Source Inition Pattern and Coupling Mechanism of Granular Deposit and Seepage in Steep Longitudinal Gully,Wenchuan

Generally, collapse and landslide are the main sources of granular deposits while the initiation of deposits is triggered by the tremendous runoff from steep longitudinal gully. Substance composition, topographic condition and catchment characteristics directly affect the models of deposits initiation, and larger longitudinal grade provides better topographic condition for the initiation. Several sets of experiments on model casing were designed to simulate the failure mode of slopes under the states of stable and unstable seepages according to catchment and penetration characteristics. It was revealed from the experiments that the initiation of granular deposits had two fundamental modes, that is, fire hose effect and static liquefaction. The former one generally happens at the unsaturated slope or the slope of high permeability while the latter case occurs at the soils containing fine particles. It was concluded that the fire hose effect could generate the deep and narrow eroded channel along with the runoff, the movement distance was related to the continuous hydrodynamic force, and the transporting capacity of solid substances was weak. In addition, slope fluidization was featured with slow seepage failure at the early stage, instantaneous shear failure at the late stage, and wider channel came out due to serious erosion.     

Effects of Simulated Diurnal Asymmetrical Warming on the Growth Characteristics and Grain Yield of Winter Highland Barley in Tibet

There has been an obvious diurnal asymmetrical warming effect as a result of the overall climate warming in the Tibetan Plateau. To reduce the uncertainty caused by the diurnal asymmetrical warming effect on future food security predictions in the Tibetan Plateau, this study used winter highland barley (var. Dongqing No. 1) for the experimental materials, and the FATI (Free Air Temperature Increase) field open heating system to carry out a simulated diurnal asymmetrical warming experiment (AW: All-day warming, DW: Daytime warming, NW: Nighttime warming, CK: Control) for two growing seasons (2018-2019 and 2019-2020) at the Lhasa Agroecosystem Research Station. The growth characteristics and yield of Tibetan winter highland barley were investigated in this study. Compared to the control, all the AW, DW and NW treatments had significant effects on the phenological period of winter highland barley, with the advancement of the phenological phase and shortening of the whole growth period. The degree of influence was AW>NW>DW, and all the AW, DW and NW treatments shortened the interval from sowing to heading of winter highland barley and increased the interval from heading to maturity. The effect on the phenological phase was the most obvious for AW and reached a statistically significant level (P<0.05). During the generative growth phase, the biomass above-ground and plant height of winter highland barley had an increasing tendency under the different warming conditions. In the late growth period, the biomass above-ground and plant height of the NW treatment were significantly higher than those of the other treatments. In addition, the warming caused a decrease in the dry matter distribution proportions of leaves and stems at the mature stage, and an increase in the distribution ratios of roots and spikes; and the AW, NW and DW treatments increased grain yields by 16.4%, 24.6% and 9.5%, respectively, on average in the two years. The increasing effect on grain yields of the NW treatment reached a significant level compared with the control in 2019-2020 (t=-2.541, P=0.026). In terms of yield composition, the effective spike number and 1000-grain weight tended to increase. The grain number per spike tended to increase, except for the AW treatment, while panicle length and seed setting rate tended to decrease, except for the NW treatment. Therefore, the effects of different simulated diurnal asymmetrical warming treatments on the growth characteristics and yield of winter highland barley were variable in the Tibetan Plateau.     

黄土丘陵沟壑区现代沟道农业及其可持续发展

现代沟道农业是黄土丘陵沟壑区人地耦合发展形成的一种新兴农业地域类型,其可持续发展对于区域农业高质量发展、“三生”空间优化和乡村振兴具有重大现实意义。从人地系统科学认知出发,对现代沟道农业的内涵、可持续发展方向、典型发展模式和保障体系进行了探讨,并进行了相关研究展望,为系统认识黄土丘陵沟壑区沟道农业模式,推进农业可持续发展提供了理论参考。主要结论：(1)沟道农业是乡村地域系统的重要功能类型,具有多尺度、多层次的特点,其可持续发展应从微观、中观和宏观3个层面,协同解决土壤生态系统、农田生态系统和农业地域系统的可持续发展问题。(2)保障粮食安全和生态安全,积极推进农业结构调整,发展多功能农业,通过“3C”模式,即农业自身内循环、农业外循环、基于农业多功能的农业大循环,实现生产结构优化、产业链条延伸和城乡功能互补。(3)创新推广土地综合整治带动模式、农业结构调整带动模式、特色资源综合开发模式和土地流转规模生产模式,有助于农业提质增效和农业高质量发展。(4)拓展地理学与其他学科的交叉研究,深化“理论-实践”贯通式研究,探索建立涵盖技术研发与应用、人才培养、政策制度支撑等内容于一体的农业生产保障体...     

黄土丘陵沟壑区生态系统服务对人类福祉的影响及其群体差异

生态系统服务对人类福祉的影响研究对于分析区域生态系统的社会贡献及有效减贫等方面具有重要的理论与实践意义。本文以地处黄土丘陵沟壑区的陕西省米脂县为例,在整合主客观人类福祉的基础上,基于生态系统服务可得性评估,利用结构方程模型定量分析了生态系统服务对人类福祉的影响及其群体差异。结果如下：① 生态系统服务对客观福祉和主观福祉具有显著正向影响,并通过客观福祉对主观福祉产生间接影响。农户属性对生态系统服务和客观福祉直接效应显著,对主观福祉直接效应不显著。② 生态系统服务对人类福祉的影响存在群体差异,纯农型与兼业型的服务可得性对客观福祉直接效应显著,而非农型不显著;纯农型与兼业型的服务可得性对主观福祉的直接效应明显大于非农型,且非农型间接效应不显著;非农型客观福祉对主观福祉的影响明显高于纯农型与兼业型。③ 生态系统服务对人类福祉影响的因子贡献与服务组合存在群体差异,即三类群体生态系统服务对福祉影响的差异不仅体现在服务类型及影响程度上,还体现在服务组合的差异上。     

黄土丘陵沟壑区村域生态系统服务簇的时空分异及其地形梯度分析

探究村域生态系统服务簇对于厘清黄土丘陵沟壑区农业生态系统复杂特征、从多重服务供给角度提高服务的福祉贡献具有重要意义。论文以黄土丘陵沟壑区米脂县为例,基于高斯混合模型识别2009年和2019年村域生态系统服务簇并分析其时空分布,同时,结合地形分布指数探究服务簇在地形梯度上的分布模式。结果如下： ① 各类服务空间分异明显,且服务之间空间分布差异较大;近10 a间各类服务水平均有不同程度提高,其中调节服务有较大改善,而食物供给与文化服务增幅较小;各类服务空间变化格局存在较大差异,这与土地利用的空间演变关系密切。② 利用高斯混合模型识别4类服务簇,包括农业生产簇、农业美学簇、生态保育簇与城镇休闲簇;各类服务簇空间分异明显,且研究期间存在明显数量和空间转移变化;农业美学簇与生态保育簇是当地主导服务簇,且主导性增强,而农业生产簇与城镇休闲簇比重下降。③ 地形起伏度与服务簇的空间关联密切。随起伏度上升,农业生产簇与农业美学簇呈倒U型,生态保育簇优势分布增加,城镇休闲簇优势分布减弱;研究期间农业生产簇与城镇休闲簇向低起伏度的转移趋势明显,而农业美学簇与生态保育簇趋向于向高起伏度转移。     

ASYMMETRICAL STRUCTURES OF THE TEMPERATURE AND HUMIDITY OF TROPICAL CYCLONES

Based on NCEP/CFSR 0.5° reanalysis data and the best track data from the Japan Tokyo Typhoon Center,composite and comparative analyses demonstrate the asymmetrical structures of the temperature and humidity in tropical cyclones over the Western North Pacific and the South China Sea from 1979 to 2010.The results are shown as follows.(1) With intensifying tropical cyclones,the flow field tends to become gradually more axisymmetric;however,the asymmetry of the specific humidity in the outer regions is more obvious.(2) In general,tropical cyclones have a non-uniform,vertical, "double warm-core" structure.The "warm-cores" in the lower level of weak tropical cyclones and in the higher level of strong tropical cyclones are the stronger of the two.(3) The distribution area of a "warm-core" is enhanced with cyclone intensification and tends to become more axisymmetric.At 200 hPa,the "warm-core" of a weak cyclone has a weak anticyclone in the center,whereas that of a strong cyclone has a weak cyclone in the center.(4)The "wet-core" of a tropical cyclone is primarily located in the lower level(700-850 hPa).With the cyclone's intensification,the intensity of the "wet-core" increases and the scope of the 0.8 g kg~(-1) specific humidity anomaly tends to expand to higher levels.(5) With the cyclone's deepening,the pseudo-equivalent potential temperature at different levels in different regions increases.In addition,the largest warming rates at each intensity level in the different regions occur in the core area,followed in turn by the envelope and outer areas.     

Factors controlling the morphology and volume (V)–length (L) relations of permanent gullies in the northern Ethiopian Highlands

Small‐scale aerial photographs and high‐resolution satellite images, available for Ethiopia since the second half of the twentieth century as for most countries, allow only the length of gullies to be determined. Understanding the development of gully volumes therefore requires that empirical relations between gully volume (V) and length (L) are established in the field. So far, such V–L relations have been proposed for a limited number of gullies/environments and were especially developed for ephemeral gullies. In this study, V–L relations were established for permanent gullies in northern Ethiopia, having a total length of 152 km. In order to take the regional variability in environmental characteristics into account, factors that control gully cross‐sectional morphology were studied from 811 cross‐sections. This indicated that the lithology and the presence of check dams or low‐active channels were the most important controls of gully cross‐sectional shape and size. Cross‐sectional size could be fairly well predicted by their drainage area. The V–L relation for the complete dataset was V = 0 · 562 L ^1·381 (n = 33, r² = 0 · 94, with 34 · 9% of the network having check dams and/or being low‐active). Producing such relations for the different lithologies and percentages of the gully network having check dams and/or being low‐active allows historical gully development from historical remote sensing data to be assessed. In addition, gully volume was also related to its catchments area (A) and catchment slope gradient (S_c). This study demonstrates that V–L and V–A × S_c relations can be very suitable for planners to assess gully volume, but that the establishment of such relations is necessarily region‐specific. Copyright © 2013 John Wiley & Sons, Ltd.     

都江堰市龙池镇麻柳沟泥石流特征及形成条件分析

通过对都江堰市龙池镇麻柳沟泥石流灾害现场调查,分析了泥石流的特征及形成条件,并对沟道内松散固体物质储量进行了计算,分析了危险区范围。结果表明:麻柳沟流域的地形特征为泥石流形成提供了有利的地形条件,"5.12"汶川地震和"4.20"芦山地震为泥石流的形成提供了丰富的物源条件,多次强降雨为泥石流的启动提供了充足的水源条件。通过计算得出,麻柳沟沟道内的松散固体物质储量约为29.21×104 m3,其中形成区13.19×104 m3,流通区3.27×104 m3,堆积区12.75×104 m3,泥石流最大危险范围为0.247 1km2。     

基于GIS纸坊沟小流域土壤侵蚀强度空间分布

给出水蚀预报模型各因子计算方法,利用GIS空间数据提取和运算,结合水力侵蚀强度分级,获取流域土壤侵蚀强度空间分布特征.结果表明,流域实际土壤侵蚀强度分布特征是流域沟头侵蚀面积大,侵蚀强度高于沟口,且极易发生极强烈和剧烈侵蚀;流域中部以轻度和中度侵蚀为主,同时左岸侵蚀强度明显强于右岸.流域强烈侵蚀区位于苦荞沟、拐沟、大范家沟、大罗锅沟、正沟,年均侵蚀模数23 000～33 000 L/(km2·a);浅沟侵蚀是造成沟间地剧烈土壤侵蚀发生的主要原因,流域土壤侵蚀强度空间分布受地面植被覆盖和坡度制约.     

黄土丘陵小流域生态用水试验研究——气候和土地利用变化的影响

为探讨黄土高原地区的生态恢复,以半干旱黄土丘陵区安家沟小流域的气象、土壤水分、地形图和土地利用图(1982年和2002年)为源信息,分析了不同植被类型的蒸散量和生态用水量、流域生态用水量及其与气候和土地利用变化的关系。研究结果表明:(1)流域土地利用结构从1982-2002年间变化较大,农地(特别是梯田)增加较快,乔木林地急剧减少,主要表现为毁林、开荒和造田;(2)研究区内各种植被/土地利用类型的蒸散量和生态用水都极大地受控于气候(特别是降雨量)的影响,其年际差异较大;(3)不同植被/土地利用类型间的蒸散量和生态用水差异明显,在各个年份乔灌林的生态用水量均大于农作物和自然草地的蒸散量和生态用水量,但生态用水的差异程度小于蒸散量的差异程度;(4)以自然草地(即荒草地)为标准,农作物的蒸散量和自然草地接近,但乔灌林地的蒸散量和生态用水量均远高于自然草地,难于实现土壤水分平衡;(5)流域土地利用结构的变化(主要是强耗水植被的减少)减小了流域生态用水量,增强了流域的水分平衡能力。