Abstract: [Objective] The spatial distribution of aboveground biomass of desert vegetation along with the distance away from riverway in combination with groundwater depth were studied to provide a theoretical basis for restoration and rehabilitation of the ecological environment in arid desert region.[Method] A transect consisting of 20 continuous sample plots (size of 100 m×100 m) was set in September, 2014 at Yingsu section in the lower reaches of TarimRiver. Plant species and total number of trees and shrubs within sample plots together with crown size, plant height and DBH were recorded. According to the biomass model of Populus euphratica and the fresh weight of standard shrub branches, the aboveground biomass was calculated respectively. The sample plots were further divided into four smaller plots (size of 50 m×50 m), and then 6 to 10 even smaller sample plots (size of 1 m×1 m) along the diagonal were randomly selected, the total herbaceous plant species and numbers in each sample plot were recorded, all grasses were harvested to the ground surface to get aboveground biomass. Finally, a fitted function was created according to the relationship between aboveground biomass and groundwater depth, and then the regression equations and regression coefficients were tested for significance.[Result] The results showed that total aboveground biomass, tree aboveground biomass and shrub aboveground biomass were all negatively correlated with the distance to the riverway and with the groundwater depth (P<0.05). Aboveground biomass of shrub firstly increased and then decreased consistently, showing a single peak type. The total aboveground biomass of shrub and herbaceous plants reached 855.06 g·m^-2 when groundwater depth was less than 4 m (0 to 300 m away from the riverway); and 62.45% was reduced (321.08 g·m^-2) when groundwater depth was in range of 4 to 5.5 m (300 to 1 000 m away from the riverway), and 87.11% was reduced (110.19 g·m^-2) when groundwater depth was above 5.5 m (1 000 to 2 000 m to the riverway).[Conclusion] Community structure and aboveground biomass of desert plants varied with the distance to the river and groundwater depth, indicating that groundwater depth significantly affected the spatial distribution pattern of desert vegetation and aboveground biomass. The controlling mechanism in the ecosystem of extreme arid area is quite unique because as the main water source, river in the desert determines the spatial distribution pattern and structure of the desert vegetation.

Key words: aboveground biomass, groundwater depth, desert vegetation, distance away from the riverway, spatial distribution, regression analysis, the lower reaches of Tarim River