An experimental and modeling synthesis to determine seasonality of hydraulic redistribution in semi-arid region with multispecies

A key challenge in critical zone science is to understand and predict the interaction between aboveground and belowground eco-hydrologic processes. Roots play an important role in linking aboveground plant ecophysiological processes, such as carbon, water and energy exchange with the atmosphere, and the belowground processes associated with soil moisture and carbon, and microbial and nutrient dynamics. In this study, I have analyzed aboveground and belowground interaction through hydraulic redistribution (HR), a phenomenon that roots serve as preferential pathways for water movement from wet to dry soil layers. HR process is simulated by multi-layer canopy model (MLCan) and compared with relative measurements from the field to study effect of HR on different plant species where Posopis velutina Woot. (velvet mesquite) and understory co-exist and share resources. The study site is one of Ameriflux sites: Santa Rita Mesquite savanna, AZ, with a distinct dry season that indicates occurrence of HR. The model is modified to better represent Santa Rita Mesquite site where fractions of plants and soil coverage change from season to season. I analyzed how two plants share and utilize the limited amount of water by HR in both dry and wet seasons. During dry season, water moves from deep layer to shallow layer through roots and hydraulic lift (HL) occurs. During wet season, water moves from shallow layer to deep layer through roots and hydraulic descent (HD) occurs. Mesquites deposit water to deeper soil through their roots right after rain to prevent water loss due to surface evaporation. About 40% of precipitation is transferred to deep soil layer with HD and 15% of that is transported back to shallow soil layer with HL in dry season. Assuming water supplied through HL supports evapotranspiration of plants, HL supports 10% of evapotranspiration. The ratio of mesquite and understory root conductivities is an important factor that determines how two plant species interact and share resources in water-limited environment. The sensitivity analysis of root conductivities suggests that high understory root conductivity facilitates water transported by HR and increases mesquite transpiration and photosynthesis. Understory transpiration and photosynthesis show increase with HR only in dry season when water is supplied to shallow layer through HL. With low understory root conductivity, understory looses the competition for water against mesquite and show decrease in transpiration and photosynthetic fluxes when HR is allowed.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Civil Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2016

Author dc:creator

• Lee, Esther

Contributors dc:contributor

• Kumar, Praveen

• Hydraulic Redistribution

Statement dc:rights

• Copyright 2016 Esther Lee

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/93058

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/93058