Grassland species respond differently to altered precipitation amount and pattern

Abstract

An increase in precipitation amount with prolonged inter-rainfall intervals is predicted to occur in the Inner Mongolia grassland in the future. However, how the native species respond to such alterations remains poorly understood. We collected the seeds of eight species from a natural community and raised their seedlings by pot culture. The responses of these species to manipulated precipitation amount and inter-rainfall intervals were examined by rainout shelters. The biomass production in seven out of eight species was enhanced by increased precipitation amount. However, the impacts of prolonged inter-rainfall interval differed substantially among species, with one being promoted, two suppressed and five not affected. For most species, biomass allocations among vegetative organs were neither affect by precipitation amount nor by inter-rainfall intervals. In contrast, the impacts on species’ reproductive allocation were highly species-dependent. Soil moisture, soil temperature and soil inorganic nitrogen played important roles in affecting species’ biomass production but the pathways, directions (positive or negative) and magnitudes were species-dependent. Given that these eight species jointly represent about 80% of community biomass production, the impact of altered precipitation pattern on grassland ecosystems may be more difficult to predict than that of altered amount.