Semi-arid Region Of China Research Articles

Optimum planting configuration for alfalfa production with ridge-furrow rainwater harvesting in a semiarid region of China

Soil desiccation is a major challenge faced by subsistence farmers growing alfalfa (Medicago sativa L) in consecutive cultivation in semiarid regions. We hypothesized that alfalfa fodder yield would increase with the length of growing season, growing degree-days, and rainfall. A field experiment was conducted on alfalfa production from 2012 to 2016 to 1) determine the response of fodder yield to rainfall, the length of growing season, and accumulated growing degree day (AGDD) in different growing-cutting stage (GCS)s; 2) obtain the suitable mulching material and the optimum ridge width for ridges with manually compacted soil (MCS), mulched with bio-degradable film (BF), and plastic film (PF). There were 10 treatments (3 ridge widths × 3 ridge-mulching materials + flat planting (FP) as control) with three replications laid in a randomized block design. The ratio of the first GCS to the second GCS in fodder yield ranged from 1.10 to 4.55, which was similar to the ratio of the first GCS to the third GCS in fodder yield ranged from 1.14 to 4.59, although rainfall, the length of growing season, and AGDD were different during the two or three GCSs. The highest fodder yield was obtained from the first GCS in one year and reached the highest level in the second growing year, and maintained a similar level in the subsequent years, although rainfall, the length of growing season, and AGDD varied during the five year periods. Fodder yield was affected by both the rainfall in the GCS and the available soil moisture prior to the GCS. Compared to FP, the increase of evapotranspiration for MCS, BF, and PF was 11, 61, and 63 mm, respectively. Fodder yield for BF and PF increased by 28% and 33%, respectively. Fodder yield for MCS maintained the same level as that for FP. Evapotranspiration increased and fodder yield decreased as ridge width increased. The optimum ridge width for MCS, BF, and PF was 29, 39, and 37 cm, respectively, across five years. Future study should focus on alfalfa-crop rotation to mitigate soil desiccation after alfalfa consecutively production.

Effects of ridge-furrow rainwater-harvesting with biochar application on sediment control and alfalfa (Medicago sativa L.) fodder yield increase in semiarid regions of China

Effects of ridge-furrow rainwater-harvesting with biochar application on sediment control and alfalfa (Medicago sativa L.) fodder yield increase in semiarid regions of China

Selection of suitable type and application rate of biochar for alfalfa (Medicago sativa L.) productivity in ridge-furrow rainwater-harvesting in semiarid regions of China

Ridge-furrow rainwater-harvesting (RFRH) has emerged as an effective technology to mitigate drought stress, control soil erosion, and increase crop yield in semiarid regions of China. However, the use of plastic film mulch in RFRH makes this technology impractical. A field experiment was conducted for three consecutive years in a randomized complete block design to determine 1) the runoff coefficient for ridges compacted with soil mixed with two types of biochar (rice straw biochar and cow dung biochar) at two application rates (single application rate i.e., 3 × 104 kg ha−1; and double application rate i.e., 6 × 104 kg ha−1; and 2) the effects of the ridges compacted with soil mixed with two types of biochar at two application rates on soil physico-chemical properties, economic benefit, fodder yield and water use efficiency (WUE) of alfalfa, and ridges compacted with soil (no biochar) as control. The average runoff coefficient for NB, SRSB, DRSB, SCDB, and DCDB (NB, SRSB, DRSB, SCDB, and DCDB were ridges compacted with soil, compacted with soil mixed with single rice straw biochar application, double rice straw biochar application, single cow dung biochar application, and double cow dung biochar application, respectively) over these three years was 31%, 28%, 27%, 22%, and 21%, respectively. Ridges compacted with soil-biochar crust had lower runoff coefficients, soil water storage, net income, and higher soil nutrients, when compared to ridges compacted with soil. The topsoil temperature at ridge tops was affected by the ridges compacted with soil-biochar crust, but the topsoil temperature at furrow bottoms was not affected. Compared to ridges compacted with soil mixed with cow dung biochar, ridges compacted with soil mixed with rice straw biochar had lower soil nutrients, and higher soil water storage resulting in higher fodder yield and WUE of alfalfa. With runoff, the nutrients in biochar flowed from ridges to furrows, becoming usable for plants. Ridges compacted with soil-biochar crust increased topsoil nutrients, especially soil organic matter ranging from 15% to 34%, resulting in high fodder yield and WUE of alfalfa. Compared to NB, annual fodder yield for SRSB, DRSB, SCDB, and DCDB increased by 9.0%, 5.9%, 4.4%, and 3.8%, respectively, over three years, while WUE for the same treatments increased by 2.81, 1.95, 0.65, and 0.45 kg ha−1 mm−1. Rice straw biochar at an application rate of 3 × 104 kg ha−1 was found to be suitable type of biochar for increase in fodder yield and WUE of alfalfa in RFRH. Future studies should be conducted in the form of long-term field study to determine economic benefits of biochar application.

Quantitative Assessment for the Spatiotemporal Changes of Ecosystem Services, Tradeoff–Synergy Relationships and Drivers in the Semi-Arid Regions of China

Ecosystem services in arid inland regions are significantly affected by climate change and land use/land cover change associated with agricultural activity. However, the dynamics and relationships of ecosystem services affected by natural and anthropogenic drivers in inland regions are still less understood. In this study, the spatiotemporal patterns of ecosystem services in the Hexi Region were quantified based on multiple high-resolution datasets, the InVEST model and the Revised Wind Erosion Equation (RWEQ) model. In addition, the trade-offs and synergistic relationships among multiple ecosystem services were also explored by Pearson correlation analysis and bivariate spatial autocorrelation, and redundancy analysis (RDA) was also employed to determine the environmental drivers of these services and interactions. The results showed that most ecosystem services had a similar spatial distribution pattern with an increasing trend from northwest to southeast. Over the past 40 years, ecosystem services in the Hexi Region have improved significantly, with the water retention and soil retention increasing by 87.17 × 108 m3 and 287.84 × 108 t, respectively, and the sand fixation decreasing by 369.17 × 104 t. Among these ecosystem services, strong synergistic relationships were detected, while the trade-offs were found to be weak, and showed significant spatial heterogeneity in the Hexi Region. The spatial synergies and trade-offs in the Qilian Mountains were 1.02 and 1.37 times higher than those in the Hexi Corridor, respectively. Human activities were found to exacerbate the trade-offs between ecosystem services by increasing water consumption in the Hexi Corridor, with the exception of carbon storage. In particular, there were significant tradeoffs between food production and water retention, and between soil retention and habitat quality in the oases of the Hexi Corridor, which is affected by rapid population growth and cropland expansion. Additionally, precipitation, temperature and vegetation cover in the Qilian Mountains have increased significantly over the past four decades, and these increases significantly contributed to the enhancements in water retention, carbon storage, habitat quality, soil retention and food production. Nevertheless, the amount of sand fixation significantly decreased, and this was probably associated with the reduction in wind speed over the past four decades. Our results highlighted the importance of climate wetting and water resource management in the enhancement of ecosystem services and the mitigation of food production trade-offs for arid inland regions.

Bentonite-humic acid improves soil organic carbon, microbial biomass, enzyme activities and grain quality in a sandy soil cropped to maize (Zea mays L.) in a semi-arid region

A bentonite-humic acid (B-HA) mixture added to degraded soils may improve soil physical and hydraulic properties, due to effects such as improved soil structure and increased water and nutrient retention, but its effect on soil physicochemical and biological properties, and grain quality is largely unknown. The effect of B-HA, added at 30 Mg ha−1, was studied at 1, 3, 5 and 7 years after its addition to a degraded sandy soil in a semi-arid region of China. The addition of B-HA significantly increased water-filled pore space and soil organic carbon, especially at 3 to 5 years after its soil addition to the soil. Amending the sandy soil with B-HA also increased the content of microbial biomass (MB)-carbon, -nitrogen and -phosphorus, and the activities of urease, invertase, catalase and alkaline phosphatase. The significant effect of maize (Zea mays L.) growth stage on soil MB and enzyme activities accounted for 58 and 84% of their total variation, respectively. In comparison, B-HA accounted for 8% of the total variability for each of the same two variables. B-HA significantly enhanced soil properties and the uptake of N and P by maize in semi-arid areas. The use of B-HA product would be an effective management strategy to reclaim degraded sandy soils and foster sustainable agriculture production in northeast China and regions of the world with similar soils and climate.

Coupling-decoupling of soil CO<sub>2</sub> and CH<sub>4</sub> fluxes and their responses to temperature in arid and semi-arid regions of China

Coupling-decoupling of soil CO<sub>2</sub> and CH<sub>4</sub> fluxes and their responses to temperature in arid and semi-arid regions of China

Fungal community diversity and driving factors in rhizosphere soil of Caragana species across semi-arid regions

To investigate fungal community diversity in rhizosphere soil of Caragana species, and their relationships with ecological factors in the semi-arid regions of China, we collected soil samples from Caragana liouana and C. microphylla in different habitats. By using Illumina MiSeq high-throughput sequencing technology, we analyzed fungal diversity, community composition, and the driving factors. Results showed that 7 phyla, 20 classes, 43 orders, 66 families, and 78 genera were recorded from the rhizosphere soil. The dominant phyla in all sample sites were Ascomycota (37.7%), Basidiomycota (13.7%), and Zygomycota (4.3%). At the genus level, Penicillium, Geomyces, and Mortierella were dominant, and Rhizophagus and Glomus were also found in rhizosphere soil. The fungal Chao1 index, ACE index, and Simpson index of C. microphylla were significantly higher than those of C. liouana. There was significant difference between the two species in the composition of fungal communities. Results of redundancy analysis showed that soil organic carbon, total nitrogen, electrical conductivity, available potassium, altitude, total phosphorus and aridity index exhibited significant impacts on soil fungal diversity. Overall, those results enhanced our understanding of the relationships between rhizospheric microbial community diversity of Caragana species and ecological factors, and provided important information on the adaptive mechanisms of desert plants in semi-arid regions.

First Report of Sea buckthorn Stem Wilt Caused by Fusarium sporotrichioides in Gansu, China.

Sea buckthorn (Hippophae rhamnoides) is an important deciduous shrub for fruit and ecological restoration in arid and semi-arid regions of China. Twelve Chinese and Russian cultivars (cv. Shenqiuhong, eshi01, ... eshi11) were planted about 1.6 acre area in a seedling nursery, located in Qingyang City of Gansu province in northwest China, where high mortality (more than 70%) of sea buckthorn was observed in late July 2019. Symptoms consisted of massive chlorosis, drooping leaves and dried-up stems on 5-year-old trees. Pieces of tree roots and stems with irregular light-brown discoloration in the xylem vessels were selected. Small pieces of discolored tissue were surface disinfested (1 min in 1% sodium hypochlorite, followed by three rinses with sterile distilled water), air-dried, and placed on potato dextrose agar (PDA) medium for 5 days at 25°C in the dark. A fungus was consistently isolated from both diseased roots and stems tissues. Colonies on PDA grew rapidly. Dense mycelia were pinky-white initially, and became carmine red color with age on the undersurface of the plate. Macroconidia were moderately curved, 3 to 5 marked septa, hyaline, thick walled, and measuring 27.8± 3.6 µm × 4.8 ± 0.5 µm (n = 30). Microconidia were abundant, pear-shaped, ellipsoid to fusoid, often with a papilla at the base, and 8.4 ± 2.2 µm ×3.1 ± 0.3 µm (n = 30). Genomic DNA was extracted for amplification and sequencing of the internal transcribed spacer region (ITS1 and ITS4 primers) (White et al. 1990) of the ribosomal DNA (Accession Nos. MN160235 to MN160238) and translation elongation factor-1 alpha (EF1 and EF2 primers, accession Nos. MN429075 to MN429078) (O'Donnell et al. 1998). The sequences revealed 99% similarity to the sequences of the ITS (AY188917), and 100% identity with EF1-α (JF740808) regions of Fusarium sporotrichioides. Based on morphological and molecular characteristics, the fungus was identified as F. sporotrichioides (Leslie and Summerell 2006). Koch's postulates were fulfilled on healthy, potted 1-year-old sea buckthorn seedings using two isolates in a greenhouse at 25 °C, 90% relative humidity, and 12-hour light/dark photoperiod. Ten potted seedings were inoculated on the stems by placing a 5-mm-diameter mycelial plug (5-day-old PDA cultures for each isolate) into the surface of a wound created with a needle, and the inoculation sites were covered with Parafilm to maintain moisture. Ten seedings were inoculated with PDA plugs as controls. Seven to ten days after inoculation, typical symptoms of dark-brown necrotic lesions on chlorotic leaf margins were observed. About 2 weeks after inoculation, the inoculated stems were gradually dry up, accompanied by withering and fallen leaves. Control plants remained asymptomatic. Pathogens were successfully isolated from the inoculated stems again, exhibiting morphological characteristics identical to those of F. sporotrichioides. Previous papers reported F. sporotrichioides as a common pathogen caused lavender wilt (Cosic et al. 2012), foliar spots on forage corn (Moya-Elizondo et al. 2013) and maize ear rot (Wang et al. 2019). To our knowledge, this is the first report of sea buckthorn stem wilt caused by F. sporotrichioides on several Chinese and Russian cultivars in Gansu province of China. In Heilongjiang province, the same disease was reported in 2010 (Song et al. 2010), nearly 30 longitudes away from Gansu province. Therefore, this disease appears to be a serious risk for future sea buckthorn production.

Response of dual‐purpose winter wheat yield and its components to sowing date and cutting timing in a semiarid region of China

AbstractDual‐purpose winter wheat (Triticum aestivum L.) has been advocated on the Loess Plateau of China to fill feed gap and integrate crop–livestock systems; however, the effects of sowing date on the recovery after cutting and interactions between various management practices are largely unclear. Field experiment was conducted in 2015–2017 in semiarid northwestern China to investigate the effects of sowing date and cutting timing on forage yield, grain yield, and its components of dual‐purpose winter wheat cultivars. The experiment combined four cutting treatments, that is, winter cutting, spring cutting, winter–spring cutting, and control, two sowing dates (22 Sept., 2 Oct.), and two cultivars (early to mid‐maturing Zhongmai and late‐maturing Longyu4). Results showed delayed sowing decreased forage yield by 33.4%, but still had the potential to produce an average of 1.6 t ha−1 of forage, with average protein content of 290 g kg−1. Response of winter wheat grain yield to cutting ranged from −38.9 to 1%, with a delay of 1–7 d in maturity. Delayed sowing induced insignificant yield penalties. More forage and higher kernel protein content were produced if crops were cut in winter–spring, but this came with large reductions (30.1% in Longyu4 and 38.9% in Zhongmai) in grain yield, mainly due to reductions in kernels per spike and kernel weight. This study suggests that Longyu4 and Zhongmai are suitable varieties for dual‐purpose winter wheat in the Loess Plateau. For higher forage and grain yield, Longyu4 is suitable for sowing in middle or late September, whereas Zhongmai is suitable for delaying sowing. Winter cutting or spring cutting is acceptable to maintain the forage and grain yield, whereas winter–spring cutting is disadvantageous to grain yield in our study area.

Impacts of Human Activities on Ecosystem Service Value in Arid and Semi-Arid Ecological Regions of China.

The quantitative and spatial–temporal variations in the characteristics of ecosystem value can be helpful to improve environmental protection and climate adaptation measures and adjust the balance between economic development and the ecological environment. The arid and semi-arid regions of China are undergoing the effects of climate change across the entire northern hemisphere. Their ecological environments are fragile and in conflict with anthropogenic activities, which significantly altered more ecosystems services in these regions. Therefore, estimating the effects of anthropogenic activities on ecosystem services is important for formulating ecological policy and regional environmental mitigation plans of these regions. This study employed the model of ecosystem service value (ESV) assessment and the bivariate spatial autocorrelation method to reveal the spatiotemporal variations in the characteristics of ecosystem value in the arid and semi-arid ecological regions of China and its interaction with human activities. Results showed that (1) the total value of ES of the study area increased from USD 487,807 billion in 2000 to USD 67,831,150 billion 2020; (2) the ES value provided by forest land first increased by 5.60% from 2000 to 2020; (3) the ESV provided by grassland showed an overall decline over the 20 years. Food and raw material production showed the lowest ES value, and climate regulation and soil conservation decreased from 2000 to 2020; (4) the index of human footprint patches decreased from 45.80% in 2000 to 17.63% in 2020, while the high and very high human footprint index areas increased significantly, mainly due to the rapid urbanization and improvement of railway networks in these areas. Spatially, the regions with high human footprint were mostly dispersed in the northeastern of China such as Shanxi and Gansu, whereas the regions with a low human footprint remained mainly located in the central and southwestern parts of China; (5) significant spatial dependencies between changes in ESV and the human footprint index were recorded. Our study could provide a scientific basis for ecosystem functions regulation and land development security in arid and semi-arid ecological regions.

The spatial relationship between ecosystem service scarcity value and urbanization from the perspective of heterogeneity in typical arid and semiarid regions of China

Rapid expansions of urban areas and the intensification of human activities have severely impacted ecosystems and ecosystem service provisions. Considering limited availability of ecosystem services, the evaluation of ecosystem service value should consider its fluctuations supply and demand due to urbanization, i.e., the ecosystem service scarcity value (ESSV). Taking typical arid and semiarid regions of China and the Ningxia Hui Autonomous Region as an example, the effects of different scarcity factors on the scarcity value of ecosystem services were compared. At the same time, a geographically weighted regression model (GWR) was developed to analyze the spatial relationships between urbanization and the scarcity value of ecosystem services. The results suggest that demand-driven scarcity is the most important factor affecting the ESSV in Ningxia, and between 1990 and 2015, the ESSV in Ningxia increased significantly, with increase being more evident from 2005 to 2015. Among the different types of ecosystem services, the scarcity values of ecosystem services such as air quality, waste treatment, soil retention, biodiversity services, and recreation and culture increased significantly from 1990 to 2015. Spatially, the total ESSV and the ESSV of different ecosystem service types exhibited evident spatial heterogeneity due, to spatial distribution characteristics of land-use type, population density and per capita GDP. The GWR modeling result shows, that the impact of urbanization on ESSV was positively correlated overall. The ESSV of food production, raw material, air quality, climate regulation and water supply are greatly affected by urbanization, while the ESSV of biodiversity services and recreation and culture are less affected by urbanization. Meanwhile, the High-Low type and Low-High type had significant aggregation effects in the study area.

Study of mesoscale NDVI prediction models in arid and semiarid regions of China under changing environments

Currently, studies analysing the relationship between climatic factors and vegetation may present some problems, including considering insufficient spatiotemporal characteristics, contradictory results and deficiencies in reflecting vegetation changes in the future. To address this, we first analysed the spatiotemporal characteristics of the impact of climatic factors on the normalized difference vegetation index (NDVI) using a multiple regression model constructed from the perspective of water deficit. Second, the two carbon emission scenarios provided by Coupled Model Inter-comparison Project phase 5 (CMIP5) were combined to predict the future vegetation conditions in China. Finally, trend analysis, Sen's slope and cycle analysis methods were employed to explore the trend of the NDVI and its spatiotemporal characteristics in the arid and semiarid regions of China. The results show that the impact of climate change on vegetation possesses distinct spatiotemporal characteristics, and the influences are different depending on the month and location. Vegetation has greened in most arid and semiarid areas of China during historical periods. In the future, NDVI variation will show a fluctuating tendency, and increasing and declining trends for the NDVI will alternately occur monthly. Although both precipitation and temperature will increase in the future, spring vegetation will be threatened by stress in some areas due to severe drought caused by the increase in evaporation, which is caused by increasing temperature. The impact of climatic factors on the amplitude and cycle of vegetation type zones varies monthly. The impact of carbon concentration on the NDVI in vegetation type zones was not significant but was relatively large in some areas. The influence of the carbon concentration on the NDVI cycle is different each month. Carbon concentration basically has no effect on amplitude.

Bentonite effects on soil physical properties and millet yield components in a semi-arid region in China

Soil structure plays a critical role in agroecosystems because it controls soil air and water capacity, nutrient availability, and crop root growth. A field experiment was conducted to evaluate the effect of bentonite on soil relative water content, soil cone penetration resistance, soil bulk density, aggregate size distribution, and millet crop yield components in a semi-arid region in northern China from 2011 to 2015. Treatments consisted of six bentonite rates (0, 6, 12, 18, 24, and 30 Mg·ha−1) applied only in the initial year. Addition of bentonite significantly increased soil relative water throughout the profile (0–60 cm) and aggregates in 0.25–2 mm class in 0–40 cm depth; it significantly decreased soil bulk density, soil cone penetration resistance, and aggregates in 0.053–0.25 mm class in the 0–40 cm depth. All of the bentonite treatments significantly increased 1000-kernel weight and panicle number up to 16% and 33%, respectively, but did not affect kernels per spike. Treatment with 24 Mg·ha−1 bentonite achieved the greatest effect on all the soil physical parameters and crop yield components averaged over all years; the highest application rate (30 Mg·ha−1) had an increasing effect over time. This study indicates that application of bentonite improves soil health in sandy-loam soil in a semi-arid region, and thus it would help promote sustainable agriculture development in regions with similar soil and climate.

Experimental Study of Runoff and Sediment Yield Affected by Ridge Direction and Width of Sloping Farmland

Water and soil losses from sloping farmlands potentially contribute to water eutrophication and land degradation. However, few studies explored the combined effects of ridge direction and ridge width on surface runoff and soil losses of sloping farmlands. Twenty-seven experimental plots (8 m long and 4 m wide) with nine treatments (three ridge direction: cross ridge, longitudinal ridge, and oblique ridge; and three ridge width: 40, 60, and 80 cm) were adopted under natural rainfall conditions for two years in the Luanhe River Basin of China. Results indicated that ridge direction had significant effects on runoff and sediment yield (p < 0.05). The ridge width had no significant effect on runoff and sediment yield. No significant interaction effect was found between ridge direction and width on runoff and sediment yield of the sloping farmland based on statistical analyses. Compared with cross-ridge (CR) tillage and oblique-ridge (OR) tillage, longitudinal-ridge (LR) tillage significantly decreased runoff by 78.9% and 64.9% and soil losses by 88.2 and 83.5%, respectively (p < 0.05). The effects of ridge directions on runoff and sediment yield were related to rainfall grade. When the rainfall grade reached rainstorm, the runoff yield under CR, LR, and SR had significant differences (p < 0.05). The runoff under LR and OR treatment was 5.16 and 3.3 times, respectively, of that under CR. When the rainfall level was heavy rain or rainstorm, the sediment yield under LR was significantly greater than that under CR. The sediment yield was 13.45 times of that under CR. Cross-ridge tillage with a ridge width of 40 cm is an optimally effective measure of soil and water conservation on sloping farmland in arid and semiarid regions of China.

Effect of cloud condensation nuclei concentration on a hail event with weak warm rain process in a semi-arid region of China

Although there are several studies on the effects of cloud condensation nuclei (CCN) concentration on convection, it requires more attention. A hail event in semi-arid China is simulated with four different CCN concentration levels, which correspond to the marine area, mid-continental, continental, and polluted background CCN concentrations. It was found that the auto-conversion of cloud water to rainwater is not significant in the simulated convection. The increase in CCN concentration was accompanied by a large number of graupel particles of smaller size, which consequently induced smaller rain droplets. It is shown that increasing CCN concentration changed the dominant average mass-weighted diameters of the graupel, hail particles and rain droplet. The number concentration of rain droplets increased with CCN concentration, corresponding to the significant evaporation during the falling process. Consequently, the maximum of rainfall on the ground did not increase. Additionally, increasing the CCN concentration does not have the same apparent impact on the size of hail particles.

Estimation and testing of linkages between forest structure and rainfall interception characteristics of a Robinia pseudoacacia plantation on China\u2019s Loess Plateau

Understanding the interaction between canopy structure and the parameters of interception loss is essential in predicting the variations in partitioning rainfall and water resources as affected by changes in canopy structure and in implementing water-based management in semiarid forest plantations. In this study, seasonal variations in rainfall interception loss and canopy storage capacity as driven by canopy structure were predicted and the linkages were tested using seasonal filed measurements. The study was conducted in nine 50 m × 50 m Robinia pseudoacacia plots in the semiarid region of China’s Loess Plateau. Gross rainfall, throughfall and stemflow were measured in seasons with and without leaves in 2015 and 2016. Results show that measured average interception loss for the nine plots were 17.9% and 9.4% of gross rainfall during periods with leaves (the growing season) and without leaves, respectively. Average canopy storage capacity estimated using an indirect method was 1.3 mm in the growing season and 0.2 mm in the leafless season. Correlations of relative interception loss and canopy storage capacity to canopy variables were highest for leaf/wood area index (LAI/WAI) and canopy cover, followed by bark area, basal area, tree height and stand density. Combined canopy cover, leaf/wood area index and bark area multiple regression models of interception loss and canopy storage capacity were established for the growing season and in the leafless season in 2015. It explained 97% and 96% of the variations in relative interception loss during seasons with and without leaves, respectively. It also explained 98% and 99% of the variations in canopy storage capacity during seasons with and without leaves, respectively. The empirical regression models were validated using field data collected in 2016. The models satisfactorily predicted relative interception loss and canopy storage capacity during seasons with and without leaves. This study provides greater understanding about the effects of changes in tree canopy structure (e.g., dieback or mortality) on hydrological processes.

Genomic Adaptive Evolution of Sand Rice (Agriophyllum squarrosum) and Its Implications for Desert Ecosystem Restoration.

Natural selection is a significant driver of population divergence and speciation of plants. Due to local adaptation to geographic regions with ecological gradients, plant populations harbored a wide range of adaptive genetic variation to enable them to survive the heterogeneous habitats. This is all the more necessary for desert plants, as they must tolerant more striking gradients of abiotic stresses. However, the genomic mechanism by which desert plants adapt to ecological heterogeneity remains unclear, which could help to guide the sustainability of desert ecosystems. Here, using restriction-site-associated DNA sequencing in 38 natural populations, we investigated the genomic divergence and environmental adaptation of sand rice, Agriophyllum squarrosum, an annual pioneer species that covers sand dunes in northern China. Population genetic structure analyses showed that sand rice could be divided into three geographically distinct lineages, namely, Northwest, Central, and East. Phylogeographic analyses revealed that the plant might originate locally in Bergen County and further differentiated into the East lineage and then the Central lineage. Ecological niche modeling found that different lineages occupied distinct ecological niches, suggesting that the ecological gradient would have triggered genomic differentiation among sand rice lineages. Ecological association study supported that the three SNPs under divergent selection were closely correlated with precipitation gradients, indicating that precipitation might be the most important stress trigger for lineage diversity in sand rice. These adaptive SNPs could be used to genotype suitable germplasms for the ecological restoration of specific desertified lands. Further analyses found that genetic structure could significantly overestimate the signals for balancing selection. Within the Central lineage, we still found that 175 SNPs could be subject to balancing selection, which could be the means by which sand rice maintains genetic diversity and adapts to multiple stresses across heterogeneous deserts and sandy lands. From a genomic point of view, this study highlighted the local and global adaptation patterns of a desert plant to extreme and heterogeneous habitats. Our data provide molecular guidance for the restoration of desertified lands in the arid and semi-arid regions of China and could facilitate the marker assistant breeding of this potential crop to mitigate climate change.

Straw incorporation with ridge–furrow plastic film mulch alters soil fungal community and increases maize yield in a semiarid region of China

The Loess Plateau is a typical dry farming area in China. Film mulching—a widely used practice in this region—can be further deplete the poor soil organic matter levels. Straw incorporation can alleviate the adverse environmental impact of film mulching and increase crop yield. However, few studies have investigated the effects of continuous straw incorporation with film mulching on the soil fungal community in the Loess Plateau of China. This study compared the effects of straw incorporation (S) and without straw incorporation (NS) under ridge–furrow plastic film mulch on fungal community structure, fungal network structure, soil quality, and maize yield in a four-year experiment. At the end of the experiment, the soil under S had greater soil fungal richness than the soil under NS. The fungal community had greater stability and complexity and more competition and cooperation between fungi under S than NS. The stochastic process played a stronger role in constructing the fungal community under NS than S. Continuous straw incorporation changed the key dominant species from Agaricomycetes, Dothideomycetes, and Leotiomycetes under NS to Ascomycetes under S. The pathogenic fungal population significantly increased by 166% under S. Changes in the soil fungal community under S were mainly affected by increasing soil moisture, total phosphorus, and total nitrogen. Continuous straw incorporation improved soil quality with increased soil urease and catalase activities and soil organic carbon and available phosphorus contents. In four years, S significantly increased the maize yield by 4–15% compared with NS treatment. In sum, continuous straw incorporation changed the fungal community composition, improved the relationships between fungal communities and soil quality, contributing to the increased maize yield under S. The results of this study could promote the sustainable development of agriculture, which has great significance for the wider application of straw incorporation in China and elsewhere.

Evaluation of Agricultural Ecosystem Service Value in Arid and Semiarid Regions of Northwest China Based on the Equivalent Factor Method

A reasonable assessment of the value of ecosystem services is an effective measure to maintain the normal operation of the ecosystem and adjust the balance between economic development and the ecological environment. With the help of the related concepts of ecosystem services, this paper establishes an evaluation framework system and adopts the widely used and comprehensive evaluation method of equivalent factors, which is a rapid accounting tool used for the evaluation of ecosystem services. The value of agricultural ecosystem services was estimated from 2008 to 2017 in a typical arid-semiarid region, and nine ecosystem service functions were analyzed. Our research showed that from 2008 to 2017 the value of agricultural ecological services in Gansu Province increased annually, and the annual growth rate in 2012 was the highest (15%). The results showed that the selection of appropriate methods could quickly and effectively evaluate the value of agricultural ecosystem services. In-depth research on the function and value of agroecological services could better promote the sustainable development of agroecosystems and maintain the balance and integrity of ecological service functions. Evaluation of the balance and integrity of agricultural ecosystem ecological service functions in arid semi-arid regions will provide recommendations for land use and sustainable development and ecological environment protection in these regions.Highlights• Agricultural ecosystem services have changed in an arid and semiarid region of China in recent decades.• We reflect the results of China's ecological progress.• This study provides advice on agricultural development of other developing countries.

Ridge and furrow rainfall harvesting can significantly reduce N2O emissions from spring maize fields in semiarid regions of China

The ridge and furrow rainfall harvesting (RFRH) system is an effective method for enhancing the rainfall water use efficiency and crop yield. Determining how the fertilization rate affects soil nitrous oxide (N2O) emissions under the RFRH system has important practical significance for improving fertilization strategies and evaluating the environmental effects of the RFRH system. Therefore, we conducted a three-year field experiment in the Loess Plateau, China, to compare the RFRH system with traditional flat planting (T) at four different fertilizer rates (no fertilizer, N:P2O5 at 150:75 kg ha–1, N:P2O5 at 300:150 kg ha–1, and N:P2O5 at 450:225 kg ha–1). Under the same fertilization level, the soil water content (SWC) and dry matter were higher under RFRH compared with T, and the nitrate nitrogen (NO3−-N) content and N2O emissions were reduced. In the two planting models, SWC and NO3−-N of each treatment and its corresponding N2O emission flux were significantly positively correlated. Under the same planting model, SWC decreased but NO3−-N and the N2O emission increased with increasing fertilization rate. SWC was the key variable affecting the N2O emission flux in the RFRH system. In addition, the grain yield under RFRH increased by 2.2–28.0%, whereas the global warming potential (GWP) and greenhouse gas intensity (GHGI) decreased by 1.0–16.1% and 13.0–56.8%, respectively, compared with T. The grain yield and GHGI had quadratic relationships with the fertilization rate. Moreover, GWP increased in a linear manner with the fertilizer rate. These findings suggest that the RFRH system is an effective tillage measure for reducing N2O emissions. When the N:P2O5 fertilization rate was 200:100 to 307:154 kg ha−1, the RFRH system could maintain a higher grain yield and reduce the N2O emissions.