How does soil structure affect K values? How are they related?
Soil structure and aggregate stability will have a large impact on the hydraulic conductivity values. Depending on the type of soil structure that is formed and the strength of that structure you will see a larger development of macropores within the soil which will have the ability to transmit more water than if the soil had poor structure or no structure.
How would you measure horizontal hydraulic conductivity in field conditions? How would you disaggregate the horizontal component of hydraulic conductivity form the vertical one?
Soil structure and aggregate stability will have a large impact on the hydraulic conductivity values. Depending on the type of soil structure that is formed and the strength of that structure you will see a larger development of macropores within the soil which will have the ability to transmit more water than if the soil had poor structure or no structure.
How would you measure horizontal hydraulic conductivity in field conditions? How could you disaggregate the horizontal component of hydraulic conductivity from the vertical one?
This depends on whether you are measuring saturated or unsaturated hydraulic conductivity. It can be difficult to try and do this for saturated hydraulic conductivity in the field. In theory, if you took a sample from the field and measured this in the lab, horizontal vs. vertical should be the same in terms of hydraulic conductivity. Hydraulic conductivity is independent of whether the flows are vertical or horizontal because these components are corrected for. If you want to measure unsaturated hydraulic conductivity in the field and look at how it changes in the horizontal vs. vertical position, this could potentially be done with tensiometers and water content sensors positioned in a grid to look at the movement of water and change in water potential.
What influence do high soil temperatures associated with forest fires have on short term unsaturated conductivity?
Because of the hydrophobicity effect from the high temperatures associated with forest fires, I expect you would see a significant impact on the unsaturated hydraulic conductivity of the soil. There are experts who have done work in this area. Researchers at the US Forest Service would be a great sounding board for this question. Pete Robichaud, in particular, might have some thoughts on this topic.
Lab K2 measurements move from the bottom to the top. Is Ks similar if water goes from the top to the bottom of a sample?
As long as the calculations are done correctly there shouldn’t be a difference if water is percolated from the bottom or the top of the sample.