摘要
平衡理论强调家畜和草地资源之间的生物反馈,主张采取保守放牧策略保证草地生态系统的稳定性,草地管理的目标是调节草地牧草供给量和家畜饲草需求量平衡。基于非平衡理论的"新草地科学",则强调气候因素尤其是降水,决定着干旱、半干旱区草地承载力,主张采取机会主义策略,充分利用草地并维持草地基况。传统上,草地载畜量的确定是先计算生长季末的草地产量,利用草地利用率等校正系数校正,再除以家畜的年平均需求量;但由于其没有考虑牧草质量、饲喂价值和家畜营养需求,载畜量估计存在误差,从而导致争议。本文依据国内外研究进展,回顾了草地载畜量概念的发展和演变,比较了草地产量载畜量、营养载畜量(包括标准干草载畜量、总可消化养分及可消化粗蛋白载畜量、能量载畜量)差异,归纳了草地载畜量在应用上的争议。本文指出,由于牧草养分的季节变化动态,采用家畜营养需求法估测的载畜量值通常较草地产量法为低,放牧实践上应采用2种方法相结合估算草地载畜量,根据估算数较低者确定草地载畜量有利于草地可持续利用和保护。草地通常既存在平衡态,也存在非平衡态;而基于平衡理论的保守放牧策略在放牧率和放牧压力上,与基于非平衡理论的机会放牧策略存在差异;放牧管理应结合气候条件、草地基况、草地产权制度、政府贴现与否及市场价格等因素,选择保守放牧策略或机会放牧策略,实现草地畜牧业生产的生态和经济效益。由于生态模型通过模拟草地对放牧的响应及放牧对草地的影响,是草地管理的基础,本文归纳了草地放牧管理相关的生态模型和放牧管理应用程序,以期为草地放牧管理决策提供参考。
Based on equilibrium theoretical models, the response of vegetation to grazing pressure is linear and reversible, and can be manipulated predictably with stocking rates. This equilibrium-based theoretical model advocates a conservative stocking strategy to maintain internal ecosystem regulation and stability. The management goal is to maintain a balance between stocking numbers and feeding resources. In contrast, ＂new rangeland science＂ based on non-equilibrium ecological dynamics placed greater emphasis on external disturbances as drivers of ecosystem behavior. The ＇new science＇, proposes that plant composition and biomass in semi arid rangelands are primarily driven by rainfall and not by grazing pressure. Management of such systems should be opportunistic and take advantage of, or create, conditions which allow switches to a more desirable state. There are two major approaches： plant- or animal-oriented, to determine rangeland carrying capacity （CC） The traditional technique for determining 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 feeding requirements of a livestock unit. Using total herbaceous forage productivity as the single criterion to predict the livestock support capacity has been criticized because biomass quality and feeding value for livestock and livestock nutritional needs are largely ignored. Based on research progress, the development and evolution, controversy in theappli cation of the CC concept are summarized. The plant-, animal- （including standard hay-, total digestible nutri ents digestible crude protein- and energy oriented） oriented CC was also compared. It is evident that in view of the seasonal variation in nutrient content of natural herbage, animal-oriented permissible stocking rates on the whole tend to be lower than those predicted by the plant-oriented approach. The most complete approach to e valuate primary and secondary productivity of rangelands should combine plant and animal-based methods, rather than just plant oriented. In the case of a conservative grazing strategy, stocking rate was stable and grazing pressure fluctuated while for an opportunistic grazing strategy, stocking rate was unstable and grazing pressure was stable. Both equilibrium and non-equilibrium dynamics are found in rangelands, often at different times or governing different parts of the resource. Either conservative or opportunistic strategies could be cor rect, depending on the circumstances, including environmental variability and predictability, degradation and thresholds, property right regimes, discount rates, and market stability and prices. Finally, rangeland science and management are ultimately based on ecological models. In making management decisions, the specific model used is important because it determines both the expected ecosystem response to particular actions, as well as the strategies to attain desired conditions. The ecological model and grazing lands applications are summed up to provide reference for grazing management decision.
出处
《草业学报》
CSCD
北大核心
2014年第3期313-324,共12页
Acta Prataculturae Sinica
基金
中国科学院重要方向性项目(KSCX2-YW-G-076)
中国科学院战略性先导科技专项(XDA05050304)
保定市科技攻关项目(13zf063)资助
关键词
草地载畜量
平衡理论
新草地科学
放牧策略
草地生态模型
grassland carrying capacity
equilibrium theory
new grassland science
grazing strategy
grassland ecology model
