No abstract

Different grazing strategies impact grassland plant production and may also regulate the soil carbon formation. For a site in semiarid temperate steppe, we studied the effect of combinations of rest, high and moderate grazing pressure over three stages of the growing season, on the process involved in soil carbon sequestration. Results show that constant moderate grazing (MMM) exhibited the highest root production and turnover accumulating the most soil carbon. While deferred grazing (RHM and RMH) sequestered less soil carbon compared to MMM, they showed higher standing root mass, maintained a more desirable pasture composition, and had better ability to retain soil N. Constant high grazing pressure (HHH) caused diminished above- and belowground plant production, more soil N losses and an unfavorable microbial environment and had reduced carbon input. Reducing grazing pressure in the last grazing stage (HHM) still had a negative impact on soil carbon. Regression analyses show that adjusting stocking rate to ~5SE/ha with ~40% vegetation utilization rate can get the most carbon accrual. Overall, the soil carbon sequestration in the temperate grassland is affected by the grazing regime that is applied, and grazing can be altered to improve soil carbon sequestration in the temperate steppe.

Livestock have long been integral to food production systems, often not by choice but by need. While our knowledge of livestock greenhouse gas (GHG) emissions mitigation has evolved, the prevailing focus has been—somewhat myopically—on technology applications associated with mitigation. Here, we (1) examine the global distribution of livestock GHG emissions, (2) explore social, economic and environmental co‐benefits and trade‐offs associated with mitigation interventions and (3) critique approaches for quantifying GHG emissions. This review uncovered many insights. First, while GHG emissions from ruminant livestock are greatest in low‐ and middle‐income countries (LMIC; globally, 66% of emissions are produced by Latin America and the Caribbean, East and southeast Asia and south Asia), the majority of mitigation strategies are designed for developed countries. This serious concern is heightened by the fact that 80% of growth in global meat production over the next decade will occur in LMIC. Second, few studies concurrently assess social, economic and environmental aspects of mitigation. Of the 54 interventions reviewed, only 16 had triple‐bottom line benefit with medium–high mitigation potential. Third, while efforts designed to stimulate the adoption of strategies allowing both emissions reduction (ER) and carbon sequestration (CS) would achieve the greatest net emissions mitigation, CS measures have greater potential mitigation and co‐benefits. The scientific community must shift attention away from the prevailing myopic lens on carbon, towards more holistic, systems‐based, multi‐metric approaches that carefully consider the raison d'être for livestock systems. Consequential life cycle assessments and systems‐aligned ‘socio‐economic planetary boundaries’ offer useful starting points that may uncover leverage points and cross‐scale emergent properties. The derivation of harmonized, globally reconciled sustainability metrics requires iterative dialogue between stakeholders at all levels. Greater emphasis on the simultaneous characterization of multiple sustainability dimensions would help avoid situations where progress made in one area causes maladaptive outcomes in other areas.

Understanding the mechanism of plant morphological plasticity in response to grazing and clipping of semiarid grassland can provide insight into the process of disturbance-induced decline in grassland productivity. In recent studies there has been controversy regarding two hypotheses: 1) grazing avoidance; and 2) growth limiting mechanisms of morphological plasticity in response to defoliation. However, the experimental evidence presented for the memory response to grazing and clipping of plants has been poorly reported. This paper reports on two experiments that tested these hypotheses in field and in a controlled environment, respectively. We examined the effects of long-term clipping and grazing on the functional traits and their plasticity for Leymus chinensis (Trin.) Tzvelev (the dominate species) in the typical-steppe grassland of Inner Mongolia, China. There were four main findings from these experiments. (i) The majority of phenotypic traits of L. chinensis tended to significantly miniaturize in response to long-term field clipping and grazing. (ii) The significant response of morphological plasticity with and without grazing was maintained in a hydroponic experiment designed to remove environmental variability, but there was no significant difference in L. chinensis individual size traits for the clipping comparison. (iii) Plasticity indexes of L. chinensis traits in a controlled environment were significantly lower than under field conditions indicating that plants had partial and slight memory effect to long-term grazing. (iv) The allometry of various phenotypic traits, indicated significant trade-offs between leaf and stem allocation with variations in plant size induced by defoliation, which were maintained only under grazing in the hydroponic controlled environment experiment. Taken together, our findings suggest that the morphological plasticity of L. chinensis induced by artificial clipping was different with that by livestock grazing. The miniaturization of plant size in long-term grazed grassland may reflect retained characteristics of dwarf memory for adaptation to long-term grazing by large herbivores.

Grasslands are the predominant forage source for grazing animals and cover more of the Earth's land than any other major vegetation type. Their values are not always recognised, and conversion to other uses is continuing at a high rate leading to greater environmental and socio‐economic problems. Overgrazing is one of the main drivers of productivity decline of grasslands, reflecting the pressures from excessive human populations and a demand for food. Some 20% of the world's grasslands are in a severely degraded state; others have suffered shifts to less‐desirable species. Biodiversity and greenhouse gas production have also been particular concerns. Estimates of productivity change all show a decline over recent decades, yet animal numbers continue to increase, particularly in the developing world. This paper critically reviews the projected demands for livestock products, driven largely by human population growth; the current health of the world's grasslands and how current livestock systems that depend on land conversion and overexploitation of grassland are inappropriate and need to be improved. Central to this argument is that small holders in the developing world will be responsible for a large amount of the future red meat production, and this can be achieved through more efficient livestock production systems using lower stocking rates. The Australian sheep industry is provided as an example of how livestock production and reduced environmental impacts can be achieved with improved efficiency. Changes will require smallholders to transition to a competitive, market‐oriented livestock industry, which will provide challenges.