How lateral dimension of roots determines aboveground self-thinning

Recent researches into population dynamic have demonstrated that the aboveground mass-density (M-N) exponents vary with environmental conditions and different justifications have been presented to account for such variation. However, little has been done, especially from the perspective of belowground plant parts to reveal the mechanisms underlying the self-thinning process of natural plant populations along an aridity gradient. To fill up this gap, we conducted field investigations at three sites along an aridity gradient in West China to find out whether ratios of root to shoot crown diameter change with aridity and whether such change is followed by variation in exponents (a) of aboveground mass-density relationships. Consequently, we discovered that ratios of root to shoot crown diameter increase with aridity and this increase is the cause of variation in aboveground a. (C) 2011 Elsevier B.V. All rights reserved.