土壤盐渍化及其危害的研究进展

土地盐碱化与水土流失、大气污染一样，成为日益严重的环境问题之一。土壤盐渍化破坏土地资源，阻碍农牧业发展，已成为危及人类生存与生活的重大资源问题。改善和利用大面积盐碱地荒漠，是科学研究工作者的艰巨任务。     

Spatial Variation of Soil Urease Activity Around Irrigated Date Palms

The inhibition of soil urease activity by the accumulation of soluble salts in a coastal region of the Sultanate of Oman susceptible to salinization was investigated . Soil transects around six individual date palms (Phoenix dactylifera L.) growing on commercially managed farms were intensively sampled and assayed for soil urease activity . Activities ranged from 0 . 10 to 39 . 85 mu g NH + 4 released g 1 soil h 1 at 37 C . Soil collected from within 70 cm of the palms h ad a higher urease activity than soil from a distance 1 . 5 m . Multiple regression analysis showed that more than 75 % of the variance in soil urease activity was accounted for by soil physi cochemical properties , except in sandy soils low in organic carbon ( C ). The soil properties most closely associated with urease activity were soil organic C , salinity , and texture . A scattergram of urease activity against salinity showed high variabil ity in activity at low salinities ( 0 . 5 dS m 1 in 1 :5 soil to water extracts ) and severe inhibition at salinity values 12 dS m 1. In nonsaline soils , variation in urease activity was closely associated with variations in organic C and clay con tents , whereas at saline conditions , only soil salinity was significantly associated with urease activity .     

Effects of increased salinity and an introduced predator on lowland amphibians in Southern China: Species identity matters

Approximately 30% of amphibian species are threatened due to a variety of factors affecting their habitats and physiology, yet contributions that interactions among factors make to population declines are not well-explored. Two factors, introduced mosquitofish (Gambusia affinis) and increased salinity, may coincide in lowland habitats used by breeding amphibians. Mosquitofish have been introduced worldwide and can be significant predators of amphibian larvae. Salinization of wetlands is an increasing problem globally due to (1) application of road deicing salts in temperate regions, (2) irrigation practices associated with intensive agriculture, and (3) saltwater intrusion due to sea-level rise. We investigated the effects of mosquitofish (G. affinis) and increasing salinity on five species of lowland wetland-breeding amphibians from southern China. We exposed anuran hatchlings to four salinity levels and two fish treatments and all combinations of the two factors in a series of experiments. Four of the species were susceptible to predation by mosquitofish, two were sensitive to increased salinity at concentrations >6% seawater, and one was tolerant of both increased salinity and mosquitofish. We found no interaction between the predator and increased salinity. Salinization and mosquitofish represent significant threats to lowland amphibians in this region and, coupled with the ongoing loss and degradation of lowland wetlands, portend a bleak future for lowland amphibian populations in the region.     

The 10 Australian ecosystems most vulnerable to tipping points

We identify the 10 major terrestrial and marine ecosystems in Australia most vulnerable to tipping points, in which modest environmental changes can cause disproportionately large changes in ecosystem properties. To accomplish this we independently surveyed the coauthors of this paper to produce a list of candidate ecosystems, and then refined this list during a 2-day workshop. The list includes (1) elevationally restricted mountain ecosystems, (2) tropical savannas, (3) coastal floodplains and wetlands, (4) coral reefs, (5) drier rainforests, (6) wetlands and floodplains in the Murray-Darling Basin, (7) the Mediterranean ecosystems of southwestern Australia, (8) offshore islands, (9) temperate eucalypt forests, and (10) salt marshes and mangroves. Some of these ecosystems are vulnerable to widespread phase-changes that could fundamentally alter ecosystem properties such as habitat structure, species composition, fire regimes, or carbon storage. Others appear susceptible to major changes across only part of their geographic range, whereas yet others are susceptible to a large-scale decline of key biotic components, such as small mammals or stream-dwelling amphibians. For each ecosystem we consider the intrinsic features and external drivers that render it susceptible to tipping points, and identify subtypes of the ecosystem that we deem to be especially vulnerable.     

吉林省大安市苏打碱土碱化参数之间的关系

选择典型苏打碱化土壤,对土壤碱化度(ESP)、钠吸附比(SAR)、残余碳酸钠(RSC)、总碱度和pH等进行了测定计算,分析了各碱化参数之间的关系,得出了各参数之间的相关方程。结果表明,除pH外,苏打碱土各碱化参数之间均具有极显著的相关性,各参数之间关系密切。土壤pH与ESP和SAR之间的关系变异性较大,利用pH推算该区苏打碱土碱化状况将会产生很大的不确定性。     

近代及现代黄河三角洲不同尺度地貌单元土壤盐渍化特征浅析

近、现代黄河三角洲近50%的土地为不同程度的盐渍化土。在土壤盐渍化过程中,地貌因素至观重要。地形的高低起伏,影响地面、地下径流的运动,土壤中的水分和盐分也就随之重新分配和积累。研究的目的是分析不同尺度下地貌单元之间土壤盐渍化特征差异及原因。为此,利用2002年5月23日到29日对近、现代黄河三角洲野外考察、GPS定点和土壤采样分析所得数据,对6个表征土壤盐渍化特征的参数(土壤的全盐量、pH值、有机质、Cl-/SO42-、HCO3-/(Cl- SO42-)、(K Na )/(Ca2 Mg2 ))进行统计分析,并进行多个独立样本的非参数检验(Kruskal-WallisTest和MedianTest),检验6个参数在同一尺度不同地貌单元之间是否有明显的差异,结果表明:(1)近、现代黄河三角洲土壤盐渍化程度严重,整体属于滨海氯化物型盐渍土类型,有机质相对缺乏,土壤偏碱性。随土层深度增加(0cm￣10cm、10cm￣30cm、30cm￣60cm),盐渍化程度逐渐减轻;(2)同一尺度下不同地貌单元之间土壤盐渍化特征存在差异。一般地,随尺度变小(从一级到四级地貌单元),土壤盐渍化特征差异越来越明显,存在差异的参数也逐渐增加。一级地貌单元只有pH值明显不同,从二级地貌单元到四级地貌单元,3个土层土壤的全盐量随不同的地貌单元而有明显的差别,且随着土层深度的增加,HCO3-/(Cl- SO42-)和(K Na )/(Ca2 Mg2 )也变得明显不同。这也说明不同地貌单元下盐分组成及离子比例、积盐、脱盐过程存在差异,且随土层深度增加差异越大。     

不同灌溉方式对土壤次生盐渍化的影响

主要研究了松嫩平原地区的灌溉方式、土壤水盐运动状况、环境条件以及人为因素等,对土壤次生盐渍化的形成,提出预防与防治具有重要的意义。为了防止土壤次生盐渍化,良好的排水系统是非常重要的,它可以降低地下水位和排出土壤盐分,做到灌排配套。     

有机物料改良盐碱土的效果研究

采用盆栽试验方法 ,研究了在盐碱土中分别施入不同比例草炭和风化煤的改良效果及对作物的增产效果。结果表明 :草炭和风化煤增加了土壤速效养分 ,降低了土壤的 pH值、ESP、Na+/K+、Na+/Ca2 +和Na+/Mg2 +,增强了土壤的团聚性 ,改善了盐碱土的养分供应状况 ,增加了作物的产量。各处理中以施入 4%草炭的增产效果较好。     

宜兴市温室土壤理化性质的调查和分析

对宜兴市的温室和露天土壤的理化性质(包括pH,电导率,各种水溶性离子的含量以及全盐量)进行调查测定,结果表明:宜兴市温室土壤pH值0-20 cm土层比深层低,有酸化趋势;土壤全盐量显著高于露天土壤,盐分已明显在0～20cm土层富集,表层土壤全盐含量均在2.00 g/kg以上;在盐分的离子组成中,阳离子以Ca2 为主,平均占全盐总量的14%,阴离子以NO3-和SO42-为主,分别平均占全盐总量的56%和23%.说明该地区温室土壤己达到中度盐渍化水平.     

土壤盐渍化遥感应用研究进展

对基于不同遥感影像数据源的盐碱地监测、盐碱地信息自动化提取方法和盐碱地监测方法等方面的研究进展进行了综述。