Abstract

We examined the germination response of 21 forb species collected from semiarid grasslands of central New Mexico. After-ripened seeds were subjected to 1 of 3 treatments: 1) no treatment; 2) a 3-wk stratification at 5 °C (cold-moist treatment); or 3) a 3-wk warm-moist treatment at 30 °C. All seeds were incubated under an alternating 10/20 °C temperature regime for 6 wk following treatment. Temperature regime had a significant effect on 13 of the 21 species. Twelve species responded positively to the warm-moist treatment, germinating during or following 3 wk at 30 °C. Six species were largely nondormant, germinating under all 3 treatment regimes, and 5 species did not germinate to an appreciable degree under any of the 3 treatment regimes. Ten species responded negatively to the 3-wk stratification, and in only one case was germination slightly improved by the 3-wk stratification. A subsequent 12-wk stratification treatment did, however, increase germination for 3 of the 5 dormant species. These results indicate that, while some species may require stratification, many southwestern grassland forbs are adapted to the combination of moisture and temperature associated with a monsoonal regime, that is, a warm-moist period. Summer, rather than fall, sowing is recommended as it will provide the benefit of dormancy-breaking dry heat followed by warm-moist conditions of the July to September monsoon.

RLPendletonBKPendleton 2014.

Germination patterns of a suite of semiarid grassland forbs from central New Mexico