Abstract
ABSTRACTWater table affects litter decomposition in wetlands, but its effects on the degradation of cellulose and lignin are poorly understood. We performed a decomposition experiment in Poyang Lake Wetland, to determine how water table affected the degradation of cellulose and lignin. After 60 days of decomposition at a site with a relatively highly water table, 46.19% of initial cellulose and 41.95% of initial lignin remained. Decay rates of both cellulose and lignin increased as the depth of the water table increased. Principle component analysis showed that the decay rates of cellulose and lignin increased with increasing soil pH, but decreased with increasing contents of clay and fungi: bacteria ratio. The path model accounted for 66% and 79% of the variation in cellulose and lignin decay rates, respectively, and considered the effects of interactions between the water table and related factors. The cellulose decay rate was affected by the water table with a direct coefficient of 0.47, and an indirect coefficient of 0.65, but the lignin decay rate was indirectly affected by water table (coefficient, 1.25) and directly affected by soil property (coefficient, 0.67). Thus, the water table affected the decomposition of cellulose and lignin via different mechanisms.
Highlights
Wetlands are ecosystems between aquatic and terrestrial ecosystems that are distinguished by special hydrological cycles, either at the surface or below ground (Shaffer et al 2016)
Our results showed that 30%–50% of cellulose and 20%–50% of lignin degraded in the first 60 d of the leaf litter decomposition duration (Figure 2), indicating that the degradation of lignin and cellulose occurs faster, and to a greater extent, in this wetland ecosystem than in terrestrial ecosystems (Dignac et al 2010; Berg and Mc Claugherty 2014)
Our study revealed variations in the decay rates of cellulose and lignin that were affected indirectly and directly by the water table, and clarified several aspects of cellulose and lignin decomposition
Summary
Wetlands are ecosystems between aquatic and terrestrial ecosystems that are distinguished by special hydrological cycles, either at the surface or below ground (Shaffer et al 2016). The decomposition of plant residues, a natural and critical process for wetland ecosystem function is essential to nutrient cycling (Mitsch and Gosselink 2000; Wu et al 2017). This process is regulated by the relationship between leaf litter biochemical quality, site environment (mean annual temperature, mean annual precipitation, annual evapotranspiration), and decomposer community composition (Tang et al 2014; Charman et al 2015; Waddington et al 2015; Liu et al 2017). Cellulose and lignin are major components of plant residues in wetlands because of their slow decomposition rates under anoxic conditions (Williams and Yavitt 2003). At the terrestrial–aquatic interface, especially in typical floodplain
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