摘 要

中国干旱地区地形广袤，幅员辽阔，是世界上受荒漠化危害最严重的国家之一。荒漠生态系统恶化不仅直接影响荒漠区环境和社会经济发展，而且破坏荒漠地区人们的生存和生活条件，甚至威胁国家安全。荒漠化土地常发生区域性结皮，对改善荒漠化土壤有尤为重要的作用。生物结皮和其结皮下面土层的形成，使土壤表面锁水量提高，土壤养分条件得到优化，这些都为了其他植物的大面积生存和繁衍提供了良好的条件。

蓝藻门植物是干旱、半干旱地区生物结皮中藻类的优势类群，蓝藻分泌的有机凝胶体和多聚糖将土壤微粒紧密粘结在一起，成为了一个密致的抗蚀层，因此改变了荒漠化土壤表面结构单一、均匀、疏松的状况，使土壤表面固定化。生长能力是我们在筛选固沙藻种时的一个非常重要的生理指标。而光照条件对藻类进行光合作用、盐分的吸收都有影响。光对藻类的生长繁殖有直接影响和间接影响，同时光还能促进细胞分化、分裂和增长，必须有适合的光照条件才能让藻类正常生长。本研究以荒漠地区分离的几株蓝藻为研究对象，研究其在不同光照强度下的生长能力。通过不同光照条件培养荒漠蓝藻，测定其生物量、类胡萝卜素、可溶性多糖及蛋白质来筛选出最适光强和最佳藻种。以下为本次实验主要结论：

（1）具鞘微鞘藻M.microcoleus-4在两种光强下比爪哇伪枝藻S. javanicum-203和S.javanicum-144更早进入对数增长期，且在中等光强下稳定期的生物量略高于高等光强下的生物量，在中等光强下更早进入衰减期；

（2）在中等光强和高等光强条件下爪哇伪枝藻S.javanicum-144和S.javanicum-203同时进入对数增长期，且S.javanicum-144在两种光强下增长速率无明显差别，在高等光强下更早进入衰减期；

（3）爪哇伪枝藻S.javanicum-203在高等光强下的增长率明显高于中等光强,进入稳定期后在高等光强下的生物量明显高于中等光强，并在高等高等光强下更早达到衰减期；

（4）在中等光强下OD值、生物量、类胡萝卜素含量、蛋白质含量、胞外多糖、胞内多糖的增长率最大的依次为S.javanicum-203、M.microcoleus-4、S.javanicum-203、S.javanicum-203、S.javanicum-203、S.javanicum-203 S.javanicum-144；

（5）在高等光强下OD值、生物量、类胡萝卜素含量、蛋白质含量、胞外多糖、胞内多糖的增长率由大到小依次为S.javanicum-203、S. javanicum-203、S.javanicum-203、S.javanicum-203、S.javanicum-203、M.microcoleus-4。因此筛选出优势种为爪哇伪枝藻S.javanicum-203，其最适光强为高等光强。

关键词：荒漠化，蓝藻，生物结皮，光强

Abstract

As one of the countries that suffer from desertification most in the world, China has a vast arid area. Not only does the degradation of ecosystem in the desert impose direct impact on the environment and social economic development, but it also undermines people’s survival and living conditions, even puts a threat to national security. Soil crusting occurs in some desert regions, playing a crucial role in improving soil desertification. Biological crust and the soil layer formation beneath it is able to increase topsoil water-holding capacity and improve soil nutrient conditions, both of which create a desirable foundation for large-area settlement and reproduction of plant communities.

Cyanophyta is a dominant community of algae for biological crust in arid and semiarid regions since the organic gel and polysaccharide secreted by cyanobacteria facilitate the solid to bond tightly and form a compact resistant layer that will change desert soil’s primitive situation, i.e. single, homogenous, and loose topsoil, and stabilize topsoil. Growing ability remains a significant physical index based on which we select algae species to stabilize the sand. Sunlight plays an effect in both photosynthesis and nutritive salt absorption and assimilation for algae. Sunlight’s impact on algae growth can be divided into direct and indirect impact. Besides, sunlight is also able to promote cell differentiation and control cell division and reproduction, thus the algae won’t grow normally unless given appropriate light intensity. Taking several cyanobacteria collected from the desert area as research object, this paper investigates their growing ability with different light intensities. The desert cyanobacteria cultured based on different lighting conditions are selected to determine the most appropriate light intensity and optimal algae species by measuring their biomass, carotenoid, soluble polysaccharides, and protein. Here are the main results of the research.

(1) M.microcoleus-4 under the two kinds of light intensity than S.javanicum-203 and S.javanicum-144 earlier into the logarithmic growth, and stabilization of biomass under the medium intensity slightly higher than the biomass under higher light intensity, under the medium intensity is more early into the decay period;

(2) Under the condition of the medium intensity and high intensity S.javanicum-144 and S.javanicum-203 into the logarithmic growth at the same time, and S.javanicum-144 growth rate under two kinds of light intensity has no obvious difference, under higher light intensity into the attenuation earlier period;

(3) S.javanicum-203 growth rate of under higher light intensity was obviously higher than that of medium intensity, enter the stability under higher light intensity of the biomass obviously higher than that of moderate intensity, and the higher earlier attained under higher light intensity attenuation;

(4) The OD under the medium intensity, biomass, carotenoid content, protein content, extracellular polysaccharide, the maximum of the growth rate of intracellular polysaccharides of S.javanicum-203,M.microcoleus-4,S.javanicum-203, S.javanicum-203, S.javanicum-203, S.javanicum-203, S.javanicum-144;

(5) The OD under higher light intensity, biomass, carotenoid content, protein content, the growth rate of extracellular polysaccharide, intracellular polysaccharides from big to small in turn for S.javanicum-203, S.javanicum-203, S.javanicum-203, S.javanicum-203, S.javanicum-203, M.microcoleus-4. So select dominant species of S.javanicum- 203, its optimal light intensity is higher light intensity.

Key word: desertification；cyanobacteria；biological crust；light intensity

目录

第一章 绪论 1

1.1我国荒漠化现状 1

1.2 生物结皮 1

1.2.1 生物结皮的概念 1

1.2.2 生物结皮的种类及其形成过程 2

1.2.3 生物结皮的生态功能 2

1.3 荒漠蓝藻结皮 3

1.3.1 荒漠蓝藻的种类及作用 3