Rainfall Determines Shallow Soil Seepage in a Piedmont Summer Pasture of Alpine Meadow on the Northeastern Qinghai—Tibetan Plateau

Soil seepage is an important component used for quantifying hydrological processes that remains unclear in high-altitude alpine meadows. Shallow soil seepage was continuously measured using an auto-logged micro-lysimeter (diameter = 30 cm, depth = 30 cm) from July 2018 to June 2019 in a piedmont summer pasture of alpine meadow on the Northeastern Qinghai–Tibetan Plateau. The results showed that all the shallow soil seepage events occurred during the non-frozen period from April to September and that the cumulative amount was 106.8 mm, representing about 1/5 of the annual precipitation. The maximum and minimum monthly soil seepage were 30.7 mm in September and 1.0 mm in April, respectively. The boosted regression trees (BRT) model’s area under the curve averaged 0.92 and revealed that the daily half-hour rainfall frequency, volumetric soil water content, and air temperature played significant roles in the daily soil seepage probability, with the cumulative relative contribution of 68%. The stepwise linear regression analysis showed that the rainfall amount accounted for 59% of the variation in the daily amount of soil seepage. The monthly soil seepage was found to be significantly correlated with the monthly rainfall frequency (r = 0.86, p = 0.005). Our results highlighted that rainfall, including its amount and frequency, was the key determinant of the probability and amount of shallow soil seepage in the piedmont summer pasture of alpine meadows. These findings will be helpful for improving predictions of the water budgets of piedmont alpine meadows.

Analysis on the Temporal and Spatial Characteristics of the Shallow Soil Temperature of the Qinghai-Tibet Plateau

Shallow soil refers to the soil layer within 50 cm underground. Shallow soil temperature (ST) affects many processes that occur in the soil. Therefore, the study of shallow ST is of great significance in understanding energy, hydrological cycles and climate change. This work collected the observational data from 141 meteorological stations on the Qinghai-Tibet Plateau from 1981 to 2020, analyzed the ST as well as its temporal and spatial change characteristics at different levels. The results show that: 1) The shallow ST has a gradually increasing trend from north to south, from west to east. From the perspective of time characteristics, the increasing trend is obvious. The temperature increase of 0–20 cm (the surface layer of the shallow soil) is roughly the same. The average annual is 9.15–9.57 ℃, the interdecadal variabilities are 0.49–0.53 K/10a. The average annual of 40 cm (the bottom layer) is 8.69 ℃, the interdecadal variability reaches by 0.98 K/10a; 2) Judging from the 12 regions of 20 cm, the temperature increase trend is obvious, but there are certain regional differences. The average value ranges from 4.3 ℃ (region 4, Qaidam Plateau) to 18.1 ℃ (region 10, Southeast Qinghai-Tibet Plateau), the difference is nearly 14 K. The standard deviation ranges from 0.38 K (region 10) to 0.82 K (region 11, Northern Qiangtang Plateau); 3) The results of the reanalysis data are lower than the observational data. This work is significant for understanding the characteristics of the ST evolution and the land-atmosphere interaction on the Qinghai-Tibet Plateau.

Water Source of Six Woody Plants in Different Habitats on Desertified Land of Ordos Plateau, Semi-Arid China

Water and soil erosion and sandy desertification are two mainly land desertification types on eastern and southern Ordos Plateau, north China. Hippophae rhamnoides, Armeniaca sibirica and Pinus tabuliformis are three woody plants for soil and water conservation on loess slope. Sabina vulgaris, Artemisia ordosica and Salix psammophila are three shrubs for sand control on sand dune. Water source of six woody plants were investigated by stable isotope technology. The results showed that the δ18O of shallow soil water was similar to that of rainwater in July and September in two habitats. Both of six woody plants in two habitats mainly used shallow soil water in May. However, three shrubs on sand dune mainly used both of shallow and deep soil water in July and September. Three woody plants on loess slope mainly used rainwater or deep soil water in July and September. Therefore, six woody plants utilized different depths of soil water or rain water based on their availability in different seasons, which is an adaptive strategy to the semiarid climate on Ordos Plateau.

Modified Model for Shallow Soil Strength Recovery Calculation during Set-Up Periods of Jetted Conductor—A Case Study of Equatorial Guinea Bay Deep-Water Drilling

Jetted conductor setting depth is crucial for deep-water drilling. This paper presents an innovative method for determining the shallow soil resistance strength recovery factor based on the field data of Equatorial Guinea bay. It shows that the soil strength recovery factor of Equatorial Guinea bay is lower than that of the Gulf of Mexico. The conductor setting depth calculation referring to other place will have a high risk of wellhead sinking. According to the newly established designing charts, the conductor setting depth was recommended for the S1 well. Each preferred set-up period requires a specific setting depth. If the chosen set-up period is 2 days, the expected setting depth of a 36″ conductor should be 250 ft (76.2 m) and, similarly, 295 ft (89.9 m) for a 30″ conductor. The relationship between set-up period and surface conductor setting depth is established as well. Wellhead landed load appears to be the crucial factor for determining the conductor setting depth. The rationality of the newly developed shallow soil strength recovery model for the Equatorial Guinea deep-water block was also confirmed by the field data.

Redistribution process of precipitation in ecological restoration activity of Pinus sylvestris var. mongolica in Mu Us Sandy Land, China

Precipitation was the most important water resource in semi-arid regions of China. The redistribution of precipitation among atmospheric water, soil water and groundwater are related to the land surface ecological system sustainability. The study took widely replanted Pinus sylvestris var. mongolica (PSM) in Mu Us Sandy Land (MUSL) as a research object and monitored precipitation, soil moisture, sap flow, and deep soil recharge (DSR) to find out moisture distribution in shallow soil layer. Results showed that the restoration process of PSM in MUSL changed the distribution of precipitation. Precipitation was intercepted in shallow soil, evapotranspiration increased, and DSR significantly decreased, resulting in up to 466.94 mm of precipitation returning to the atmosphere through evapotranspiration in 2016. Vegetation increased soil water storage (SWS) capacity, with maximum SWS in PSM plot and bare sandy land (BSL) being 260 mm and 197 mm per unit horizontal area, respectively in 2016. DSR decreased from 54.03 % of precipitation in BSL to 0.2 % of precipitation in PSM in 2016. Infiltration was not only intercepted by PSM ecosystem, resulting in a time lag, but was also affected by soil temperature, and the infiltration rate in the BSL plot was 11 times of that in the PSM plot from August to September in an annual base. SWS decreased 16 mm and 7.58 mm per unit horizontal area over a one-year period (from March to October) in 2017 and 2019, respectively. The PSM annual sap flow was maintained at a relatively constant level of 153.98 mm/yr. This study helps understand the role of precipitation-induced groundwater recharge in the process of vegetation restoration in semi-arid regions and explains the possible causes of PSM forest degradation. It is necessary to reduce PSM density to allow adaptation to extreme drought in the future.

Comparative Study of Soil Index Properties of Gudu Sokoto State And Oworoshoki Area Lagos State, Nigeria.

The comparative study of the soils sample collected from Gudu and Oworoshoki area, Sokoto state and Lagos State was carried out to compare the index properties of soil at shallow soil deposit. The Global Positioning System (GPS) was used to locate the coordinates of the site. Shallow soil samples (disturbed and undisturbed) at different depths (1m, 2m and 3m) were collected from both study areas (Gudu and Oworoshoki). The disturbed samples were collected using hand trowel, digger, hoe and polythene bags while the undisturbed samples were collected using short pipes (samplers) by stroking each pipe into the ground completely with a hammer at each depth. Disturbed and undisturbed soils collected at different shallow depths (1m, 2m and 3m) were taken to the laboratory for natural moisture content, specific gravity, sieve analysis, Atterberg limits and unit weight test. Empirical equations were used for analyzing the soil samples and AASTHO System of classification was used for classifying the soil samples. The results of the test on Gudu soil samples has shown that the soil sample collected at depth 1.0m and 2.0m are nonplastic materials and were classified according to AASHTO standard as A-3 and sample at depth 3.0m as A-4 which is silty soil while Oworoshoki soil samples has shown that Soils from depth 1.0m, 2.0m and 3.0m are nonplastic (NP) because the Plastic Index (PI = 0) is zero and the soil samples are classified as A – 3 according to AASHTO standard.