98 P. C. Miller et al 







0600 1800 0600 0600 



Solar Time 



1800 0600 



Solar Time 



FIGURE 3-18. Diurnal courses of leaf water po- 

 tential for 29-30 July 1973 for Arctophila fulva 

 (A.f), Dupontia fisheri (D.f.), Carex aquatilis 

 Cm.), Eriophorum angustifolium (E.a.J, Potentil- 

 la hyparctica (P.hJ and Salix pulchra S.p.). Meas- 

 ured (o = individuals in troughs, • = individuals 

 on polygon tops) and simulated ( — ) values are 

 given. Vertical lines are the 95% confidence inter- 

 vals. (After Stoner and Miller 1975.) 



potential to leaf water content. The simulated courses of leaf water 

 potential generally followed the observed courses (Figure 3-18). Simula- 

 tions for 1972, which was relatively warm and dry, indicated stomatal 

 closure occasionally in Carex and frequently in Dupontia (Figure 3-19). 

 Complete stomatal closure occurred in Dupontia for short periods. In 

 1973, Dupontia usually was partially stressed; Carex, Eriophorum and 

 Salix had little or no stress while Arctophila and Potent ilia showed com- 

 plete stomatal closure. 



