Do hydraulic redistribution and nocturnal transpiration facilitate nutrient acquisition in Aspalathus linearis?

• Published in: Oecologia Vol. 175; no. 4; pp. 1129 - 1142
• Main Authors: Matimati, Ignatious, Anthony Verboom, G, Cramer, Michael D
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.08.2014; Springer; Springer Berlin Heidelberg; Springer Nature B.V
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Aspalathus - physiology; Aspalathus linearis; Biological and medical sciences; Biomedical and Life Sciences; Deep water; Deuterium; deuterium oxide; Drought; Ecology; Fertilizers; Fundamental and applied biological sciences. Psychology; General aspects; Hydraulics; Hydrology/Water Resources; irrigation rates; Life Sciences; mass flow; Moisture content; Nutrient availability; Nutrient flow; nutrients; PHYSIOLOGICAL ECOLOGY; Physiological ecology - Original research; Plant nutrition; Plant roots; Plant Roots - physiology; Plant Sciences; Plant Transpiration; Plants; roots; shrubs; Soil; Soil depth; Soil nutrients; Soil surfaces; Soil water; South Africa; stems; summer; Surface irrigation; Transpiration; South Africa; Hydraulic lift; Fynbos; Mass-flow; Cape Floristic Region; Nighttime transpiration; Night; Phytogeography; Hydraulics; Ecoregion; Biogeography; Hydraulic conductivity; Acquisition; Transpiration; Flora; Nutrient; Mass flow
• ISSN: 0029-8549; 1432-1939
• DOI: 10.1007/s00442-014-2987-6

The significance of soil water redistribution by roots and nocturnal transpiration for nutrient acquisition were assessed for deep-rooted 3-year-old leguminous Aspalathus linearis shrubs of the Cape Floristic Region (South Africa). We hypothesised that hydraulic redistribution and nocturnal transpiration facilitate nutrient acquisition by releasing moisture in shallow soil to enable acquisition of shallow-soil nutrients during the summer drought periods and by driving water fluxes from deep to shallow soil powering mass-flow nutrient acquisition, respectively. A. linearis was supplied with sub-surface (1-m-deep) irrigation rates of 0, 2 or 4 L day⁻¹ plant⁻¹. Some plants were unfertilized, whilst others were surface- or deep-fertilized (1 m depth) with Na¹⁵NO₃ and CaP/FePO₄. We also supplied deuterium oxide (²H₂O) at 1 m depth at dusk and measured its predawn redistribution to shallow soil and plant stems. Hydraulic redistribution of deep water was substantial across all treatments, accounting for 34–72 % of surface-soil predawn moisture. Fourteen days after fertilization, the surface-fertilized plants exhibited increased hydraulic redistribution and increased ¹⁵N and P acquisition with higher rates of deep-irrigation. Deep-fertilization also increased hydraulic redistribution to surface soils, although these plants additionally accumulated ²H₂O in their stem tissue overnight, probably due to nocturnal transpiration. Plants engaged in nocturnal transpiration also increased ¹⁵N and P acquisition from deep fertilizer sources. Thus, both nocturnal transpiration and hydraulic redistribution increased acquisition of shallow soil N and P, possibly through a combination of increased nutrient availability and mobility.