三江平原退化湿地和农田土壤养分的比较研究

三江平原农业开垦导致地表水位和土壤水分下降,原生湿地退化为沼泽化草甸和典型草甸,或者直接转化为水田和旱田.退化湿地与农田土壤养分的对比研究结果表明,4种样地类型0-30 cm土层土壤有机质含量为水田＞沼泽化草甸＞旱田＞典型草甸,全氮含量差异与有机质含量差异相一致,速效磷含量为水田＞旱田＞沼泽化草甸＞典型草甸.这说明在湿地退化为典型草甸的过程中土壤养分严重下降,水分状况是影响湿地土壤养分下降的关键因素;但是农田土壤养分仍然保持较高水平,主要是由于耕作、施肥等非水分因素的影响.由此可见,水分条件和人为干扰共同决定了退化湿地和农田土壤养分状况.

Soil Nutrients of Degraded Wetland and Farmland in Sanjiang Plain

Reclamation of the Sanjiang Plain for development of agriculture has led to decline of the surface water table and soil moisture,thus triggering degradation of primary marshes into swampy meadow,or typical meadow,or even directly into paddy field and dry farmland.A study was carried out to compare degraded wetlands with farmland in nutrient content in the surface soil 0-30 cm deep.Four types of degraded wetland showed a sequence of paddy field>swampy meadow>dry farmland>meadow in terms of organic matter and total N;and paddy field>dry farmland>swampy meadow>meadow in terms of readily available P.It is clearly indicated that soil nutrients dropped significantly with primary marsh degrading into meadow,and that variation of the moisture regime was the most important factor leading to decline of soil nutrients.Soil nutrients of farmlands remained quite high,because of cultivation and fertilizer application. Therefore,change in moisture regime and human disturbances are the two important factors responsible for difference between degraded wetlands and farmlands in soil nutrient content.