Spatial Variability of Agriophyllum squarrosum Across Scales and Along the Slope on an Active Sand Dune in Semi-Arid China

Abstract

Spatial variability has been recognized as a critical issue in vegetation restoration, and this condition is favorable for understanding underlying ecological processes or mechanisms. To assess the potential effects of spatial scales and environmental factors on vegetation patterns on active sand dunes, a 0.25 ha (50 m × 50 m) sampling plot was selected on the windward slope of an active sand dune to analyze the spatial variability of annual psammophyte Agriophyllum squarrosum across scales and along the slope. The average density, coverage, and height of A. squarrosum seedlings at five grain sizes (from 1 m × 1 m to 25 m × 25 m) as well as along the slope were measured. In A. squarrosum community, density, coverage, and height had the highest values at fine scales, but the lowest values at coarse scales. The highest value decreased gradually as scale increased, which means spatial variability gradually decreased as grain size increased. The correlations between density and height as well as between density and coverage decreased with increasing spatial scale, whereas the correlations between height and coverage increased. In regards to the slope, the seedlings of A. squarrosum developed better on top, and the Pearson correlation coefficients between plant density and height, as well as between density and coverage decreased in a fluctuating manner from the top to the bottom. In conclusion, grain size is an important consideration in the analysis of vegetation variability. Moreover, disturbances in sand dunes, such as wind erosion, should be further considered and discussed in the study of vegetation restoration and biodiversity conservation in active sand dunes.