气候变化领域集成服务门户

At the level of individual plants, exposure to prior freezing can increase drought tolerance, in a phenomenon referred to as cross acclimation. However, it is unclear how cross acclimation may contribute to the combined effects of freezing and drought on plants at the community or ecosystem levels, given that cross acclimation can vary among species. We used intact plant-soil mesocosms from an old field to examine how spring freezing influences summer drought tolerance, assessed via the responses of major functional groups (graminoids, legumes and non-leguminous forbs) and total plant productivity. We applied N-15 tracer to the mesocosms in either spring or summer, to assess effects on early/late season nitrogen retention. Freezing and drought affected both aboveground production and N-15 retention significantly, but their effects were additive, which was inconsistent with cross acclimation. The aboveground biomass responses differed from this trend at the functional group level, with an apparent cross acclimation effect for legumes, multiplicative effects of freezing and drought for non-leguminous forbs, and no significant freezing or drought effects for graminoids. These results suggest that despite variation in cross acclimation among functional groups, possible competitive and compensatory interactions can dilute cross acclimation effects at the ecosystem level.