sapwood ratio ref about ed2

[mdietze]

I don't know the ref, but I'm pretty sure pipe model derives a ratio between m2 leaf to m2 sapwood (cross sectional area).

On May 16, 2014, at 5:24 PM, Ryan Knox [email protected] wrote:

If anyone knows the reference for our parametrization of sapwood_ratio(1:17) = 3900 (see ed_params.f90), please chime in and lets get it in the code.

Unit consistency when calculating qsw suggests that sapwood_ratio is [m2 leaf / kg sapwood]. the definition in pft_coms for sapwood_ratio is a little vague, it says "area ratio"

qsw: [kg sapwood] / [kg leaf]
SLA: [m2 leaf] / [kg leaf]
sapwood_ratio: [m2 leaf]/[kg sapwood] ??

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[rgknox]

What you say seems to be the conventional wisdom I'm seeing in the literature.

see: "Allometric relationships predicting foliar biomass and leaf
area:sapwood area ratio from tree height in five Costa Rican rain
forest species"

On an aside, there seems to be some evidence that this area ratio has some dependency on height and other things, based on sapwood conductance. Maybe that would be a an interesting functionality to try some day.

In the mean time... if it is the case that sapwood_ratio is an area/area ratio, then we need to address the unit conversion. I will subdue my barking until I can get a ref or reason for our 3900.

But beware, I will not rest until I forget about this and get fixated on something else.

[crollinson]

So to revive an old thread, did the sapwood ratio and qsw ever get sorted out? I'm having trouble with the water balance in ED and I think it might comeback to sapwood ratios.

[mdietze]

@crollinson ironically I don't think the sapwood ratio affects water uptake, it just affects allocation

[mpaiao]

@crollinson Which error are you getting? Is it happening at the first day of the month? I'm asking because most of the time the error message that the model is not conserving energy/water/carbon budget is not caused by a real budget problem, but due to uninitialized variables.

@rgknox In case you haven't found the reference yet, I think the pipe model comes from these two papers, according to Moorcroft et al. 2001:
http://ci.nii.ac.jp/naid/110001881211/en
http://ci.nii.ac.jp/naid/110001881234/en

[crollinson]

@mpaiao I'm not receiving any error. My soil moisture is just ending up so low almost no matter what I do that it's having a hard time supporting deciduous trees.

[rgknox]

Thank you for the references Marcos. On that note, has anyone considered
the value in having a turnover rate control the flux of sapwood into
structural wood, thus moving NPP allocation that was originally destined to
sapwood+structural to just sapwood? While this is more true to reality, I
am not saying we will necessarily net any benefits from it. In fact, it
may just be another cat in our herd of cats (carbon pools) that we find
straying from a realistic value. In tropical systems there does not seem
to be a plethora of knowledge regarding how a plants ability to keep up
with sapwood turnover may or may not constrain it's ability to provide
adequate plumbing for its leaves (at least in tropical systems) and promote
a decline in its viability. Although a friend pointed me towards this
paper, which had some interesting points:

http://link.springer.com/article/10.1007/s00442-015-3220-y?wt_mc=alerts.TOCjournals

On Thu, Apr 2, 2015 at 9:42 AM, Christy Rollinson [email protected]
wrote:

@mpaiao https://github.com/mpaiao I'm not receiving any error. My soil
moisture is just ending up so low almost no matter what I do that it's
having a hard time supporting deciduous trees.

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#3 (comment).

[mpaiao]

@rgknox I've seen other models allocating to sapwood, and a fraction of sapwood would become heartwood based on the turnover ratio. Perhaps CLM? I think it would be an interesting test, though it may require a different definition of qsw (I remember that there was some debate on what qsw was supposed to represent at some point, and the values were very different. BTW, Yeonjoo Kim may know where the 3900 came from).

@crollinson Some suggestions to try to figure out what is causing the soil to dry so quickly.

1. Go to rk4_derivs.F90, and hard code transp = 0 right after transp is defined (and before qtransp is defined). A more extreme case would be to run with IED_INIT_MODE=-1 (total tree exclusion).
2. If soils are still becoming too dry, then the problem is in the hydrology. In this case, a good test would be to run with a more "average" soil (soil type 5 or 6) and see if the problem persists.

[crollinson]

@mpaiao Thanks for the suggestion. Interestingly, I turned IED_INIT_MODE=-1 and still get trees. That must've gotten disabled somewheres along the way. Looks like that gets to be added to the list of bugs to get fixed at some point.

In the meanwhile I'll try hardcoding transp=0 or removing PFTs (so I don't have to recompile the code) and see what happens. I suspect it's a parameterization issue rather than a bug (creating an aquifer helps a lot), but I'll post an issue if I think there's a structural problem.