Photosynthetic Traits And Resource Allocation Characteristics Of Common Species Seedlings In Tiantong National Forest Park

The Tiantong National Forest Park in Zhejiang is one of rare representative areas of subtropical evergreen broad-leaved forest region-specific vegetation type in eastern China. In Recent years, with the intensification of human activities, people pay more attention to vegetation degradation and restoration problems. Seedling regeneration is a most important step of forest community succession, vegetation restoration and other processes. This article is mainly from seedling photosynthetic traits and resource allocation characteristics point of view, focusing on the seedling's photosynthetic traits, biomass allocation, nutrient supply and non-structural carbohydrate storage characteristics, investigating of the adaptability between photosynthate and distribution, to know different species seedlings' survival strategy.(1) Using LI-6400 portable photosynthesis analyzer,20 common species seedlings in Tiantong were measured light response curves to compare the different life forms plants'photosynthetic characteristics. We found that seedlings of evergreen species have lower light compensation point (LCP), dark respiration rate (Rd) but higher apparent quantum efficiency (AQE), maximum net photosynthetic rate (Amax). Deciduous species show the opposite results.It means that evergreen species have more efficient light energy conversion and assimilation, better use capability of low light. The light saturation point (LSP) and maximum net photosynthetic rate (Amax) of evergreen shrub species are higher than those of evergreen tree species, but other photosynthetic parameters have no significantly difference. It means evergreen shrub have not only lower light use capability, but also higher net production.(2) The individual level of biomass allocation patterns,affecting the functional properties of plants,is the results of plants adaptation and evolution with the environment. This study,we selected 20 common species seedlings biomass allocation models analysis,shows that evergreen species will build more biomass on leaf to adapt the low light environment under forest,while deciduous species increases stem biomass investment,faster growth to get more light. Evergreen shrub takes more biomass to expand leaf area and root construction. It can adapt to low light quantum environment in forest, providing adequate nutrients for the growth and building more non-structural carbohydrate storage sites.(3) In plant evolution,in order to adapt to different growing environments, different species, different plant life forms or even different organs of plants formed their own different nutrient characteristics. Seedling leaf is the highest organ of N and P contents; leaf N, leaf P and stem N contents of deciduous species seedling are higher than those of evergreen species. N, P contents in evergreen shrub leaf and stem are higher than those in evergreen trees. N, P elements contents in different organs show significantly positive correlation, indicating the differences elements can promote other's absorption.(4) Root is the key place of Non-structural carbohydrate storage. In order to surviving in low light environment under forest,evergreen species seedling's sugar, starch and non-structural carbohydrate (NSC) contents in root and sugar content in stem were higher than those of deciduous species. Evergreen shrub with the small individual, due to the long life in shaded environment and vulnerable to outside interference and damage, the root sugar, NSC contents and stem starch, NSC contents were all significantly higher than evergreen tree. It is a survival adaptation.(5) The status of species in community largely depends on its trade-off between growth and survival. Seedling photosynthesis traits and resource allocation characteristics match to its living environment. Light-demanding species or pioneer-species represent "fast-growth, high-nutrients, low-storage" strategy. Strong shade-tolerant evergreen shrub represent "slow-growth, low-nutrients, high-storage" strategy. Photosynthetic capacity and carbohydrate storage of the Semi-shade evergreen tree or Iaccio wood species are medium.