民勤绿洲边缘积沙带形成的环境条件

甘肃河西地区经过60多年的防沙治沙,在绿洲边缘形成了一条积沙带。民勤绿洲边缘积沙带高4.8~18.6 m,宽30.4~461.4 m。为什么有的地段积沙带高大,而有的地段积沙带相对矮小,或者有的地段积沙带较宽,而有的地段积沙带较窄?对此,以民勤为研究区,通过对民勤绿洲边缘积沙带进行了调查,运用相关分析等方法和SPSS软件进行了分析。结果表明:(1)民勤绿洲边缘积沙带按形成方式可分为天然灌丛积沙带、乔木林带积沙带、人工固沙林积沙带3种,其中天然灌丛形成的积沙带相对高大,而农田边缘单纯的乔木林带形成的积沙带最窄。(2)控制积沙带高度的环境因子主要是积沙带与主风向的夹角,即积沙带与主风向的夹角越小,则积沙带的高度越低。上风向对准风沙口时,则积沙带与主风向的夹角越小,积沙带的宽度亦越小。(3)典型相关分析结果好于单相关分析。结果显示,积沙带的形态主要是由其宽度、宽高比和断面形状决定的,而影响积沙带形态特征的环境因子主要是上风向是否对准风沙口以及沙源的距离,亦即当上风向未对准风沙口时积沙带较宽且断面积较大,积沙带与上风向沙源距离越小则积沙带越高大。

民勤沙区胡杨林健康序列及其影响因子分析

运用50个胡杨林样地调查资料对民勤沙区的胡杨林健康状况进行模糊判别分类,并以其中19个样地的土壤取样测定数据,分析胡杨健康指标及伴生植物健康指标与土壤水分、土壤pH值、土壤有机质、土壤全N、土壤速效P以及土壤粒度的关系。模糊判别分类结果表明,健康序列1的胡杨无枯枝枯梢且更新苗相对最多;健康序列2的胡杨植株最高且龄级数最全,更新苗次多;健康序列5的胡杨过熟株、成熟株、中龄株和幼龄株均有枯枝枯梢,且样地上无更新苗。胡杨林健康指标与土壤水分、土壤pH值、土壤养分及土壤粒度的相关分析结果表明,越是靠近农田水分条件好的地块胡杨林的健康状况相对越好;土壤pH值在8.0左右时胡杨林的健康状况相对较好,土壤pH值>8.5胡杨林健康状况最差;胡杨林的健康状况与土壤有机质和全N及速效P含量正相关;健康状况较好的胡杨林地土壤中细砂、粉粒和粘粒含量较高。在民勤沙区,土壤干旱缺水是导致胡杨林退化的主要原因,土壤pH值在8.0左右的微碱性细沙地上的胡杨林相对较健康。对目前退化的胡杨林应适当补充人工灌溉,使土壤含水率保持在5%以上。营造人工胡杨林要选择靠近农田边缘水分条件较好的地块。0~60 cm的土壤速效P和0~20 cm的土壤细砂含量较多的土壤胡杨更新苗相对较多,可作为选定胡杨造林地的依据之一。

苯多羧酸分子标志物对生物炭吸附磷行为的表征

生物炭因其具有多孔、比表面积较大、含氧官能团较为丰富且芳香性较强等优点而在农业面源污染控制方面具有良好的应用前景。然而,生物炭应用于土壤后难以从土壤颗粒中分离出来,从而制约了其对农业面源污染物吸附行为的预测。分子标志物技术在表征有机碳行为领域做出了重要的贡献,苯多羧酸(Benzene polycarboxylic acids,BPCAs)分子标志物方法的引入,可为表征生物炭与磷之间相互作用提供新的视角。因此,本研究采用批量吸附实验,考察了烟秆和松木及其制备的生物炭对磷的吸附行为。结果表明,随热解温度的升高,生物质及其生物炭中各BPCAs含量及苯六甲酸(Benzene hexacarboxylic acid,B6CA)对BPCA的贡献率随热解温度的升高而增加,生物炭的芳香缩合度不断增强;两类生物炭对磷的吸附量均随热解温度的升高而降低,其中400℃烟秆生物炭和200℃松木生物炭对磷的吸附量最大。表面含氧官能团的减少和静电排斥作用降低了生物炭对磷的吸附,而较大的比表面积使烟秆生物炭的吸附量高于松木生物炭。烟秆生物炭中B6CA含量高于松木生物炭,因此其对磷的吸附量较松木生物炭高。

三种高原常见沉水植物对不同浓度铵氮的生理响应机制研究

分析植物受到高铵态氮胁迫时的响应特征,明确高浓度铵态氮对沉水植物产生毒性机制,为利用沉水植物修复高浓度铵态氮污染水体提供理论指导。选取苦草(Vallisneria natans)、大茨藻(Najas marina)和穿叶眼子菜(Potamogeton perfoliatus)3种沉水植物为研究对象,研究了不同浓度铵态氮(0、0.1、3、15和50 mg/L)对3种沉水植物的生理影响,初步探讨了沉水植物在高铵态氮浓度水体中退化的原因。当水体铵态氮浓度超过15 mg/L时,植物体内叶绿素和蛋白含量呈下降趋势,而游离氨基酸的含量呈上升趋势,植物叶绿素荧光值显著降低,植物无法正常进行光合作用。当铵态氮浓度低于15 mg/L时苦草对铵态氮的去除率明显低于大茨藻和穿叶眼子菜。铵态氮浓度较高时,大茨藻组织总氮含量高于穿叶眼子菜和苦草,而FAA和可溶性蛋白含量则是穿叶眼子菜最高。当水体中铵态氮浓度达到15 mg/L时,湖泊中广泛分布的沉水植物无法存活,植物光合能力下降是影响其存活的主要因素。本研究从机理层面初步揭示了3种广布沉水植物物种在高铵态氮水体中消失的原因。

Response of Grassland Vegetation to Air Temperature and Precipitation in Minqin Desert Region

[ Objective] This paper aims to analyze response characteristics of desert grassland vegetation to climate change. [ Method] The responses of grassland vegetation in desert region to air temperature/precipitation changes were analyzed by phenological observations since 1974, observation data conceming vegetation samples and meteorological data during the same period. The changing trend significance was denoted by linear trend line and its regression significance. The interrelation between the two variables was indicated by correlation coefficients. Data were analyzed by the software SPSS 13.0. [Result] （1） The rising rate of annual average temperature in the Minqin desert area since 1961 was greater than both the global level and Ghina＇s level over the past century. （2） Desert plants＇ response to temperature changes were mainly displayed as the advance of spring phenology, the delay of autumn phenology and the extension of growing duration. Plants＇ main response to precipitation changes was that vegetation coverage and pure coverage were decreasing along with precipitation reducing. （3） Both the vegetation coverage and pure coverage mainly had a positive correlation with the annual precipitation. Plant density mostly had a positive correlation with the precipitation in September. （4） The impact of rising temperature on plant phenology in spring was greater than that in autumn. [ Conclusion] The effects of temperature changes on desert grassland plants were the advance of spring phenology, the delay of autumn phenology, the extension of growing season and longer plant growing period than that in other reports. The responses of desert grassland vegetation to precipitation changes were that both vegetation coverage and pure coverage were decreasing along with precipitation reducing, and plant density fluctuated along with precipitation change.

Estimation of Relative Ecological Value of Returning Farmland to Forest & Mountain Enclosure for Grazing Prohibition——A case study in Yongxing Township of Jingyuan County,Gansu Province

[Objective]Returning farmland to forest and mountain enclosure for grazing prohibition ecological effect and economy rationality were explored.[Methods]A case study of returning farmland to forest and barren hills grazing prohibition in Yongxing Township of Jingyuan County was used to discuss and estimate the relative ecological function and relative ecological value.[Results]1）The ecological value of the forest of returning farmland was far more than the sum of the ecological value of farm crops and the agricultural output,and also more than the national subsidy standard.So the state policy of returning farmland to forests is not only favorable to local eco-environment restoration,but also reasonable in economic development.2）The ecological value of mountain enclosure for grazing prohibition was less than the opportunity cost of prohibiting grazing,also less than the national subsidy standard.The sum of the relative ecological value of prohibiting grazing and the state subsidies was more than the opportunity cost of prohibiting grazing.However,the ecological value of new vegetation through returning farmland to forest project was greater than the China＇s average ecological value of grassland.[Conclusion]The relative ecological value can be used to solve the problems in the equivalent conversion among various ecological indexes and between ecological indexes and economic indexes.

集沙仪开发研究现状、问题及突破点

输沙(尘)量观测是沙漠化监测、沙尘暴和风沙流研究以及土地风蚀沙化研究的主要内容之一,也是干旱沙漠化地区生态环境观测研究的重要手段之一。集沙仪是其监测必不可少的重要工具之一。目前,开发研制的集沙仪不少,但至今没有统一的观测标准和准确有效的观测仪器。国外用光学颗粒流传感器和等动力方法检验集沙仪的集沙效率,结果表明,集沙仪的集沙效率低于70%。中国多采用风洞测验集沙仪的集沙效率,检验结果为72%~89%。集沙仪开发的难点是难以使得集沙仪管内气流速度等于外界风速,突破点是研制出管内气流流速等于外界风速的集沙仪。主动式集沙仪可解决这一问题。然而,由于需要动力等原因,而未真正进入应用。需要制订统一的观测标准,提高集沙仪开发研制质量和观测质量。这样,才能揭示沙尘暴、风沙流的真实情况,也便于纵向和横向对比分析,有效推进沙漠化和沙尘暴研究的进程。

民勤绿洲边缘积沙带的稳定性动态

甘肃河西走廊经过60年的防沙治沙,在绿洲上风向边缘形成了一条流沙堆积带,即积沙带。其中,民勤绿洲上风向边缘的积沙带最高大、最连续。为了揭示积沙带的稳定性动态,在民勤绿洲上风向边缘设置11条观测样线,从2016年11月上旬至2019年4月上旬进行了7次风蚀积沙观测和沙面特征点位移观测。民勤绿洲上风向边缘积沙带按形成方式可分为人工固沙林积沙带、天然灌丛积沙带和乔灌木混交单行林积沙带。结果表明:人工固沙林积沙带风蚀最严重且前移速率最快,天然灌丛积沙带次之;风蚀程度越轻则积沙带前移速率就越慢,草本植物盖度越高沙面风蚀程度就越轻,积沙带前移速率就越慢。草本植物盖度与沙面稳定性二者相辅相成;积沙带迎风坡为风蚀面,而背风坡为积沙面,一蚀一积,维持着积沙带的前移及其动态稳定性。

利用分子生物标志物法揭示种植芭蕉的农业土壤中有机质的来源与降解

采集并比较两类不同耕作活动下的土壤(BJ和YS),利用分子生物标志物法对其中土壤有机质(SOM)的组成、分布特征和降解状态进行分析比较,以研究不同耕作活动对SOM的影响。土壤总碳含量从1.75%(YS)降低至1.58%(BJ),表明BJ中SOM的含量显著下降;脂肪酸的含量从127.22 mg g^(-1) C(YS)增大至345.09 mg g^(-1) C(BJ),长链烷烃C29、C31,以及芭蕉叶和茎中未检测到的烷醇在BJ中大量出现,表明芭蕉来源有机质的大量输入。C/N值从14.94(YS)降低至11.47(BJ),烷烃的ACLFA值从23.87(YS)增大至24.97(BJ),3,5-DHBA/V值从0.52(YS)增大至0.64(BJ),表明BJ的降解程度高于YS。短链烷烃和木质素V类可能来自原始土壤中的有机无机复合体。以上结果证明:人为耕作活动加速了SOM在土壤中的周转。广泛了解人为耕作活动对SOM的影响,将会为土壤经营管理以及估算受人为干扰的生态系统中的碳循环提供重要的信息。