【摘要】 凋落物分解是生态系统碳氮循环的重要环节,为探究青藏高原东部沙化草地中高山柳(Salix cupularis)凋落叶的分解及其对灌木"肥岛"形成的影响,采用分解袋法研究不同大小高山柳灌丛冠幅下不同微位置(茎基周围、冠幅最小半径处、灌丛间裸地)高山柳凋落叶的分解特征.结果表明:(1)分解时间显著影响高山柳凋落叶分解及养分释放过程,随着分解时间延长凋落叶木质素含量无显著变化,凋落叶质量损失率、C和N含量均显著增加(P <0.05),且凋落叶C/N和木质素/N均显著降低(P <0.05).(2)高山柳灌丛冠幅越小,其凋落叶质量损失率越高;且不同微位置下,高山柳凋落叶质量损失率外圈>中圈>内圈(P <0.05).(3)大冠幅的高山柳下,凋落叶N含量显著高于小冠幅的高山柳(P <0.05),但不同微位置未引起C(总有机碳、纤维素和木质素)和N养分含量变化的显著差异.总之,在高山柳凋落叶分解初期(第一年),高山柳灌丛冠幅大小仅影响其质量和N含量;无论高山柳灌丛冠幅大小如何,不同微位置下高山柳凋落叶养分含量无显著差异,这表明短期内高山柳凋落叶的分解对其"肥岛"的形成可能没有显著贡献.(图4表1参59)更多还原

【Abstract】 Litter decomposition is an important part of the carbon and nitrogen cycle in an ecosystem. Therefore, this study attempted to investigate the decomposition of Salix cupularis leaf litter in the desertified grassland in the eastern Qinghai-Tibet Plateau and assess the effect of S. cupularis litter decomposition on the formation of a "fertile island" under the S. cupularis bush. The field litterbag experiment was conducted to study the decomposition of litter under different microsites(central-inner cycle around the stem base, middle-middle cycle along the minimum radius, and interspace-outer cycle on bare land) around S. cupularis of different sizes(large, medium, and small size). The results showed that:(1) decomposition time significantly affected the decomposition and nutrient release process of S. cupularis leaf litter; although lignin content did not change significantly with the extension of time, the mass loss of litter and C and N content increased significantly(P < 0.05), and both C/N and lignin/N reduced significantly with the extension of time(P < 0.05).(2) The loss rate of litter quality was higher when the size of S. cupularis was smaller, and the order of mass loss rates was: interspace > middle > central under different microsites(P < 0.05).(3) The N content of litter leaf was higher significantly around large-sized than small-sized S. cupularis(P < 0.05), and microsites did not have any significant differences in the release of C(total organic carbon, cellulose, and lignin) and N. In summary, regardless of shrub size, the different microsites did not have a significant difference in the nutrient release of S. cupularis leaf litter, which indicated that the litter decomposition could be insignificantly attributed to the formation of the "fertile island" of S. cupularis during the early stage of the decomposition of S. cupularis leaf litter, i.e. for the first year.更多还原