Figure 1. Eddy covariance ecosystem CO₂ flux measurements (discontinuous). Negative values by convention indicate a net gain of CO₂ by the ecosystem and positive values a net loss.

Figure 2. Measured and predicted response of bracteole photosynthesis to light. (i) Solid line indicates the predicted response of A to photon flux assuming a constant temperature (28°C) and VPD (0.5kPa). (ii) Measured (A) versus predicted (A’) assimilation rates with an idealised 1:1 line.

Figure 3. Bracteole photosynthetic and stomatal response to CO_2. (i) Measured photosynthetic response (A) of ten bracteoles to intercellular CO₂ concentration (C_i). Solid line indicates A/C_i curve predicted assuming light saturating conditions (>1500 µmol m^-2 s^-1) and constant VPD (0.5kPa). Inset: measured (A) and predicted (A’) rates of photosynthesis under identical conditions with an idealised 1:1 line. (ii) Measured (g_s) and predicted stomatal conductance (g_s’)

Figure 4. Measured and predicted responses of bracteole CO₂ uptake (A) to diurnal patterns of photon flux (I), temperature (T_leaf) and vapour pressure defecit (VPD) for two consecutive days with contrasting VPD ranges.

Figure 5. Papyrus canopy light extinction profile. (i) Penetration of light in the canopy profile. Measured values shown as filled circles and predicted values shown as a line, (ii) The modelled decline in the proportion of sunlit (direct beam) leaf area (F_sun) with depth into the canopy. Filled circles indicate calculated points, lines are interpolated between points. (iii) A diagrammatic vertical cross section of a typical papyrus stand at Lake Naivasha.

Figure 6. Predicted diurnal patterns of micrometeorological properties and associated canopy photosynthesis. (i) Predicted gross, net, culm and umbel photosynthetic rates on days 180 and 360. (ii) Predicted respiration for soil, culm and umbel elements. (iii) Simulated direct, diffuse and total solar radiation, (iv) Simulated diurnal pattern of ambient air temperature, (v) Simulated diurnal pattern of VPD.

Figure 7. Monthly patterns of canopy photosynthesis and macrometeorological properties. (i) Simulated canopy assimilation and respiration. Umbel gross assimilation (A_umbel), Culm gross assimilation (A_culm), Net canopy assimilation (A_net) and net ecosystem CH₂O flux (E_net). (ii). Monthly total culm, umbel and detritus respiration (including root/rhizome respiration). (iii). Measured and predicted light intensities above the canopy. Measured values based upon 10 year mean values of Muthuri et al. (1985). (iv). Measured and predicted temperatures. (v) Annual VPD cycle.

Figure 8. Ecosystem CO₂ flux measurements (i) Average diurnal cycle of measured and predicted ecosystem C flux. (ii) Measured against predicted ecosystem CO₂ flux over the measurement period with an idealized 1:1 line.

Figure 9. Papyrus carbon budget. (i) Gross canopy assimilation predicted by model. (ii) Canopy respiration predicted by scaling measured values. (iii) Net assimilation comprising predicted gross assimilation minus canopy respiration. (iv) Measured above ground productivity (Muthuri et al. 1989). (v) Below ground productivity derived from net assimilation minus above ground productivity. (vi) Detritus decomposition derived from total detritus C flux minus measured and scaled root/rhizome respiration. (vii) Scaled measurement of root/rhizome respiration. (viii) Scaled detritus C flux from soil respiration chamber measurements. (ix) Ecosystem C efflux estimated from eddy covariance measurements. Values given are expressed in terms of C.

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