兰州削山填沟整地工程主要环境影响及防治对策

针对兰州市以缓解建设用地紧张为目的的削山填沟整地工程,本文在分析拟整地区域自然环境、人文环境特性的基础上,预测了整地工程实施对兰州环境空气、水土流失、土地利用和绿化条件等的影响,提出了防治施工扬尘、减少不良环境影响的措施,为合理有序地开发荒山荒沟,保障生态环境安全提供了技术支撑。     

荒漠河谷胡杨残林复壮更新试验研究

胡杨(Populus euphratica)在额济纳荒漠绿洲中的生态地位极其重要,与绿洲的兴衰息息相关。额济纳荒漠绿洲的胡杨林,目前由于河水泛滥受控制,使依赖于河漫滩而发芽生长的幼林所占林地面积比例下降,林地日趋老化、衰残,致胡杨日渐衰败,绿洲退缩。文中依据多年的试验调查数据,对荒漠河岸林胡杨残林复壮更新效果进行了分析研究。结果表明:围栏封育对加快荒漠河岸林的复壮更新和林下天然植被的恢复,起到了积极而显著的作用。开沟断根,打破了土壤表皮板结层,疏松了土壤,利于根蘖苗萌生,同时也促进了苗木侧根和须根的增加,扩大了根系吸收面积,使苗木生长量提高。间苗定株有效地促进了胡杨老树的根蘖更新。确定了河岸胡杨更新林合理密度为幼龄期为3330株/hm2,中龄期为1665株/hm2,近熟林期为600株/hm2,成熟林期为135株/hm2。在此基础上提出了全面保护好沿河现有胡杨残林的措施,实行分片、分段围栏封育和充分引用季节性河道来水浇灌的前提下,积极促进胡杨残林的复壮和根蘖更新,复壮更新。     

荒漠植物沙芥苗期对不同浓度NaCl的适应机制

本文研究了5周龄沙芥幼苗对不同浓度NaCl的适应机制。结果表明,沙芥苗期对不同浓度的NaCl具有不同的适应机制。与对照相比,在5 mmol/L的低浓度NaCl下,沙芥叶的干重和含水量分别显著增加了25%和35%(P<0.05),沙芥正是通过这种植株的快速生长和含水量的增加将进入体内过多的Na⁺稀释至毒害水平以下,以适应外界低浓度的NaCl。在50 mmol/L的中等浓度NaCl下,沙芥限制了K⁺、增强了Na⁺从根向叶的选择性运输,使叶中的Na⁺含量显著增加了8倍(P<0.05),沙芥最可能是将叶中积累的大量Na⁺区域化至液泡中来适应外界中等浓度的NaCl,该机制避免了Na⁺对叶细胞的伤害,使叶的渗透势显著降低了75%(P<0.05),让植株有效地抵御了盐分产生的渗透胁迫,维持了沙芥的正常生长。沙芥主要通过限制Na⁺、增强K⁺的选择性吸收和从根向叶的选择性运输来适应外界高浓度的NaCl。在200 mmol/L的高浓度NaCl下,该机制使沙芥叶中积累的K⁺较50 mmol/L的NaCl下显著增加了55%(P<0.05),使K⁺对渗透调节的贡献率也相应地从10.28%提高到了12.51%,K⁺一般积累于细胞质中,因此该机制有利于叶细胞质保持较低的Na⁺/K⁺、减缓Na⁺对叶的伤害,也有利于细胞质平衡来自胞内液泡和胞外高浓度NaCl产生的渗透压、减少叶的渗透伤害。尽管如此,在200 mmol/L的NaCl下,沙芥幼苗生长了7 d便使其叶的干重显著降低了51%(P<0.05),表明沙芥苗期的耐盐性有限。     

模拟放牧对高寒草甸丛枝菌根真菌的影响

采用植物样方调查与丛枝菌根（AM）真菌的形态分子鉴定等方法分析了模拟放牧对地上植物及地下AM真菌群落的影响。结果表明：随着放牧程度的增加,地上植物的物种丰富度显著降低,但AM真菌的物种丰富度没有显著变化;AM真菌总侵染率与丛枝侵染率随着放牧强度的增加显著降低,但泡囊侵染与土壤AM真菌的孢子密度均不受放牧强度的显著影响;模拟放牧对植物群落组成具有显著影响,但AM真菌的群落组成不受放牧的影响。以上结果表明较植物群落而言,AM真菌对放牧干扰具有较高的耐受性,凸显了在放牧干扰条件下,AM真菌在维持高寒草甸生物多样性过程中的作用。     

草铵膦对斑马鱼胚胎及仔鱼的毒性研究

草铵膦(glufosinate-ammonium,GLA)是一种广谱触杀型非选择性除草剂,随着在生产中应用的不断增加,其生物安全性也越来越受到人们的重视。试验以斑马鱼Danio rerio胚胎为动物模型,用不同剂量的草铵膦染毒受精后2h的斑马鱼胚胎,观察其死亡率和形态学变化,并应用原位杂交和QRT-PCR技术检测了Vasa基因表达情况,以分析草铵膦的毒性作用。结果表明:1.6μg/L的草铵膦对斑马鱼胚胎有显著致死作用、1.3μg/L的草铵膦有显著致畸作用,其中畸形表现为尾部弯曲和阻碍黑色素沉着。原位杂交结果显示:1.3μg/L的草铵膦可引起Vasa表达的部分缺失,QRT-PCR定量分析发现,草铵膦可引起斑马鱼胚胎Vasa基因表达水平下调3.8倍。表明草铵膦对斑马鱼胚胎有较强的致死毒性、致畸作用和潜在的生殖毒性。     

西北黄土高原半干旱区全膜微垄沟穴播对冬小麦耗水特性和水分利用效率的影响

【目的】西北黄土高原半干旱区降水稀少,且冬小麦生育期内50%以上为10 mm的无效降水。如何充分集蓄这部分降水,是该区冬小麦稳产高产和提高降水利用效率的关键。【方法】于2011—2015年在西北黄土高原半干旱区(104°36′E,35°35′N)进行大田定位试验,以冬小麦中粮1号为试验材料,设全膜微垄沟穴播(PRF)、全膜覆土穴播(PMS)、覆砂穴播(SM)和露地穴播(CK)4个处理,测定冬小麦不同生育时期0—200 cm土层土壤含水量、生物量、产量及其构成因子,计算不同生育期土壤贮水量、阶段耗水量和水分利用效率(WUE)等,以明确PRF处理对土壤水分含量、冬小麦阶段耗水量、产量及WUE的影响。【结果】在播前和返青期,PRF处理在0—200 cm土层的土壤贮水量较PMS、SM处理和CK分别平均增加24.3、38.8、7.4 mm和18.2、26.9、67.8 mm。PRF处理抽穗—灌浆期耗水量平均较PMS处理增加了36.0 mm,返青—抽穗和灌浆—成熟期耗水量平均较SM增加12.1和16.7 mm,较CK增加40.8和37.6 mm。PRF处理的生物量较PMS处理增加了2.2%—15.4%,分别在2011—2012年的灌浆期和成熟期、2014—2015年的苗期和抽穗期达显著差异,在苗期、抽穗期、灌浆期和成熟期显著高于SM和CK。公顷穗数、穗粒数和千粒重4年均表现为PRF处理PMS处理SM处理,3个处理间无显著差异,但均显著高于CK。PRF处理的产量最高,为4 373.6—4 950.0 kg·hm-2,较PMS处理增加2.4%—12.7%,并在2012—2013和2014—2015年达显著差异;显著高于SM处理(除2012—2013年)和CK(增产35.8%—43.8%)。PRF处理的WUE较PMS处理增加0.4%—12.8%,除2013—2014外均达显著性差异;显著高于SM处理(除2014—2015年)和CK(提高8.1%—42.1%)。【结论】全膜微垄沟穴播能较为充分地利用10 mm的无效降水,提高冬小麦播前和返青期0—200 cm土层的土壤贮水量,促进小麦灌浆期间耗水,增加公顷穗数、穗粒数和千粒重,提高小麦产量和水分利用效率,是西北黄土高原半干旱区冬小麦高产高效的种植模式。     

森林生态系统服务功能价值评估与分析

森林生态系统作为陆地生态系统的主体,其服务功能价值评估是当前生态学和经济学交叉领域的一大研究热点,本文参考《森林生态系统服务功能评估规范》(以下简称《规范》)标准,利用白水江国家级自然保护区森林生态系统实测数据和基于GIS和RS技术获得的不同林分面积等数据,评估保护区森林生态系统服务功能的价值。结果表明:保护区森林生态系统年均服务价值总计178.90亿元,各项服务价值排序为:生物多样性(43.08%)固碳释氧(19.35%)固土保肥(16.17%)涵养水源(13.11%)林产品(5.16%)净化大气(1.55%)林木营养物质积累(0.96%)旅游休憩(0.62%);按照服务价值利用类型排序为:间接利用价值(51.14%)非利用价值(43.08%)直接利用价值(5.78%)。通过对《规范》体系下不同研究成果的横向比较,不但可以校核研究结果的准确度,也可以揭示森林生态系统服务功能之间的规律。价值评估的测算结果对当地森林生态补偿机制的建立及其他环保政策的制定具有重要参考价值,同时该价值评估也有利于政府建立可持续的环境与经济综合核算体系。今后森林生态系统服务价值的研究应着重于加强对服务功能机制的探讨,研究生态系统服务价值的空间分布,重点开展服务价值的动态评估以及相关政策的制定等。      

Microbial diversity in the saline-alkali soil of a coastal Tamarix chinensis woodland at Bohai Bay,China

Soil salinization or alkalization is a form of soil desertification. Coastal saline-alkali soil represents a type of desert and a key system in the network of ecosystems at the continent-ocean interface. Tamarix chinensis is a drought-tolerant plant that is widely distributed in the coastal saline-alkali soil of Bohai Bay, China. In this study, we used 454 pyrosequencing techniques to investigate the characteristics and distribution of the microbial diversity in coastal saline-alkali soil of the T. chinensis woodland at Bohai Bay. A total of 20,315 sequences were obtained, representing 19 known bacterial phyla and a large proportion of unclassified bacteria at the phylum level. Proteobacteria, Acidobacteria and Actinobacteria were the predominant phyla. The coverage of T. chinensis affected the microbial composition. At the phylum level, the relative abundance of γ-Proteobacteria and Bacteroidetes decreased whereas Actinobacteria increased with the increasing coverage of T. chinensis. At the genus level, the proportions of Steroidobacter, Lechevalieria, Gp3 and Gp4 decreased with the increase of the vegetation coverage whereas the proportion of Nocardioides increased. A cluster analysis showed that the existing T. chinensis changed the niches for the microorganisms in the coastal saline-alkali soil, which caused changes in the microbial community. The analysis also distinguished the microbial community structure of the marginal area from those of the dense area and sparse area. Furthermore, the results also indicated that the distance to the seashore line could also affect certain groups of soil bacteria in this coastal saline-alkali soil, such as the family Cryomorphaceae and class Flavobacteria, whose population decreased as the distance increased. In addition, the seawater and temperature could be the driving factors that affected the changes.     

Pattern analysis of a linear dune field on the northern margin of Qarhan Salt Lake,northwestern China

In terms of formation mechanisms of linear dunes,there are open arguments for their widespread distribution and multi-morphological diversities.In order to clarify the formation mechanism of linear dunes of Qarhan Salt Lake,we used pattern analysis method to analyze the statistical characteristics and spatial variation of their pattern parameters.Except at the west-northwest margin,the pattern parameters showed regular spatial variation from the up-middle part towards the downwind end of the dune field.Based on the cumulative probability plots for inter-crest spacing and crest length,we divided the linear dunes into three groups,which corresponding to the three evolution stages of these dunes.The first group comprises erosional relics,with shorter crests,smaller inter-crest spacing and more random dune orientation.The second group comprises dunes whose sand supply is just sufficient to maintain stability and these dunes are approaching the net erosion stage.The crest length and inter-crest spacing of these dunes are much larger than those of the first group,and dune orientation is closer to the resultant drift direction (RDD) .The last group comprises linear dunes that are still undergoing vertical accretion and longitudinal elongation,which follows the RDD of the modern wind regime.The presence of regular spatial variation of pattern parameters and a similar geometry with the vegetated linear dunes suggest that deposition and erosion coexist in the development and evolution of linear dunes of Qarhan Salt Lake,i.e.deposition predominates at the downwind end of linear dunes in the vertical accretion and longitudinal elongation stage,whereas erosion mainly occurs at the upwind end of linear dunes in the degradation stage.Therefore,the formation mechanism of linear dunes in Qarhan Salt Lake can be reasonably explained by the combination of depositional and erosional theories.     

Optically stimulated luminescence dating of sandy deposits from Gulang county at the southern margin of the Tengger Desert,China

Aeolian deposits from the deserts in northern China have been used for palaeoenvironmental research to understand aeolian sedimentology and its dynamic connection to past climate conditions. The Tengger Desert in China is sensitive to the waxing and waning of the monsoonal system. In response to past climate change, the southern margin of the Tengger Desert has evolved significantly since the last glacial period. However, previous attempts to date aeolian deposits in this region were mainly based on radiocarbon dating, which has problems when applied to aeolian deposits. Moreover, sedimentary records are limited. Accordingly, past aeolian activity in this desert remains poorly understood. In the present study, we dated sand samples from Gulang county at the southern margin of the Tengger Desert using optically stimulated luminescence(OSL) to understand the history of aeolian activity in this region. Our samples represented well-sorted aeolian sands and sandy loess. Aeolian sands are evidence of dune field buildup and sparse vegetation cover whereas sandy loess is evidence of improved stabilization of sand dunes resulting from ameliorated vegetation cover. Certain samples showed a decline in the equivalent dose(De) values when successive integration intervals were applied, which resulted from unstable OSL signals from non-fast components in the initial part of the decay curve. In order to obtain reliable De estimates, we investigated component-resolved and different background subtraction approaches, and compared the resultant De estimates. We adopted the early background subtraction method to derive De values. Luminescence chronologies and sedimentary records indicated that sand dunes accumulation occurred before 10 ka, and sandy loess developed between 9.5 and 7.6 ka when sand dunes were stabilized as a result of increased effective moisture levels. The transition between sand dune mobilization and stabilization emphasizes the significance of an effective moisture threshold in controlling aeolian activity. Mobilization of sand dunes at ~2.3 ka might be related to an increased aridity during the Late Holocene.