New Mexico Geological Society Annual Spring Meeting — Abstracts

Understanding the interactions between vegetation, hydrology, and soil development is essential for predicting ecosystem responses to climate variability. As part of the Sevilleta Long-Term Ecological Research (SevLTER) Project, this study aims to determine how vegetation type, microtopography and infiltration capacity may systematically impact each other in a semi-arid system. Additionally, we will be investigating the effects of soil characteristics and deep-profile moisture content on relative plant health and resilience to drought. We expect to see significant differences in these ecologic-surface and topography-soil property relationships with spatial heterogeneity in their properties across the Sevilleta National Wildlife Refuge (NWR). Our study will expand upon ongoing SevLTER research by constructing run-off plots with a range of additional ecohydrological monitoring and co-located with meteorological stations. The ultimate goal of our experimental design is to close the water balance at the plot scale, while revealing internal feedbacks inside of the monitored area.

Eight monitoring sites are selected for this study, delineated by dominant vegetation type(s), and chosen for their ability to capture effects of ecological and soil characteristic spatial variation on plant-climate interactions. Six study sites are associated with existing long term Mean Variance Experiments (MVEs) which alter the mean and variance in soil moisture to simulate the effects of increasingly variable precipitation under projected warming climate conditions. These sites include Pinyon-Juniper Savannah, Juniper Savannah, High Plains Grassland (blue grama grass dominated), High Desert Grassland (black grama grass dominated), Shrubland 1 & 2 (creosote bush dominated). The shrub and grassland sites are on a suite of alluvial fans sourced from the granite-cored Los Pinos Mountains, while the existing savannah locations are in limestone-derived soils in narrow arroyos on the flanks of the Los Pinos Mountains. To test soil property related feedbacks systematically, we added two additional site locations on alluvial fan surfaces sourced from the Los Pinos Mountains: Flat Juniper Savannah and Three Biome.

The Three Biome site presents a unique and complex scenario as the only selected study location where black grama (Bouteloua eriopoda) grasses, juniper (Juniperus monosperma) trees, and creosote (Larrea tridentata) bushes coexist within the same region. This site is located on a low slope alluvial fan surface that is at an intermediate age to the surfaces hosting the High Desert and Shrub sites, and the young alluvial fans hosting the High Plains grassland. To determine the causes of inter-species cohabitation and potential eco-hydrological system impacts, three instrumented monitoring plots will be established at this site. Each monitoring plot will be positioned to maximize the presence of one of the three species of interest, while remaining in relatively close proximity at the site.

Each plot will measure 5-meters by 5-meters, oriented with the outflow zone downslope. To fully control run-off, the plots will be enclosed using partially buried sheet metal barriers staked into the ground. At the downslope end of the plot, a small sheet metal lip will be extended into the plot to focus flow toward a discharge-monitoring sharp crested weir that forms the outlet. This weir will be monitored with cameras during flow events and direct water and other transported material into a carboy to be monitored after precipitation events or monthly.

At each plot soil properties will be characterized, and soil water monitoring equipment installed at 15, 30 45, 60, 75 and 100 cm depths. At the existing MVE sites, these installations will be commercial soil moisture and water potential sensors, and at the new Three Biome and Flat Juniper Savannah sites, custom-built soil moisture probes. Core samples will be collected at these depths and the capillary pressure curves will be measured. Additionally, tension infiltrometer and theta probe soil moisture measurements will be taken seasonally at random locations within the plot to capture small-scale variations in infiltration rates and moisture. New meteorological monitoring stations will be established at the Three Biome and Flat Juniper Savannah sites.

Micro-topographic and vegetation changes within each plot will be monitored through high-resolution drone surveys seasonally, and by statically mounted stereo-cameras. Additionally, acoustic monitoring using GPS-synchronized AudioMoth recorders will collect 44 kHz acoustic data, providing additional high- frequency data on physical processes such as precipitation intensity and animal activity.

This experimental setup is designed for long-term ecological research, with initial data collection beginning summer 2025 continuing through at least 2028. The monitoring structures and instrumentation are intended to last through 2040, ensuring extended observation of climate-driven hydrological shifts. By integrating precise physical data collection with a comprehensive suite of hydrological and ecological monitoring tools, this research will contribute to a broader understanding of responses of plant-climate interactions and ecological transition to spatial heterogeneity in soil properties and microtopographic properties in the Sevilleta NWR.