Jornada Basin LTER (JRN-LTER-VII, 2019-2020/21) Outcomes Report

1. Intellectual Merit

The Jornada Basin long-term ecological research site (JRN-LTER) is a temperate dryland in southern New Mexico, representative of drylands in the southwest USA and globally. The JRN has experienced dramatic changes in vegetation structure and ecosystem function over the past century. The conversion of perennial grasslands to landscapes dominated by unpalatable, xerophytic shrubs (shrub encroachment), is often accompanied by increases in soil erosion, reduced productivity, and declining biodiversity. Because drylands occupy >40% of the Earth?s land surface, these state changes have important consequences for the provisioning of goods and services to the >1 billion people living in these landscapes.

In this phase of JRN-LTER (NSF Grant #1832194, 2019-2020/21) we explored how landscape spatial heterogeneity evolves in response to disturbance triggers, connectivity-mediated feedbacks, and their interactions with the soil-geomorphic template. We integrated long-term observations and recent theoretical developments to improve a conceptual and predictive framework for drylands to contribute to emerging ecological theory on: (a) alternative states and transient dynamics, (b) ecosystem sensitivity under global change, and (c) cross-scale interactions.  A major outcome of this 2-year project was the initiation of several new experiments that continue as part of JRN-LTER-VII (2021-2024).  

We assessed how predation risk associated with shrub encroachment alters the landscape of fear for desert lagomorphs. Black-tailed jackrabbits and desert cottontails perceive shrub-dominated habitats to be safer, but the mechanisms differ and are contingent on prey body size, escape tactics, and refuge use (Figure 1).

The Nutrient Effects of Aeolian Transport (NEAT) experiment demonstrated how reduced grass cover results in increased wind erosion, loss of soil nutrients, abrasion and burial of plants, and ultimately, elimination of grasses. Once-in-a-generation winds in the Spring of 2019 produced significant excavation and abrasion of grass roots and in some cases complete removal of aboveground grass biomass (Figure 2a). Fractional root exposure was related to grass density and subsequent grass greening (Figure 2b-c).

The connectivity modifier (ConMod) experiment complemented NEAT to examine the multi-scale interactions between wind and water erosion, landform characteristics and plant cover. ConMods initially resulted in increased litter cover, with an increase in perennial grass cover in later years (Figure 3). On alluvial soils, connectivity-mediated plant?soil feedbacks developed that were not persistent (active soils) or did not develop (stable soils). These results are important for global drylands where connectivity-mediated feedbacks can impact plant recovery and state change reversals.

Our results also demonstrated that shrub competition may contribute to grass suppression as an additional feedback mechanism during shrub encroachment (Figure 4). In particular, we found that shrub competition for water in wet years prevented the full growth response seen for grasses not subject to competitive interactions.   

Our Bajada watershed studies used an ecohydrological model of the impacts of climate change and vegetation state-transition on landscape hydrology to show how the connectivity implications of grassland to shrub transitions induce larger variation in hydrological processes than climate change (Figure 5). This is due to the strong role of increasing bare soil during woody plant encroachment on runoff responses, compared to the effect of larger rainfall events in a warmer world.

We reviewed literature on dryland systems and their role in future carbon sequestration and climate management. Global drylands contain ~30% of global terrestrial carbon stocks, demonstrating the significance of dryland carbon reserves and importance for global carbon management. Dryland carbon storage capacity is correlated with water availability and future aridity patterns (Figure 6). Future management of dryland carbon should consider local ecological contexts, while ensuring ecological integrity of dryland systems and provision of critical services to dryland populations.

2. Broader Impacts

The JRN-LTER continues to publish high-impact research in leading ecological and interdisciplinary journals, including Nature, Ecology and Evolution, Global Change Biology, and other journals. Peer-reviewed articles totaled 105 during the 2019-2021 period.

From 2019-2021, 49,273 K-12 students increased their understanding of the Chihuahuan Desert and LTER research. Almost 2,000 students gained skills in interpreting long-term datasets through the Desert Data Jam. We adapted to COVID-19 school closures by creating new lesson plans, which have been made available to teachers virtually, and a video series guiding students through hands-on learning. These videos are featured on the local school district's YouTube channel and our outreach partner's website (www.asombro.org/onedayinthedesert).

Information Management was a focus for 2019-2021 and has led to major transformation in how we manage, archive, and distribute data. This includes a new website (https://lter.jornada.nmsu.edu/) with immediate access to current and historical climate data, and other datasets. More particularly, our new IM team has updated and submitted hundreds of datasets to the EDI repository. We believe our data management systems, and diverse options to access data, now place us in the forefront of data distribution for the LTER network.

Last Modified: 02/14/2022
Modified by: Niall P Hanan