Effect Of Harvesting And Light On Modular Population Of Taxus Yunnanensis

Taxus yunnanensis is an endangered and rare plant species, it is one of the first nationallyprotected plants of our country. Taxus yunnanensis is rich in taxol, it has a broad developmentprospects. So far, artificial cultivation of taxus forest is the most feasible way of obtaining taxol.For this purpose, many regions in the southwest China have carried out large-scale constructionof taxol raw material forest, Taxus yunnanensis is one of the main planting species.It’s not easy to construct Taxus yunnanensis raw material forest base, now the problem weneed to solve is to design and perfect the way of managing and mainteining Taxus yunnanensisplantation. Design reasonable managerial actions especially harvesting methods could bringtechnical support for the sustainable output of Taxus yunnanensis raw material forest andprovide theoretical basis for their conservation. Considering the lack of scientific harvestingtechniques, our paper used4different harvesting methods, every methods had3levels. Wesurveyed the amount and dynamics of branches, leaves, buds of these harvested Taxusyunnanensis for1year. Besides, the modular population affected by light enviroment wasinvestigated. Our purpose is to explore the effect of harvesting on the modular population ofTaxus yunnanensis and summarize the best harvesting methods of Taxus yunnanensis rawmaterial forest. Our ultimate aim was managing Taxus yunnanensis raw material forestrationally, and maximizing the economic benefit of Taxus yunnanensis raw material forest. Themain results of this thesis are as follows:1. Effect of harvesting on branch modular population of Taxus yunnanensis: Lowharvesting intensity could inhibite the amount of spring branch growed in one branch, onebranch could grow more spring branches with the increase of harvesting intensity; havestingcould increase the amount of antumn branches growed in one branch. High harvesting intensitycould promote more branches spouting spring branch and autumn branch, simultaneously, thelength of spring branch and autumn branch would be promoted. The addition of spring branch length became larger with the increase of harvesting intensity, this tendency didn’t havesignificant relation with whether retain trunk. Autumn branch length was close related towhether retain trunk, it was negatively correlated with harvesting intensity if retain trunk, andpositively correlated with harvesting intensity when cut trunk; harvesting could raise theamount and length of new branch, promoting effect went obviously with the increase ofharvesting intensity.2. Effect of harvesting on leaf modular population of Taxus yunnanensis: Harvesting couldinfluence the defoliation dynamics of old branches of Taxus yunnanensis; Harvesting couldincrease sping leaf numbers of Taxus yunnanensis, but it lowered sping leaf density, the higherthe harvesting intensity, the lower the spring leaf density; harvesting could increase autumnleaf numbers of Taxus yunnanensis, meanwhile increase their density; Harvesting played apromoting effect in new leaf amount, an inhibitory action in new leaf density, the harvestingmethod which had the biggest promoting effect was retaining trunk and harvesting3/4branches and leaves, its leaf amouts was81.3%more than the control. Harvesting had nosignificant effect on new leaf density, the difference of all harvesting methods didn’t reachsignificant level.3. Effect of harvesting on bud modular population of Taxus yunnanensis: Harvesting couldincrease sping bud numbers of Taxus yunnanensis as well as increase sping bud density,promoting effect was significantly correlated with harvesting intensity, cutting trunk andharvesting1/4,2/4,3/4branches and leaves were1.21,1.38,1.64times of the control,retaining trunk and harvesting1/4,2/4,3/4branches and leaves were1.21,1.44,1.51times ofthe control; Most harvesting ways could enhance autumn bud amount and autumn bud density;Harvesting branches and leaves favoured the increase of new bud amount and density.4. The choice of the optimum harvesting method: During these harvesting methodsdesigned in this paper, the growth and development trend of branches, leaves, buds populationof4methods’ are most obvious, they were cutting the trunk and harvesting2/4and3/4branches and leaves of crown length, retaining trunk and harvesting2/4and3/4branches and leaves of crown length, the differences of modular population dynamics of these4harvestingmethods weren’t significant. In order to get more branches and leaves, two methods whichharvested2/4branches and leaves of crown length were eliminated. Simultaneously, if thetrunk were harvested, the population and density of branches, leaves and buds were a littlehigher than those whose trunks were retained, meanwhile, they had more sprouts, sprouts playsa very important role in the natural regeneration of plants. To sum up, cutting the trunk andharvesting3/4branches and leaves of crown length is the best harvesting methods in this paper.5. Effect of light on architectural model and leaf water feature of Taxus yunnanensis: Thearchitectural of Taxus yunnanensis model was modified plastically in response to different lightconditions, the leaf water feature also has some differences. Taxus yunnanensis had greatstature and wide crown in theses areas where had sufficient light, the crown fullness ratio was0.97, almost double of those under canopy. The average overall bifurcation ratio in full lightenvironment is8.57, it was significantly bigger than6.40of gap and4.81of under canopy,some other architectural parameters such as length of the first order branch, branch angle andleaf angle have the same trend. The leaves displayed significant differently in various lightenvironment, the leaf number of branch in full light was2.77times of gap and6.88times ofunder canopy, but all of them have the biggest amount of leaves distributed at the first-orderbranches. The water saturation deficit increased with the continuous weakening of lightintensity, while tissue density, relative water content and ratio of dry weight to fresh weightreduced with the tapering off of light. It indicated that the leaves’s ability of combating drought,retaining water and resisting water stress increased with the increasing of the intensity of thelight. These indicated that Taxus yunnanesis made some necessary changes in morphologicaland physiological aspects in order to accommodate themselves to the change of lightenvironment.