Table 3.
Soil microbial biomass C and estimates for ecosystem carbon cycle components.
| Grazing intensity (sheep ha−1)a | ||||
|---|---|---|---|---|
| 0 | 8 | 16 | SEM | |
| Soil microbial biomass C | ||||
| Winter, November 2010 (g kg−1 dry soil) | 2.60 | 2.19 | 2.95 | 0.40 |
| Spring, April 2011 (g kg−1 dry soil) | 3.19 | 4.08 | 4.39 | 0.39 |
| Summer, August 2011 (g kg−1 dry soil) | 2.80 | 2.52 | 2.67 | 0.31 |
| Winter grazing (1 October to 29 December 2010) | ||||
| Est. herbage intake of sheep (t DM ha−1, 90 days) | − | 639 | 1,281 | 123 |
| Herbage mass change during grazing (kg DM ha−1) | 122 | −399 | −450 | 124 |
| Energy harvested (GJ ha−1 a−1)b | − | 5.11 | 10.24 | 0.99 |
| Metabolic grazing days (kg0.75 day ha−1 a−1)c | − | 8,830 | 16,890 | 132 |
| Summer grazing (1 July to 30 September 2011) | ||||
| Est. herbage intake of sheep (kg DM ha−1) (90 days) | − | 380 | 730 | 68 |
| Herbage mass change during grazing (kg DM ha−1) | 266 | −11 | −108 | 61 |
| Energy harvested (GJ ha−1)b | − | 4.13 | 8.03 | 0.75 |
| Metabolic grazing days (kg0.75 day ha−1 a−1)c | − | 6,690 | 13,150 | 48 |
| Annual CO2 fluxes | ||||
| Estimated CO2 loss by animal respiration (t ha−1 a−1)d | − | 0.49 | 0.97 | 0.070 |
| Total respiration (soil + herbage) (t CO2 ha−1 a−1) | 28.0 | 29.5 | 33.4 | 1.3 |
| Soil respiration (t CO2 ha−1 a−1)e | 24.4 | 21.9 | 23.7 | 1.0 |
| Herbage respiration (t CO2 ha−1 a−1) | 3.6 | 7.6 | 9.7 | 1.6 |
| Animal-induced summer respiration increase (t CO2 ha−1 a−1)f | − | 0.075 | 0.149 | 0.024 |
| Tentative estimate of herbage GPP (t CO2 ha−1 a−1)g | 25.3 | − | − | − |
Eight sheep on 1.0 or 0.5 ha, respectively, for 90 days with separate summer and winter plots.
Calculations as described by Chen et al. (2010).
Theoretically provides common units for feed demand of differing animal species to be summed.
Assuming herbage 48% C and 55% of C ingested by animals respired (Parsons et al., 2013).
Soil temperature response coefficients in this Table were used to adjust values downwards to correct for soil warming on bare soil with herbage removed in spring and summer and radiative cooling in winter.
Calculated from co-efficient 0.0078 in Table 2.
Calculated provisionally by combining data from two studies as described in “Scaling Up to Ecosystem Level and Impact of Grazing” section.