Resprouting ability and mobile carbohydrate reserves in an oak shrubland decline with increasing elevation on the eastern edge of the Qinghai–Tibet Plateau

Abstract

Resprouting is the main regeneration mechanism of most Quercus species after severe disturbance such as fire or coppicing. Yet little is known about the relationships between the amounts of resources stored in the roots and resprouting ability when the total aboveground part of plants/trees was fully removed or destroyed, and about the resprouting ability in relation to increasing elevation associated with decreasing site productivity. The present study investigated the non-structural carbohydrate (NSC) concentrations and its pool size in roots of Quercus aquifolioides clumps grown at 3000m, 3500m, and 3950m a.s.l. on Zheduo Mt., southwestern China, to test two competing hypotheses that (1) decreases in net primary productivity and growing season length with increasing elevation result in less allocation to storage of belowground NSC reserves, so that after coppicing, shrubs at higher elevations produce fewer resprouts and less total biomass than those at lower elevations, vs. (2) the shrubs growing at high-elevation sites with low-productivity produce more resprouts and biomass than those at low-elevation sites after coppicing, as it is expected that resprouting is favored in low-productivity environments. Our results indicated that early resprouting of Q. aquifolioides shrubs after coppicing is largely determined by the initial carbohydrate pool but not by the carbohydrate concentrations in roots. The large resprouting vigor of this species may be mainly ascribed to its large ratios of root to shoot biomass or root NSC pool to shoot NSC pool. The resprouting vigor of clumps decreased significantly with increasing elevation, which corresponds to significant decreases in the root biomass or root NSC pool size per clump with increasing elevation. Resprouts self-thinned more early and rapidly in clumps at lower elevations than at higher elevations, which may be mainly resulted from competition occurred more early in the more productive sites at lower elevations compared to higher elevations. Our results support the 1st but not the 2nd hypothesis. The present study has important implications for resources storage dealing with ecophysiology-based management strategy of coppicing woodland across scales.