Differential response of plant water consumption to rainwater uptake for dominant tree species in the semiarid Loess Plateau

Whether uptake of rainwater can increase plant water consumption in response to rainfall pulses requires investigation to evaluate the plant adaptability, especially in water limited regions where rainwater is the only replenishable soil water source. In this study, the water sources from rainwater and three soil layers, predawn (Ψpd), midday (Ψm) and gradient (Ψpd−Ψm) of leaf water potential, and water consumption in response to rainfall pulses were analyzed for two dominant tree species, Hippophae rhamnoides and Populus davidiana, in pure and mixed plantations during the growing period (June–September). In pure plantations, the relative response of daily normalized sap flow (SFR) was significantly affected by rainwater uptake proportion (RUP) and Ψpd−Ψm for H. rhamnoides, and was only significantly influenced by Ψpd−Ψm for P. davidiana (P < 0.05). Meanwhile, the large Ψpd−Ψm was consistent with high SFR for H. rhamnoides, and the small Ψpd−Ψm was consistent with the low SFR for P. davidiana, in response to rainfall pulses. Therefore, H. rhamnoides and P. davidiana exhibited sensitive and insensitive responses to rainfall pulses, respectively. Furthermore, mixed afforestation significantly enhanced RUP, SFR, and reduced the water source proportion from the deep soil layer (100–200 cm) for both species (P < 0.05). The SFR was significantly influenced by RUP and Ψpd−Ψm for both species in the mixed plantation. Lower Ψm and higher Ψpd were adopted by H. rhamnoides and P. davidiana in mixed plantation, respectively, to enlarge Ψpd−Ψm, enhance rainwater uptake, and decrease water source competition from the deep soil layer. These results indicate that mixed afforestation enhanced the influence of rainwater uptake to water consumption after rainfall pulse, regardless of sensitivity to rainfall pulses. This study provides insights into suitable plantation species selection and management considering the link between rainwater uptake and consumption in water limited regions.

Analysis of settlements in piled raft systems founded in soft soil under consolidation process

In piled raft systems (PRSs), the piles are used to support load or to control settlements. These systems, when founded in soft soils that are then consolidated by loads or subsidence processes, can induce negative friction in the piles and other phenomena related to variations in the distribution of load or settlements. This paper presents the results of physical modeling in a geotechnical centrifuge capable of different distributions of piles under a raft. As a result, the influence of consolidation and extraction of water from a deep soil layer on the behavior of the PRS model was analyzed. It was determined that the processes associated with the extraction of water from the deep soil layer induce larger settlements. A separation between the raft and the soil is possible, as well as a change in the behavior of the PRS.

Effect of Weed Treatment on Cereal Yield in Direct Seeding: A Challenge Between Soil Pollution and Seeds Quality

The study was conducted at Technical Institute of Cereals (ITGC- Setif) during the years 2014-2018 for understanding the effect of weed treatment in direct seeding on cereal yield, soil and seeds quality. Two horizons were considered: horizon one (0 less than H1 less than 20 cm) and horizon two (H2 less than 20 cm) and four herbicide doses were applied: D1 =1080g ha-1, D2= 900g ha-1, D3= 720 g ha-1 and D4= 540 g ha-1. The yield results depended on the herbicide doses applied before seeding. The highest yield responded to the highest dose of herbicide applied (1080g ha-1). Study indicated that glyphosate reached soil during weed treatment and transferred in deep soil layer and to harvested seeds. Half-live values (DT50) of glyphosate found under field conditions were high.

Sustainability of Abandoned Slopes in the Hill and Gully Loess Plateau Region Considering Deep Soil Water

Soil desiccation of the deep soil layer is considered one of the main limiting factors to achieving sustainable development of ecosystems in the hill and gully Loess Plateau region. In this study, slope croplands were selected as the control, and deep soil water was studied on abandoned slopes, including natural abandoned slopes, Robinia pseudoacacia plantations, and Caragana korshinskii plantations. Then, we explored deep soil water characteristics of different vegetation types and slope aspects and the variation tendencies of deep soil water at different recovery stages. The results showed that there were no significant differences in deep soil water content between sunny and shady slopes, and thus, slope aspect was not the key impact factor affecting deep soil water. Deep soil water content on R. pseudoacacia plantations and C. korshinskii plantations was lower than that on natural abandoned slopes; there were no significant differences in soil water content between the natural abandoned slopes and slope croplands. Soil desiccation did not exist on natural abandoned slopes; thus, natural vegetation restoration is an appropriate way to achieve a sustainable ecosystem with respect to deep soil water. In contrast, soil desiccation intensified until it was difficult for vegetation to obtain available water in the deep soil layer on the plantations; soil desiccation began to appear at the 11–20-year stage, and it became increasingly severe until the deep soil water was close to the wilting coefficient at the ≥30-year stage on R. pseudoacacia plantations. Deep soil water was rapidly consumed, and soil desiccation began to appear at the 1–10-year stage and then was close to the wilting coefficient in the later stages on C. korshinskii plantations. According to the results, the plantations needed to be managed in a timely manner to prevent or reduce soil desiccation.

Research on the Vibration Attenuation Rules and Wave Propagation Law under Impacting Drill on the Deep Soil Layer

A field test is carried out to study the effect of vibration while treating foundation using vibroflotation method in the deep soil layer in Zhengzhou, China. The vibration attenuation rules and wave propagation rules in different formations caused by different numbers of drills are analyzed. Evaluate the influence on the adjacent buildings. The result shows that the vibration will be generated in foundation obviously in the process of construction using the method. Vibration force, impact frequency and site soil are important influence factors on ground vibration attenuation. The analysis reveals that the maximum vertical acceleration attenuation velocity was much greater in near area than that in the relative far area. The waves caused by vibration propagate in two ways: (1) surface wave is generated on the wall of drill hole and propagated to the ground surface, and attenuated in a certain distance (<8m); (2) shear wave was generated and propagated in the impacting formation and attenuated from the deep formation to the ground surface. Vibration amplitude is mainly distributed in the low frequency range in the areas which far away from vibration source and in the silt layer near the ground surface.