丹江口水库典型消落区不同土地利用类型土壤养分分布

DISTRIBUTION OF NITROGEN,PHOSPHORUS IN THE SOILS OF DIFFERENT LAND USES FROM THE REPRESENTIVE WATERLEVEL-FLUCTUATING ZONE OF DANJIANGKOU RESERVOIR

丹江口水库是南水北调中线工程的取水口,调水工程的实施使新增淹没区土壤由于淹没浸泡可能使其中氮磷等营养盐释放,对水库水质构成威胁。采集丹江口水库典型消落区不同土地利用类型的表层土壤,测定现有消落区（149~160m）和新增消落区（160~172m）不同土地利用类型土壤的氮磷含量,分析消落区土壤养分分布特征。结果表明：土壤有机质含量在滩地和农田混杂区最高,分别为43.9、49.8g/kg,有机质易在扰动强烈或生物多样性丰富的区域累积。现有消落区（149~160m）和新增消落区（160~172m）土壤中总氮、总磷均值无显著性差异（p〉0.05）。消落区不同土地利用类型中,果园土壤的总磷、裸地土壤水溶性磷含量均为最高。现有新增消落区土壤磷流失率（0.564%）高于现有消落区（0.378%）,需防范新增消落区的磷流失风险。消落区土壤总氮含量与有机质含量呈极显著相关（p〈0.01）;总氮含量范围为0.044%~0.167%,农田、果园等受人为耕作作用强烈的土地利用类型土壤总氮含量相对较高。在消落区实施退耕还林等措施,恢复消落区的植被群落,可有效降低土壤的氮磷的流失。

The Mid-Route South-North Water Transfer Project taks water from the Danjiangkou Reservoir to overcome the water shortage in the North China.Once the Reservoir is impounded,the normal water level of the reservoir would rise from the elevation of 157 mto 170 m,and the areas of water-levelfluctuating zone could increase from 232.0km2（between the elevation of 150-160m）to 285.7km2（160-172m）.The soils of newly submerged area with different land uses may be a potential source to release nitrogen and phosphorus into the overlying water,causing a huge threat to the water quality of the reservoir.Based on the survey of the existing（between the elevation of 149 m-160 m）and newly increased（160m-172m）water-level-fluctuating zone in Dongkuwan and Caijiadu from northern bank of the Danjiangkou reservoir,several surface soil samples were collected from different land uses and the distribution characteristics of nitrogen,phosphorus under different land uses and elevations were analyzed.The results indicated that the surface soils of beach land and hybrid zone had a higher content of organic matter,with the values of 43.9g/kg-1 and 49.8g/kg-1,respectively,indicating organic matter can easily accumulate in the disturbance place and biodiversity area.The average contents of total phosphorus（TP）and nitorgen（TN）of the existing（between the elevation of 149m-160m）and newly increased（160m-172 m）showed no significant differences（p0.05）.In both water-level-fluctuating zones,the soil of orchard had the maximum content and water-soluble phosphorus（WSP）.The newly increased（160m-172m）water-level-fluctuating zone had a higher drop-out rate of phosphorus（0.564%）than the existing（between the elevation of 149m-160m）ones,indicating that it is necessary to take measures to prevent the risk of phosphorus loss in the newly increased water-level-fluctuating zone.The contents of TN and organic matter（OM）in the soils of the water-level-fluctuating zone had a significant correlation（p0.01）.The TN content in the soil varied from 0.044% to 0.167%,and the farmland and orchard,strongly effected by artificial cultivation,had a relatively high TN contents.Some measures like returning farmland to forests or restoring the vegetation communities are needed to implemented to effectively reduce the loss of nitrogen and phosphorus in the soil of water-level-fluctuating zone.