Annual Plants in a changing climate

How’s the weather? 

The responses of Sonoran Desert winter annuals to seasonal weather and a changing climate

Dr. Larry Venable

Sonoran Desert Annuals

       Small desert plants that complete their life cycle in one growing season

       Comprise 50% of the Sonoran Desert flora

       Diverse community 

       Over 125 species of winter annuals, and 170 total (summer and winter) annual species occur at Tumamoc Hill.

Detailed demographic data on winter annual species has been collected since 1982 as part of a long term monitoring effort.


       Very sensitive to changes in precipitation and temperature

      Temperature and precipitation highly variable in the Sonoran Desert


Ecophysiological Studies of Tumamoc Winter Annuals

        Studies at Tumamoc have shown that winter annual species differ in traits associated with growth, stress tolerance and obtaining resources such as light and water.

       We identified a trade-off between stress tolerance and growth capacity (graph below). 

       Species that have stress tolerant physiology have less variable reproductive success.

       Species with faster growth ability have large fluctuations in reproductive success. 

How does plant physiology determine responses to weather?

     To address this question, we compared changes in population performance over 3 decades for species with different physiologies and related this to aspects of seasonal weather 


How has climate change affected community composition?

     We observed changes in abundances of species over 3 decades of monitoring at Tumamoc and related it to climate change and species physiologies.

It has been getting drier:

and hotter:

In response, germination has shifted to later in the season (Fig. 1A, gray circles).

Paradoxically, temperatures are now cooler when germination occurs (Fig. 1A, black circles).

These shifts have led to increases in abundance for cool-temperature, stress-tolerant species, with a concurrent decrease in abundance for high growth capacity species. (Fig. 1B). 


       Changes in weather conditions favor different species over time.

       Since weather in the Sonoran Desert varies widely, species with different physiologies can coexist within the same community due to reduced competing with each other for resources.

       Climate change has enabled certain cold-germinating species with stress tolerant physiologies to increase in abundance. 

       Understanding how species respond to the environment as it changes will help us to predict how Sonoran Desert plant communities will continue to respond to global climate change.

       Perhaps more importantly, understanding the mechanisms, such as how species with different physiologies respond to changes in weather, provides a more comprehensive understanding of the forces determining community composition over time. 

       The natural, undisturbed conditions at Tumamoc Hill provide a great setting to understand plant community responses to environmental change. 

For more on ecophysiology and climate change response of Tumamoc winter annuals see:

       Angert, A. L., T. E. Huxman, G. A. Barron-Gafford, K. L. Gerst, and D. L. Venable. 2007. Linking growth strategies to long-term population dynamics in a guild of desert annuals. Journal of Ecology 95:321-331. pdf

       Huxman, T. E., G. Barron-Gafford, K. L. Gerst, A. L. Angert, A. P. Tyler, and D. L. Venable. 2008. Photosynthetic resource-use efficiency and demographic variability in desert winter annual plants. Ecology 89:1554-1563. pdf

       Kimball, S., A. L. Angert, T. E. Huxman, and D. L. Venable. 2010. Contemporary climate change in the Sonoran Desert favors cold-adapted species. Global Change Biology 16:1555-1565. pdf

       Kimball, S., J. R. Gremer, A. L. Angert.,T .E. Huxman, D. L. Venable. 2012. Fitness and physiology in a variable environment. Oecologia 169:319–329. pdf

       Venable, D. L., and S. Kimball. 2013. Population and Community Dynamics of Sonoran Desert Winter Annuals. Pages 140-164 in C. K. Kelly, M. G. Bowler, and G. A. Fox, editors. Temporal Dynamics and Ecological Process. Cambridge University Press, Cambridge, England.

       Huxman, T. E., S. Kimball., A. L. Angert, J. R. Gremer, G. A Barron-Gafford, & D. L. Venable. 2013. Understanding past, contemporary, and future dynamics of plants, populations, and communities using Sonoran Desert winter annuals. American Journal of Botany 100:1369-1380. pdf

       Gremer, J. R., S. Kimball, K. R. Keck, T. E. Huxman, A. L. Angert & D. L. Venable. 2013. Water-use efficiency and relative growth rate mediate competitive interactions in Sonoran Desert winter annual plants. American Journal of Botany 100:2009-2015. pdf

       Huang, Z., S. Liu, K. J. Bradford, T. E. Huxman, and D. L. Venable. 2016. The contribution of germination functional traits to population dynamics of a desert plant community. Ecology 97: 250-261. pdf