Hu Xin, Hong Baoning, Du Qiang, et al. Influence of water contents on shear strength of coal-bearing soil[J]. Rock and Soil Mechanics, 2009, 38(8): 2291－2294. (in Chinese with English abstract)[30]

土的抗剪强度是工程设计中重要的依据指标,同时也是土壤精准耕作,大型农业器具设计的一个基本参数。紫色水稻土长期处于淹水状态,为研究其抗剪强度的水敏感性特征,该文以重庆市合川区钱塘镇大柱村国土整治项目区内紫色水稻土为试样,采用调控含水率变化,通过三轴不固结不排水试验研究其抗剪强度的水敏感性特征,并为实际工程中处理紫色水稻土提出建议。结果表明：1）同一围压下,紫色水稻土的最大主应力差随着含水率的增加而减小;相同含水率下,随着围压的升高最大主应力差增加,但这种增加趋势随土壤含水率的增加而减小。2）当含水率处于界限含水率附近时,抗剪强度随含水率的增减变化较为缓慢;含水率大于某一值后紫色水稻土抗剪强度随含水率增加而减小。3）紫色水稻土的粘聚力随含水率的变化具有明显的峰值,呈先增大后减小的趋势。4）紫色水稻土内摩擦角与含水率之间具有明显的线性负相关性。该研究可为地区农业基础工程的设计到施工,以及工后更好地控制路基路堑的稳定性等提供参考。     

汶川地震重灾区土壤侵蚀敏感性评价

以通用土壤流失方程为基础,选择降雨侵蚀力、土壤可蚀性、地形起伏度、植被覆盖自然因子作为土壤侵蚀敏感性的评价指标,根据汶川地震重灾区自然环境特征,制定评价指标的分级标准,在GIS技术支持下生成单因子敏感性评价图,在此基础上基于ArcGIS的空间叠加分析功能,完成单因子的叠加运算,从而实现土壤侵蚀敏感性综合评价。结果表明:研究区土壤侵蚀敏感性以高度敏感和中度敏感为主,轻度敏感次之,不敏感和极敏感所占比例较小。空间上土壤侵蚀敏感性呈块状不连续分布,但侵蚀敏感性区域又相对集中,分布特征与地貌类型关系较大。针对不同的土壤侵蚀敏感等级,提出了相应的水土保持对策。     

SWAT模型在黄土丘陵区参数敏感度分析及率正研究

SWAT模型是基于水文过程的、具有很强物理机制的流域分布式水文模型。应用SWAT模型,结合1986—2000年罗玉沟流域实测水文资料对径流进行模拟,并进行了模型参数敏感度分析和率正。通过敏感度分析,辨析出影响该流域产流模拟结果精度的主要参数因子,如径流曲线数CN2等。依据上述结论调整参数值,对模型进行了率正和验证,得出率正期的相对误差为14.0%,R²为96.1%,Nash—Suttcliffe系数为0.89;验证期的相对误差为8.8%,R²为91.5%,Nash—Suttcliffe系数为0.82。结果表明实测流量和模拟流量的线性回归系数和模型的效率系数满足模型模拟的要求,SWAT模型适用于该研究区域。     

基于GIS的仁怀市生态敏感性评价

区域生态敏感性评价对于制定区域社会经济发展政策,有效进行环境管理具有重要作用.利用GIS技术,以贵州省仁怀市为研究对象,运用单因子敏感性评价和综合敏感性评价两种方法,选择土地利用、高程、坡度、水系、地质灾害作为评价因子,对仁怀市生态敏感性及其空间分布进行了研究.结果表明:极敏感区占仁怀市总面积的1.43％,主要分布在高海拔山区;敏感区占17.76％,分布在沿河地区以及山麓地区;低敏感区占57.41％,分布在中低山地区;不敏感区占23.40％,主要分布在城镇区域.结合生态敏感性,提出了各区块的生态环境建设和保护对策,以期为仁怀市区域生态环境保护提供决策依据.     

气候变化对黄河中上游地区潜在蒸散影响的估算

采用Penman—Monteith公式计算潜在蒸散,分析1961-2010年黄河中上游地区气候因子的变化趋势,并用偏微分方法定量分析各气候因子变化对潜在蒸散的影响。结果显示：1）近50年来黄河中上游地区气温显著升高（α〈0．01）,风速和日照时间显著减少（α〈0．01）。半干旱区面积不断扩大,气候总体呈暖干变化趋势。2）潜在蒸散对实际水汽压变化最敏感,其次为最高气温、风速和日照时间,对最低气温变化最不敏感。夏季潜在蒸散对日最高气温最敏感,其他季节对实际水汽压最敏感。3）风速对年潜在蒸散变化贡献最大,其次为气温和日照时间,实际水汽压贡献最小。春夏秋冬对潜在蒸散变化贡献最大的气候因子依次为风速、日照时间、气温。温度升高、湿度减少埘潜在蒸散的正影响已被风速、辐射下降的负影响所抵消。综合考虑各气候因子对潜在蒸散的作用有助于加深对气候变化影响机制的认识,并为气候变化适应对策研究提供科学依据。     

根系吸水模型模拟覆膜旱作水稻气孔导度

为构建覆膜旱作水稻根系吸水模型,进一步改进气孔导度模型,该文在湖北十堰开展包含3个水分处理(淹水、覆膜湿润和覆膜旱作栽培)的田间试验,分析覆膜旱作水稻蒸腾(根系吸水)与根长之间的关系,在此基础上建立覆膜旱作水稻根系吸水模型,并将其代替彭曼(Penman-Monteith,PM)方程来估算蒸腾强度,进而与脱落酸(abscisic acid,ABA)参与调控的气孔导度模型耦合,模拟覆膜旱作条件下水稻气孔导度的日变化过程。结果表明,水稻蒸腾与根长呈线性正比关系(R~2=0.96,P0.05),据此建立的根系吸水模型可以较好地模拟覆膜旱作水稻的蒸腾(根系吸水)规律,使蒸腾强度模拟值和实测值间的相对误差基本控制在15%以内;经改进后的Tardieu-Davies气孔导度模型(TD模型)可有效描述不同土层根系吸水流中的ABA浓度及不同根系层ABA的合成对木质部蒸腾流中总ABA含量的贡献,可较好地模拟气孔导度的日变化过程。改进TD模型大大提高了模拟精度,使相对误差不超过7.0%。该研究可为覆膜旱作水稻生理节水机理和水分利用效率评估提供一定的理论依据。     

基于GIS的慈溪市土壤侵蚀敏感性评价

[目的]对影响浙江省慈溪市土壤侵蚀敏感性的各因素进行评价,为该市进行环境功能区划和各项水土保持措施工程的布局调整提供参考。[方法]借鉴土壤侵蚀流失USLE模型,选取降雨侵蚀力、土壤质地、植被覆盖和地形起伏度4因子构建土壤侵蚀敏感性评价体系,并运用GIS进行土壤侵蚀敏感性分析。[结果]慈溪市土壤侵蚀敏感性在空间格局上呈半圆环状结构分布,并且轻度敏感区面积为733.05km2,占比高达75.70%,广泛分布于平原乡镇地区;不敏感区主要分布于近海滩涂区域,极敏感、高度敏感及中度敏感区则位于南部的丘陵、山地地区。[结论]慈溪市土壤侵蚀敏感性评价结果与水土流失现状空间分布走势大致相符,为此应重视和预防水土保持工作。     

渠道边坡稳定的盐敏感性特征研究

工程中灌排渠道在运行多年后,随着土中含盐量的增加,会造成渠道边坡不同程度的滑塌、变形及结构的破坏。通过对盐化土的剪切试验和界限含水率试验,得到不同含盐量下土的抗剪强度指标和稠度界限,运用单因素试验分析含盐量对土的抗剪强度和稠度界限的影响规律。随着含盐量的增加,土体的团聚体稳定性降低,增加了粘粒的分散性,土的抗剪强度有所下降;同时土的稠度界限也会降低,增大了土的流动性,明确地说明含盐量增加也是影响灌排渠道边坡稳定性重要因素。     

Effect of ABA,arginine and sucrose on protein content of date palm somatic embryos

Abscisic acid (ABA), arginine and sucrose were evaluated for their effects on the morphology, germination rates and protein content of date palm somatic embryos (SE). Different concentrations of these supplements in the culture medium were used. The comparative study of SE length and thickness between treated and untreated SE revealed no differences, except for ABA (20 μM), which increased thickness. A decrease of water content (WC) in favor of an increase in dry weight (DW) was observed in all treated SE, especially with sucrose (90 g l⁻¹) and ABA (20 μM). Only ABA (20 and 4 μM) caused a proliferation rate of the cultures higher than those in the control. Although all the tested compounds increased protein content, ABA (20 μM) was more effective in protein enrichment than arginine and sucrose treatments. The SDS-PAGE protein profiles showed a significant difference between treated and untreated SE. A protein band of 22 kDa, identified as glutelin in a previous work, was accumulated after treatment with 20 μM ABA or 3 mM arginine. These findings may contribute to further understanding of the mechanisms involved in the accumulation of specific storage proteins in several plants.     

Does root-sourced ABA play a role for regulation of stomata under drought in quinoa (Chenopodium quinoa Willd.)

The Andean seed crop quinoa (Chenopodium quinoa Willd.) is traditionally grown under drought and other adverse conditions that constrain crop production in the Andes, and it is regarded as having considerable tolerance to soil drying. The objective of this research was to study how chemical and hydraulic signalling from the root system controlled gas exchange in a drying soil in quinoa. It was observed that during soil drying, relative g_s and photosynthesis A_max (drought stressed/fully watered plants) equalled 1, until the fraction of transpirable soil water (FTSW) decreased to 0.82 ± 0.152 and 0.33 ± 0.061, respectively, at bud formation, indicating that photosynthesis was maintained after stomata closure. The relationship between relative g_s and relative A_max at bud formation was represented by a logarithmic function (r² = 0.79), which resulted in a photosynthetic water use efficiency WUE_Amax_/gs$\text{WU}{\text{E}}_{A_{\text{max}}/g_{\text{s}}}$ of 1 when FTSW > 0.8, and increased by 50% with soil drying to FTSW 0.7–0.4. Mild soil drying slightly increased ABA in the xylem. It is concluded that during soil drying, quinoa plants have a sensitive stomatal closure, by which the plants are able to maintain leaf water potential (ψ_l) and A_max, resulting in an increase of WUE. Root originated ABA plays a role in stomata performance during soil drying. ABA regulation seems to be one of the mechanisms utilised by quinoa when facing drought inducing decrease of turgor of stomata guard cells.