Browsing by Author "Dörner J"

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18O isotopic labelling and soil water content fluctuations validate the hydraulic lift phenomena for C3 grass species in drought conditions
(Elsevier B.V., 2024-02-29) Oliveira BA; López IF; Cranston LM; Kemp PD; Donaghy DJ; Dörner J; López-Villalobos N; García-Favre J; Ordóñez IP; Van Hale R
Hydraulic lift is a functional characteristic observed in some plant species, often associated with their ability to withstand drought conditions. It involves capturing water from deep soil layers and redistributing it to shallower soil layers through the plant's roots. Bromus valdivianus Phil., Dactylis glomerata L., and Lolium perenne L. may perform hydraulic lift at varying rates. Using both direct (isotopic labelling - δ18O) and indirect (soil water content sensors) techniques, the study assessed and validated the hydraulic lift under extreme drought conditions on the soil top layer (below permanent wilting point), maintaining the bottom layer at high (20–25% filed capacity [FC]) and low (80–85% FC) levels of soil water restriction. Above- and below-ground biomass growth and morpho-physiological responses were evaluated. All species displayed some degree of hydraulic lift, with significant differences observed in the isotopic analysis and soil water content (p > 0.05). This illustrates that water was redistributed from the deep to shallower soil layer and validates that the hydraulic lift phenomenon is occurring in these C3 grasses. Bromus valdivianus presented the highest δ18O values (25.05‰) and highest increases in soil water content (µ=0.00626 m3 m−3; five events). Bromus valdivianus had a dry matter ratio of approximately 4:1 (0–20cm:20–40 cm). In contrast, L. perenne and D. glomerata had approximately 6:1 and 5:1, respectively. This difference in root morphology may explain the higher rate of hydraulic lift observed in B. valdivianus relative to L. perenne and D. glomerata. This paper validates the occurrence and provides initial insights into the hydraulic lift process occurrence of temperature grass species.
Effect of Varying Dairy Cow Size and Live Weight on Soil Structure and Pasture Attributes
(MDPI (Basel, Switzerland), 2025-10) Negrón M; López IF; Dörner J; Cartmill AD; Balocchi OA; Saldivia E; Bellocchi G
Grazing systems’ production efficiency is a dynamic interaction between soil, pasture, livestock, and climate. The magnitude of the changes is related to the mechanical stress applied by the livestock and their feeding behaviour. In Southern Chile, dairy cattle present a high heterogeneity in breeds, size, live weight, and milk production. This study investigated whether cows of contrasting size/live weight can improve degraded pasture and positively modify soil (Andosol-Duric Hapludand) physical features. Three pasture types were used as follows: (i) cultivated fertilised Lolium perenne L. (perennial ryegrass) and Trifolium repens L. (white clover) mixture (BM); (ii) cultivated fertilised L. perenne, T. repens, Bromus valdivianus Phil. (pasture brome), Holcus lanatus L. (Yorkshire fog), and Dactylis glomerata L. (cocksfoot) mixture (MSM); and (iii) naturalised fertilised pasture Agrostis capillaris L. (browntop), B. valdivianus, and T. repens (NFP). Pastures were grazed with two groups of dairy cows of contrasting size and live weight: light cows (LC) [live weight: 464 ± 5.4 kg; height at the withers: 132 ± 0.6 cm (average ± s.e.m.)] and heavy cows (HC) [live weight: 600 ± 8.7 kg; height at the withers: 141 ± 0.9 cm (average ± s.e.m.)]. Hoof area was measured, and the pressure applied by cows on the soil was calculated. Soil differences in penetration resistance (PR) and macro-porosity (wCP > 50 μm) between pastures were explained by tillage and seeding, rather than as a result of livestock presence and movement (animal trampling). The PR variation during the year was associated with the soil water content (SWC). Grazing dairy cows of contrasting live weight caused changes in soil and pasture attributes, and they behaved differently during grazing. Light cows were linked to more intense grazing, a stable soil structure, and pastures with competitive species and greater tiller density. In MSM, pasture consumption increased, and the soil was more resilient to hoof compression. In general, grazing with heavy cows in these three different pasture systems did not negatively impact soil physical properties. These findings indicate that volcanic soils are resilient and that during renovation, the choice of pasture type has a greater initial impact on soil structure than the selection of cow size, but incorporating lighter cows can be a strategy to promote denser pasture swards in these grazing systems.
Effect of Water Restriction and Supplementary Nitrogen on the Growth Dynamics of Bromus valdivianus Phil
(MDPI (Basel, Switzerland), 2025-09) López IF; Rodríguez A; Cartmill AD; Dörner J; Calvache I; Balocchi O; Sanders D; Liu Y
Decreasing summer precipitation is negatively affecting global productivity of grassland plant species. This study evaluated the effect of three levels of soil plant available water [80–90% PAW-H (high), 50–60% PAW-M (medium), and 20–30% PAW-L (low), which were soil water restriction (SWR) equivalent to (v/v%) 10–20%, 40–50%, and 70–80%, respectively] and nitrogen (N 0 and 110 kg ha⁻¹) on growth and nutritional quality of Bromus valdivianus Phil. (Bv) mini-swards (MS; 125 L containers), arranged in three blocks. Total lamina length (TLL), leaf expansion rate (LER; cm d⁻¹), phyllochron (Phy) expressed as “days” and “°C day”, tiller mass (TM, g tiller⁻¹), number of live leaves (NLL), number of dead leaves (NDL), and accumulated herbage mass [AHM, g DM (dry mass) m²] were measured. Defoliation events, leaving 5 cm residual height, were carried out every 320 GDD (using a base growth temperature of 5 °C), and foliage samples for nutritive quality [DM, crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF), water-soluble carbohydrates (WSC), and metabolic energy (ME)] were collected. Reducing PAW to 20–30% decreased the AHM by 60.7%, TLL by 52.7%, LER by 50%, and TM by 50%, with significant interaction between the main effects for AHM, TLL, and LER. The addition of N increased the AHM by 31.6%, LER by 21.6%, and TLL by 19.6%. The Phy remained undisturbed by decreasing PAW and increasing the N rate. Nutritive quality was generally not statistically different for the interaction or between N levels. However, low PAW levels resulted in statistically (p < 0.05) lower ME and higher concentrations of NDF. In general, growth, AHM, and nutritional quality of Bv during the summer period were driven by PAW levels and by the availability of N. Plant available water levels of 50% to 60% at 20 cm soil depth, with the addition of N, allowed Bv to reach its highest production.