Figure 4.

Hypothetical relationships of whole-plant hydraulic conductivity and carbohydrate availability during drought. Carbohydrate availability is plotted using the simulation from Figure 1, and hydraulic conductivity follows a typical pattern from Brodribb and Cochard (2009). The threats of hydraulic failure, biotic attack, or outright carbon starvation are enhanced by the interdependent feedbacks between conductivity and carbohydrates. The abundance of biotic agents that kill their hosts varies with species, climate, and region, so a flat line is used to indicate their general presence rather than a specific attack agent. If these agents are present, their attack is more likely to result in mortality after the threshold is exceeded.