关键词: 凋落物生产, 凋落物分解, 碳氮归还, 青藏高原, 高寒灌丛

Abstract: Aims Alpine shrublands are crucial for global carbon cycle due to their substantial soil carbon storage and sensitivity to global changes. Twig and leaf litter play a crucial role in terrestrial ecosystem carbon and nutrient cycling; however, comparative studies on their production and decomposition remain limited. This knowledge gap hinders accurate assessments of their contributions to soil carbon and nutrient cycling. Methods This study investigated the annual production, decomposition rates, and carbon and nitrogen retention of twig and leaf litter in an alpine shrubland ecosystem on the eastern margin of the Qinghai–Tibetan Plateau of China over a four-year period. Important findings Results found that: (1) Leaf litter production (138.94 g·m?2·a?1) was 4.41 times higher than twig litter production (31.48 g·m?2·a?1). Thus, leaf litter had a higher annual carbon and nitrogen inputs than twig litter. (2) Decomposition rate of twig litter (K = 0.356 a-1) was significantly slower than that of leaf litter (K = 0.522 a-1). The proportion of recalcitrant fraction of twig litter during decomposition was 4.86 times higher than that of leaf litter (0.287 vs. 0.059, respectively). (3) Nitrogen release patterns differed between twig and leaf litter: leaf litter exhibited a net nitrogen release, while twig litter followed a pattern of “enrichment—stabilization—release”. (4) After four years of decomposition, the estimated annual carbon retention of twig and leaf litter was similar (3.85 g?m-2?a-1 for twig litter and 3.72 g?m-2?a-1 for leaf litter). However, leaf litter retained significantly more nitrogen than twig litter (0.11 g?m-2?a-1 vs. 0.06 g?m-2?a-1). This study highlights the complementary roles of twig litter in promoting carbon accumulation in alpine shrubland due to its slower decomposition. In contrast, leaf litter plays a more crucial role in alleviating soil nitrogen limitation due to its faster nitrogen release and higher nitrogen return. Our results provide valuable foundation for accurately assessing the contributions of twig and leaf litter to soil carbon and nitrogen cycling.

Key words: Litterfall production, litter decomposition, carbon and nitrogen inputs, Tibetan Plateau, alpine shrubland