Climate-driven interannual variability in net ecosystem exchange in the Northern Great Plains grasslands ZhangLi; Wylie,B.K.; Ji,L.; Gilmanov,T.G.; Tieszen,L.L. Rangeland Ecology and Management: 1, 40-50 2010 10.2111/08-232.1 https://eurekamag.com/research/034/585/034585791.php