating resilience of species to climate variability, as well as reconstructing hydrological fluctuations and river flow. Dendrochronology or examining tree rings as a method for scientific dating provides accurate dating because in principle each ring represents a year in a trees life. Seasonality in climate is the main driver for growth-ring formation and many tree species in the tropics are growing under a seasonal climate and hence experiencing cambial dormancy. Depending on climate seasonality and species, formation of rings can range from indistinct to distinct from annual to bi annual. Tree rings are history books and they can tell us many things about past climates, tree growth and vegetation dynamics, history of people and their landscapes, and the rise and fall of civilization, among many others. Knowledge of the range of natural climate variability and tolerance range of tree species to climatic stress is scarce especially in the tropics and subtropics. Aster Gebrekirstos World Agroforestry Centre, Nairobi, Kenya ([email protected]) Applications of Dendrochronology in Agroforestry and Climate Change Research What is dendrochronology and what can it tell us? sample preparation • stem disks from dead trees or increment cores can be used • Careful sample preparation (polishing the surface with sanding paper of different grit size is important) • for δ 13 C and δ 18 O series measurements were done using mass spectrometry. holes indicate sample preparations for δ 13 C and δ 18 O series measurements using mass spectrometry. how was past climate and its impacts? Were there extreme events and how frequent ? From daily to seasonal dynamics: does the species form annual rings ? When and how big does it grow and how sensitive is it to climate variability? 0 100 200 300 400 500 600 700 800 1926 1931 1936 1941 1946 1951 1956 1961 1966 1971 1976 1981 1986 1991 1996 2001 2006 scle Tug scle nub year Ring width ( mm) Sahel drought ? Ring width cross correlation of S. birrea between Tugure and Nubere showed a similar pattern and positive correlation (r=0.54) Location specific climate reconstructions? Reconstruction of precipitation and source of water? δ1 3 C and δ 18 O of S. birrea along a climate gradient follow a similar pattern, showing that external factors affect isotope fractionations in a similar way. However, δ 13 C from the Sahel region is highly enriched compared to the transition Sudan Sahel zone. In contrast its δ 18 O differences are not quite so obvious. The annual δ 13 C and δ 18 O patterns of S. birrea correlate negatively with precipitation, PDSI (Palmer Drought Sensitivity Index) (of August up to r=-0.65), and show positive correlations with temperature (r=0.72). High temperature (evaporative demand) in drought years would cause stomatal closure and preferential loss of the light oxygen isotope resulting in high concentration of δ 13 C and δ 18 O, respectively. S birrea is sensitive to climate variability. The strong correlation of δ 18 O with rainfall also indicates that S. birrea is using soil water (precipitation). (Gebrekirstos et al. 2011). Hydrological fluctuations and river flow Acknowledgements We are grateful to CCAFS for funding the lab set up, all our project collaborators and Prof. Dr. Achim Braeuning Carbon turn over
Transcript of Applications of Dendrochronology in Agroforestry and ... · Our laboratory ... The analyses of...
Our laboratory primarily focuses on the following aspects:
1) Assessment of climate growth relationships and evaluation of the effect of a changing climate on tree growth, agroforestry systems and forest development
2) Using tree ring data for proxy reconstruction of past climate conditions beyond the period where
instrumental records are available, proxy evidence of past variation in the El Nino/Southern Oscillation and other large-scale atmospheric circulations
3) The analyses of radial growth increment and stable isotopes at the inter-annual and intra-annual scale together with tree physiological parameters to better understand the ecological relationships between tree growth, climate and site conditions
4) Determining cambial dynamics, carbon allocation patterns and changes in wood anatomy, and hydraulic conductivity at different spatial and temporal resolutions
5) Changes in river flow, source of water and hydrological fluctuations in relaton to climate change
6) The study of past and present changes in wild fire by dating the fire scars left in tree rings to determine the frequency of fire occurrences
Intra-annual stable carbon isotope (δ13C) study related to a labeling experiment to illustrate differences in temporal pattern of recent carbon allocation to wood structure of two functional types of trees. A proportion of labeled δ13C is stored in reserves of wood parenchyma and/or needles for up to three years in the late successional conifer species Podocarpus falcatus. In contrast, the pioneer broad-leaf tree (Croton macrostachyus) shows a high turnover and a carry-over effect of δ13C that is only detectable in the subsequent year. This shows the consequences of forest disturbance in carbon turn over (Krepkowski et al. 2013 New Phytologist).
Conclusions
The results highlight the potential of tree ring width and stable isotopes for reconstructing past climates and extreme events, determining water use efficiency and water sources and evaluating resilience of species to climate variability, as well as reconstructing hydrological fluctuations and river flow.
Dendrochronology or examining tree rings as a method for scientific dating provides accurate dating because in principle each ring represents a year in a trees life. Seasonality in climate is the main driver for growth-ring formation and many tree species in the tropics are growing under a seasonal climate and hence experiencing cambial dormancy. Depending on climate seasonality and species, formation of rings can range from indistinct to distinct from annual to bi annual.
Tree rings are history books and they can tell us many things about past climates, tree growth and vegetation dynamics, history of people and their landscapes, and the rise and fall of civilization, among many others.
Knowledge of the range of natural climate variability and tolerance range of tree species to climatic stress is scarce especially in the tropics and subtropics.
Aster Gebrekirstos
World Agroforestry Centre, Nairobi, Kenya ([email protected])
Applications of Dendrochronology in Agroforestry and Climate Change Research
What is dendrochronology and what can it tell us?
sample preparation
• stem disks from dead trees or increment cores can be used
• Careful sample preparation (polishing the surface with sanding paper of different grit size is important)
• for δ13C and δ18O series measurements were done using mass spectrometry.
holes indicate sample preparations for δ13C and δ18O series measurements using mass spectrometry. how was past climate and its impacts? Were there
extreme events and how frequent ?
From daily to seasonal dynamics: does the species form annual rings ? When and how big does it grow and how sensitive is
it to climate variability?
0
100
200
300
400
500
600
700
800
1926 1931 1936 1941 1946 1951 1956 1961 1966 1971 1976 1981 1986 1991 1996 2001 2006
scle Tug scle nub
year
Ring width ( mm
)
Sahel drought ?
Ring width cross correlation of S. birrea between Tugure and Nubere showed a similar pattern and positive correlation (r=0.54)
Location specific climate reconstructions?
Reconstruction of precipitation and source of water?
δ13C and δ18O of S. birrea along a climate gradient follow a similar pattern, showing that external factors affect isotope fractionations in a similar way. However, δ13C from the Sahel region is highly enriched compared to the transition Sudan Sahel zone. In contrast its δ18O differences are not quite so obvious. The annual δ13C and δ18O patterns of S. birrea correlate negatively with precipitation, PDSI (Palmer Drought Sensitivity Index) (of August up to r=-0.65), and show positive correlations with temperature (r=0.72). High temperature (evaporative demand) in drought years would cause stomatal closure and preferential loss of the light oxygen isotope resulting in high concentration of δ13C and δ18O, respectively. S birrea is sensitive to climate variability. The strong correlation of δ18O with rainfall also indicates that S. birrea is using soil water (precipitation). (Gebrekirstos et al. 2011).
Hydrological fluctuations and river flow
Acknowledgements
We are grateful to CCAFS for funding the lab set up, all our project collaborators and Prof. Dr. Achim Braeuning
Carbon turn over
