More Like this

1. Fungi Follow Flora, Bacteria Track the Seasons: A Tale of a Changing Landscape

   https://doi.org/10.1007/s00248-025-02568-3  

   Embury, Emily L; Romero-Olivares, Adriana L (December 2025, Microbial Ecology)

   Abstract Microbes play critical roles in dryland ecosystems, driving nutrient cycling, soil stability, and plant interactions. Despite their ecological importance, few studies have examined how microbial communities respond to vegetation changes in arid landscapes. In the northern extent of the Chihuahuan Desert, the encroachment of woody shrubs into grasslands has been occurring since the 1800s, largely driven by extensive livestock grazing and increased drought levels. In this study, we investigated how microbial communities respond to both biotic (i.e., vegetation) and abiotic (i.e., seasonality) factors, how they assemble in a changing landscape, and which taxa may be particularly responsive to shrub encroachment or even facilitating this transformation. We assessed microbial communities using soil surface samples across five distinct seasonal periods in a grassland-to-shrubland gradient in the Jornada Experimental Range in the Chihuahuan Desert through the use of phospholipid fatty-acid analysis and DNA metabarcoding techniques. Our findings reveal that bacterial and fungal biomass are significantly influenced by seasonal changes, with strong correlations to humidity and temperature fluctuations. We also found that fungal community assembly and diversity were highly impacted by vegetation whereas seasons were more impactful on bacteria. Our results support the idea that microbes may be playing a crucial role in facilitating the grassland-to-shrubland transition. Overall, our study highlights the complex interactions between microbial communities and biotic and abiotic factors in dryland systems. These findings are essential for understanding the future of dryland ecosystems undergoing shrub encroachment and provide a critical foundation for guiding restoration efforts, particularly those looking to incorporate microbial-mediated solutions. 

   more » « less
2. Shrub encroachment promotes positive feedbacks from herbivores that reinforce ecosystem change

   https://doi.org/10.1002/ecs2.70483  

   Andreoni, Kieran J; Bestelmeyer, Brandon T; Schooley, Robert L (December 2025, Ecosphere)

   Abstract Herbivores can be drivers of ecosystem change by triggering and reinforcing vegetation transitions. Such processes may be prevalent in drylands with low productivity where herbivore abundances are linked to climate‐driven resource pulses. In the Chihuahuan Desert, ecosystems are being transformed from black grama (Bouteloua eriopoda) grasslands to honey mesquite (Neltuma[formerlyProsopis]glandulosa) shrublands. Domestic livestock, exotic African oryx (Oryx gazella), and native rodents and lagomorphs have all been implicated as drivers of these transitions through multiple mechanisms affecting different plant life stages. Across shrub encroachment gradients, we paired a long‐term (21 years) herbivore exclusion experiment focused on established perennial grasses with field trials measuring herbivory risk for perennial grass seedlings. We evaluated the roles of cattle, oryx, and native herbivores in reducing grass cover, and tested whether herbivore effects on grass cover and seedling mortality varied among ecosystem states (grassland, ecotone, and shrubland). Cattle and African oryx did not contribute strongly to vegetation dynamics. However, long‐term exclusion of rodents and lagomorphs led to two‐to‐threefold increases in perennial grass cover compared to control plots (with open access to all herbivores) in shrub‐encroached states where mesquite shrubs provided these herbivores with cover from predators. Likewise, herbivory of perennial grass seedlings was highest in the shrub‐encroached states and was driven by rodents. Our results indicate that native rodents and lagomorphs exert strong control over perennial grass dynamics, creating positive feedbacks mediated by changes in habitat structure that can reinforce grassland–shrubland transitions in drylands. 

   more » « less
3. Ecogeomorphic Interactions in Drylands: Aeolian Processes

   Fischella, Michael Raymond (October 2024, ProQuest)

   Dryland environments are experiencing shifting ecogeomorphic patterns due to climatic changes and anthropogenic activities, resulting in a shift from grasslands to shrub-dominated landscapes. This dissertation investigates the effects from increasingly variable monsoonal precipitation and ecogeomorphic connectivity on perennial grass growth, litter distribution, and soil organic matter in drylands, with a focus on grass-shrub ecotones. Field experiments were conducted in the Chihuahuan Desert at the Jornada Basin Long-Term Ecological Research (LTER) site using a precipitation manipulation system and connectivity modifiers (ConMods) to assess their effects on plant productivity, recruitment, and soil nutrient distribution. Results show that reducing connectivity, combined with increased monsoonal precipitation, can enhance perennial grass productivity and recruitment, and affect the distribution of soil organic matter and non-photosynthetic vegetation. These findings contribute to our understanding of how aeolian processes and shifting precipitation regimes will shape vegetation patterns and soil properties in dryland environments under future climate scenarios. This research provides insights into potential mitigation strategies for combating shrub encroachment and promoting the sustainability of dryland ecosystems. 

   more » « less
4. Mammalian herbivores reinforce ecological state transitions in the Chihuahuan Desert

   Andreoni, Kieran (May 2024, www.ideals.illinois.edu)

   Woody plant encroachment is a main driver of landscape change in drylands globally. In the Chihuahuan Desert, past livestock overgrazing interacted with prolonged drought to convert vast expanses of black grama (Bouteloua eriopoda) grasslands to honey mesquite (Prosopis glandulosa) shrublands. Such ecosystem state transitions have greatly reduced habitat for grassland wildlife species, increased soil erosion, and inhibited the delivery of ecosystem services to local communities. The potential for wild herbivores to trigger or reinforce shrubland states may be underappreciated, however, and few studies compare herbivory effects across multiple consumer taxa. Here, I address the roles of multiple mammalian herbivores in driving or reinforcing landscape change in the Chihuahuan Desert by examining their effects on plant communities over multiple spatial and temporal scales, as well as across plant life stages. Moreover, I studied these herbivore effects in the context of precipitation pulses, long-term climate influences, competitive interactions, and habitat structure. I used two long-term studies that hierarchically excluded herbivores by body size over 25 years (Herbivore Exclosure Study) and 21 years (Ecotone Study), and a perennial grass seedling herbivory experiment. Native rodents and lagomorphs were especially important in determining grass cover and plant community composition in wet periods and affected perennial grass persistence over multiple life stages. Conversely, during drought, climate drove declines in perennial grass cover, promoting shrub expansion across the landscape. In that shrub-encroached state, native small mammals reinforced grass loss in part because habitat structure provided cover from predators. This research advances our understanding of an underappreciated component of ecosystem change in drylands – small mammal herbivory – and highlights the need to incorporate positive feedbacks from native small mammals into conceptual models of grassland-shrubland transitions. 

   more » « less
5. Connectivity measures across scales differentially influence dryland sediment and seed movement

   https://doi.org/10.1111/rec.14173  

   Turk, Tyler G; Okin, Gregory S; Faist, Akasha M (August 2024, Restoration Ecology)

   Drylands makeup over 40% of the terrestrial land surface area and are highly vulnerable to degradation. The drivers of dryland degradation can lead to shifts in vegetation, such as woody plant encroachment into historic arid grasslands. Encroachment often creates connected bare plant interspaces where wind and water erosion can redistribute resources, including sediment and seeds. Dryland restoration can incorporate methods to reduce these connected pathways, thus mitigating erosion and retaining resources locally. One method to reduce connectivity is through connectivity modifier (ConMod) structures. Quantifying sediment and seeds captured in ConMod structures provides insight into resource movement on the landscape and system‐level resilience. We quantified sediment and germinable seeds captured in ConMods in relation to vegetation along a grassland‐to‐shrubland gradient, measured at multiple scales, in the Northern Chihuahuan desert, United States. We found (1) a significant but weak correlation between ConMod sediment and seed capture; (2) connectivity in the form of bare ground cover at the large and small scale correlated with sediment capture but not seed capture; and (3) sediment and seed capture were both influenced by previously implemented restoration treatments, though differentially. When investigating the capture of different seed functional groups and sizes, we found that grass seed capture increased with proximity to shrubs and that smaller seeds were both captured more frequently and more closely correlated to sediment capture. These findings have implications for the use of ConMods as restoration tools in shrub‐encroached systems. 

   more » « less