| This research was conducted to explore the ecological restoration mechanism inabandoned wetland of subtropical China. We collected data from20in situ plots in asubtropical wetland, which had been abandoned from paddy agriculture for oneyear.The wetland with nutrient background for long-term experiment were dividedinto two water treatments (the drainage treatment and the seasonal flooding treatment).The vegetation community composition、ecological type and the community diversityduring the early wetland restoration stage were determined after the vegetationsurvey.We used the redundancy analysis (RDA) to conduct the corresponding analysisof the community structure of plant species and soil physical and chemical properties,to explore the dominate soil factors affecting the plant community structure inwetlands. Through the investigation on vegetation aboveground biomass, we analysethe relationship between productivity in Wetland ecological restoration process andspecies diversity, and the influence of the factors on productivity; in order to providebasic data to explore ecological conservation function of little piece of abandonedfarmland for the hilly region in the south. Our research has achieved conclusions asfollows:1. In the early restoration stage for subtropical abandoned rice fields of wetlandecosystem vegetation, community species composition was relatively simple. Higherplants that appeared in sample plot were all for herbs, species number of every yearwas ranging between28and38, with no obvious increase trend. The total speciesappeared in three years was65, belonging to32families and56genera, the largerfamilies among which were gramineae, compositae, syringaresinol, cyperaceaefamilies, etc. In the early restoration stage, the pioneer species were mainlyannual/biennial plants and aquatic plants, then perennial and mesophyte increasedgradually with succession proceeding. Different water treatments had great influenceon the ecological characteristics of the community and this kind of influence wasmore obvious with succession. The plant species numbers in drained zones wassignificantly greater than that in seasonal flooded zones. There was mainlyannual/biennial and mesophyte plants in the drained zones, while in seasonal floodedzones there were mainly aquatic plants, the mesophyte plants were far less than that in drained zones. Soil ventilation status was the main environmental factor whichrestricted the pioneer mesophyte species settled down. Community evenness waschanged from mixed and disorderly erratic to stability. And the species richness andShannon-Wiener index of diversity both had the decline trend year by year. Thereason of the decline trend might because that some of the mesophyte invasion wasnot adapt to aquatic environment and be phased out, then a stable community formed.2. A redundancy analysis between plant communities and soil factors wasconducted using the data of the vegetation investigation and soil properties analysis.Results showed that soil water condition, available K (AK), available P (AP), and pHwere the principle factors which affected plant growth and distribution. In first year,the vegetation species in the experimental sites could be divided into three typicalspecies groups according to the impact of soil factors: Ludwigia prostrate-Murdannia triquetra group (G1), Hemarthria altissima-Rotala rotundifolia-Lapsana apogonoides group (G2), and Conyza canadensis-Polygonum hydropiper-Paspalum pasaloides group (G3). G1mainly occurred in the soil with higher AKwhile G2mainly occurred in the periodically flooded zones. Furthermore, thedistribution of G3mainly occurred in drained zones and was positively correlated tosoil AP concentration. The species richness negatively related to soil available N(AN).Species diversity was positively related to pH and AK. However, the communityeveness index was positively related to soil total K(TK) and AK, but negativelyrelated to soil AN. The result reflected the poor correlation between species diversityand soil nutrient in the early stage of vegetation restoration in wetland.3. The vegetation above-ground biomass increased gradually during the earlywetland veaetation restoration process, with the biomass in the seasonal flooded zoneshigher than the drained zones. Negative correlations were found between thevegetation above-ground biomass and the vegetation richness, diversity index. Therewas no clearly correlation between biomass with community evenness. The TK andAN of the soil factors had significant positive relationship with the biomass. |
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