Abstract: Nutrient return with litters is the main process of ecosystem material cycling and an important source of nutrients for tree growth. Compared with other elements, potassium (K) and sodium (Na) play an extremely important role in regulating osmotic pressure. Both elements are easy to be lost, as their leaching is strong. However, there is a lack of necessary attentions. We investigated the return characteristics of K and Na in different types of litter from September 2015 to August 2016 in a primary dark coniferous forest (3589 m a.s.l.), which was dominated by Larix mastersiana andAbies faxoniana. The results showed that: (1) The amount of annual return of K and Na in litter was 25.34 and 4.44 kg·hm^-2, respectively, with the order of different organs: foliar litter>twig litter>miscellaneous>bark litter>epiphytic litter>reproductive organ litter. Among them, foliar litter and twig litter accounted for more than 85% of the total return of K and Na. (2) The return dynamics of K and Na in total litter, foliar litter and twig litter presented “bimodal”patterns, with the maximum values in May and October. The dynamics of K and Na returns in bark litter and reproductive organ litter showed a “unimodal” pattern, with a maximum in May. (3) The K and Na in tree litters showed a “bimodal” return pattern, with the maximum values in May and October. The K and Na returns in shrub litters showed a “unimodal” pattern, with peaks in September to October. These results illustrate the seasonal characteristics of element return in different types of litters in typical coniferous forests in alpine areas, providing basic reference for further understanding regional forest material cycling and related ecological processes.

Key words: stress germination, wheat (Triticum aestivum), seed vigor, enzyme activity, gene expression.