Litter production and leaf nutrient concentration and remobilization in response to climate seasonality in the central Amazon

Abstract

Litterfall is the largest source of nutrients to forest soils of tropical rainforests. However, variability in litterfall production, nutrient remobilization, and changes in leaf nutrient concentration with climate seasonality remain largely unknown for the central Amazon. This study measured litterfall production, leaf nutrient remobilization, and leaf area index on a forest plateau in the central Amazon. Litterfall was measured at monthly intervals during 2014, while nitrogen, phosphorus, potassium, calcium and magnesium concentrations of leaf litter and canopy leaves were measured in the dry and rainy seasons, and remobilization rates determined. Leaf area index was also recorded in the dry and rainy seasons. Monthly litterfall varied from 33.2 (in the rainy season) to 87.6 g m^‒2 in the dry season, while leaf area index increased slightly in the rainy season. Climatic seasonality had no effect on concentrations of nitrogen, calcium, and magnesium, whereas phosphorous and potassium responded to rainfall seasonality oppositely. While phosphorous increased, potassium decreased during the dry season. Over seasons, nitrogen, potassium, and phosphorous decreased in leaf litter; calcium increased in leaf litter, while magnesium remained unaffected with leaf aging. Regardless, the five nutrients had similar remobilization rates over the year. The absence of climate seasonality on nutrient remobilization suggests that the current length of the dry season does not alter nutrient remobilization rates but this may change as dry periods become more prolonged in the future due to climate change.