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"Loess Plateau"
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HIGH QUALITY DEVELOPMENTAL APPROACH FOR SOIL AND WATER CONSERVATION AND ECOLOGICAL PROTECTION ON THE LOESS PLATEAU
Analyse the effects of ecological management measures undertaken so far. Point out the main problems that confront effective ecological management. Suggest some measures to guide ecological management and high-quality development. Develop some models to improve the quality of clear waters and green mountains. Provide scientific and technological support for green and eco-friendly development. The Loess Plateau is the core area in the Yellow River basin for implementing environmental protection and high-quality development strategies. A series of ecological projects has implemented aimed at soil and water conservation and ecological management on the Loess Plateau over the past 70 years. The effects of the ecological projects are apparent mainly through a marked increase in vegetation cover, controlled soil erosion and reduced flow of sediment into the Yellow River, continual optimization of the industrial structure and increased production from arable land, poverty alleviation and greater prosperity, and optimal allocation of space for biological organisms. Major problems have also been analyzed in ecological management including the fragile ecosystem of the region, maintaining the stability of vegetation, lower agricultural productivity and continued risk from natural disasters. Some suitable schemes and models have been developed for the coordinated development of the region through research and demonstration, striking the optimum balance between rural industry and ecology, and increased regional capacity to supply high-quality ecological products. Countermeasures to address the problems are suggested to guide ecological management and high-quality development in the future.
Journal Article
Towards a Rural Revitalization Strategy for the Courtyard Layout of Vernacular Dwellings Based on Regional Adaptability and Outdoor Thermal Performance in the Gully Regions of the Loess Plateau, China
In the context of the Chinese rural revitalization strategy, the unique residential characteristics of local vernacular dwellings formed by profound historical and cultural accumulation, climate characteristics, and residential lifestyle have undergone profound change in the gully regions of the Loess Plateau. Accordingly, the contradictions of traditional vernacular dwelling protection, increasing living requirements, and ecological protection have intensified. In this paper, with the aim of optimizing courtyard layout for vernacular dwellings, the thermal performance and regional adaptability of different courtyard layouts were analyzed using Ladybug and Honeybee tools. According to the thermal simulation within the courtyard, the current optimal layout type was determined, and then, several ecological optimization designs were proposed for the further improvement of it. The results revealed that the improved vernacular dwelling model has better regional adaptability, which corresponds to the local living culture and living habits, saves land resources, and provides a better thermal comfort performance. This research not only has a positive function for the protection of local architectural culture, but also plays an essential role in improving residents’ living comfort and living standards. We hope that the research results are meaningful and can be used as a reference for future rural construction in the Loess Plateau.
Journal Article
Characterizing magnetic mineral assemblages of surface sediments from major Asian dust sources and implications for the Chinese loess magnetism
Eolian dust plays an important role in the Earth’s climate system. Environmental magnetism has been widely used to trace dust variations at different spatial and temporal scales. However, the magnetic properties of sediments from key dust sources have not been well determined. In this study, surface samples from potential dust sources in inner Eastern Asia were systematically investigated. Our results indicate that ferrimagnetic and antiferromagnetic minerals are both present in surface sediments and that they have broad grain size distributions. Ferrimagnetic components are dominated by partially oxidized coarse-grained (pseudo-single domain and multi-domain) lithogenic magnetite particles with minor contributions from pedogenic fine-grained (single domain and superparamagnetic) particles. Antiferromagnetic hematite can be classified into three groups in terms of diffuse reflectance spectroscopy (DRS) band positions (
P
560 nm
,
P
545 nm
, and
P
535 nm
, where numbers indicate the DRS band wavelength for hematite). The first group (
P
560 nm
) is the coarse-grained hematite of lithogenic origin and is mostly confined to western China. The
P
535 nm
group is of pedogenic origin. The
P
545 nm
group is an intermediate phase that is present both in surface samples from the source regions and in loess. Therefore, the
P
545 nm
and
P
535
nm
groups are related to eolian inputs to the Chinese Loess Plateau and pedogenic processes, respectively. In addition, significant differences exist between the magnetic properties of eolian material from sources and depositional regions due to gravitational sorting. These insights provide strong constraints on interpretation of dust signals recorded by the Chinese loess and marine sediments from the North Pacific Ocean.
Journal Article
Exploring How Soil Moisture Varies with Soil Depth in the Root Zone and Its Rainfall Lag Effect in the Ecotone from the Qinghai–Tibetan Plateau to the Loess Plateau
Focusing on the ecotone from the Qinghai–Tibetan Plateau to the Loess Plateau (QPtoLP), this study firstly constructs a retrieval model of soil moisture in various depth layers based on multi-source remote sensing data by using the two-source energy balance (TSEB) model and soil–vegetation–atmosphere transfer (SVAT) model. And then, it uncovers how the soil moisture changes across various depths in the root zone and discusses the lagging effect of rainfall. This research indicated that the correlation between the retrieved soil moisture and field-monitored values in various depth layers ranged from 0.720 to 0.8414, demonstrating that it is suitable for the retrieval of soil moisture at various depths in the study area. During the growing season, soil moisture experienced a slight decrease from mid-May to mid-June, followed by a partial recovery in mid-June. After a dry spell in July, the soil moisture reached its lowest point, but surface and deep soil moisture levels rebounded to above 0.2 and 0.1 cm3/cm3, respectively, by mid-August. Spatially, the soil moisture was higher in the southern region, characterized by dense human activities, and lower in the northern region, which is dominated by alpine grasslands. Comparing different depths, the soil moisture at a 0–5 cm depth was generally the highest most of the time, except in July, when the 35–50 cm depth had the highest value. Additionally, the surface soil moisture at a 0–5 cm depth indicated frequent fluctuations at elevations above 4000 m. As the soil depth increases, the rainfall lag effect becomes more pronounced, and the lag effect in the 35–50 cm soil layer is three days.
Journal Article
Sapflow-Based Stand Transpiration in a Semiarid Natural Oak Forest on China’s Loess Plateau
The semi-arid region of China’s Loess Plateau is characterized by fragile ecosystems and a shortage of water resources. The major natural forest type in this region is the secondary forest with the flora dominated by the Liaodong oak (Quercus liaotungensis Koidz.). To understand its transpiration water use in relation to environmental factors, we applied Granier-type thermal dissipation probes to monitor stem sap flows of 21 sample trees, representing different classes of diameter at breast height in a permanent plot. The stem- and stand-scale transpiration values during the 2008–2010 growing seasons were estimated using measurements of sap flux densities and corresponding sapwood areas. The dominant factors affecting stand-scale transpiration varied with time scales. Daily stand transpiration correlated with daily solar radiation and daytime average vapor pressure deficit. Seasonal and interannual changes in stand transpiration were closely related to leaf area index (LAI) values. No obvious relationship was observed between monthly stand transpiration and soil moisture or precipitation during the period, probably as a result of both the hysteretic effect of precipitation on transpiration, and changes in LAI throughout the growing season. Stand transpiration during the three growing seasons ranged from 75 to 106 mm, representing low to normal values for the semi-arid forest. The proportion of transpiration by oak trees in the stand was stable ranging from 60% to 66% and corresponded to their basal area proportion of approximately 59%. The results suggest that the natural forest consisting mainly of oak trees is in a formal stage of forest development that maintains a normal magnitude of annual water consumption.
Journal Article
Spatial differentiation of the leaf area index in forests in ecological transition zones and its environmental response
The leaf area index (LAI) is a crucial vegetation parameter that characterizes leaf sparsity and canopy structure, and the study of the spatial distribution pattern of the forest LAI and its environmental response can help to reveal the adaptive capacity of forest vegetation to climate change in semiarid areas. In this paper, a remote sensing inversion model of the LAI, which pertains to the forest ecosystem of Xinglong Mountain in the transition zone between the Qinghai‒Tibet Plateau and Loess Plateau, was established by combining an optical instrumentation method, a remote sensing inversion method, and a generalized additive model (GAM). The results showed that (1) the Meris terrestrial chlorophyll index (MTCI) linear regression model provided the greatest explanatory power for the LAI in the Xinglong Mountain forest, with R2 = 0.88 and RMSE = 0.32. (2) The LAI was influenced mainly by the altitude, slope, profile curvature, aspect, planform curvature, temperature, precipitation, and evapotranspiration. According to the single-factor GAM, altitude (R2 = 0.43) explained most of the total variation in the LAI, followed by precipitation (R2 = 0.36). According to the multifactor GAM, the above influencing factors could explain 84.2% of the total variation in the LAI, which was significant (P < 0.001). (3) Interaction analysis revealed that the LAI was significantly influenced by the interaction between topographic and meteorological factors (P < 0.001). It was revealed that the topography of Xinglong Mountain is fragmented, the vertical band spectrum of vegetation is notable, and the forest LAI exhibits high spatial heterogeneity under the interaction between topographic and meteorological factors, reflecting the environmental response mechanism of vegetation growth in forest ecosystems in ecological transition zones.
Journal Article
Loess Thickness Variations Across the Loess Plateau of China
The soil thickness is very important for investigating and modeling soil-water processes, especially on the Loess Plateau of China with its deep loess deposit and limited water resources. A digital elevation map (DEM) of the Loess Plateau and neighborhood analysis in ArcGIS software were used to generate a map of loess thickness, which was then validated by 162 observations across the plateau. The generated loess thickness map has a high resolution of 100 m × 100 m. The map indicates that loess is thick in the central part of the plateau and becomes gradually shallower in the southeast and northwest directions. The areas near mountains and river basins have the shallowest loess deposit. The mean loess thickness is the deepest in the zones with 400–600-mm precipitation and decreases gradually as precipitation varies beyond this range. Our validation indicates that the map just slightly overestimates loess thickness and is reliable. The loess thickness is mostly between 0 and 350 m in the Loess Plateau region. The calculated mean loess thickness is 105.7 m, with the calibrated value being 92.2 m over the plateau exclusive of the mountain areas. Our findings provide very basic data of loess thickness and demonstrate great progress in mapping the loess thickness distribution for the plateau, which are valuable for a better study of soil-water processes and for more accurate estimations of soil water, carbon, and solute reservoirs in the Loess Plateau of China.
Journal Article
Occurrence and Health Implication of Fluoride in Groundwater of Loess Aquifer in the Chinese Loess Plateau: A Case Study of Tongchuan, Northwest China
This study was carried out to delineate the occurrence and spatial distribution of groundwater fluoride in a loess area of China and to determine the geochemical and anthropogenic factors that influence its concentration. Water quality was assessed for drinking purpose by comparing with the national and WHO drinking water guidelines, and the impacts of fluoride on human health were also quantified using the health risk assessment model recommended by the USEPA. The results demonstrate that groundwater in the study area is slightly alkaline in nature, and its quality is generally good except slightly excessive TDS, TH, Na
+
, F
−
, and nitrate at some local locations. High-fluoride groundwater is mainly distributed in the southeast part of the study area, which is in accordance with the groundwater flow direction in this area. Groundwater fluoride is mainly of natural origin and is dominantly controlled by natural factors such as pH, specific hydrochemical environment, ion exchange, and saturation state of minerals. Fluoride contributes the most to the total health risk in the present study. Children are at higher health risk than adults in this area. Establishing central water supply system and rainwater harvesting system are suggested to guarantee safe drinking water supply in this area.
Journal Article
Joint analysis of changes in temperature and precipitation on the Loess Plateau during the period 1961–2011
The Loess Plateau is particularly sensitive to climate change owing to its fragile ecological environment and geographic features. Here, we present a comprehensive analysis of the joint probabilistic characteristics and tendencies for bivariate and trivariate precipitation and temperature indices across the plateau, based on copula theory. The results show that the southeast region of the plateau had a higher potential for flooding: the 10-year return levels for the number of days with heavy and very heavy precipitation (R10mm, R20mm) and for the maximum 5-day precipitation value (RX5day) were higher in this region. The northwest region of the plateau, however, had a higher potential for drought, as reflected in the high and increasing 10-year return levels for the number of consecutive dry days (CDD) and the number of days with low precipitation (R1mm). In a joint analysis of precipitation indices, large areas of the Loess Plateau showed a relatively high risk of concurrent extreme precipitation events. However, the risk of concurrent extreme wet and dry events did not increase over the past half century, as demonstrated by nonsignificant changes in the probability of concurrently long CDD and long consecutive wet days (CWD). A trivariate copula analysis showed that some grid locations in the southeast of the plateau had an increasing risk of extreme precipitation events occurring at a high frequency and a high intensity, and forming a large percentage of the annual precipitation. Joint analysis of precipitation and temperature indices showed that the risk of higher temperatures and longer spells of consecutive dry days had increased over the past 50 years in grid locations scattered in the northern and southern regions: there were negative trends in the bivariate return periods for warm days (TX90p) and CDD. In addition, there was a decreased probability of concurrent long spells of consecutive wet days and colder temperatures, as demonstrated by the positive trends in the bivariate return periods for cold days (TX10p) and CWD across large areas of the plateau. Overall, the risk of severe floods and droughts over the Loess Plateau increased over the period 1961–2011.
Journal Article