An official website of the United States government
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
Connectivity measures across scales differentially influence dryland sediment and seed movement
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
- Award ID(s):
- 2425143
- PAR ID:
- 10661700
- Publisher / Repository:
- Society for Ecological Restoration
- Date Published:
- Journal Name:
- Restoration Ecology
- Volume:
- 32
- Issue:
- 6
- ISSN:
- 1061-2971
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
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
-
Abstract Hydrologic connectivity refers to the processes and thresholds leading to water transport across a landscape. In dryland ecosystems, runoff production is mediated by the arrangement of vegetation and bare soil patches on hillslopes and the properties of ephemeral channels. In this study, we used runoff measurements at multiple scales in a small (4.67 ha) mixed shrubland catchment of the Chihuahuan Desert to identify controls on and thresholds of hillslope‐channel connectivity. By relating short‐ and long‐term hydrologic records, we also addressed whether observed changes in outlet discharge since 1977 were linked to modifications in hydrologic connectivity. Hillslope runoff production was controlled by the maximum rainfall intensity occurring in a 30‐min interval (I30), with small‐to‐negligible effects of antecedent surface soil moisture, vegetation cover, or slope aspect. AnI30threshold of nearly 10 mm/h activated runoff propagation from the shrubland hillslopes and through the main ephemeral channel, whereas anI30threshold of about 16 mm/h was required for discharge from the catchment outlet. Since storms rarely exceedI30, full hillslope‐channel connectivity occurs infrequently in the mixed shrubland, leading to <2% of the annual precipitation being converted into outlet discharge. Progressive decreases in outlet discharge since 1977 could not be explained by variations in precipitation metrics, includingI30, or the process of woody plant encroachment. Instead, channel modifications from the buildup of sediment behind measurement flumes may have increased transmission losses and reduced outlet discharge. Thus, alterations in channel properties can play an important role in the long‐term (45‐year) variations of rainfall–runoff dynamics of small desert catchments.more » « less
-
This dataset contains water year precipitation collected from meteorological stations, litter and vegetation cover values derived from overhead photos, and litter and soil accumulation in lateral photos in a long-term experiment (2013-2021) of cross-scale interactions (CSIs) at the Jornada Basin LTER site in southern New Mexico, U.S.A. Manipulations were initiated in 2013 at 15 experimental blocks, each with 4 treatment plots: plant-scale herbicide of mesquite shrubs, patch-scale connectivity modifiers (ConMods), herbicide + ConMods, control without manipulations. Litter, soil, and vegetation cover were estimated using repeat overhead photographs of microplots within treatment and control plots. Litter and soil accumulation were estimated from lateral photos of ConMods. This dataset utilized QuickBird imagery from 2011 to assess ground cover classes within the Jornada Basin, focusing on bare ground, herbaceous, and shrub cover. Daily precipitation data collected from 13 meteorological stations were used to calculate water year (1 October-30 September) precipitation from 2013 through 2021. This dataset provides supporting data for the manuscript "Growing grasses in the desert: Multi-scale Interactions and State Change Reversal in Drylands" by Peters et al.more » « less
-
Abstract Vegetation change in drylands can influence wind erosion and sand and dust storms (SDS) with far‐reaching consequences for Earth systems and society. Although vegetation is recognized as an important control on wind erosion and SDS, the interactions are not well described at the landscape level or in the context of dryland ecosystem change. The transition of sites from one ecological state to another (e.g., grassland to shrubland) is typically associated with changes in the composition, cover, and structure of vegetation, which influence drag partitioning and wind shear velocities that drive aeolian sediment transport. Here, we quantify the magnitude and direction of aeolian sediment transport responses to ecological state change in the northern Chihuahuan Desert and identify thresholds associated with state transitions. Our results show aeolian sediment mass flux (Q) increased from ∼1 to 10 g m−1 d−1in historical grassland with scattered shrubs to ∼10–100 g m−1 d−1following shrub invasion and decline in perennial grass cover to ∼100–10,000 g m−1 d−1in shrubland following complete grass loss. The magnitude shifts were associated with critical perennial grass cover thresholds governing nonlinear increases inQacross ecological state transitions. Grass recovery in shrubland reducedQto rates similar to those in historical grasslands—a multiple order of magnitude reduction. Our results show that crossing degradation and restoration thresholds between alternative ecological states can have a profound effect on the magnitude and spatiotemporal variability of aeolian sediment transport and primacy in determining patterns of wind erosion and dust emissions in vegetated drylands.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1111/rec.14173
