三北防护林体系建设前后华北春季生态环境对比   总被引：4，自引：0，他引：4  

钟中  王汉杰 《气象》2001,27(9):13-17

利用三北防护林体系建设前后华北地区长期定点观测资料，对该地区春季生态环境的变化进行了对比分析。分析表明，防护林体系建设以后，除日照有所减少、温度日较差减不春季农作物生长有一些不利影响外，其它生态环境因子都是向着有利于作物生长和改善生存环境方向变化的。  相似文献   

植物生物条件下荒漠土壤水分预报的数学模型   总被引：2，自引：2，他引：2  

朱永华  吕海深等 《冰川冻土》2001,23(3):264-269

通过对生长了3a的荒漠植物骆驼刺的根系分布规律及不同深度土壤含水量分布资料的研究，利用动态模拟方程，分析了骆驼刺根系吸水的分布规律，以及根系吸水与其影响因素之间的关系，用多元回归分析方法拟合了骆驼刺根系吸水的数学模型，利用所得到的骆驼刺根系吸水模式对实验地的土壤水分动态进行了模拟，模拟值与实测值比较表明结果具有一定的精度。  相似文献   

表生作用下稀土元素地球化学特征——以海南岛北部玄武岩分布区为例   总被引：7，自引：0，他引：7  

黄成敏  龚子同 《山地学报》2002,20(1):70-74

对海南岛北部玄武岩区岩石-土壤-植物-地下水系统中稀土元素迁移和分布模式的研究表明，随土壤的发育，REE出现分异，LREE逐渐富集；Ce由玄武岩中的负异常向土壤中正异常演化。地下水中REE的含量和分布模式主要受岩石风化和成土作用影响。植物虽对REE具有选择吸收作用，但REE的生物地球化学循环不活跃。  相似文献   

A multi-proxy analysis of climate impacts on the recent development of subarctic Lake Saanajärvi in Finnish Lapland     

A. Korhola  S. Sorvari  M. Rautio  P.G. Appleby  J.A. Dearing  Y. Hu  N. Rose  A. Lami  N.G. Camerson 《Journal of Paleolimnology》2002,28(1):59-77

Responses to recent climatic changes in the sediment of subarctic Lake Saanajärvi in northwestern Finnish Lapland are studied by comparison of various biological and sedimentological proxies with the 200-year long climate record, specifically reconstructed for the site using a data-set of European-wide meteorological data. The multi-proxy evidence of simultaneously changing diatom, Cladocera, and chrysophyte assemblages along with the increased rates of organic matter accumulation and pigment concentrations suggest that the lake has undergone a distinct typological change starting from the turn of the 20th century. This change, indicating an increase in lake productivity, parallels a pronounced rise in the meteorologically reconstructed mean annual and summer temperatures in the region between ca. 1850 and 1930's. We postulate that, during the Little Ice Age, the lake was not, or was only weakly, thermally stratified during summer, whereas the subsequent increase in air and hence epilimnetic water temperatures resulted in the development of the present summer stratification. The increased thermal stability of the lake created more suitable conditions for the growth of phyto- and zooplankton and changed the overall primary production from benthos to plankton. Mineral magnetic and carbonaceous particle records suggest long-distance pollution, particularly since the 1920's, yet the observed changes in lake biota and productivity can hardly be explained by this very minor background pollution; the 20th century species configurations are typical of neutral waters and do not indicate any response to pollution.  相似文献   

Plant life-form and germination in a Mexican inter-tropical desert: effects of soil water potential and temperature     

Joel Flores  Oscar Briones 《Journal of Arid Environments》2001,47(4):485

We investigated the effects of soil water potential (SWP) and temperature on seed germination of six coexisting species of an inter-tropical desert. These species include three life-forms; the shrubs Cercidium praecox andProsopis laevigata ; the columnar succulents Neobuxbaumia tetetzo and Pachycereus hollianus; and the arborescent semi-succulents Beaucarnea gracilis and Yucca periculosa. In the six species germinability increased and germination time and speed of germination (t⁵⁰) decreased as SWP decreased. The SWP treatments were 0 MPa, −0·12 MPa, −0·2 MPa, −0·41 MPa and −0·66 MPa. There was, however, a SWP threshold below which germination time and t⁵⁰increased and germinability decreased. The shrubs had the highest germinability whereas the columnar succulents had the lowest. The shrubs also had shorter germination time andt⁵⁰ than arborescent semi-succulents whereas seeds of the columnar succulents were indeterminate. In all species except P. laevigata germinability increased and the germination time and t⁵⁰decreased as temperature increased. The temperature treatments were 12°C, 20°C and 26°C. The shrubs had the shortest t⁵⁰and germination time and the highest germinability at all temperatures. Arborescent semi-succulents had the lowest germinability and longest germination time and t⁵⁰at the three temperatures treatments. Our results support the hypothesis that in desert environments different plant life-forms utilise different germination strategies to persist.  相似文献   

大地震发生的网络性质——兼论有关地震预测的争论   总被引：16，自引：0，他引：16  

郑宝山  王滨滨  朱广伟  余孝颖 《地学前缘》2001,8(2):0-0

大量研究结果证实 ,人体摄入的碘 80 %以上来自于食品 ,因此 ,碘缺乏病病区的形成应归因于植物含碘量的区域性差异。植物中的碘来自于大气和土壤 ,至今科学尚不能搞清在不同情况下 ,哪一部分碘占据主要部分。土壤中的碘与成土母岩中的碘含量基本无关 ,土壤碘含量主要决定于母岩风化产物对大气干湿沉降碘的吸收和保持能力。限于植物和大气中碘测定的困难 ,在碘的地球化学与碘缺乏病病区成因的问题上 ,目前仍有许多未解之谜。笔者提出 ,土壤中某种形态的碘可能以气态挥发并在近地大气层富集 ,存在植物吸收利用这一部分碘的条件的地区 ,不会有碘缺乏病的流行。  相似文献   

试论榆神煤炭液化性能及拟建液化厂的外部环境     

段中会  鲁文宇等 《中国煤田地质》2001,13(1):19-21,43

榆神煤液化效果好，主要液化指标较高，是适于直接液化的原料用煤，在榆神矿区建设煤直接液化厂具备优越的内，外部条件。  相似文献   

若尔盖地区泥炭资源的开发与珍稀动物资源的保护     

何光荣 《四川地质学报》1992,(3)

若尔盖地区广布的沼泽地蕴藏着丰富的泥炭资源,北区部分泥炭沼泽地又是珍稀动物赖以生存的栖息场所,全面开发泥炭资源势必影响珍稀动物的生存。本文根据泥炭资源分布规律与珍稀动物的分布、活动规律及其相关性,论述了泥炭资源合理开发与珍稀动物资源保护,二者兼顾的意见。  相似文献   

辽宁核电站温坨子厂址设计墓准地面运动SL_2和SL_1的确定     

钟以章  王国新 《中国地震》1994,(1)

本文在综合厂址及区域地震地质资料的基础上，采用地震构造法、综合概率法和最大历史地震法分别计算了辽宁核电站温坨子厂址的极限安全地震动（ＳＬ２），计算结果分别是１７７ｃｍ／ｓ２，１７５ｃｍ／ｓ２和８９ｃｍ／ｓ２，取其中的最大值１７７ｃｍ／ｓ２。为安全起见，建议将ＳＬ２取值２００ｃｍ／ｓ２。运行安全地震动（ＳＬ１）按５０年０．１超越概率和ＳＬ２／２选取，采用两者的较大值，确定为１００ｃｍ／ｓ２。  相似文献   

一二年生植物在坝上沙质退耕地上的引种筛选     

赵雪  张强 《中国沙漠》1994,14(4):60-65

一二年生植物引种成功的种源区域范围及科属范围都较多年生植物广，而对土壤基质、水分、人为活动等具体生境差异反应明显。最佳的引种植物有临夏燕麦、丹麦４４４燕麦、黑圆箭舌豌豆、３３３Ａ箭舌豌豆及Ｐｈａｌａｒｉｓ属的几个种等。  相似文献