Johnson and Matchett explored the roles of grazing and burning on root growth in experimental watersheds at Konza Prairie, Kansas. Annual burning resulted in a 25% increase in root regrowth compared to the unburned watershed, as plants compensated for N limitation by increasing allocation to roots. Grazing decreased root growth, especially in heavily grazed patches. Grazing by ungulates increased N cycling and availability. Therefore, grazed plants, instead of being N limited, experienced C limitation as shoots regrew and plants allocated less C to roots. Root ingrowth on the long-term unburned watershed was as low as in lightly grazed patches in the grazed watershed. Seemingly disparate treatments such as infrequent burning and grazing both had higher levels of N availability than annually burned prairie in the absence of grazers. Grazing increased net N mineralization rates from 87% to 617% compared to watersheds without grazers, whereas, annual burning decreased it by 50% compared to unburned prairie. Ultimately, differences in the quantity and quality of roots provide feedback to affect C and N cycling and help to maintain and even promote the fundamental differences in N cycling between burning and grazing in tallgrass prairie.
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