Gully Land Consolidation Research Articles

Erosion Transportation Processes as Influenced by Gully Land Consolidation Projects in Highly Managed Small Watersheds in the Loess Hilly–Gully Region, China

The Loess Hilly–Gully region (LHGR) is the most serious soil erosion area in the world. For the small watershed with high management in this area, the scientific problem that has been paid attention to in recent years is the impact of the land consolidation project on the erosion environment in the gully region. In this study, the 3D simulation method of vegetation, eroded sediment and pollutant transport was innovated based on the principles of erosion sediment dynamics and similarity theory, and the impacts of GLCP were analyzed on the erosion environment at different scales. The verification results show that the design method and the scale conversion relationship (geometric scale: λl = 100) were reasonable and could simulate the transport process on the complex underlying surface of a small watershed. Compared with untreated watersheds, a significant change was the current flood peak lagging behind the sediment peak. There were two important critical values of GLCP impact on the erosion environment. The erosion transport in HMSW had no change when the proportion was less than 0.85%, and increased obviously when it was greater than 3.3%. The above results have important theoretical and practical significance for watershed simulation and land-use management in HMSW.

Chemical fertilizer reduction with organic fertilizer effectively improve soil fertility and microbial community from newly cultivated land in the Loess Plateau of China

Improving the soil quality of cultivated land generated by the Gully Land Consolidation Project could promote sustainable economic and ecological development in the hilly gully area of the Loess Plateau, China. A pot experiment with maize crop was conducted to assess the effects of different organic amendments and chemical fertilizer reduction on soil fertility and the microbial community in newly cultivated land, of which the amount of chemical fertilizer applied was half of the local conventional maize field (90 kg ha−1 of CO(NH2)2, 45 kg ha−1 of P2O5, and 60 kg ha−1 of K2O). The experiment involved six treatments: bare soil (CK), only maize (M), maize + chemical fertilizer (MF), maize + chemical fertilizer + organic fertilizer (MFO), maize + chemical fertilizer + biochar (MFB), and maize + chemical fertilizer + polyacrylamide (MFP). The results are as follows: (1) compared with the MF treatment, the MFO treatment exhibited the best effect on improving soil physicochemical properties, such as electrical conductivity (EC), soil organic carbon (SOC), nitrate nitrogen (NO3−-N), total nitrogen (TN), available phosphorus (AP) and available potassium (AK), followed by MFB and MFP. (2) The MFO treatment significantly (P < 0.05) improved the Species richness and Shannon indices of the bacteria, but its effects on fungal diversity index are not significant. (3) The MFO treatment increased the relative abundance of Betaproteobacteria, Alphaproteobacteria, Gammaproteobacteria and Gemmatimonadetes and decreased the relative abundance of Sordariomycetes and Agaricomycetes, and it also increased the functional abundance of Amino acid metabolism, Membrane transport, Xenobiotics biodegradation and metabolism, Undefined Saprotrophs and Arbuscular Mycorrhizal Fungi. (4) The TN and EC were the main driving factors of bacterial community structural variation, while TN and NO3−-N were the main factors for variation of fungal community structure. (5) The fresh weight and dry weight of maize increased significantly (P < 0.05) under all amendment treatments, among which the MFO treatment had the greatest effect. In conclusion, organic fertilizer application is the most effective measure for rapidly improving soil fertility and microbial community structure. Our findings have valuable implications for agricultural land productivity, food security and long-term sustainability of the environment.

Influence of Gully Land Consolidation on Phreatic Water Transformation in the Loess Hilly and Gully Region

Gully Land Consolidation (GLC) is a proven method to create farmlands and increase crop yields in the Loess Hilly and Gully Region, China. However, GLC influences phreatic water transformation and might cause the farmlands water disasters, such as salinization and swamping. For exploring the influence of GLC on phreatic water transformation and mitigating disasters, a series of indoor experiments were conducted in the artificial rainfall hall. Then, we simulated the phreatic water transformation patterns under more conditions with HYDRUS-3D. Finally, an engineering demonstration in the field was performed to validate our research. The indoor experiments indicated that GLC could increase phreatic water outflow rate 4.39 times and phreatic water coefficient (PWC) 2.86 times with a considerable delay. After calibration and validation with experimental data, the HYDRUS-3D was used to simulate phreatic water transformation under more soil thickness and rainfall intensities. Accordingly, we summarized the relationship among PWC, rainfall intensities, and soil thickness, and therefore suggested a blind ditch system to alleviate farmlands disasters. Field application showed that a blind ditch system could avoid disasters with 3.2 times the phreatic water transformation rate compared to loess. Our research provides implications for sustainable land uses and management in the region with thick soil covers.

Sliding mechanical properties of fault gouge studied from ring shear test-based microscopic morphology characterization

Fault activity is a factor causing geological disasters and controlling their spatial distribution. The information on fault activity can be recorded by the microstructure of the fault gouge sliding surface, which provides an approach to study the macroscopic mechanical behavior of faults. In this study, the ring shear test was used to simulate the shear sliding behavior of a fault gouge under different stress states and water contents, and the microstructure of the shear sliding surface was quantitatively analyzed using scanning electron microscopy (SEM). The results revealed an evident relationship between the microstructure and macroscopic mechanical properties of the fault gouge. The microstructure, represented by sliding scratches, was primarily created by the movement of coarse particles, such as sand and quartz. An index of the sliding scratch ratio was proposed to characterize the microstructure. The sliding scratch ratio is negatively correlated with water content and normal stress, and a multivariate model of sliding scratch ratio was established with water content, normal stress and coarse particle contents. Allying the model to natural scratches of the fault gouge reveals that the observed sliding scratches were formed during slope sliding, which proves the influence of fault on the occurrence of the studied landslide. Influenced by the “Gully Land Consolidation” projects in the Loess Plateau of China, the groundwater level may increase and then weaken the shear strength of fault gouge, reducing the stability of slopes crossed by fault zone. Therefore, more attention should be paid to potential geological disasters induced by faults in gully filled areas

Sustainability of soil organic carbon in consolidated gully land in China\u2019s Loess Plateau

Massive gully land consolidation projects, launched in China’s Loess Plateau, aim to restore 2667 mathrm{km}^2 agricultural lands in total by consolidating 2026 highly eroded gullies. This effort represents a social engineering project where the economic development and livelihood of the farming families are closely tied to the ability of these emergent landscapes to provide agricultural services. Whether these ‘time zero’ landscapes have the resilience to provide a sustainable soil condition such as soil organic carbon (SOC) content remains unknown. By studying two watersheds, one of which is a control site, we show that the consolidated gully serves as an enhanced carbon sink, where the magnitude of SOC increase rate (1.0 mathrm{g,C}/mathrm{m}^2/mathrm{year}) is about twice that of the SOC decrease rate (− 0.5 mathrm{g,C}/mathrm{m}^2/mathrm{year}) in the surrounding natural watershed. Over a 50-year co-evolution of landscape and SOC turnover, we find that the dominant mechanisms that determine the carbon cycling are different between the consolidated gully and natural watersheds. In natural watersheds, the flux of SOC transformation is mainly driven by the flux of SOC transport; but in the consolidated gully, the transport has little impact on the transformation. Furthermore, we find that extending the surface carbon residence time has the potential to efficiently enhance carbon sequestration from the atmosphere with a rate as high as 8 mathrm{g,C}/mathrm{m}^2/mathrm{year} compared to the current 0.4 mathrm{g,C}/mathrm{m}^2/mathrm{year}. The success for the completion of all gully consolidation would lead to as high as 26.67 mathrm{Gg,C}/mathrm{year} sequestrated into soils. This work, therefore, not only provides an assessment and guidance of the long-term sustainability of the ‘time zero’ landscapes but also a solution for sequestration hbox {CO}_2 into soils.

Farming Influence on Physical-Mechanical Properties and Microstructural Characteristics of Backfilled Loess Farmland in Yan’an, China

A gigantic project named Gully Land Consolidation (GLC) was launched in the hill-gully region of the Chinese Loess Plateau in 2011 to cope with land degradation and create new farmlands for cultivation. However, as a particular kind of remolded loess, the newly created and backfilled farmland may bring new engineering and environmental problems because the soil structure was disturbed and destroyed. In this study, current situations and characteristics of GLC are introduced. Test results show that physical-mechanical properties and microstructural characteristics of backfilled loess of one-year and five-year farmland are significantly affected by the Gully Land Consolidation project. Compared to natural loess, the moisture content, density, and internal friction angle of backfilled loess increase. On the contrary, the porosity, plasticity index, particle size index, and cohesion index decrease. Through SEM tests, it is observed that the particles of backfilled loess are rounded, with large pores filled with crushed fine particles, which results in skeleton strength weakness among particles and pores. The pore size distribution (PSD) of the four types of loess (Q3 loess, Q2 loess, one-year farmland, and five-year farmland) was measured using mercury intrusion porosimetry (MIP) tests, showing that the pore size of Q3 loess is mainly mesopores 4000–20,000 nm in size, accounting for 67.5%. The Q2, five-year, and one-year farmland loess have mainly small pores 100–4000 nm in size, accounting for 52.5%, 51.7%, and 71.7%, respectively. The microscopic analysis shows that backfill action degrades the macropores and mesopores into small pores and micropores, leading to weak connection strength among soil particles, which further affects the physical-mechanical properties of loess. The disturbance of backfilled loess leads to an obvious decrease in cohesion and a slight increase in internal friction compared to natural loess. The farming effect becomes prominent with increased backfill time, while the loess soil moisture content increases gradually. Both the cohesion and internal friction of the backfilled loess soil decrease to different degrees. This study is helpful to investigate sustainable land use in the Chinese Loess Plateau and similar areas.

Spatial analysis of land-use management for gully land consolidation on the Loess Plateau in China

Abstract How to balance the relationship between man and land has always been an essential problem for human beings. In 2011, the Gully Land Consolidation (GLC) project was implemented on the Loess Plateau in China. The aim of this project was to improve the living conditions of the local people through land-use management while ensuring the integrity of the environment. As little is known about the GLC, the objective of this study is to provide insight into the effects and potential problems associated with this project. We carried out a polygon-based interpretation of five land types before and after this project was implemented using multiple high-resolution satellite images (0.46 m) and 0.1 m resolution UAV photographs. The ecological footprint method was applied to analyze the supply-demand relationship between human and the land to assess the impact of engineering. Both the ecological capacity value and the area of arable land have increased due to land-use management, suggesting that this project had a positive effect in the area studied. The correlation between the spatial distribution and the transformation of arable land types was also examined to evaluate the efficiency of this project. Six factors were statistically analyzed to identify the most typical characteristics of the unused land distribution role. The existence of unused arable land is concentrated at the head of each gully. It is mainly affected by engineering, but it is also affected by the scale of the project. As a result, we identified two effects of the GLC. Although there were problems after this project, for instance, the unused rate of land became higher as the arable land increased, this project can satisfy human needs by increasing the area and quality of the arable land while improving the carrying capacity of the ecological environment.

Evaluation of the environmental effects of intensive land consolidation: A field-based case study of the Chinese Loess Plateau

The large-scale implementation of the Grain for Green project on the Chinese Loess Plateau since 1999 has greatly increased the vegetation coverage and rapidly decreased the agricultural land by converting slope cropland to planted vegetation (forest and grasslands). However, the geological, hydrological, ecological, and agricultural effects of the Gully Land Consolidation (GLC) project launched at Yan’an City in 2011 to address these land-use problems are not clearly understood. To assess the project outcomes in this region, we examined 71 of the 193 subprojects (61 treated gullies and 10 untreated gullies); measured geological, hydrological, ecological, and agricultural indices in the field; and tested disturbed (n = 447) and undisturbed (n = 142) soil samples (e.g., particle size distribution, saturated hydraulic conductivity, bulk density, and heavy metal contents). We found that: (1) slope stability improved for 67 % of the subprojects, (2) severe swamping was found only for 2 % of the subprojects, (3) the average increase in NDVI was 0.0231, 69 % of treated gullies NDVI was increased, and (4) crop yield was overall improved. There were no significant differences between the treated and untreated gullies in soil texture, saturated hydraulic conductivity, bulk density, or heavy metal contents (Cr, Zn, Cu, Ni, Pb), although particle size contents (range of 0.05 mm – 0.20 mm) differed significantly (p < 0.05). To promote successful gully land consolidation, the GLC project should (1) prioritize slope stability and long-term maintenance of water preservation facilities in gullies, (2) use bioengineering to accelerate the maturation of newly created land, or develop new cropping system after the GLC project; (3) on the basis of Grain for Green, integrate the GLC project, and modern agriculture to be complementary.

Soil Moisture Characteristics of a Typical Slope in the Watershed of the Loess Plateau for Gully Land Consolidation Project

To clarify the characteristics of soil moisture in the slope of watershed of the gully land consolidation watershed, and to further guide the implementation of the gully land consolidation project and vegetation restoration in this area, this study selected a typical slope of gully land consolidation watershed as the research object. The soil moisture of different slope positions was monitored and analyzed, and its temporal stability was analyzed. The results showed that: 1) The average soil moisture of different slope positions increased with the increase of soil depth, and the variability showed an increasing-decreasing-increasing trend, and the variability was the smallest at about 70 cm from the surface with weak variability, and the soil moisture variability in other layers is moderate. 2) On the slope, the distribution characteristics of soil moisture content were as follows: upslope &lt;middleslope &lt;downslope position. The differences of soil moisture between the upslope and downslope, midslope and downslope were significant. 3) The temporal stability analysis of the soil moisture showed that there is high stability between August and September of the soil moisture of the 0-50 cm and the correlation is extremely significant, while the soil moisture content of 50-100 cm range has a significant correlation between May and June. 4) The time stability of soil moisture in the middle slope position is the highest, followed by the upslope position, and the time stability in the downslope position is the lowest. 5) The best time stability point in the study area is the M3 point of the middle slope.

基于层次分析法的延安治沟造地土地整治项目综合效益研究

基于层次分析法的延安治沟造地土地整治项目综合效益研究

Impacts of land consolidation on rural human–environment system in typical watershed of the Loess Plateau and implications for rural development policy

Exploring the impact of land consolidation on the evolution of rural human-environment system (HES) is of positive significance for optimizing land consolidation model and innovating rural development policy. Taken a typical small watershed in Yan'an city as case study area, this paper explored the impact of gully land consolidation (GLC) on local HES from the perspectives of land use, landscape pattern, ecological security, social-economic response and comprehensive evaluation, based on high-resolution remote sensing image data, landscape pattern analysis and household surveys. The results showed that: (1) GLC could contribute to the improvement of land use structure. The terraces, sloping fields, shrub land and grassland at the bottom and both sides of the gully were mostly converted to high quality check dam land. Some of the shrub land were converted to more ecologically suitable native forest due to biological measures. (2) GLC could also help to optimize the landscape pattern. The average patch area and patch cohesion index of the check dam land increased, which indicated that the function of production improved. The landscape shape index and patch cohesion index of forestland and shrub land kept at a high level, and thus their ecological function was stable. At the watershed level, the fragmentation degree of landscape decreased, the landscape tended to be more diversified and balanced, and the anti-jamming capability of landscape and stability of ecosystem improved. (3) GLC have positive effects on the ecological security. Vegetation cover, ecological environment and capacity of flood control improved significantly, and soil erosion decreased by 55%. And (4) human activities responded to the changes of geographical environment. The scale of agricultural production, agricultural mechanization, diversity and non-agriculturalization of employment increased. However, the structure of agriculture is still unitary, the efficiency of agriculture is still low, and rural development is still relatively lagging. Field investigations showed that insufficient public participation, and lack of leadership and overall planning for sustainable utilization of resources and environment are the main reasons. A ladder model has been proposed for better understanding the impacts of land consolidation on territorial human-environment system in rural China. This paper suggests that land consolidation should be seen and evaluated in a broader rural development context, and more efforts should be made to innovate the rural governance mechanism of “common consultation and collective action”, thereby exerting the comprehensive effectiveness of land consolidation and promoting the transformation development and revitalization of territorial rural HES.

Intensive land restoration profoundly alters the spatial and seasonal patterns of deep soil water storage at watershed scales

Soil-water storage (SWS) highly correlates with changes to land use and land restoration, and is an important variable for managing water resources and environmental restoration in water-limited terrestrial ecosystems. The Gully Land Consolidation project (GLC) was implemented in 2011 on the Chinese Loess Plateau and it may influence the spatial distribution and temporal variability of SWS at the watershed scale. However, there have been limited studies assessing the magnitude and pattern of such changes. We measured SWS to a depth of 5 m nine times over four seasons across two watersheds－one treated by the GLC project (GT-T, n = 89) and the other untreated (GT-U, n = 72). We then used correlation analysis, principle component analysis, multiple linear regression analysis, generalized linear model, and regression kriging to evaluate the seasonal variability, as well as spatial patterns, of SWS. Mean SWS in the spring, summer, autumn, and winter ranged from 830 to 934 mm in the GT-T watershed and from 681 to 771 mm in the GT-U watershed. Land use was the most important factor for predicting SWS in the two watersheds. After land management as a result of the GLC project, SWS exhibited different spatial patterns in the GT-T watershed compared with the GT-U watershed. Dynamics of SWS between adjacent seasons in the GT-U watershed displayed more variability than that in the GT-T watershed. In both watersheds, soil water volume (SWV, i.e., SWS per unit area × watershed area) declined from spring to summer (-3.9% in the GT-T and -13.4% in the GT-U), and increased from summer to autumn (11.7% in the GT-T and 20.7% in the GT-U). After the whole year, SWV displayed different degrees of increase in the two watersheds (10.6% in the GT-T, 2.7% in the GT-U) due to the effect of land restoration. The ratios of SWV in the gully land filled in the GT-T watershed to the SWV of the whole GT-T watershed for the four seasons ranged from 21.4–23.3%, with a mean value of 22%. Our results provide new insights regarding how human engineering of landscapes (as exemplified by GLC project) affect the spatial distribution of SWS and the dynamics of SWV storing capacity at the watershed scale. Understanding the dynamics of SWS/SWV between seasons is essential to evaluate, model and manage the soil water resources in human-affected watersheds.

Theoretical and practical research into excavation slope protection for agricultural geographical engineering in the Loess Plateau: A case study of China's Yangjuangou catchment

The Loess Plateau is one of the most vulnerable areas in the world as it is extremely susceptible to soil erosion and ecological destruction. Recently, the local government carried out the “Gully Land Consolidation Project” (GLCP) in the Loess Plateau region to increase farmland area, improve rural production and living conditions. Among all the GLCP engineering constructions, slope protection engineering plays an important role in ensuring the safety of the main project, residential lives and properties, although more theoretical and technical research on comprehensive protection of engineering slopes is required. In this study, a field experiment using 12 standard runoff plots (length 4m×width 2m) was performed in Yangjuangou catchment of Yan'an City, to compare and analyze the comprehensive benefit to vegetative growth, soil erosion and engineering benefit from four vegetation styles and three levels of slope gradient (45°, 53°,63°). Results show that under different slope gradient and vegetation styles, significant differences existed in the comprehensive benefit to slopes, as well as the levels of vegetative growth, soil erosion and engineering benefit. The comprehensive benefit of the 53° slope was significantly better than that of 45° and 63° slopes. In addition, the comprehensive benefit of slopes with one or more vegetation styles was better than that of non-vegetation covered slopes. With the increase in slope gradient, the vegetative growth and slope erosion indices of vegetation average height, species richness, vegetation coverage slope, runoff production and sediment yield, showed a remarkable declining trend. Conversely, the engineering benefit index including newly-increased farmland area and excavating earthwork volume, showed an increasing trend. Recently, agricultural geographical engineering (AGE) has become an indispensable method for ecological construction and agricultural development, resulting in an increase in research in the field of geography. These findings not only have theoretical significance and enrich our understanding of the influence of gradient and vegetation styles on excavation slope protection, but also have practical significance and provide a baseline for engineering parameters and suggestions for slope protection engineering strategies.

Characterizing spatial-temporal patterns and abrupt changes in deep soil moisture across an intensively managed watershed

Soil moisture content (SMC) is highly variable in space and time due to the combined effects of natural processes and human influences. This study was conducted to explore the temporal-spatial patterns of deep SMC and detect possible abrupt changes in SMC in deep soil layers across an intensively managed watershed. We monitored SMC to a depth of 500 cm from 2016 to 2017 at the Gutun watershed (N = 89) on the Chinese Loess Plateau and determined related soil and vegetation properties. The mean SMC on the slopes at different depths were lower than in the gullies at the intensively managed areas affected by the “Grain for Green” project and the “Gully Land Consolidation” project. With increasing soil depth, slope SMCs gradually increased to 14%, while gully SMCs reached 40%. The spatial structures and patterns of mean SMCs within the 0–500 cm profile were similar but differed among different sub-layers. The detected fast changing layers (FCLs) of SMC (mean thickness = 76 cm) often occurred on the slopes of the watershed, while the relatively stable layers of SMC (mean thickness = 257 cm) were often located in the gullies. In deep soil layers (below 300 cm), we detected deep-FCLs at eight sites (mean thickness = 60 cm) which were all located on the slopes and under the same species (Robinia pseudoacacia L.). The mean SMCs within each of the eight deep-FCLs demonstrated a decreasing trend with time, which may be caused by the distribution of fresh roots. Human management had a profound impact on the spatial and temporal patterns of SMC in deep soil profiles at the watershed scale. This information should be considered by hydrologists and policy makers when developing eco-hydrology models and best management practices at multiple scales in a watershed.

Valley reshaping and damming induce water table rise and soil salinization on the Chinese Loess Plateau

A megaproject, “Gully Land Consolidation” (GLC), was launched on the Chinese Loess Plateau in 2011 to combat land degradation and create new farmlands. However, the newly-claimed farmlands have suffered soil salinization, and the mechanism of salinization has been inadequately addressed. In this study, a creek valley that completed the GLC project in 2014 was selected and a total of 17 new farmlands along the reshaped creek valley were investigated in 2016. Moreover, the hillslope farmlands without conducting the GLC project, the loess parent material that used to fill the stream channel, and the water samples from reservoirs, irrigation wells and spring outlets in the reshaped valley were sampled and chemically analyzed. We found that the new farmlands experienced a significant rise in the water table that played a key role on soil salinization. After GLC, >80% of the sampling sites (14 out of 17) showed a shallow depth (≤3 m) from the soil surface down to the groundwater influence zone. Moreover, the closer the downstream farmlands to the newly-built dams, the shallower the water table, indicating considerable impacts of constructing dams on the water table depth in the near-dam farmlands. At the study site, more than half of the shallow soil samples (20 cm depth) underwent light soil salinization, and the most significant soil salinity occurred in the upper stream farmlands. The interplay between a near-surface water table, a high evaporation rate, landform features, and the alkaline properties of the loessial soil has led to the significant soil salinization in the upper stream of the valley. To mitigate soil salinization and ensure the sustainability of the newly-created farmlands in GLC, drainage trenches in the downstream near-dam farmlands and the drainage canals on both sides of the reshaped valley are suggested, which improve the drainage efficiency and control the water table depth.

The Effect of the Gully Land Consolidation Project on Soil Erosion and Crop Production on a Typical Watershed in the Loess Plateau

The Gully Land Consolidation Project (GLCP) was launched to create more arable land by excavating soil from the slopes on both sides of gullies, combined with simultaneous comprehensive gully prevention and control measures. The purpose of the GLCP is to increase crop production and reduce soil erosion to achieve ecological and agricultural sustainability. In this study, we assess the effects of the GLCP on soil erosion and crop production by studying the BaoChengGou Watershed in the Loess Plateau, primarily by means of high spatial-resolution satellite images (taken by the GF-1 and ZY-3 satellites) combined with the InVEST model and field investigations. Sloping cropland, sparse forestland, and natural grassland are the main land use types in the study area. After implementing the GLCP, consolidated land in the cropland increased by 7.35%, an increase that has come largely at the expense of grassland and forestland. The GLCP has markedly reduced soil erosion in the BaoChengGou Watershed, especially in the sense that soil erosion intensity was also reduced significantly in the project region on the whole, despite intensifying in certain places, such as excavated slopes; furthermore, it has improved crop yields in the study area by 10.9%. Comprehensive measurement shows the GLCP to be scientific, reasonable, and clearly efficacious. This study presents findings regarding the positive significance of the GLCP in promoting ecological and agricultural sustainability in the Loess Plateau.

Exploring the role of land restoration in the spatial patterns of deep soil water at watershed scales

Soil water is a key variable for re-vegetation and environmental restoration in water-limited terrestrial ecosystems such as the Chinese Loess Plateau. Large land restoration projects (e.g., the “Grain for Green” launched in 1999 and the “Gully Land Consolidation” launched in 2011) had substantial impacts on the storage, distribution, and spatial patterns of soil water, and these factors remain poorly understood across watershed scales. We measured the amount of water stored in soil layers from the surface down to 5 m depth and characterized the vertical distribution of gravimetric soil water content (SWC) among four land uses (cropland, shrubland, forestland, and orchard), two slope aspects (shady vs. sunny), and two landforms (slope vs. gully) in three watersheds on the Chinese Loess Plateau. All three of the watersheds were affected by Grain for Green project, two were affected by the Gully Land Consolidation project (named NG and GT-T watersheds) and one was unaffected by restoration efforts (named GT-U watershed). In the three watersheds, the slope and gully SWCs varied from 2.4 to 24.2% and from 4.8 to 46.6%, respectively, during the sampling period in October 2015 (end of the rainy season). The amount and vertical distribution of slope SWC differed significantly among the land uses and between shady and sunny slopes in the three watersheds (p < 0.05). The mean gully SWC (20.4%) was significantly higher than the mean slope SWC (8.7%) for each of the three watersheds (p < 0.01). Gullies filled by the Gully Land Consolidation project had a large capacity to store soil water by increasing the infiltration of precipitation, which accounted for 14.7% and 11.3% of the total annual rainfall in the NG and GT-T watersheds, respectively. Filled gullies can serve as large reservoirs of soil water to relieve the problem of water shortage and can also increase the amount of land available for cultivation to ease deficits in food production. A combination of the Grain for Green project on slopes for soil conservation and the Gully Land Consolidation project in gullies for storing more soil water and increasing farmland area is an effective land restoration strategy on the Chinese Loess Plateau and is helpful for managing water cycles in regions around the world with deep soils.

Land quality evaluation based on sustainable development for gully erosion control and land consolidation project of Yan’ an, China

Based on the three land consolidation projects in Yan’an region, the differentiation of the soil capacity, texture, available nutrients, pH etc before and after land consolidation were analyzed, and a comprehensive evaluation of soil quality before and after consolidation was done in this study. The results show that: (1) After the gully-land consolidation, the soil capacity, nitrogen, available P, available K and conductivity are increased, while the organic matter and pH are decreased. With one-year’s cultivation, the soil capacity decreased and the organic matter increased. After the slope-land consolidation, the soil physical and chemical properties have similar trends with the gullies, but the change is more significant. (2)No matter for gully or slope, the soil quality declines where the land just get consolidated, and the slope has more significant declining. With one-year’s cultivation, the soil quality of the gully has more rapid recovery with one grade uplift. (3) The correlation coefficient method was used to give a comprehensive evaluation of the soil quality, to considerate of the changes of the coefficients of the factors and the evaluation object. The evaluation can well reflect the actual situation of the soil quality, give reference to the soil quality evaluation for consolidated land, and the results may provide basis for the performance evaluation of the Yan’an land consolidation projects.

GIS-based effect assessment of soil erosion before and after gully land consolidation: A case study of Wangjiagou project region, Loess Plateau

The Loess Plateau is one typical area of serious soil erosion in the world. China has implemented ‘Grain for Green’ (GFG) project to restore the eco-environment of the Loess Plateau since 1999. With the GFG project subsidy approaching the end, it is concerned that farmers of fewer subsidies may reclaim land again. Thus, ‘Gully Land Consolidation Project’ (GLCP) was initiated in 2010. The core of the GLCP was to create more land suitable for farming in gullies so as to reduce land reclamation on the slopes which are ecological vulnerable areas. This paper aims to assess the effect of the GLCP on soil erosion problems by studying Wangjiagou project region located in the central part of Anzi valley in the middle of the Loess Plateau, mainly using the revised universal soil loss equation (RUSLE) based on GIS. The findings show that the GLCP can help to reduce soil shipment by 9.87% and it creates more terraces and river-nearby land suitable for farming which account for 27.41% of the whole study area. Thus, it is feasible to implement the GLCP in places below gradient 15°, though the GLCP also intensifies soil erosion in certain places such as field ridge, village land, floodplain, natural grassland, and shrub land. In short, the GLCP develops new generation dam land and balances the short-term and long-term interests to ease the conflicts between economic development and environmental protection. Furthermore, the GLCP and the GFG could also be combined preferably. On the one hand, the GFG improves the ecological environment, which could offer certain safety to the GLCP, on the other hand, the GLCP creates more farmland favorable for farming in gullies instead of land reclamation on the slopes, which could indirectly protect the GFG project.