Montane meadow change during drought varies with backgroundhydrologic regime and plant functional group

Debinski, Diane; Wickham, Hadley; Kindscher, Kelly; Caruthers, Jennet; Germino, Matthew

Climate change models for many ecosystems predict more extreme climaticevents in the future, including exacerbated drought conditions. Here we assess the effects ofdrought by quantifying temporal variation in community composition of a complex montanemeadow landscape characterized by a hydrological gradient. The meadows occur in tworegions of the Greater Yellowstone Ecosystem (Gallatin and Teton) and were classified into sixcategories (M1–M6, designating hydric to xeric) based upon Satellite pour l’Observation de laTerre (SPOT) satellite imagery. Both regions have similar plant communities, but patch sizesof meadows are much smaller in the Gallatin region. We measured changes in the percentcover of bare ground and plants by species and functional groups during five years between1997 and 2007. We hypothesized that drought effects would not be manifested evenly acrossthe hydrological gradient, but rather would be observed as hotspots of change in some areasand minimally evident in others. We also expected varying responses by plant functionalgroups (forbs vs. woody plants). Forbs, which typically use water from relatively shallow soilscompared to woody plants, were expected to decrease in cover in mesic meadows, but increasein hydric meadows. Woody plants, such as Artemisia, were expected to increase, especially inmesic meadows. We identified several important trends in our meadow plant communitiesduring this period of drought: (1) bare ground increased significantly in xeric meadows of bothregions (Gallatin M6 and Teton M5) and in mesic (M3) meadows of the Teton, (2) forbsdecreased significantly in the mesic and xeric meadows in both regions, (3) forbs increased inhydric (M1) meadows of the Gallatin region, and (4) woody species showed increases in M2and M5 meadows of the Teton region and in M3 meadows of the Gallatin region. The woodyresponse was dominated by changes in Artemisia spp. and Chrysothamnus viscidiflorus. Thus,our results supported our expectations that community change was not uniform across thelandscape, but instead could be predicted based upon functional group responses to the spatialand temporal patterns of water availability, which are largely a function of plant water use andthe hydrological gradient.

Montane meadow change during drought varies with backgroundhydrologic regime and plant functional group

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