用隔绝法对极干旱区土壤水分来源的分析

 通常认为极干旱区土壤水分来源于降水、大气或凝结水,深埋区不存在潜水蒸发。然而通过使用拱棚法初步证明在极干旱深埋区存在潜水蒸发,而潜水是土壤水分的重要来源。为了进一步求证土壤水分来源,开挖200 cm×200 cm×200 cm的土坑,完全隔绝与下层土壤及四周的水分联系,回填后监测土壤10、30、50、100、150 cm的空气温湿度;同时设置与四周隔绝但底面联通的对照坑。27 d后都模拟25 mm降雨。监测发现模拟降雨前联通土壤的水分含量、空气相对湿度、绝对湿度都明显高于隔绝土壤。1 a后远离降雨时土壤水分的检测发现隔绝土壤水分含量低于联通对照,但因隔绝土壤处于潜水蒸发漫溢的相同气象环境,其湿度不会无限下降。隔绝对比实验反演证明深埋极干旱区存在潜水蒸发。     

青海湖滨土地沙漠化驱动机制

在自然因素和不合理人为活动的影响下,青海湖流域及其周边地区正面临土地沙漠化、湿地萎缩、草场退化、水土流失等严重的生态环境问题。本文分析了青海湖滨土地沙漠化现状及其驱动因素。结果表明:青海湖滨广泛分布的古风沙沉积物是现代沙漠化的沙物质来源,现代流动沙丘的粒度特征与古风成沙丘粒度极为相似,两者的继承与改造关系极为明显。草皮层及其下的粉沙土层是古沙丘的保护层。保护层的机械破坏,使下伏松散的古风沙沉积物暴露,是形成沙漠化的关键一步。随后在风蚀、雨水冲刷及其他因素的共同作用下,松散的古风沙沉积物被侵蚀,引起草皮层坍塌,导致古沙丘活化,风沙活动加剧,形成风沙沉积。流水侵蚀和地层沉陷是导致草皮层机械破坏的主要因素。青海湖水位下降,河流沉积,风沙入湖,都可使沙地面积增加,但仅限于湖边局部地方。     

黄土区渭北旱塬苹果基地对区域水循环的影响

通过对苹果地、农田和其他塬面主要土地利用方式的比较研究，发现苹果地土壤入渗速率大、降雨产流率低和存在生物利用型土壤干层。这些水文学性质将增强土壤－植物－大气间垂直水分交换，削弱降雨转化为地表径流和地下水的比例，最终影响区域地表和地下水资源的数量。另外土壤干层的出现还削弱了土壤水库对年际和季节性干旱的调节作用，导致苹果产量随降雨量的自然变化呈现较大波动。     

Effects of soil degradation on infiltration rates in grazed semiarid rangelands of northeastern Patagonia, Argentina

In grazed semiarid ecosystems, considerable spatial variability in soil infiltration exists as a result of vegetation and soil patchiness. Despite widespread recognition that important interactions and feedbacks occur between vegetation, runoff and erosion, currently there is only limited quantitative information on the control mechanisms that lead to differences in infiltration from different vegetation types. In this paper, we determine (i) the relationship between vegetation and soil surface characteristics and (ii) the soil infiltration rate by using rainfall simulations on runoff plots (0.60 × 1.67 m) in three plant communities of northeastern Patagonia: grass (GS), degraded grass with scattered shrubs (DGS), and degraded shrub steppes (DSS). Our results clearly indicate that vegetation and soil infiltration are closely coupled. Total infiltration was significantly higher in the GS (69.6 mm) compared with the DGS and DSS (42.9 and 28.5 mm, respectively). In the GS, soil infiltration rate declined more slowly than the others communities, reaching a terminal infiltration rate significantly greater (57.7 mm) than those of DGS and DSS (25.7 and 12.9 mm, respectively). The high rate of water losses via overland-flow may limit the possibilities for grass seedling emergence and establishment and favor the persistent dominance of shrubs.     

Water availability in almond orchards on marl soils in southeast Spain: The role of evaporation and runoff

Clean sweeping (i.e., frequent and shallow tillage in orchards) is a common practice in semi-arid areas. A potential drawback in dry areas is that the tree roots cannot access the water in the plough layer. Our objective was to quantify the loss of water by evaporation and the loss or gain by overland flow in almond (Prunus dulcis Mill.) orchards on loamy soils in southeast Spain. The evaporation from a 15 cm plough layer equals 70–104% of annual precipitation, taking into account losses or gains by overland flow. The large evaporation explains the low canopy cover observed, which averaged 3.2%. The runoff coefficient of the test sites is 1–6%. There is no drainage below 15 cm during dry years, except for an area that receives a net influx of overland flow. The trunk basal area in this depression is 12% larger compared to the rest of the field. The options for increasing the water intake of the trees are to reduce the tillage depth or to switch from clean sweeping to no-tillage combined with chemical weeding.     

陕西省子午岭生态功能区水源涵养能力研究

应用InVEST模型和SCS模型,计算得出研究区多年平均水源涵养量约为3×108 m3,涵养深度69.79 mm,表明研究区具有比较突出的水源涵养服务功能,特别是在森林和灌丛分布相对集中的子午岭自然保护区内,水源涵养能力处于较高水平。不同土地利用类型的水源涵养能力有较大差别。由于灌丛具有较好的降水截留能力和较小的蒸腾作用,水源涵养能力最强;而森林由于蒸腾旺盛,加之冠层截留的大部分降水用于蒸发而无法积累,使其水源涵养能力稍低于灌丛;草地和农田覆盖地区,降水极易流失,因而草地和农田的水源涵养能力较差,对区域总水源涵养量的贡献也最小。此外,研究区多年平均产水深度139.4 mm,整体趋势是从东南向西北方向减小,与区域降水量空间变化趋势一致,在土地利用类型的影响下,这一趋势更加明显;多年平均径流深度71.1 mm,空间上大致由南向北减少,同时,由于径流深度还受到降水时间分配、土地利用类型、土壤质地的影响,因此呈现出较为复杂的空间分布特征。     

Effect of apple production base on regional water cycle in Weibei upland of the Loess Plateau

Weibei upland of the Loess Plateau containing Xianyang city, northern part of Weinan city, southern part of Yan'an city and a part of Tongchuan city covers a total area of 30,000 km2 with an elevation of 900 to 1500 m above sea level and annual average precipitation is from 550 to 600 mm. The Luochuan and Changwu uplands are two of those large uplands in Weibei region. These uplands have been identified as a commercial apple production base for its special features of topography and climate…     

Effect of apple production base on regional water cycle in Weibei upland of the Loess Plateau

Weibei upland, located in southern part of the Loess Plateau, is a commercial apple production base in China. The enlargement of apple-planting area has a great impact on the regional water cycle. The effects of different land use on hydrological parameters are compared and studied in this paper. The main results are as follows: (1) The initial and steady infiltration rates in apple orchard are higher than those in other land use types such as grassland, idle land and farmland. Their initial rates of infiltration are 0.823 cm/min, 0.215 cm/min, 0.534 cm/min and 0.586 cm/min in apple orchard, grassland, idle land and farmland respectively. Their steady infiltration rates are 0.45 cm/min, 0.038 cm/min, 0.191 cm/min and 0.155 cm/min respectively. (2) There is no runoff generated in plot of apple orchard in all 8 storm events in observed natural rainfalls, while runoff is generated in winter wheat plot, corn plot and alfalfa plot with runoff coefficients of 2.39%, 1.58% and 0.31% respectively. (3) The transpiration of apple trees is strong and thus soil moisture is gradually depleted. The average soil water contents in 3-9 m soil profile in Changwu plots with apple trees of 14 and 32 years in age are 11.77% and 11.59% and in Luochuan plots with those of 15 and 28 years in age are 11.7% and 11.59% respectively, which are nearly 9.0% of wilting moisture of Changwu soil and 8.6% of wilting moisture of Luochuan soil. The pathway of rainfall percolating to groundwater is hindered by dry soil profile.     

GEOMORPHOLOGICAL CHANGES WITHIN A HILLSLOPE CAUSED BY A WINDTHROW EVENT IN THE TATRA MOUNTAINS,SOUTHERN POLAND

Tree uprooting plays an important role in hillslope evolution. The geomorphological impact of tree uprooting after a foehn wind occurrence, in December 2013 in the Tatra Mountains, was investigated. Geomorphological mapping was conducted in three watersheds. Additionally, in one of the watersheds, 459 windthrow pits were measured, in an area of 6.4 ha. The mean volume of a pit was 2.41 m³, and the mean surface area was 5.47 m². 3.9% of the area was affected by windthrow pits, however locally the magnitude of changes was significantly higher, reaching up to 14.5% of the surface area. Slope inclination weakly influenced the effects of uprooting, and a decrease in the average depth of pits on steep slopes was observed. Individual windthrow pits (five cases) initiated the activity of geomorphological processes, and two cases of periodic springs were noted. Changes in the relief of small landforms caused by tree uprooting were documented. Windthrow creation facilitated the delivery of the soil material from the slopes into the channels.     

SCS-CN 径流模型中CN值确定方法研究

 径流计算是区域径流量预报和水土资源评价模型中的重要组成部分。SCS-CN径流模型是一种常用的径流计算方法。径流曲线数（CN）是SCS-CN模型中反映降雨前流域特征的一个综合参数。用北京密云石匣3个小区实测降雨径流资料,用平均值法、中值法、算术平均值法、S对数频率分布法以及渐近线法来反推CN值,并用反推的CN值计算了径流深。用模型效率系数、相关系数和合格率比较了这5种方法确定的CN值计算径流深的优劣。结果表明：从模型有效系数来看,渐近线法得到的模型有效系数最好;从相关系数和合格率来看,算术平均值法的结果最好。相对于渐近线法来讲,算术平均值法计算CN简单,因此建议在计算CN值时用算术平均值法。     

Occurrence of soil erosion after repeated experimental fires in a Mediterranean environment

In the Mediterranean area, forest fires have become a first-order environmental problem. Increased fire frequency progressively reduces ecosystem recovery periods. The fire season, usually followed by torrential rains in autumn, intensifies erosion processes and increases desertification risk. In this work, the effect of repeated experimental fires on soil response to water erosion is studied in the Permanent Field Station of La Concordia, Valencia, Spain. In nine 80 m² plots (20 m long × 4 m wide), all runoff and sediment produced were measured after each rainfall event. In 1995, two fire treatments with the addition of different biomass amounts were applied. Three plots were burned with high fire intensity, three with moderate intensity, and three were unburned to be used as control. In 2003, the plots with the fire treatments were burned again with low fire intensities. During the 8-year interval between fires, plots remained undisturbed, allowing regeneration of the vegetation–soil system. Results obtained during the first 5 months after both fire experiments show the high vulnerability of the soil to erosion after a repeated fire. For the burned plots, runoff rates increased three times more than those of 1995, and soil losses increased almost twice. The highest sediment yield (514 g m^− 2) was measured in 2003, in the plots of the moderate fire intensity treatment, which yielded only 231 g m^− 2 of sediment during the corresponding period in 1995. Runoff yield from the control plots did not show significant temporal changes, while soil losses decreased from 5 g m^− 2 in the first post-fire period to 0.7 g m^− 2 in the second one.     

福建洛阳江口红树林湿地及其周边地区景观变化研究

利用"3S"技术,对福建洛阳江口红树林湿地及周边地区1993年、2001年、2003年和2006年遥感影像进行了动态分析.将研究区的景观类型划分为红树林、米草(Spartina)地、滩涂、水域、建设及交通用地、其他林地与农田7类;分析各类型景观格局特征和动态变化以及各景观类型间的转化.结果表明,4个时期的红树林面积发生明显变化,与1993年相比,2006年红树林的面积增加了5倍,达到145.08 hm2;红树林的空间分布范围也在不断向南延伸,红树林空间质心变化由早期向西北偏移变为后期向东南偏移.4个时期中,研究区红树林的平均斑块面积在2001年最小(0.34 hm2),而斑块数(58)、破碎度(0.000 291)、分离度(223.15)、斑块形状指数(20.67)、分维数(1.50)都在2001年达到最大,红树林在2001年破碎化现象最明显,分布零散,斑块形状最复杂.2001年,研究区其他6种景观类型的连续性和整体性较差,这与研究区附近城乡建设和经济发展有关.滩涂与其他林地的动态度在2003～2006年间最大;红树林、米草地、建设及交通用地以及农田的动态度在2001～2003年间最大,这主要与城乡建设以及红树林湿地恢复和外来入侵物种防治工作有关.在其他林地、建设及交通用地和农田的面积转化中,建设及交通用地面积在1993～2006年间增加了1 526.17 hm2.     

巴丹吉林沙漠边缘地区植被特征

通过在巴丹吉林沙漠野外植被调查,描述了植被的生活型和群落的空间分布特征,分析了植被多样性、优势度及均匀度指数,并探讨了历年来气候变化对植被分布的影响。结果表明：（1）巴丹吉林沙漠植物种类较少,可分为小乔木、灌木、小灌木、半灌木、多年生草本和一年生草本6类生活型。其中灌木种类最为丰富,小乔木最少。（2）巴丹吉林沙漠东南一带物种丰富度和多样性高于西北一带,南缘地区植被群落分布及植被群落多样性亦均高于北缘地区。（3）近53 a巴丹吉林沙漠气温发生显著变化,蒸发量增加。南缘地区增温而降水减少。这种变化对于以水分为主导因子的沙漠地区植被发育来说极为不利,有加剧沙漠南缘荒漠化的威胁。     

北京地区径流曲线数模型中的径流曲线数

径流曲线数模型(SCS-CN模型)是国内外最受欢迎的地表径流评价方法,该模型只需综合参数--径流曲线数(CN),该参数反映降雨前流域的地表和土壤特征。本文的目的是确定北京地区径流曲线数模型中的径流曲线数。研究采用了北京密云、延庆、门头沟64个坡面径流小区的降雨径流资料,用算术平均值法计算出小区径流曲线数值,用定水头法测定了北京主要土壤类型和土地利用类型的饱和导水率,用经验公式确定出64个坡面径流小区的饱和导水率值,并根据饱和导水率确定了北京地区和坡面径流小区的水文土壤组类型,得到了北京不同水文土壤组、土地利用下的径流曲线数数据库。结果表明:北京地区主要水文土壤组为B类;土地利用、水土保持措施、植被盖度和前期土壤湿度等对径流曲线数有显著影响;根据北京径流小区径流资料得到的径流曲线数值比美国土壤保持局查算表提供的数值要大。本研究结果可为该区域的地表水资源量评价以及土地利用管理提供服务。     

三峡库区紫色土坡地养分状况及养分流失*

紫色土是三峡库区移民安置区的主要坡地土壤。本研究采用典型区域调查,代表性土壤剖面养分分析,结合实验小区人工降雨的方法,初步研究了发育于侏罗纪紫色砂泥岩母质上紫色土的养分状况、养分流失特点、过程及影响养分流失因素。     

长白山哈泥泥炭地7种苔藓分布与环境关系研究

在长白山哈泥泥炭地调查7种苔藓的典型生境,共计93个样方,计测样方中苔藓植物的盖度和包括泥炭全氮（TN）、全磷（TP）、K^＋和Ca^2＋等在内的9个环境因子,应用典范对应分析对数据进行处理,做出样方、物种与环境因子关系二维排序图,排序图直观地反映苔藓植物与环境因子间的关系。结果表明,排序图中同种苔藓为主的样方多数集中分布,个别分散分布;水位埋深、沼泽水pH以及乔木郁闭度和灌木盖度是影响泥炭地苔藓植物生态位分异的主要环境因子,泥炭全磷（TP）对苔藓植物分布影响较大。7种苔藓中,尖叶泥炭藓（Sphagnum capilifolium）、大泥炭藓（S．palustre）在乔木郁闭度和pH梯度上,喙叶泥炭藓（S．fallax）、沼泽皱缩藓（Aulacomnium palustre）在水位埋深和灌木盖度梯度上,生态位分异明显。锈色泥炭藓（S．fuscum）、桧叶金发藓（Polytrichum juniperinum）和中位泥炭藓（S．magellanicum）在各个环境梯度上生态位都比较相似。     

Vertical distribution of soil moisture and surface sandy soil wind erosion for different types of sand dune on the southeastern margin of the Mu Us Sandy Land, China

Soil moisture is a critical state affecting a variety of land surface and subsurface processes. We report investigation results of the factors controlling vertical variation of soil moisture and sand transport rate of three types of dunes on the southeastern margin of the Mu Us Sandy Land. Samples were taken from holes drilled to a depth of 4 m at different topographic sites on the dunes, and were analyzed for soil moisture, grain-size distribution and surface sediment discharge. The results show that: (1) The average soil moisture varies in different types of dunes, with the following sequences ordered from highest to lowest: in the shrubs-covered dunes and the trees-covered dunes the sequence is from inter-dunes lowland to windward slope to leeward slope. The average moisture in the bare-migratory sand dunes is sequenced from inter-dunes lowland to leeward slope to windward slope. (2) Vegetation form and surface coverage affect the range of soil moisture of different types of dunes in the same topographic position. The coefficient of variation of soil moisture for shrubs-covered dunes is higher than that of other types of dune. (3) The effect of shrubs on dune soil moisture is explained in terms of the greater ability of shrubs to trap fine-grained atmospheric dust and hold moisture. (4) The estimated sand transport rates over sand dunes with sparse shrubs are less than those over bare-migratory dunes or sand dunes with sparse trees, indicating that shrubs are more effective in inhibiting wind erosion in the sandy land area.     

紫色丘陵区典型小流域氮素迁移及其环境效应

选择四川盆地中部紫色土丘陵区典型小流域,通过2002～2004年3 a对主要土地利用地类氮素流失、小流域地表水和井水氮素迁移形态、途径与通量的连续观测,研究非点源氮素的来源、去向、迁移特征及其环境效应。结果表明,紫色土坡地氮素主要通过径流与泥沙迁移,坡耕地、居民点氮素流失是小流域非点源氮的主要贡献者,其氮素流失负荷分别为150．4kg、73．84 kg,占小流域氮素迁移总负荷的52．4％、25．7％；紫色丘陵区小流域地表水已呈现明显氮索富营养化特征,地下水硝酸盐污染较为严重,应重视该地区非点源污染控制；小流域氮素迁移的尺度差异明显,坡地以颗粒态氮为主,小流域以硝酸盐为主,氮素迁移的尺度效应可能导致非点源氮污染的异地效应,从而加剧长江三峡水体富营养化压力。     

The effect of an increasing tree canopy on hay meadow vegetation in south-west Norway

In a sloping hay meadow, situated on phyllitic soils in the fjord region of western Norway, shade from solitary trees in the lower meadow and from high tree cover on the upper slopes has reduced the number of indicators of traditional management, which include vulnerable hay-meadow species. However, the number of additional species, for example, forest species, was higher in shade from solitary trees than in the open; the areas under the crowns may have functioned as refuges for forest species in former days, when wooded hay meadows, comprising small woodlots, solitary trees and shrubs, were widespread in the region. Indicators of traditional management were more frequent in dry plots than in moist plots, but most species in this group occurred in moist plots too. To keep the habitat area for these species as large as possible and at the same time restore the former well-managed tree-layer of the meadow, the removal of large Fraxinus excelsior and Alnus incana specimens from the upper slopes and reduction of the crowns of solitary Taxus baccata and Prunus domesticus on the lower slopes is recommended.     

应用EUROSEM模型对三峡库区陡坡地水力侵蚀的模拟研究

三峡库区坡地资源被广泛利用,但水土保持措施没有被很好地利用。坡地,尤其是陡坡地是库区主要泥沙来源,因此,有效评估土壤侵蚀风险、预测径流和侵蚀速率以及选择合理的水土保持措施在该地区显得非常必要。EUROSEM模型是动态分布式模型,可以在单独地块或小流域中预测水力侵蚀强度,其特点比较适合库区土壤侵蚀预测预报。本研究以在三峡库区秭归县王家桥小流域水土保持试验站的标准径流小区的人工降雨资料为基础,应用EUROSEM模型模拟陡坡地中的侵蚀状况。模拟结果表明,EUROSEM对人工降雨中径流模拟效果较好,但对土壤流失的模拟效果相对较差,更精确地模拟库区陡坡地的土壤侵蚀状况则需要作进一步的研究