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Aeolian sediment transport occurs as a function of, and with feedback to ecosystem changes and disturbances. Many desert grasslands are undergoing rapid changes in vegetation, including the encroachment of woody plants, which alters fire regimes and in turn can change the spatial and temporal patterns of aeolian sediment transport. We investigated aeolian sediment transport and spatial distribution of sediment in the surface soil for 7 years following a prescribed fire using a multiple rare earth element (REE) tracer‐based approach in a shrub‐encroached desert grassland in the northern Chihuahuan desert. Results indicate that even though the aeolian horizontal sediment mass flux increased approximately three‐fold in the first windy season in the burned areas compared to control areas, there were no significant differences after three windy seasons. The soil surface of bare microsites was the major contributor of aeolian sediments in unburned areas (87%), while the shrub microsites contributed the least (<2%) during the observation period. However, after the prescribed fire, the contribution of aeolian sediments from shrub microsites increased considerably (∼40%), indicating post‐fire microsite‐scale sediment redistribution. The findings of this study, which is the first to use multiple REE tracers for multi‐year analysis of the spatial and temporal dynamics of aeolian sediment transport, illustrate how disturbance by prescribed fire can influence aeolian processes and alters dryland soil geomorphology in which distinct soils develop over time at very fine spatial scales of individual plants. Plain Language Summary: In this study, we investigated how soil and nutrients attached to soil particles are transported and redeposited by wind after a prescribed fire using a new tracer method in a desert grassland. Results from this long‐term (7‐years) experiment in a desert grassland in the northern Chihuahuan desert reveal the role of fire in changing the erosional and depositional areas on the soil surface, which in turn determine what vegetation type can dominate the landscape. In a grassland encroached with shrubs, prescribed fire modified soil erosion processes and resulted in a more uniform distribution of nutrients in the landscape, favoring grass recovery. The findings also highlight the role of prescribed fires as an effective grassland management tool. Key Points: First long‐term analysis of post‐fire aeolian sediment transport using multiple rare earth element tracersAeolian transport, fires, and vegetation modify surface processes in which distinct soils develop at very fine spatial scales of individual plantsDemonstrates long‐term changes in the post‐fire shift in aeolian sediment source and sink dynamics in heterogeneous dryland landscapes [ABSTRACT FROM AUTHOR]

Aims: In many mixed grass-shrub ecosystems, increased shrub biomass tends to promote overall carbon storage, but the distribution of carbon pools may be complicated by disturbances such as wildfires. We investigated the spatial distribution of surface soil organic carbon (SOC) and its relative contribution from grasses and shrubs after fires in a grass-shrub transition zone in the northern Chihuahuan Desert, USA.Methods: We used a prescribed fire to create a burned treatment, then collected soil and plant samples. The biogeochemical approaches, geostatistical analyses, and carbon partitioning analyses were used to quantify the SOC and soil δ13C spatial patterns.Results: Before the prescribed fire, up to 98% of the spatial dependence of SOC was autocorrelated at a distance of 1.91 m, corresponding to the approximate average shrub canopy diameter, but the spatial dependence dropped to 81% at a larger autocorrelation distance (3.74 m) two windy seasons after the fire. C4 grasses and C3 shrubs contributed approximately equal amounts of carbon to the surface SOC pool before the prescribed fire. However, C4 grasses became the dominant source of SOC two windy seasons following the fire. For individual microsites, a substantially increased proportion of SOC was derived from C4 grasses at the shrub microsites following the fire.Conclusions: The higher proportion of C4 grasses-derived SOC at the shrub microsites post-fire suggests that SOC may have preferred pathways to move among different microsites following fire disturbance. The distinct spatial distribution patterns of δ13C, and the increased contribution of SOC from grasses may be explained by the rapid recovery of grasses following the fire. Overall, our results provide insights into how fire might be used as a management tool to alter soil carbon pools in the context of shrub encroachment. [ABSTRACT FROM AUTHOR]

The rapid conversion of grasslands into shrublands has been observed in many arid and semiarid regions worldwide. Studies have shown that fire can negatively affect shrub communities and promote resource homogenization, thereby providing some reversibility to the resource heterogeneity induced by shrub encroachment, especially in the early stages of encroachment. Here, we used prescribed fire in a grassland-shrubland transition zone in the northern Chihuahuan Desert to test the hypothesis that fire facilitates the remobilization of nutrient-enriched soil from shrub microsites to grass and bare microsites and thereby reduces the spatial heterogeneity of soil resources. Results show that the shrub microsites had the lowest water content compared to grass and bare microsites after fire, even when rain events occurred. Significant differences of total soil carbon (TC) and total soil nitrogen (TN) among the three microsites were not detected 1 year after the fire. The spatial autocorrelation distance increased from 1 to 2 m, approximately the mean diameter of an individual shrub canopy, to over 5 m 1 year after the fire for TC and TN. Patches of high soil C and N decomposed 1 year after the prescribed fire. Overall, fire stimulates the redistribution of soil C and N from shrub microsites to nutrient-depleted grass and bare microsites, leading to a decrease in spatial heterogeneity of these elements. The redistribution of soil C and N from shrub to grass and bare microsites, coupled with the reduced soil water content under the shrub canopies but not in grass and bare microsites, suggests that fire might influence the competition between shrubs and grasses, leading to a higher grass, compared to shrub, coverage in this ecotone. [ABSTRACT FROM AUTHOR]

Rangelands cover 70% of the world's land surface, and provide critical ecosystem services of primary production, soil carbon storage, and nutrient cycling. These ecosystem services are governed by very fine-scale spatial patterning of soil carbon, nutrients, and plant species at the centimeter-to-meter scales, a phenomenon known as "islands of fertility". Such fine-scale dynamics are challenging to detect with most satellite and manned airborne platforms. Remote sensing from unmanned aerial vehicles (UAVs) provides an alternative option for detecting fine-scale soil nutrient and plant species changes in rangelands tn0020 smaller extents. We demonstrate that a model incorporating the fusion of UAV multispectral and structure-from-motion photogrammetry classifies plant functional types and bare soil cover with an overall accuracy of 95% in rangelands degraded by shrub encroachment and disturbed by fire. We further demonstrate that employing UAV hyperspectral and LiDAR fusion greatly improves upon these results by classifying 9 different plant species and soil fertility microsite types (SFMT) with an overall accuracy of 87%. Among them, creosote bush and black grama, the most important native species in the rangeland, have the highest producer's accuracies at 98% and 94%, respectively. The integration of UAV LiDAR-derived plant height differences was critical in these improvements. Finally, we use synthesis of the UAV datasets with ground-based LiDAR surveys and lab characterization of soils to estimate that the burned rangeland potentially lost 1474 kg/ha of C and 113 kg/ha of N owing to soil erosion processes during the first year after a prescribed fire. However, during the second-year post-fire, grass and plant-interspace SFMT functioned as net sinks for sediment and nutrients and gained approximately 175 kg/ha C and 14 kg/ha N, combined. These results provide important site-specific insight that is relevant to the 423 Mha of grasslands and shrublands that are burned globally each year. While fire, and specifically post-fire erosion, can degrade some rangelands, post-fire plant-soil-nutrient dynamics might provide a competitive advantage to grasses in rangelands degraded by shrub encroachment. These novel UAV and ground-based LiDAR remote sensing approaches thus provide important details towards more accurate accounting of the carbon and nutrients in the soil surface of rangelands. • Rangeland function is influenced by fine-scale patterns of species & soil nutrients. • Range plant-soil-nutrient dynamics require very high spatial & spectral resolution. • UAV multispectral-photogrammetry fusion excels at functional cover classification. • UAV hyperspectral-LiDAR fusion excels at species & soil fertility classification. • LiDAR data detect soil fertility changes from ecological disturbance of fire. [ABSTRACT FROM AUTHOR]