浑善达克沙地植被的生态适应及植物资源特征

浑善达克沙地位于锡林郭勒高原中部，是我国干草原地带最大的一片沙地。由于长期过度利用，导致了草场退化、固定沙丘活化、沙地大面积沙漠化等一系列环境问题，防治沙漠化的进一步扩大已经刻不容缓。本论文的目的是了解沙地植被与环境的生态关系、沙生植物适应沙地环境的特点以及沙地植物资源特征，为在沙漠化防治中选择合适的治沙物种、制定合理的植被恢复方案提供理论依据。论文包括三方面的内容：1 浑善达克沙地丘间低地草本植物群落的分类与排序;2 沙埋对中间锦鸡儿幼苗生长发育的影响;3 浑善达克沙地植物资源分析。 对丘间低地的草本植物群落进行TWINSPAN 分类和DCA 排序结果表明，浑善达克沙地中部研究区域丘间低地植物群落可分成四个主要类型，每个类型各具不同的特点，土壤盐分以及相关的土壤水分因素对群落分布有着显著的影响。在沙地环境中，沙埋是影响植物幼苗存活的一个重要因素。中间锦鸡儿（Caragana intermedia）是浑善达克沙地和毛乌素沙地固定和半固定沙丘上常见的一种沙生灌木。为了研究沙埋对其幼苗的存活以及生长的影响，对出土后生长了一个月的中间锦鸡儿实生苗进行沙埋实验，实验处理有对照、部分沙埋和全埋，结果表明，部分沙埋对中间锦鸡儿幼苗的生长发育没有显著的影响，说明中间锦鸡儿是一个比较耐沙埋的物种，尽管全部沙埋对其幼苗的生长发育产生了显著的抑制。 浑善达克沙地的物种资源丰富，有种子植物约952 种，分布在348 属、75 科中，菊科和禾本科是最大的两个科;草本植物是主要的生活型，有828 种，占物种总数的86.97％;植物的水分生态类型以中生植物最多，有577 种，占物种总数的61.1％，其次为旱生植物291 种，占总数的30.8％;沙地中有优良牧草植物149 种，可用于固沙的植物几十种，有药用价值的植物约301 种。

Effects of the stocking density and body size of the mitten crab (Eriocheir sinensis) on aquatic plant biomass

Experiments in tanks and cages were conducted to examine the effects of stocking density and body size of the Mitten crab (Eriocheir sinensis) on transplanted submersed macrophyte biomass. The early juvenile crab with 7.0 +/-0.6 mm. carapace width (CW) had little effect on plant biomass, regardless of the stocking densities. However, larger crabs (CW: 18.0 +/-2.2,35.0 +/-3.6, and 60.0 +/-5.7 mm) significantly influenced plant biomass, especially at large stocking densities. Predictive models, using crab body size and stocking density, were generated to demonstrate effect of the mitten crab on the changes Of plant biomass. The results indicate that dense mitten crab populations may adversely affect aquatic plant communities, particularly when its animal food resources are scarce.

Natural Anthraquinone Derivatives from a Marine Mangrove Plant-Derived Endophytic Fungus Eurotium rubrum: Structural Elucidation and DPPH Radical Scavenging Activity

There is considerable interest in the isolation of potent radical scavenging compounds from natural resources to treat diseases involving oxidative stress. In this report, four new fungal metabolites including one new bisdihydroanthracenone derivative (1, eurorubrin), two new seco-anthraquinone derivatives [3, 2-O-methyl-9-dehydroxyeurotinone and 4, 2-O-methyl4-O-(alpha-D-ribofuranosyl)-9-dehydroxyeurotinone], and one new anthraquinone glycoside [6,3-O-(alpha-D-ribofuranosyl)questin], were isolated and identified from Eurotium rubrum, an endophytic fungal strain that was isolated from the inner tissue of the stem of the marine mangrove plant Hibiscus tiliaceus. In addition, three known compounds including asperflavin (2), 2-O-methyleurotinone (5), and questin (7) were also isolated and identified. Their structures were elucidated on the basis of spectroscopic analysis. All of the isolated compounds were evaluated for 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity.