Sagebrush carrying out hydraulic lift enhances surface soil nitrogen cycling and nitrogen uptake into inflorescences

Abstract

Plant roots serve as conduits for water flow not only from soil to leaves but also from wetter to drier soil. This hydraulic redistribution through root systems occurs in soils worldwide and can enhance stomatal opening, transpiration, and plant carbon gain. For decades, upward hydraulic lift (HL) of deep water through roots into dry, litter-rich, surface soil also has been hypothesized to enhance nutrient availability to plants by stimulating microbially controlled nutrient cycling. This link has not been demonstrated in the field. Working in sagebrush-steppe, where water and nitrogen limit plant growth and reproduction and where HL occurs naturally during summer drought, we slightly augmented deep soil water availability to 14 HL+ treatment plants throughout the summer growing season. The HL+ sagebrush lifted greater amounts of water than control plants and had slightly less negative predawn and midday leaf water potentials. Soil respiration was also augmented under HL+ plants. At summer's end, application of a gasbased 15 N isotopic labeling technique revealed increased rates of nitrogen cycling in surface soil layers around HL+ plants and increased uptake of nitrogen into HL+ plants' inflorescences as sagebrush set seed. These treatment effects persisted even though unexpected monsoon rainstorms arrived during assays and increased surface soil moisture around all plants. Simulation models from ecosystem to global scales have just begun to include effects of hydraulic redistribution on water and surface energy fluxes. Results from this field study indicate that plants carrying out HL can also substantially enhance decomposition and nitrogen cycling in surface soils.rhizosphere | flowering | seed production

Diel plant water use and competitive soil cation exchange interact to enhance NH4 + and K+ availability in the rhizosphere

“…S7 and S8). This sensitivity to plant-driven flow supports the body of literature arguing that plant control of water use, both rates of daytime transpiration and nighttime water use (i.e., nighttime transpiration and nighttime root-water release), can modify nutrient availability within the rhizosphere and alter plant nutrient uptake (e.g., Snyder et al 2008;Cramer et al 2009;Cardon et al 2013;Cernusak et al 2011;Matimati et al 2014;Graciano et al 2016). The second implication of Fig.…”

“…A constant water potential of −0.5 MPa was prescribed at the bulk-soil boundary (Ψ sb ) and a time-varying water potential was prescribed at the root-soil interface (Ψ sr ), mimicking daily oscillations in soil water potential measured in natural ecosystems (e.g., Meinzer et al 2004;Cardon et al 2013) and establishing unsaturated, diel water-flow across the soil domain. This approach assumes no competition for water between neighboring roots and captures flow conditions with the bulk soil water potential poised at an ecologically relevant point.…”

Variation in physicochemical and biochemical soil properties among different plant species treatments early in the restoration of a desertified alpine meadow

“…Previous studies have indicated that plant species significantly affect soil water and nutrient availability due to having different hydraulic lift capacities (Cardon, Stark, Herron, & Rasmussen, ), input quantities and qualities of litter and root exudates (Haichara, Santaella, Heulin, & Achouak, ; Tsunoda & van Dama, ), and directions and strengths of the rhizosphere priming effect (Finzi et al, ; Huo, Luo, & Cheng, ). Similarly, this research also showed that many soil physicochemical properties differed significantly among the three plant species.…”

Challenging the maximum rooting depth paradigm in grasslands and savannas

“…Additionally, HR may play important roles for increasing nutrient availability in surface soil layers (Cardon et al . ). For many grassland systems, nutrient availability is highest in the surface soil layers (Ajwa, Rice & Sotomayor ), with mineralization rates correlated with changes in soil moisture (Stanford & Epstein ).…”