灌丛沙堆是干旱区一种典型的景观类型,经常出现在靠近流沙地带。在地处荒漠草原带的宁夏盐池北部的流沙边缘就发育有典型的白刺(Nitraria tangutorum)灌丛沙堆。本文对不同沙源距离和灌丛生长状况下的白刺灌丛沙堆形态特征进行了研究。结果表明:荒漠草原带白刺灌丛沙堆的高度0.2～4.8 m,90.05%的高度小于3.0 m;体积0.11～805.17 m³,6.08%的体积小于150 m³;面积0.86～333.3 m²,72.26%的小于50 m²。灌丛沙堆长轴长和短轴长、高度和面积、高度和体积、面积和体积间都存在很好的幂函数关系,随着灌丛沙堆高度的增加,其面积和体积也增加。沙源对白刺灌丛沙堆的分布特征有显著影响,灌丛沙堆的高度、面积和体积和沙源距离都有很好的抛物线形关系。白刺灌丛的生长状况对灌丛沙堆的形态特征也有明显的影响,即白刺灌丛生长状况越好,灌丛沙堆的高度、面积和体积也增大。

Nebkha is a typical landscape in arid and semi-arid land, which commonly distributed in the quicksand regions. There are lots of Nitraria tangutorum nebkhas in the quicksand edge of north YanChi country under the desert steppes. This paper studied the effects of sand source and N. tangutorum growth condition on nebkhas morphology characteristics. The results are as follows: the height of N. tangutorum nebkhas in desert steppes were between 0.2-4.8 m, and about 90.05% of them were smaller than 3.0 m; the volume were between 0.11-805.17 m and only about 6.08% of them were bigger than 150 m³; the area were between 0.86-333.3 m², and about 72.26% of them were under 50 m². The relationships of long axis and short axis, height and area, height and volume, area and volume can well described with power functions. Area and volume of nebkhas were increased with the increase of nebkhas height. The distance of sand sources significantly affect the distribution characteristics of nebkhas. The growth conditions of N. tangutorum also affect the morphology characteristics of nebkhs, and the heights, areas, volumes of nebkhas were increased with the increase of coverage of N. tangutorum.

灌丛沙堆是干旱、半干旱区绿洲边缘常见景观类型，在绿洲风沙防护及生物多样性保护方面有重要意义。本文对中国西北干旱区不同气候区常见的柽柳（Tamarix chinensis）、泡泡刺（Nitraria sphaerocarpa）和柠条锦鸡儿（Caragana korshinskii）灌丛沙堆形态和养分积累特征进行了对比研究。结果表明：柽柳灌丛沙堆高度、面积和体积显著高于泡泡刺和柠条锦鸡儿灌丛沙堆，泡泡刺灌丛沙堆高度、面积和体积最小。3种灌丛的存在都显著增加了沙堆土壤有机质含量，使灌丛沙堆成为“肥岛”，其中柽柳灌丛沙堆“肥岛”效应最明显。柽柳灌丛沙堆土壤有机质、全碳、全氮和凋落物含量显著高于泡泡刺和柠条锦鸡儿灌丛沙堆。主要原因是柽柳枝条茂密，拦截面积大且凋落物量大，因此沙物质拦截和养分积累能力强于其他两种灌丛。另外，不同气候区沙源和气象条件的差异也可能导致灌丛沙堆形态及养分累积特征不同。

Nebkhas， or vegetated sand dunes， are a common landscape in the transitional zone of oasis and desert in arid and semi-arid regions. And， nebkhas are critical in preventing desertification and biodiversity protection of oasis. This paper studied the differences of nebkhas morphology characteristics and soil nutrition content among three types of nebkhas （ Tamarix chinensis， Nitraria sphaerocarpa and Caragana korshinskii） which from different regions. The results are as follows： The height， area and volume of T. chinensis nebkha were significantly higher than N. sphaerocarpa and C. korshinskii nebkhas. And the height， area and volume of N. sphaerocarpa nebkha were the smallest. The existence of both three types of shrubs were significantly increased soil organic matter， and made nebkhas into “fertile island”. Soil organic matter， total carbon， total nitrogen and total phosphorus of T. chinensis nebkha were all significantly higher than N. sphaerocarpa and C. korshinskii nebkhas. The mainly reason was that soil litter content of T. chinensis nebkha was the highest， and the growth habitof T. chinensis are vertical， dense， and multi-branching. Thus， theinterception and accumulation capability of T. chinensis nebkha is stronger than N. sphaerocarpa and C. korshinskii. In addition， the differences of sand source and meteorological condition among different regions may also lead to the differences of morphological characteristics and soil nutrition content of nebkhas.

通过野外调查，分析了民勤荒漠绿洲过渡带不同地下水位埋深的3个白刺灌丛沙堆样方内灌丛沙堆水平投影面积与高度的关系、灌丛沙堆的空间分布及空间自相关关系，确定各个样方白刺灌丛沙堆的演化阶段，并分析了地下水位、沙源及植被生长对灌丛沙堆发展的影响。结果表明,白刺灌丛发育阶段灌丛沙堆的水平投影面积和高度之间为线性关系；稳定阶段白刺灌丛沙堆高度与水平投影面积为幂函数关系；退化阶段白刺灌丛沙堆高度和水平投影面积为二次函数关系。不同演化阶段白刺灌丛沙堆的空间自相关尺度为5 m，且3个样方之间自相关尺度没有显著差异。

Relationships of nebkhas horizontal projection area with nebkhas height and nebkha spatial distribution, and the spatial autocorrelationship were investigated in the Minqin desert-oasis ectone. The results were applied to categorize the developing phases of nebkhas. Effects of underground water table, distance to sand source, and plant growth on nebhas evolution were also investigated. Relationship between nebkhas horizontal projection area and height in the initial phase, developing phase, and degradation phase of nebkhas evolution demonstrate linear, power, and quadratic function relationshps, respectively. The spatial autocorrelation scale of nebkhas in the three phases is 5 m, and no significant difference among autocorrealtion scales of the three evolution phases is observed.

沙源的供给形式和丰富度是控制沙丘形态的直接因子。在内蒙古高原阴山北麓,以洪积扇下风向、农耕地下风向和残积地内的小叶锦鸡儿(Caragana microphylla)灌丛沙堆为研究对象,用典型样方法对沙堆的分布及形态进行系统测量。结果显示:相同样地面积内,相比内源型供给的残积地内的灌丛沙堆,外源型供给的洪积扇和农耕地下风向灌丛沙堆数量少,但单体沙堆的平均尺度大;洪积扇下风向样地沙堆的各项形态参数顺风向急剧递减,残积地内沙堆的水平形态参数顺风向缓慢递增,灌丛及沙堆高度顺风向保持不变,这一结果是对沙源相对位置不同导致沙粒运移方式和沙源量产生差异的响应;内源型、外源型供给的沙堆长、宽间均存在极显著的线性关系(ppp<0.01),其中残积地内沙堆水平尺度与高度间的拟合曲线顺风向几乎无变化,洪积扇下风向样地的则顺风向逐步产生差异。

The sand supply and its richness have long been considered the direct factors in influencing dune morphology. The targeted <i>Caragana microphylla</i> nebkhas are located at three different sites(downwind of alluvial fans, downwind of cultivated land and residual-depositional land) in northern foot of Yinshan Mountain of Inner Mongolian Plateau of China, and its distribution pattern and morphology were systematically measured with a typical quadrat sampling method. The results show that compared with those nebkhas locating at exogenous alluvial fans and cultivated land, the dunes at endogenous residual-depositional land are less in unit area, but the average size is larger. In downwind direction, the morphological parameters in horizontal direction of nebkhas at residual-depositional land are increased slowly and both the height(at vertical direction) of the vegetation and nebkhas has little change, while the parameters are decreased sharply at alluvial fan site. It is believed that the phenomenon is response to the difference of sand movement and quantity caused by relative location between the nabkhas and sand resource. There is an extremely significant linear relationship between the length and width of nebkhas at both endogenous and exogenous area(<i>p</i><0.01), and the fitting lines' slope is increased in the downwind direction. A good correlation also exists between nebkhas height and vegetation height in the two supplying form(<i>p</i><0.05). An extremely significant power function relationship was found between the horizontal parameters and height of the nebkhas on downwind of alluvial fan and residual-depositional land(<i>p</i><0.01), and the fitting curves of horizontal parameters and height of nebkhas change slightly in wind direction at residual-depositional land, while that shows a gradually large variation in wind direction at alluvial fans.

以民勤荒漠绿洲过渡带为研究区,通过样方调查,研究了荒漠区、荒漠绿洲过渡区到绿洲内不同梯度生境中灌丛沙堆的形态特征及分布格局。结果表明:(1)3种生境中灌丛沙堆的形态呈极显著性差异(p&lt;0.01);绿洲区灌丛沙堆的平均高度、底面积、纵横断面积和体积均最大,其次为荒漠区,过渡区最小。(2)过渡带3种生境灌丛沙堆的长、短轴之间均呈二次函数关系,但相关程度不同,过渡区相关性最高,相关系数达0.78;绿洲区相关性最低,相关系数为0.57;高度与底面积、体积与高度间均呈幂函数关系,相关系数均在0.59以上;(3)过渡区灌丛沙堆分布密度较大,呈聚集分布,而荒漠区及绿洲区沙堆分布密度较小,均呈随机分布。

The desert-oasis ecotone in Minqin,Gansu, China was selected as the studied area, and the morphological characteristics and distribution patterns of nebklas in three habitats, just desert, desert-oasis ecotone and oasis were researched by the quadrat survey method. The results are as follows. (1) There were significant differences of the nebklas' morphological characteristics among the different habitats (p<0.01). The average height, bottom area, vertical and cross section and volume of the nebkhas were all the largest in the oasis, followed by the desert, and the last was the desert-oasis ecotone. (2)There was significant quadratic function relationship between the long axis and short axis of nebklas, but with different degree of correlation, the highest was in the desert-oasis ecotone with correlation coefficient value 0.78, while the lowest was in the oasis with correlation coefficient value 0.57. Typical power function relationships were existed between the height and bottom area, and also between the volume and height of the nebklas, the correlation coefficient values were all more than 0.59. (3) The nebklas in the desert-oasis ecotone was presented clustered distribution with much higher distribution density, while in the oasis and the desert area nebklas showed random distribution with lower distribution density.

依据风沙运动实验相似理论,以新疆和田河流域实测的柽柳沙堆形态数据为基础,按40∶1的比例缩小制成半球形和圆锥形模型,并在模型顶部模拟人工“植物灌丛”,选用起沙风速区间在6~14 m\5s-1的5组不同的风速分别对半球形灌丛沙堆模型和圆锥形灌丛沙堆模型在风洞中作纯气流流场模拟实验,以探讨植物在灌丛沙堆绕流结构形成中的作用。模拟实验表明,无论沙堆基本形态如何变化,沙堆顶部的植物都增加了沙堆表面的粗糙度,对翻越沙堆的绕流气流阻滞消能,消除了裸露沙堆顶部常见的强风侵蚀区域,并加强了背风坡涡流影响范围,这种流场结构变化必将影响沙堆前后风沙流的结构特征。因此,植物的存在将更有利于截留沙尘、促进沙堆增长,植物在沙堆发育过程中起着十分重要的作用。

Plants in a dune environment have a high risk of being denudated by wind or buried by sand. We conducted a field experiment to assess growth and reproductive performance as well as biomass allocation of Artemisia ordosica after denudation and burial. Height growth decreased after denudation, but remained constant after burial; biomass was reduced by severe burial, but not by moderate ones. Vegetative growth measured by current‐year generated vegetative branches declined with increasing severity of burial. Reproductive maturity was not affected by either denudation or burial, and reproduction decreased only after severe denudation. After denudation, biomass allocated to reproduction was greatly reduced, as shown by strongly reduced biomass allocation to fruits and whole reproductive branches, but that allocated to current‐year vegetative growth was maintained. Biomass allocation to reproduction and vegetative growth remained rather stable after burial. Current‐year reproductive‐to‐vegetative‐biomass ratio was lower after denudation than after burial, indicating that vegetative growth was more favored by A. ordosica after denudation. These modifications are adaptive in the fluctuating environment of mobile sand dunes where denudation and burial frequently occur.

Question: Phytogenic mounds (nebkhas) ‐ the natural accumulation of wind‐blown sediments within or around the canopies of plants ‐ have been proposed as important structures for locally maintaining high species richness in coastal and arid ecosystems. Nebkhas are assumed to increase habitat heterogeneity, but what is the importance of the nebkha host species relative to other nebkha characteristics in determining the associated plant assemblages? Are some host species more effective in creating diversity hotspots, or does a single species‐area relationship apply to all nebkhas, regardless of host species? Can the influence of the host be ascribed to its indirect effects on abiotic attributes of the nebkha complex?