Regeneration Characteristics Of Deciduous Broad-leaved Forest And Photosynthetic Eco-physiology Of The Endemic Species In Langyashan

The area of limestone covers one seventeenth of of the total land in China. In these area, soil layer is thin with high Ca content, and is serious shortage with the supply of effective water, which result in being difficult to recovery vegetation and serious soil erosion. As a result, the tree species selection and feasible regeneration model for the limestone area are most important topics to resolve. The area of limestone is up to 11.5% in the region of eastern Anhui, in which Platycladus orientalis and Quercus acutissima are the dominant trees, the area with large exposed rock is even in retrograde succession to secondary shrub. However, Ulmaceae is the dominant family in deciduous broad-leaved forest in Langyashan forest park. The broad-leaved forest dominated with Fagaceae, Ulmaceae and Aceraceae is the typical forest community in temperate zone of China. Langyashan is one of well-preserved area in warm-temperate broad-leaved forest zone. The study on population structure and regeneration characteristics is few, neither is photosynthetic eco-physiology of the endemic species in this typical forest.In this study, a typical deciduous broad-leaved forest in Langyashan was selected. The stand structure and regeneration characteristics were investigated. The results showed that a total of 8 tree species (DBH≥3.0 cm) which belonged to 5 families and 7 genus were recorded within 4 sampling plots. Aceraceae and Ulmaceae were the dominant families in this forest. The vertical structure of the forest was simple without obvious shrub and herb layers. In the arbor layer, Acer mono, Zelkova schneideriana and Platycarya strobilacea were the dominant tree species with absolute dominance. Tree species diversity was relatively low in this deciduous broad-leaved forest. The regenerated specis under the forest include seedlings and saplings of Acer mono Maxim, Pteroceltis tatarinowii Maxim, Zelkova schneideriana, Ulmus chenmoui Cheng. However, the seedlings of Koelrcuteria paniculata, Quercus acutissima and Platycarya strobilacea were hard to regenerate. Acer mono and Pteroceltis tatarnowii not only had a large number of regenerated seedlings and saplings, but also distributed widely, especially for Acer mono. The endemic species, Ulmus chenmoui with many regenerated saplings under the canopy only distributed at Nantianmen with high elevation.In order to indentify the effect of soil physico-chemical properties and soil seed bank on forest regeneration, regression analysis was conducted. The results showed that Pteroceltis tatarinowii regeneration was significantly and negatively correlated to organic concentration. The regeneration of Zelkova schneideriana was significantly related to the nitrate concentration. The Koelrcuteria paniculata regeneration was significantly and positively correlated to soil pH(H2O) and available N. The Ulmus chenmoui regeneration was significantly related to soil EC and elevation. Acer mono, Zelkova schneideriana, Platycarya strobilacea, Pteroceltis tatarinowii had a large soil seed bank. The seeds content of Acer mono, Zelkova schneideriana, Pteroceltis tatarinowii were almost consistent with regeneration status. Platycarya strobilacea had a large seed bank but hard to regenerate seedlings and saplings. Most tree species regeneration were influenced by soil seed bank except for Acer mono and Zelkova schneideriana.According to the comparison between typical broad-leaved forest and Quercus acutissima forest, we found that the main regeneration tree species were Acer mono, Pteroceltis tatarnowii, Zelkova schneideriana, Koelrcuteria paniculata, which were dominated by regeneration trees. The regeneration species were the same with the dominant tree species in the arbor layer, except Koelrcuteria paniculata. The regeneration species in Quercus acutissima forest were composed by Acer buergerianum, Quercus aliena, Celtis sinesis. Some of the Acer buergerianum and Quercus aliena had entered arbor layer with a certain competition. Quercus acutissima and Platycarya strobilacea were hard to regenerate in both forests, which could be closely related to light conditions, seed quality and quantity, soil properties.Through measurment by Li– 6400, the result showed that the diurnal changes of photosynthetic indexes for Ulmus gaussenii and Ulmus chenmoui had the same trend in the sammer and autumn. The curves of Pn,Gs,Tr had double peaks, while for Ci curve had a concave peak.