Abstract
Wetland plants are important components in constructed wetlands (CWs), and one of their most important functions in CWs is to purify the water. However, wetland plant litter can also increase eutrophication of water via decomposition and nutrient release, and few studies have focused on the interspecific variation in the decomposition rate and nutrient release of multiple plant species in CWs. Here a greenhouse litter-bag experiment was conducted to quantify the decomposition rates and nutrient release of 7 dominant macrophytes (2 floating plants and 5 emergent plants) in three types of water substrate. The results showed that plant litter species and growth forms significantly affected the litter mass losses. The nutrient release was significantly different among plant litter species, but not between floating and emergent plants. Litter traits, such as litter lignin, total nitrogen (TN) and total phosphorus (TP) can well predict the decomposition rates of submerged litter. These results indicated that submerging litter in water did not change the relationships between litter traits and litter decomposition rates, and leaching might play a more important role in the decomposition of submerged litter in CWs than that in other terrestrial ecosystems. These findings can provide suggestions for managers about the maintenance of constructed wetlands.
Highlights
Plant litter decomposition is a key ecosystem process in constructed wetlands (CWs) because it can release nutrients for plant growth [1] and control the dynamics of the carbon (C) stock [2,3].The process of plant litter decomposition includes all the physical and chemical changes that occur after tissue senescence and death, starting with complex organic molecules and ending in simple inorganic elements [4]
The following questions should be answered: (1) Do the decomposition rate and nutrient release depend on the plant species identity and/or plant growth form? (2) Which plant traits might predict the decomposition rates and nutrient release of those wetland plant species when they are incubated in water? (3) How do different water substrates affect plant litter decomposition rates and nutrient release? The final aim of this study is to understand the role of wetland plant species in CWs and provide suggestions to wetland managers about the maintenance of constructed wetlands
As it is understood that constructed wetlands are mostly nutrient-rich ecosystems that are linked with numerous human services and livelihoods, due management of wetland plant-litter decomposition is warranted for appropriate inclusive nutrient management
Summary
Plant litter decomposition is a key ecosystem process in constructed wetlands (CWs) because it can release nutrients for plant growth [1] and control the dynamics of the carbon (C) stock [2,3]. The process of plant litter decomposition includes all the physical and chemical changes that occur after tissue senescence and death, starting with complex organic molecules and ending in simple inorganic elements [4]. In constructed wetlands where moisture is not constraining, the most important determinants of decomposition are chemical traits of the decomposing material (litter quality), nutrient availability, and decomposer activity at the site where the decomposition occurs (external environment) [6,7,8,9]. Nutrient release can promote the growth and development of wetland plants; a large amount of plant litter decomposition might lead to eutrophication in CWs [10].
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