4.2 Potential factors control nutrient release
Nutrient release during litter decomposition could be a nutrient source for the water column. There are accumulated studies that explored the effect of litter decomposition on water quality (McClaugherty et al. 1985; Zhai et al. 2019), but little is known about the effect of litter mixing on the water nutrient contents through decomposition. Our results indicated that the water nutrient content was mainly controlled by litter decomposition rate but not the initial nutrient concentrations in litters.
The effect of litter on nutrient release during decomposition can be related directly and indirectly to the initial litter quality and the decomposition rate (Liu et al. 2010). However, previous studies have paid the most attention to the effect of litter quality. In contrast, we did not find the relationship between the water nutrient content and the nutrient concentration in leaves (Fig. 7). We further confirmed that the nutrients released into waters were controlled by the decomposition rate of litter mixtures, indicated by the strongly positive correlations between water nutrient contents and litter decomposition rate (Fig. 8). Although such relations have been confirmed in some aquatic plants (Wu et al. 2017) and algae (Cao et al. 2015), these studies have not considered litter mixtures.