Emergence and development of Chihuahuan Desert grasses under simulated wet-dry sequences

Abstract

We evaluated the response (emergence, speed of germination, survival) of nine grasses (six native, three introduced) commonly occurring in the State of Chihuahua, Mexico to four irrigation “wet-dry” sequences that simulate sequences of days with and without rainfall, under greenhouse conditions. The sequences provide a total of 120, 100, 80 and 60 mm (high, medium, low, and very low) of water for 40 days. The native species were Bouteloua curtipendula, B. dactyloides, B. eriopoda, B. gracilis, Digitaria californica, and Leptochloa dubia. The introduced grasses were Cynodon dactylon, Eragrostis curvula, and E. superba. A decrease in water, resulting from the drier sequences, delayed the emergence from 4 to 7 days in most species. The native B. dactyloides displayed the best potential for growth with high emergence (18%) and high survival (44%) under low or very low water sequences. In general, survival for native species was higher than for introduced species under water restrictions. The native species showed high survival and high root:shoot ratio (RSR) under drought, which was not observed in introduced species. As expected, we found that plant species responded differently to modeled rainfall sequences, providing insight into plant adaptations to drought and potential for survival under environmental variation.