近20年黄土高原不同地貌类型区植被覆盖变化及原因分析

 植被覆盖是控制或加速水土流失最敏感的因子。以黄土高原为研究对象,利用1988—2005年NOAA/AVHRR植被指数(NDVI)月最大值合成的7月份资料分析不同地貌类型区NDVI值的时空变化规律,并通过计算NDVI值与同期降雨量的相关系数分析降雨量对不同地貌类型区NDVI的影响,探讨黄土高原典型区县退耕还林政策对NDVI的影响。结果表明:1)黄土高原整体植被覆盖度较低,NDVI多年平均值为0.29,平原区、石质山地、黄土低山、黄土塬及其周围地区NDVI值在0.30～0.40之间,梁、卯、片沙黄土丘陵区NDVI值在0.18～0.22之间,其余地貌类型区均低于0.15;2)1998年之后8年NDVI的平均值比前10年的NDVI平均值略有增加,整体增加幅度为4.5%,不同地貌类型区NDVI值变化表现出明显的地带性,呈东北西南走向,黄土高原主体部分中的黄土塬、黄土破碎塬、梁状黄土丘陵均增加10%以上,峁状黄土丘陵、风蚀沙化丘陵略有减少,减少的区域没有增加的区域大;3)除石质山地、黄土低山和平原地区外,其他地貌类型区7月最大NDVI值与5—7月累计降雨量存在很好的相关性,R2在0.60以上;4)地处梁状黄土丘陵区的吴旗县,1998年后形成了一个明显的以县为边界的NDVI值增长区,增幅达40%,远远高于该地貌类型区的平均增长值14%。初步结论:除平原地区外,降雨量决定黄土高原植被覆盖度的空间分布,1998年前后黄土高原植被变化的决定因素是降雨量;吴旗县的实例证明,只要水土保持资金到位、林草建设因地制宜、管理保护措施完善,退耕还林政策将会对植被覆盖度的增加起到积极作用。     

富县水土流失危害及其防治

水土流失是黄土高原普遍存在的严重问题。富县位于陕北黄土高原沟壑区向黄土丘陵沟壑区的过渡带,塬面、丘陵、山地、河谷阶地等黄土高原区的主要地貌类型均有,是这类地区水土保持重点县之一。摸清该县水土流失状况,不仅为搞好全县农业区划、防治水土流失提供依据,而且对了解整个黄土高原水土流失的类型、分布规律、危害程度、发展趋势、防治途径也是有益的。为此,我们结合土壤普查,对富县水土流失状况作了全面调查,绘制了1/50,000的土壤侵蚀图。     

汾河流域土壤重金属垂直分布规律及地域差异

山西汾河流域按土属采土样１７４０个，测定镍、铬、铅、锌、砷、铜、汞、镉八种元素的含量。探讨了垂直分布及各地形部位贡献大小和地域差异。在中高山地、山地、低山丘陵、丘陵阶地、二级阶地和平原盆地六个地形部位中，土壤重金属元素含量均未超过土壤污染起始值。各元素不同地形部位贡献大小为：中高山地汞大、山地铜大、低山丘陵铬大，丘陵阶地铅、镍、铜大，二级阶地汞大、锌小，平原盆地镉、汞大、铜小。故二级阶地和平原盆地应施用铜、锌微肥和防止汞、镉污染。地域差异研究表明：东西两山山地土壤多数元素含量差异不显著，利用较为一致。南北两盆地污染重点在太原盆地。上述研究结果为土壤环境质量评价、土壤污染防治和预测，工矿企业合理布局，农业生产结构调整提供了科学依据。     

黄土的物质成分和结构与水土保持的关系

黄土是我国有特色的第四纪沉积物。黄土在中国北方的分布,大致为北纬30—40°的范围。其中以黄河中游地区分布最为广泛,构成了切割程度不一的黄土高原。黄土在黄河中游地区的分布面积约为275,600平方公里,占该区总面积的40%以上。黄土高原是一个遭受较强烈侵蚀的地区,加之黄土本身的性质比较疏松,具大孔隙和垂直节理发育等组织结构特征,使这里的水土流失比较严重。解决西北黄土高原水土流失问题,对实现我国农业现代化具有重大意义。     

黄土高原新近纪红黏土磁性特征研究

黄土高原第四纪黄土之下,埋藏着更加古老的新近纪红黏土。以黄土高原甘肃西峰剖面和灵台剖面为例,采集了两个剖面第四纪黄土和古土壤与新近纪红黏土典型样品,比较了各自风化强度和磁性特征的差异。结果表明,新近纪红黏土样品的风化强度与第四纪古土壤较为接近,远强于第四纪黄土;但新近纪红黏土磁化率显著减弱,在西峰剖面平均只有古土壤的1/5、黄土的1/2;在灵台剖面平均亦不到古土壤的1/2,并小于黄土。两剖面黄土、古土壤与新近纪红黏土磁化率与有机质和活性铁含量呈显著正相关,说明有机质含量与铁活化程度对磁性矿物的含量有显著影响。因此,新近纪红黏土磁性的减弱,可能由于沉积年代久,有机质含量减少,氧化铁矿物老化,磁赤铁矿转化成赤铁矿;也有可能与地下水活动,导致磁性矿物的溶蚀有关。有关机理仍需作进一步研究。     

前言

黄河因其多沙多灾闻名于世,泥沙多则为淤积的主要病症。黄土高原的水土流失又是黄河泥沙的根源。现代黄土高原所呈现的千沟万壑侵蚀地貌,尤其在汛期暴雨情况下,黄土高原特殊的地形、降雨及黄土易蚀特性等特点,更使人们慑於黄河洪水泥沙滚滚不可抗拒的威力。一些研究者提出以下看法:黄土的侵蚀、搬运和沉积过程基本上是一个物理风化为主的机械过程,不应把黄河看成是生态破坏的象征,黄河携带大量泥沙是一种自然环境地质现象,与太阳黑子活动周期密切相关;构造抬升和气候因素在黄土侵蚀和沟谷发育中起重要作用;根据安塞县沟谷侵蚀的发育,黄土高原现代侵蚀以自然侵蚀为主,约占总侵蚀量的70%。     

福建农地基本特征及其水土保持措施探析

福建山多平地少,山地和丘陵占全省土地总面积的85%以上,平原面积很小,仅占10%左右,因此福建的农地多为利用山地丘陵的坡面种植农作物而形成的.由于我省山地丘陵的坡度都比较大,15°以上的约占82.49%,25°以上的约占49.39%,极易造成水土流失,因此农地水土保持开展的成功与否将直接影响到我省农业的发展.     

陕西省特大型滑坡空间分布规律与类型划分

特大型滑坡空间分布规律及其类型划分是研究其形成机理、致灾模式与风险减缓对策的重要基础。通过遥感解译、野外调查与解剖勘查等手段,查明陕西省特大型滑坡空间上具有明显的分布规律:在地貌上主要分布于关中盆地黄土塬边44处,其次是黄土梁峁、丘陵区22处,秦岭北坡6处,汉中盆地中低山区6处;在构造单元上分布于包括秦岭北坡断裂带在内的关中断陷盆地72处,汉中断陷盆地6处;在斜坡结构类型上,主要分布于黄土+泥岩型斜坡41处,其次为黄土+基岩型斜坡11处、黄土+红黏土型斜坡9处。特大型滑坡在空间分布上受活动断裂、地貌单元与斜坡结构类型的控制,不同区域发育特大型滑坡类型不同,特大型滑坡类型划分为宝鸡黄土塬边黄土—泥岩顺层型、灞桥白鹿塬边黄土—红黏土逆层型、蓝田横岭地区黄土—红黏土接触面型、关中盆地渭北地区黄土—基岩接触面型、陇县北部及韩城黄土梁峁区岩土混合型以及秦岭北坡与陕南“勉略宁”地区的堆积层型、顺向或块状岩质型滑坡等。     

地形气候对浙江丘陵山地“立体农业”布局的影响

<正> 浙江200米以上的丘陵山地(下简称山地)面积占全省陆地面积的70.4％,主峰海拔多在1100-1900米之间。山系可分为平行的三支,即:北支,从怀玉山经黄山入浙成天目山;中支,仙霞岭经天台山入海成舟山群岛;南支,洞宫山-雁荡山-括苍山。山系之间和内部,错落着众多盆地、台地、湖泊和水库。地形之差异会影响光、热、水、风等的局地分布,从而影响山地“立体农业”的布局。本文拟探讨:地形气候与作物气候安全栽培高度、气候安全栽培地段、气候较佳区     

黄土高原450ka BP前后荒漠草原大迁移的初步研究

根据野外调查和室内鉴定、分析 ,讨论了黄土高原 45 0kaBP前后的荒漠草原大迁移问题。资料表明 ,在地处黄土高原南缘的陕西长安少陵塬和西安白鹿塬 ,第 5层黄土形成初期有代表荒漠草原环境的石膏发育 ,指示当时黄土高原气候发生了显著的干旱化与大幅度的荒漠草原南迁 ,气候带向南迁移了约 5个纬度 ,荒漠草原和更为荒凉的环境广布于黄土高原。石膏的发育还揭示 ,在 45 0kaBP前后黄土高原气候发生了性质的转变 ,由季风气候转变为非季风气候 ,当时该区已基本不受夏季风的影响 ,并处在非季风气候的环境下。     

Physical properties and hydraulic regime of alluvial soils in floodplains of rivers in the Sikhote-Alin Mountains

The particle-size distribution, density, porosity, and water yield of soils in the floodplains in the Sikhote-Alin Mountains are characterized. The principal soil-hydrological constants are determined, and the mode of their variation upon different river discharge is shown. It is found that the vertical heterogeneity of the soil profiles’ density may be one of the reasons for the formation of a high water level in minor river basins in the Sikhote-Alin in the summer.     

Salt-affected soils of the Barguzin Depression

Factual materials on salt-affected soils in the Barguzin Depression (Buryat Republic) are generalized. A geomorphic map of the depression has been developed. The distribution of salt-affected soils and the specificity of salinization in different geomorphic regions are characterized. These soils tend to be developed within the low lacustrine–alluvial plain of the depression, on the floodplain of the Barguzin River and its tributaries. Smaller areas of salt-affected soils are found on the river terraces. They are virtually absent on ancient sandy ridged terraces (kuituns). The genesis and chemistry of soil salinization are mainly related to the discharge of slightly saline deep water along tectonic faults and fissures. An additional source of soil salinity is represented by surface water flows. The presence of permafrost preventing the leaching of salts and the cryoarid climate favoring the migration of salts toward the soil surface during the dry spring and early summer periods and during the soil freezing in the winter contribute to the soil salinization. Slightly saline hydromorphic solonchakous soils predominate among salt-affected soils of the depression; the portion of semihydromorphic saline soils is smaller. Automorphic saline soils rarely occur in the depression. Strongly saline soils— solonchaks—are widespread within lacustrine depressions around salt lakes. Soils of the soda and sulfate salinization predominate. The content of chlorides is small; their increased amounts, as well as the presence of sulfates, are indicative of the discharge of dee ground water onto the surface. The soda type of salinization is also related to the discharge of deep stratal water with further transformation of salt solutions during freeze–thaw cycles. Under anaerobic conditions, the formation of soda is favored the processes of sulfate reduction.     

Salinization dynamics in irrigated soils of the Svetloyarsk irrigation system,Volgograd oblast

On the basis of soil surveys performed by the Volgograd hydrogeological reclamation expedition in 1998 and 2006, published data, and original materials obtained by the authors, the dynamics of soil salinization within the Svetloyarsk irrigation system in Volgograd oblast during the irrigation and post-irrigation periods have been traced. It is found that high irrigation rates under conditions of poor drainage and closed drainage basins upon both shallow (within the Caspian Lowland) and relatively deep (on the Ergeni Upland) occurrence of saline groundwater and the presence of natural salts in the soils and subsoils lead to the rise in the groundwater level above the critical level and the development of secondary salinization in the previously surfacesaline, deeply saline, and even nonsaline soils. During the post-irrigation period (15–18 years) under modern climatic conditions, the groundwater level has been descending to a depth of more than 3 m, and the degree of salinity in the upper meter of light chestnut and meadow-chestnut soils has decreased owing to the leaching of salts with atmospheric precipitation.     

Closed basins and Vertisol formation in the rincon lagoon (Andalusia,Spain)

A study was made of the genetic relationship between the geomorphological phenomenon of closed basins and Vertisol formation in an area of Southern Spain.The lithology of the area, the low erosive power of the drainage system and the semi-arid climate are factors which favour the seasonal hydromorphism responsible for the evolution of original material into Vertisols.Depth dissolution of Keuper saline materials gives rise to the creation of basins, where water accumulates, forming laggons.Although El Rincón lagoon is now a closed basin, in the past it formed part of a larger lacustrine area which to a great extent gave rise to the blackening of the soils.     

大尺度流域不同地貌类型区水土保持减水效益分析

趋势分析结果显示 ,河源涧区、风沙区、丘陵区各代表流域年径流量均在 1970年前后发生一致性改变 ,即从 1970年以来开始有明显的减少趋势 ,平均减流幅度 (与 195 9～ 196 9年径流相比 )以河源涧区 (大理河 )和丘陵区 (小理河 )最大 ,分别为 36 .33%和 36 .2 1% ,风沙区 (海流兔河 )最小 (2 0 .6 1% )。减流幅度的大小是各类型区下垫面状况、水土保持措施和治理程度、降雨量变化等多种因素综合作用的结果。借助适合于黄土高原降雨 -产流特性的月水量平衡改进模型 ,计算天然状态下降雨应有的产流量与同期实测径流量求得减水效果。结果表明 ,3个地貌类型区 70年代的减水效益没有明显差异 ,而在 80年代减水效果差异显著 ,丘陵区 (小理河 ,2 4.99% ) >风沙区 (海流兔河 ,17.2 8% ) >河源涧区 (大理河 ,13.13% )。上述结论为定量评价黄土高原生态环境建设对黄河水资源及水环境演变的影响提供了数据基础。     

土壤施用有机物料后重组有机质变化规律的探讨Ⅰ.对有机无机复合及腐殖质结合形态的影响

通过在粉壤质黑钙土和粘壤质轻度盐化草甸土上进行田间、盆栽及培养试验,研究了施用各种有机物料后两年来重组有机质的变化状况.施用有机物料可以提高土壤有机质和重组有机质的含量,可以提高有机无机复合量,降低原土复合度.各种有机物料的效果并不一样,追加复合量和追加复合度均随玉米秸秆施用量的增加而提高,但复合系数却因用量的增加而降低.施用有机物料后重组有机质中各种结合形态的腐殖质在绝对含量上都明显提高,但以松结合态的增加较多,松/稳、松/紧比值提高.这种作用主要表现在施用的第一年.     

豫北第四纪沉积物的矿物特征

豫北平原属于黄淮海平原的一部分,位于太行山洪积-冲积扇以东的黄河、漳河之间,是河南新乡和安阳两地区的主要粮棉产地。豫北平原除部分地区是黄土缓丘和山前洪积冲积物外,大部分由黄河、漳河、沁河等现代河流沉积物所组成,其中沁河沉积物、黄土、次生黄土分布在豫北平原西部,漳河沉积物分布在豫北平原北部,而中部和东部则为大面积的黄河河流沉积物。为配合黄淮海平原中豫北平原的治理及南水北调工程中线的选线间题,我们曾对豫北地区各种沉积物上所发育的土壤进行分析,有关华北平原的土壤已有详细专著(熊毅等1965),本文仅就豫北平原地区土壤的矿物性质作简要讨论。     

关于浙江金华地区红壤的基层分类问题

我国长江以南的亚热带地区,多红壤分布,其中以第四纪红色粘土发育的红壤最为常见,均为主要垦殖对象。有的红壤垦殖利用情况良好,开垦后,土壤性质逐渐变好,得到稳定耕种;但是有的红壤利用很差,开垦两三年后,作物产量减低;有的红壤甚至连马尾松都长不好。红壤肥力的差别,显然受到红壤本身性状的影响,这些不同的土壤性状只有从土壤基层分类单元,才可区别出来。本文拟根据作者等在浙江金衡盆地九攀农中-带土壤详测所获得的部分结果,对本地区红壤的特性及其基层分类问题,作初步讨论。     

广东的海涂土壤

广东面临南海,岸线长而曲折,多港湾和岛屿,众多河流的来水来沙,形成沿岸大面积的海涂土壤。其土层深厚,质地不一,盐分和养分含量较高,气候条件优越,开垦利用价值很高,潮间带宜农垦面积以珠江口较大,是今后围垦种植的主要基地,适时围垦后可宜发展外向型农业;广阔的潮下带及不适宜农垦的潮间带,宜发展海水养殖业,这是今后海岸带开发利用的重要领域。并毗邻港澳、经济特区和沿海开放城市前缘,因此,积极开发利用丰富的海涂土壤资源,对促进沿海经济发展是有其重要的战略意义。     

Soils and the soil cover of the arkaim reserve (Steppe Zone of the Trans-Ural Region)

Soils of the Arkaim Reserve in the area around a unique settlement-fortress of the Bronze Age in Chelyabinsk oblast have been studied. These soils are generally typical of the entire Trans-Ural Plateau. The soil properties are characterized in detail on the basis of factual data on 170 soil pits and four soil catenas. The soil cover of the reserve is specified into six geomorphic groups: (a) denudational surfaces of the low mountains, (b) accumulative-denudational surfaces of the low mountains, (c) denudational-accumulative plain surfaces, (d) lacustrine-alluvial plain surfaces, (e) floodplain surfaces, and (f) slopes and bottoms of the local ravines and hollows. Chernozems occupy about 50% of the reserve; solonetzes and saline soils, 32%; meadow chernozems, 7%; and forest soils, 1%. The soils of the reserve are relatively thin; they have a distinct tonguing of the humus horizon and are often saline and solonetzic. The latter properties are inherited from the parent materials and are preserved in the soils for a long time under the conditions of a dry continental climate. The genetic features of the soils differ in dependence on the composition and age of the parent materials. With respect to the thickness of the soil profiles and the reserves of soil humus, the soils can be arranged into the following lithogenic sequence: the soils developed from the eluvium of igneous rocks-redeposited kaolin clay-montmorillonite-hydromica nonsaline and saline loams and clays. The content of C_org in the upper 20 cm varies from 2.5 to 5.6%, and the reserves of C_org in the layers of 0?C0.5 and 0?C1.0 m reach 57?C265 and 234?C375 t/ha, respectively. The soils of pastures subjected to overgrazing occupy two-thirds of the reserve. Their humus content is 10?C16% higher in comparison with that in the analogous plowed soils. Another characteristic feature of the humus in the soils of the pastures is its enrichment in the labile fraction (28?C40% of C_org).