Rainfall Distribution Study

Rainout Shelters One of the challenges of living and working in the Great Basin is the variable climate. However, there has been surpisingly little research on the effect of weather variation on rangeland vegetation. The difficulty in manipulating weather is part of the reason for the lack of prior research. One can attempt to document year-to-year changes in vegetation and relate the changes back to weather patterns. However, this approach requires very long time frames and there is still the problem of many variables to sort out (weather is more complex than just rainfall and temperature).

In this study we chose to focus on one question, "How does precipitation timing influence Great Basin vegetation?" This is a difficult subject to study because one cannot easily manipulate precipitation timing. Our approach was to exclude all precipitation with fixed location rain shelters and use an overhead sprinkler system to "rain on" three different zones under each rain shelter at the desired time.

Layout of Plots at Rainout Shelter We have five 30'x100' rain shelters each with three 30'x30' zones to which rain is applied at different times. Our three rainfall treatments (zones) are : 1) average current rainfall distribution, 2) a higher proportion of rainfall during winter, and 3) a higher proportion of rainfall during the spring. All three treatments recieve the same amount of precipitation.

Our measurements include variables such as plant development and productivity, species composition and cover, rooting activity, reproductive output, and soil moisture and nitrogen.

We hope the results of this study will help land managers better understand the impacts of weather on vegetation trends. Managers are faced with the challenge of separating the effects of weather from those induced by management. We also know that the Great Basin has undergone large changes in weather patterns in the past and will likely do so in the future. The results of this study might help us predict how climatic shifts will influence vegetation.

If you would like more information on this, contact Tony Svejcar , Jon Bates , Rick Miller , or Ray Angell.