ObjectiveThe occurrence of shrub encroachment in typical steppe areas will inevitably change the ecosystem structure and functions. In this paper, researching how the species diversity and biomass of grassland communities response to the shrub encroachment, to provide reference for subsequent management and control of shrub expansion in grassland areas.
MethodWe conducted ecological community survey at shrub encroachment sample sites in Xilin Gol typical steppe area. Based on the characteristics of shrubs and herbaceous communities between shrubs, the typical steppe shrub encroachment index (TSSEI) was proposed and classified the shrub encroachment grade, defined as slightly, moderately, and severely shrub encroachment grassland, respectively. One-way ANOVA, Pearson correlation analysis and LSD multiple comparative analysis were conducted on the shrub characteristic index, the α diversity index of herbaceous community and the biomass of herbaceous community in different shrub encroachment level plots.
ResultThrough analysis, it was found that: (1) there was no significant difference in richness index, Shannon-Wiener index and Simpson diversity index between grade I and grade II shrub encroachment plots, but they were significantly higher than grade III plots. With the development of shrub from moderate to severe, the species diversity of herbaceous community decreases gradually. Though, the species diversity of herbaceous communities was lowest in the severe shrub encroachment plot. (2) There was no significant difference in aboveground biomass and litter quality between shrubs in different shrub encroachment plots; underground biomass and total biomass of shrub interspaces areas were the lowest in grade II and the highest in grade III shrub encroachment plots. The belowground biomass and total biomass of shrub interspaces of grade I plots, have no significant difference with grade II and III shrub plots. (3) TSSEI was negatively correlated with Shannon-Wiener index and Simpson index (P < 0.01), negatively correlated with richness index (P < 0.05), and positively correlated with Pielou evenness index (P < 0.01). There was no significant correlation between TSSEI and aboveground biomass, underground biomass, litter and total biomass of herbaceous community in shrub interspaces.
ConclusionThe results showed that slight and moderate shrub encroachment of typical steppe had no significant effect on species diversity of herbaceous community among shrubs, and severe shrub encroachment would significantly reduce species diversity. The expansion of shrubs had no significant effect on aboveground biomass and litter mass of herbaceous community. The underground biomass and total biomass of herbaceous community in severe shrub encroachment plots were significantly higher than that in moderate plots. The shrub expansion in typical grassland significantly affected the species diversity of herbaceous communities in shrub interspaces area, but had little effect on the biomass of herbaceous communities.
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