Above-and below-ground microenvironmental attributes cluster to varying degrees around Wyoming Big Sagebrush canopies

Authors: KOUTZOUKIS, SOFIA - Utah State University; Monaco, Thomas; BEBLEN, KARI - Utah State University

Submitted to: Ecosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/9/2025
Publication Date: 9/15/2025
Citation: Koutzoukis, S., Monaco, T.A., Veblen, K.E. 2025. Above-and below-ground microenvironmental attributes cluster to varying degrees around Wyoming Big Sagebrush canopies. Ecosphere. https://doi.org/10.1002/ecs2.70396.
DOI: https://doi.org/10.1002/ecs2.70396

Interpretive Summary: The mosaic of bare ground and heterogeneous vegetation are considered critical for the establishment of under story species. “Shrub islands” can create favorable conditions for plant establishment and persistence near the shrub canopy relative to the inter space area between shrubs. This study hypothesized that favorable aboveground environmental attributes would tightly cluster around sagebrush canopies whereas favorable below ground attributes would be more diffuse and extend farther from the canopy into the inter space. At four sites across the Inter mountain West, we sampled aboveground (i.e., solar radiation and vapor pressure deficit) and below ground (i.e., soil organic matter, moisture content, potassium, phosphorus) attributes at four micro sites away from the main stem of big sagebrush (Artemisia tridentata Nutt.): the canopy edge, maximum inter space distance between neighboring sagebrush canopy edges, and two intermediate distances between these extremes (25% and 50% of the intervening distance). Solar radiation (above ground attribute) and soil potassium (below ground attribute) levels generally were abruptly different between the canopy and the nearest (25%) inter space micro site, indicative of clustering of these resources around the canopy. In contrast, inter space levels for the below ground soil attributes of organic matter, soil moisture, and the above ground attribute vapor pressure deficit, tended to change more gradually with distance from canopy, consistent with a more diffuse pattern, whereas phosphorous did not differ significantly across micro sites. These results reveal that some favorable shrub aspects of shrub canopies do not extend beyond the canopy, whereas others diminish with distance from canopy. These results support the conclusion that a simplistic “canopy versus inter space” dichotomy is no longer valid when describing shrub island dynamics.

Technical Abstract: Micro sites beneath shrub canopies in dry land landscapes characterized by a mosaic of bare ground and heterogeneous vegetation are often considered critical for the establishment of under story species.“Shrub islands” can create favorable environmental conditions for plant establishment and persistence near the shrub canopy relative to the inter space area between shrubs. However, the degree to which favorable conditions cluster around canopies and whether specific environmental attributes remain elevated at intermediate distances between the canopy maximum and inter space micro sites is understudied. If environmental attributes do not strongly cluster around shrub canopies, the inter space region beyond canopies may provide at least partially favorable conditions for establishment or persistence of under story plants. We hypothesized that favorable aboveground environmental attributes would tightly cluster around sagebrush canopies whereas favorable below ground attributes would be more diffuse and extend farther from the canopy into the inter space. At four sites across the Inter mountain West, we sampled aboveground (i.e., solar radiation and vapor pressure deficit) and below ground (i.e., soil organic matter, moisture content, potassium, phosphorus) attributes at four micro sites associated with big sagebrush (Artemisia tridentata Nutt.): the canopy edge, maximum inter space distance between neighboring sagebrush canopy edges, and two intermediate distances between these extremes (25% and 50% of the intervening distance). Despite high site-to-site variation of all attributes, solar radiation (aboveground attribute) and soil potassium (below ground attribute) levels generally were abruptly different between the canopy and the nearest (25%) inter space micro site, indicative of clustering of these resources around the canopy. Inter space levels for the below ground soil attributes of organic matter, soil moisture, and the above ground attribute vapor pressure deficit, tended to change more gradually with distance from canopy, consistent with a more diffuse pattern, whereas phosphorous did not differ significantly across micro sites.