Study On Plant Configuration In Ecological Engineering Of Returning Farmland To Wet Land In Hengdong

Reverting farmland to wetland is one of the main methods to restore the area and function of wetland,and the construction of optimum wetland vegetation is the premise of restoration of wetland ecosystem and function.Reasonable arrangement of plants can make plants play a better role of purification and economic landscape in the restoration and reconstruction of wetland ecosystem.Based on the characteristics of plant resources,pollution sources and pollutants in Mishui of Hengdong area in Hunan province,three different models of plant arrangement were constructed to analyze the influence on water purification in this study.It was of great significance to the practice of restoration of vegetation in degraded wetlands and reverting farmland to wetland-The main results were as follows:(1)According to different water levels and site conditions,three different models of plant arrangement were constructed,namely,eco-economic model(I),ecological landscape model(?)and rapid growth and large biomass purification model(?),and the area without reverting farmland to wetland as control treatment(CK).Under the same influent load,the removal rate of pollutants in the area of reverting farmland to wetland was significantly higher than that in the area without reverting farmland to wetland.There are differences in the purification of water quality under three different models of plant arrangement.In terms of the purification effect of water turbidity,?(2.57NTU)>?(2.34NTU)>?(2.23NTU);in terms of removal rate,?(77.14%)>?(54.28%)>?(42.85%)>CK(20.57%);in terms of TN removal rate,?(78.18%)>?(73.27%)>?(72.91%)>CK(44.55%);in terms of COD removal rate,?(43.50%)>1(37.22%)>?(35.75%)>CK(21.70%);in terms of NH3-N removal rate,III(73.28%)>II(69.94%)>I(69.10%)>CK(37.79%).The comprehensive capacity of each group in turn was III>II>I>CK.(2)Under the same influent load,the effect of plant arrangement on the removal rate of pollutants in the areas of reverting farmland to wetland was more obvious due to seasonal factors,the absorption of N,P and organic matter were more quicker in spring and summer,and the removal rate of TP,TN and NH3-N were approximately 30-50%,the removal rate of COD was approximately 20%;however,the absorption of N,P and organic matter were much more slower in autumn,and the removal rate of TP?TN?NH3-N?COD were approximately 20%.(3)Margalef species richness index,Simpson dominance index,Shannon-Wiener diversity index and Pielou evenness index were used to analyze plant communities.The results showed that the diversity of plant communities with different plant arrangements was much higher when compared with the areas without reverting farmland to wetland.The increasing range of Margalef index was I(0.2553)>?(0.2004)>?(0.1923)>CK(0.12);the increasing range of Simpson index was ?(0.172)>?(0.1495)>?(0.116)>CK(0.0774);the increasing range of Shannon-Wiener index was II(0.228)>I(0.226)>III(0.2116)>CK(0.176);however,the evenness of Pielou index has no great difference.