关键词: 更新机制, 树线, 林线生态交错区, 木本植物幼苗, 环境胁迫, 气候变化, 空间分布特征

Abstract: After the implementation of grassland contracting system, two grassland management patterns were formed in the QinghaiTibetan Plateau, namely singlehousehold management pattern (SMP) and multihousehold management pattern (MMP). The soil stoichiometry under two grassland management patterns were compared in Nagqu, China. The results showed that in the 0-30 cm soil layer, there were no differences in the ratios of SOC∶ STN, SOC∶STP and STN∶STP between SMP and MMP. In the vertical direction, regardless of management pattern, the SOC∶STP and STN∶STP at the 0-15 cm soil layer were significantly higher than those at the 15-30 cm soil layer. At the 15-30 cm soil layer, the SOC∶STP and STN∶STP were significantly higher under the MMP than under the SMP. In addition to a significant linear correlation between SOC and STN, there were nonlinear coupling relationships between SOC and STP, STN and STP, as well as SOC, STN, STP and their stoichiometric ratios. Phosphorus was a main limiting factor of soil in the study area. Our results suggested that although soil nutrients were significantly different between MMP and SMP, there was no difference in soil nutrient stoichiometry. Therefore, soil stoichiometry may not be effective in evaluating soil quality in this area.

Key words: regeneration mechanism, tree seedling, spatial distribution characteristics, environment stress, treeline ecotone, climate change, treeline