Abstract: Forest debris and understory vegetation play an important role in forest key processes and plantation management. The influence mechanism of debris management on the understory vegetation is not clear in subtropical plantation. This study was based on a field platform in middle-aged plantation of Chinese fir (Cunninghamia lanceolata) under two treatments (debris removal and control) with four replications. After four years continuous treatments, two dominant herb species (Dryopteris chinensis,Lophatherum gracile) and two dominant shrub species (Ilex pubescens,Callicarpa bodinieri) were sampled in the growing season. The concentrations of NH₄⁺-N, NO₃^--N, available P in rhizosphere and bulk soils, as well as N and P in leaves and roots were measured to explore the responses of roots and leaves in different species. The results showed that debris removal significantly improved the available P in the rhizosphere and bulk soils for the four species (P<0.05), while different species had different responses for the concentrations of mineral N (NH₄⁺-N+NO₃^--N). Debris removal had no significant influence on leaf nutrients, except for reducing leaf P of C. bodinieri, but significantly increased root N and P, except for root P of L. gracile. Furthermore, debris removal improved the root N/P of D. chinensis and L. gracileand the leaf N/P of C. bodinieri. In conclusion, debris removal can enhance the nutrient supply capacities of surface soil in a short time. Root has an earlier and stronger response to soil nutrient and environmental changes than leaf, whereas leaf has a stronger internal stability of nutrient balance than root in Chinese fir plantation.

Key words: seed, flower organ, Qinghai-Tibetan Plateau, pollen, Saussurea przewalskii