Production Ecology

of the

Greater Kruger Park System

RJ Scholes, N Hanan, WL Kutsch, S Archibald and A Nickless

bscholes@csir.co.za

KNP Network Meeting 12 March 2010

What is ‘Production Ecology?’

• The flow of energy and organic material (represented by carbon) through the ecosystem

• Primary production concerns only the plants

• It forms the foundation for secondary production by herbivores and higher trophic levels

• It is the basis of natural resource supply, including the carbon-based climate regulating service

Some terminology

NEE = NPP-Rh

Net Biome

Production

(=sink)

CO2CO2

Gross

Assimi-

lationNet Primary

Production

Net

Ecosystem

Exchange

Gross

Primary

Production

Light

respiration

Plant

respiration

Heterotropicrespiration

NPP

NEE

Rh

Export,Harvest,

Disturbance

Photo of the Skukuza flux

tower

22 m

16 m measurement height

10 m vegetation height

Operational since 2000

The Skukuza flux towerSkukuzacamp

15 km

Located on an ecotone

Sandy soils

Clayey soils

Deflocculated

impervious layer

Combretum savanna Acacia savannaSeepline

Skukuza key carbon publicationsScholes, R.J., N. Gureja, M. Giannecchinni, D. Dovie, B. Wilson, N. Davidson, K. Piggott, C. McLoughlin, K.

van der Velde, A. Freeman, S. Bradley, R. Smart & S. Ndala. 2001. The environment and vegetation of the flux measurement site near Skukuza, Kruger National Park. Koedoe 44(1), 73-83

Williams, C.A., N.P.Hanan, J. Neff, R.J. Scholes, J. Berry, A.S. Denning and D.F. Baker. 2007. Africa and the global carbon cycle, Carbon Balance and Management, 2:3 doi:10.1186/1750-0680-2-3

Archibald, S. and R.J. Scholes.2007. Leaf green-up in a semi-arid African savanna – separating tree and grass responses to environmental cues. Journal of Vegetation Science 18, 583-594

Kutsch, W.L., N. Hanan, R.J. Scholes, I. McHugh, W. Kubheka, H. Eckhardt, C. Williams. 2008. Response of carbon fluxes to water relations in a savanna ecosystem in South Africa. Biogeosciences 5, 1797-1808

Archibald, S., A. Kirton, M. van der Merwe, R. J. Scholes, C. A. Williams, and N. Hanan. 2009. Drivers of interannual variability in Net Ecosystem Exchange in a semi-arid savanna ecosystem, South Africa. Biogeosciences 6, 261-266

Merbold, L., J. Ardo, A. Arneth, R. J. Scholes, Y. Nouvellon, A. de Grandcourt, S. Archibald, J. M. Bonnefond, N. Boulain, C. Bruemmer, N. Brueggemann, B. Cappelaere, E. Ceschia, H. A. M. El-Khidir, B. A. El-Tahir, U. Falk, J. Lloyd, L. Kergoat, V. Le Dantec, E. Mougin, M. Muchinda, M. M. Mukelabai, D. Ramier, O. Roupsard, F. Timouk, E. M. Veenendaal, and W. L. Kutsch. 2009. Precipitation as driver of carbon fluxes in 11 African ecosystems. Biogeosciences, 6, 1027-1041

Williams, C.A., N. Hanan, R.J. Scholes and W. Kutsch. 2009. Complexity in water and carbon dioxide fluxes following rain pulses in an African savanna. Oecologia 161, 469–480

Hanan, N, N Boulain, C Williams, R Scholes and S Archibald (in prep) Functional convergence in ecosystem carbon exchange in adjacent savanna vegetation types of the Kruger National park, South Africa.

Carbon cycle rough balance2000/1 (‘wettish year’)

i.e. net sink of ~0.5 tC/ha/y

Component gC/m2/y

NPP -1137

Rsoil 1047

Rherbivore 10

Net Ecosystem Production -84

Rfire 36

Net Biome Production -52

Interannual variability

Archibald, S., A. Kirton, M. van der Merwe, R. J. Scholes, C. A. Williams, and N. Hanan. 2009. Drivers of interannual variability

in Net Ecosystem Exchange in a semi-arid savanna ecosystem, South Africa. Biogeosciences 6, 261-266

Net E

cosys

tem

Exc

ha

ng

e g

C/m

2/y

25

75

Sink

Source

Canopy

conductance

and water

Kutsch, W.L., N. Hanan, R.J. Scholes, I. McHugh, W. Kubheka, H. Eckhardt, C. Williams. 2008. Response of carbon fluxes to

water relations in a savanna ecosystem in South Africa. Biogeosciences 5, 1797-1808

Water is the main factor controllingBoth photosynthesis and respiration

It works directly (eg through stomatal

Closure) and indirectly (through

phenology)

It is not only the current, but also the past

water availability that matters

Effects of temperature and water

Kutsch, W.L., N. Hanan, R.J. Scholes, I. McHugh, W. Kubheka, H. Eckhardt, C. Williams. 2008. Response of carbon fluxes to

water relations in a savanna ecosystem in South Africa. Biogeosciences 5, 1797-1808

Soil temperature ( C )

Soil

Respiration m

g C

O2/m

2/s

The split between trees and grasses

Archibald, S. and R.J. Scholes.2007. Leaf green-up in a semi-arid African savanna – separating

tree and grass responses to environmental cues. Journal of Vegetation Science 18, 583-594

Carbon fluxes in pulsed systems

Williams, C.A., N. Hanan, R.J. Scholes and W. Kutsch. 2009. Complexity in water and carbon dioxide fluxes following

rain pulses in an African savanna. Oecologia 161, 469–480

Net

Ecosyste

m E

xcha

nge

Days since rainfall pulse

Respiration

Photosynthesis

Net

Time to peak depends on

drought history

Hanan, N, N Boulain, C Williams, R Scholes and S Archibald (in prep) Functional convergence in ecosystem carbon exchange

in adjacent savanna vegetation types of the Kruger National park, South Africa.

Broadleafed vs Fineleafed

Although the controls

differ somewhat,

the effects tend to

cancel out.

Ecosystem NEE

is very similar

between Acacia

and Combretum

savannas

Acacia

Combretum

The bigger picture

Merbold, L., et al 2009. Precipitation as driver of carbon fluxes in 11 African ecosystems. Biogeosciences, 6, 1027-1041

Williams, C.A., N.P.Hanan, J. Neff, R.J. Scholes, J. Berry, A.S. Denning and D.F. Baker. 2007. Africa and the global carbon cycle,

Carbon Balance and Management, 2:3 doi:10.1186/1750-0680-2-3

African savannas as a whole are

highly variable

Management Implications

• Selling the carbon stocks or fluxes in the

KNP as carbon credits would be a bad

idea

– The net flux appears to be to the atmosphere

• It is feasible to repeatedly estimate the

NPP of the KNP as a monitoring variable

– But to be really useful, it would need to be disaggregated into tree and grass components, and we are not quite there yet.

Time to take a breath

and think of the next steps

• Skukuza is the longest-running flux tower in Africa, and one of the longest in savannas anywhere

• Current funding has come to an end, and so has the design life of many of the instruments

• What do we want to do with the site in the future?– Declare victory, dismantle and move on?

– Establish somewhere else?

– Maintain it as an C-cycle observation platform?– Elaborate the measurements to look at particular

processes?

Thanks

• SANParks for hosting the site for the past decade

• NASA, NOAA, NSF, EU FP6, DST and CSIR for supporting the science

• Jeff Privette, Niall Hanan, Werner Kutsch, Chris Williams, Ian McHugh, Sally Archibald, AleciaNickless, Walter Kubheka…

• and many other students and KNP staff who have contributed over the years