A resurvey of late-lying snowpatches reveals changes in both species and functional composition across snowmelt zones

Abstract

Alpine snowpatches are areas that, due to topographical and climatic factors, retain snow long after the thaw in the surrounding landscape. Within snowpatches there are often reliable patterns of snowmelt resulting in differences in plant composition, with snowpatch specialists limited to areas of late snowmelt. In 2013, we resurveyed vegetation in early, mid and late snowmelt zones across seven alpine snowpatches in the Snowy Mountains, Australia, 6 years after the initial 2007 survey. In both surveys, there were differences in vegetation cover and species composition among snowmelt zones; in particular, the cover of graminoids was higher in areas of earlier thaw. Differences in functional composition between survey periods were determined using functional traits (plant height, percent leaf dry matter content and specific leaf area) to calculate community trait-weighted means. In both surveys, early and mid snowmelt zones were dominated by taller species with larger leaves, mostly graminoids. Notably, by 2013 there was an increase in species richness in the late snowmelt zone and an increase in the cover of the tall tussock grass Poa costiniana across all snowmelt zones, driving changes in the community trait-weighted means for plant height and specific leaf area in the late snowmelt zone. The results highlight that snowpatch vegetation can change within relatively short time periods and that snowpatch plant communities may not remain as discrete units in the near future due to the encroachment of more competitive and productive species from the surrounding landscape.