Annual burning decreases seed density in the upper soil layers of the seed bank

Abstract

The seed bank records the plant-life history of the prairie and is a source of regeneration following disturbance. Prairie flora have adapted and evolved unique responses to the periodic presence of fire. In order to determine the effects of burning on the seed bank and the prairie in general, we germinated soil samples from burned and unburned plots in a tallgrass prairie at CERA. We recorded the total number of seedlings, number of monocot individuals, number of dicot individuals, and number of morphospecies found in the upper (0-5 cm) and lower (5-10 cm) layers of soil within burn and no burn plots. Our research indicated that the number of viable seeds and the abundance of dicots varied significantly with burning. Although we hypothesized that burning would increase seed bank density because fire bolsters plant reproductive capacity, thus increasing seed bank input, we found that burning actually decreases the number of viable seeds in the seed bank. We attribute this to two important consequences of fireopening of the canopy and lethal temperatures. Our results suggest that burning promotes diversity of plant species above ground while reducing viable seed density in the upper layers of the seed bank.