Gully Land Consolidation Project Research Articles

TIC-driven sustainable land use mode in the Loess Plateau: A case study of gully land consolidation project in Yan'an City, China

The Loess Plateau is one of the most severely eroded areas in the world. The complexity of the multiple challenges facing the Loess Plateau entails the support of scientific and systematic innovations in land use. Based on technological innovation cluster (TIC) theory, this paper develops a self-circulation structure model for the TIC to analyze the hierarchical structure of the land-use innovations in the Loess Plateau. Then, employing the self-circulation structure model and taking the “Gully Land Consolidation Project” (GLCP) as a case study, this paper proposes one TIC-driven sustainable land use mode (TSLUM). A TIC has been developed among innovations in the TSLUM. The structure of TSLUM consists of three types of innovations: basic, related, and infrastructure innovations. Basic innovations are generally radical innovations that breed related, and infrastructure innovations. Diffusion-based and reversal-based mechanisms govern the evolution of the TSLUM. These two clustering mechanisms integrate with each other and jointly promote the development of the TSLUM in a self-circulation way. Furthermore, the TSLUM exhibits multiple functions, such as optimizing gully-slope interaction mechanism, providing continuous driving forces, consolidating the achievements of the “Grain for Green Project”, bolstering rural livelihoods, and fostering some feasible ways for food security. The results obtained will be useful for advancing sustainable land use and regional sustainable development in the Loess Plateau via TICs effectively and systematically.

Effects of the Gully Land Consolidation Project on Geohazards on a Typical Watershed on the Loess Plateau of China

From 2011 to 2013, a mega project, known as the Gully Land Consolidation Project (GLCP), was implemented in the hilly gully region atop China’s Loess Plateau. However, the GLCP involved large-scale slope excavation and gully backfilling that changed the local geological environment, which led to serious geohazards, such as erosion, soil salinization, and dam failure. In this study, various geohazards caused by the GLCP in the Gutun watershed (GTW) were investigated by combined remote sensing analysis, geophysical exploration, and field surveys, and the relationships between the hazards were also explored. According to the achieved results, increased soil erosion with an average doubling from 2018 to 2020 is widely distributed in the GTW. Furthermore, 195 areas containing clear evidence of salt precipitates were observed in some of the newly created arable lands, especially downstream of the dam. This was mainly attributed to the high water table, evaporation, and soluble salt concentration of the loess. Fifty-nine newly built silt dams, primarily located in the branch channels and at the gully mouth of the Gutun channel, broke in 2020. The osmotic damage and softening caused by the combined effect of the incomplete compaction of the dam body and concentrated heavy rainfall were the main reasons of the dam breaks. The different types of disasters in the GTW after the implementation of the GLCP show a strong spatial relationship that follows the surface water flow path and forms a disaster chain consisting of slope erosion, silt dam breaks, and the soil salinization of near-dam farmlands downstream. This disaster chain amplifies disaster risks and losses. These findings can guide the improvement of the GLCP and inform geohazard mitigation strategies in areas impacted by the GLCP.

Effects of the Gully Land Consolidation Project on soil erosion and sediment yield on the Loess Plateau, China

AbstractLand consolidation can increase the area of arable land and improve the ecology and environment and is widely used worldwide. The Gully Land Consolidation (GLC), as a special type of land consolidation, significantly impacts soil erosion. The purpose of this study was to investigate the effect of the GLC on soil erosion and sediment yield under different rainfall events and hydrological years in the Xingshuyaozi watershed on the Chinese Loess Plateau, where the GLC area accounted for 10.36% of the watershed. A computer model integrated with the Chinese soil loss equation (CSLE) and the continuity equation of sediment was used. Sediment connectivity before and after the GLC was compared to illustrate the effect of the GLC on sediment yield. The results showed that the reduction in soil loss increased with increasing rainfall amount, and the reduction rate of soil erosion was over 50%. The GLC had the greatest effect on soil erosion in wet years. The GLC effectively decreased sediment at the outlet of the watershed, with over 99% of the sediment being trapped. The reduction efficiency of soil erosion and sediment yield decreased in order of wet year, normal year and dry year. The decreased soil erosion and sediment yield resulted from the significantly lowered slope gradients and sediment connectivity after the GLC. These results indicate that the GLC is an effective soil and water conservation measure. These results can provide technical support for the application of the GLC and policymaking.

Effects of the Gully Land Consolidation Project on Runoff and Peak Flow Rate on the Loess Plateau, China

The Gully Land Consolidation (GLC) project, aiming to create land for agriculture on the Loess Plateau, heavily interfered with the underlying surface and thus affected the hydrological process. The purpose of this study was to investigate the effects of the GLC on the surface runoff and peak flow rates of watershed on the Loess Plateau under different rainfall events and hydrological years. A GIS-based Soil Conservation Service Curve Number (SCS-CN) model was used. The results showed that GLC reduced the mean event surface runoff by 6.2–24.7%, and the reducing efficiency was the highest under light rain events. GLC also decreased annual surface runoff, and the reducing efficiency was 12.04% (normal year) > 7.63% (wet year) > 4.45% (dry year). In addition, GLC decreased the peak flow rate of the watershed by 8.1–30.2% and prolonged the time to peak flow rate. The efficiency of GLC in reducing the peak flow rate was higher under light rain events than that under extraordinary storm events. The reason for the decrease in runoff and peak flow rate after GLC was that the GLC decreased the slope gradient and hydrological connectivity of the watershed. The results will provide guidance for the application of GLC on the Loess Plateau and watershed management for similar regions.

Evaluation of the impact of the Gully Land Consolidation Project on runoff under extreme rainfall

AbstractExtreme rainfall is an important driver of soil erosion and land damage. The Gully Land Consolidation program (GLCP) was first launched in 2011 as a major land reclamation practice to increase farmland in the Loess Plateau of China. Studying the impact of artificial projects on hydrology can help humans to respond to the various water issues, but the assessment of the effects of the GLCP on extreme rainfall‐induced water runoff at watershed scale is currently lacking. Our study used the soil and water assessment tool (SWAT) to evaluate the influence of the GLCP at different locations and areas on water runoff under extreme rainfall events in the Yanhe watershed. Results showed that: (1) the GLCP can improve the interception of surface runoff, with interception efficiency in downstream of the watershed approximately twice that at midstream and entire watershed as well as seven‐times that at the upstream; (2) when GLCP measures are evenly distributed in a watershed, as the area of GLCP increases from 76.40 km2 (1% of watershed area) to 382.01 km2 (5%), the interception of surface runoff increases by 0.77 mm; (3) and the GLCP can increase soil infiltration and groundwater recharge. This research is expected to provide insights into the optimized layout of the GLCP at watershed scale. Correspondingly, policymakers can refer to this information in developing policies on the sustainable use of land.

Spatiotemporal soil water storage variation comparison between newly formed and untreated gully land sites under a land restoration project and associated implications on land management

Soil water storage (SWS) can effectively be used as an important indicator to manage soil water resources in water-limited ecosystems, being strongly linked to land-use and land management changes. The Government of China launched the Gully Land Consolidation (GLC) project in 2011 to reclaim landforms and resolve land scarcity and food shortages in the Chinese Loess Plateau (CLP) without endangering the environment. Corollary effects of this project were alterations to original landscapes and associated hydrological processes. However, temporal dynamics in available soil water of the newly formed land for cultivation purposes remain unclear. Accordingly, this study measured SWS to a 5 m soil depth over a 5-year period at two gully sites, one newly formed under the GLC project (i.e., the experimental site) and the other left untreated (i.e., the control). SWS exhibited similarly weak temporal variation at both gully sites (coefficient of variation [CV] = 6% at the experimental site; CV = 11% at the control site). Although SWS always negatively correlated to mean temperature and wind speed (p < 0.05) with no observable hysteresis, SWS responded to precipitation at both sites with obvious hysteresis (experimental site = two month hysteresis; control site = three months hysteresis). Seasonal SWS characteristics confirmed the lag response to precipitation. Moreover, spatial SWS patterns differed distinctly at both sites. The mean proportion of available SWS to the available water holding capacity was 69% at the experimental site, indicating that stored soil water was available for crop cultivation without the threat of water shortages. Our results provide new insight into spatial and temporal SWS variation in newly formed land engineered by restoration projects. Furthermore, clarifying SWS temporal dynamics and spatial distributions based on long-term monitoring is essential to evaluate, model, and manage water resources in areas affected by anthropic activities.

Characteristics and prevention mechanisms of artificial slope instability in the Chinese Loess Plateau

Numerous artificial slopes emerged in the watersheds of the Chinese Loess Plateau (LP) after the Gully Land Consolidation project (GLCP) that cut slopes to create farmland in the gully, which had incurred instabilities over time and could potentially resulted in soil erosion and geological hazard. This paper explored the characteristics and prevention mechanisms of artificial slope instability after the GLCP with field investigation in a typical watershed and the Back Propagation Neural Network (BPNN) method. The results showed that: (1) 439 instabilities induced by infiltration and erosion were found in 79 artificial slopes. (2) The difference of soil moisture and failure mode resulted in the instability degree of shady slope and lower slope were significantly higher than that of sunny slope and upper slope. (3) Among the surface condition factors, slope instability volume was significantly influenced by gradient, soil compactness, height and soil shear strength. Platform instability volume had great connection with soil compactness and its shear strength. (4) A “Drain-Improve-Green-Reinforce (DIGR)” system was proposed as the prevention mechanism for artificial slope instability, which included drainage system, soil improvement, vegetation protection, and reinforcement engineering. Taken together, this research provides the scientific reference for a better understanding and prevention of artificial slope instability, which would contribute to ensuring GLCP effectiveness and ecological security in the LP.

Measuring the Ecological Safety Effects of Land Use Transitions Promoted by Land Consolidation Projects: The Case of Yan’an City on the Loess Plateau of China

Land consolidation projects play an important role in promoting agricultural land use transitions, ensuring national food security, and accelerating the construction of ecological civilization. The Loess Plateau in China is a typical ecologically fragile area, where the Gully Land Consolidation Project (GLCP) has been implemented recently and had a major impact on local ecological safety. In this study, we established a quantitative evaluation model for ecological safety effects from the four aspects of dam safety, slope stability, efficient farmland, and effective management, and then scientifically measured the ecological safety effects of land use transitions promoted by land consolidation projects. Three small watersheds (Gutun, Yangjuangou and Luoping) within the GLCP area were employed to verify the evaluation model for ecological safety effects. The results showed that the GLCP can effectively improve the ecological environment and promote the development of modern agriculture, but the ecological safety of gullies and slopes in some areas may also facing a series of threats due to improper project management measures. Among them, Gutun had the highest ecological safety evaluation value, followed by Yangjuangou, while Luoping had the lowest value. The indicator system and evaluation method established in this research could be helpful to systematically diagnose the problems and scientifically guide the implementation of the GLCP from the perspective of ecological safety.

Effects of land-use management on soil erosion: A case study in a typical watershed of the hilly and gully region on the Loess Plateau of China

The effect of land use on erosion over space and time is relevant. In this study, two types of land-use management practices, the gully land consolidation (GLC) project and the land consolidation (LC) project, were applied on the Loess Plateau. Based on the soil erosion that occurred from 2010 to 2019, the spatial distribution, spatiotemporal evolution and susceptibility map of soil erosion were analyzed by geospatial analysis, statistical methods and frequency ratio (FR) models. The results showed that the implementation of the GLC project can have two effects on soil erosion. Firstly, a large amount of slope erosion was caused by slope excavation in the GLC watershed; secondly, the amount and scale of gully erosion were effectively controlled by hydraulic engineering. In addition, the unreasonable hydraulic engineering of the LC project can cause large areas of soil erosion. The influencing factors of gully erosion can be ranked as follows: reservoir > elevation > dam land > flow length > geology > LS. Three aspects of engineering optimization measures for the GLC project were proposed: 1. Slope excavation should be reduced, and diverse slope protections should be implemented in this project, especially for the bottom of the slope, which should adopt different measures than the top of the slope. 2. For trenches within 1.2 km of the gully head, more attention should focus on soil and water conservation measures than on land leveling. 3. Hydraulic engineering and irrigation and drainage engineering should effectively cooperate with leveling projects and adjust the applied measures to the local conditions and the natural shape of the original rivers. As a new land-use management approach, our results highlight that little is known about the effect of the GLC project on soil erosion, and our results can provide specific guidance for the next step of project implementation.

Evaluating the flow and sediment effects of gully land consolidation on the Loess Plateau, China

Gully land consolidation (GLC) is a slope-gully reclamation program that was implemented after “Grain for Green” project on the Loess Plateau, China. Through the GLC project, the Chinese government planned to increase the area of cropland by 337.80 km2 from 2013 to 2017. To quantify the impact of GLC on runoff and sediment transport, the coupled SWAT (Soil and Water Assessment Tool) model, which was integrated with a process-based terrace algorithm, was employed in this research. The results showed that the improved SWAT model was proven to be a powerful tool for detecting the effect of GLC on flow and sediment discharge. The effect of GLC on flow and sediment loading was concentrated in the flooding period, its runoff interception efficiency was 169,350 m3/(km2·yr), and sediment trap efficiency was 3979 t/(km2·yr), showing that it had good flow and sediment reduction benefits. However, the GLC project drastically altered the water and sediment flux equilibrium, and excessive expansion was likely to lose parts of riparian-ecosystem functions of the downstream river. In view of this, we integrated the improved SWAT (embedded in the terrace module), double-mass curve and Pettitt test to identify the recommended ratio of GLC area to the total area in the Yanhe watershed. The results demonstrated that if the reclaimed gully area accounted for 0.8% (61 km2) of the total area (7608 km2), the runoff abruptly changed. Therefore, the reclaimed gully area should remain within 0.8% of the total area in the Yanhe watershed, if so, GLC not only alleviates the contradiction between agricultural development and ecological restoration, but also gives full play to its functions of reducing flood and restricting sediment transport.

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.

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.

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

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.

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.

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.