The Ecophysiological And Productivity Of Cinnamomum Camphora

Camphor tree (Cinnamomum camphora (L.) presl) is national peculiar species for timber and economy. As one of the most important components of the evergreen species in subtropical zone. Camphor trees play a important role on maintaining the structure, functions and biodiversity in subtropical evergreen broad leaf forest. The prominent conifer plantation trees and the singular structure make the forest ecosystem susceptible to area environment safety. As a result, it is urgent and necessary to plant great area ecological forest to improve the ecological environment. In this thesis, many aspects, including photosynthesis, transpiration and little climate characteristics, biological productivity, area biological net primary productivity (NPP) and growing potential evaluation, were studied in the camphor tree plantation forest, by adopting the Li-6400P portable photosynthesis system and ZENO-2000TE trunk transpiration measurement system, combining the outdoors field research with indoors analysis. The results are following:There is a significant midday depression in the daily changes of net photosynthetic rate (Pn)In growing periods the maximum of Pn is up to 18.370 M molCOa-m-2-s-1. and the minimum is1.5 n molCO2-m-2-s-1. .The daily change of Pn of the upper leaves and the middle leaves varies with double peak curves , which appears at 10:00 and 14:00, respectively, Pn of the below leaves increase rapidly from 8:00 a.m. to 12:00 and maintains for some time about from 12:00 to 16:00, about 3 u molCO2-m-2-s-1.. The peak appears at 16:00, the average Pn is 2.583 u molCO2-m-2-s-1 corresponding to 54.54% and 87.99% of the upper and middle leaves, respectively. When it is cloudy, Pn appears single peak in a day, and the peak appears at 12:00 all so, but in different seasons, it is a double peak curve, the climax appear in June and September. The difference is apparent for the different layers leaf. The light saturation point (LSP) of upper leaves is 1200 ?0 P mol- m-2-s-1,; middle leaves is 800 ?50 u mol-m-2-s-1, beneath leaves is 700 ?50 n mol- m-2-s-1 .And light compensation point (LCP) is 50 P mol-m-2-s-1 . The CO2 saturation point of upper leaves is l000p mol-mol-1; middle leaves is l000u mol-mol-1, below leaves is 1400 U mol-mol-1; Respectively, the C0₂ compensation point of all leaves is about 50 n mol-mol-1 Many biological and ecological factors take account for the net photosynthesis, such as Cond, Ci, Vpdl, Tair, Tleaf, RHS and PARi. Although the increasing CO₂concentration doesn't affect the stoma itself, it restrains the Pn. The increasing of light intensity influences the photosynthetic characteristics of the middle and beneath leaves in arbor layer, on the contrary ,which the Pn decline when the light intensity exceeds the light saturation point.The daily change of leaf transpiration rate of camphor is summarized as the single peak curve, the peak appears in different time and different condition, the peak appears at 14:00 apparently in93May and July, the leaves upper and middle change violently, and the below change gradually. In September, the transpiration rate shows a stable period from 10:00 to 14:00 .The maximum of leaf transpiration rate is 6.72mmol m-2s-1 .There are difference about the leaf transpiration rate in vertical patters .The order of leaf mean daily transpiration rate is: upper leaves >middle leaves>below leaves in May and September, and in July is middle leaves > upper leaves>below leaves; At the individual level , the daily change of transpiration rate shows single peak curve, which the peak appears at 14:00 when it is sunny and cloudy ,the rainy day occurs at 16:00.The minimum of transpiration rate appears at 6:OOA.M .The order of mean daily transpiration rate is: sunny >cloudy>rainy. In different phonological phase, the order is: juvenile period> senescent period>shift period. The leaf transpiration rate was summarized as single peak curve, which is high in June and the mean value of upper, middle and below leaf is 3.72, 2.31, 2.93mmol-m-2-s-1. The m...