Plant water use strategies in the Shapotou artificial sand-fixed vegetation of the southeastern margin of the Tengger Desert, northwestern China

Stable oxygen and hydrogen isotopic compositions(δ^(18)O and δD) of plant xylem water and its potential water sources can provide new information for studying water sources, competitive interactions and water use patterns of plants. The contributions of different water sources to three plants, Hedysarum scoparium(HS), Caragana Korshinskii(CK) and Artemisia ordosica(AO), were investigated in the artificial sand-fixed vegetation of Shapotou, the southeastern margin of the Tengger Desert of northwestern China, based on meteorological data and δ^(18)O and δD values of precipitation, groundwater, soil water and xylem water of HS, CK and AO. Our results indicated that soil water infiltration through precipitation was the main water source of the artificial sand-fixed vegetation. Obvious differences in soil water content and in δ^(18)O of soil water and xylem water were found among different seasons. No relationship was found between the δ^(18)O in plant xylem water and in soil water in January. The same water use patterns were found in CK, HS and AO in May, suggesting they have the same water sources. The different water sources of CK, HS and AO in August indicate that water competition occurred. In addition, the main water sources of CK, HS and AO in August mainly come from shallow soil water, while they use relatively deep soil water in May. This phenomenon is related to the differences of soil water content throughout soil profile, precipitation, transpiration and water competition under different growth periods. The water use patterns of CK, HS and AO respond to soil water content throughout the soil profile and their competition balance for water uptake during different growth season. The results indicate that these sandfixed plants have developed into a relatively stable stage and they are able to regulate their water use behavior as a response to the environmental conditions, which reinforces the effectiveness of plantation of native shrubs without irrigation in degraded areas.

Soil restoration research advances of artificial sand-binding vegetation ecosystem in the Tengger Desert, Northern China

Soil plays an important role in desert ecosystem, and is vital in constructing a steady desert ecosystem. The management and restoration of desertified land have been the focus of much discussion. The soil in Shapotou desert region has developed remarkably since artificial sand-binding vegetation established in 1946. The longer the period of dune stabilization, the greater the thickness of microbiotic crusts and subsoil. Meanwhile, proportion of silt and clay increased significantly, and soil bulk density declinced. The content of soil organic matter, N, P, and K similarly increased. Therefore, soil has developed from aeolian sand soil to Calcic-Orthic aridisols. This paper discusses the effects brought about by dust, microbiotic soil crust and soil microbes on soil-forming process. Then, we analyzed the relation between soil formation and sand-binding vegetation evolution, in order to provide a baseline for both research on desert ecosystem recovery and ecological environment governance in arid and semi-arid areas.

宁夏沙坡头国家级自然保护区流动沙丘移动与固定沙地风蚀的研究

【目的】深入探究宁夏沙坡头国家级自然保护区流动沙丘营建植被后土壤风蚀抑制效率的定量关系,以期为我国干旱区制定合理的防风固沙方案提供理论依据。【方法】在宁夏沙坡头国家级自然保护区内3处流动沙丘各设置3个观测点,采取插钎法观测流动沙丘的移动;同时在保护区3处固定沙地采集栽植沙柳地段、栽植樟子松地段与栽植油蒿、花棒、柠条地段的原状土和各自对照的原状土开展室内风洞实验,风洞内观测在不同风速下的吹蚀变化。【结果】宁夏沙坡头国家级自然保护区流动沙丘一个风季平均前移3.23 m。风洞内不同风速吹蚀下,栽植沙柳地段样地土样的风蚀模数与对照相比,在风速为15 m/s时减少96.78%,在风速为20 m/s时减少97.07%;在10、15、20 m/s的风速吹蚀下,栽植樟子松地段样地土样的风蚀模数分别比对照减少53.13%、99.61%、99.84%,栽植油蒿、花棒、柠条地段样地土样的风蚀模数分别比对照减少50.00%、65.01%、3.65%。【结论】流动沙丘采用机械草方格固定后栽植人工植被能够促进地表生物结皮形成,进而土壤风蚀大为减弱。在干旱半干旱区进行植物固沙工作时要高度重视生物结皮的防治土壤风蚀的作用,以促进我国的生态恢复。

不同固沙区结皮中微生物生物量和数量的比较研究

沙地生态系统是温带干旱区、半干旱区的重要草地类型,沙地的稳定性是生态系统健康的重要条件。在中国科学院沙坡头沙漠试验研究站,笔者对不同程度固沙区结皮和流动沙丘表层中的微生物生物量和数量进行了比较研究。结果表明:自然和人工植被固沙区结皮及流沙表层的微生物数量分布不同,细菌数量比真菌和放线菌数量多数百倍,在所有微生物类群中,细菌数量最大,微生物总数的变化取决于好气性细菌数量的多少,但生物量却与之不同。在不同程度固沙区结皮中,微生物生物量大小依次排列为:自然植被区>1956年人工植被区>1964年人工植被区>1982年人工植被区>流沙区,微生物生物量在自然植被固沙区中最多,分别是1956年、1964年、1982年人工植被固沙区和流沙区的2 63、4 17、9 25和44 29倍,表明微生物生物量随人工植被的栽植年代增加而增大,在流动沙丘中最小,而菌丝生物量方面是1956年人工植被固沙区已与自然植被固沙区十分接近。微生物生物量和数量与沙丘固定程度、人工植被栽植年代、结皮厚度、苔藓种类等均呈正相关,人工植被栽植年代越长,结皮越厚、微生物生物量和数量也越大。在不同年代人工植被固沙区结皮中,微生物生物量和数量与相对稳定的自然植被固沙区相比,仍未达到稳定状态。

沙坡头人工固沙区草本层片结构组成与群落演替规律分析

对腾格里沙漠沙坡头人工固沙区草本植物带群落的结构组成进行了分析，结果表明，６０年代以前的固沙植被区已进入演替的亚顶极群落，群落多样性、均匀度值均达相对最大，优势度最低。草本层片的种类组成以小画眉草（Ｅｒｏｇｒｏｓｔｉｓｐｏａｅｏｉｄｅｓ）和雾冰黎（Ｂａｓｉａｄａｓｙｐｈｙｌａ）为主，伴生虫实（Ｃｏｒｉｓｐｅｒｍｕｍｓｐ．）、虎尾草（Ｃｈｌｏｒｉｓｖｉｒ－ｇａｔａ）和狗尾草（Ｓｅｔａｒｉａｖｉｒｉｄｉｓ）等的一年生草本。固沙区受到扰动（沙面被破坏）后因其固沙年限和干扰程度的不同，群落将在原基础上开始其初始状态不同而终局相同的演替历程。

沙坡头人工植被变化的动态平衡

沙坡头地处腾格里沙漠的东南缘,属于宁夏回族自治区中卫县。该地区自然条件严酷,沙丘起伏大,沙层深厚,格状沙丘由西北向东南倾斜且呈阶梯状分布。地下水位深达几十甚至10Om以上,有机质、碳酸钙和速效性养分含量都很低,pH值7.14一7.60。

沙坡头人工植被组成分析

本文根据多年的植被调查和沙层水分动态的观测资料,对沙坡头地区无灌溉条件下人工植被33年演变过程中的组成进行分析。结果表明:(1)目前,人工植被已经演变为以油蒿为主的灌木半灌木+一年生草本+孢子植物占优势的人工——天然植被。(2)人工植被的生活型以高位芽植物和一年生植物为主,辅以少量的地面芽植物,没有地上芽和隐芽植物,生活型谱不完整。与天然油蒿群落比较,人工植被种类少、投影盖度低、根栖层水分严重亏缺。(3)投影盖度是荒漠半荒漠植被最重要的特征之一。人工植被演变初期投影盖度波动性上升。7—16龄为鼎盛时期,投影盖度为30%左右。随后又波动性下降。这种波动性变化规律在判断沙漠化程度时有意义。(4)人工植被演变过程中Shannon-Wiener多样性指数的变化规律近似“∩”型。种优势度指数的变化规律与其成负相关,近似“U”型。(5)流沙群落、3—33龄的人工植被的种多度分布模式为几何级数型。天然油蒿群落和红砂—珍珠群落为对数正态分布。1—2龄的人工植被种多度分布模式完全受人为因素的制约。

沙坡头人工固沙植被生态系统土壤恢复研究进展

土壤是荒漠生态系统的重要组成部分,沙化土地的治理与恢复是人们关注的重点。沙坡头人工固沙植被区的土壤经过50 a的恢复,已得到显著的发育。结皮及亚表土层厚度随固沙年代的增加而增大,土壤颗粒组成中粘粒和粉粒含量增多,土壤容重降低,有机质和氮、磷、钾等营养元素含量增加,流动风沙土已发育成为钙积旱成土。本文探讨了降尘、生物土壤结皮和土壤微生物对土壤恢复的影响,分析土壤发育与人工植被演替的相互作用,并提出了今后的研究重点方向。