The exposure of prairie soils to millennia of climate variability and change

The native grassland ecosystems of the Northern Great Plains (NGPs) are adapted to millennia of climate variability. Field experiments have examined the response of native prairie to a range of historical weather conditions that are unrepresentative of the full spectrum of hydroclimatic variability since grasslands became established on the NGP. We review existing paleo-environmental records of Holocene vegetation and climate and present a tree-ring reconstruction of the hydroclimate of the past millennium. Sedimentation rates and pollen in cores from prairie lakes reveal significant disturbance of native prairie under drought conditions, but also relatively rapid recovery of the grassland when the climate cycles back to wetter conditions. Tree-ring signals of prolonged and severe drought coincide with the reactivation of sand dune fields and indicators of reduced vegetation cover and soil erosion in the lake sediments. Climate model projections of future changes in the soil water balance suggest that prairie grasslands will be subject to drier conditions like those in the paleoclimate record from the mid-Holocene and more recent medieval warm period. The stability and resistance of prairie soils to wind and water erosion, as a function of the resilience of native grassland, contrast with the agroecosystems that have replaced most of the native prairie. By casting a unique paleo-environmental perspective on the resilience of native prairie as a protective soil cover, this paper provides a context and further support for agricultural practices that restore and maintain soil health.