黄土宽梁缓坡丘陵区次降雨对土壤水分补给效率与阈值研究

降水是干旱、半干旱地区的主要水分来源,其对土壤水分的补给直接影响到植被生长和生态系统服务的维持,但由于降雨特征和植被结构影响,有限的降水资源并未得到有效利用.研究次降雨事件对不同植被类型下土壤水分的补给效率和阈值,对于指导植被恢复、提高降水资源利用效率具有重要意义.本研究以半干旱黄土丘陵区天然荒草、小麦、红豆草、沙棘和油松5种典型植被为例,通过不同水文年降雨和土壤水分动态监测,以土层20cm土壤水分动态作为衡量降雨是否得到有效补给的判断依据,研究了次降雨事件对不同植被类型土壤水分的补给效率与阈值.结果表明:(1)降雨补给的延滞时间、补给速率和补给效率与植被类型密切相关,不同植被之间存在较大差异.(2)天然荒草土层20cm处降雨补给的延滞时间为26.4h,其次为小麦27.8h、沙棘41.8h、红豆草50.0h和油松81.8h;降雨补给速率依次为:小麦0.40mm h~(-1)、天然荒草0.30mm h~(-1)、沙棘0.17mm h~(-1)、红豆草0.14mm h~(-1)、油松0.09mm h~(-1);降雨对土壤水分补给的效率依次为:天然荒草35.1%、小麦29.2%、沙棘16.8%、红豆草11.5%、油松4.2%.(3)通过线性拟合得到不同植被具有土壤水分补给作用的降雨有效补给阈值为:小麦6.8mm、天然荒草10.5mm、沙棘20.5mm、红豆草22.6mm、油松26.4mm,由此可知天然荒草地土壤水分对降雨响应较为敏感,油松林地土壤水分则难以得到降水有效补充.     

流域水资源初始产权界定初探一以黑河流域中游为例

随着水资源短缺程度的加剧,可交易水权制度逐渐成为当今世界水资源管理制度发展的新方向.水资源初始产权是水资源管理的基础和前提.在干旱区内陆河流域,产权初始配置要在生态环境可持续的前提下,坚持公平、效益相结合的分配目标和配置原则.通过建立初始水权配置指标体系,对黑河流域进行实地问卷调查,在此基础上对用户调查结果进行专家判断修正,应用层次分析法研究了各分配指标的权重分布.以黑河流域张掖地区为例的界定结果表明,除上游的肃南县和山丹县外,其余各县市的实际用水量都超过了各自界定的初始水权,这种差别为水资源产权交易管理提供了现实依据,为开展流域上游的生态保护补偿提供了理论基础.     

2009年秋至2010年春我国西南地区干旱及与历史场次干旱对比分析

2009年10月至2010年4月,我国西南地区由于受厄尔尼诺影响,气温偏高、降雨偏少,发生了秋冬春三季连旱,耕地受旱面积占全国同期耕地受旱面积的78%,受灾人口和大牲畜饮水困难头数都达到了近十年来该地区的最高水平。通过对比本次和历史场次干旱发现,西南干旱并非稀遇现象,1951~1990年的40年间该地区曾发生干旱12次,且1949年以来,干旱有缓慢加重的趋势;本次旱灾与1963年旱灾在时空分布、灾害成因和灾情方面较为相似,但从气象干旱的角度来看,虽然1963年部分受旱地区无有效降雨历时为11个月,高于本次旱灾的6个月,但本次受灾率和成灾率均为1949年以来的最大值,说明在快速发展背景下,经济社会面对干旱显得更为脆弱。这些结论对于认清西南地区干旱特性与旱灾演变规律,加强抗旱减灾体系建设,具有重要的参考价值。     

利用瞬变电磁技术进行地下水资源勘察

为解决内蒙古白旗地区水资源严重短缺的问题,采用瞬变电磁技术进行水资源勘察.本文通过分析平原地区含水层的矿化度和孔隙度对岩石电阻率的影响,得出在内蒙古干旱牧区浑善达克沙地的含水砂砾岩电阻率值为75~150 Ω·m之间变化.以导电球体为模型来计算地下含水层异常的可分辨时间窗口,确定该区地下含水层异常出现最大值的探测条件.瞬变电磁技术在结合已知自流井的电性差异基础上,可以对地下水的含水层和含水深度进行准确勘察,确定新的水井5位置,经钻孔验证喷水量达到每小时100 m3以上,满足白旗供水需求.验证了瞬变电磁技术在地下水资源勘察中的有效性,为西部地区水资源的评价提供了重要的技术依据.     

近40年来南四湖湿地NDVI变化特征及其控制因子分析

利用Landsat系列卫星的MSS、TM和ETM+遥感数据,计算了研究区的归一化植被指数(NDVI),并以此为湿地植被活动的指标,研究1973 2011年间该湿地植被变化特征及年内季节变化特征,揭示植被活动在年内和年际变化的控制因子以及湿地植被对于气候变化、人类活动和极端干旱事件的响应特征.结果表明:(1)近40年来南四湖湿地植被各个季节的变化特征不尽相同.春季NDVI呈现先降低后增加的特征,主要先后受到研究区围垦、渔业养殖等人为活动和气候变化(增温)的影响;夏季和冬季的NDVI呈现显著降低趋势,主要受到围垦、渔业养殖等人类活动的影响;秋季NDVI的变化不显著.(2)年内季节变化方面,湿地植被面积和NDVI都呈现单峰的变化特征,从春季开始增加,在夏季末(全年的第202和205 d)达到最大值,然后开始下降,到冬季降至最低.植被的年内季节变化特征主要受到月均温度的控制.(3)干旱在一定程度上不是湖泊湿地NDVI增加的限制因子.干旱导致湖泊水位下降,滨湖滩地及湖底露出,可能会促进湿地植被生长和植被面积的扩大,使得湿地NDVI增加.     

基于SPEI的黄河流域干旱时空格局研究

干旱是对人类社会影响最为严重的自然灾害之一,在中国干旱灾害频发,严重威胁着人们的生存环境.黄河流域是中国各大流域中受干旱影响最严重的区域,所以对黄河流域旱情进行监测尤为重要.文章基于1961~2015年黄河流域124个站点的月值气象数据,以标准化降水蒸散指数SPEI作为干旱指标,应用极点对称模态分解ESMD方法对SPEI序列进行时频周期与趋势分解,运用B-G分割算法进行阶段划分,从干旱年际变化、季节变化、干旱频率和干旱强度等方面对黄河流域及其8个水资源分区的干旱时空格局进行研究.结果表明:(1)近55年来黄河流域的干旱呈显著增加趋势, SPEI倾向率为-0.148 (10a)~(-1),其中兰州至河口镇地区干旱化趋势最为明显(-0.214 (10a)~(-1));(2)黄河流域干旱具有准2.9年、准5年、准10.2年和准18.3年的周期特征,且可划分为3个阶段(1961~1996年、1997~2002年和2003~2015年),对应SPEI均值分别为0.20、-0.71和-0.21;(3)干旱频率从大到小依次为夏季春季秋季冬季,均值分别为71.0%、47.2%、10.2%和6.9%;(4)干旱强度从大到小依次为夏季春季冬季秋季,均值分别为0.93、0.40、0.05和0.04.     

青海湖流域复合生态系统分析

青海湖流域是西北半干旱地区一个典型的复合生态系统,它主要由草地、湖泊、沙漠、农田和城镇生态系统复合而成。该系统具有高寒干旱、太阳辐射强,以及交通闭塞、人口少、经济落后等特点,因而抗干扰能力弱、输出水平较低。在气候暖干化条件下,不合理的人类经济活动使该系统暴露出土地沙化、植被退化、湖水位下降、渔业减产和鸟岛生态环境恶化以及潜在的工业污染扩大等一系列的生态环境问题。     

全新世气候渐变导致中亚地区植被突变

理解过去生态系统对气候变化的响应是评估未来气候变化影响的关键.在全新世气候逐渐变化背景下,萨赫勒-撒哈拉生态系统经历了由萨瓦拉到荒漠的突变.这样的非线性响应现象是否具有普遍意义仍需深入研究.本研究基于38个高质量的化石孢粉记录,系统分析了全新世中亚地区植被与气候的关系.结果显示全新世中亚地区的植被发生了两次大的突变,一次在早全新世(突变Ⅰ,"建立式"突变),另一次在晚全新世(突变Ⅱ,"崩溃式"突变),全新世中期则较稳定.然而这些植被突变无法与任何已知的气候突变事件相关联,并且不同区域发生植被转型的时间表现出异步性,显示出与当地降水量变化密切相关.这些植被突变可归因于植被响应轨道驱动的气候渐变的阈值效应.早全新世在轨道驱动下降水量增加,较湿润的区域首先达到植被"建立"的阈值,而在较干旱的区域明显较晚才达到该阈值.与之相反,晚全新世时在轨道驱动下降水量降低,首先在较干旱的区域达到阈值,导致植被"崩溃",而在较湿润地区延后达到阈值.另外,4.2kyr BP左右的干旱事件以及人类活动干扰对植被的崩溃退化也起到了一定的作用.上述认识得到了现代孢粉-气候关系分析以及生态系统模拟结果的支持.这些结果暗示未来气候变化一旦达到阈值将导致干旱生态系统产生突变.     

内蒙古地区深部水源瞬变电磁法探测

在干旱少雨,地表水资源紧缺的地区,寻找深部水资源已经成为经济可持续发展首要解决的问题,而如何快速、准确的实现深部水源的定位探测却鲜有文章涉及.本文利用瞬变电磁法在煤矿水文地质勘探中取得的探测经验,通过总结该探测方法的关键性技术,应用拟MT反演技术对探测资料进行解释,在内蒙古酸刺沟煤矿工业广场附近成功探测到两处深部低阻异常区,经过钻探验证,出水量均达到80m3/h,实现了深部水源的定位探测,为该煤矿水源井工程的建设提供了可靠的供水水源,解决了该煤矿生产、生活用水的问题.说明:采用瞬变电磁法探测技术探测深部水源,是一种较为理想且有效的探测方法,可以在地表水资源匮乏的地区推广应用.     

亚热带人工林水分利用效率的季节变化及其环境因子的影响

中国科学院千烟洲红壤丘陵试验站地处亚热带季风气候区,其植被类型主要为人工针叶林.研究采用涡度相关技术观测结果计算了2003年和2004年的植被水分利用效率(WUE)季节变化.适逢2003年极端干旱,降雨量远远低于多年(1985～2002)平均水平,其中7月份降水量仅是多年平均值的2.8%,气温却高于平均水平3℃,而2004年的气象条件与多年平均水平接近,这为研究WUE的环境控制作用提供了天然的条件.经研究发现千烟洲试验站的降水多集中于春季,而夏季则存在明显的季节性干旱现象,从而导致了该区域特殊的植被WUE季节变化模式.WUE的季节变化与冠层蒸发散(Fw)和总初级生产力(GPP)的季节动态大致相反,在夏季达到最小值,而在冬季则达到最大值.在冬季GPP和Fw随气温和大气饱和水汽压差(VPD)的增加而增加,且GPP和Fw的增加速率比较接近;而在干旱的夏季,GPP和Fw却随气温和VPD的增加而降低,并且GPP随气温和VPD变化而降低的速率要远远大于Fw,这破坏了GPP和Fw的平衡关系,并进一步改变了WUE的保守性,最终导致夏季WUE的降低.夏季干旱期土壤水分的亏缺和高强度的辐射也都是造成该生态系统WUE降低的原因.在冬季该生态系统植被的光合和蒸腾作用主要受控于环境因素,而受植被本身气孔行为的控制作用相对较弱.在夏季植被的Fw主要受植被本身气孔行为的限制作用,而植被的GPP则受环境因素和植被本身气孔行为的双重限制.     

Effects of surface characteristics on infiltration patterns in an arid shrub desert

Precipitation is often the sole source of water replenishment in arid and semi‐arid areas and, thus, plays a pertinent role in sustaining desert ecosystems. Revegetation over 40 years using mainly Artemisia ordosica and Caragana korshinskii at Shapotou Desert Experimental Research Station near Lanzhou, China, has established a dwarf‐shrub and microbiotic soil crust cover on the stabilized sand dunes. The redistribution of infiltrated moisture through percolation, root extraction, and evapotranspiration pathways was investigated. Three sets of time‐domain reflectometry (TDR) probes were inserted horizontally at 5, 10, 15, 20, 30 and 40 cm depths below the ground surface in a soil pit. The three sets of TDR probes were installed in dwarf‐shrub sites of A. ordosica and C. korshinskii community with and without a microbiotic soil crust cover, and an additional set was placed in a bare sand dune area that had neither vegetation nor a microbiotic soil crust present. Volumetric soil moisture content was recorded at hourly intervals and used in the assessment of infiltration for the different surface covers. Infiltration varied greatly, from 7·5 cm to more than 45 cm, depending upon rainfall quantity and soil surface conditions. In the shrub community area without microbiotic soil crust cover, infiltration increased due to preferential flow associated with root tunnels. The microbiotic soil crust cover had a significant negative influence on the infiltration for small rainfall events (～10 mm), restricting the infiltration depth to less than 20 cm and increasing soil moisture content just beneath the soil profile of 10 cm, whereas it was not as strong or clear for larger rainfall events (～60 mm). For small rainfall events, the wetting front depth for the three kinds of surface cover was as follows: shrub community without microbiotic soil crust > bare area > shrub community with microbiotic soil crust. In contrast, for large rainfall events, infiltration was similar in shrub communities with and without microbiotic soil crust cover, but significantly higher than measured in the bare area. Soil water extraction by roots associated with evapotranspiration restricted the wetting front penetration after 1 to 3 h of rainfall. Copyright © 2006 John Wiley & Sons, Ltd.     

Hydrological regimes in a tropical valley of New Caledonia (SW Pacific): Impacts of wildfires and invasive fauna

In New Caledonia wildfires and invasive mammals (deer and wild pigs) constitute the major agents of land surface degradation. Our study reveals the linkage between land cover and water balance on the northeast coast of New Caledonia (2400 mm annual rainfall) located on a micaschist basement. The hydrological regime of characteristic and representative land surfaces is assessed using a 1-year record from three 100 m² plots each, located in a forest area degraded by an invasive fauna, in a woody savannah which is regularly burned, and in a healthy forest area. The three plots present highly contrasting hydrological regimes, with annual and maximum runoff/rain ratios during a rain event of, respectively, 0.82, 0.16, 0.03, and 2.7, 0.7, 0.2, for the degraded forest, the savannah and the healthy forest. Such results suggest that subsurface flow originating from the contributing area above the degraded forest plot should exfiltrate inside the plot. A conceptual model for the degraded forest plot shows that water exfiltrating inside the plot represents 61% of the observed runoff. In savannahs, water should mainly be transferred downstream by subsurface flow within a thick organic soil layer limited by an impervious clay layer at a 20–30 cm depth. Savannahs are generally located above forests and generate the transfer of rainwater to downslope forests. Exfiltration into the forests can be the result of this transfer and depends on the thickness and permeability of the forest topsoils and on topographic gradients. Water exfiltration in forest areas highly degraded by pigs and deer enhances erosion and increases further degradation. It probably also limits percolation in the areas located downstream by increasing the amount of superficial runoff concentrated in gullies.     

集水区尺度景观格局与过程的时空动态分析:美国俄勒冈州塞勒支盆地1977-2000年的变化

在集水区尺度利用景观生态学的原理进行分析和管理是现代生态学与地理科学的一个重要课题.在人口增长和经济发展的压力下,集水区的格局和过程己受到人类活动越来越强烈地干扰.赛勒支盆地是一个典型的美国太平洋西北部沿海地区的集水区,本文以此为例,研宄了美国俄勒冈州中部集水区尺度的景观格局和过程在人类活动干扰下的时空动态.通过卫星遥感影像的应用,我们对1977年到2000年间赛勒支盆地土地覆盖的变化进行了检测.我们用陆地资源卫星1977年的多光谱影像(MSS), 1988年的专题影像(TM)' 2000年的增强专题影像(ETM+)高精度地定量分析了森林演替系列(如,演替后期的老针叶林和成熟针叶林,演替前期的年轻针叶林,以及更新的幼林）和其它土地覆盖类型的变化.景观的空间格局通过多种格局指数,例如,缀块指数、缀块形状复杂性指数、以及连接指数等进行了分析.同时,基于美国太平洋西北部主要森林类型和其它土地覆盖类型碳通量和碳贮量的空间数据库和文献资料,我们对 1977-2000年赛勒支盆地中的碳库及其在人类活动干扰下的变化作了测定.研宄结果揭示出,因为森林皆伐,老针叶林和成熟针叶林在1977-2000年间显著地减少,分别由占整个盆地土地覆盖面积的23%和12%, 减少为12%和7%;与此相反,年轻针叶林和无林地则分别从24%和5%增加为43%和14%.同时,因为采伐等干扰,留存的老针叶林和成熟针叶林空间分布格局的破碎度也迅速增加.集水区的碳收支在 1977-2000期间发生了巨大的变化.在收获干扰的压力下,在1977-2000年间,整个集水区的生态系统碳贮量从 17640797t 减少到 13405720t;净生态系统生产力(Net Ecosystem Production, NEP)由每年 100462tC 减少为每年76800tC.     

Dating desert pavements – First results from a challenging environmental archive

Desert pavements are widespread landforms of arid environments. They consist of a monolayer of clasts at the surface, associated with an underlying unit of eolian fines. In some situations, buried desert pavements can be observed, which is interpreted as a change in the environmental conditions. Therefore, it is believed that desert pavements represent important paleoenvironmental sediment archives, especially for arid environments, where natural archives of past environments are rare. To better understand the formation process of desert pavements and to enable the paleoenvironmental interpretation of these valuable sediment archives, reliable chronologies are of crucial importance. Thus, OSL dating was applied to samples from well-developed desert pavements in two different study areas, the Cima Volcanic Field, eastern Mojave Desert, USA, and the desert of northeastern Badia, Jordan. To test the suitability of the sediments for OSL dating, the luminescence characteristics of the fine- and coarse-grain quartz fraction are described and compared. Finally, first OSL ages are presented.     

The response of vegetation cover and dune activity to rainfall,drought and fire observed by multitemporal satellite imagery

The stable longitudinal dunes in the northern Simpson Desert, Australia, were observed in satellite imagery to become more active after vegetation cover was reduced by fire and drought. Subsequent rainfall events also resulted in significant vegetation regrowth and dune stabilization. These switches between more active and stable conditions have not been previously described in the largely vegetated dune fields of central Australia. The observations, made on 12 dune sites, relied on high spatial resolution satellite imagery to observe dune crest activity, and seasonal Landsat fractional cover imagery to observe vegetation cover changes. The non-photosynthetic vegetation (NPV) component of the fractional vegetation cover images revealed significant changes in hummock grass cover on the dunes between 1988 and 2018, with a positive relationship with the three-year cumulative rainfall, disrupted by two periods of patchy burning. Only those sites that had burnt became active, and only after vegetation cover had remained low (NPV < 16%) during the ‘Millennium Drought’. There is no threshold in vegetation cover, below which dune crests become active, but active dune features require four-years of low NPV cover (< 16%) to develop. The large rainfall event that ended the drought increased NPV cover, stabilizing the dunes. Similar hummock grass covered dunes are present across large areas of the arid zone, and are likely to respond in similar ways, given that fire and drought are common occurrences in Australia. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.     

Design of store‐release covers to minimize deep drainage in the mining and waste‐disposal industries: results from a modelling analyses based on ecophysiological principles

Sustainable long‐term storage of municipal waste and waste rock from mining activities in waste dumps (either above or below the land surface) requires minimization of percolation of rainwater into and then through stored waste material. There has been increasing attention given to the use of store‐release covers (transpirational covers) to achieve this. However, the design of such covers remains problematic because of the unique combinations of weather, vegetation composition, soils and their interactions that determine the efficacy of each design that could be available for the construction of the covers. The aim of the work described here was to use ecophysiological knowledge of soil‐plant‐atmosphere (SPA) interactions through the application of a detailed mechanistic model of the SPA continuum. We examined the relative influence of soil depth, soil texture, leaf area index and rainfall as determinants of rates of evapotranspiration and water budget for several different theoretical cover designs. We show that minimizing deep drainage requires a cover that has the following attributes: (i) a water storage capacity that is large enough to store the volume of water that is received as rainfall in above‐average wet months/seasons; (ii) a root distribution that explores the entire depth of the cover; (iii) a leaf area index that is present all year sufficient to evapotranspire monthly rainfall; and (iv) takes into account the intra‐annual and inter‐annual variability in rainfall and other climatic variables that drive ET. Copyright © 2012 John Wiley & Sons, Ltd.     

Dead level contours and infiltration pits for risk mitigation in smallholder cropping systems of southern Zimbabwe

The persistent droughts, dry spells, and chronic food insecurity in semi-arid areas necessitate the introduction of more robust rainwater harvesting and soil water management technologies. The study reported here was conducted to assess the influence of dead level contours and infiltration pits on in-field soil water dynamics over two growing seasons. A transect consisting of six access tubes, spaced at 5 m interval, was established across each dead level contour with or without an infiltration pit before the onset of the rains. Two access tubes were installed upslope of the contour while four tubes were installed on the downslope side. Dead level contours with infiltration pits captured more rainwater than dead level contours only resulting in more lateral soil water movement. Significant lateral soil water movement was detected at 3 m downslope following rainfall events of 60–70 mm/day. The 0.2–0.6 m soil layer benefited more from the lateral soil water movement at all the farms. Our results suggest that dead level contours have to be constructed at 3–8 m spacing for crops to benefit from the captured rainwater. It is probably worth exploring strip cropping of food and fodder crops on the downslope of the dead level contours and infiltration pits using the current design of these between-field structures. With the advent of in situ rainwater harvesting techniques included in some conservation agriculture practices it will benefit smallholder cropping systems in semi-arid areas if these between-field structures are promoted concurrently with other sustainable land management systems such as conservation agriculture.     

A hydrological model for the Negev Desert Highlands: effects of infiltration,runoff and ancient agriculture / Modèle hydrologique pour les régions montagneuses du Negev: les effets d'infiltration,d'écoulement et de l'agriculture ancienne

Abstract

A digital computer model of basin regime was developed for the Negev Desert Highlands, a region which experiences a mean annual rainfall of about 100 mm. The model was based on 13 years of rainfall and runoff records. Relationships obtained from experiments were used to determine areal distribution of rainfall, infiltration rates of soils, effects of slope angle on runoff, stone cover, rainfall intensity, antecedent rainfall, basin size, soil crust, overland flow and channel losses. These relationships also explain how ancient civilizations were able to collect ample water from small basins in order to establish stable agricultural settlements.     

巴丹吉林沙漠湖泊水分补给机制的模拟——以苏木吉林湖区为例

巴丹吉林沙漠气候干旱,蒸发强烈,与之形成鲜明对比的是沙漠腹地湖泊群的长久不衰,目前对于湖泊水分的补给来源仍存在争议.本文以水量均衡为基础,在苏木吉林湖区开展了降水、蒸发及湖水位和地下水位的动态监测,结合已有的水文地质资料建立地下水流动三维模型,重现湖区地下水位的季节动态变化,并基于模型进行水均衡分析.结果表明:苏木吉林湖区降水入渗补给量不足以平衡湖泊蒸发量,湖泊需要深层承压水的越流补给;湖水位和地下水位均呈现正弦曲线形态,11月最低,4月达到峰值,水位变幅分别为22和18 cm;湖区地下水多年平均总补给量为11620 m3/d,其中降水和承压水越流分别约占13%和87%,降水补给量夏季高、冬季低,承压水越流补给量季节变化不明显;承压水越流补给量可能主要来源于沙漠周边山区降水,未发现明显的水量亏空需要断裂导水来弥补.研究结果为巴丹吉林沙漠地下水资源分析及合理利用提供科学依据.     

我国东南沿海中小流域洪水模拟研究

我国东南沿海多为独流入海的中小流域,河流短小,流域调节能力弱.该区洪水历时较短,但危害较大,加之近年来区内经济的迅速发展,洪水造成损失日趋加剧,因此开展此区洪水特性和防洪减灾研究意义重大.本文以中国东南沿海曹娥江流域为典型,根据中小流域洪水的特点,在初步分析流域降雨径流的成因和洪水演进规律的基础上,开展了流域洪水模拟研究, 选择建立了流域降雨径流模型以及洪水演进模型,重点探讨了利用遥感信息和GIS相结合确定水文模型参数的方法和途径,经实验流域资料检验分析,其模拟结果计算精度满足要求.该研究将有助于该区流域降雨径流特性及洪水演变规律的深入研究,同时为东南沿海中小流域洪水模拟预测和防洪减灾研究提供了经验和模式.