Changes in productivity partitioning induced by precipitation extremes increase inaccuracy of grassland carbon estimation

<p><span>The fraction of net primary productivity (NPP) allocated to belowground organs (<em>f</em>_BNPP) in grasslands is a critical parameter in global carbon cycle models; moreover, understanding the effect of precipitation changes on this parameter is vital to accurately estimating carbon sequestration in grassland ecosystems.&nbsp;Here, by conducting both a precipitation gradient experiment (100&ndash;500 mm) and a long-term observational study (34 years) in the Inner Mongolia grassland, we showed that <em>f</em>_BNPP decreased linearly along the precipitation gradient from extreme drought to extreme wetness due to stronger responses in aboveground NPP (ANPP) to drought and wet conditions than those of BNPP. The linearly decreasing response pattern in <em>f</em>_BNPP should be incorporated into models that forecast carbon sequestration in grassland ecosystems; failure to do so will lead to underestimation of the carbon </span><span>stock</span><span> in drought years and overestimation of the carbon </span><span>stock</span><span> in wet years in grasslands.</span></p>