关键词: 有机磷组分, 长期施肥, 黄土旱塬, 小麦产量

Abstract: Riparian ecosystem is the ecotone between aquatic ecosystem and terrestrial ecosystem. It harbors high biodiversity and provides numerous ecosystem services. In this study, we examined species composition and α, β, and γ diversities of plant communities in the riparian zonealong a longitudinal gradient of elevation from downstream to upstream of the Beijiang River. The results showed that: (1) A total of 136 plant species belonging to 116 genera and 59 families were recorded. Gramineae and Compositae were dominant families. Species composition differed among plots. Many species were found with low frequency, with 48.7%-71.4% of total species occurred only once, suggesting that riparian ecosystem maintained plant species diversity through harboring different species rather than high individuals of single species. (2) The α diversity first decreased and then increased along the longitudinal gradient, with higher values observed at plots located in high altitudinal riparian zone. (3) Plant species turnover presented intense fluctuation and discontinuity from low altitudinal to high altitudinal sites or from downstream to upstream, while the similarity of plant species consistently varied. This would be related to the specific characteristics of riparian zone in maintaining biodiversity and the relative heterogeneous distribution of plants species derived by human activities, topographic, and climatic factors. (4) The γ diversity along the longitudinal gradient showed a down-up trend, suggesting that the riparian γ diversity at regional scale was simultaneously influenced by many environmental gradients. The γ diversity of high altitude was higher than that of low altitude.

Key words: Loess Plateau, long-term fertilization, organic phosphorus fraction, yield of wheat