Hydrological and Nutrient Controls on the Structure and Function of Southern African Savannas: A Multi-scale Approach

1. Hydrological and Nutrient Controls on the Structure and Function of Southern African Savannas: A Multi-scale Approach J.D. Albertson, K.K. Caylor, Paolo D’Odorico, Christelle Hély, Greg Okin, S.A. Macko, Natalie Mladenov, Lydia Ries, Susan Ringrose, T.M. Scanlon, H.H. Shugart, R.J. Swap, Matt Therrell, Lixin Wang and Robert Washington-Allen

2. Kalahari Transect • Wet and dry season field campaigns for basic ecological process and detailed structural measurements of vegetation

3. Kalahari Transect • Wet and dry season field campaigns for basic ecological process and detailed structural measurements of vegetation • Detailed soil characterizations

4. Kalahari Transect • Wet and dry season field campaigns for basic ecological process and detailed structural measurements of vegetation • Detailed soil characterizations • Instrumented long-term physical data records

5. Kalahari Transect • Wet and dry season field campaigns for basic ecological process and detailed structural measurements of vegetation • Detailed soil characterizations • Instrumented long-term physical data records • Field fertilization experiments with phosphorus and nitrogen and stable isotope analysis in experimental and spatially distributed contexts

6. IGBP Kalahari Transect Strong rainfall gradient, seasonal climate Uniform sandy soils – ‘Kalahari sands’ Heterogeneous vegetation; tree, shrub and grass in woodland, savanna, and shrubland mixtures. High net plant productivity, widespread biomass burning, high carbon turnover

7. Mean annual rainfall along the Kalahari Transect

8. Kalahari Rainfall – 1901-1996

9. Kalahari Rainfall – 1901-1996

10. Kalahari Rainfall – 1901-1996

11. Kalahari Rainfall – 1901-1996

12. Kalahari Rainfall – 1901-1996

13. Vegetation Patterns on the Kalahari Transect

14. Plant interactions dominate pattern Landscape interactions dominate pattern Spatial Variation in NDVI at Different Spatial Scales

15. Pattern and Process

16. Grass Cover Decreasing Tree Cover More Southerly and Drier Vegetation structural characteristics along the Kalahari Transect

17. Light TRADE-OFFS Moisture

18. TRADE-OFFS

19. Dispersed Clumped Depends on the Prior History

20. necessarily is not equivalent to v

21. Patch Leaf Multi-Patch Structure A Landscape Vegetation Model

22. UMD Tree Cover Data

23. Live Non-woody Live Tree Leaves Dead Non-woody Dead Tree Leaves

24. Fine-leaved nutrient-rich savannas Broad-leaved nutrient-poor savannas Sankaran et al. 2005 Nature 438:846-849

25. Rationale for a Key Role of Nutrient Availability at the Ecosystem Level Water Limitation Nutrient Limitation Scanlon et al. 2003 RSE

26. Does this have any practical implications?

27. Grazing Pressure across Southern Africa

28. Grazing Impact across Southern Africa during a Wet Year.

29. Grazing Impact across Southern Africa in a Dry Year.

30. In wet versus dry years, the impact varies regionally Dry Wet

32. The End

33. Nitrogen does not appear to be a limiting nutrient in these systems, at least for grasses. Dry End Wet End Wang et al. Climatic Change in revision

35. necessarily is not equivalent to v

36. Could you tell me again where we’re going with all this?

37. or Patch Leaf Regional Emissions to the Atmosphere Multi-Patch Structure

39. Domestic Industrial Wildfires Along with wildfires, there are other significant sources of emissions to the atmosphere.

40. Domestic Industrial Wildfires We have some understanding of the contribution of these different sources.

41. Transport Domestic Industrial Wildfires Regional Emissions Deposition