Comparative Study Of Seedling Community Composition And Distribution Patterns Under Different Sampling Intensity In 24 Ha Gutianshan Forest Dynamic Plot

A wide variety of resources and services is supported by forest community whicn holds the rcihest biodiversity on Earth to maintain the human survival and development. For a long time, biological diversity and mainteance mechanism of community forest has been the critical and core issues explored and researched by ecological and evolutionary biologist. The previous study of forest community have the feature of randomness and uncertainty. Based on the fact that a large plot of forest dynamic monitoring method has become one of the effective means of biodiversity research, it played an important role on the species coexistence, distribution pattern of diversity, ecology theory test and forest conservation and restoration. The species composition and diversity distribution pattern of forest communities in the past mainly focused on individuals of non seedlings whose DBH≥1 cm, however, resrch on the seedlings of forest community is less. As an important part of the forest community, the community can not only affect the formation of microenvironment of Under-forest seedlings, but also indirectly influence the structure and function of forest communities through regeneration and succession, which play a vital effect on the formation and maintenance of biological diversity. With the large-scale forest dynamics monitoring plots established, emphasis on understory seedlings has been increased. Currently, the establishment of a large number of 1 m × 1 m seedlings districts has promoted to make many important achievements. However, due to the strength of the sample is small, mainly related to common species, and the lack of effective monitoring of rare species, previous studies may not be able to fully reflect the composition and diversity of seedling species at community level distribution pattern.As the seedling stage is the bottleneck in forest tree regeneration, knowledge of the composition and structure of seedling communities are crucial to understanding the mechanisms of community assemblage and diversity maintenance. Here, we established a new seedling monitoring network in 24 ha Gutianshan (GTS) forest dynamic plot (FDP) which consisted of 285 seedling plots (5 m × 5 m) in 2012. In the seedling pots, all woody plants (DBH<1 cm and height≥10 cm) were tagged, mapped and measured every two years. In this paper, the first census data was used to investigate seedling composition, species diversity patterns, seedling and non-seedling species habitat association. Our results showed that:(1) There were 138 species,20,581 individuals in total in the 285 5 m × 5 m seedling plots. The Shannon-Weiner diversity index and rarefied species richness was higher than those of 1 m ×1m seedling community and 24 ha FDP census (DBH≥1 cm), The same results came from extracting 1000 individual samples of different seedling communities and different diameter woody plants using Rarefaction sampling principles; Compared to 1 m× 1 m seedling community, number of species showed a significant increase and species-area curve became more saturated; (2) The relationship between abundances of seedling and tree species exhibited a negative allometry (r=0.63; p<0.0001), which indicated that the mortality rate of plants in seedling stage was relatively high, and the survival rate was relatively low compared with the rate of non-seedling stage. (3) Sampling intensity and selection of DBH cutoffs could influence the definition of rare species. Some rare species defined by trees with DBH≥1 cm were not actually rare when we took individuals with DBH<1 cm into consideration (i.e. Ardisia crenata、Litsea cubeba、 Lespedeza thunbergii subsp. formosa); (4) The 5 m × 5 m seedling community had indicator species different from those of 24 ha FDP census and 1 m × 1 m seedling community. Only three and two shared indicator species were identified for 1 m × 1 m seedling and 24 ha FDP census data respectively. In conclusion, sampling intensity will influence the description of seedling composition and diversity patterns, and increasing sampling intensity can provide greater insights into the processes of diversity maintenance.By analyzing the composition and diversity distribution pattern of seedlings community and comparing the diffirences in the community composition, diversity distribution pattern and preference on the habitat between seedlings and non-seedlings, the study found that different sampling intensity has a significant influnce on the concrete results of diversity distribution pattern of seedings. Systematic monitoring understory seedlings via expanding seedlings plot can futher strengthen the acquaintance of maintenance mechanism of biological diversity. We initially realized the multiscale (time and space) dynamic inspecting all of the wooden plants in different life history stages from seeds,seedlings in different sampling intensity, through saplings and to trees by current seedlings community and the seed rain and litter monitoring developed in the plots,providing possibility for exploring the formation and maintenance mechanism of diversity in different life history stages, being of great significance to forest community construction and multifarious maintenance mechanism, and providing foundation for related theory testing and development of coexist and maintaining of forest species diversity.