Vegetation water potential from CLM5 forcing with concep

[whh_xkp]

Why the vegetation water matric potential for canopy was higher in the grassland and desert, comparing that in the forest ecosystem.

 

[djk2120]

Hello Haohao WU,

Thanks for your interest and for pointing this out. It sounds like you were expecting grasslands to experience more negative leaf water potential. I guess they might be drier in general, right? I'd be very interested to see any literature you might know of that covers this topic. We're always looking for these kinds of papers!

At this point vegetation water potential is not fully validated in the model. We are currently carrying out parameter estimation work to understand and improve the plant hydraulics. Part of why the forests are showing lower leaf water potential is due to the larger stature. Assuming equal xylem conductivity, taller trees experience a larger drop in water potential from soil-to-leaf, due to the longer conducting path. But it's hard to say what's most important in your plot, given that this looks like a snapshot of a single day, where the specific meteorology could play a significant role as well.

Note also that the VEGWP field will average day time and night time values of water potential. It can often be useful to look at half-hourly or daily minimum values to get a better sense of the water potential dynamics. I should also note that the values of VEGWP would not be significant in desert areas, and should be ignored.

best,
Daniel Kennedy

 

[whh_xkp]

Hello Haohao WU,

Thanks for your interest and for pointing this out. It sounds like you were expecting grasslands to experience more negative leaf water potential. I guess they might be drier in general, right? I'd be very interested to see any literature you might know of that covers this topic. We're always looking for these kinds of papers!

At this point vegetation water potential is not fully validated in the model. We are currently carrying out parameter estimation work to understand and improve the plant hydraulics. Part of why the forests are showing lower leaf water potential is due to the larger stature. Assuming equal xylem conductivity, taller trees experience a larger drop in water potential from soil-to-leaf, due to the longer conducting path. But it's hard to say what's most important in your plot, given that this looks like a snapshot of a single day, where the specific meteorology could play a significant role as well.

Note also that the VEGWP field will average day time and night time values of water potential. It can often be useful to look at half-hourly or daily minimum values to get a better sense of the water potential dynamics. I should also note that the values of VEGWP would not be significant in desert areas, and should be ignored.

best,
Daniel Kennedy

The diurnal dynamic of simulated leaf water potential at site scale is readily comprehensible and very useful. When it comes to the spital pattern, I just guess more negative leaf water potential in grassland than that in the forest ecosystem. This bothered me for quite some time. But here, your explanation of the model results is convincing and inspired me a lot.

Thanks a lot for the detailed explanation!