研究论文 正式出版 版本 1 Vol 11 (1) : 81-89 2020
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陕北不同沟道土地土壤盐碱化现状及影响因素
Situation and impact factors of soil salinization in different dammed farmlands in the valley area of the Northern Shaanxi Province
: 2019 - 03 - 11
: 2019 - 07 - 08
: 2019 - 07 - 14
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摘要&关键词
摘要:沟道土地是陕北黄土丘陵沟壑区重要的土地资源。然而,当前对黄土高原沟道土地的盐碱化问题关注不够,对盐碱化的现状、发生机制和防治措施也缺乏深入系统的认识,知识储备不能满足生产实际的需要。以陕北黄土丘陵沟壑区自然和人为形成的沟道土地为研究对象,分别是延安顾屯新造耕地(治沟造地)、延川马家湾淤地坝土地和子洲黄土洼天然古聚湫土地,在这些流域内沿沟道采集土壤样品,测定土壤的电导率(EC)、pH值、含水量及粒度,分析土壤盐碱化的现状和影响因子。结果表明:马家湾淤地坝土地盐碱化最为严重,流域中游至上游均出现程度不等的盐碱化;顾屯新造地上游出现盐碱化,盐碱化程度较马家湾轻,而黄土洼古聚湫全流域未出现盐碱化。地下水位埋深是沟道土地发生盐碱化的主要影响因素,因此陕北沟道土地盐碱化防治应着力控制地下水位,建设良好的排水系统,加快排水。
关键词:治沟造地;淤地坝;古聚湫;地下水位;土壤盐碱化;黄土高原
Abstract & Keywords
Abstract: Background, aim, and scope Soil salinization is one of the most important types of land degradation, which receives highly attention by scientists and governments around the world. During the past 50 years, China has achieved great success in controlling soil salinization, while it is still a serious problem of land degradation in many areas of China, e.g. the Yellow River Basin. The Chinese Loess Plateau (CLP) locates the middle reaches of the Yellow River, where is an area prone to soil salinization with low precipitation, high evaporation, and alkaline soil. The valley area on the CLP is the place where has high risk of soil salinization being high groundwater table and poor drainage system. However, the valley on the CLP has a large area of farmlands, e.g. the dammed farmlands formed through human and natural factors in the hilly-gully regions of the Northern Shaanxi Province. Currently, we lack a comprehensive understanding of the situation, mechanisms and prevention measures of soil salinization in these dammed farmlands in the valley of the loess hilly-gully regions, which has substantially constrained the knowledge demands of agricultural practice on the CLP. Materials and methods In this study, three kinds of dammed farmlands in the valley area of the Northern Shaanxi Province were selected to examine the situation and impact factors of soil salinization. The dammed farmlands included the man-made farmlands in the valley of the Gutun watershed, Yan’an City (formed through gully land consolidation), the semi-natural farmlands behind the fulfilled check dams in the valley of the Majiawan watershed, Yanchuan County, and the natural farmlands formed through the ancient landslide-dammed lake in the valley of the Huangtuwa watershed, Zizhou County. Soil samples were collected in the three kinds of farmlands, and soil electric conductivity (EC), pH value, soil moisture and soil texture were measured. Moreover, based on the measured soil moisture content in the profile, groundwater levels in the three kinds of farmlands were estimated through an empirical equation. Results According to the determined soil physical and chemical parameters and the estimated groundwater levels, the situation and impact factors of soil salinization in the three kinds of farmlands were evaluated. Results showed that: (1) soil salinization both occurred in the Gutun and Majiawan watersheds, and Majiawan showed the most serious situation of soil salinization among the three valley sites; (2) in the Guntun watershed, soil salinization occurred in the upper reaches of the valley; while in the Majiawan watershed, soil salinization extended to the middle reaches of the valley; (3) in the Huangtuwa watershed, no soil salinization was found in the valley farmlands. Discussion Majiawan watershed showed the most serious situation of soil salinization due to a shallow water table, where profile soil moisture demonstrated the highest average content (28.4%) among the three kinds of farmlands. Moreover, the estimated average water table depth was 1.23 m, which demonstrated a very shallow groundwater level. In the Guntun watershed, the average groundwater level was 2.85 m and the middle and lower reaches of the valley showed a relatively deep groundwater table; while in the upper reaches of the valley, the groundwater table was shallow and many farmlands showed a groundwater table less than 1 m . Therefore, obvious soil salinization occurred in the upper reaches of the valley in the Gutun watershed. The ancient landslide-dammed farmlands in the valley of the Huangtuwa watershed demonstrated no salinization mostly being a deep groundwater table. The Huangtuwa watershed locates in a high platform, and the estimated groundwater level was 4.77 m. Moreover, the profile soil moisture content showed a moderate level and demonstrated a decreasing trend with the increase of soil depth, which indicates that soil water is well drained at the bottom of the farmland. Therefore, no soil salinization occurred in the valley farmlands. Conclusions Shallow groundwater table was the critical reason of soil salinization in the dammed farmlands in the valley of the loess hilly-gully regions of the Northern Shaanxi Province. Recommendations and perspectives Strengthening the drainage system and suppressing the groundwater table are the core issues in deal with the problems of soil salinization in the dammed farmland in the valley of the Northern Shaanxi Province. The results of this study can provide scientific basis for soil salinization control on the CLP.
Keywords: gully land consolidation; check dam; ancient landslide-dammed lake; groundwater table; soil salinization; Chinese Loess Plateau
土地退化是一个全球性问题,在干旱半干旱区尤为严重(Li et al,2016)。土壤盐碱化是土地退化的一种重要形式,受到世界各国科学家和政府部门的重视(Clark et al,2007)。据统计,全球受盐碱化影响的土地面积大约为9.55亿公顷,其中0.77亿公顷正在遭受土壤次生盐碱化的影响(Metternicht and Zinck,2003)。土壤盐碱化导致农作物产量低下,土地资源无法可持续利用(Abbas et al,2013)。我国盐碱土总面积约为3600万公顷,其中盐渍化耕地的面积达到921万公顷,约占全国耕地总面积的7%(全国土壤普查办公室,1998)。自20世纪50年代以来,我国政府和科学家投入大量的人力和物力开展盐碱化治理,取得了巨大的成就,如华北平原地区盐碱化土地面积大幅降低(李保国等,2003)。然而,我国土地盐碱化问题依然严峻,尤其是华北、西北和东北地区,因此迫切需要开展盐碱化的成因、机制和治理措施研究,提高我国盐碱化土地的开发潜力。
黄土高原由于降雨量低(150—800 mm)、蒸发量高(900—1300 mm)、黄土呈碱性(pH均值为8.5)等特征,使得该地区土地容易发生盐碱化(李英能,1999;Liu et al,2013;Peng et al,2017)。尤其是沟道内土地,地下水位高,排水不畅,加之缺乏良好的排水设施,发生盐碱化的风险非常高。当前,黄土高原保存有大量的沟道土地。例如:自1950年以来,黄土高原大规模建设的淤地坝淤成耕地达30多万亩(Wang et al,2011;Jin et al,2012)。这些沟道土地水肥条件好,生产力约是坡耕地的5—10倍,因此素有“宁种一亩沟,不种十亩坡”、“打坝如修仓,拦泥如积粮;村有百亩坝,再旱也不怕”的说法,由此可见沟道土地在黄土高原农业生产中的重要性。2013年以来,在国土资源部和财政部的支持下,延安市试点实施了治沟造地工程(2013—2017年),项目涉及延安市13个县区,目前已完成治沟造地50万亩,总投资48亿元。然而,野外考察发现,一些新造耕地出现了不同程度的盐碱化,甚至影响到正常耕种。此外,对淤地坝的考察也发现,部分淤地坝内的耕地也出现了盐碱化现象,导致土地生产力下降。因此,如何科学有效地防治沟道土地的盐碱化,提高沟道土地的利用效率,是陕北黄土丘陵沟壑区农业发展的重要任务。
当前,国内学者针对黄土高原河谷平原区土壤盐碱化的现状、机制和治理措施开展了大量的研究,取得了突出的成果,如宁夏灌区、内蒙古河套地区、陕西渭南地区等(王全九和王文焰,1993;康跃虎等,2012;管孝艳等,2012;樊会敏,2017),但对黄土高原沟道土地盐碱化的研究关注不够。早期日本学者联合中国科学院水保所科研人员,对淤地坝土地盐碱化的发生机制进行了初步研究,发现淤地坝流域上游地区容易发生盐碱化,地下水抬升是导致土壤发生盐碱化的主要原因(Li et al,2012;Shimizu et al,2014;Shimizu,2014)。最近,中国科学院地球环境所科研人员对治沟造地流域土壤盐碱化的现状和机制进行了研究,发现了和淤地坝类似的现象(Jin et al,2019)。然而,当前对黄土高原沟道土地的盐碱化现状、发生机制和治理措施的研究还远远不够,知识储备不能满足生产实际的需要,因此迫切需要加强相关方面的研究,促进黄土丘陵沟壑区农业的可持续发展。
本研究通过选择陕北三个不同地点的沟道土地,分别为延安顾屯治沟造地工程新造的土地、马家湾淤地坝土地和黄土洼天然古聚湫土地,对各沟道土地的土壤理化性质(土壤电导率、pH、含水量、粒度)进行测试分析,旨在初步了解陕北黄土高原不同类型沟道土地的盐碱化现状、发生机制及控制因素,为黄土高原沟道土地盐碱化的治理提供理论支撑。
1   材料与方法
1.1   研究区概况
研究区位于陕北黄土丘陵沟壑区,由南向北依次选择了三种典型的沟道土地,分别为延安市甘谷驿镇顾屯流域治沟造地土地、子长县贾家坪镇马家湾淤地坝土地和子洲县裴家湾镇黄土洼天然聚湫土地(图1)。顾屯流域位于陕西省宝塔区甘谷驿镇境内(36°45′16″—36°50′24″N,109°46′18ʺ—109°51′05″E),流域总面积约24.35 km2;该区域黄绵土是主要的土壤类型;多年平均气温10.3℃,年平均降水量495 mm(1980—2007)(余云龙等,2017)。顾屯流域治沟造地工程开始于2011年,2014年完工。马家湾位于延川县贾家坪镇马家湾村(36°59′56.18″—37°0′45.07″N,109°57′42.98″—109°58′45.12″E);该区域多年平均降水量458.3 mm,年均温10.6℃,平均日照时数2528.4小时,光热充足,年均无霜期183天(延川县国土资源局,2017-12-10)。马家湾淤地坝于上世纪50年代修建淤满后进行耕种。黄土洼天然古聚湫位于陕北子洲县裴家湾镇黄土坬村(37°18′39.64″—37°19′10.12″N,110°00′0.54″—110°00′27.83″E),于明代隆庆三年(公元1569年)山体滑坡堵塞沟谷泥沙淤积形成(龙翼等,2009);黄土洼古聚湫淤地面积为17.2公顷(安锁堂,2004),多年平均降水量435.43 mm,1953—2017年气象数据显示该区年均温为9.98℃(中国气象数据网,http://www.nmic.cn/)。各研究区主要种植的农作物为玉米。


图1   陕北三种典型沟道土地地理位置
Fig.1 Three kinds of dammed farmlands in the valley area of the Northern Shaanxi Province
a:顾屯治沟造地的新造耕地,b:马家湾淤地坝土地,c:黄土洼天然古聚湫土地。 a: farmlands formed through gully land consolidation in the valley of the Gutun watershed, b: farmlands formed through fulfilled sedimentation behind the check dams in the valley of the Majiawan watershed, c: farmlands formed through fulfilled sedimentation in ancient landslide-dammed lake in the valley of the Huangtuwa watershed.
1.2   土壤样品采集与前处理
在三个不同的沟道流域,自下游至上游利用土钻法和挖掘土壤剖面法采取土壤样品,包括24个土钻点(5 cm直径)和11个2 m深度的土壤剖面点(图1),共采集土壤样品476个。顾屯治沟造地流域包括9个土钻点,3个剖面点,142个土壤样品;马家湾淤地坝包括7个土钻点,4个剖面点,94个土壤样品;黄土洼古聚湫包括8个土钻点,4个剖面点,240个土壤样品。采样的层距间隔方法为0—100 cm土层每间隔10 cm取一个土壤样品,100—200 cm土层每间隔20 cm取一个土壤样品。所有土壤样品的采集工作于2018年5月中旬完成。土壤样品采集后装进密封袋,编号后带回实验室进行前处理。采集的土壤样品均自然风干,玛瑙研磨后过2 mm筛待测。
1.3   土壤样品理化指标分析
土壤样品测定的理化指标包括土壤电导率、pH值、含水量和粒度。土壤电导率采用DDS-307型电导率仪进行测定,用于指示土壤盐碱化水平;土壤pH值按水土比2.5∶1电位法测定,每个样品重复测3次,取平均值;土壤含水量使用烘干法进行测定;土壤粒度采用MAZ3000激光粒度仪测定。
根据鲍士旦(1999)在《土壤农化分析》一书中描述的土壤电导率与盐分的关系:土壤电导率0—2000 μS·cm-1,指示为非盐渍化土;土壤电导率2000—4000 μS·cm-1,指示为轻度盐渍化土;土壤电导率4000—8000 μS·cm-1,指示为中度盐渍化土;土壤电导率8000—16000 μS·cm-1,指示为重度盐渍土;土壤电导率>16000 μS·cm-1,指示为极重度盐渍化土。
1.4   地下水位估算方法
地下水径流畅通,地下水位低的地区土壤含盐量低;反之,土壤容易发生盐碱化(宋长春和邓伟,2000)。土壤含水量高低可表征地下水位深浅状况:土壤剖面含水量高,指示地下水位较浅;含水量低,指示地下水位深(马龙和刘廷玺,2007;刘景利等,2008)。前人研究发现西北地区土壤含水量与地下水位埋深存在以下指数关系式(张惠昌,1992;张长春等,2003),根据该指数关系可估算得到三个研究区的地下水位深度:
\[H=-\frac{\mathrm{l}\mathrm{n}\frac{\theta }{35.726}}{0.185}\]
式中=中:H表示地下水位的埋深(m);θ表示土壤剖面平均含水量(%)。
2   研究结果
2.1   陕北三种不同沟道土地土壤盐碱化现状
2.1.1   顾屯流域新造耕地土壤盐碱化现状
通过对顾屯流域土壤电导率进行测试和分析发现,新造地0—20 cm土层深度土壤电导率值在356—3380 μS·cm-1波动(图2)。流域不同部位土壤电导率差异较大,反映的盐碱化程度也有所不同。流域中、下游土壤电导率较低,均在1000 μS·cm-1以下,指示土壤未发生盐碱化。和流域下游相比,流域上游土壤电导率较高,指示土壤出现了盐碱化。例如位于流域上游的#8和#9采样点,土壤电导率分别为3380 μS·cm-1和2180 μS·cm-1,均高于2000 μS·cm-1,指示土壤存在明显的盐碱化趋势。


图2   顾屯新造地0—20 cm土层深度电导率分布
Fig.2 Spatial distribution of soil electric conductivity at a depth of 0—20 cm in the farmlands formed through gully land consolidation in the valley of the Gutun watershed
2.1.2   马家湾流域淤地坝土地土壤盐碱化现状
从马家湾流域土壤电导率可以看出,流域上游至下游土壤电导率值波动较大,总体在416—5385 μS·cm-1变化(图3)。流域下游电导率最高为1505 μS·cm-1,指示土壤未发生盐碱化。与下游相比,流域中上游电导率显著高于下游(p<0.05),中游4号采样点电导率高达5385 μS·cm-1,表明马家湾流域中游土壤盐碱化最为严重;上游土壤电导率也较高,指示土壤也发生了盐碱化。


图3   马家湾0—20 cm土层深度电导率分布
Fig.3 Spatial distribution of soil electric conductivity at a depth of 0—20 cm in the farmlands formed through fulfilled sedimentation behind the check dams in the valley of the Majiawan watershed
2.1.3   黄土洼天然古聚湫土地土壤盐碱化现状
由土壤电导率数据(图4)可知,黄土洼天然古聚湫土地未出现盐碱化,全流域土壤电导率在304—1614 μS·cm-1波动,平均值为588.13 μS·cm-1。流域内仅一个采样点的表层土壤(0—20 cm)电导率值较高,为1614 μS·cm-1,但未超过2000 μS·cm-1,其他采样点土壤电导率值均低于1000 μS·cm-1


图4   黄土洼0—20 cm土层深度电导率分布
Fig.4 Spatial distribution of soil electric conductivity at a depth of 0—20 cm in the farmlands formed through fulfilled sedimentation behind the ancient landslide-dammed lake in the valley of the Huangtuwa watershed
Fig.4 Spatial distribution of soil electric conductivity at a depth of 0—20 cm in the farmlands formed through fulfilled sedimentation behind the ancient landslide-dammed lake in the valley of the Huangtuwa watershed
2.1.4   三种不同沟道土地土壤盐度的剖面分布特征
从陕北三种不同沟道土地土壤电导率的剖面分布特征来看,三个研究区平均土壤电导率大小为马家湾(1190.44 μS·cm-1)>顾屯(588.2 μS·cm-1)>黄土洼(453.11 μS·cm-1)(图5)。从统计结果看,三种不同沟道土地土壤电导率存在显著差异,其中马家湾显著高于顾屯和黄土洼(p<0.05)。马家湾土壤电导率随土层深度增加而减小,0—20 cm土层电导率值最高,表明表层土壤存在明显的盐分聚集作用;而顾屯和黄土洼土壤电导率总体在600 μS·cm-1左右波动,随土层深度的变化波动不大。


图5   陕北不同沟道0—100 cm土壤电导率分布特征
Fig.5 Vertical distribution characteristics of soil electric conductivity at a depth of 0—100 cm in the three different kinds of farmlands in the valleys of Northern Shaanxi Province
2.2   陕北三种不同沟道土地土壤含水量、地下水位、土壤粒度和pH特征
(1)土壤含水量和地下水位
三种不同沟道土地0—200 cm土层含水量大小关系为:马家湾(均值为28.4%)>顾屯(均值为21.1%)>黄土洼(均值为14.8%)。顾屯和马家湾土壤含水量随剖面深度增加而增加,而黄土洼土壤含水量随土层深度增加而逐步降低(图6)。通过土壤含水量估算的地下水位深度得知,顾屯的平均地下水位深度约为2.85 m,马家湾平均地下水位深度约为1.23 m,黄土洼地下水位深度约为4.77 m。由此可见,顾屯新造地和马家湾淤地坝土地地下水位深度较浅(<3 m),容易发生土壤盐碱化,因此表层土壤呈现较高的电导率值;而黄土洼天然古聚湫地下水位较深,并且随着剖面深度的加深,土壤含水量降低,表明该区域土壤排水较好,土壤不易发生盐碱化,因此表层土壤呈现较低的电导率值。


图6   陕北不同沟道0—200 cm土壤含水量分布特征
Fig.6 Vertical distribution characteristics of soil moisture at a depth of 0—200 cm in the three different kinds of farmlands in the valleys of Northern Shaanxi Province
(2)土壤粒度
从土壤粒度分布可见,顾屯和马家湾粉粒(0.002—0.05 mm)占比较大,分别为66.95%和67.45%,砂粒(0.05—2 mm)占比低,土壤质地较黄土洼黏重;而黄土洼粉粒占比为58.91%,砂粒占比为39.01%(表1)。
表1   陕北不同沟道土地土壤机械组成
采样点
Sampling site
土壤粒度分布 Soil grain size distribution /%
砂粒 Sand
0.05—2 mm
粉粒 Silt
0.002—0.05 mm
黏粒 Clay
<0.002 mm
顾屯 Gutun29.8666.953.19
马家湾 Majiawan29.6367.452.92
黄土洼 Huangtuwa39.0158.912.08
粒级据美国农部制命名。
Classification of soil grain size according to the US Department of Agriculture.
(3)土壤pH值
通过对比三种不同沟道土地pH发现,0—40 cm土层,顾屯新造地土壤pH均值(8.22)>马家湾(8.07)>黄土洼(7.81)(图7)。由于0—40 cm为农作物的根系分布密集区,根系对土壤存在酸化作用。黄土洼农业种植时间最长,酸化时间最长,因此显现出最低的土壤pH值;马家湾作物种植时间次之,土壤pH值居中;而顾屯为新造耕地,作物种植时间短,对土壤的酸化作用最弱,加上新造耕地为取自山脚边坡的碱性黄土,其本身pH值较高,因此呈现最高的土壤pH值。40—200 cm土壤,黄土洼和顾屯土壤pH值变化较小,而马家湾土壤pH值呈现一个明显升高的过程,尤其是在40—90 cm土层深度。深部土壤的pH均值,马家湾(8.69)>顾屯(8.62)>黄土洼(8.15),表明马家湾高的地下水位浸泡土壤,使得土壤pH升高。


图7   陕北不同沟道0—200 cm土壤pH分布特征
Fig.7 Vertical distribution characteristics of soil pH in the three kinds of farmlands at a depth of 0—200 cm in the valleys of Northern Shaanxi Province
3   讨论
顾屯流域和马家湾流域上游地区均出现了不同程度的盐碱化,但马家湾流域土壤盐碱化进一步扩展到中游地区,并且流域中游盐碱化最为严重,而黄土洼天然古聚湫整条流域未出现盐碱化现象。从土壤粒度来看,顾屯和马家湾粉粒和黏粒占比较大,土壤质地较黄土洼黏重。顾屯和马家湾土壤质地较黏重也说明这两条沟道小流域土壤持水性较黄土洼好,但也导致土壤的导水性能下降,不利于土壤排水,这也是导致土壤发生盐碱化的一个因素。实际上,马家湾流域严重的土壤盐碱化,与其较低的地下水位密切相关。从马家湾流域土壤含水量来看,各采样点的平均土壤含水量在三种沟道土地中最高(28.4%),并且随着坡面深度的增加,土壤含水量逐步升高,很多点位土壤含水量超过40%,达到饱和水平,表明地下水对土壤含水量产生了较强的影响(图6)。此外,马家湾流域由土壤含水量估算的地下水位平均深度为1.23 m,呈现非常浅的地下水埋深,这与野外采样过程中的实际观察是对应的。因此,高的地下水位是马家湾流域产生严重盐碱化的主要原因。此外,马家湾流域表层(0—20 cm)盐碱土土壤pH均值为7.63,呈现相对较低的pH值水平,表明该流域主要为土壤盐化。从土壤电导率来看,顾屯流域新造地土壤盐碱化程度低于马家湾,平均地下水位约为2.85 m。此外,从土壤含水量的剖面分布来看,和马家湾流域相似,随着土层深度的增加,土壤含水量逐步升高,部分点位土壤含水量超过35%。前人研究表明:如果地下水位深度<3 m,地下水可通过毛细管吸力上升至地表;地下水位下降后,地下水中的盐分离子在地表聚集,导致表层土壤发生盐碱化(方生和陈秀玲,2005;缑倩倩等,2011)。因此,顾屯流域存在较大的盐碱化风险。此外,顾屯上游地区出现盐碱化的表层土壤pH均值为9.09,表明该流域上游主要为土壤碱化。黄土洼天然古聚湫的地下水位最深,平均为4.77 m;并且从土壤含水量的剖面分布来看,随着土层深度的增加,土壤含水量逐步降低,表明底部排水良好,2 m土层深度未受到地下水的影响,因此整条流域未发生盐碱化现象。由此可见,地下水位深度是决定沟道土地是否发生盐碱化的主要原因,但不同的沟道土地,出现盐碱化的特征不同,有可能发生盐化(马家湾),也有可能发生碱化(顾屯)。
从实际考察来看,顾屯流域新造地和马家湾流域淤地坝土地较低的地下水位,主要由流域排水不畅导致,尤其是流域上游地区。在流域上游,由于地形狭窄,老地形较高,老地形上自然淤积(淤地坝)或人为覆盖(治沟造地)的土层较薄,加之水库或淤地坝的阻挡作用,使得该区域的地下水位非常浅,极易发生盐碱化。以马家湾为例,自上世纪50年代淤地坝修建后,由于沟道排水不畅,地下水位高,使得坝内土地盐碱化严重,800多亩坝地中450亩为盐碱地,无法耕种,虽经多期改造,仍未得到明显改善(王允升,1988)。此外,顾屯上游出现的明显盐碱化,还与水库漏水或渗水导致的地下水位升高有关,如#8和#9采样点,均位于顾屯上游靠近5号水库的位置。根据课题组前期的研究结果,发现5号水库可能存在明显的漏水或渗水现象,导致下游区域出现明显的盐碱化,表层土壤可溶性盐含量均高于2 g·kg-1(Jin et al,2019)。然而,值得注意的是,黄土洼天然古聚湫,于明代隆庆三年(公元1569年)由山体滑坡堵塞流域出口自然淤积形成(龙翼等,2009),距今已有450年历史。该流域无任何排水设施,但地下水位高,底部排水良好,因此没有出现任何盐碱化现象,这可能与该区域的局部地形有关。从地形来看,黄土洼位于沟谷尾部的高台上,虽然从流域四周汇水,但由于地形相对较高,汇聚的水分较易从底部渗透排走,因此使得古聚湫的地下水位较高,从而维持了黄土洼古聚湫良好的水肥条件和高的土地生产力。综上所述,陕北沟道土地的盐碱化防治,加强排水、控制地下水位的上升是关键。例如:马家湾流域排水渠坍塌淤堵严重,排水不畅,应及时对沟渠进行清淤,畅通地表径流,降低地下水位;而顾屯流域应加强水库下游横向排水沟(截沟)的建设,阻截壤中流和水库的渗透,调控地下水位。
4   结论
研究选择的三个流域沟道土地,两个流域上游(顾屯治沟造地和马家湾淤地坝土地)出现了不同程度的盐碱化,其中马家湾流域盐碱化最为严重,进一步扩展到中游地区。浅的地下水位是导致陕北黄土丘陵沟壑区沟道土地发生盐碱化的主要原因,因此加强沟道排水、降低沟道地下水位,是防治沟道土地盐碱化的关键。
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稿件与作者信息
陈淑敏
CHEN Shumin
金钊
JIN Zhao
张晶
ZHANG Jing
褚光琛
CHU Guangchen
桑维峻
SANG Weijun
林杭生
LIN Hangsheng
出版历史
出版时间: 2019年7月14日 (版本1
参考文献列表中查看
地球环境学报
Journal of Earth Environment