Seedling Establishment And Ecological Adaptation Mechanism On Teminalia Franchetii And Quercus Franchetii In Jinshajiang Dry-hot Valley, Southwest China

Dry-hot valleys of Jinsha River are typical ecological fragile areas in southwest of China. There are poor natural conditions and seriously vegetation degradation in these areas. Communities of Teminalia franchetii and Quercus franchetii are two very important natural vegetation types in Yuanmou county segment of Jinshajiang dry-hot valley. In the context of sustained or even strengthened human disturbance, there is great significance for cultivation and management of natural vegetation and ecological restoration in the region, which study seedling establishment of the community and its response mechanism to environmental factors. In this study, field sample investigation, follow-up observation and indoor control experiments were employed, community characteristics, flowering biological characteristics, seed biology and germination characteristics, soil seed band and seedling dynamics and the main impact factors of seedling early growth about T. franchetii were systematically studied. At the same time, we researched community characteristics, seed biology and germination characteristics, and characteristics of seedling early growth response of the main environmental factors about Q. franchetii. The suitable environmental conditions for seed germination and seedling early growth of T. franchetii and Q. franchetii were clearly determined, and seedling establishment mechanism and its ecological adaptation to environments of them were analyzed. Research results are as follows.Ⅰ. There are extremely simple species composition in both T. franchetii and Q. franchetii remaining communities of Yuanmou dry-hot valley.32 kinds of plants were found in the former, which belong to 16 families and 28 genera, and 68 kinds of plants were found in the latter, which belong to 35 families and 60 genera. Species diversity of two kinds of communities was relatively low, and the main species of them belong to Poaceae, Papilionaceae and Labiatae families.Ⅱ. When T. franchetii flowers open, their stigmas spread and enlarge first, then stamens begin expand. Single flowers of T. franchetii approximately have 10-15 days flowering period, which shows the period from the stigma spreading out of buds to anthers fading. There may be wind pollination and insect pollionation of two forms in T. franchetii, and its breeding system was dominated by outcrossing, part of them was self-compatible, requiring pollinators, and flowers in the same inflorescence or different inflorescence can pollinate each other. However, different inflorescence pollinated seed yield was significantly higher than the same inflorescence pollination.Ⅲ. Both T. franchetii and Q. franchetii seeds germination are extremely sensitive to water conditions, and their germination process to some extent was limited by the moisture conditions. At the same time, there is the best germination for T. franchetii seeds at room temperature (25℃) and 20-30℃day-and-night changed temperature, and its germination was strongly inhabited at 15℃temperature. There is the best germination for Q. franchetii seeds at 20-30℃day-and-night changed temperature, and its germination to some extent was limited at 35℃.2 kinds of plant seeds have no dormancy; they may germinate in the suitable conditions when they fall to the ground. Storage (less than 1 year) is conducive to T. franchetii seeds germination, is not conducive to Q. franchetii seeds germination. Exposure in the sun can cause Q. franchetii seeds germination rate decreased significantly.Ⅳ. T. franchetii seed banks include canopy seed bank and soil seed bank of two kinds of forms. Retention time of seeds in the canopy was more than 1 year, and there may be a positive correlation between seed shedding and wind power, and there may be a negative correlation between seed shedding and rainfall and relative humidity of the air. T. franchetii seeds spread mainly by wind power, and the distance of seed dispersal were very far (more than 11.5 m).Ⅴ. T. franchetii seedling regeneration occurred in the rainy season, there is no seedling regeneration in the dry season. Seedlings can survive the period just after germination is the key to forest seedlings successfully regeneration. In communities, distribution of the natural regeneration seedlings has obviously aggregation characteristics. The seedlings are more concentrated under Dodonaea viscosa shrubs or near the basal of T. franchetii adult plants and other good environments.Ⅵ. Water conditions have a significant impact on plant morphologic characteristics, leaf characteristics and biomass allocation during early growth of both T. franchetii and Q. franchetii seedlings. Two kinds of seedlings showed some ability to adapt water stress, but T. franchetii seedlings showed a relatively narrow range of water condition than Q. franchetii seedlings. And Q. franchetii seedlings can survive or grow simultaneously in a very dry and more humid environment, and has a strong ecological adaptability.Ⅶ. Competition of Heteropogon contortus has a significant impact on the early growth process of T. franchetii seedlings. Seedling germination time and the number of surrounding H. contortus populations play an extremely important role in T. franchetii seedlings survive and growth. When T. franchetii seedling establish before H. contortus or there are small number of H. contortus populations, T. franchetii seedling have great survival advantage. Habitat heterogeneity is one of important factors which affect Q. franchetii seedlings successful establishment in communities, and low land covered by litter (LLCL) and flat ground covered by litter (FGCL) were better micro-habitats for Q. franchetii seedlings growth.Relatively more seedlings can be found in both T. franchetii community and Q. franchetii community in Yuanmou dry-hot valley, but saplings are rare. Seedlings can get through the period after seed just germination is the key to forest seedlings successfully regeneration. Therefore, it is useful for early growth of forest seedling to strengthen the conservation of plant diversity within the community, and make it a good environment. At the same time, in the artificial cultivation and management and vegetation restoration, it is very important to create a catchment, water retention environmental conditions for the early growth of seedling, such as litter or film cover habitas and deep dig ponds to breed.