敦煌市棉田烟粉虱发生规律的研究

2006年4月~2006年9月,对敦煌市棉田烟粉虱的生物型进行了鉴定并对其发生规律进行了研究.结果表明:敦煌市棉田烟粉虱为B型烟粉虱.烟粉虱5月初开始从温室向棉田扩散,6月下旬在棉田内开始普遍发生,8月上旬形成第1个成虫高峰,至9月中下旬随棉花采摘和气温的下降田间成虫数量逐渐减少,卵、若虫的种群动态与成虫基本一致.烟粉虱从温室迁入棉田,其扩散距离越远,数量越少;距离温室越近的棉田烟粉虱发生数量越多,距离温室大棚10 m处的棉田的种群数量显著高于50 m处的棉田.     

库姆塔格沙漠东南部胡杨液流变化及其对环境因子的响应

于2018年4月?10月(春季4月、夏季7月、秋季9月)利用PS-TDP8树木茎流监测系统对库姆塔格沙漠东南部胡杨(Populus euphratica)的液流速率变化进行监测,采用相关分析及逐步回归法分析气象因子(太阳总辐射、空气温度、风速、空气相对湿度)对胡杨液流的影响。结果表明:胡杨茎干液流日变化趋势呈几字“宽峰型”;夏季液流的启动时间最早,液流启动在06:00,秋季液流启动时间最晚,不同季节夜间存在较高液流(10.994~26.035 cm·h^?1);树干液流速率与太阳总辐射、空气温度、风速、饱和水气压差呈正相关关系,与空气湿度呈负相关关系;影响春季、秋季胡杨液流速率的主要气象因子是太阳总辐射和空气温度,夏季为太阳总辐射和空气相对湿度;不同季节胡杨液流速率与空气温度、空气相对湿度、风速、饱和水气压差的日变化响应呈顺时针环状,与太阳辐射响应呈逆时针环状;不同季节胡杨液流速率对气象因子的响应规律存在差异。这表明胡杨为了保持水分平衡应对水分亏缺的策略不同,在一定条件下(极端干旱)通过气孔调节降低水分损失。研究结果对于明确干旱沙漠环境中胡杨水分传输对环境因子的响应规律及更深入地认识胡杨适应干旱环境的水分利用策略具有重要意义。     

Effect of antecedent soil water content and rainfall regime on microrelief changes

Surface microrelief substantially affects surface sealing, runoff, and soil erosion processes on bare soils. Yet, the stability of microrelief for different antecedent soil water contents and rainstorms is not well understood. This study investigates the effect of surface microrelief and antecedent water content on the decay of microrelief under different rainstorm regimes. Two different rainstorm regimes were studied in laboratory experiments: continuous rainfall for a total amount of 60 mm applied at 30 mm/h intensity, and intermittent rainfall consisting of five successive rainstorms of 12 mm each, again with an intensity of 30 mm/h and separated by one week drying cycles. Rough, medium, and fine microrelief surface conditions representing different degrees of seedbed preparation were studied for three soils at antecedent soil water contents of 2–4% and 14–20%. Before and after rainfall, digital elevation models determining the surface microrelief were developed using a laser scanner with 2 mm grid spacing. The specific surface area calculated from microrelief data was used as an index to characterize microrelief. Microrelief stability increased with increasing initial roughness and was much higher for the antecedent wet soils than for the dry soils. Microrelief stability for the continuous rainstorm regime was higher than for intermittent rainfall. Differences in microrelief stability were mostly attributed to different aggregate stabilities. Additionally, the higher stability for the rougher microrelief surfaces was attributed to the lower drop impact density and splash density on the surfaces with larger specific surface area. Aggregate slaking due to air escape and rapid wetting was found to be responsible for the low microrelief stability at initially dry conditions.     

Morphology and formation mechanism of sand shadow dunes on the Qinghai-Tibet Plateau

The formation and development of dunes depend on wind-blown sand movement which is affected by the characteristics of sand material, topography, wind regimes and other factors. In this paper, we investigated two sand shadow dune groups in Shigatse and Za’gya Zangbo of Tibet and an individual dune in Da Qaidam of Qinghai, and analyzed their topographies and morphologies, and the physical characteristics of the sand, wind regime and sand transport. Formed under harsh conditions behind hills, these mature sand shadow dunes are hundreds of meters long, have significant ridges and crescent dunes downwind, and have a hill pass on one or both sides. Wind tunnel experiments revealed that the hill gap and wind velocity are important factors in the formation of these dunes. Sand shadow dunes formed only when the gap spacing is two-thirds of the hill height. When wind velocities are 20 m/s, the sand body is divided into two parts. The hill pass allows the transport of sand by wind, creating a "narrow-pipe effect", which causes the transported material to gradually accumulate in the center of the shadow zone. We observed that the following are needed for sand shadow dunes to form:(1) strong winds, sufficient sand, suitable obstacles and a dry climate;(2) one or both sides of the obstacle forming the shadow zone must have a hill pass; and(3) the windward side of the obstacle must have a wide, flat area, providing adequate spacing for wind flow and transport of material and the leeward side must have a sufficiently broad, flat area to allow the release of the transported material. Research results on these newly discovered dunes on the Qinghai-Tibet Plateau could contribute to the understanding of dune geomorphology.     

西北干旱半干旱区生态系统碳循环研究进展

干旱半干旱区是陆地生态系统的重要组成部分,在陆地生态系统碳循环过程中起着非常重要的作用,了解该区目前碳循环研究现状对准确评估陆地生态系统碳收支具有重要意义。概述了碳循环的基本概念,归纳了影响干旱半干旱区碳循环的环境因素（辐射,温度,水分条件等）,并总结了目前该区域碳通量研究现状。指出目前干旱半干旱区生态系统碳循环研究仍存在诸多薄弱环节,最后提出今后重点研究的方向：(1)不同时空尺度生态系统碳循环研究;(2)碳源/汇的物理、化学以及生物过程的研究;(3)从整体和系统的角度来研究干旱半干旱区生态系统碳循环;(4)制定统一的野外监测与试验方法。     

软儿梨果肉中黄酮类化合物的提取及含量测定

以青海产软儿梨为试材,以乙醇为提取剂,通过单因素、正交实验对黄酮类化合物进行提取,研究其最佳提取条件。结果表明:提取的最佳条件为乙醇浓度95%,浸提温度为80℃,乙醇加入量为90mL,浸提时间为3.0h。以芦丁为标准物,通过分光光度法测定软儿梨果肉中总黄酮的含量为0.0189g/100g。     

敦煌阳关国家级自然保护区湿地现状及保护对策

阐述了甘肃敦煌阳关国家级自然保护区湿地资源的类型和特点,分析了保护区湿地保护和利用存在的问题,提出了加大宣传教育,提高环保意识;制定科学合理的湿地保护、恢复和开发规划;提高科研监测水平;实施湿地恢复工程;加强环境监测等保护对策。     

甘肃敦煌西湖多枝柽柳群落特征和种群格局

为阐明多枝柽柳的群落特征和种群格局,选择甘肃敦煌西湖国家级自然保护区作为调查地点,在2006年10月和2007年6月分别调查了35个20m×20m的样方,采集了经纬度、海拔和土壤类型等环境因子数据,运用物种丰富度指数、物种多样性指数和物种均匀度指数等多样性指标及丛生指标、平均拥挤度、聚块性指数、扩散系数和负二项参数等聚集强度指标进行分析。结果表明:多枝柽柳群落中共记录植物20种,分属12科19属,其中,灌木层8种,分属5科8属,草本层12种,分属7科11属;该群落可划分为4个群丛组:Ⅰ多枝柽柳-芦苇群丛组;Ⅱ多枝柽柳+苏枸杞群丛组;Ⅲ多枝柽柳+盐节木群丛组;Ⅳ多枝柽柳沙包群丛组。多枝柽柳群落的物种丰富度指数为0.375,物种多样性指数为0.330,物种均匀度指数为0.487。从群丛组间比较来看,物种丰富度指数和物种多样性指数呈现相同的分布规律,依次为ⅢⅡⅠⅣ;物种均匀度指数依次为ⅢⅣⅡⅠ。从指数间的相关性分析来看,物种多样性指数与物种均匀度指数呈极显著正相关,相关系数达0.920(α0.01)。种群格局分析表明,多枝柽柳和共建种芦苇的种群空间分布都呈显著的聚集分布,且芦苇对空间的侵占和填充能力要强于多枝柽柳。     

不同预处理对酸枣种子发芽的影响

酸枣种子硬实率高达93.4%,自然条件下较难发芽出苗,进行一定处理可提高种子发芽率,有利于生产实践。本次试验对酸枣种子进行20 d和30 d层积催芽,60℃和35℃的温水浸种,浓硫酸浸种,4%NaOH浸种,29%H2O2浸种等预处理,测定不同的预处理方法对酸枣种子发芽的影响。结果表明：在发芽试验中,不同的预处理显著地提高了酸枣种子的发芽率,不同的预处理方法对种子发芽率的影响不同,低温层积30 d＋98%硫酸带壳浸泡30 min＋清水浸泡24 h＋60℃温水浸泡48 h可以使酸枣种子的发芽率达到最高。     

青藏高原冻融风蚀形成机理的实验研究

青藏高原独特的高寒环境,冻融作用强烈,在干旱多风的气候条件下,容易产生风蚀,导致沙漠化的出现。冻融风蚀作为冻融侵蚀的一种主要形式,在青藏高原表现得尤为突出。为此,对青藏高原采集的土样进行了冻融风蚀模拟实验。结果表明,风蚀强度随着冻融循环次数的增多、冻融过程中含水量以及冻融温差的增大而增强,因此,在水分参与条件下,反复、剧烈的冻融作用所引起的土体结构的破坏是青藏高原冻融风蚀产生的主要原因,而挟沙风又是其主要动力。