Functional Resource Heterogeneity Increases Livestock and Rangeland Productivity

Abstract

Most of the world’s rangelands are subject to large spatial and temporal variation in forage quantity and quality, which can have severe consequences for the stability and profitability of livestock production. Adaptive foraging movements between functional seasonal resources can help to ameliorate the destabilizing effects on herbivore body stores of spatial and temporal variability of forage quantity and quality. Functional dry-season habitats (key resources) provide sufficient nutrients and energy to minimize reliance on body stores and are critical for maintaining population stability by buffering the effects of drought. Functional wetseason habitats dominated by short, nutritious grasses facilitate optimal intake of nutrients and energy for lactating females, for optimal calf growth rates and for building body stores. Adaptive foraging responses to high-quality focal patches induced by rainfall and disturbance further facilitate intake of nutrients and energy. In addition, focused grazing impact in high-quality patches helps to prevent grassland maturing and losing quality. In this regard, the design of many rotational grazing systems is conceptually flawed because of their inflexible movement of livestock that does not allow adaptation to spatial and temporal variability in forage quantity and quality or sufficient duration of stay in paddocks for livestock to benefit from self facilitation of grazing. Similarly the fixed intraseasonal resting periods of most rotational grazing systems might not coincide with the key
pulses of nitrogen mineralization and rainfall in the growing season, which can reduce their efficiency in providing a functional recovery period for grazed grasses. This might explain why complex rotational grazing systems on average have not outperformed continuous grazing systems. It follows, therefore, that ranchers need to adopt flexible grazing management practices that allow adaptation to spatial and temporal variability in forage quantity and quality, allow facilitation of grazing (seasonlong grazing), and allow more effective recovery periods (season-long resting).