不同退耕年限条件下菜子湖湿地土壤理化性质变化

Physical and Chemical Properties of Soils in Wetlands of Caizi Lake Different in Restoration History in Anqing,Anhui Province

退耕还湖是我国长江中下游地区湿地生态恢复的重要举措。土壤理化性质指标是评价湿地生态恢复状况的重要组成部分。选取菜子湖区不同退耕年限(2、5、8、10和20 a)湿地为研究对象,通过与相邻仍耕作油菜地和原始湿地土壤理化性质的比较,揭示了退耕还湖后湿地土壤生态特征变化规律。结果表明,随着退耕年限的增加,不同土壤理化性质指标变化趋势存在差异;土壤有机质含量逐年增加;土壤全氮和碱解氮含量在退耕5 a时显著升高,而后期变化平缓;土壤全磷和有效磷含量均呈先降低后升高趋势;土壤黏粒含量逐渐增加;土壤容重呈先升高后降低趋势;土壤含水量不断增加;土壤pH值缓慢降低。退耕2 a湿地土壤生态特征仍与油菜地相似,退耕2 a后土壤生态特征开始向原始湿地方向演化。退耕20 a期间湿地表层土壤理化性质变化强烈,而亚表层变化相对平缓。回归分析表明,除土壤pH和氮素含量的回归曲线拟合不显著外,退耕湿地表层土壤黏粒含量、容重、含水量、有机质含量、全磷含量和有效磷含量恢复到原始湿地水平所需时间分别为19、23、31、26、27和22 a,快于亚表层土壤的20、31、51、40、30和23 a。

Returning farmland to lake （RFL） is an important strategy in China for the restoration of wetland ecology in the middle and lower reaches of the Yangtze River. Soil physical and chemical properties are important indices for evaluation of the restoration of wetland ecology. Plots of wetland different in restoration history （2, 5, 8, 10 and 20 a） in the Caizi Lake were selected for comparison with their adjoining rapeseed fields and natural wetland in soil physical and chemical properties, i.e. soil bulk density, clay content, water content, pH, organic matter, total nitrogen, hydrolysable nitrogen, total phosphorus and available phosphorus, to expose law of the variation of ecological features of the soils after RFL. Results show that the variation of soil physical and chemical properties differed in trend between plots different in restoration history. Soil organic matter content increased with the age of restoration; soil total nitrogen and alkalyzable nitrogen in- creased significantly 5 years after restoration, and gradually leveled off in the later years; soil total phosphorus and availa- ble phosphorus decreased first and then increased; soil clay content increased gradually; soil bulk density rose first and then declined; soil water content went up steadily; and soil pH lowered gradually and slowly. The 2-year wetland soil was still similar to the adjoining rapeseed land soil in soil ecological feature. The second year seemed to be the turning point, after which the soil began to evolve towards natural wetland soil in ecological feature. During the 20 years soil physical and chemical properties changed more significantly in the surface layer than in the subsurface layer. Regression analysis shows that recovery of clay content, bulk density, water content, organic matter, total phosphorus and available phosphorus in the restored wetland to the respective level in the natural wetland may take 19, 23, 31,26, 27 and 22 years in the surface layer, and 20, 3l, 51, 40, 30 and 23 years in the subsurface layer.