Observations on biomass dynamics of a crested wheatgrass and native shortgrass ecosystem in southern Wyoming

Abstract

Above- and belowground net primary production (ANPP and BNPP) were compared between a 30-year-old crested wheatgrass site and an adjacent native shortgrass prairie. ANPP was estimated using successive harvests in May, June, July, and October 1985. BNPP was estimated using soil cores to a depth of 100 cm at the same time that aboveground harvests were made. ANPP was significantly greater in the crested wheatgrass site compared to the native site, but belowground and total net primary production were not different. The native shortgrass system, however, had greater live root biomass early in the growing season. The crested wheatgrass system had a high accumulation of aboveground dead material at the start of the growing season, which was followed by a significant decline in June and an increase in July and October. The native shortgrass system, however, had significantly lower accumulations of aboveground dead material. Approximately 92% of the fixed carbon in the native site was allocated belowground, while crested wheatgrass allocated about 85% of its fixed carbon belowground.