Photoprotective Role of Photosynthetic and Non-Photosynthetic Pigments in Phillyrea latifolia: Is Their “Antioxidant” Function Prominent in Leaves Exposed to Severe Summer Drought?

Carotenoids and phenylpropanoids play a dual role of limiting and countering photooxidative stress. We hypothesize that their “antioxidant” function is prominent in plants exposed to summer drought, when climatic conditions exacerbate the light stress. To test this, we conducted a field study on Phillyrea latifolia, a Mediterranean evergreen shrub, carrying out daily physiological and biochemical analyses in spring and summer. We also investigated the functional role of the major phenylpropanoids in different leaf tissues. Summer leaves underwent the most severe drought stress concomitantly with a reduction in radiation use efficiency upon being exposed to intense photooxidative stress, particularly during the central hours of the day. In parallel, a significant daily variation in both carotenoids and phenylpropanoids was observed. Our data suggest that the morning-to-midday increase in zeaxanthin derived from the hydroxylation of ß-carotene to sustain non-photochemical quenching and limit lipid peroxidation in thylakoid membranes. We observed substantial spring-to-summer and morning-to-midday increases in quercetin and luteolin derivatives, mostly in the leaf mesophyll. These findings highlight their importance as antioxidants, countering the drought-induced photooxidative stress. We concluded that seasonal and daily changes in photosynthetic and non-photosynthetic pigments may allow P. latifolia leaves to avoid irreversible photodamage and to cope successfully with the Mediterranean harsh climate.     

The Dune Lakes in central coastal California: Why are they dry?

The Dune Lakes comprise 10 natural lakes in the Callender Dunes in central coastal California, USA. These lakes are wetlands in an arid environment, being important habitat for native wildlife and plants, including three occurrences of the federally endangered/State threatened wetland plant, La Graciosa thistle (Cirsium scariosum var. loncholepis; Asteraceae). This plant is known from 21 occurrences, of which only five are extant in 2019. One extant occurrence persists at the lakes and where two other occurrences are likely extirpated. Nine lakes have recently dried, one having been dry for 5 years (2012–2017). Understanding the hydrology of the Dune Lakes is essential for conservation planning and to help prevent extinction of La Graciosa thistle. The best available information points to a combination of two primary causes for drying of the lakes. The first is extensive groundwater extraction beneath Nipomo Mesa to the east. The second is severe drought. The competing demands for water and continued development on the mesa will be obstacles to restoration of the lakes and to recovery of the endangered plant.     

末道次大压下率轧制工艺对提高微碳深冲板成品性能的研究

对微碳深冲板进行末道次大压下率轧制的新工艺试验研究以期提高其成品性能。试验结果表明：采用新工艺可显著细化热轧显微组织，并大大促进冷轧有利织构〈111〉的形成，从而大幅度提高冷轧成品的杯突值、应变硬化指数及塑性应变比。同时，由于采用新工艺而使变形速度提高，变形量加大，使得金属质点均匀流动而获得满意的板形。     

水旱灾害是主要的自然灾害

介绍中国水旱灾害系列专著之一的《黑龙江省水旱灾害》的主要内容。     

重庆市干旱灾害特征与影响因素及对策建议

采用重庆市1990~2016年旱情、气象、水利工程设施等数据,对重庆市综合旱情等级、旱情经验频率、降水量及距平分布、抗旱基础设施建设情况进行了深入的分析。结果表明:(1)重庆市在1990~2016年的27 a时间里,每年都有不同程度的旱情发生,多年区域平均农业旱情指数为0.54,为中度旱情,多年因旱饮水困难人数为213.73万人,为中度干旱,因旱饮水困难旱情等级、农业旱情等级整体呈逐年减弱的趋势;(2)不同旱情等级出现频率有所不同,轻度、中度、严重、特大干旱的发生频率分别为48.15%,44.45%,3.70%,3.70%,总体来看,重庆市的旱灾易发等级为轻度干旱;(3)造成干旱的原因有气象性、地域性、人为性等多种因素。为应对重庆市干旱灾害,提出主要对策建议:加快水生态文明建设步伐、加大水利工程设施建设、抓好水土保持工程建设、加强信息化工程建设。     

云南2009—2014年持续性气象水文干旱特征及成因分析

基于戴-帕尔默干旱强度指数(Dai Palmer drought severity index,Dai-PDSI)和径流干旱指数(streamflow drought index,SDI),分析云南地区2009—2014年持续性气象干旱与水文干旱时空演变特征,并利用NCAR/NCEP再分析资料,从西太平洋副热带高压、青藏高压、南支槽、对流层垂直运动及水汽垂直分布等视角,分析2009—2014年云南持续性干旱的原因。结果表明:(1)2009—2014年是云南地区自1961年以来最严重的一次持续性极端干旱过程,2009年10月—2010年9月是最干旱的时段;夏季与冬季是干旱最严重的两个季节。(2)在空间上,云南中东部旱情最重,东南部稍轻。(3)水文干旱伴随气象干旱而生,金沙江和南盘江出现重度水文干旱,澜沧江出现中等水文干旱,从强度上讲,水文干旱弱于气象干旱。(4)夏季西太平洋副热带高压偏西偏强,青藏高压持续偏强、中心偏西,云南上空的大气持续受它们控制,盛行下沉气流;冬季南支槽偏弱,不利于引导孟加拉湾水汽北上;在其他季节,大气多以下沉运动为主,对流层水汽严重不足。     

区域农业旱灾脆弱性评价及其影响因素

为加强区域农业旱灾风险管理,对河南、山东省农业旱灾脆弱性进行评价。结合相关文献与区域实际情况,从敏感性和恢复力2个角度选取12个指标,建立评价指标体系;运用熵值法和综合指数法构建旱灾脆弱性评价模型,计算区域内各城市的农业旱灾脆弱性指数;最后采用因子贡献度模型对关键影响因素进行识别。结果表明:研究区农业旱灾脆弱性级差化特征明显,总体处于中脆弱度状态;农业旱灾脆弱性空间差异显著,河南省脆弱性程度高于山东省;河南省农业旱灾脆弱性的主要影响因素有农业人口比重、复种指数和农村居民人均收入,山东省农业旱灾脆弱性的主要影响因素是有效灌溉面积比重、单位耕地面积农业用水量和人均财政收入。     

气候变化对滇中引水工程取水影响分析

气候变化正在逐渐改变全球的水循环现状,并对水文水资源及其应用产生重大影响。在联合国政府间气候变化专门委员会(IPCC)对气候变化趋势进行分析的基础上,优选近期、远期气候变化情景,并模拟在未来气候变化情景下金沙江流域干流主要断面的逐日流量过程,用以分析气候变化对金沙江干流石鼓断面水文干旱以及对滇中引水工程取水的影响。研究结果表明:受未来可能的气候变化影响,金沙江干流石鼓断面的水文干旱发生强度和发生频率都将有所增加,远期较近期具有高的不确定性;滇中引水工程不可取水天数和可调水量将会增加,但总体而言对工程的不利影响较小。     

标准化径流指数在阿克苏河水文干旱特征识别中的应用

阿克苏河位于丝绸之路经济带重要通道,是典型的中亚跨境河流,阿克苏丰富的水资源成为沿岸各国争夺的焦点。针对阿克苏河未来水资源评估和管理的迫切需要,以阿克苏河干流月径流为数据基础,结合径流距平百分比,采用标准化径流指数(Standardized Runoff Index,SRI)辨识阿克苏河水文干旱事件,并验证了水文干旱识别的合理性。结果表明:SRI丰枯等级划分临界值在阿克苏河能够有效地识别水文干旱事件及其干旱等级,SRI趋势分析发现未来阿克苏河春、夏季洪水和冬旱现象的可能性在逐渐增大,水资源季节差异将越来越明显,这将是未来水资源合理利用和管理的一个新挑战。