科尔沁沙地差巴嘎蒿群落及种群生态特征

对科尔沁不同类型沙地上差巴嘎蒿群落内物种重要值、多样性等生态特征进行分析后,将其划分为3个类型：差巴嘎蒿 1年生植物群聚、差巴嘎蒿 禾草类群丛、冷蒿 黄蒿+禾草类群丛,分别分布于流动、半固定和固定沙地上.随着沙地基质固定程度的增加,差巴嘎蒿群落由差巴嘎蒿-1年生植物群聚(先锋群落、盖度＜10%、多样性指数0.33)演替到差巴嘎蒿-禾草类群丛(盖度30%～35%、多样性指数0.56)再演替到冷蒿 黄蒿＋禾草类群丛(草原群落、盖度40%～45%、多样性指数0.59).在差巴嘎蒿群落演替过程中,差巴嗄蒿种群年龄结构的变化趋势是:在流动沙地上为增长型;在半固定和固定沙地上为衰退型.人工种植5年后差巴嘎蒿种群年龄结构为增长型,人工种植18年后为稳定型.     

内蒙古科尔沁沙地两种沙生植物冷蒿和差不嘎蒿竞争策略的生理生态学依据(英文)

Gas exchange, water relations and leaf chemical characteristics were examined of twodominant psammophytes: Artemisia frigida Willd and A halodendron Turcz. ex Bess in Horqin sandy land, NeiMongol, China under different water regimes. The measurements were conducted by submitting the plantsto five different irrigation levels. A. fTigida was characterized by lower photosynthetic rate (Pn), lowertranspiration rate ( TR and lower shoot water potential (ψuw) relative to A. halodendron. Foliage of A frigdahad higher values of relative water deficit (RWD), bound water content (BWC), ratio of bound water contentto free water content (BWC/FWC) and integrated drought-resistant index (DI than that of A. halodendron.Water relations differed significantly between two species in response to soil water availability. ψw, BWCand BWC/FWC ratio of A halodendron exhibited large variation with gradual decrease of soil moisture.However, in terms of these parameters, A. fRIGIDA was characterized by higher capacity of water holding anddrought tolerance relative to A halodendron. Proline and total soluble sugar contents of A frigida and Ahalodendron tended to increase with decrease of soil moisture and the former had a larger increaseamplitude than the latter. This shows that A frigida has a higher osmotic regulation ability than A halodendron.Under the extreme drought conditions, ψw, RWD, BWC and BWC/FWC of two species were approximate,but soluble proteins degraded largely. A large amount of accumulation of organic matter, proline and totalsoluble sugars were observed in both A halodendron and A frigida. The increase in proline and total solublesugar contents and soluble protein degradation of A frigida far exceeded those of A. halodendron. Webelieve that the accumulated materials at this moment are mostly of nutrient substances available for therecovery of plants after the drought. This is one of the reasons why A halodendron plants died while Afrigida plants survived under extremely drought condition. Our results suggest that these ecophysiologicalfeatures of A frigida are favorable to its growth in the fixed sandy land compared with A halodendron, whichoften lost its dominance due to weak competition for water sources under lower soil water availability andare major factors resulting in replacement of A. halodendron by A. frigida in the later stage of sandyvegetation succession in Horqin.     

Wind-dispersed seed deposition patterns and seedling recruitment of Artemisia halodendron in a moving sandy land

* BACKGROUND AND AIMS: Artemisia halodendron is a native sub-shrub that occurs mainly in moving and semi-fixed sandy lands in Inner Mongolia, China. Information on the spatial patterns of wind-dispersed seed deposition and seedling recruitment of A. halodendron inhabiting moving sandy lands is very limited. The aim of this study was to examine wind-dispersed seed deposition patterns and post-dispersal recruitment of A. halodendron seedlings. * METHODS: The spatial patterns of wind-dispersed seed deposition and seedling recruitment of A. halodendron were examined by investigating the numbers of deposited seeds, emerged and surviving seedlings using sampling points at a range of distances from the parent plant in eight compass directions for two consecutive growing seasons. * KEY RESULTS: Wind-dispersed seed deposition showed considerable variation between directions and years. Wind transported A. halodendron seeds only a few meters away from the parent plant in all eight directions. Seedling emergence and establishment also showed between-direction and between-year variability, but the spatial pattern of seedling distribution differed from that of seed deposition. Only a very small fraction (<1 %) of the deposited seeds emerged in the field and survived for long enough to be included in our seedling censuses at the end of the growing season. * CONCLUSIONS: The spatial variation in wind speed and frequency strongly affects the pattern of seed deposition, although the variation in seed deposition does not determine the spatial pattern of seedling recruitment. Seeds of A. halodendron are not dispersed very well by wind. The low probability of recruitment success for A. halodendron seedlings suggests that this species does not rely on seedling recruitment for its persistence and maintenance of population.     

Water-use process of two desert shrubs along a precipitation gradient in Horqin Sandy Land

Aims The determination of the source of plant water is an important research on the plant-water relationship in arid and semiarid regions and helps to understand the adaptation strategy of desert species to the dry environment. Plant water use pattern affects plant community composition and ecosystem water budget. This study aims to investigate the water use patterns of Caragana microphylla and Artemisia halodendron, two typical shrub species, under altered rainfall conditions in Horqin Sandy Land. Methods Water treatments include ambient rainfall (natural rainfall), 50% increase in rainfall (enhanced rainfall) and 50% decrease in rainfall (reduced rainfall) by artificially intercepting and redistributing natural rainfall. Stable hydrogen and oxygen isotope ratios (δD and δ¹⁸O) were measured for xylem water, rainfall, and soil water in different soil layers (0-120 cm depth). The possible ranges of potential water sources used by C. microphylla and A. halodendron were calculated using the IsoSource model. Important findings 1) Alteration of ambient rainfall mainly affected the soil water condition in the shallow soil (0-30 cm). Increase in rainfall significantly increased the above- and below-ground biomass, and δ¹⁸O values of soil water declined with soil depth. 2) Under the enhanced rainfall treatment, A. halodendron mainly used the soil water in the shallow soil (0-40 cm) and C. microphylla was able to extract water from multiple soil layers. Under the reduced rainfall treatment, both species increasingly relied on extracting water from deeper soil layers, 60-80 cm for A. halodendron and 60-120 cm for C. microphylla. 3) For the natural rainfall treatment, in the wet season, the upper soil water was recharged by rainfall, C. microphylla and A. halodendron extract the shallow soil water (0-60 cm). However, in the dry season, soil water content was dramatically reduced, and main water sources for C. microphylla shifted from topsoil to deeper soil, and A. halodendron can use multiple layers of soil water. In summary, A. halodendron is more capable of exploring deeper soil moisture under reduced rainfall in comparison with C. microphylla, and is likely to be more adaptive to this water-limiting desert environment.     

沙埋对两种沙生植物幼苗生长的影响及其生理响应差异

为了解沙埋对沙生植物生长的影响及其生理响应特征, 比较不同沙生植物耐沙埋能力及其机制, 2010年在内蒙古科尔沁沙地研究了不同深度沙埋下沙蓬(Agriophyllum squarrosum)和盐蒿(Artemisia halodendron)幼苗的存活率、株高等生长特性及其渗透调节物质含量, 保护酶活性和膜透性的变化, 得到以下结果: 沙蓬和盐蒿幼苗均具有较强的耐沙埋能力, 其中沙蓬幼苗最大耐沙埋深度超过幼苗10 cm, 盐蒿幼苗最大耐沙埋深度超过其株高8 cm; 随着沙埋深度增加, 沙蓬和盐蒿幼苗的存活率和株高均显著下降, 沙蓬的下降幅度显著小于盐蒿; 沙埋处理下两种植物均未表现出受水分胁迫, 沙埋导致其光合面积下降, 幼苗顶土困难, 是影响其存活和高生长的主要生态机制; 随着沙埋深度增加, 沙蓬幼苗丙二醛(MDA)含量显著增加, 盐蒿幼苗MDA含量下降, 虽然二者膜透性均呈增加趋势, 但沙蓬膜透性增加幅度显著低于盐蒿, 说明细胞膜受损是导致二者幼苗存活率下降和生长受到抑制的主要生理机制, 沙蓬膜透性受损程度较低是其耐沙埋能力较强的主要生理机制; 沙埋胁迫下, 虽然两种植物都通过提高过氧化物酶活性和脯氨酸含量减轻细胞膜受损程度, 但沙蓬体内超氧化物歧化酶也表现出重要协调作用, 使之酶促系统在保护细胞膜免受胁迫损伤过程中的作用更有效。