DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 9-10/2022 str. 33     <-- 33 -->        PDF

regeneration of cypress. In this study, plant density of regenerated seedlings in 20 sample plots was 0 individuals / hm2, meaning no regeneration phenomenon. The reason for this phenomenon may be that these 20 plots are from the three sample survey areas where human activities were intensive. The frequent occurrence of concentrated human trampling incidents hindered the occurrence of seedlings. Morover, we revealed that NR through seed reproduction under appropriate environmental conditions could be achieved despite the rare NR of cypress plantation. The NR of cypress is closely related to the environment and stand factors. The suitable condition for NR of cypress is wet, high light intensity, soft soil, and low understory vegetation coverage.
We found that the number of Grade I, Grade II, Grade III, and Grade IV showed a decreasing trend, indicating that the number of young plant regeneration decreased with the increase of age; as well as implicating that the competition for regeneration plants from a young age to old age was fierce with high mortality. Competition becomes increasingly fierce when the supply of resources such as light and space cannot meet the needs of individual growth of the population. Thus, as young cypress individuals grow, the external environment requires that cypress seedlings be more resistant and adaptable to survive. As a result, the upper height level seedlings cannot stably enter the next stage, leading to a decline in the number of renewal seedlings.
The influence mechanism of herb coverage effect on cypress regeneration – Utjecaj mehanizma pokrovnosti bilja na prirodnu obnovu obične azijske tuje
This study found that there was a significant negative correlation between understory herb density and the number of cypress seedlings (Table 3; Figure 4), which was similar to the previous research results (Dyderski et al. 2018). The reason may be that cypress regeneration seedlings need nutrients and light during growth and development, which will produce fierce competition with herbs (Colmanetti et al. 2021). A competitive relationship between herbs and seedlings is driven by two reasons: They compete for photosynthetic nutrient space on the ground and nutrient and water resources underground; Herbaceous plants influence the behavior of herbivores and attract them to the area where the cypress is also located, increasing the risk destruction (Duclos et al. 2013). So, the regeneration of cypress seedlings will be suppressed due to the continuous increase of herb density (Montti et al. 2011). Therefore, for the investigated forest, the goal of promoting NR of cypress can be achieved by moderately thinning understory plants.
The influence mechanism of moss coverage effect on cypress regeneration – Utjecaj mehanizma pokrovnosti mahovinom na prirodnu obnovu obične azijske tuje
The number of cypress seedlings increased with increasing moss coverage (Table 3; Figure 4), suggesting that the density of cypress seedlings and moss coverage are beneficial to grow of each other. Mosses grow basically close to the ground and their high coverage rates contribute to improving soil moisture and reducing soil surface temperature. Studies reported that mossy mulch is associated with high mortality of small seed herbaceous plants (Fukasawa et al. 2019), which may be reduced the herbaceous plants competing for nutrients with cypress seedlings. Thus, a high moss coverage rate is conducive to cypress regeneration. On the one hand, different stand densities cause the heterogeneity of light and heat conditions in the forest, which impacted the growth and development of understory moss. On the other hand, the strong water and soil retention abilities of mosses provide a moist soil surface microclimate and inhibit herbaceous plant growth (Mallik and Kayes 2018). Last but not least, most of the water source needed by bryophytes is derived from atmosphere, thereby bryophytes do not compete with cypress regeneration seedlings for a large amount of water in the soil. Moreover, cypress is a sun-loving tree species but tolerates slightly shade rather than drought when young. To some extent, the growth habit of cypress in young stage resembles that of mosses. Therefore, for this study, the moss layer can not only provide a relatively humid growth environment for cypress seedlings and young trees but also act as a protective pad (Fukasawa,et al. 2018) . Conclusively, the higher moss coverage, the more suitable for NR of cypress.
The influence mechanism of soil stone content effect on cypress regeneration – Utjecaj mehanizma kamenitosti tla na prirodnu obnovu obične azijske tuje
In the present study, the number of cypress regeneration seedlings showed an upward trend with the increase of soil stone content. We speculated that increasing soil gravel content maybe elevate soil porosity thereby the roots of cypress seedlings are easier to take root. The soil with different stone content creates a completely different space for the root system of cypress seedlings from the pure soil, in which the factors have changed, such as water, fertility, gas, and temperature. In such an environment, cypress roots could actively regulate the accumulation of biomass by adjusting the physical distribution and changing the root metabolic rate, thus, the purpose of improving the growth level of cypress seedlings was achieved.