新疆古尔班通古特沙漠南部沙垄不同部位藻类的垂直分布特征

VERTICAL DISTRIBUTION OF ALGAE IN DIFFERENT LOCATIONS OF SAND DUNES IN THE GURBANTUNGGUT DESERT,XINJIANG,CHINA

通过2005和2006年夏季两次对新疆古尔班通古特沙漠南部荒漠土壤中藻类植物进行采样、培养、鉴定和生物量测定，分析了该区沙漠沙垄不同部位藻类物种组成、优势种和生物量的垂直变化。结果表明：1）在不同地貌部位的不同层次中，藻类的种类组成均有所差异。2）藻类优势物种主要集中在0～2cm层次中，2cm以下的土层中藻类细胞很少，绝大部分土层以具鞘微鞘藻（Microcoleus vaginatus）为第一优势种，有些部位的土层中第一优势种是伪双点颤藻（Osdllatoria pseudogeminata），如垄间低地和迎风坡的1～2cm中。此外，大型集胞藻（Synechocystis crassa）、舟形藻（Navicula sp．）、卵圆双眉藻（Amphora ovolis）数量也较多。3）除垄顶外，藻类生物量在其它3个部位不同层次的差异呈极显著水平（P〈0．01），生物量由表及里锐减；在同一土层，藻类生物量基本表现为垄间低地最高，迎风坡与背风坡居中，垄顶最低，不同地貌部位对藻类生物量影响呈显著或极显著水平。

Aims It is well known that desert algae play significant and irreplaceable roles in the early formation and structural maintenance of the biological soil crusts. Although species composition and community structure of algae have been widely studied, only a few investigations have been made on the vertical distribution of soil algae in deserts. Our objective was to further reveal species community structure and ecological distribution of desert algae in vertical layers. Methods We selected typical sand dunes in the Third Site of the southern Gurbantunggut Desert and collected 112 soil samples twice in summers of 2005 and 2006. Using a fixed section from different locations of the sand dunes, we gathered soil samples at serial sections of 0 - 0.5,0.5 - 1,1 - 2, 2 - 5 cm depth respectively. Algae species were identified by direct microscopic observation and liquid culture observation （dominant species were identified by direct observation）. Each sample was checked three times, with ten observations for each sample. Algae biomass was determined by measurement of chlorophyll a. Important findings Algae species composition differ among soil layers. Dominant algae species are mainly in the 0 - 2 em layers and seldom exist in lower layers. The most dominant algae species in most layers is Microcoleus vaginatus. In 1 - 2 em layers of interdune and windward, Oscillatoria pseudogeminata is the most dominant. In addition, Synechocystis crassa, Navieula sp. and Amphora ovalis are more dominant than other algae. Except for the top of sand dunes, algae biomass in different layers exhibited highly significant differences （p 〈 0.01） at other locations. Algal biomass dramatically decreased with soil depth from the surface to lower levels. At the same soil depths, algae biomass declined from the inter dune position to the windward and leeward, to the top, with differences highly significant （p 〈0.01） or significant （p 〈0.05）.