I stand open for correction, but would this not be more related to free
water than humidity? Unless I am mistaken, de Souza seems to be more
interested in the atmosphere that exists within soil pore-space.
The most interesting question that I hope he and his colleagues will
investigate will be the fluctuations in the upper atmosphere of saturated
soil "air" within those spaces, charted against temperature changes and
condensation as a fraction of available water that is beyond measurement by
conventional AWC (available water capacity) measurement techniques.
I hope that de Souza will post his methods and findings here soon.
WT
----- Original Message -----
From: "John Mickelson" <[email protected]>
To: <[email protected]>
Sent: Wednesday, August 28, 2013 7:48 PM
Subject: Re: [ECOLOG-L] Soil humidity from topographic data?
There are a number of reasonably well documented equations and soil moisture
model (or "Topographic Wetness Index, TWI) approaches for calculating soil
moisture parameters using a raster digital elevation model. The calculations
(which I'm guessing have evolved over the past few years) are simply a
function of the slope and the contributing upslope area; with the basic
understanding that, all things (such as land cover and soil catenas) being
equal, the bottom of a long slope slope will tend to be wetter than the top
of a short slope. Some of the older hydrological software addons to ArcGIS
(TauDEM, etc...) even have Soil Moisture functions included. The simplistic
notation is: LN (a/S) or the natural log of the Upslope Area divided by the
slope (for all points\pixels within the DEM).
H. Mitasova has been working on the geospatial estimation of such estimates
(which can easily be built into scripted functions within packages such as
ArcGIS with Spatial Analyst (as well as Open Source software such as
GRASS)...
For more see:
http://naldc.nal.usda.gov/download/44278/PDF
http://skagit.meas.ncsu.edu/~helena/gmslab/reports/CerlErosionTutorial/denix/Advanced/ErosionRep97/rep97.html
http://hydrology.usu.edu/RRP/userdata/4/87/Appendices.pdf
http://ks.water.usgs.gov/pubs/reports/wrir.99-4242.html
http://journalofmaps.com/student/10_01_Hardy.pdf
John Mickelson
Geospatial and Ecological Services
501 Stage Rd.
Monroe, NY 10950-3217
(845) 893-4110
[email protected]
________________________________
From: Alexandre Fadigas de Souza <[email protected]>
To: [email protected]
Sent: Wednesday, August 28, 2013 10:00 PM
Subject: [ECOLOG-L] Soil humidity from topographic data?
Dear friends,
I have a number of soil-related variables, and need to estimate soil
humidity. Would someone know how?
We have collected topographic (elevation, slope, convexity), soil (texture
and nutrients), and vegetation cover data from 85 5 x 5 m plots scattered
through a sandy coastal vegetation complex in northeastern Brazil, which
include sand dunes as well as latosols.
We did not have enough funding or time to measure soil humidity in the
filed, but our analyses would greatly benefit from an estimation of it. Do
you have an idea on how to do that?
Many thanks,
Alexandre
