Some outstanding questions regarding mechanisms of drought-related vegetation mortality

Background/Question/Methods

There is a growing body of research regarding the mechanisms of vegetation mortality during drought.  Along with this new research has come a valuable debate regarding how universal or variable these mechanisms may be globally.  Here I review the evidence for the variety of hypothesized mechanisms.

Results/Conclusions

As reported in the literature, there is both support and lack thereof for carbon starvation, hydraulic failure, and outright biotic overwhelming of tree defenses.  Some of these conclusions may be influenced by the a priori perspective brought into the studies; nonetheless, all of these studies provide valuable insight into tree mortality.  I propose that the process of each of these mechanisms is supported in nearly all studies, though the final straw in plant survival during drought is likely quite variable.  A synthetic unbiased approach is needed, in which all mechanisms are simultaneously tested, for us to advance our understanding of tree death during drought.