中文摘要：

研究了科尔沁沙地不同沙漠化阶段（潜在、轻度、中度、重度和严重沙漠化）植物一土壤系统的有机碳与氮储量，以揭示沙漠化对碳氮动态的影响．结果表明，从潜在沙漠化到轻度、中度、重度和严重沙漠化，生物量（地上与地下）有机碳储量分别下降26．4％、51．0％、79．0％和91．0％，生物量氮储量分别下降33．6％、66．9％、87．4％和93．2％；土壤有机碳储量分别下降52．2％、75．9％、87．0％和90．1％，土壤全氮储量分别下降43．5％、71．0％、81．3％和82．7％．植物一土壤系统的有机碳与氮储量大小为：潜在沙漠化（C：5266g·m^-2和N：534g·m^-2）〉轻度沙漠化（C：2619g·m^-2和N：303g·m^-2）〉中度沙漠化（C：1368g·m^-2和N：156g·m^-2）〉重度沙漠化（C：715g·m^-2和N：99g·m^-2）〉严重沙漠化（C：517g·m^-2和N；91g·m^-2）．研究结果表明，生物量碳氮储量的衰减在沙漠化后期（从重度到严重）快于沙漠化初期（从潜在到轻度），而土壤碳氮储量的衰减在沙漠化初期快于沙漠化后期；沙漠化过程中土壤有机碳储量的衰减要快于全氮，而生物量氮储量的衰减在沙漠化初期快于碳，在后期则相反．

英文摘要：

Organic carbon and nitrogen storages in plant-soil system were measured at different desertification stages （potential, light, moderate, severe, and most-severe） in Horqin sandy land. From potential desertification to light, moderate, severe, and most-severe desertification, total biomass （aboveground and belowground） carbon storages deerease by 26.4 %, 51.0 %, 79.0 %, and 91.0 %, respectively, while total biomass nitrogen storages decrease by 33.6 %, 66.9 %, 87.4 %, and 93.2 %, soil organic carbon storages by 52.2%, 75.9%, 87.0%, and 90.1%, and soil nitrogen storages by 43.5%, 71.0% , 81.3%, and 82.7%, respectively. The carbon and nitrogen storages in plant soil system are in the order： potential （C. 5 266 g·m^-2 and N; 534 g·m^-2） 〉light （C; 2 619 g·m^-2 and N： 303 g·m^-2） 〉moderate （C. 1 368 g·m^-2 and N： 156 g·m^-2） 〉severe （C： 715 g·m^-2 and N： 99 g·m^-2） 〉most severe （C： 517 g·m^-2 and N： 91 g·m^-2）. The biomass carbon and nitrogen storages decline more rapidly at later desertification stage （from severe to most-severe） than initial stage （from potential to light）, while soil carbon and nitrogen decline more rapidly at initial stage. There is a greater proportional decline in soll carbon than in nitrogen during desertification process. The biomass nitrogen storages decline more rapidly than carbon at initial stage, however, the case is reverse at later stage.