Decomposition of green and senescent leaves in Amazonian streams: nutrients, toughness, and decomposers biomass

Abstract

Studies on leaf decomposition in streams usually focus on senescent leaves; however, in the Amazon, green leaves are a crucial source of allochthonous material, linked to the rainy season and strong winds. We assessed the decomposition of green and senescent leaves in Amazonian streams by using 16 plant species. We hypothesized that green leaves would exhibit higher decomposition, fungal biomass, and shredder biomass due to the remobilization of nutrients during leaf senescence and lower toughness. Multivariate analyses segregated the plant species into two groups corresponding to green and senescent leaves associated with distinct litter traits. Green leaves had higher concentrations of carbon, nitrogen, phosphorus, potassium, sulfur, tannin, and cellulose, whereas senescent leaves had higher values of toughness, specific leaf mass, lignin, C:N, C:P, and N:P. Polyphenol, calcium, and magnesium concentrations varied widely between and within species, but were similar between green and senescent leaves. The leaf breakdown rate was 1.7 times faster in the green leaves than in the senescent leaves. Fungal biomass was similar between green and senescent leaves on average. However, the shredder biomass was 5.9 times higher in green leaves than in senescent leaves. Our findings highlight the difference between green and senescent decomposition patterns in Amazonian streams.