退田还湖后洞庭湖区土壤颗粒组成和化学特性的变化

土壤质量变化的长期动态监测是评价"退田还湖"工程实施后生态学效应的重要组成部分.选取洞庭湖区3种不同退田还湖模式(自然恢复、种植芦苇和种植杨树)下的典型"双退"区(青山垸、官垸和小集成)为对象,通过与相邻堤垸农田生态系统土壤物理性质和化学性质的比较,揭示退田还湖后土壤生态特征的变化及其成因.研究发现,以种植杨树作为湿地恢复模式的小集成样地促进了粘粒和粉粒的形成,并能快速累积有机质、全磷、全钾;以种植芦苇为恢复方式的官垸样地中,由于经常受洪水影响而使土壤物理性质有向自然生态系统转化的趋势,同时土壤有机质含量有所下降,而全磷含量增加;以恢复自然湖泊为方式的青山垸样地中,土壤物理特性和全量元素含量无明显变化.研究认为优势物种的生物学特性和自然过程的强弱等是造成洞庭湖"退田还湖"系统中土壤颗粒组成和化学性质发生变化的主要原因.

Changes of soil particle composition and chemical characteristics after "returning farmland to lake" in the Dongting Lake area

Long-term monitoring of soil characteristics is an important measure to evaluate the ecological consequences after implementation of the project of "returning farmland to lake (RFTL)".Three sites (Xiaojicheng, Guanyuan, and Qingshanyuan) which restored by three models of RFTL projects (poplar plantation, reed plantation, and natural restoration, respectively), were selected to study the changes of soil physical and chemical properties in comparison with counterpart agro-ecosystems after 8-year implementation of RFTL in the Dongting Lake area. Poplar plantation can facilitate the formation of clay and silt, and increase the contents of organic matter, total phosphorus, and total potassium in the Xiaojicheng. Soil physical characteristics was acclimated to that of natural ecosystem due to the influence of incessant flood in the Guanyuan where restored by reed plantation. Meanwhile, the content of organic matter decreased but total phosphorus increased in the Guanyuan. Soil particle composition and chemical characteristics were insignificantly different with that of agro-ecosystems in the Qingshanyuan, where natural lake was restored. Both biological characteristics of dominant species and the strength of natural processes are main factors accounting for the differences in soil characteristics in different restoration models of RFTL projects.