五种沙生植物根际土壤的盐分状况

以根袋模拟法,研究了古尔班通古特沙漠5种常见沙生植物梭梭(Haloxylon ammodendron Bge)、白梭梭(Haloxylon persicum Bge)、刺沙蓬(Salsola Rathenica Iljin)、骆驼蓬(Peganum harmala Linn)和骆驼刺(Alhagi sparsifolia Shap)根际土壤的pH值和盐分状况,结果表明:5种植物根际土壤的pH值均小于非根际土壤,其中梭梭根际土壤和非根际土壤差值最大,达0.3个单位;5种供试植物根际土壤的电导率均高于非根际土壤,除刺沙蓬外其它供试植物均差异显著(p<0.05);可溶性总盐含量在根际土壤中均出现了聚集的现象,主要是SO42-、Ca2+和Mg2在根际的聚集,Cl-主要在骆驼刺根际中出现了聚集现象,在其他植物根际和非根际中没有显著变化;5种供试植物中骆驼刺根际土壤盐分聚集最为明显;从Cl-/SO42-、Na+/K+、Na+/Ca2+和Na+/Mg2+的值可以看出,沙生植物根际土壤主要是硫酸钙、镁盐的聚集,而非氯化钠的聚集。以上结果说明,沙生植物能够通过根际调节降低根际土壤的pH值,从而促进植物对土壤中养分以及水分的利用,同时沙生植物根际土壤中盐分聚集的现象为植物根际的"盐岛"效应的发生提供了很好的依据

树干径流对梭梭“肥岛”和“盐岛”效应的作用机制

为探明荒漠灌木个体周围土壤养分和盐分的空间分布及其成因，以荒漠灌木梭梭( Haloxylon ammodendron Bge． ) 为研究对象，对其周围土壤 pH 值，电导率，有机碳，全氮和有效磷的空间异质性以及树干径流的化学性质进行了研究。结果表明: 树干周围出现显著的“肥岛”效应，且土壤有机碳，全氮和有效磷的“肥岛”作用范围发生在距主根大约 20—40 cm 以内。土壤 pH 值和电导率在主根周围 25 cm 以内的值却显著低于外围，而在离主根 25 cm 处出现了“盐岛”，即在梭梭主根中心形成了一种高养分、低盐和低 pH 值的环境。树干径流和自然降雨化学性质的对比研究表明: 除 pH 值和 CO2－3外，树干径流中其他化学离子的含量均显著高于自然降雨中的含量，说明这种高养分、低盐分的环境是由树干径流引起的，也就是树干径流带给土壤养分的同时将盐分带走

Overview of soil forming process of aeolian sandy soil under the effect of artificial shelter-belt

人工防护林是防风固沙、有效防治沙漠化的重要措施之一。在沙漠地区建立人工防护林，可以有效防止土壤侵蚀，促进土壤有机质及黏粒积累，促使地表结皮形成，不仅对流沙起到了固定作用，而且促进了风沙土的成土过程。本文结合植物－土壤相互作用理论，分别从植物地上部分对养分的阻滞、聚集和减少土壤表面蒸发，以及地下部分的固沙和物质的分解与营养补给等方面综述了生物防护林在风沙土成土过程中的作用。同时，从以往的研究发现，在风沙土成土过程中，土壤机械组成变细，比重和容重减小；土壤剖面结构分异显著，分层增加；土壤含水量和养分显著聚集；土壤微生物数量和种类增加，活性增强，酶活性也大幅度提高。总之，随着沙漠生物防护林的建造，林下风沙土性质发生了明显的改良作用，逐渐发展成固定风沙土。说明人工防护林和风沙土的成土过程是协同发展的，这不仅有利于沙漠防护林的可持续管护，也有利于沙漠化的防治和退化生态系统的恢复与重建

Spatio-temporal dynamics of soil salt under saline irrigation in Taklimakan Desert artificial shelterbelt

Irrigation with saline water is in risk of soil salinity, which is a major threat for plant growth since salinity stored within the root zone. To determine the effects of saline irrigation on soil salinity, an experiment was carried out at the artificial shelterbelt in Taklimakan Desert Highway to examine soil salinity under different salt concentration irrigation. The rationale for conducting this study was to understand the movement for salinity in soil profile under saline irrigation. The results showed that topsoil (0-5 cm) salinity was greatly correlated with the mineralization of irrigation water, at temporal scale. During an irrigation cycle, the topsoil salinity increased at first four days, the largest soil salinity presented at the 4th day (11.7 dS m-1), and then presented a decreasing trend at the last ten days, while at the under layers (5-210 cm), soil salts were great less than the topsoil, and presented a decreasing trend within an irrigation cycle. During a growing season, topsoil salts presented a unimodal distribution under higher salinity irrigation (28 g L-1), from Apr to Jul it presented a rising trend, and then presented a decreasing trend to Oct, and the larger salinity presented from Jun to Aug, this phenomenon because great higher evaporation during Jun to Aug which lead to upward flux exceeding downward flux, while soil salinity did not change much throughout the soil profile of 5 cm to 200 cm. Yearly dynamics for topsoil salinity presented an increasing trend with the irrigation years, and also changed little at the under layers (5 cm to 210 cm) from 2002 to 2008. The spatial or profile distribution for soil salt showed salt not only accumulated at the topsoil, but also leached to the under layers (130 to 280 cm) and ground water (410 cm), but no salinity at the root zone(5 to 130 cm). These results documented that even with saline irrigation in Taklimakan Desert Highway artificial shelterbelt; it will lead no sodality for plants, since the content of soil salt at root zone was small (about 0.4 dS m-1). Therefore, saline groundwater should be used for protecting the Taklimakan Desert Highway. However, the impact of long-term irrigation with such salinity groundwater for vegetation should not be ignored; low saline water and also limiting irrigation quantities and frequency should be considered in future

干旱区植物根际土壤养分状况的对比研究/Nutrition in the rhizosphere of five xerophytic plants[J]

利用根袋模拟实验方法,研究了古尔班通古特沙漠南缘5种常见植物梭梭(Haloxylon ammodendron)、白梭梭(Haloxylon persicum)、刺沙蓬(Salsola ruathenica)、骆驼蓬(Peganum harmala)和骆驼刺(Alhagi sparsifolia)的根际和非根际土壤的pH值及养分含量状况.结果表明:干旱区五种植物均可以通过根系调节降低根际土壤pH,且梭梭根际和非根际的pH值差异显著.有机质含量除梭梭和白梭梭外均在根际显著聚集,其根际聚集率分别为刺沙蓬110.27%,骆驼蓬113.08%,骆驼刺为126.73%.全氮含量在刺沙蓬和骆驼蓬的根际中亏缺显著,亏缺率分别达24.54%和18.75%.而在骆驼刺根际中却显著聚集,聚集率为120.43%.有效氮在根际和非根际中的含量与全氮相反,刺沙蓬和骆驼蓬根际中聚集率分别为178.16%和151.76%,而在骆驼刺根际中亏缺率为45.79%.全磷含量和全钾含量在根际和给根际问均无显著差异.有效磷含量在刺沙蓬和骆驼蓬根际中出现了显著亏缺.速效钾含量在梭梭根际中表现为亏缺,在骆驼刺中表现为富集,而在其余3种植物中差异不显著.总之,5种干旱区植物均表现出不同程度的根际效应,对降低根际土的pH值、提高根际有机质含量有积极作用,对5种不同生活型植物的对比表明梭梭和白梭梭两种荒漠灌木在1 a的盆栽实验中,其根际效应没有草本植物根际效应大