China Loess Research Articles

Strongly Active Responses of Pinus Tabuliformis and Sophora Viciifolia to Co2 Enrichment and Drought Revealed by Tree Ring Isotopes on the Central China's Loess Plateau

Strongly Active Responses of Pinus Tabuliformis and Sophora Viciifolia to Co2 Enrichment and Drought Revealed by Tree Ring Isotopes on the Central China's Loess Plateau

Factors dominating the horizontal and vertical variability of soil water vary with climate and plant type in loess deposits

Identifying the variability and predominant factors affecting soil water (SW) is essential in regions with thick vadose zones and deep-rooted plants. This information is needed to clarify the balance between water availability and plant water demand. We collected 9263 soil samples from 128 profiles of 7–25 m deep soil under different climates (arid, semiarid and subhumid), soil textures and plant types (shallow or deep roots) in China's Loess Plateau. The factors dominating the horizontal and vertical variability of SW were identified using a multimodel inference approach and stepwise regression analysis. Horizontally, the mean water content and storage increased while the water deficits decreased from the northwest to the southeast. Vertically, mean water content and storage are highest in the relatively stable layer, followed by rapidly changing layers and active layers. Plant age and soil clay content dominate the horizontally varied SW, while plant age and normalized difference vegetation index (NDVI) dominate the vertical variability of SW. However, the dominant factors appeared to differ with climate and plant type. It was determined that for climate, soil clay content and plant age in arid regions, precipitation and plant age in semiarid regions, NDVI and plant age in subhumid regions were important factors. For plants, the dominant factors are NDVI and precipitation under shallow-rooted plants; however, NDVI and plant age were dominant under deep-rooted plants. The dominance of plant age highlighted the impact of vegetation patterns on SW, especially for deep-rooted plants, which should be taken into account when managing water resources and ecosystem rehabilitation in degraded regions.

Simulations and Experiments of the Soil Temperature Distribution after 2.45-GHz Short-Time Term Microwave Treatment

Microwave treatment is a green and pollution-free soil disinfection method. The application of microwaves to disinfect soil before cultivation is highly important to increase crop yields and protect the ecological environment. The electromagnetic field is an important parameter influencing the soil temperature field in the process of microwave soil treatment, and the change in soil temperature directly affects soil disinfection. Therefore, this article carried out research on the heating pattern in North China loess due to microwave treatment. First, COMSOL software was employed to simulate the microwave soil treatment process to analyze microwave penetration into soil. Second, with the application of microwaves at the designed frequency produced with a 2.45-GHz tunable microwave generating microdevice, soil with water contents of 0%, 10%, 20%, and 30% was treated for 10~60 s (at 10-s time intervals), and experiments on the influence of the microwave output power, treatment time, and soil moisture content on the soil temperature were performed via the controlled variable method. The simulation results indicate that with increasing soil moisture content, the microwave frequency inside the soil model increases, and the electric field intensity value decreases in the model at the same depth. After microwaves traverse through the 20-cm soil model, the incident field strength is three orders of magnitude lower than the outgoing field strength. The results of the microwave soil treatment experiment reveal that: (1) Compared to microwave output power levels of 1.8 and 1.6 kW, a level of 2 kW is more suitable for microwave soil disinfection. (2) After treatment, the highest temperature occurs on the soil surface, not within the soil. (3) The location of the highest soil internal temperature after microwave treatment increasingly approaches the soil surface with increasing soil moisture content, and the microwave output power does not affect the location of the highest soil internal temperature. Combining the electromagnetic field simulation and microwave soil treatment experiment results, it was found that the higher the field strength is, the higher the temperature value, and the highest soil internal temperature after microwave treatment often occurs at the first electromagnetic wave peak.

Effects of different tillage practices on rill distribution of sloping farmland

AbstractTo better understand how surface roughness affects soil erosion, we investigated the rill distribution of sloping farmland under tillage practices in China's Loess Plateau region. Four tillage treatments (three tillage practices and a non‐tillage control) were simulated manually using five slope gradient levels (3°–20°) and two rainfall intensities (90 and 120 mm h–1). The spatial distribution of rills was extracted and four indices were derived based on Strahler's stream ordering. With increasing slope gradient, random roughness exhibited a decreasing effect on sediment yield, and the interaction effect changed from negative to positive at a critical slope gradient of ∼10°. Low‐order rills gradually merged into high‐order rills, forming a complete rill network toward higher slope gradients. The bifurcation ratio of different treatments did not differ considerably. With increasing surface roughness, the length of first‐order rills and their longitudinal river slope decreased. For example, on the 10° slope under 90 mm h–1 rainfall intensity, the longitudinal river slope of contour plowing, manual hoeing, and contour drilling treatments decreased respectively by 29.4, 38, and 48.9% relative to the value of smooth surface (control) with a rise in rill order. Yet a greater surface roughness had the least effect on the number, length, and longitudinal river slope of third‐order rills. A similar result was obtained in that correlation between sediment yield and the length of third‐order rills was the weakest overall. The results indicate that surface roughness affects rill distribution and soil erosion on sloping farmland via its effect upon low‐orderrill development.

Dynamics of interspecific water relationship in vertical and horizontal dimensions under a dryland apple-Brassica intercropping system: Quantifying by experiments and the 3D Hi-sAFe model

Separation of water absorption by roots between trees and crops is critical to intercropping in water-limited regions. The current knowledge about interspecific water relationship is in one dimension, i.e., the vertical direction, little is known in both vertical and horizontal directions under different rainfall conditions. Therefore, an experiment was carried out in an apple tree based intercropping system and an apple tree monoculture on China's Loess Plateau during one growing season which started with a high rainfall period followed by a low rainfall period. We investigated the spatial distribution of soil water and plant root, and simulated their water use strategies using the 3D Hi-sAFe model. The root growth of apple trees in the top 60 cm was restricted by intercropping in the cropped area but increased in the top 40 cm in the uncropped area compared with monoculture. In the high rainfall period, compared with the control, the apple trees' water absorption from the uncropped area (0–60 cm) increased by 44.43%, but the water utilization from the cropped area (0–60 cm) decreased by 32.59%. More than 90% of the soil water absorbed by B. napus came from the 0–60 cm soil layer in the cropped area. During the low rainfall period, intercropping promoted an increase of 14.79% in apple trees' water absorption from the 60–100 cm soil layer in the cropped area. The soil water in the 20–60 cm layer became the main source for B. napus and its contribution was 63.51%, but only 20.56% of the water absorbed by apple trees came from here. It can be concluded that, to alleviate water competition, water absorption between species was segregated horizontally during the wet period due to the roots "niche differentiation", while water use complementarity occurred along the vertical axis during the dry period.

Eco-efficiency in China's Loess Plateau Region and its influencing factors: a data envelopment analysis from both static and dynamic perspectives.

China's Loess Plateau Region (LPR) plays a significant role in national ecological security and development. Due to the advantage that relates environment with economy, eco-efficiency has become an important indicator of sustainable analysis. Using cross-level panel data for the period 2006-2017, this paper studied LPR's static eco-efficiency and dynamic performance through a combined application of DEA super-efficient slack-based measure and Malmquist Productivity Index at multi-scales. LPR's eco-efficiency was found to experience a slight increase during the study period. The value decreased roughly from east to west, with high eco-efficiency mainly distributed in provincial cities and resource-based cities. The decomposition of the Malmquist Index indicated that technological change contributed most to the improvement of eco-efficiency in the LPR. Besides, this paper explained the variations of eco-efficiency based on the integrated input-output indicators and TOBIT regression model. Economic scale, population density, government regulation, technical innovation, and openness degree were identified as positive influencing factors, while the structure of the industry and land-use intensity were found to have negative impacts on eco-efficiency. Resource-based cities were found to have stronger potentials for eco-efficiency improvement than non-resource-based cities. This paper revealed the characteristics of LPR's eco-efficiency from three perspectives: a spatiotemporal perspective, a macro-meso-micro perspective, and a static-dynamic perspective. The findings of this study hold important implications for policy makers.

Distribution characteristics and controls of soil organic carbon at different spatial scales in China′s Loess Plateau

Understanding the variations and controls of soil organic carbon (SOC) at different spatial scales can help in selecting edaphic and environmental covariates that enables us to model SOC more accurately. The present study investigated the distribution characteristics and controls of SOC content at various spatial scales, including a deep soil core (204.5 m) taken from land surface down to bedrock (plot scale), two toposequences with different slope aspects (slope scale), and eighty-six soil profiles along a north-south transect under different land uses (regional scale) in China's Loess Plateau. The results showed that SOC content at different spatial scales decreased exponentially with increasing soil depth, but the rate of reduction differed at various spatial scales and in soil layers at different depths. For the deep soil core, the SOC content and the average rate of reduction with depth in the 0–15.5 m soil layer were significantly higher than the corresponding values of the 15.5–34.5 m and 34.5–204.5 m soil layers (p < 0.05). For the toposequences with varying slope aspects, SOC content in the 0–50 cm soil layer declined rapidly with increasing depth; while SOC content in the 50–200 cm soil layer showed relatively no change. There was no significant difference of average SOC content at depths of 0–200 cm for forestland and grassland considering slope aspects that differed or were the same (p > 0.05) due to the similar climatic conditions. However, SOC content within 0–500 cm soil profile under different land uses along the north-south transect exhibited a significant difference (p < 0.05), following the order of farmland (4.94 ± 1.23 g kg−1) > forestland (3.01 ± 1.45 g kg−1) > grassland (2.03 ± 0.68 g kg−1); moreover, the mean SOC content of the 0–500 cm soil profile generally decreased from south to north following the decreasing rainfall and temperature gradient. The average rates of reduction of SOC content in the 0–50 cm soil layer under different land uses (0.0807–0.1756 g kg−1 cm−1) were higher than the values of the 50–200 cm (0.0021–0.0154 g kg−1 cm−1) and 200–500 cm soil layers (0.0001–0.0017 g kg−1 cm−). The SOC content at the plot scale at different depths positively correlated with total nitrogen content. The SOC content at the slope scale was mainly affected by soil water content and saturated hydraulic conductivity, while that at the regional scale was impacted by climate, topography and soil water/clay content. Pedotransfer functions were applied to adequately simulate and predict SOC content at different spatial scales in the studied area, which could provide a foundation to build SOC prediction models and extrapolate the various spatial scales to other loess regions worldwide. Our findings demonstrate the importance of considering the scale effects for efficiently predicting the spatial patterns of SOC and can help in devising better policy to protect or enhance existing SOC stocks.

Transform the Land, Train the Youth: Water and Soil Conservation Teams and State-Induced Migration in mid-1960s China

AbstractBeginning in 1964, the PRC party-state orchestrated the resettlement of thousands of young people from cities to erosion-prone areas in China's Loess Plateau to form “water and soil conservation teams” (shuitu baochi zhuanyedui). Although their ostensible mission was to limit erosion by building terraces and planting trees, documents related to conservation teams emphasized their capacity to thoroughly reform urban youth while mobilizing them to do the work of remaking the environment. Provincial and county archives, along with fieldwork conducted at the site of one water and soil conservation team in Shaanxi province's Baishui county, indicate that conservation teams did not realize either of these objectives. Due to urban youth's inexperience with agriculture and conservation, they did little to promote environmental management. At the same time, unruly teenagers who migrated to the countryside to join conservation teams, as well as the cadres who oversaw them, continued to engage in transgressive behavior.

Stable isotopes of deep soil water retain long-term evaporation loss on China's Loess Plateau

Evaporation from the land surface enriches heavy isotope ratios (2H/1H and 18O/16 O) in shallow soils, and downward water movement will carry the fractionation signal to deep soils. However, how to acquire the evaporation from water stable isotopes in deep soils remains untested. Here, we measured water stable isotope composition in the deep soils (2–10 m) across 20 sites on China's Loess Plateau. Our results show that the line-conditioned excess (lc-excess) in deep soils of these sites was invariable with depth at each site, but ranged between −14.0‰ and − 4.1‰ among these sites, indicating differing degree of enrichment in heavy water isotopes between sites. Moreover, the mean lc-excess in deep soils water was significantly correlated to mean annual precipitation (R2 = 0.57), potential evapotranspiration (R2 = 0.25), and the Budyko dryness (R2 = 0.68), indicating that deep soil water lc-excess reflects land surface climate conditions. Furthermore, the deep soils correspond to a timescale of approximately 100 years at one site and more than 27 years at the remaining sites. These results together indicate that stable isotopes of deep soil water retained long-term land surface evaporation effects. Further, by implementing the steady-state isotope mass balance model into the lc-excess framework, we derived a new method to estimate evaporation loss fraction (f). Our f estimates at these sites varied between 5% and 15%, which may represent the lower bound of the actual evaporation to precipitation ratio. Nevertheless, our work suggests that in these and the other similar regions, deep soil is a novel archive for long-term soil evaporation loss, and f may be estimated through a snapshot field campaign of stable isotope measurements.

Evaluating the effect of ecological policies from the pattern change of persistent green patches–A case study of Yan'an in China's Loess Plateau

Evaluation from landscape pattern change can comprehensively reflect the impact of ecological policies on the ecosystem service function. However, previous assessments based on landscape patterns only considered land cover type and ignored the quality of vegetation cover, which could hardly reflect regional differences in restoration durability and sustainability. Based on the temporal phase characteristics of the vegetation index, this study proposes the concept of Persistent Green Patches (PGPs). Taking Yan'an, a key area for the implementation of ecological projects in the Loess Plateau, as a study area, the effect of ecological policies was evaluated from the pattern change of PGPs from 2000 to 2017 through Morphological Spatial Pattern Analysis (MSPA). It is found that (1) the area of PGPs was increased from 14.45% to 44.26% in Yan'an since the implementation of the ecological projects; (2) the Grain for Green projects can hardly form a short-term increase of PGPs; while the Natural Forest Protection projects can quickly increase the PGPs area, its effect would tend to be saturated or even decrease in the long term; (3) the fragmentation and connectivity of the landscape show that the ecological projects promote the connection between different green patches, and improves the overall connectivity of the PGPs. This study provides a new perspective on evaluating the effect of ecological projects, which is expected to provide a reference for the future optimization of relevant ecological policies and regional sustainable development.

Assessing the effects of ecological engineering on spatiotemporal dynamics of carbon storage from 2000 to 2016 in the Loess Plateau area using the InVEST model: A case study in Huining County, China

Implementation of the Grain for Green program (GGP) resulted in great changes in land use and cover in northwest China, and presumably in the region's carbon. However, accurate assessment of the effects of the GGP on carbon storage remains a challenge. The Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model can map and evaluate natural goods and services that sustain life and quantify their impact from the changes in the ecosystem. Taking Huining County in China's Loess Plateau region as a case, the land use and land cover changes (LUCC) following the GGP were quantified, and their effects on carbon storage between 2000 and 2016 were evaluated using the InVEST model. The results showed that, a total area of about 3996.13 km2 underwent changes following the GGP in Huining County during the study period, accounting roughly for 74% of the county. The total carbon storage increased from 6470.72 Gg in 2000 to 7335.07 Gg in 2016. Spatially, carbon density in the south of this county was greater than the northern part. Directly induced by the GGP (conversions of farmlands to forests and grasslands), the carbon storage increased by 786.84 Gg in total, with a rate of 46.28 Gg per year, the majority of which occurred during the first stage of the study period (from 2000 to 2008). The increase of carbon storage was mostly attributable to the increases in vegetation pool and the carbon density showed a strong spatial correlation with the growing season Normalized Difference Vegetation Index (NDVI). The similarities between carbon density and NDVI spatial patterns during the study period may have been shaped by the county's climate patterns, but not to any significant extent by climate change during the study period. This county-scale study allows for a deeper understanding of the links between LUCC induced by environmental restoration programs and carbon storage changes, and contributes to a greater accuracy in the estimation of carbon storage at the provincial (or larger) scale.

Estimation of initiation thresholds and soil loss from gully erosion on unpaved roads on China's Loess Plateau

AbstractGullies form easily on unpaved road surfaces during heavy rainstorms on China's Loess Plateau. The integrated effect of rainfall, topography, vegetation, land use, and other factors determines where and when gully erosion occurs; however, the mechanisms driving gully erosion on unpaved road surfaces need to be further understood. Repeated gully erosion on some roads during the storm season provides a good opportunity to better understand the mechanisms behind gully erosion. This article aimed to quantify the integrated threshold conditions required for gully initiation in terms of topography, event rainfall, and upslope land use, and to propose an event‐based model to predict the position and magnitude of road gully erosion. Rill and gully erosion on unpaved roads were investigated after an extreme rainstorm of 212.2 mm in 2017 and a regular rainstorm of 83.8 mm in 2018. A digital surface model (DSM) derived from unmanned aerial vehicle (UAV) images was used to analyze the road gradient (S) and upslope area (A). The runoff (QRS) of each road segment (RS) was estimated by the runoff curve number method. The results showed the following: (1) The mean and total gully volumes under the regular rainstorm were only 26.3% and 8.1% of those under the extreme rainstorm, respectively; (2) Gully formation on the surveyed roads under both the regular and the extreme rainstorm could be explained by the threshold relationship (S − 0.056)QRS3.363 ≥ 72.444; and (3) A non‐linear relationship between gully erosion in road segments and event runoff (QRS) and road gradient (S) was found, and was subsequently used to predict road gully erosion on an event basis.

Long-term straw mulching with nitrogen fertilization increases nutrient and microbial determinants of soil quality in a maize–wheat rotation on China's Loess Plateau

Mulching and nitrogen (N) fertilization are essential to increase crop yields in semiarid drylands. However, their long-term effects on soil physicochemical properties, extracellular enzyme activities, microbial community structure, and therefore soil quality via developing a soil quality index (SQI) remain largely unexplored. Hence, we analyzed soils after 14 years of mulching (CT, no mulch; RF, plastic film-mulched ridges and straw mulched-furrows; SM, straw mulching) and N fertilization (0, 120 and 240 kg ha−1) treatments in a maize–wheat rotation on China's Loess Plateau. Compared with CT, RF and SM significantly increased soil moisture content (SMC), organic carbon (SOC), phosphatase, and total phospholipid fatty acids (PLFAs). Compared with RF, SM increased SOC, total N, available phosphorus (AP), available potassium (AK), β-glucosidase, N-acetyl-glucosaminidase (NAG), peroxidase, and cellobiohydrolase, gram-negative bacteria (G−), and fungi. Consequently, the SQI was highest in SM (0.698), followed by RF (0.642) and CT (0.620). Nitrogen fertilization significantly increased total N, NO3−, microbial biomass N, α-glucosidase, NAG, total PLFAs, and G−, but caused a significant decline in pH, AP, AK, and the G+:G− ratio. Averaged across N-fertilizations, the SQI was ranked N240 (0.680) > N120 (0.650) > N0 (0.630). Redundancy analysis showed that SOC was closely associated with enzyme activities, whereas NO3−, SOC, and SMC were the key variables regulating microbial community composition. Structural equation model indicated that mulching and N fertilization strongly and positively affected SQI by regulating soil available N, P, and K, enzyme activities, and microbial communities, and the total effect of mulching (0.62) on SQI was greater than that of N addition (0.34). Collectively, the highest SQI observed in the SM + N240 treatment suggested that straw mulch, rather than plastic-film mulch, combined with high N addition could be a sustainable land management practice that improves soil quality in semiarid dryland farming systems.

Rare prokaryotic sub-communities dominate the complexity of ecological networks and soil multinutrient cycling during long-term secondary succession in China's Loess Plateau

Unraveling the succession of microbial communities is a core ecological research topic. Yet few studies have focused on how long-term secondary succession affects the functional profiles and ecological processes of abundant and rare microbial subcommunities. Here, we used amplicon sequencing and GeoChip analysis to explore the ecological functions of abundant and rare biospheres and their correlation with soil multinutrient cycling. Samples for this study were collected from a well-established secondary succession chronosequence that spans >30 years of dryland ecosystem development on the Loess Plateau of China. Although both abundant and rare subcommunities shifted with succession, the changing of beta-diversity of the microbial communities was primarily driven by species replacement of the rare biosphere. Phylogenetic changes of abundant and rare taxa were associated with their functional traits, which dominated the diversity-related selection along all succession ages. Neutral theory analysis indicated that the assemblage of abundant taxa over all successional ages was regulated by dispersal homogenizing and ecological drift. The null model revealed that homogeneous and variable selection were the dominant assembly processes for rare subcommunities compared with abundant species. pH and nitrogen content were the paramount drivers determining the assembly of microbial communities and functional genes, consistent with the importance of environmental filtering. Furthermore, the rare biosphere had a paramount role in the entire ecological network and was the major driver for most soil processes such as C, N, and S cycling. Nonetheless, a significant portion of soil P cycling was regulated by abundant taxa. Collectively, our study provides insight into the mechanisms underlying microbial community assembly and soil microbe-driven functional changes in biogeochemical processes during secondary succession.

Effects of vegetation and climate on the changes of soil erosion in the Loess Plateau of China

Soil erosion is simultaneously driven by multiple factors. Identifying the dominant controlling factors and quantifying the contribution of each factor would be helpful to sustain water and soil resources. China's Loess Plateau was taken as an example area to investigate the above issues since it is the most eroded region in the world, and its soil loss is being controlled by a large-scale revegetation program. We extended the Revised Universal Soil Loss Equation (RUSLE) to large-scale erosion estimation with the aid of GIS for the period of 1986–2015, analyzed the relationship between erosion and controlling factors by correlation and wavelet coherence analysis, and quantified the contribution of each factor to erosion change by the elasticity coefficient method. Results showed that the soil erosion decreased from 1013 t·km−2·a−1 in 1991–1995 to 595 t·km−2·a−1 in 2011–2015, with a downward trend in the whole period. Spatially, most areas had soil erosion of slight intensity, and the areas with high-intensity erosion concentrated in a northeast-southwest strip with hilly-gully landscapes or densely distributed rivers. The changes in surface conditions including vegetation cover and soil conservation measures had dominant effects on the spatial heterogeneity of erosion, their contribution to erosion reduction was 119%. But rainfall erosivity increased soil erosion, and it had a contribution to erosion reduction of −28%. These results are helpful in understanding the mechanism behind the changes in soil erosion and providing information for sustainable soil and water management and vegetation restoration.

Spatial variation and influencing factors of the effectiveness of afforestation in China's Loess Plateau

Payment for ecosystem services (PES) has become a widely accepted strategy for combining environmental conservation or restoration with socioeconomic development. Understanding the spatial heterogeneity of the effects of PES programs and their influencing factors is necessary for the design and implementation of effective programs. However, few researchers have both distinguished the effects of PES and analyzed their spatial variation simultaneously. Here, we analyzed the spatial differences in the effectiveness of afforestation under China's Grain-to-Green Program (GTGP), a well-known PES program, in the Loess Plateau. The approach is based on remote sensing data and county-level statistical data, which reflects the basic implementation unit of the GTGP. We identified several local and non-local influencing factors: the aridity index, rural non-farm employment, and rural migration improved afforestation effectiveness, whereas the total afforestation degree (the cumulative area of afforestation divided by the total area), vegetation conditions before afforestation, grain production, and investment in fixed assets decreased its effectiveness. Based on our results, we propose several suggestions for improvement: preferring afforestation in humid counties with low vegetation cover, identifying an optimal degree of afforestation, and promoting the transformation of rural livelihoods. Our study provides a general approach to analyze the effectiveness of PES and its spatial variation, thereby providing insights into future PES programs both within China and around the world.

Impacts of deep-rooted fruit trees on recharge of deep soil water using stable and radioactive isotopes

Deep-rooted fruit trees mine more water from deep soils than their shallow-rooted counterparts. Understanding how deep soil water (DSW) is replenished and subsequently depleted by deep-rooted fruit trees, therefore, are important for informing sustainable water resources management particularly in arid regions. In this study, we collected soil samples from the surface down to 20 m under four land use types (farmland, 8-year apple orchard, 12-year peach orchard, and 25-year apple orchard) in China's Loess Plateau. We then measured the soil water content, stable (δ2H and δ18O) and radioactive (3H) isotopic compositions. The radioactive isotope was used to constrain the age of soil water while the stable isotopes were used to determine the types of storms that would have contributed to recharging the DSW. We then implemented a soil water balance model to identify the mechanisms underlying the changes in DSW. Mechanistically, our results show that water movement in these soils was predominantly via piston flow. The age of DSW below 8 m was determined to be older than 55 years. Altogether, these results support an interpretation that DSW may have only been recharged by high-intensity, low-frequency rainfall events during the wet season (July to September), but that the magnitude of DSW recharge was likely to be influenced by subsequent water mining by deep-rooted fruit trees. The deep-rooted fruit trees consumed more DSW than farmland vegetation, substantially limiting the magnitude of DSW recharge under the orchards. Our simple soil water balance model, informed by water stable isotopes and supplemented with information from tritium, provides a technique for partitioning soil water balance (SWB) and insights into the long-term effects of land use change on water resources in arid regions.

The design of the slow-moving system of the new cave building based on the concept of "slow city"

This paper fully discusses the design method of the slow-moving system of new cave buildings based on the concept of "slow city" by various modes of passage and road design, slow-moving system plant design, landscape node design, ecological facilities and so on. Cave architecture is an important part of native architecture, mainly distributed in china's loess plateau area, which is an ancient form of living. With the development of the times, the new cave building is still full of vitality. Based on the concept of "slow city", the design method of construction creates a slow-moving system into its landscape construction. The design follows the principles of regionality, ecology, humanization and emotion.

Responses of soil ammonia-oxidizing bacteria and archaea to short-term warming and nitrogen input in a semi-arid grassland on the Loess Plateau

Ammonia-oxidizing archaea (AOA) and bacteria (AOB) predominantly control ammonia oxidation, the first and rate-limiting step of nitrification, and critically affect plant utilization and the fate of reactive nitrogen (N) input to soil. Both AOA and AOB are often sensitive to environmental changes, but their responses to the concurrent climate warming and N input remain poorly understood, particularly in semi-arid grassland ecosystems where nitrification dominates soil N transformations. We examined the interactive effects of short-term (2-yr) warming and N input (12 g N m−2 y−1) on the abundance and community structure of AOA and AOB in a semi-arid grassland on China's Loess Plateau. Results showed that AOA abundance was significantly higher than AOB in all treatments. N input significantly increased the abundance of AOA and AOB by 32% and 521%, respectively, and induced a significant shift in the AOB community composition. Warming significantly increased the abundance of AOB by 94%, but had no impact on the AOA abundance. Warming (alone or combined with N input) did not significantly affect the community structure of AOA or AOB. These results indicated that AOB was more sensitive to N input and climate warming than AOA in semi-arid Loess grasslands. Our findings suggest that understanding the responses of AOB abundance and composition may be key to predict the N dynamics under future global change scenarios.

Towards the progress of ecological restoration and economic development in China's Loess Plateau and strategy for more sustainable development

China's Loess Plateau (LP) is one of the most typical regions with serious soil erosion. Its ecological restoration, economic development, and social progress are directly related to realizing China's national sustainable development goals (SDGs). With intensive field investigations, comprehensive analyses of statistical data, remote sensing data, and local monitoring data, this current research explored the achievements in local ecological restoration and economic development, discussed the main problems faced by the LP, and assessed the sustainable development status of the LP. Moreover, drawing from a 3C system approach (classification–coordination–collaboration), this research proposed the sustainable development strategies for more sustainable LP. We found that the LP's ecological restoration and economic development made remarkable achievements since 2000. However, the environment was still fragile and regional development was still lagging behind. In realizing SDGs, further improvements on clean water and sanitation, decent work and economic growth, industry, innovation and infrastructure, reduced inequalities, and climate action are needed. Coordinated and collaborated efforts are expected from multiple hierarchical levels including household, watershed, region, and nation in developing LP. Specifically, human-environment interactions should be highlighted at the household level, upstream-downstream interactions that are catering to the particular characteristics of the LP is encouraged at the watershed level, and regional and urban-rural interactions shall play an increasingly important role at the regional level. While at the national level, the central government should carry out a systematic overarching design. To better realize the goal of more sustainable LP, this research calls for (1) forming an actor-network consists of multi stakeholders, including the central government, local government, watershed, families, ecosystem and environment, enterprises, NGOs, and scientists, and (2) paying attention to ecosystem management, ecological restoration, industrial structure optimization, ecological agriculture, rural infrastructure, and ecological civilization construction in the future development.