Litter quality and interactions of macrophytes tissues decomposition in a eutrophic shallow lake

Abstract

Abstract Macrophyte decomposition is critical for eutrophic shallow lakes because it can influence the accumulation of the sediment layer and lake terrestrialization processes. As three dominant macrophytes in Lake Baiyangdian, N. nucifera ( Nelumbo nucifera ), P. australis ( Phragmites australis ), and T. latifolia L ( Typha latifolia L ) have spread quickly and covered a large proportion of the lake as a result of water nutrient enrichment over the past 30 years. In this study, we investigated the decomposition processes of these three plants using the litterbag method to demonstrate their roles in lake degradation. Decomposition rates of plant tissues (leaves, stems, and roots) and whole plants were determined at three sampling sites that had different nutrient levels. The litter samples displayed a wide range of decomposition rates. Of all samples, the leaves of N. nucifera decomposed the most rapidly, while the stems of P. australis had the lowest decomposition rates. The decomposition correlated significantly with the initial litter phosphorus (P) and nitrogen (N) content, and the ratios of carbon (C) to N (C:N) and C to P (C:P), especially the P-related indicators, implying a relative shortage of P in the sampled species. Although not as strong as litter quality, site chemistry effects also can be observed during decomposition. The site with a high nutrient level in the water body exhibited rapid decomposition and high decomposition rates. Interactions of plant tissues (expressed as the differences between observed and expected decomposition rates) were tested when we investigated the decomposition processes of the whole plants. Observed decomposition rates of the whole plant individuals significantly deviated from the expected rates that were calculated based on the mass losses of plant tissues of the corresponding species. The strengths of the interactions varied greatly with plant species. T. latifolia L displayed significantly positive interactions among plant tissues, while significantly negative interactions of plant tissues were observed for the other two species. Moreover, our results suggest that the interactions of plant tissues greatly vary among the three sampling sites, indicating that both the biotic and abiotic characteristics of an ecosystem can be important drivers controlling litter decomposition.