库布齐东段不同植被恢复阶段荒漠生态系统碳氮储量及分配格局

为科学评价植被恢复促进沙漠化逆转对碳氮储量的影响,以流动沙地、半固定沙地、油蒿固定沙地、柠条固定沙地、沙柳固定沙地5个阶段荒漠生态系统为研究对象,采用时空替代法分析植被恢复过程中荒漠生态系统碳氮储量及分配格局。结果表明:不同恢复阶段碳氮储量均表现为:流动沙地(3320.97 kg C/hm~2、346.69 kg N/hm~2)半固定沙地(4371.46 kg C/hm~2、435.95 kg N/hm~2)油蒿固定沙地(6096.50 kg C/hm~2、513.76 kg N/hm~2)柠条固定沙地(9556.80 kg C/hm~2、926.31 kg N/hm~2)沙柳固定沙地(19488.54 kg C/hm~2、982.11 kg N/hm~2)。植被层碳氮储量均呈现随植被恢复逐渐增加的趋势,除流动沙地外,其他阶段碳氮储量均以灌木层为主,占比分别为66.65%—91.41%和52.94%—93.39%,草本和凋落物占比较小。灌木各器官生物量及碳储量分配均为:茎根叶,氮储量分配无明显规律,草本各器官生物量及碳氮储量分配均为地上部分高于地下部分。土壤层是荒漠生态系统碳氮储量的主体,碳储量占比为68.64%—99.62%,氮储量占比为89.26%—99.89%,同样呈现随植被恢复逐渐增加的趋势。碳氮储量随土层加深逐渐降低,具有明显的表层富集特征,且随植被恢复过程富集性显著加强。这说明人工建植促进植被演替实现沙漠化逆转可以显著增强荒漠生态系统的碳氮固存能力。

Carbon and nitrogen storage and distribution patterns of desert ecosystems at different vegetation restoration stages in the eastern Hobq Desert

Storage of carbon (C) and nitrogen (N) in ecosystems is the result of long-term accumulation in vegetation and the soil stratum. In this study, a spatial series analysis was performed, that represented a temporal series to accurately estimate the total C and N reserves of the eastern Hobq Desert ecosystems. Fixed sand was selected for the standard plots to identify the C and N storage and distribution patterns at different restoration stages and in various vegetation and plant organs. The aim of the study was to clarify the effects of vegetation restoration and the reversion process of desertification on the C and N storage in a mobile dune, semi-fixed sand, Artemisia ordosica fixed sand, Caragana korshinskii fixed sand, and in Salix cheilophila. The results revealed that the change trends for the total C and N storage in the desert ecosystems at different restoration stages were the same:mobile dune (3320.97 kg C/hm² and 346.69 kg N/hm²) < semi-fixed sand (4371.46 kg C/hm² and 435.95 kg N/hm²) < Artemisia ordosica fixed sand (6096.50 kg C/hm² and 513.76 kg N/hm²) < Caragana korshinskii fixed sand (9556.80 kg C/hm² and 926.31 kg N/hm²) < Salix cheilophila fixed sand (19488.54 kg C/hm² and 982.11 kg N/hm²). Except for the mobile dune, the plant C and N stores at the other sites were mainly distributed in the shrub layer. At these sites, the C and N reserve in shrubs accounted for 66.65%-91.41% and 52.94%-93.39% of the plant layer, respectively. However, the C and N reserve of the herbaceous plants and litter only accounted for a small proportion of the plant layer. Additionally, different organs in the plants had different C and N storage characteristics; the biomass and C reserve of the shrubs both showed the following, stem > root > leaf. The distribution of N storage in the different organs of the shrubs was not significant. The above-ground biomass and the C and N storage of the herbaceous pants were greater than the underground biomass. Like other ecosystems, the main components of a desert ecosystem are the C and N storage in the soil layer, which accounted for 68.64%-99.62% and 89.26%-99.89% of the desert ecosystem, respectively. When the sand was gradually fixed and vegetation cover rate increased, the C and N storage in the soil layer increased. Different soil depths had different C and N storage characteristics; the C and N storage of the shallow soil was greater than that of the deep soil. This revealed an obvious enrichment phenomenon in the surface soil. Additionally, with the reversion of the process of desertification, the enrichment became more and more remarkable. In conclusion, with the succession of vegetation and soil development, the reversion of desertification could promote the absorption and fixation of C and N in desert ecosystems.