Southeastern Gansu Research Articles

Analysis on Mesoscale Characteristics of a Rainstorm Process in Southeastern Gansu

Analysis on Mesoscale Characteristics of a Rainstorm Process in Southeastern Gansu

Spatial Estimation of Losses Attributable to Meteorological Disasters in a Specific Area (105.0°E–115.0°E, 25°N–35°N) Using Bayesian Maximum Entropy and Partial Least Squares Regression

The spatial mapping of losses attributable to such disasters is now well established as a means of describing the spatial patterns of disaster risk, and it has been shown to be suitable for many types of major meteorological disasters. However, few studies have been carried out by developing a regression model to estimate the effects of the spatial distribution of meteorological factors on losses associated with meteorological disasters. In this study, the proposed approach is capable of the following: (a) estimating the spatial distributions of seven meteorological factors using Bayesian maximum entropy, (b) identifying the four mapping methods used in this research with the best performance based on the cross validation, and (c) establishing a fitted model between the PLS components and disaster losses information using partial least squares regression within a specific research area. The results showed the following: (a) best mapping results were produced by multivariate Bayesian maximum entropy with probabilistic soft data; (b) the regression model using three PLS components, extracted from seven meteorological factors by PLS method, was the most predictive by means ofPRESS/SStest; (c) northern Hunan Province sustains the most damage, and southeastern Gansu Province and western Guizhou Province sustained the least.

Temporal dynamics and spatial patterns of drought and the relation to ENSO: a case study in Northwest China

ABSTRACTAn investigation of temporal dynamics and spatial patterns of dryness/wetness conditions over the eastern part of Northwest China (including Shaanxi, Ningxia, the eastern part of Gansu, and a part of southern Inner Mongolia) during the period 1960–2009 is presented. The analysis of this study is threefold. First, the dryness/wetness conditions over the study area were characterized using the self‐calibrating Palmer Drought Severity Index (PDSI). The spatiotemporal variability of dryness/wetness conditions in the study area was then investigated by the rotated empirical orthogonal function (REOF) and Mann–Kendall trend test. Third, we examined the periodical oscillations of dryness/wetness conditions and the multi‐scale relationships between dryness/wetness conditions and El Niño‐Southern Oscillation (ENSO). The results indicate that most parts of the study area were characterized by a dry trend in both the rainy season (May–September) and winter. Four sub‐regions of dryness/wetness conditions across the study area were identified. Based on the wavelet analysis, the periodical features in the PDSI time series for each sub‐region were explored. Negative relationships between the PDSI in the sub‐region I (representing the central and southern parts of Shaanxi and the southeastern Gansu) and the Niño 3.4 index can be consistently detected on 2–6 year scales during the entire period 1960–2009. This suggests that the strong El Niño events generally lead to very dry conditions in the sub‐region I on multi‐year scales. In addition, we further investigated how the ENSO cycle modulates the strength of the East Asian summer monsoon (EASM) in both developing and decaying phases of El Niño and La Niña events. The results of this study could be beneficial for efficient water resources management and drought assessment in the current study area and also provide a valuable reference for other areas with similar climatic characteristics.

Effective Resistance to Wheat Stripe Rust in a Region with High Disease Pressure.

Stripe rust is a major fungal disease of wheat. It frequently becomes epidemic in southeastern Gansu province, a stripe rust hot spot in China. Evaluations of wheat germplasm response are crucial for developing cultivars to control the disease. In total, 57 wheat cultivars and lines from Europe and other countries, comprising 36 cultivars with documented stripe rust resistance genes and 21 with unknown genes, were tested annually with multiple races of Puccinia striiformis f. sp. tritici in the field at Tianshui in Gansu province from 1993 to 2013. Seven wheat lines were highly resistant, with infection type (IT) 0 during the entire period; 16 were moderately resistant (IT 0;-2); and 26 were moderately susceptible (IT 0;-4), with low maximum disease severity compared with the susceptible control Huixianhong. 'Strampelli' and 'Libellula', with three and five quantitative trait loci, respectively, for stripe rust resistance have displayed durable resistance in this region for four decades. Ten cultivars, including 'Lantian 15', 'Lantian 26', and 'Lantian 31', with stripe rust resistance derived from European lines, were developed in our breeding program and have made a significant impact on controlling stripe rust in southeastern Gansu. Breeding resistant cultivars with multiple adult-plant resistance genes seems to be a promising strategy in wheat breeding for managing stripe rust in this region and other hot spots.

County-Scale Changes in Soil Organic Carbon of Croplands in Southeastern Gansu Province of China from the 1980s to the Mid-2000s

The Loess Plateau is an area of low crop productivity and one of the most susceptible areas for soil erosion in China. This study was designed to investigate changes in soil organic carbon (SOC) of croplands in four humid to semiarid counties (Huixian, Xifeng, Linxia, and Yuzhong) of Gansu province that have experienced accelerated grain production since the early 1980s. In 1979 to 1988 and 2006 to 2007, respectively, 2036 and 15,764 topsoil (20-cm) samples were collected and analyzed for SOC concentration and density from croplands covering 12 Chinese soil groups. By comparing the SOC data from the mid-2000s and the 1980s, we found that across the four counties, topsoil (20-cm) SOC concentration and density in croplands changed significantly (P < 0.01) at a rate of 0.04 ± 0.14 g kg–1 yr–1 or 0.01 ± 0.03 kg m–2 yr–1 from 7.9 ± 3.5 g kg–1 and 1.98 ± 0.9 kg m–2 in the 1980s to 8.7 ± 2.4 g kg–1 and 2.22 ± 0.5 kg m–2 in the mid-2000s, respectively. This overall increase in topsoil (20-cm) SOC concentration by 10% or density by 12% in the mid-2000s was associated with an increase of 83% in the stubble and root inputs to the soil across the four counties. There were large differences in the change size in the cropland topsoil (20-cm) SOC concentration and density among counties. In Huixian and Xifeng, both the topsoil SOC concentration and density in the mid-2000s were significantly higher than in the 1980s (P < 0.01), whereas there were no significant changes in topsoil SOC concentration and density in either Linxia or Yuzhong. Soils with lower initial SOC tended to increase more in SOC concentration than soils with higher initial SOC.

The Effect of Site Condition on Ground Motion in Gansu Province during the Wenchun Ms8.0 Earthquake

Based on mobile strong motion array observation, borehole exploration and site seismic response analysis, the site effects of mountainous topography in southeastern Gansu and the topography of loess tableland on ground motion were investigated in details. The analysis on acceleration records of aftershocks showed that the peak ground acceleration at top of the mountain is nearly 2 times of that at the foot of it. The seismic response analysis of sites shows that the loess tableland may amplify PGA by 1.44-2.0 times. Therefore, site effects of mountains and loess topography on ground motion should been taken account into seismic design.

Crustal Structure in Southeastern Gansu from Regional Seismic Waveform Inversion

AbstractThe 3‐component full‐waveform data from the August 1, 2008 aftershock of the Wenchuan earthquake recorded by 24 permanent broadband seismograph stations in southeast Gansu and adjacent areas were used to study the crustal velocity structure of southeast Gansu by the waveform inversion method which combines the niching genetic algorithm and reflectivity method. The western and eastern region of southeast Gansu belongs respectively to the Tibetan Plateau and the transition zone between Tibetan Plateau and Ordos block. The inversion result indicates that the upper and middle crusts of the two regions have very similar average P‐wave velocities and consist of acid and intermediate rocks. However, the lower crusts differ considerably in P‐wave velocity (6.41 km/s in the east and 6.96 km/s in the west) and thickness (9.3 km in the east and 19.8 km in the west). This indicates that the lower crust of the western region is composed of basic rock, while that of eastern region is intermediate rock, supporting the view that crustal thickening in the northeast margin of Tibetan Plateau occurs mainly in the lower crust. The P‐wave velocity at the top of upper mantle in the western region is 7.73 km/s, corresponding to that of a young, tectonically active area; while that in the eastern region is 8.05 km/s, corresponding to a stable ancient landmass. On the top of upper crust of the eastern region there is a sedimentary layer about 6.5 km thick and with a P‐wave velocity of 5.78 km/s, which is missing in the western region. Compared with the global average crust velocity of PREM, the overall crustal velocities of both regions are somehow low.

Late Quaternary landscape evolution in a small catchment on the Chinese Loess Plateau

Late Quaternary landscape evolution was analysed with reference to a small (0.08 km 2) drainage basin system in southeastern Gansu Province, southwestern Chinese Loess Plateau. In this region, V-shaped valleys with broad valley floors are prominent landscape features whose basic shape already existed prior to MIS 2. During MIS 2 the valley bottoms were infilled with fluvially reworked loess, today forming accumulation terraces. Infrared optically stimulated luminescence (IRSL) dating of these loess-like deposits assigned them to the time span ranging from 22.5 to 17.7 ka BP. During the late Holocene, valley fills were partly eroded, and the receiving stream channel was deepened by at least 25 m close to the confluence of the study site's channels. These alternating erosion and accumulation phases were triggered by climatic factors or human impact. In the most recent past, the high landscape sensitivity of the Chinese Loess Plateau has led to increasing soil conservation measures that have effectively confined surface erosion. However, the lack of drainage on the artificial terraces induces piping processes.

Wheat stripe rust in China

China has the largest stripe rust epidemic region in the world in terms of wheat acreage affected by the disease. Extensive studies on the epidemiology and management of stripe rust have been carried out since the widespread occurrence of the disease in the 1950s. Fifteen epidemic zones were classified, based on factors influencing the occurrence of wheat stripe rust. The disease can spread inter-regionally, mainly from west to east and from south to north. Winter-wheat growing regions in the north-west, south-west, and north, and spring-wheat growing regions in the north-west are the major epidemic areas. Hotspots of wheat stripe rust are mainly located in south-eastern Gansu and north-western Sichuan, and these areas constitute the inoculum base, centre of diversity, and major over-summering areas of the pathogen. Successful control in over-summering areas is the key to achieving sustainable management of stripe rust in China. Pathogen variability and race virulence have been monitored continuously, and the resistance genetics and background of Chinese wheat cultivars analysed. Effective management of stripe rust includes resistance breeding and application, diversification and deployment of various resistance genes, use of chemicals, adoption of appropriate agricultural practice, and integrated disease management in ‘hotspot’ regions. Collaboration of scientists among various organisations and disciplines is vital. We discuss the progress and challenges of wheat stripe rust management in China.