A review on grassland carrying capacity (Ⅱ): Parameters and calculation methods

doi:10.11686/cyxb20140438

Abstract

Abstract: The traditional technique for determining grassland carrying capacity (CC) is to calculate the total amount of forage at the end of the growing season,multiply this by a correction factor,and then divide by the average yearly feed requirements of a livestock unit. But there has been no consensus on the correction factors and time span. For convenience of management,ananimal unit (AU) is defined,based on the grazing pressure on grassland or grass consumption of certain specific animals,as the standard so other animals can be converted into animal units by comparing the same items. Currently,the most widely used animal units are animal unit (cow unit) and sheep unit (SU). But the AU is often defined on a live body weight (LBW) basis,which does not distinguish between physiological stages that may affect forage intake. What’s more,some forage species are not preferred by some kinds of livestock,and some ranges are better suited to one kind of livestock than to another; Animal units for different animal species should be adjusted based on the average dietary overlaps of these animal species on a specific type of range for calculating pasture-specific substitution ratios. It is important for pastoralist to be aware of use levels,residual vegetation and other grazing impacts during the period of use as well as utilization at the end of the growing season. Various methods were developed to estimate proper utilization rates,which can fall into two categories:estimation and measurement. The rule-of-thumb takes half-leave,half-use has been a standard in the range management profession for years. But forage output fluctuates considerably between years in response to changing climatic conditions and the concept of utilization rates means how it should be used in pasture management and has led to some confusion because a variety of ways in calculating pasture utilization rates are often not clearly defined. Furthermore,the choice of a proper use value has a profound effect on the estimate of CC. Based on research progress,the concept,measurement method and application dispute of parameters such as grassland output,proper utilization rate,livestock substitute rate et al. for CC calculation are summarized. The calculation method and adjustment factors for CC are also summarized to provide reference for grazing management decisions.

CLC Number:

S812

XU Min-yun,GAO Li-jie,LI Yun-qi. A review on grassland carrying capacity (Ⅱ): Parameters and calculation methods[J]. Acta Prataculturae Sinica, 2014, 23(4): 311-321.

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