Date of Award:

8-2026

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Wildland Resources

Committee Chair(s)

Andrew Kulmatiski

Committee

Andrew Kulmatiski

Committee

Karen H. Beard

Committee

Scott B. Jones

Abstract

Across the western United States, pinyon and juniper woodlands are changing with pinyon pine trees dying back while juniper becoming more abundant. Previous studies suggested that pinyon may lose more water during drier periods. But water loss is only part of the story. Water inputs, or how plants absorb water, are also likely to be important, but rarely well understood. To better understand this, we measured how pinyon and juniper absorb water from different soil depths and how actively they lose water through their leaves. Measurements were made over two years at three sites that ranged from more dry to less dry conditions in southern Utah, USA. We found that pinyon is more flexible in absorbing water, it moves its roots more to absorb water from different depths and able to absorb more water when it is available. However, even with flexible rooting distributions, pinyon experienced more water stress and also lost more water than juniper. Results indicate that pinyon uses fast water handling strategies than juniper. These strategies allow pinyon to grow quickly when water is available, but do not provide enough water to pinyon during drought conditions. As droughts and temperatures are expected to increase, our results suggest that pinyon decline and juniper expansion are likely to continue in the coming century.

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