【作者】 吴殿鸣；

【导师】 薛建辉；

【作者基本信息】 南京林业大学 ， 生态学， 2012， 博士

【摘要】 本论文研究杨农间作系统中土壤氮素随地表径流和淋溶流失的过程及特点，探讨了不同施肥量对间作系统氮素循环及土壤氮累积量的影响，分析农林间作系统氮素损失的主要影响因素和作用机理。研究结果为减轻农业面源污染，营建合理的杨农间作模式，提高氮肥利用率，改善太湖流域水环境具有一定的理论和实践意义。主要结论如下：（1）单作农田氮素的淋溶水量与降雨量呈显著正相关关系。间作系统中杨树在生长季能有效减少土壤淋溶水量。氮素的迁移和淋失以NO₃^--N形式为主，间作系统内各样点淋溶水的氮素浓度均低于单作农田，各样点氮素淋失量受林分密度、与杨树种植行的距离影响，但差异不显著。（2）地表径流量和氮素流失量随降雨强度的增加而增加。间作系统能显著减少径流量和泥沙侵蚀量，并与林分密度成呈负相关关系。地表径流中TN和NO₃^--N的浓度在产流前期较高，且随着降雨时间的延长，趋于稳定或减小，后期则又有所上升；NH₄⁺-N浓度在产流初期即达最大值，后逐步下降。（3）杨麦间作系统能有效改善表层土壤（0²0cm）养分状况，20⁸0cm土层中NO₃^--N和NH₄⁺-N含量均小于对应层次小麦单作农田的含量。间作系统中土壤NO₃^--N含量具有明显的垂直和水平分布差异性，距杨树种植行越近，NO₃^--N在不同土层中变异程度越大。（4）土壤硝态氮含量在冬小麦各个生育时期表现出一定的规律性变化。0⁴0cm土层硝态氮含量孕穗期最高，而后缓慢下降；40⁸0cm土层硝态氮含量在孕穗期之前保持较低水平，之后深层土壤的硝态氮含量有增加的趋势。（5）冬小麦根系的根长密度和根干重均随土壤深度的增加而递减，密集分布区为0²0cm土层，并随生育期呈先升高后降低的趋势，最大值出现在灌浆期。间作系统中，冬小麦根长密度和根干重均小于单作农田，越靠近林带小麦根长密度和根干重越小。杨树根长密度随土壤深度增加呈下降趋势，越靠近林带根长密度和根干重越大。杨麦间作系统中杨树和小麦根系存在一定程度的生态位重叠。（6）¹⁵N微区试验表明，苋菜吸收尿素氮的比例随着施氮量的增加而减少，间作系统内肥料的利用率得到显著提高。间作系统内土壤各土层残留¹⁵N含量均小于对照农田；土壤中残留肥料¹⁵N以NO₃^--N形式存在的数量随施氮量的降低而降低。间作系统肥料¹⁵N的损失量和损失率明显低于对照农田。更多还原

【Abstract】 The process and characteristics of nitrogen loss along with the runoff and leaching flowwere investigated in poplar-crop intercropping systems. Effects of different levels of fertilizingtreatment were also studied on the nitrogen cycling and soil nitrogen accumulation inintercropping systems. Some main factors and action machenisms were identified affectingtheir nitrogen loss process. Research results could be a reference for practices in the alleviationof agricultural non-point pulltion, the increase of nitrogen use efficiency, the improvement ofwater environment in Taihu Lake area and the establishment of poplar-crop intercroppingsystems. The main conclusions were described as follows:（1）The results indicated that there existed a positive correlation between the quantity ofleachate water and precipitation. In intercropping ecosystem poplar trees could reduce thequantity of eluviated solution by canopy interception. The intercropping ecosystem couldreduce N leaching effectively and avoid N further moving into shallow groundwater. Thenitrogen leaching had spatial heterogeneity in intercropping ecosystem and changed with thedifferent stand density and different distance to the poplar row.（2）Surface runoff and sediment increased with the increase of rainfall intensity.Compared with the monoculture land of wheat, intercropping systems could decrease amountsof total nitrogen loss and sediment carried away by runoff. Some specifical patterns of TN lossand nitrate concentration were discovered with time. In early runoff stage the concentration washigher, and the reduced or kept stabile in middle stage, and in the end the concentrationreascended. The ammonium nitrogen concentration decreased with the time increasing.（3）The intercropping ecosystem could definitely improve soil nutrient status in the depthof0²0cm. Compared with monoculture land of wheat, intercropping ecosystem decreased thecontent of NO₃--N and NH₄⁺-N in the depth of20⁸0cm. The results showed there existed bothhorizontal and vertical variances of the content of soil nitrate in intercropping ecosystem. Thenearer the the distance of plot to the poplar row is, the more variation extent there existed.（4）Some specifical patterns of NO₃--N content changes appeared in the wholedevelopment stage of wheat. The content of nitrate in0⁴0cm soil layer came to the peak valueat the earring stage, and then decreased with increasing time. Before the heading stage, thecontent of nitrate was relatively lower in40⁸0cm soil layer, and then the content reascended.（5）Both root length density and biomass of wheat decreased with the increase of soildepth. The roots mainly distributed in the upper soil layer of0²0cm. The root length densityand biomass of wheat changed with different wheat development stages, the total dry weight ofroot in0⁸0cm soil layer reached its peak value at the filling stage. In monoculture system of wheat, the root length and dry weight in0⁸0cm soil layer were greater than those of theintercropping ecosystem in every development stage. In poplar-wheat intercropping system, thenearer the distance of the wheat root system to the poplar row is, the less the root system will be.The fine root length density and biomass of poplaer trees decreased with the increase of soillayer depth. The nearer the distance to the tree row was, the greater they were. There existed aniche overlapping are between poplar tree and wheat in such intercropping system.（6）In^<sup>15N micro-plot experiment, the utilization rate of nitrogen fertilizer by theamaranth decreased with the increase of N application level. The N use efficiency ofintercropping system significantly increased. Applying N fertilizer increased the nitrate contentsin0⁸0cm soil layer.Intercropping ecosystems could significantly decrease the¹⁵N losses andloss rate of N fertilizer compared with pure crop land.更多还原