【作者】 张国盛；

【导师】 朱金兆； 王林和；

【作者基本信息】 北京林业大学 ， 水土保持与荒漠化防治， 2004， 博士

【摘要】 毛乌素沙地是一个多层次的生态过渡带，也是土地荒漠化较为严重的地区之一。天然分布于毛乌素沙地的灌木树种臭柏、油蒿、沙柳等，对维持当地生态系统的稳定，防治荒漠化土地的扩展起到了重要作用。本论文应用野外实验生态学方法，对天然臭柏群落结构特征；光合和蒸腾作用；根系分布、根量及不定根的发生；天然更新及更新微生境；克隆生长格局以及臭柏灌丛地土壤特性等进行研究，探讨毛乌素沙地天然臭柏群落的稳定性。 天然臭柏群落高度为30～100cm，覆盖度为40％～85％。分为灌木层和草本层，早期群落的物种丰富度较高，后期下降形成纯灌丛林。臭柏灌丛边缘的光合生物量高，生长量约为灌丛中心的3～4倍。臭柏群落依靠其匍匐茎的无限克隆生长来拓展灌丛范围，依靠种子传播实现异地迁移。臭柏为针叶克隆植物，在灌丛边缘3m的范围内，从边缘向灌丛中心，间隔物长度和分枝角度逐渐变大；分枝强度则逐渐变小，并且呈现出指数函数的变化规律。臭柏克隆生长和资源共享特性在维持群落稳定中起着重要作用，来源于同一上级枝的匍匐茎，有不定根的和无不定根的日平均蒸腾速率和气孔导度没有差异，但无不定根匍匐茎的叶水势比有不定根的高。生长在沙丘顶部的臭柏，蒸腾速率比滩地的臭柏低，表明臭柏具有强的蒸腾控制能力。切断与上级匍匐茎的联系后，依靠不定根吸收的地下资源，虽然能够维持匍匐茎的生命，但其生理特性受到了明显的抑制，切断1周后，蒸腾速率仅能达到对照的45％，叶绿素荧光特性差异显著(p＜0.05)。切断后受损程度的大小，主要取决于地上生物量与不定根生物量的比值。臭柏灌丛地土壤养分资源分布具有空间异质性，存在明显的“沃岛”现象。0～5cm土层内的中细粒子(0.25～0.02 cm)臭柏灌丛地比油蒿覆盖区高9％。除速效磷以外，土壤中的有机质、全氮、速效钾、碱解氮等在臭柏灌丛下0～20 cm的土层内相对富集。 分布在滩地的乌柳灌丛地是臭柏天然更新幼苗的保护者，也是臭柏更新最适宜的微生境，乌柳灌丛地拥有臭柏更新幼苗数高达30～50株／m~2。臭柏灌丛的覆盖度虽与乌柳灌丛地相似，表层土壤种子密度达770粒／m~2，但因表层土壤含水量低，种子不能萌发形成幼苗，丧失了种子更新微生境。毛乌素沙地臭柏群落的演替开始于滩地，终止于固定沙丘，演替模式为：乌柳(或其它保护植物)→乌柳+臭柏→臭柏+乌柳→臭柏→油蒿。 臭柏通过其高的水分利用效率、旱生化的叶片构造和水分特征、高细根含量、克隆生长等特性，构成高覆盖度，集中成片分布的景观格局，增强抗干扰能力，维持群落稳定。更多还原

【Abstract】 Mu Us sandland is an ecotone and one of the serious desertification areas. The natural shrubs, such as Sabina vulgaris , Artemisia ordosica, Slix psammophila, are important to keep the stability of the ecosystem and to control the extension of the desertification. It was studied on structure characteristics, photosynthesis, transpiration, roots distribution, root number, generation of adventitious roots, natural regeneration, regenerate setting, clonal growth pattern and soil characteristic of Sabina vulgaris community with field experiment. And the stability of Sabina vulgaris community was discussed.The height and the coverage of the natural Sabina vulgaris community were 30~ 100cm and 40%~85% respectively. The community structure was made up of shrub and herbage synusias. The biodiversity index was high in early succession of community, then declined in upper succession of community and came into being pure shrubs. The ratio of photosynthesis biomass was high in shrub edge. The growth quantity of shrub edge was 3~4 times that of shrub center. Sabina vulgaris community extended its shrub range by infinitely clonal growth of the stolon and moved other areas by the spread of seeds. The internode length and branching angle decreased, while branching intensity increased gradually from inside to outside within the range of 3m from the edge of the shrub to its center along the stolon, and they changed with an exponential model. The characteristics of clonal growth and resources sharing were important to keep stability of community. The transpiration and the stomatal conductance of stolon with and without adventitious roots were same. But the water potential of stolon without adventitious roots was higher than that with adventitious roots. The transpiration of Sabina vulgaris on top of sand dune was lower than that on grassland. After the stolon was severed from the superior stolon, the stolon could maintain life by the adventitious roots absorbing resources, but the physiological characteristics were restrained obviously. After a week of severing, the transpiration was only 45% that of control and the differences of chlorophyll fluorescence characteristics between them were significant (p<0,05) . The ratio of biomass between stolon and adventitious roots was an important index of injured degree. The soil nutrientswere heterogeneously distributed. It has shown an evident phenomenon of "island of fertility" . The medium-fine soil particles(0.25~0.02cm) in Sabina vulgaris shrubs were 9% higher than that in Artemisia ordosica area. The nutrients except available P showed the enrichment oppositely under the layer of 20cm.The ground with Salix cheilophila shrubs was a protector of seedlings and a feasible microenvironment of regenerate Sabina vulgaris. There were 30-50 seedlings per square metre on this ground. The seed density of Sabina vulgaris was 770 seeds per square metre, but the seeds could not bourgeon because of water deficit in topsoil. The succession began on grassland and ended on fixed sand dune in Mu Us. The mode of succession was from Salix cheilophila or protect plants to Salix cheilophila + Sabina vulgaris to Sabina vulgaris + Salix cheilophila to Sabina vulgaris to Artemisia ordosica.The high coverage and concentrative sheet distribution of Sabina vulgaris enhanced anti-jamming and maintained stability of community because of its characteristics, such as high efficiency of water using, the structure of leave fighting a drought, the high content of fine roots and clonal growth.更多还原