Defining management rules for grasslands using weed demographic characteristics

Abstract

The study objective was to use demographic information to adjust forage production practices to control the invasive weeds golden chervil and yellow-rattle without herbicides by defining the population dynamics traits that are directly involved in weed responses to farming practices. The principal population traits are capacity for dominance, sensitivity and accessibility of targeted developmental stages, and variation in weed population reactions from year to year. On the basis of demographic surveys of these two weed species when subjected experimentally to various cutting regimes (by date and number), we used matrix simulation models to describe each weed in terms of these traits and to construct species-specific management strategies. Management strategies for golden chervil need to prevent new recruitment by focusing on limiting or eliminating seed production and seedling survival because adult mortality is insensitive to cutting. Grazing to a low residual height is proposed in spring, when seedling emergence is maximal, or when adults reach their apex height to prevent the development of reproductive stems. Cutting before flowering may also efficiently limit seed production. The annual life cycle of yellow-rattle allows more flexibility in its management, even when density fluctuates and is unpredictable. If cutting is scheduled to coincide with peak juvenile height, this can drastically reduce population density the next year, and the population can be eradicated within 3 yr.