草地畜牧业系统:要素、结构和功能

Grassland Farming System: Components,Structure and Function

草地饲草生产联系牲畜生产组成一个紧密的整体,形成草地畜牧业系统,能量和营养在土壤-饲草-牲畜间转移流动,形成结构,并输出牲畜生产成为系统功能。草地畜牧业系统具有系统的一般特征:整体性、结构性、层次性、功能性、动态性;同时,又有独特的特征,即半自然半人工性,自然性主要表现为饲草生产是一个受土壤、气候决定的自然过程,人工性主要表现为牲畜放牧生产和饲养生产是一个有人工作用的过程。草地畜牧业系统各要素具有复杂的影响因子,并构筑成子系统,子系统的数量关系决定主系统的功能。定义草地畜牧业系统,并将各要素及其子系统纳入到统一的草地畜牧业系统有助于综合理解草地管理及其牲畜生产,有助于从系统层次进行思考,而不是纠缠于特定类型、性质、组成要素及其之间的关系或相互作用等细节。中国年用饲草料7亿t,生产2000万t牲畜,饲草转化率仅为2%～3%,系统效率非常低,发展有粮草地畜牧业对于促进北方草地畜牧业系统效率、保护草地具有根本意义。

Grassland farming system concepts consist of forage and livestock production as affected by grazing and driven by marketing.Energy and nutrients transferred from forage to animals form the system structure and function.Grassland farming system has generally common characteristics;for example behavior,structure,relationship,and integration.The system also has its specific characteristics,as influenced by being both a semi natural and semi human-made system.Its natural attribute is represented by a production process of grass/forage depending on soil and climate,while the human-made attribute is represented by a process of livestock production depending on forage quantities and qualities and labor involvement.Each component of the system has a series of elements to form a subsystem which allows total system efficiency.Appropriate definition of grassland farming system can improve our understanding about the integrated relationship between grassland and animal management.The facts are that the forage grasses of 0.3 billion ton from grassland and the forage stalks of 0.6 billion ton from cropland are produced per year in China.The total forages of 0.7 billion ton are consumed to produce the livestock of 20 million ton per year.The feed conversion ratio is only 2%~3% per year indicating that there is great potential to improve the efficiency of grassland farming system.