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Question

The ephemeral layer is an important component of the plant community in cold deserts. Conventional wisdom has it that the ephemeral layer primarily depends on early spring snowmelt water for germination and development. However, this hypothesis has never been subjected to rigorous testing.

Location

Southern edge of the Gurbantunggut Desert, a cold desert and a natural habitat of ephemeral plants (the inter-sand dune lowland), in the far northwest of China and around the geographical centre of the Eurasian continent.

Methods

At the end of the snow cover season between 2009 and 2011, four different snow treatments (0, 50, 100 and 200% snow cover, with 100% representing the natural amount of snow) were applied, using five replicates. Seedling establishment, species diversity and plant growth, population, cover and productivity were monitored throughout or sampled at the end of the growing season.

Results

The ephemeral plant germination and seedling density were significantly influenced by changes in snow cover. Germination, density of mature ephemeral plants and plant coverage rose as snow cover depth increased. However, the height, rooting depth, numbers of lateral roots and above-ground biomass of individual plants decreased as snow cover increased, and plant size was negatively correlated with plant density. At the ephemeral layer level, above-ground biomass showed no significant variation between snow treatments. There was also no significant difference in species richness among the snow treatments.

Conclusions

Increased snow resulted in higher plant density of ephemerals. However, this high density induced strong competition, reducing the body size of individual plants. By the end of the growing season, snow treatments did not induce significant changes in primary productivity of the ephemeral layer. Primary productivity or growth after seedling establishment depended mainly on rainfall that occurred after the snow had melted, not on snowmelt water itself. Thus conventional wisdom was shown to be only partially true. Snow was important to these ephemeral plants, but its role was limited to seedling establishment.