中文摘要：

结合第二次全国土壤普查（1979年）一黑龙江省水稻土分布及其相关数据，2011年采取调查取样与室内分析的方法，研究了黑龙江地区4种类型（黑土型、白浆土型、草甸土型和沼泽土型）水稻土表层有机碳、氮含量及其密度的状况。结果表明：目前（2011年）4种类型水稻土表层平均有机碳、氮含量范围分别为21．18±7．27～30．91±9．99gkg-1、1．83±0．44。2．49±0．74gkg-1，表层平均有机碳、氮密度范围分别为5．32±1．42～6．95±0．98kgm-2、0．46±0．07～0．56±0．08kgm-2，其中沼泽土型水稻土表层有机碳、氮含量及其密度最大，黑土型则最小；沼泽土型与黑土型水稻土之间表层有机碳、氮含量及其密度差异均达1％显著水平，与草甸土型水稻土之间表层有机碳、氮含量差异均达1％显著水平，其有机碳、氮密度差异均达5％显著水平，与白浆土型水稻土之间表层有机碳及其密度差异达1％显著水平。与第二次全国土壤普查的相关数据相比较，黑龙江地区4种类型水稻土表层有机质（碳）、氮含量呈现明显下降趋势，但其表层有机碳、氮含量及其密度仍处于较高水平。

英文摘要：

The contents and densities of organic carbon and nitrogen in the topsoil of different paddy soilswere researched by field investigation and indoor analysis in 2011 according to the distribution of paddy soils （black soil, albic soil, meadow soil and boggy soil） in Heilongjiang Province obtained from the second national soil investigation. The results indicated that the content of organic carbon and nitrogen for the four paddy soils were 5.32 ± 1.42 - 6.95± 0.98 kg m-2, 0.46 ±0.07 - 0.56 ± 0.08 kg m-2, respectively, while the average density of organic carbon and nitrogen were 5.32 ± 1.42 - 6.95 ± 0.98 kg m-2, 0.46 ± 0.07 - 0.56 ± 0.08 kg m-2, respectively. Boggy soil had the maximum content of organic carbon and nitrogen, while black soil had the minimum content. The differences of organic carbon, nitrogen and density between boggy soil and black soil were very significant （P 〈 1%）. The differences of organic carbon and nitrogen between boggy soil and meadow soil were very significant （P 〈 1%）, while the differences of density were significant （P 〈 5%）. The differences of organic content and density between boggy soil and albic soil were very significant （P 〈 1%）. Although the contents of organic carbon and nitrogen at surface of the four paddy soils reduced obviously, compared with the second national soil investigation, the contents of them still kept a high level.