Research On Ecological Functions Of Algal Crust In Songnen Grassland

The Songnen grassland is one of northeast Leymus chinensis grassland in China.It hasimportant economic and ecological significance. In recent years,caused by human disturbanceand climate change, The saline-alkalied and desertified phenomenon is becoming more andmore serious.Aboveground vegetation was sparsed. The algal crust is widespread,and it hasimportant ecological functions.This paper selected algal crust in varying degrees of typical saline-alkalied grassland asresearch object.Experiment plots was composed by Leymus chinensis community，Chlorisvirgata community，Artemisia anethifolia community，Suaeda corniculata community andAlkali spot.The ecological functions of the algal crusts was researched: Identified the speciesof cyanobacteria；The relationship of algal crust and undergroud soil,including the content ofsoil pH value、electrical conductivity and exchangeable sodium; The relationship of algalcrust and aboveground vegetation, including the content of vegetation biomass、plant heightand density；Algal crust photosynthetic gas exchange differences; Simulated experiment ofalgal crust in colonization and succession.The results showed that: identified32species of cyanobacteria，Microcoleus vaginatusand Nostoc commune are dominant species；In general, algal crust could reduce pH value、electrical conductivity and exchangeable sodium of surface soil. Algal crust on deeper soilelectrical conductivity are significant relatively, and the pH value and exchangeable sodiumimpact were not significant. Algal crust improved aboveground vegetation biomass, plantheight (except for Suaeda corniculata community). Algal crust is not significant for thevegetation density. Comparison of algal crust in the natural state and restored statephotosynthesis, water is a decisive condition for algal crust photosynthesis. The intensity ofnatural state algal crust group gas exchange was correlated with soil pH value、electricalconductivity and exchangeable sodium negatively，the photosynthesis of algal crust playedan important role in improving soil salinity.For simulation experiment of algal crust incolonization and succession，the filamentous Cyanophyta are dominant, and water plays a keyrole.