Base cation concentrations in forest litter and topsoil have different responses to climate and tree species along elevational gradients

The forest litter is an essential reservoir of nutrients in forests, supplying a large part of absorbable base cations(BC) to topsoil, and facilitating plant growth within litter-soil system. To characterize elevational patterns of base cation concentrations in the forest litter and topsoil, and explore the effects of climate and tree species, we measured microclimate and collected the forest litter and topsoil(0-10 cm) samples across an elevational range of more than 2000 m(1243 ～ 3316 m a.s.l.),and analyzed the concentrations of BC in laboratory. Results showed that: 1) litter Ca concentration displayed a hump-shaped pattern along the elevational gradients, but litter K and Mg showed saddle-shaped patterns. Soil Ca concentration increased with elevation, while soil K and Mg had no significant changes. 2) Ca concentration in the forest litter under aspen(Populus davidiana) was significantly higher than that in all other species, but in topsoil, Ca concentration was higher under coniferous larch and fir(Larix chinensis and Abies fargesii). Litter K and Mg concentrations was higher under coniferous larch and fir, whereas there were nosignificant differences among tree species in the concentrations of K and Mg in topsoil. 3) Climatic factors including mean annual temperature(MAT), growing season precipitation(GSP) and non-growing season precipitation(NGSP) determined BC concentrations in the forest litter and topsoil. Soil C/N and C/P also influenced BC cycling between litter and soil. Observation along elevations within different tree species implies that above-ground tree species can redistribute below-ground cations, and this process is profoundly impacted by climate. Litter and soil Ca, K and Mg with different responses to environmental variables depend on their soluble capacity and mobile ability.     

Compression characteristics of saturated re-compacted glacial tills in Tianmo Gully of Tibet,China

Glacial tills are highly compressible soils composed of loosely cemented sandy silt particles. Their role, for instance, as initial filler materials in geo-technical projects along temperate glacier regions warrant a systematic evaluation of their compressive characteristics. As such, we carry out a series of onedimensional compression tests on re-compacted glacial till samples obtained from Tianmo Gully, Tibet, with the aims of evaluating their compressive behavior under controlled initial stress conditions. The yield stress was determined from the void ratio versus consolidation pressure(e-log) planes. Its compression and swelling behaviors were observed during the primary and secondary compressions of the consolidation tests. From the compression curves, a correlation can be found between the consolidation stress and the void index. In addition, we find that the compression curves of glacial tills collapse into a single curve when normalized by the compression index. The experimental results in this study provide a basic understanding of the compression characteristics of the glacial tills in Tibet, China.     

鄂尔多斯盆地西缘羊虎沟组物源区分析

鄂尔多斯盆地西缘羊虎沟组物源特征对天然气勘探尤为重要。通过砂岩的碎屑组分、岩屑组分、重矿物组合以及石英阴极发光等研究,认为研究区羊虎沟组受到北部、西南部、南部物源控制,各个方位物源在研究区中部吴忠—马家滩地区汇合。通过砂岩轻、重矿物组合和碎屑组分的Dickinson三角图解,以及泥岩的稀土元素特征等分析,认为研究区羊虎沟组源岩以大陆上地壳岩石为主。研究区北部砂岩物源区为再旋回造山带物源区,泥岩球粒陨石标准化稀土元素配分模式与阿拉善古陆浅变质岩相似,具有亲缘性;西南部及南部砂岩物源区为稳定陆块区和再旋回造山带物源区,泥岩球粒陨石标准化稀土元素配分模式与祁连—北秦岭造山带中浅变质岩相似。综上所述,研究区北部母岩主要为阿拉善古陆的浅变质岩夹少许火山岩,西南部及南部母岩主要为祁连—北秦岭造山带的中浅变质岩,其次为碳酸盐岩和火山岩。     

关于确保甘肃省祁连山生态保护红线落地并严守的科技支撑建议

祁连山是中国西部重要生态安全屏障,是国家重点生态功能区,其生态保护与治理一直受到国家、地方政府和当地居民高度关注。目前,在祁连山的生态保护工作中,缺乏对现状基础数据的全面掌握,区域经济发展与生态环境保护矛盾突出,生态环境综合监测系统不完备,生态补偿机制推进实施缺乏创新。在全面梳理祁连山目前存在的重大生态问题的基础上,提出了祁连山生态保护红线落地并严守的建议,包括加快开展祁连山综合科学考察、完善并落实开展生态补偿机制、探索以正面清单为导向的协调发展模式、促进生态安全与地方经济社会可持续发展相协调、进一步实施重大配套政策、完善保障支撑体系等。     

关于新时期中国西部发展沙产业的思考

沙产业是中国西部开发、生态文明建设和脱贫致富的必然选择。在对新时期沙产业内涵理解的基础上,对中国西部发展沙产业的空间基础、资源基础和科技基础进行了潜力分析,通过案例分析了新时期沙产业发展与生态文明建设和精准扶贫的关系。指出了目前中国西部沙产业发展中存在的主要问题,并提出了中国西部沙产业发展的政策建议。     

张掖盆地地下水硝酸盐污染与人体健康风险评价

地下水是张掖盆地的重要水资源,其硝酸盐污染尚未得到足够重视。对张掖盆地2004、2015年地下水硝酸盐浓度进行了系统分析,并采用美国环境保护署（USEPA）推荐的健康风险评价模型评估了地下水硝酸盐的健康风险。结果表明：自2004年以来张掖盆地地下水硝酸盐污染日趋严重。2015年硝酸盐浓度最高已达到283.32 mg·L^-1,17.61%的采样点硝酸盐氮浓度超过GB5749-2006《生活饮用水卫生标准》中饮用地下水限量值（20 mg·L^-1）。研究区人群经皮肤接触途径摄入硝酸盐的健康风险在可接受水平,而饮水摄入硝酸盐的健康风险较高,总风险中饮水途径引起健康风险的贡献率占99.40%,远大于皮肤接触途径。儿童经饮水摄入和皮肤接触两种途径的健康风险均显著高于成人,分别为成人的1.544倍和1.039倍。32.39%的采样点地下水硝酸盐对儿童的健康风险超出了可接受水平,14.79%的采样点地下水硝酸盐对成人的健康风险不可接受。甘州区城区、临泽县北部边缘及高台县城区周围硝酸盐浓度最高,这些区域内所有人群都面临硝酸盐引发的高健康风险,其余区域硝酸盐引发的健康风险相对较低。     

毛乌素沙区1961-2016年降水特征

基于毛乌素沙区10个气象站1961-2016年观测资料,应用Mann-Kendall方法和t检验法对各气象站年降水量进行了突变检验,借助小波分析讨论了各气象站年降水量的周期特征,根据降水量等值线划分结果对整个研究区分区分析了年、季、月和日尺度上的降水变化特征,并在两个时段上分析了季节性降水的差异。结果表明：毛乌素沙区年降水量空间特征差异明显,东部亚区呈上升趋势,中西部亚区呈下降趋势,但变化趋势不显著且无突变发生;降水年内分配不均,干湿季分明,降水集中在5-9月,夏秋季降水占全年降水比重大,季、月和日尺度降水量存在梯度递减变化;年降水量的年际变化过程存在多重时间尺度的自相似结构;近26年的冬春季降水增加显著,但降水波动幅度小于前30年。     

大亚湾西部海域沉积物中生物硅的含量及其分布特征

采用2. 0 mol/dm~3Na_2CO_3溶液5h单点化学提取-硅钼蓝连续分光光度分析法分别测定了大亚湾西部海域13个表层沉积物和1个沉积物岩芯中生物硅的含量.表层沉积物和沉积物岩芯中生物硅含量占比分别为0. 69%～2. 02%和1. 24%～2. 05%,平均值分别为1. 42%和1. 60%.结果证实西大亚湾沉积物中生物硅含量水平与我国南海近岸海域基本一致.在210Pbex测年的基础上,通过分析沉积物岩芯中生物硅、有机物、无机碳等多指标,揭示近百年来大亚湾周边环境变化对海洋环境的影响,证实了上世纪80年代以来西大亚湾周边农业、海水养殖业和工业发展等人类活动加剧了该海域生态环境变化,尤其90年代核电站运行对海洋生态变化造成一定的影响.     

柔肝通络汤治疗脑梗死急性期40例临床观察

目的：观察柔肝通络汤治疗脑梗死急性期（阴虚络瘀证）的临床疗效。方法：将脑梗死急性期（阴虚络瘀证）患者80例,随机分为2组,每组各40例。治疗组采用柔肝通络汤治疗,对照组采用西医常规治疗。结果：综合疗效总有效率治疗组为87.5%,对照组为72.5%,组间比较,差异有统计学意义（P＜0.05）;中医证候疗效总有效率治疗组为90.0%,对照组为75.0%,组间比较,差异有统计学意义（P＜0.05）;2组血液流变学指标、NIHSS评分治疗前后组内比较及治疗后组间比较,差异均有统计学意义（P＜0.01）。结论：柔肝通络汤治疗脑梗死急性期（阴虚络瘀证）有较好疗效,优于西医常规治疗。     

龙胆祛湿汤加减联合海棠丁香凝胶治疗亚急性湿疹36例

目的：观察龙胆祛湿汤加减联合海棠丁香凝胶治疗亚急性湿疹（湿热蕴肤型）的临床疗效。方法：将76例亚急性湿疹（湿热蕴肤型）患者随机分为治疗组36例与对照组40例。治疗组采用龙胆祛湿汤加减联合海棠丁香凝胶治疗,对照组采用盐酸左西替利嗪治疗。观察2组治疗前后症状体征评分,评定临床疗效。结果：总有效率治疗组为97.22%,对照组为82.50%,组间比较,差异有统计学意义（P<0.05）。结论：龙胆祛湿汤加减联合海棠丁香凝胶治疗亚急性湿疹（湿热蕴肤型）的临床疗效优于盐酸左西替利嗪治疗,值得临床推广应用。