Reduced grazing pressure delivers production and environmental benefits for the typical steppe of north China

Abstract

Degradation by overgrazing is common in many areas of the world and optimising grassland functions depends upon finding suitable grazing tactics. This four-year study on the northern China steppe investigated combinations of rest, moderate or heavy grazing pressure early in the summer growing season, then moderate or heavy grazing in the mid and late season. Results showed that moderate grazing pressure (~550 sheep equivalent (SE) grazing days ha(-1) year(-1)) gave the optimal balance between maintaining a productive and diverse grassland, a profitable livestock system, and greenhouse gas mitigation. Further analyses identified that more conservative stocking (~400 SE grazing days ha(-1) year(-1)) maintained a desirable Leymus chinensis composition and achieved a higher live weight gain of sheep. Early summer rest best maintained a desirable grassland composition, but had few other benefits and reduced incomes. These findings demonstrate that reducing grazing pressure to half the current district stocking rates can deliver improved ecosystem services (lower greenhouse gases and improved grassland composition) while sustaining herder incomes.

Figure 1

The relationship between average vegetation growth (kg DM ha⁻¹ day⁻¹) and (a) grazing pressure measured as SE grazing days ha⁻¹ year⁻¹ (1 SE = a 50 kg reference weight animal; Y = −0.03154X + 44.86, Adj R² = 0.55); and (b) utilization of above ground herbage mass due to grazing (Y = 8.84 + 44.54*0.0219^X, Adj R² = 0.87) for season long grazing treatments between 2011 and 2013. Growth rate and utilisation were not calculated for rest treatments.

Figure 2

The relationship between average grazing season herbage mass ln +1 (kg DM ha⁻¹) and SE grazing days ha⁻¹ year⁻¹ (1 SE = a 50 kg reference weight animal); Adj R² = 0.94) between 2010 and 2013 (2010, Y = −0.00083X + 1.1451; 2011, Y = −0.00074X + 0.86; 2012, Y = −0.00083X + 0.7452; 2013, Y = −0.0013X + 0.9387).

Figure 3

The average liveweight gain (LWG) per head (g hd⁻¹ day⁻¹) compared to herbage mass for season-long grazing (__; Y = 136.8 – 126.8(0.0391X); Adj R2 = 0.44) and rest (_ _; Y = 113.1X – 0.7; Adj R2 = 0.64) grazing treatments.

Figure 4

The average proportion of (a) Leymus chinensis (Y = 0.9035−0.7475(0.067^X); Adj R² = 0.80), (b) Artemisia scopari (Y = 0.02464 + 0.2865(0.00803^X); Adj R² = 0.68) and c) forbs (Y = 0.0212 + 0.4307(0.0666X); Adj R2 = 0.68) throughout the year compared to the average herbage mass.

Figure 5. Partial redundancy analysis (RDA) of field data in axis1 × aixs₂ ordination planes constrained by the five treatments.