Inter-Annual and Seasonal Variation of ANPP and Leaf Nutrient Concentration in Cold-Temperate Wetlands of Tierra del Fuego

We investigated the inter-annual and seasonal variation of the aboveground net primary productivity (ANPP), and leaf nitrogen and phosphorus concentrations across two different types of wet meadows (spring-fed and riparian) in Tierra del Fuego Island, Southern Patagonia. In addition, we estimated grazing effects on ANPP, the nature of nutrient limitation, and the resorption efficiencies for both nutrients. ANPP showed a high inter-annual variation (CV = 49-57%), typical seasonal dynamics with a summer peak, and higher annual means at the spring-fed meadows (532 ga (TM) m(-2)a (TM) yr.(-1)) compared to the riparian meadows (310 ga (TM) m(-2)a (TM) yr.(-1)) with a higher contribution of graminoids (50-65%). Sheep grazing reduced a 66% the annual mean of ANPP (108 ga (TM) m(-2)a (TM) yr.(-1)) in riparian meadows. Leaf nitrogen concentrations were similar to reported values for graminoids from temperate and cold regions (1.5-2.5%), while leaf phosphorus concentrations were markedly higher (0.2-0.3%), indicating a nitrogen limitation. Resorption efficiency was 54.2% for nitrogen and 48.2% for phosphorus, exhibiting incomplete resorption proficiency for both nutrients. Our results represent valuable information to design sustainable management strategies for wetlands according to their spatial and temporal variation, and to define a baseline of vegetation functioning to assess the impact of climate change in high-latitude southern ecosystems.