1. Spectral changes with leaf aging in Amazon caatinga
PPT：Chen Li

2. Contents 1 Introduction 2 Materials and methods 3 Results 4 Discussion5
Acknowledgments

3. Introduction

4. Introduction
Caatinga
卡汀珈群落
极端干旱的热带疏林和刺灌丛
NIR
Near-infrared

5. Introduction evergreen vs deciduous leaf age physical environment
Anatomical, biochemical and physiological properties of leaves
Introduction
associated spectral response
evergreen vs deciduous
leaf age
physical environment
a function of life strategy
light quality
life span

6. Introduction
Many changes in leaf-properties are associated with changes in the spectral quality of light transmitted, reflected and absorbed by leaves.
Spectroscopic techniques represent a potentially non-destructive means of evaluating leaf physiological function（Gamon et al. 1995)
Remote sensing of canopy spectral properties provides as a viable approach for scaling up physiological mesurements from leaf to global scales（Field. 1991)
A better understanding of mechanisms that contribute to the spectroscopic propertites of different tropical forest communities will help in the classification and extraction of ecological information from remote sensing.

7. The Amazon caatinga has distinctly low NIR reflectance relative to adjacent forest types at a landscape scale.

8. fungi, leafy liverworts, lichens, algae, bacteria
Introduction
natural morphological
leaf age
spectral changes
physiological changes
mechanical damage
fungi, leafy liverworts, lichens, algae, bacteria

9. Materials and methods

10. Materials and methods Species information
To test the leaf aging hypothesis we utilized spectroscopic techniques to study temporal changes in visible to NIR leaf spectra.
measured spectra from six caatinga dominants (Aldina, Pagamea, Clusia, Ouratea, Pradosia, Humiria)
Aldina heterophylla: slow growth rate, infrequent leaf flushes(once or twice in a season)
growing in situ difficult to simulate in a greenhouse
track populations of leaves

11. A B D C E Materials and methods Study design
each of the trees were between 2m and 5m tall B D
fully expanded green leaves or fresh flush of unexpanded leaves
leaves remained in full sun C E
six branches on each tree with fully sunlit leaves were tagged
photographs of each tree were collected from a fixed location

12. Timeline for phenology and spectral sampling
Timeline for phenology and spectral sampling. The vertical position of each collection as shown on the plot corresponds to the relative time at which measurements were made with collection one corresponding to day zero. Precipitation measured in Manaus is plotted to the left.

13. Reflectance, transmittance and absorptance spectra for Pradosia schomburgkiana and Protium heptaphyllum. Uncolonized, mature leaves are shown with thin, light grey lines, old foliage with moderate epiphyll cover as medium grey lines and old foliage with heavy epiphyll cover as thick, dark lines. Spectral differences due to leaf age and epiphyll cover are far more pronounced than species differences.

14. Materials and methods Leaf spectroscopy
Leaf spectra were measured using a portable spectrometer( Analytical Spectral) attached to an integrating sphere(Model ).
At the start of the experiment a leaf map was constructed, ensuring that leaf spectra were always collected from the same position on the leaf.
From each leaf a pair of four spectral measurements (reflectance and transmittance for both surfaces) were made.
The spectrometer used has a nominal spectral range between 329 and 1051nm
Leaf reflectance and transmittance from both surfaces were used to calculate leaf absorptance.

15. Results

16. Results Phenology and physical attributes
plots are shown of reflectance, transmittance and derived absorptance for uncolonized leaves and leaves with moderate and heavy epiphyll cover.

17. Results
Leaf spectra
In red wavelengths, reflectance showed a steady increase over the same period.
a slight decrease over the remaining period
Green reflectance decreased

18. In the NIR, reflectance showed an initial rapid increase
the combination of increasing red reflectance and decreasing red transmittance
In the NIR, reflectance showed an initial rapid increase

19. Results Epiphylls and necrosis广阔
Results
Epiphylls and necrosis
》》用前必读哦！
the upper leaf surfaces of dried specimens were observed to bear large patches of dark fungi 【moistened→little adherece】
four epiphyll desity categories: uncolonized, slight, moderate and necrotic
the net effect of an increase in NIR absorptance on an individual leaf basis, will be magnified by an increase in the incidence of coatings or necrosis on a canopy level

20. uncolonized, slight and moderate epiphyll cover or were necrotic
initial rapid increase of 4% over the first 70 days
leaf counts for each category as they varied over the study period
little change over the next 116 days
by the end of the study,NIR absorptance had increased to between 6 and 7%
NIR absorptance and the number of leaves in each category are reported.

21. Discussion

22. Discussion Physical attributes high leaf thickness low SLA
high leaf toughness

23. Discussion Spectral changes and leaf aging 01 02 03 04 05
the first 186 days : decreased NIR transmittance remaining 9 months: increased NIR absorptance (the only significant change in leaf spectra for the remaining 9 months occurred in the NIR) 01
absorptance at 550nm increased while reflectance and transmittance decreased at this wavelength 02
in this wavelength region, leaves showed a consistent increase in NIR absorptance and decrease in NIR transmittance 03
increase in NIR absorption with increasing leaf age 04
the ecological role of epiphylls in caatinga forest cannot be answered 05

24. Discussion Conclusions and implications1 2 3
The most significant finding is an increase in NIR absorptance with increasing leaf age.
A significant increase in NIR absorptance as leaves aged from a variety of caatinga species growing in central Amazonia.
Increased NIR absorptance may be attributed primarily to increased leaf necrosis and epiphllic growth on leaf surfaces.

25. D.A.Roberts·B.W.Nelson J.B.Adams·F.Palmer Acknowledgments
Spectral changes with leaf aging in Amazon caatinga.
Trees,12:

26. Thanks！！！