Plants in extreme desert environments must adapt to their harsh and relentless conditions in order to survive. It's difficult enough when they are the only species in the area, and their job becomes even more difficult when they are forced to compete with other species for scarce resources.
Researchers at the University of Arizona studied the effects of competition and efficiency of water usage on plants in the Sonoran desert, a large desert area stretching through parts of Arizona, California, and northwestern Mexico. Their findings, recently published in the American Journal of Botany, showed that data on growth rate and water usage within a species of plant might be used to predict the plant's response to a scarcity of resources.
Natural variations in rainfall and water retention from year to year and from area to area produce different results in the plant population, with species that are efficient in their water usage succeeding well in dry years and areas but faring more poorly in wet years and areas. During this time, they may be crowded out by fast-growing species that thrive under the wetter conditions.
These conditions may be exacerbated in the desert, where a plant population may face long periods of extreme drought, or torrential short-term rains. Therefore, the desert environment provides an excellent environment for studying the competitive effects between species. Wet years can produce a large number of plants with increased diversity, and dry years can reduce both the number of species and the overall amount of surviving plants-with the process accelerated under the combined variability and extreme conditions of the desert environment.
The team observed plant species that are native to the Sonoran desert and found in large numbers throughout the area, representing a range of abilities in rapid growth and efficient usage of water. Plant biomass was measured in the shoots, roots, and stems to draw conclusions about their response to different conditions.
All of the studied species thrived in wet environments, where they did not have to compete with other species for resources. When competitive species were present, dry environments had a limited effect on plants with greater water efficiency, and wet environments had a limited effect on plants with faster growth rates. Plant species with intermediate skills in water efficiency and growth rate tended to have the largest effect on competition, as well as the largest amount of competitiveness between species-perhaps implying that if you aren't particularly good at anything as a species, you have to try harder to survive.
Being able to predict the competitive responses from desert plants will become more important over time, with expected continued climate changes. If general traits can be used as predictors, the amount of study related to each individual plant species is reduced, and progress in predicting the results of climate change may be expedited. That may also mean that critical actions to reverse a trend may be taken in enough time to potentially save an endangered plant species.