关键词: 洞庭湖流域, 富营养化, 人类活动净磷输入(NAPI), 磷循环

Abstract: Research in germination responses and dormancy of buried seeds contributes to a better understanding of how the timing of germination and dormancy breaking is controlled in nature. Calligonum junceum, a superxerophilous shrub, is a candidate species for revegetation of the cold deserts of northwest China. Fresh seeds were placed on the surface and buried in soil (3-5 cm) in its natural habitat in July 2015, and exhumed (every six weeks in first year, and every eight weeks in second year, up to September 2017) and tested for germination over a range of temperature (15/5, 20/10, 25/15, 30/15 ℃, respectively). The germination percentage of exhumed seeds was very low at four varying temperatures, indicating the existence of primary dormancy. Most seeds were characterized by both non-deep and intermediate physiological dormancy. Seed dormancy was broken in late autumn, winter or next spring. Seeds exhumed in March had a higher germination percentage. Most seeds (70%) reentered secondary dormancy during summer due to high temperature. Most seeds exhibited annual dormancy/non-dormancy cycles in the natural habitat of Dabancheng, due to seasonal changes of temperature, rainfall and chronic wind. Seeds buried in soil had higher germination rate than that on soil surface, whereas seeds on soil surface had higher germination rate than that buried in soil when there was snowing in winter, which was related to different seasonal fluctuations of soil temperature and humidity.

Key words: net anthropogenic phosphorus input (NAPI), eutrophication., Dongting Lake basin, phosphorus cycle