Final report: Hydraulic mechanisms of survival and mortality during drought in pinon-juniper woodlands of southwestern USA
- Univ. of New Mexico, Albuquerque, NM (United States)
The goal of this project was to use rainfall manipulation of an intact pinon-juniper woodland in central New Mexico to understand the mechanisms that control the response of these species to extremes of rainfall. Experimental plots were installed in a pinon-juniper woodland at the Sevilleta National Wildlife Refuge and treatments were imposed in August 2007. Treatments consisted of 1) a Drought treatment imposed by diverting approximately 45% of precipitation away from the plot, 2) and Irrigation treatment imposed by applying six 19 mm simulated rainfall events at regular intervals during the growing season, 3) a Cover Control treatment designed to assess the impact of the plastic troughs constructed on Drought plots without imposing the rainfall diversion, and 4) an untreated control that received no modification. Extensive pinon mortality was observed beginning one year after the start of drought treatment on hillslope plots, while a third drought plot on deeper soils did not exhibit pinon mortality until the fifth year of drought treatment. Pinon mortality occurred in the context of high levels of bark beetle activity, motivating the installation of two additional plots in 2010: a control plot and a drought plot built to the same standards as the original treatments but with bark beetle control maintained by pesticide application to the bole of target trees from 2010 - 2016. Although the drought treatment created similar conditions to those experienced on hillslope drought plots, the drought plot with bark beetle control exhibited no pinon mortality for 5 years even in the presence of high regional bark beetle activity in 2012/13. One of the goals of the research was to identify the mechanism of drought-induced mortality in pinon and juniper: 1) mortality due to catastrophic failure of water transport through plant tissues (hydraulic failure), 2) mortality due to limitations in carbon uptake (carbon starvation) and 3) either of the first two mechanisms with the involvement of bark beetles and other pathogens. Data from this study implicate the interaction of hydraulic failure and carbon limitations with bark beetles playing a pivotal role in influencing the timing of mortality. The uncommon nature of this kind of large scale manipulative experiment has motivated widespread use of the data from the various treatments in modeling exercises with several collaborative groups.
- Research Organization:
- Univ. of New Mexico, Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Biological and Environmental Research (BER)
- DOE Contract Number:
- FG02-07ER64393
- OSTI ID:
- 1333275
- Report Number(s):
- DOE-UNM-ER64393
- Country of Publication:
- United States
- Language:
- English
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