Quantifying soil surface change in degraded drylands: Shrub encroachment and effects of fire and vegetation removal in a desert grassland

Woody plant encroachment, a worldwide phenomenon, is a major driver of land degradation in desert grasslands. Woody plant encroachment by shrub functional types ultimately leads to the formation of a patchy landscape with fertile shrub patches interspaced with nutrient-depleted bare soil patches. This is considered to be an irreversible process of land and soil degradation. Recent studies have indicated that in the early stages of shrub encroachment, when there is sufficient herbaceous connectivity, fires (prescribed or natural) might provide some reversibility to the shrub encroachment process by negatively affecting shrub demography and homogenizing soil resources across patches within weeks to months after burning. A comprehensive understanding of longer term changes in microtopography and spatial patterning of soil properties following fire in shrub-encroached grasslands is desirable. Here, we investigate the changes in microtopography with LiDAR (light detection and ranging), vegetation recovery, and spatial pattering of soil properties in replicated burned, clipped, and control areas in a shrub-grass transition zone in the northern Chihuahuan Desert four years after prescribed fire or clipping. Results indicate a greater homogeneity in soil, microtopography, and vegetation patterning on burned relative to clipped and control treatments. Findings provide further evidence that disturbance by prescribed fire may allow for reversal of the shrub encroachment process, if the event occurs in the early stages of the vegetation shift. Improved understanding of longer-term effects of fire and associated changes in soil patterning can inform the use and role of fire in the context of changing disturbance regimes and climate.