Impact of ambient temperature, precipitation and seven years of experimental warming and nutrient

Abstract

Global change is causing changes in temperature, precipitation, and nutrient availability. Alpine and polar regions are predicted to be among the most vulnerable for these changes. We applied a seven-year factorial experiment with warming and nutrient addition in two alpine vegetation communities. We analyzed relationship between fruit production and monthly mean, max and min temperatures during the fall of the pre-fruiting year, fruiting summer, whole fruit production period, and effects of summer and winter precipitation on fruit production. Nutrient addition and combined nutrient addition and warming increased total fruit production, and fruit production of graminoids in the later years in the Heath and Meadow and had a positive effect on forbs in the Meadow. In contrast fruit production of evergreen shrubs were negative affected by all treatments in the Meadow and Heath, while fruit production of deciduous shrubs was negatively affected in the Meadow. Minimum and mean temperatures were more important than max temperatures, and max temperatures of the fall before flowering was more important than max temperature during the flowering year. Winter precipitation had significant effect on total fruit production, fruit production of deciduous shrubs and forbs in the Heath, and on evergreen shrubs and forbs in the Meadow. Increased nutrient availability increased fruit production over time in contrasting high alpine plant communities, while experimental warming had no, or negative effect. Additionally, the results indicate that warmer summers may have limited impact on fruit production of high alpine plants. Instead, max temperatures during the fall before the fruiting year, and minimum temperatures may be more important.