Loess Plateau Of Northwestern China Research Articles

Automatic and Efficient Detection of Loess Landslides Based on Deep Learning

Frequent landslide disasters on the Loess Plateau in northwestern China have had a serious impact on the lives and production of the people in the region due to the fragile ecological environment and severe soil erosion. The effective monitoring and management of landslide hazards is hindered by the wide range of landslide features and scales in remotely sensed imagery, coupled with the shortage of local information and technology. To address this issue, we constructed a loess landslide dataset of 11,010 images and established a landslide detection network model. Coordinate Attention (CA) is integrated into the backbone with the aid of the YOLO model to capture precise location information and remote spatial interaction data from landslide images. Furthermore, the neck includes the Convolutional Block Attention Module (CBAM), which prompts the model to prioritize focusing on legitimate landslide objectives while also filtering out background noise to extract valid feature information. To efficiently extract classification and location details from landslide images, we introduce the lightweight Decoupled Head. This enhances detection accuracy for landslide objectives without excessively increasing model parameters. Furthermore, the utilization of the SIoU loss function improves angle perception for landslide detection algorithms and reduces the deviation between the predicted box and the ground truth box. The improved model achieves landslide object detection at multiple scales with a mAP of 92.28%, an improvement of 4.01% compared to the unimproved model.

Quantification of the effects on the flow velocity caused by gramineous plants in the loess plateau in North-Western China

Accurate prediction of the mean velocity of overland flow is the premise and foundation for establishing a soil erosion model, but it is difficult to accurately estimate the mean flow velocity with the presence of vegetation. To explore the variation law of the mean velocity of overland flow under the influence of gramineous plants typical in the Loess Plateau in North-Western China, indoor scouring tests with ten levels of vegetation coverage (9.42 %–94.25 %), seven unit discharges (0.278–1.667 L·m−1·s−1), and five slope gradients (4°–12°) were performed. The results showed that the mean flow velocity initially increased and then decreased with an increase in vegetation coverage, and the critical cover was affected by the unit discharge. For a slope of 4°, the mean flow velocity with a vegetation coverage of 94.25 % was only 21.6 %–32.0 % of that on a bare slope, indicating that vegetation can effectively reduce flow velocity. For each experiment conducted, with an increase in vegetation coverage, the overland flow gradually moved from laminar flow to transitional flow. Based on the principle of equivalent roughness and Manning's equation, a prediction model was also established in order to predict more accurately the mean velocity associated with overland flow, and it has been validated against the experimental results demonstrating a satisfactory agreement with the measured values (adj.R2 = 0.879, NSE = 0.867). These results provide further insights regarding the influence that the vegetation can have on the flow velocity and contribute to develop a better management of these environmental areas.

Pepino (Solanum muricatum) Metabolic Profiles and Soil Nutrient Association Analysis in Three Growing Sites on the Loess Plateau of Northwestern China

Different soil nutrients affect the accumulation characteristics of plant metabolites. To investigate the differences among the metabolites of pepino grown in greenhouses on the Loess Plateau in northwest China, we investigated the main soil nutrients and their correlation with metabolites. A total of 269 pepino metabolites were identified using UPLC-QTOF-MS to detect metabolites in fruits from three major pepino growing regions and analyze their differential distribution characteristics. A total of 99 of these substances differed among pepino fruits from the three areas, and the main classes of the differential metabolites were, in order of number: amino acids and derivatives, nucleotides and derivatives, organic acids, alkaloids, vitamins, saccharides and alcohols, phenolic acids, lipids and others. An environmental factor analysis identified soil nutrients as the most significant differentiator. Five soil nutrient indicators: TN (total nitrogen), TP (total phosphorus), AP (available phosphorus), AK (available potassium), and OM (organic matter), exhibited significant differences in three growing sites. Metabolite and soil nutrient association analysis using redundancy analysis (RDA) and the Mantel test indicated that TN and OM contributed to the accumulation of amino acids and derivatives, nucleotides and derivatives, and alkaloids while inhibiting organic acids, vitamins coagulation biosynthesis. Moreover, AP and TP were associated with the highest accumulation of saccharides and, alcohols, phenolic acids. Consequently, differences in soil nutrients were reflected in pepino metabolite variability. This study clarified the metabolite variability and the relationship between pepino and soil nutrients in the main planting areas of northwest China. It provides a theoretical basis for the subsequent development of Pepino’s nutritional value and cultivation management.

Straw strip mulching: A sustainable technology for saving water and improving efficiency in dryland winter wheat production

An improved straw mulching model may be a sustainable agricultural production technology due to its improvements in soil water and the fertilizer environment by the recycling of waste straw resources. A four-year field experiment was conducted in a randomized block design on the Loess Plateau of northwestern China in 2015–2019, which aimed to study the effects of straw strip mulching (SSM) and conventional flat planting without mulching (CK) on soil water storage, water consumption characteristics, water use efficiency, precipitation use efficiency, winter wheat growth, economic benefits, and nutrient benefits. The results obtained for the four years showed that the SSM treatment improved soil water storage in the 0–180 cm soil layer over the whole growth period, which was especially obvious in the 0–60 cm soil layer at the jointing and blooming stages. Compared with CK, SSM increased the contribution rate of precipitation to total evapotranspiration and increased it quite significantly by 20.4 percentage points in the earlier growth period. SSM significantly reduced soil water storage consumption in the 0–180 cm soil layer and ultimately reduced evapotranspiration by 11.2 mm during the whole period. In the 0–180 cm soil layer, SSM decreased evapotranspiration by 33.1 mm from the sowing to the jointing stages, but increased it by 19.5 mm from the jointing to the blooming stages. In addition, SSM improved the water use efficiency of grain yield by 21.6% and improved the precipitation use efficiency of grain yield by 18.6%, and it ultimately increased grain yield by 16.5% through improving spike number by 9.5% and kernel number per spike by 8.9%. SSM improved the water use efficiency of biomass yield by 13.5% and the precipitation use efficiency of biomass yield by 9.9%, and it ultimately increased biomass yield by 8.7% and plant height by 6.5%. Furthermore, SSM increased net income by 413 CNY ha–1 and the total amount of straw returned to the field after harvest by 8 876–9 619 kg ha–1. After returning straw to the field, SSM significantly increased the soil nutrient contents, which could significantly reduce the burden of fertilization by farmers after a few years. Therefore, straw strip mulching technology could probably be a sustainable and potentially useful practice, which could save water and increase efficiency in rainfed winter wheat production.

Distribution and Characteristics of Damming Landslides Triggered by 1920 M~8 Haiyuan Earthquake, NW China

Earthquake-triggered damming landslides threaten downstream residents and affect the regional landscape by disrupting water and sediment fluxes. Therefore, it is essential to study the distribution characteristics and distinctive controlling factors of earthquake-triggered damming landslides to provide a reference for treating landslide dams caused by damming landslides. This study uses the 1920 M~8 Haiyuan earthquake-triggered landslides as an example to study the characteristics and topographic effects of damming landslides in the Loess Plateau in Northwestern China. A detailed Haiyuan-earthquake-triggered damming landslide inventory was established. The statistics of terrain, geology, seismic factors, and information gain rankings were used to quantify the significance of the controlling factors. The aspect ratio, equivalent coefficient of friction, area, and slope position was calculated. Damming landslides’ distinctive geomorphic and morphological characteristics were summarized through comparisons with non-damming landslides. The results showed that damming landslides were concentrated in areas with thick loess sediment, low relief, and close proximity to a river. Loess thickness was the most critical control factor among them. Damming landslides have the geomorphological characteristics of a large ratio of length to width (L/W), a low ratio of height to length (H/L), large scales, and entire-slope failure. Moreover, damming landslides can transform the topography of the Loess Plateau through their long-term effects. These findings highlight the characteristics of damming landslides in the Loess Plateau and supplement the global landslide dam inventory. They provide a reference for assisting in earthquake-triggered damming landslides treatments in the Loess Plateau.

Optimum fertilizer application rate to ensure yield and decrease greenhouse gas emissions in rain-fed agriculture system of the Loess Plateau

Application of nitrogen (N) can increase the supply of N in soil and, in turn, can lead to higher yield—but also to large increase in emissions of greenhouse gases (GHGs) if applied in excess. To determine the optimum dose of N for maize planting system, we analysed the relationship between yield and emissions of GHGs at seven levels of N, namely 50, 100, 150, 200, 250, 300, and 350 kg ha−1, using the DNDC (denitrification decomposition) model and maize grown with and without mulching. The model simulated the following variables: maize production; emissions of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4); global warming potential (GWP); and GHG intensity (GHGI). We used data from 1980 to 2013 for a rain-fed region of the Loess Plateau in north-western China and validated the DNDC model against data from field experiments. The model performed well in simulating yield and GHG emissions (Adj.R2 > 0.61). Under mulching, the average yield of maize was 3.6–12.2 t ha−1 and the partial factor productivity was 73.1–35.0 kg kg−1; and both of these were significantly higher 78%–236% than those in the crop without mulching. The emissions of CO2, N2O, and the GWP increased with the increase in the dose of N whereas CH4 emissions remained unaffected by the dose. Mulching increased yields significantly in the north-western region, and the GWP and GHGI were higher mainly in the central and north-western regions. The optimum dose of N for maize grown with mulching ranged between 150 kg ha−1 and 200 kg ha−1 and offers the best balance between higher yield and lower emissions. The optimum dose may promote the development of mulched maize and provide a reference standard for dryland agriculture in zones with similar climates elsewhere in the world.

Monitoring of soil moisture and temperature distributions in seasonally frozen ground with fiber optic sensors

The evolution of moisture and temperature fields plays an important role in governing soil behavior, which heavily influences the performance of infrastructures built on the ground soil. However, conventional geotechnical instrumentation presents many limitations in the monitoring of seasonally frozen soils in cold regions. This study investigates the feasibility of actively heated fiber Bragg grating (AH-FBG) in measuring the temperature, water content, and ice content of seasonally frozen soil through laboratory tests and field monitoring. The working principle of the AH-FBG monitoring system is introduced in detail. A series of laboratory calibration tests were performed on soil specimens to explore its performance. Long-term in-situ monitoring was carried out on the Loess Plateau in northwestern China. Results show that the AH-FBG technique can be applied to measure the total water content of soils using the Côté and Konrad model. In the field monitoring, the freezing-thawing process of frozen soil was captured by measuring soil temperatures and ice contents during field monitoring, and the maximum freezing depth was deduced. The AH-FBG technique is verified to be a powerful tool in estimating the actual behavior of in-situ ground soil and provides rich information on multi-field interactions in cold regions.

Increased precipitation enhances soil respiration in a semi-arid grassland on the Loess Plateau, China.

BackgroundPrecipitation influences the vulnerability of grassland ecosystems, especially upland grasslands, and soil respiration is critical for carbon cycling in arid grassland ecosystems which typically experience more droughty conditions.MethodsWe used three precipitation treatments to understand the effect of precipitation on soil respiration of a typical arid steppe in the Loess Plateau in north-western China. Precipitation was captured and relocated to simulate precipitation rates of 50%, 100%, and 150% of ambient precipitation.Results and DiscussionSoil moisture was influenced by all precipitation treatments. Shoot biomass was greater, though non-significantly, as precipitation increased. However, both increase and decrease of precipitation significantly reduced root biomass. There was a positive linear relationship between soil moisture and soil respiration in the study area during the summer (July and August), when most precipitation fell. Soil moisture, soil root biomass, pH, and fungal diversity were predictors of soil respiration based on partial least squares regression, and soil moisture was the best of these.ConclusionOur study highlights the importance of increased precipitation on soil respiration in drylands. Precipitation changes can cause significant alterations in soil properties, microbial fungi, and root biomass, and any surplus or transpired moisture is fed back into the climate, thereby affecting the rate of soil respiration in the future.

Runoff and soil and nutrient losses from gravel mulching: A field experiment with natural rainfall on the Loess Plateau of China

Gravel mulch has been used effectively to conserve agricultural water for three centuries in the semiarid Loess Plateau of northwestern China. In this study, gravel mulch field experiments on the slopes of the plateau were carried out to evaluate the effects of different particle sizes of gravel mulch and different slope gradients on surface runoff, soil erosion, and nutrient losses under natural rainfall throughout 2017 and 2018. Experiment plots (3 m × 5 m) on slopes of 5°, 10°, 15°, and 30° were implemented; in each plot, three gravel mulch treatments were investigated: fine gravel (2 to 5 mm in size, FG), coarse gravel (40 to 60 mm, CG), and the control that lacked any mulching (CK). We found that gravel mulching on soil significantly reduced both the amounts of runoff and soil loss under natural rainfall conditions in 2017 and 2018, for which the soil loss-suppression effect was most pronounced under FG mulching. Applying FG also significantly increased the rainfall threshold to generate runoff, and caused the fewest runoff events during the two years of monitoring. Coarse gravel mulching caused a strong reduction in soil loss on the relatively flat slopes (i.e., 5° and 10°) whereas its effect was weak on relatively steep slopes (i.e., 15° and 30°). The respective effects of FG and CG mulching on the losses of various nutrients from soil also differed markedly. The gravel mulching significantly increased the amounts of total nitrogen (TN), potassium (K), and nitrate-nitrogen (NO₃-N) in the runoff but greatly decreased those of iron (Fe), copper (Cu), and zinc (Zn). Furthermore, the amount of nutrients lost in runoff increased with a steeper slope, with notably greater variability of nutrient elements in the runoff on the steepest slopes. Accordingly, FG mulching is recommended for use in arid and semiarid areas from the perspective of water, soil, and nutrient conservation.

Effects of gravel-sand mulch on the runoff, erosion, and nutrient losses in the Loess Plateau of north-western China under simulated rainfall

Gravel mulching is a characteristic agricultural technique that has been used for hundreds of years in the north-western Loess Plateau of China. However, the effects of the gravel-sand mulch on the processes of the runoff, soil erosion, and nutrient losses are neither fully distinguished nor even known in many parts of the world. This study investigated how different gravel particle sizes in the mulch affected the runoff, erosion as well as the extent of the nutrient losses in the surface runoff. The laboratory experiments were conducted using a rainfall simulator with three gravel mulch treatments: (1) fine gravel mulch (FG); (2) medium gravel mulch (MG); (3) coarse gravel mulch (CG) and a control group, bare soil (BS). The results of these rainfall simulation experiments gave estimates on how the grain size influences the runoff and losses of the soil and its nutrients. Applying the gravel mulch significantly delayed the runoff’s starting time when compared with the bare soil. Both the total runoff and soil loss increased with the grain size of the gravel mulch. Compared with the bare soil, the lowest surface runoff and soil loss was observed from the fine gravel treatment. These results clearly show that gravel mulch plays an important role in the runoff and sediment generation processes, and that it significantly reduces the surface runoff and soil loss. The losses of the total nitrogen (TN), total phosphorus (TP), and total organic carbon (TOC) from the bare soil were much higher than those under the gravel mulching. The fluctuations in these nutrient-loss processes were the most intense in the CG treatment, while the TC content, in initial runoff, was significantly higher in the FG than the other treatments. Our findings suggest gravel mulch is a useful water and soil conservation technique in the loess area of north-western China, and these results can inform one on the theoretical principles for properly utilising gravel-mulched fields.

Long-term effects of gravel mulching and straw mulching on soil physicochemical properties and bacterial and fungal community composition in the Loess Plateau of China

Gravel and straw mulching are the most effective and widely used surface coverage practices used to mitigate drought stress and soil erosion in Loess Plateau of northwestern China. Unlike for straw mulching, however, benefits of gravel mulching fluctuate on a long-term scale, possibly leading to soil degradation. Here we investigated variation in soil physicochemical properties and the bacterial and fungal communities in soil after 10 years of applied gravel mulching (GM), straw mulching (SM), and non-mulching (CK). Proteobacteria (30.46–31.39%) was the most abundant phylum in all three treatments. We found Actinobacteria (19.10–24.92%) enriched in both GM and SM soils, while Acidobacteria (13.53–19.42%) had a higher relative abundance in gravel mulching soil only. A heatmap and principal component analysis (PCA) revealed that gravel or straw mulching significantly changed the soil bacterial and fungal community structure. Soil fungal community is more sensitive to gravel than straw mulch applications, under SM, the relative abundance of Mortierellomycota and Glomeromycota phyla increased while that of Ascomycota was decreased. In-depth taxonomic analysis of Proteobacteria demonstrated that the relative abundance of the class Alphaproteobacteria in straw mulching soil significantly exceeded that in the non-mulching soil. Comparing the three treatments, relative abundances of Nitrosomonadaceae family members were significantly higher in gravel mulching soil, while those of Steroidobacteraceae were significantly higher in the non-mulching soil. Redundancy analysis (RDA) suggested pH and soil water content were key factors driving these long-term changes in soil bacterial community structure.

Drought stress-induced autophagy gene expression is correlated with carbohydrate concentrations in Caragana korshinskii.

Autophagy has been reported to be an adapt function of plant cells under various stresses. In this report, autophagy-related gene expressions and carbohydrate concentrationsin Caragana korshinskii leaf cells under drought stress were investigated. Leaf samples of C. korshinskii plants of an estimated 15-year-old were collected from three sites with different drought stress (annual precipitation range, 325.8 to 440.8mm) at the Loess Plateau in northwestern China. Autophagy was observed in C. korshinskii samples from all three sites and was revealed by autophagosomes in the cytoplasm of mesophyll cells and increased chloroplasts degradation observed by transmission electron microscopy. Furthermore, with the drought stress increase, autophagy-related gene expressions were upregulated and leaf concentration of sucrose was increased, while concentrations of monosaccharide sugars such as glucose, fructose and galactose were decreased. The results suggested that drought stress induced autophagy gene expression, which may serve as a survival mechanism for nutrient remobilisation.

Pollution characteristics of toxic metals in topsoil of small and medium-sized cities in mountainous areas of loess plateau in china——A case study of Guyuan

Urban soils are subjected to large number of pollutants (including toxic metals). This study investigated the urban soil environmental quality of Guyuan (a typical mountainous city in the Loess Plateau of northwestern China) by determining the concentrations of eight toxic metals (Cu, Zn, Cd, Pb, Cr, Ni, Mn, and Co) in urban topsoil as well as their potential sources. The toxic metal contents in the urban topsoil of Guyuan were generally less than those of other cities in northwestern China. Majority of the metals were highly concentrated in commercial and residential areas at the centre of Guyuan and the industrial region in southeastern Guyuan. The results of our study can contribute towards controlling, managing, and preventing soil pollution, as well as implementing safe layouts for the development of mountainous cities from the planning stage itself.

Effects of different tillage and straw retention practices on soil aggregates and carbon and nitrogen sequestration in soils of the northwestern China

Soil tillage and straw retention in dryland areas may affect the soil aggregates and the distribution of total organic carbon. The aims of this study were to establish how different tillage and straw retention practices affect the soil aggregates and soil organic carbon (SOC) and total nitrogen (TN) contents in the aggregate fractions based on a long-term (approximately 15 years) field experiment in the semi-arid western Loess Plateau, northwestern China. The experiment included four soil treatments, i.e., conventional tillage with straw removed (T), conventional tillage with straw incorporated (TS), no tillage with straw removed (NT) and no tillage with straw retention (NTS), which were arranged in a complete randomized block design. The wet-sieving method was used to separate four size fractions of aggregates, namely, large macroaggregates (LA, >2000 μm), small macroaggregates (SA, 250–2000 μm), microaggregates (MA, 53–250 μm), and silt and clay (SC, <53 μm). Compared to the conventional tillage practices (including T and TS treatments), the percentages of the macroaggregate fractions (LA and SA) under the conservation tillage practices (including NT and NTS treatments) were increased by 41.2%–56.6%, with the NTS treatment having the greatest effect. For soil layers of 0–5, 5–10 and 10–30 cm, values of the mean weight diameter (MWD) under the TS and NTS treatments were 10.68%, 13.83% and 17.65%, respectively. They were 18.45%, 19.15% and 14.12% higher than those under the T treatment, respectively. The maximum contents of the aggregate-associated SOC and TN were detected in the SA fraction, with the greatest effect being observed for the NTS treatment. The SOC and TN contents were significantly higher under the NTS and TS treatments than under the T treatment. Also, the increases in SOC and TN levels were much higher in the straw-retention plots than in the straw-removed plots. The macroaggregates (including LA and SA fractions) were the major pools for SOC and TN, regardless of tillage practices, storing 3.25–6.81 g C/kg soil and 0.34–0.62 g N/kg soil. Based on the above results, we recommend the NTS treatment as the best option to boost soil aggregates and to reinforce carbon and nitrogen sequestration in soils in the semi-arid western Loess Plateau of northwestern China.

Modification of Vertical Earth Pressure Formulas for High Fill Cut-and-Cover Tunnels Using Experimental and Numerical Methods

The high-filled cut-and-cover tunnel (HFCCT) is a solution to reclaim more useable lands due to the unique landforms of Loess Plateau in northwestern China. Because of the ultrahigh backfill, the estimation of vertical earth pressure will significantly affect the design and safety of the cut-and-cover tunnel (CCT). The current methods for estimating the vertical earth pressure are either to overestimate or underestimate the vertical earth pressure on the top of HFCCT. To more precisely estimate the vertical earth pressure distribution, the vertical earth pressure based on the soil column pressure,γh(h: the height of backfill above the CCT), needs to be properly modified. Considering different influential factors, four corresponding coefficients are proposed:k0: cross-sectional shape of CCT effect,k1: stiffness of backfill effect,k2: width of CCT effect, andk3: coupling effect of slope angle,θ,and the ratio of B/D. It is found thatk0has little influence; thek3andk1reduce andk2amplifies theγh. The corresponding general forms for these coefficients are determined based on finite element analysis results. A general equation for estimating vertical earth pressure for the HFCCT including these four coefficients is proposed. Meanwhile, this general form is verified by the numerical analysis results and experimental results for different cases. Therefore, this proposed equation is applicable to estimate the vertical earth pressure for existing or newly designed HFCCT. Furthermore, this proposed method can significantly reduce the computational work in engineering analysis.

Architectural and anatomical responses of maize roots to agronomic practices in a semi‐arid environment

AbstractRoot architecture and anatomy are important determinants of nitrogen (N) and water acquisition, but they are also environmentally plastic to adapt to N and water availability. Therefore, understanding the relationship between root traits and environmental factors is essential for improving N and water acquisition. A field experiment was conducted in the semi‐arid region of the Loess Plateau in northwestern China to quantify the architectural and anatomical root traits of maize (Zea mays L.) in response to plastic film mulching and N fertilization. We compared four treatments: non‐mulching with and without N supply as well as plastic film mulching with and without N supply. Variation existed for all root architecture and anatomy traits within maize root crowns. Crown and brace root angles to the soil line decreased in response to film mulching and N fertilization. Crown roots under plastic film mulching showed a significantly decreased distance to branching, reduced lateral root length, and overall increased root diameter. Similarly, N application significantly decreased the distance to branching, yet induced more compact and denser crown roots, and increased the root diameter. Brace roots exhibited an increased distance to branching, greater lateral root length and density, as well as a larger root diameter in response to plastic film mulching and N fertilization. Additionally, the accumulated number of nodal roots increased greatly under plastic film mulching and N treatments. At the anatomical level, N application reduced the proportion of the root cortical aerenchyma area. In contrast, aerenchyma area, cortex cell size, and late metaxylem vessel diameter were increased as a result of plastic film mulching. These results demonstrate root architectural and anatomical traits respond to mulching practices and N fertilization.

N2-fixing black locust intercropping improves ecosystem nutrition at the vulnerable semi-arid Loess Plateau region, China

The Loess Plateau in northwestern China constitutes one of the most vulnerable semi-arid regions in the world due to long-term decline in forest cover, soil nutrient depletion by agricultural use, and attendant soil erosion. Here, we characterize the significance of N2-fixing Robinia pseudoacacia L. and non-N2-fixing Juglans regia L. for improving nutrient availability and water retention in soil by comparing a range of biological and physicochemical features in monoculture and mixed plantations of both species. We found that N2-fixing Robinia facilitates the nitrogen and phosphorus composition of non-N2-fixing Juglans in the mixed stand as a consequence of improved soil nutrient availability, evident as higher levels of nitrogen and labile carbon compared to mono-specific stands. This demonstrates that intercropping N2-fixing Robinia with non-N2-fixing woody plants can greatly improve soil carbon and nitrogen bioavailability as well as whole-plant nutrition and can potentially mediate water retention with additional sequestration of soil organic carbon in the range of 1 t C ha−1 year−1. Thus, intercropping N2-fixing woody species (e.g. Robinia pseudoacacia or Hippophae rhamnoides L.) with locally important non-N2-fixing tree and shrub species should be considered in afforestation strategies for landscape restoration.

Soil microbial diversity during 30 years of grassland restoration on the Loess Plateau, China: Tight linkages with plant diversity

AbstractRestoring ecosystems has been a key strategy to combat land degradation and reverse losses in biodiversity. Because interactions between communities above and below the ground drive key ecosystem processes, they can profoundly influence ecological succession trajectories. However, relatively little empirical information is available for plant–microbial diversity linkages during ecological restoration. Here, using the Illumina platform for bacterial and fungal sequencing, we investigated linkages between soil microbial and plant diversity across a 30‐year chronosequence of restored grasslands on the Loess Plateau in Northwestern China. The results showed that plant, bacterial, and fungal species richness all increased with increased years of grassland restoration, during which their community compositions shifted among six different habitats. The microbial community assembly data were integrated into a co‐occurrence network analysis, revealing greater network complexity in the late restoration stage (25 and 30 years). The alpha and beta diversities of both the bacterial and fungal communities were significantly and positively correlated with plant communities. Bacterial community composition was governed primarily by soil edaphic factors and deterministic processes, whereas fungal community composition was structured mainly by plant community composition and both deterministic and stochastic processes. This evidence strongly suggests that different ecological processes shaped bacterial and fungal communities during ecological restoration of the grasslands. Our results provide insight into the aboveground–belowground associations of restored habitats, which may have implications for ecological restoration practices and biodiversity maintenance in arid and semiarid grassland ecosystems.

Microbial residues were increased by film mulching with manure amendment in a semiarid agroecosystem

ABSTRACTAmino sugars, as a kind of microbial residue, are strongly associated with cycling of microbial-derived soil organic matter. However, responses of amino sugars to agricultural practices on the Loess Plateau in North-western China are poorly known. The objective was to evaluate effects of film mulching (no film mulching + NPK fertilizers, CK; film mulching + NPK fertilizers, PF; film mulching + NPK fertilizers + cow manure, FM) on accumulations of amino sugars in this region. FM significantly increased total amino sugar by 190.46 mg kg−1 in 0–10 cm layer and 214.66 mg kg−1 in 10–20 cm layer relative to CK, but PF significantly decreased it by 139.28 mg kg−1 in 0–10 cm layer. Ratios of glucosamine to muramic acid were markedly decreased by 2.50 in 0–10 cm layer and 2.28 in 10–20 cm layer in FM than CK, suggesting a tendency of microbial residues pool shift towards bacterial residues in this agroecosystem. These results indicated film mulching alone was not benefitial to accumulation of amino sugar while organic manure contributed to the build-up of amino sugar partly due to manure contained microbial residues. The different patterns of amino sugars suggested significant changes in the quality of microbial-derived organic matter.

Wheat Yield Affected by Soil Temperature and Water under Mulching in Dryland

Core Ideas Plastic mulch increased soil temperature and water, thus increased wheat yield. High soil temperature by plastic mulch and planting legume reduced wheat yield. Incorporation of legume increased soil temperature of next wheat growing season. Planting legume increased soil water use in summer and decreased evapotranspiration in wheat season. In the Loess Plateau of northwestern China, soil water shortage is the main factor constraining dryland wheat (Triticum aestivum L.) production. Soil mulching is considered an effective practice to improve wheat yield due to increased soil water storage, but the information related to integrated understanding of soil temperature and water is scarce. We conducted a location‐fixed field experiment with two soil mulching (plastic mulch and planting legume) treatments to confirm the effects of soil temperature and water on wheat yield under different precipitation levels. In 2014–2015 with higher than average precipitation, plastic mulch increased soil water storage by 13% at sowing and average soil temperature by 0.4°C, which in turn increased yield by 13%, compared to the control. In 2012–2013 with extremely lower than average precipitation, the high daily maximum soil temperature during wheat reproductive period decreased grain number per spike and grain weight by 16 and 4%, respectively, thus reduced yield by 16%. For planting legume, the lower soil water storage at sowing and high daily maximum soil temperature during the wheat reproductive period decreased the number of spikes per hectare and grain weight by 29 and 4%, respectively, resulting in a 37% decrease in yield in 2012–2013. In other years with relatively higher precipitation, the proper soil temperature and extra N input under planting legume alleviated the negative impact of yield decline. Overall, planting legume did not show any benefit for wheat yield, while plastic mulch provided an opportunity for increasing wheat yield in dryland.