Document: RON-3-19-5

Hydraulic lift and uptake of water and nutrients.

RYEL, R.J.* and M.M.CALDWELL

Utah State University, USA ¹

Abstract:
Hydraulic lift involves water uptake from relatively moist soil layers, usually at depth, and release of this water from roots in drier soil layers during times when stomatal conductance is very low, such as at night. The following morning most of this released water is apparently taken up and passes into the transpiration stream. This process of temporary storage of water in drier soil layers allows roots in moist layers to absorb water both night and day and to facilitate overall water uptake under conditions of high evaporative demand. Yet, does this process result in a redistribution of water in the soil profile over periods of weeks and months and, if so, what are the implications for both water and nutrient uptake? Furthermore, how are these processes influenced by vertical rooting depth distributions? Recent modeling efforts suggest that a substantial longer-term redistribution of water does occur and it has several implications for both water and nutrient acquisition as the soil profile is depleted of water during drying cycles. Under some circumstances, hydraulic lift may be critical in prevented an extreme desiccation of the upper soil layers. Nutrient uptake in drying soil becomes rapidly diffusion limited and hydraulic lift can theoretically prolong nutrient uptake by several weeks. Root depth distributions and recharge of water at depth may also play important roles in how effectively hydraulic lift redistributes water in the profile.

Keywords: hydraulic lift, plant water relations, root systems

This abstract is being presented at: 9:55 AM in session:
Symposium # 9: The Water Limitation: Issues in Plant, Community, and Ecosystem Water Use.