Earth and Environmental Sciences

Heat stress is a major constraint for grazing livestock in hot semiarid regions and undermines the sustainability of pasture-based production, while practical on-farm adaptation options remain limited. In this study, we evaluated a low-input silvopastoral strategy as a climate-smart alternative to full-sun irrigated pastures in Brazil's semiarid region. Integrating a moderate density of native Caatinga trees into sheep paddocks created a measurably milder microclimate than a full-sun monoculture system: silvopastoral paddocks showed slightly cooler air temperatures (reductions of up to ∼1 °C at the hottest hours) and a one-point decrease in the black-globe humidity index (BGHI 86.1 vs. 87.2; p < 0.05), indicating a lower environmental heat load. Morada Nova lambs in the silvopastoral system spent about 62% of the grazing day (∼6 h 48 min) under tree shade and ∼63% of the time grazing, with clear diurnal shifts in ingestive behavior (p < 0.001 for period effects on grazing time and bite rate). Thermal mitigation was reflected in lower heart and respiratory rates, particularly around midday (system × period interactions for HR and RR, p <0.05), even though rectal temperature remained within the normal range in both systems. A canonical discriminant analysis based on only five descriptors-air temperature, BGHI, respiratory rate, time spent grazing and time spent in the sun-correctly classified 97.9% of system × time-of-day combinations (p < 0.001), providing a concise monitoring set for field diagnosis of heat stress. Overall, our results show that introducing tree shade into irrigated pastures is a low-tech, scalable and resource-efficient intervention that reduces heat stress by 1.1 BGHI points and improves animal welfare, thereby enhancing the climate resilience of small-ruminant production systems in hot semiarid environments and contributing to cleaner, more sustainable livestock production.

The application of engineered cementitious composite (ECC) in 3D concrete printing has the potential to achieve rebar-free 3D concrete printing. To improve the strength of 3D printed ECC, this study utilized polyethylene (PE) fibers to regulate the rheological and mechanical properties of the material, thereby developing a 3D printable high-strength ECC (3DP-HSECC) and systematically investigated the rheological properties, mechanical characteristics and flexural behaviors of the 3DP-HSECC. The addition of PE fiber increases the viscosity- enhancement effect of fibers on the matrix, and thus achieves favorable printability and shape-retention capability. The results reveal that the compressive strength of 3DP-HSECC exhibits anisotropy, which is influenced by fiber orientation and interface properties of 3DP-HSECC. The highest compressive strength is observed when specimens are loaded perpendicular to the interface, demonstrating 21.3% and 78.1% increases compared to mold-cast specimens and printed specimens loaded parallel to the interface, respectively. The 3DP-HSECC beams show coordinated deformation under flexural loading with no significant horizontal interlayer slippage. Numerical simulations of 3DP-HSECC under compression and flexure demonstrate well agreement with experimental result. Parametric analysis indicates that an interlayer bond strength exceeding 3.0 MPa has the minimal influence on the flexural performance of printed 3DP-HSECC beams. The findings provide a design foundation for the application and promotion of 3DP-HSECC.

Fiber-reinforced polymer reinforced concrete columns (FRP-RC columns) have attracted increasing attention in recent years. However, conventional FRP bars remain susceptible to compressive buckling. Building on previously developed FRP-confined GFRP bars with high compressive strength, this study investigates concrete columns incorporating these bars as longitudinal reinforcement to mitigate this issue. Axial compression tests were carried out on 26 FRP-RC columns to examine the effects of GFRP bar type, GFRP bar diameter, and spiral pitch. The results indicate that, compared with columns reinforced with conventional GFRP bars, those incorporating FRP-confined GFRP bars showed improved ultimate load capacity and ductility, with maximum increases of 18.0% in strength and 18.1% in ductility. The FRP-confined GFRP longitudinal bars also helped reduce the risk of longitudinal bar buckling and contributed up to 36% of the overall axial load capacity. This contribution was strongly influenced by the confinement provided by the FRP spirals. In addition, existing load capacity and confinement models were reviewed, and the experimental results indicated that the model proposed by Ye et al. provided suitable predictions for the FRP-confined GFRP bar-reinforced concrete columns tested in this study.