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要旨:
Drought-induced tree mortality results from an interaction of several mechanisms. Plant
water and carbon relations are interdependent and assessments of their individual contributions
are difficult. Because drought always affects both plant hydration and carbon assimilation,
it is challenging to disentangle their concomitant effects on carbon balance and carbon
translocation. Here, we report results of a manipulation experiment specifically designed to
separate drought effects on carbon and water relations from those on carbon translocation.
In a glasshouse experiment, we manipulated the carbon balance of Norway spruce saplings
exposed to either drought or carbon starvation (CO2 withdrawal), or both treatments, and
compared the dynamics of carbon exchange, allocation and storage in different tissues.
Drought killed trees much faster than did carbon starvation. Storage C pools were not
depleted at death for droughted trees as they were for starved, well-watered trees. Hence
drought has a significant detrimental effect on a plant’s ability to utilize stored carbon.
Unless they can be transported to where they are needed, sufficient carbon reserves alone
will not assure survival of a drought except under specific conditions, such as moderate
drought, or in species that maintain plant water relations required for carbon re-mobilization.
