Grass abundances during Dust Bowl

A study finds that shifts in seasonal precipitation patterns during extreme drought can explain grassland responses to the 1930s Dust Bowl drought in the United States. During the 1930s Dust Bowl drought in the United States, plants that use the C3 photosynthetic pathway expanded into grasslands previously dominated by C4-photosynthetic pathway plants. The shift was counterintuitive because C3 plants generally use water less efficiently and are more sensitive to high temperatures than C4 plants. To understand the factors behind the C3 expansion during drought, Alan K. Knapp and colleagues simulated 4 years of extreme drought at experimental grassland plots in Kansas and Wyoming. In accordance with the Dust Bowl observations, the ratio of C3 biomass production increased by as much as five-fold in the drought-exposed plots, whereas biomass declined in C4 plants. Analysis of long-term climate records revealed that C4 grasses are dominant in regions where warm temperatures and high precipitation co-occur, whereas C3 grasses generally increase with relatively high cool-season precipitation. During extreme drought years, the authors note, the proportion of precipitation that falls during cool weather increases, resulting in a seasonal precipitation pattern favorable to C3 grasses. The results explain the paradox of Dust Bowl vegetation responses to extreme drought. Additionally, the findings reveal that in globally important and climatically vulnerable grasslands, plant responses to climate extremes may include shifts in ecosystem function that are not predictable from well-known plant physiological traits, according to the authors.

Article #19-22030: "Resolving the Dust Bowl paradox of grassland responses to extreme drought," by Alan K. Knapp et al.

MEDIA CONTACT: Alan K. Knapp, Colorado State University, Ft. Collins, CO; e-mail: aknapp@colostate.edu

###

---

---