Hydraulic lift and water scarcity: Journal Club with Tinashe Mawodza

Many ways of improving crop yields can be discovered when scientists  get to grips with the underlying processes in plants. Grantham Scholar Tinashe Mawodza introduced our students to a process known as ‘hydraulic lift’. In this blog, he explains how it could help plants in regions where water is scarce.

This week’s paper

‘Hydraulic lift: a potentially important ecosystem process’ by J. L. Horton and S. C. Hart

Tinashe Mawodza
Tinashe Mawodza

This week’s Journal Club delved into a potentially important ecosystem process that is known to be carried out by many deep rooted plants in their quest for better survival in areas where water is scarce. The review paper we looked at highlighted the progress that has been made in terms of better understanding hydraulic lift, a process that enables some plants to passively extract water from deeper soil horizons, re-depositing it into shallower soil regions bearing a lower water potential (?w) where its finer roots are located.

We discussed the potential for exploiting of hydraulic lifting plants to encourage plants to grow in deserts and arid areas. These plants as exemplified by Prosopis tamarugo which grows in the Atacama desert and are able to extract water from deep in the soil profile – these plants are likened to a biological ‘water pump’ that is able to passively access water deep underground and bring it to near the Earth’s surface. The group asked questions about why this ecosystem process hasn’t been fully exploited across the arid world. This may be due to the fact that there is a need for scarce extensive irrigation to initially establish these plants.

The currently unclear role of hydraulic lifters in making nutrients more available to themselves and other plants was also considered as a potentially beneficial role hydraulic lifters could perform in many dry areas. Hydraulic lifters’ potential for hydrological support of many other plants such as grasses could support an additional active carbon dioxide sink in these dry areas, which would enhance the environmental functionality of deserts. Other terrestrial organisms such as soil micro-flora could also benefit from the increased soil moisture availability.

Apart from the hydraulic lift carried out by many hardy trees and shrubs, some crops of agricultural value (eg, Medicago sativa – alfalfa) have also been shown to hydraulically lift water to improve the efficiency of their photosynthesis. The limitation with many agricultural crops, however, is usually their shallower reaching roots which are often not deep enough to tap into water tables at the depths of arid areas. The hydraulic lifting ability of the drought resisting drumstick tree Moringa oleifera was also discussed, as it is used extensively as a natural nutritional supplement in the developing world.

Hydraulic lifting may also come at a cost however, as highlighted by an invasive species, Eucalyptus, native to Australia, which has the potential to substantially lower the water table, possibly putting wetland ecosystems at risk of eradication. To others however, this species of trees may actually be a saving grace as its cultivation may reduce the risk of flooding where wetlands have been encroached by human settlement as a result of population growth. These rapidly growing trees may also provide an income to impoverished developing communities through the sale of the timber they produce, as well as giving governments’ carbon credits.

In conclusion, our group thought the process of hydraulic lift was an interesting one that had the potential to improve the arid world, but more research needs to be carried out in order to fully realise its benefits.