Water uptake parameters for Sage Brush

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JBrandenburg
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Joined: Mon Feb 15, 2021 3:40 pm
Location: USA

Water uptake parameters for Sage Brush

Post by JBrandenburg » Thu Feb 18, 2021 8:46 pm

Hello, I am looking for advice on assigning root water uptake parameters for Sage Brush (Artemisia tridentata). I need to assign either Feddes or S-Shape water uptake reduction model parameters. After a very thorough search, I haven't found any published values, and I don't think any of the built-in parameters are appropriate for something that drought tolerant and with such a high matric potential. Has anybody worked through this problem before? Thank you!

TSal
Posts: 3
Joined: Tue Feb 09, 2021 3:57 am
Location: USA

Re: Water uptake parameters for Sage Brush

Post by TSal » Fri Feb 19, 2021 4:30 am

I agree that the built in parameters are not appropriate for sage brush. Sage brush is a different "animal"; quite deep rooted and drought tolerant.

One thing I have done in the past is compare reported ET/PET data for different land covers (e.g. grass pasture to range pasture to sage brush) to develop ratios between these different land covers. For example, PET for grass pasture is 75cm/year and 50 cm/year for sage brush. This is reported data for your area.

In Hydrus you can then run your simulation with grass pasture values provided in Hydrus and develop an estimate of ET for that specific land cover. Then you can iteratively vary root parameters (both water update and rooting depth), hold all other inputs constant and calculate ET for the altered land cover. Once you end up with a similar ratio, and assuming your inputs are reasonable (reasonable estimates of rooting depth for sage brush, wilting point, etc.), then you likely have reasonable root uptake values to move forward with. It's not perfect, but it's a reasonable sound approach for an engineer.

I stress reasonable. If you are a scientist, you might be cringing. There likely is some obscure dissertation out there with data regarding sage brush rooting depth and limiting stresses for water uptake, but that doesn't make it correct...

JBrandenburg
Posts: 2
Joined: Mon Feb 15, 2021 3:40 pm
Location: USA

Re: Water uptake parameters for Sage Brush

Post by JBrandenburg » Fri Feb 19, 2021 3:05 pm

Thank you - I appreciate your quick reply! The calibration/investigation you describe seems totally reasonable to me. Would you mind sharing an example of the water uptake reduction parameters you have determined like this? I won't plan to rely on that, but it would be good to know if I am in the ballpark of what other people are finding.

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