Assessing Establishment Success And Suitability Analysis Of Four Zostera Marina Seed Planting Technologies

Seed planting method for restoration is an important way to recover seagrass bed. In this study, we investigated four Zostera marina seed planting technologies in Swan Lake on the eastern coast of Shandong Peninsula, China. Establishment success of seed planting was assessed and suitable seed planting factors were explored. The economic cost of the four technologies were also analyzed comparatively. Finally we comprehensively summarized the eelgrass recovery mode by using seedlings and reasonable seed planting process for restoraion was proposed. The findings of the research not only provide information, basic theory and support for large-scale restoration of seagrass beds, but also give references and examples for relevant research on other seagrass species. The main results are summarized as follows.1. We conducted the experiment by using the burlap bags method in Swan Lake. Seed planting effect was assessed and the effects under different seeding densities (200.300.400 and 500 seeds/Unit) were explored by monitoring seed germination rates, seedling establishment rates, and shoots growth. The results showed that the average seed germination rate and seedling establishment rate was 38.0% and 20.9% respectively. Eelgrass patches were established, and the average density was up to 495 shoots m-2. The shoot density of 657 shoots m-2 under 400 seeds/Unit was significantly higher than those under other treatments, so it may be the suitable seed planting density. This study provides a supporting technology for significantly improving the seed utilization rate of Z. marina.2. We conducted the experiments with seeds protected in gauze bags based on the seeds viability against high labor intensity and complex operation. Firstly, the experiment in laboratory was carried out to determine whether bags affect seed viability and then we verified the seed planting effects in the field. The results showed that gauze bag had no obvious effect on seeds viability, so it is a suitable material for seed planting. Seed germination rate (up to 65.7%). seedling establishment rate (20.8%) and the highest shoot density (350 shoots m-2) were found in the first year after planting, suggesting a good recovery.3. The clay model method based on the seeds viability was created to speed up the growing mechanization of seed planting technology for large-scale restoration. We studied the placing time and planting depth of seed planting units in laboratory, and verified the seed planting effects in the field. The results suggested the best placing time to seed planting unit was 2 days under laboratory conditions. It was a suitable way that the seed planting unit was embedded in the bottom surface (1.5 cm depth). In the field experiment, the seedling establishment rate of the treatments of seed planting unit buried in the sediment and embedded in the bottom surface were up to 27.5% and 32.6% respectively, and the highest shoot density in one year after planting were 377 shoots m-2 and 357 shoots m-2. There was no significant difference in the recovery effects between two planting patterns, but the operation of the pattern seed planting unit embedded in the bottom surface was simple, so it should be a suitable pattern for seed planting. The findings lay the theoretical foundation for the realization of mechanization planting.4. In order to break the restrictions of clumped seed planting pattern on plant propagation and restoration area expansion, we developed a planting pattern of cultivating seedlings in the field, the seedling bed method. We investigated the planting effects affected by the factors of seeds vernalized at 4℃ before planting, seed planting density and the number of the holes on the flowerpot lateral wall by monitoring the seed germination, seedling establishment and shoot growth. We found that vernalization (stored at 4℃), the density of 27 seeds PU-1 and 7 holes on the flowerpot lateral wall could enhance seed germination rate and the seedling establishment rate was highest (up to 16.7%), so they are the suitable factors for seeding cultivation. The average shoot density was 13.0 shoots PU-1 in one year after planting and was up to 47.0 shoots PU-1 in two year after planting, which suggested a good effect on seedling cultivation; and the shoot morphological parameters of the 7 holes on the flowerpot lateral treatment wall were significantly higher than that of the 4 holes on the flowerpot lateral treatment, which suggested increasing the exchange of dissolved oxygen in interstitial water could help seedling establishment and shoots growth. The results provide the technical foundation for creating a way of "seedling cultivation-ramet transplantation"5. We comparatively analyzed the planting effects of four methods and found that their seedling establishment rates ranged from 14.8% to 32.6%, which were significantly higher than those reported. These results improved the seed utilization rate. Their shoot densities in the first year after planting were up to 350-655 shoots m’2, suggesting a good restoration. Economic cost accounting showed the investments of four methods ranged from 6068 to 10120 Yuan/Mu, and the investment of cultivating seedlings in the field was lowest. According to the progress in domestic and foreign research and the main conclusions in this study, we summarized the eelgrass recovery mode by using seedlings, established the process of seed planting for eelgrass, and suggested the research prospect.