Variation in root:shoot ratios induced the differences between above and belowground mass–density relationships along an aridity gradient

Despite the importance of root density regulation, this has received little attention compared with density regulation of aboveground plant parts and there is a similar lack of comparisons between above and belowground mass–density relationships. Here we report on field investigations in three sites to study these two aspects. We found that the belowground mass–density exponents (α) were closer to −4/3 and they varied less than the aboveground α along an aridity gradient. These differences arose because of variation in root:shoot ratios.