Desert icon Joshua trees are vanishing, scientists say

Download story podcast
11:36 PM PDT on Saturday, June 20, 2009
By JANET ZIMMERMANThe Press-Enterprise

Kurt Miller / The Press-Enterprise
Mike Cipra, a desert program manager for the National Parks Conservation Association, examines a burned Joshua tree that shows signs of growth earlier this month. Scientists say the effects of global warming could make Joshuas extinct within a century.

A breeze stirs the silence at Joshua Tree National Park as a red-tailed hawk takes flight from the spiky arm of one of the namesake plants in search of breakfast.

It's a scene that national parks protector Mike Cipra has witnessed many times. Still, he can't contain his enthusiasm on this early morning outing, despite the gloomy topic he's discussing with a visitor -- the probable extinction of the Joshua tree in the park that bears its name.

The ancient plants are dying in the park, the southern-most boundary of their limited growing region, scientists say. Already finicky reproducers, Joshua trees are the victim of global warming and its symptoms -- including fire and drought -- plus pollution and the proliferation of non-native plants. Experts expect the Joshuas to vanish entirely from the southern half of the state within a century

Read more:

Instrumentation enabling study of plant physiological response to elevated nighttime temperature

Global climate warming can affect functioning of crops and plants in the natural environment. In order to study the effects of global warming, a method for applying a controlled heating treatment to plant canopies in the open field or in the greenhouse is needed that can accept either square wave application of elevated temperature or a complex prescribed diurnal or seasonal temperature regime.

The current options are limited in their accuracy, precision, reliability, mobility or cost and scalability.

Results: The described system uses overhead infrared heaters that are relatively inexpensive and are accurate and precise in rapidly controlling the temperature. Remote computer-based data acquisition and control via the internet provides the ability to use complex temperature regimes and real-time monitoring.

Due to its easy mobility, the heating system can randomly be allotted in the open field or in the greenhouse within the experimental setup. The apparatus has been successfully applied to study the response of rice to high night temperatures.

Air temperatures were maintained within the set points + 0.5 oC. The incorporation of the combination of air-situated thermocouples, autotuned proportional integrative derivative temperature controllers and phase angled fired silicon controlled rectifier power controllers provides very fast proportional heating action (i.e.9 ms time base), which avoids prolonged or intense heating of the plant material.

Conclusion: The described infrared heating system meets the utilitarian requirements of a heating system for plant physiology studies in that the elevated temperature can be accurately, precisely, and reliably controlled with minimal perturbation of other environmental factors.

Author: Abdul MohammedLee TarpleyCredits/Source: Plant Methods 2009, 5:7